Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2013 Article ID 570587 9 pageshttpdxdoiorg1011552013570587

Research ArticleSolar Photocatalytic Degradation of Bisphenol Aon Immobilized ZnO or TiO2

Andreas Zacharakis1 Efthalia Chatzisymeon1 Vassilios Binas2 Zacharias Frontistis1

Danae Venieri1 and Dionissios Mantzavinos13

1 Department of Environmental Engineering Technical University of Crete Polytechneioupolis 73100 Chania Greece2 Institute of Electronic Structure and Laser (IESL) FORTH PO Box 1527 Vassilika Vouton 71110 Heraklion Greece3 Department of Chemical Engineering University of Patras Caratheodory 1 University Campus 26504 Patras Greece

Correspondence should be addressed to Dionissios Mantzavinos mantzavinoschemengupatrasgr

Received 30 May 2013 Accepted 14 July 2013

Academic Editor Christos Trapalis

Copyright copy 2013 Andreas Zacharakis et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The removal of bisphenolA (BPA) under simulated solar irradiation and in the presence of either TiO2orZnOcatalysts immobilized

onto glass plates was investigated The effect of various operating conditions on degradation was assessed including the amount ofthe immobilized catalyst (361ndash1507mgcm2 for TiO

2and 05ndash68mgcm2 for ZnO) initial BPA concentration (50ndash200 120583gL)

treatment time (up to 90min) water matrix (wastewater drinking water and pure water) the addition of H2O2(25ndash100mgL)

and the presence of other endocrine disruptors in the reaction mixture Specifically it was observed that increasing the amountof immobilized catalyst increases BPA conversion and so does the addition of H

2O2up to 100mgL Moreover BPA degradation

follows first-order reaction kinetics indicating that the final removal is not practically affected by the initial BPA concentrationDegradation in wastewater is slower than that in pure water up to five times implying the scavenging behavior of effluentrsquosconstituents against hydroxyl radicals Finally the presence of other endocrine disruptors such as 17120572-ethynylestradiol spiked inthe reactionmixture at low concentrations usually found in environmental samples (ie 100120583gL) neither affects BPA degradationnor alters its kinetics to a considerable extent

1 Introduction

Endocrine disrupting compounds (EDCs) constitute animportant class of emerging environmental contaminantswhich pose an increasing threat to aquatic organisms as wellas to human health [1] In particular the exposure to EDCshas been linked with altering functions of the endocrine sys-tem inmale fish such as vitellogenin induction and feminizedreproductive organs [2] Moreover the increasing incidenceof cancer and the hypothesis of a decreasing reproductivefitness of men are thought to be attributed to endocrinedisruptors Among various EDCs bisphenol A (BPA) is well-known for its interference with the endocrine system of livingbeings [3 4] BPA is widely used in the manufacturing ofnumerous chemical products such asCDsDVDs drink con-tainers electrical and electronic equipment and protective

coatings [1 5] These substances enter municipal wastewatertreatment plants (WWTPs) through either human excretionor their direct disposal in the sewage system Currently whenEDCs enter conventional biological WWTP only a smallamount of these chemicals are removed via biodegradationprocesses becausemost of themare xenobiotics and thus non-biodegradable [6] Therefore the majority of EDCs remainsoluble in the effluent and they are discharged to aquaticbodies In the last decade several studies have confirmed theoccurrence of EDCs at the level of ngLndash120583gL in inlandwaters(rivers and streams) and wastewaters (outlets of municipaland industrial WWTPs) worldwide [7ndash11] Not only this butit has been found that these compounds can pose a potentialdanger to fish and other aquatic organisms even at lowconcentrations of 01ndash10 ngL [12] Thus it is necessary tolook further on the removalmechanisms in order to improve

2 International Journal of Photoenergy

the efficiency of the existing treatment systems and to developnew and reliable treatment strategies to remove EDCs fromwastewaters

Semiconductor photocatalysis using solar radiation asthe source of photons for the activation of the catalyst hasreceived considerable attention over the past several yearsSeveral heterogeneous photocatalysts have been investigatedand amongst them the use of TiO

2under ultraviolet andor

visible light has extensively been researched Another photo-catalyst that absorbs over a large fraction of the solar spec-trum is ZnO with a gap energy of 32 eV The photocatalyticmechanism of ZnO is similar to that of TiO

2[13] Moreover

solar photocatalysis is considered as a cost-effective andsustainable treatment technique due to the utilization of solarenergy (an abundant source of energy) However the biggestproblem with slurry photocatalysis has been recognizedto be the need for a posttreatment recovery step [14 15]Therefore research has been conducted to produce catalystson supports that would keep the catalyst powder out of thetreated water and sufficiently reduce even more the cost ofthe photocatalytic process since there will be no need forcatalyst aftertreatment So far few studies have dealt withthe treatment of EDCs by means of TiO

2or ZnO catalysts

immobilized onto supports such as glass [4 16] PTFE meshsheets [17] titanium substrates [18 19] and polyurethanefoam cubes [20]

Hence in this work the efficacy of solar photocatalyticprocess to remove BPA from aqueous environmental sampleswas investigated For this purpose two different photocat-alytic materials namely ZnO and TiO

2 were immobilized

onto appropriate glass substrate by means of a heat attach-ment technique The effect of various operating parameterssuch as the immobilized catalyst amount the initial BPA con-centration the treatment time the water matrix the additionof H2O2 and the presence of other organic substances on

process efficiency was investigated

2 Materials and Methods

21 Materials BPA and 17120572-ethynylestradiol (EE2) werepurchased from Sigma-Aldrich while ZnO (ge99 particlesize lt 100 nm 15ndash25m2g BET surface area) and TiO

2-

P25 (anatase rutile 75 25 21 nm primary crystallite particlesize 50m2g BET surface area) were purchased from Flukaand Degussa-Evonik Corp respectively The water matrixwas either of the following three (i) wastewater (WW)collected from the outlet of the secondary treatment ofthe municipal WWTP of Chania W Crete Greece (ii)commercially available bottled water which will be referredto in the text as drinkingwater (DW) and (iii) ultrapurewater(UPW) at pH = 61 taken from a water purification sys-tem (EASYpureRF-BarnsteadThermolyne USA) The mainproperties of WW and DW are given in Table 1

22 Catalyst Preparation The ZnO or TiO2catalyst powders

were immobilized on glass plates (15 cm times 15 cm) by aheat attachment method Analytically the glass plates werefirst treated with a 38 HF solution and then washed with

Table 1 Properties of wastewater and drinking water matrices usedin this study

Parameter Wastewater Drinking waterpH 8 77TOC (mgL) 78 03COD (mgL) 24 NDConductivity (120583scm) 820 329HCO

3

minus (mgL) 190 188Clminus (mgL) 220 lt5NO2

minus (mgL) 57 lt009NO3

minus (mgL) 26 lt5ND not determined

001MNaOH in order to increase the number of OH groupsand achieve better contact of the catalyst on glass plates[14] Moreover a suspension of 8 gL catalyst in distilledwater was preparedThis suspension was sonicated at 80 kHzfor 120min in order to improve the dispersion of the solidcatalyst in water Afterwards the sonicated catalyst solutionwas poured on the glass plates at various volumes rangingfrom some 120583L to about 10mL and then placed in an oven at120∘C for 60min After drying the glass plates were calcinedat 500∘C for 180min Finally the glass plates were washedwith distilled water to remove the loosely attached catalyticparticles

23 Catalyst Characterization Techniques The crystal struc-ture particle size and morphology were examined with apowder X-ray diffraction (XRD) system and scanning elec-tron microscopy (SEM) respectively XRD patterns werecollected on a Rigaku DMAX-2000H rotating anode dif-fractometer (Cuk120572 radiation) equipped with a secondarypyrolytic graphite monochromator operating at 40 kV and80mA over the 2120579 collection range of 10ndash80∘ The scan ratewas 005min with a step size of 001 Surface morphologyof the catalytic plates was carried out on a JEOL JSM-6400VSEM instrument

24 Photocatalytic Experiments Photocatalytic experimentswere performed using a solar simulator (Newport model96000) equipped with a 150W xenon ozone-free lamp andan Air Mass 15 Global Filter (Newport model 81094)simulating solar radiation reaching the surface of the earthat a zenith angle of 482∘

The incident radiation intensity on the photochemicalreactor in the UV region of the electromagnetic spectrumwas measured actinometrically using 2-nitrobenzaldehyde(purchased from Sigma-Aldrich) as the chemical actinometer[21] and it was found to be 165 10minus5 einsteinm2 In a typicalphotocatalytic run 64mL of the water matrix spiked withthe appropriate amount of the organic substance was fed ina cylindrical pyrex cell and the ZnO or TiO

2catalytic plate

was added while the cell was open to the atmosphere Thesolar simulator was placed on top of the liquid surface whilethe catalytic glass plate was held by a Ti support dipped into

International Journal of Photoenergy 3

Inte

nsity

(au

)

A

A A

R

A

10 20 30 40 50 60 70 802120579 Cuk120572

Figure 1 XRD pattern of the TiO2immobilized particles on glass

plate (A anatase R rutile)

the reactionmixture Samples of about 1mLwere periodicallytaken from the cell and analyzed as follows

25 Analytical Techniques High-performance liquid chro-matography (Alliance 2690 Waters) was employed to mon-itor the concentrations of BPA and EE2 Separation wasachieved on a Luna C-18(2) column (5120583m 250mm times46mm) and a security guard column (4mm times 3mm) bothpurchased from Phenomenex The mobile phase consistsof 35 65 UPW acetonitrile eluted isocratically at 1mLminand 30∘C while the injection volume was 100120583L Detectionwas achieved through a fluorescence detector (Waters 474)in which the excitation wavelength was 280 nm and theemission wavelength was 305 nm Under these conditionsthe retention time for BPA was 43min the limit of detectionwas 068120583gL and the limit of quantitation was 232 120583gLthe respective values for EE2 were 51min 063 120583gL and211 120583gL Residual H

2O2concentration was monitored using

Merck peroxide test strips in the range 0ndash100mgL Changesin effluent pH during photocatalytic treatment were checkedusing a Toledo 225 pH meter

3 Results and Discussion

31 TiO2Catalyst Plates Figure 1 shows XRD pattern of the

TiO2immobilized particles on glass plate subjected to heat

treatment at 500∘C for 3 h Peaks at 2120579 values of 25∘ and27∘ correspond to the anatase (101) and rutile (110) planesrespectively The crystalline size (119863) was calculated at 17 nmusing the Scherrer equation

119863 =119896120582

120573 cos 120579 (1)

where 119896 is a constant equal to 09 120582 is the wavelength ofcharacteristics X-ray applied (015418 nm) 120573 is the full widthat half maximum of the anatase (101) peak obtained by XRDand 120579 is the Bragg angle

The phase content of TiO2particles can be calculated as

follows

119891119860=

1

1 + 119868119877079119868

119860

(2)

where 119891119860is the content of anatase and 119868

119860and 119868119877are the

integrated intensities of the anatase (101) and rutile (110)peaks respectively The TiO

2catalytic plate mainly consists

of the anatase phase with mirror rutile phase (70 30)Figure 2 shows SEM images of the immobilized catalytic

particles on glass plates with different amounts of TiO2in the

range 813ndash3392mg (361ndash1507mgcm2) The TiO2layer is

homogeneouswith a porous surface while themorphology ofTiO2particles is amorphous As the amount of TiO

2increases

the homogeneity increases and so does the film thickness inthe range 2ndash6120583m

The effect of increasing the amount of immobilized TiO2

on BPA removal is shown in Figure 3 the 90min conversionincreases from 60 to 80 as TiO

2increases from 361 to

1507mgcm2 and this is expected sincemore catalyst surfacesites are available for reaction at higher catalyst loadingsAn additional run was performed in the absence of catalystyielding only 15photolytic removal after 90min Since TiO

2

in slurry has extensively been used for photocatalytic pur-poses an extra runwas carried out to compare the efficienciesof slurry and immobilized catalysts Hence 065mg TiO

2

powder was added to the reaction mixture and completeremoval of 100 120583gL BPA could be achieved after 35min ofreaction (data not shown) This shows that slurry catalystseven at extremely low concentrations yield higher reactionrates than the immobilized systems presumably due to lowermass transfer limitations

32 ZnO Catalyst Plates Figure 4 shows XRD pattern of theZnO immobilized particles on glass plate subjected to heattreatment at 500∘C for 3 h The sharp intense peaks of ZnOconfirm the good crystalline nature of ZnO and form (100)(002) (101) (102) (110) (103) (200) and (112) reflections ofhexagonal ZnO The size of the particles was calculated at47 nm using (1)

Figure 5 shows SEM images of the immobilized catalyticparticles for the fresh and used ZnO Moreover the initialglass plate as well as the HF-treated surface is shown Itis evident that the glass surface becomes rough after acidtreatment (Figure 5(b)) thus facilitating catalyst attachmentFigure 5(c) shows the dispersion of fresh ZnO onto theglass surface where agglomeration of the particles takesplace to some extent Conversely Figure 5(d) shows the SEMimage of a plate that has been employed for more than30 h of photocatalytic experiments under various conditions(including runs with wastewater) It is observed that particlesdispersion is more homogeneous than that of the fresh plateand this is probably due to the presence of several organicandor inorganic impurities accumulated onto the surfaceduring its photocatalytic use The film thickness is in therange 2ndash4120583m

The effect of increasing ZnO loading in the range 12ndash153mg (05ndash68mgcm2) on BPA removal is shown in

4 International Journal of Photoenergy

813mg TiO2

(a)

1018mg TiO2

(b)

1523mg TiO2

(c)

3392mg TiO2

(d)

Figure 2 SEM images of TiO2immobilized particles on glass plate with increasing amount of catalyst from 813 to 3392mg (361 to

1507mgcm2)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

0mg813mg1018mg

1523mg3392mg

[BPA

][BP

A] 0

Figure 3 Effect of TiO2loading on the conversion of 100 120583gL BPA

in UPW

Figure 6 where the 90min conversion is enhanced from52 to 90 Notably for ZnO loadings between 16 and25mgcm2 BPA degradation remains practically unchangedat about 65

112

200

103110

102

101

002

100

Inte

nsity

(au

)

20 30 40 50 60 70 802120579 Cuk120572

Figure 4 XRD pattern of the ZnO immobilized particles on glassplate

Another interesting finding is that for the same volume ofthe catalyst aqueous suspension (ie from 200120583L to 10mL)the quantity of ZnO attached onto the glass support is 1-2orders of magnitude lower than that of TiO

2 This is due to

the fact that TiO2is known to have more hydroxyl anions

on its surface than ZnO thus enhancing the adhesion of

International Journal of Photoenergy 5

(a) (b)

(c) (d)

Figure 5 SEM images of (a) glass plates (b) glass plates treated with HF solution (c) 37mg fresh ZnO (16mgcm2) immobilized onto theplate and (d) 37mg used ZnO (16mgcm2) immobilized onto the plate

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

12mg37mg41mg

56mg153mg

Figure 6 Effect of ZnO loading on the conversion of 100 120583gL BPAin UPW

powder onto the appropriate substrate Nevertheless thisdoes not seem to affect the catalytic activity of ZnO whichon a catalyst-loading basis is more efficient than TiO

2 for

example a common BPA conversion can be achieved after90min at 18mgcm2 ZnO or 452mgcm2 TiO

2 as can be

observed from Figures 3 and 6

33 Effect of Initial BPA Concentration The effect of initialBPA concentration (50 100 and 200120583gL) on its degradationover 1507mg cm2 TiO

2was investigated and concentration-

time profiles were followed (data not shown) The 90minBPA removal was 77 plusmn 3 irrespective of the initial BPAconcentration thus implying first-order kinetics that is

minus119889 [BPA]119889119905= 119896app [BPA] lArrrArr ln [

BPA]119900

[BPA]

= 119896app119905 lArrrArr ln (1 minus 119883) = minus119896app119905(3)

where 119896app is an apparent reaction rate constant and119883 is BPAconversion independent of its initial concentration [BPA]

119900

Figure 7(a) confirms that the reaction approaches indeedfirst-order kinetics Plotting the logarithm of normalizedBPA concentration against time results in straight lines (thecoefficient of linear regression of data fitting 1199032 is between993 and 996) with a nearly common slope whichcorresponds to the apparent reaction rate constant this is 15plusmn 1 10minus3minminus1

The effect of initial BPA concentration was also studied at16mgcm2 ZnO the 90min removal was 64plusmn2 irrespectiveof the initial concentration Figure 7(b) shows the respectivefirst-order degradation kinetics fromwhich the apparent rateconstant is computed at 11 plusmn 1 10minus3minminus1 (the coefficientof linear regression of data fitting 1199032 is between 994 and996)

6 International Journal of Photoenergy

002040608

112141618

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0

02

04

06

08

1

12

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(b)

Figure 7 Effect of initial BPA concentration on its degradation in UPW at (a) 1507mgcm2 TiO2and (b) 16mgcm2 ZnO Plot of (3)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

00005

0010015

0020025

003

0 25 50 100

[BPA

][BP

A] 0

0mgL H2O2

25mgL H2O2

50mgL H2O2

100mgL H2O2

H2O2 concentration (mgL)

k(m

inminus1)

Figure 8 Effect of H2O2on the conversion of 100120583gL BPA in

UPW at 16mgcm2 ZnO Inset graph change of 119896app with H2O2

concentration

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

UPW (37mg ZnO)WW (37mg ZnO)UPW (153mg ZnO)

DW (153mg ZnO)WW (153mg ZnO)

[BPA

][BP

A] 0

Figure 9 Effect of water matrix on the conversion of 100120583gL BPAat two ZnO loadings

From the results presented so far it is evident that bothcatalysts exhibit a similar performance for BPA degradationthrough first-order kinetics We decided to expand exper-imentation with ZnO since (a) TiO

2has extensively been

studied in the literature for several environmental applica-tions and (b) ZnO has the potential to achieve improvedphotocatalytic performance as it absorbs over a wide regionof the UV-A spectrum [22] It should be mentioned herethat ZnO is generally more susceptible to photo corrosionandor chemical corrosion (ie leaching) than TiO

2and this

is a point of concern nonetheless our previous studies [13]showed that ZnO was remarkably stable during the photo-catalytic oxidation of slightly alkaline wastewater matrices

34 Effect of Hydrogen Peroxide The addition of oxidizingspecies increases the efficiency of the photocatalytic processbecause H

2O2is an electron acceptor and reacts with the

electrons of the photo-activated surface of the catalyst

H2O2+ eminus 997888rarr ∙OH+OHminus (4)

Thus the addition of peroxide constitutes an extra source ofhydroxyl radicals and increases the photoreactivity of ZnOduring the photocatalytic degradation [23]

According to our findings (Figure 8) increasing hydro-gen peroxide concentration from 0 to 100mgL results inincreased removal for example the 90min conversion is66 78 85 and 92 at 0 25 50 and 100mgL H

2O2

respectively The inset of Figure 8 shows that the respectiveapparent rate constants increase almost linearly with theamount of H

2O2added up to 100mgL

It should be noted here that H2O2was only partly

consumed during the previous photocatalytic runs as con-firmed with the peroxide test strips unfortunately precisedetermination of residual peroxide was not possible with thismethod

35 Effect of Water Matrix Figure 9 clearly shows thatBPA degradation is impeded in complex water matrices

International Journal of Photoenergy 7

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

002040608

1

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

[BPA

][BP

A] 0

50 120583gL BPA100120583gL BPA200120583gL BPA

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 10 Degradation of a mixture of BPA and EE2 in UPW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200 120583gL BPA(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

containing organic and inorganic constituents for instancethe 90min conversion is 93 65 and 41 in UPW DWand WW respectively at 153mg (68mgcm2) ZnO Therespective apparent kinetic constants are computed equal to0342 (1199032 = 0955) 0128 (1199032 = 095) and 0064minminus1(1199032 = 0979) The discrepancy by an order of magnitudebetween kinetics in UPW and WW can be explained takinginto account that (a) the oxidizing agents are competitivelyconsumed in reactions involving the residual organic fractionpresent in treated WW (ie COD = 24mgL) but notin UPW Since this is known to be refractory to biologicalor chemical oxidation [24] and constitutes most of thematrixrsquos total organic content nonselective oxidizing agentswill partly be wasted attacking this fraction (b) hydroxylradicals may be scavenged by bicarbonates and chloridespresent in WW andor DW to form the respective radicalswhose oxidation potential is lower than that of hydroxylradicals [25 26]

The experiments were repeated at a reduced ZnO loadingof 37mg (16mgcm2) In this case the 90min BPA conver-sion is 60 in UPW and decreases to 44 in WW with therespective rate constants being 12 10minus3minminus1 (1199032 = 0994) and6 10minus3minminus1 (1199032 = 0992) the ratio 119896UPW119896ww is 53 and 2at 68 and 16mgcm2 ZnO respectively These results clearlyindicate that the degree of deceleration of the photocatalyticprocess due to the complexity of the water matrix stronglydepends on the catalyst-loading

36 Degradation of EDCsMixture Experiments were carriedout to investigate the possible interactions of BPA with EE2a synthetic hormone typically found in the contraceptivepill and well-known for its interference with the endocrinesystem of living beings [27]

Figure 10(a) shows BPA concentration-time profiles (50ndash200120583gL initial concentration) in UPW and in the presence

of 100120583gL EE2 while Figure 10(b) shows EE2 concentration-time profiles (100 120583gL initial concentration) in UPW and inthe presence of different BPA concentrations in the range 0ndash200120583gL Comparing Figures 7(b) and 10(a) (inset graph) itis deduced that BPA degradation is slightly impeded by thepresence of EE2 especially at 50 and 100 120583gL BPA initialconcentrations On the other hand Figure 10(b) shows anenhancement of EE2 degradation from 79 in the absenceof BPA to 87 945 and 99 in the presence of 50 100and 200120583gL BPA respectively These results are consistentwith our previous work [16] where the photocatalytic EE2degradation was studied in the presence of BPA Possibleexplanations of this observation would involve the following(a) differences in BPA and EE2 chemical structures EE2 hasa longer molecular chain with more complicated structurethan BPA and this could render it more readily susceptible tooxidative attack (b) the simultaneous BPA-EE2 degradationmay create active radicals that would also attack firstly EE2facilitating thus its degradation and (c) EE2 due to its longerandmore complexmolecule chain may act as a shield to BPAmolecule preventing its diffusion to the catalyst surface thusdecreasing its degradability

The experiments were then performed in WW and theresults are shown in Figure 11 The previous phenomenonis far less pronounced in this case and this is possiblydue to the fact that the WW matrix has already had astrong adverse impact (see Section 35) thus masking anyinteractions between BPA and EE2

A kinetic simulation of BPA degradation in the presenceof EE2 was performed for both UPW and WW matricesBased on the experimental data shown in Figures 10(a)and 11(a) BPA degradation seems to follow near first-orderkinetics as its degradation rate does not depend stronglyon its initial concentration The apparent rate constant fordegradation in UPW is 9 plusmn 2 10minus3minminus1 (computed from the

8 International Journal of Photoenergy

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

001020304050607

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

ln(C

0C

)

BPA 50120583gLBPA 100120583gLBPA 200120583gL

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 11 Degradation of a mixture of BPA and EE2 inWW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200120583gL BPA and(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

slope of the straight lines shown in inset Figure 10(a)) anddecreases to 6 plusmn 1 10minus3minminus1 in WW (inset Figure 11(a))

4 Conclusions

Overall the removal of BPAunder simulated solar irradiationand in the presence of either TiO

2or ZnO catalysts immo-

bilized onto glass plates was investigated It was observedthat the amount of catalyst attached onto the glass platecan affect process efficiency which generally increases atincreased catalyst loadings under the conditions tested BPAremoval follows a first-order reaction rate indicating thatthe removal is not practically affected by the initial BPAconcentration in the presence of either TiO

2or ZnO catalyst

At the conditions employed in this study apparent reactionrates increase with (a) increasing H

2O2concentration in a

proportional fashion and (b) decreasing complexity of thewater matrix (ie from wastewater to drinking water toultrapure water) The presence of other EDCs such as EE2spiked in the reactionmixture does not seem to obstruct BPAdegradation

Hence solar photocatalytic treatment using immobilizedTiO2or ZnO photocatalysts can be a promising with

low energy requirements and efficient process to removeendocrine disrupting compounds found at low concentra-tions from aqueous matrices The key advantage of the pro-posed setup is that there is no need for catalyst aftertreatmentand separation in train with the photocatalytic process thusdecreasing the overall cost of a large-scale treatment plant

References

[1] P K Jjemba Pharma-Ecology The Occurrence and Fate ofPharmaceuticals andPersonal Care Products in the EnvironmentJohn Wiley amp Sons Hoboken NJ USA 2008

[2] V Belgiorno L Rizzo D Fatta et al ldquoReview on endocrinedisrupting-emerging compounds in urban wastewater occur-rence and removal by photocatalysis and ultrasonic irradiationforwastewater reuserdquoDesalination vol 215 no 1ndash3 pp 166ndash1762007

[3] C Lindholst S N Pedersen and P Bjerregaard ldquoUptakemetabolism and excretion of bisphenol A in the rainbow trout(Oncorhynchus mykiss)rdquo Aquatic Toxicology vol 55 no 1-2 pp75ndash84 2001

[4] H Barndok M Pelaez C Han et al ldquoPhotocatalytic degra-dation of contaminants of concern with composite NF-TiO

2

films under visible and solar lightrdquo Environmental Science andPollution Research vol 20 no 6 pp 3582ndash3591 2013

[5] V M Daskalaki I Fulgione Z Frontistis L Rizzo and DMantzavinos ldquoSolar light-induced photoelectrocatalytic degra-dation of bisphenol-A on TiO

2ITO film anode and BDD

cathoderdquo Catalysis Today vol 209 pp 74ndash78 2013[6] S D Richardson ldquoWater analysis emerging contaminants and

current issuesrdquo Analytical Chemistry vol 81 no 12 pp 4645ndash4677 2009

[7] C I Kosma D A Lambropoulou and T A Albanis ldquoOccur-rence and removal of PPCPs in municipal and hospital wastew-aters inGreecerdquo Journal ofHazardousMaterials vol 179 no 1ndash3pp 804ndash817 2010

[8] J L Rodrıguez-Gil M Catala S G Alonso et al ldquoHeteroge-neous photo-Fenton treatment for the reduction of pharmaceu-tical contamination in Madrid rivers and ecotoxicological eval-uation by a miniaturized fern spores bioassayrdquo Chemospherevol 80 no 4 pp 381ndash388 2010

[9] G Gatidou E Vassalou and N S Thomaidis ldquoBioconcen-tration of selected endocrine disrupting compounds in theMediterranean musselMytilus galloprovincialisrdquoMarine Pollu-tion Bulletin vol 60 no 11 pp 2111ndash2116 2010

[10] M Gros M Petrovic and D Barcelo ldquoTracing pharmaceuticalresidues of different therapeutic classes in environmental watersby using liquid chromatographyquadrupole-linear ion trapmass spectrometry and automated library searchingrdquoAnalyticalChemistry vol 81 no 3 pp 898ndash912 2009

International Journal of Photoenergy 9

[11] A S Stasinakis G Gatidou D Mamais N S Thomaidis andT D Lekkas ldquoOccurrence and fate of endocrine disrupters inGreek sewage treatment plantsrdquoWater Research vol 42 no 6-7 pp 1796ndash1804 2008

[12] M Auriol Y Filali-Meknassi R D Tyagi C D Adams and RY Surampalli ldquoEndocrine disrupting compounds removal fromwastewater a new challengerdquo Process Biochemistry vol 41 no3 pp 525ndash539 2006

[13] Z Frontistis D Fatta-Kassinos D Mantzavinos and N P Xek-oukoulotakis ldquoPhotocatalytic degradation of 17120572-ethynylestra-diol in environmental samples by ZnO under simulated solarradiationrdquo Journal of Chemical Technology and Biotechnologyvol 87 no 8 pp 1051ndash1058 2012

[14] M A Behnajady N Modirshahla N Daneshvar and MRabbani ldquoPhotocatalytic degradation of CI Acid Red 27 byimmobilized ZnO on glass plates in continuous-moderdquo Journalof Hazardous Materials vol 140 no 1-2 pp 257ndash263 2007

[15] A R Khataee ldquoPhotocatalytic removal of CI Basic Red 46on immobilized TiO

2nanoparticles artificial neural network

modellingrdquo Environmental Technology vol 30 no 11 pp 1155ndash1168 2009

[16] V Κoutantou M Kostadima E Chatzisymeon et al ldquoSolarphotocatalytic decomposition of estrogens over immobilizedzinc oxiderdquo Catalysis Today vol 209 pp 66ndash73 2013

[17] T Nakashima Y Ohko D A Tryk and A Fujishima ldquoDecom-position of endocrine-disrupting chemicals in water by useof TiO

2photocatalysts immobilized on polytetrafluoroethylene

mesh sheetsrdquo Journal of Photochemistry and Photobiology A vol151 no 1ndash3 pp 207ndash212 2002

[18] V M Daskalaki Z Frontistis D Mantzavinos and A Katsaou-nis ldquoSolar light-induced degradation of bisphenol-A with TiO

2

immobilized on Tirdquo Catalysis Today vol 161 no 1 pp 110ndash1142011

[19] J Gunlazuardi andW A Lindu ldquoPhotocatalytic degradation ofpentachlorophenol in aqueous solution employing immobilizedTiO2supported on titanium metalrdquo Journal of Photochemistry

and Photobiology A vol 173 no 1 pp 51ndash55 2005[20] R Wang D Ren S Xia Y Zhang and J Zhao ldquoPhotocatalytic

degradation of Bisphenol A (BPA) using immobilized TiO2and

UV illumination in a horizontal circulating bed photocatalyticreactor (HCBPR)rdquo Journal of Hazardous Materials vol 169 no1ndash3 pp 926ndash932 2009

[21] E S Galbavy K Ram and C Anastasio ldquo2-Nitrobenzaldehydeas a chemical actinometer for solution and ice photochemistryrdquoJournal of Photochemistry and Photobiology A vol 209 no 2-3pp 186ndash192 2010

[22] M A Behnajady N Modirshahla and R Hamzavi ldquoKineticstudy on photocatalytic degradation of CI Acid Yellow 23 byZnOphotocatalystrdquo Journal ofHazardousMaterials vol 133 no1ndash3 pp 226ndash232 2006

[23] F Mendez-Arriaga M I Maldonado J Gimenez S Esplugasand S Malato ldquoAbatement of ibuprofen by solar photocatalysisprocess enhancement and scale uprdquo Catalysis Today vol 144no 1-2 pp 112ndash116 2009

[24] Z Frontistis and D Mantzavinos ldquoSonodegradation of 17120572-ethynylestradiol in environmentally relevant matrices labora-tory-scale kinetic studiesrdquo Ultrasonics Sonochemistry vol 19no 1 pp 77ndash84 2012

[25] L A T Espinoza M Neamtu and F H Frimmel ldquoThe effect ofnitrate Fe(III) and bicarbonate on the degradation of bisphenolA by simulated solar UV-irradiationrdquo Water Research vol 41no 19 pp 4479ndash4487 2007

[26] C Sirtori A Aguera W Gernjak and S Malato ldquoEffect ofwater-matrix composition on trimethoprim solar photodegra-dation kinetics and pathwaysrdquoWater Research vol 44 no 9 pp2735ndash2744 2010

[27] Z Frontistis C Drosou K Tyrovola et al ldquoExperimental andmodeling studies of the degradation of estrogen hormones inaqueous TiO

2suspensions under simulated solar radiationrdquo

Industrial and Engineering Chemistry Research vol 51 no 51pp 16552ndash16563 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

2 International Journal of Photoenergy

the efficiency of the existing treatment systems and to developnew and reliable treatment strategies to remove EDCs fromwastewaters

Semiconductor photocatalysis using solar radiation asthe source of photons for the activation of the catalyst hasreceived considerable attention over the past several yearsSeveral heterogeneous photocatalysts have been investigatedand amongst them the use of TiO

2under ultraviolet andor

visible light has extensively been researched Another photo-catalyst that absorbs over a large fraction of the solar spec-trum is ZnO with a gap energy of 32 eV The photocatalyticmechanism of ZnO is similar to that of TiO

2[13] Moreover

solar photocatalysis is considered as a cost-effective andsustainable treatment technique due to the utilization of solarenergy (an abundant source of energy) However the biggestproblem with slurry photocatalysis has been recognizedto be the need for a posttreatment recovery step [14 15]Therefore research has been conducted to produce catalystson supports that would keep the catalyst powder out of thetreated water and sufficiently reduce even more the cost ofthe photocatalytic process since there will be no need forcatalyst aftertreatment So far few studies have dealt withthe treatment of EDCs by means of TiO

2or ZnO catalysts

immobilized onto supports such as glass [4 16] PTFE meshsheets [17] titanium substrates [18 19] and polyurethanefoam cubes [20]

Hence in this work the efficacy of solar photocatalyticprocess to remove BPA from aqueous environmental sampleswas investigated For this purpose two different photocat-alytic materials namely ZnO and TiO

2 were immobilized

onto appropriate glass substrate by means of a heat attach-ment technique The effect of various operating parameterssuch as the immobilized catalyst amount the initial BPA con-centration the treatment time the water matrix the additionof H2O2 and the presence of other organic substances on

process efficiency was investigated

2 Materials and Methods

21 Materials BPA and 17120572-ethynylestradiol (EE2) werepurchased from Sigma-Aldrich while ZnO (ge99 particlesize lt 100 nm 15ndash25m2g BET surface area) and TiO

2-

P25 (anatase rutile 75 25 21 nm primary crystallite particlesize 50m2g BET surface area) were purchased from Flukaand Degussa-Evonik Corp respectively The water matrixwas either of the following three (i) wastewater (WW)collected from the outlet of the secondary treatment ofthe municipal WWTP of Chania W Crete Greece (ii)commercially available bottled water which will be referredto in the text as drinkingwater (DW) and (iii) ultrapurewater(UPW) at pH = 61 taken from a water purification sys-tem (EASYpureRF-BarnsteadThermolyne USA) The mainproperties of WW and DW are given in Table 1

22 Catalyst Preparation The ZnO or TiO2catalyst powders

were immobilized on glass plates (15 cm times 15 cm) by aheat attachment method Analytically the glass plates werefirst treated with a 38 HF solution and then washed with

Table 1 Properties of wastewater and drinking water matrices usedin this study

Parameter Wastewater Drinking waterpH 8 77TOC (mgL) 78 03COD (mgL) 24 NDConductivity (120583scm) 820 329HCO

3

minus (mgL) 190 188Clminus (mgL) 220 lt5NO2

minus (mgL) 57 lt009NO3

minus (mgL) 26 lt5ND not determined

001MNaOH in order to increase the number of OH groupsand achieve better contact of the catalyst on glass plates[14] Moreover a suspension of 8 gL catalyst in distilledwater was preparedThis suspension was sonicated at 80 kHzfor 120min in order to improve the dispersion of the solidcatalyst in water Afterwards the sonicated catalyst solutionwas poured on the glass plates at various volumes rangingfrom some 120583L to about 10mL and then placed in an oven at120∘C for 60min After drying the glass plates were calcinedat 500∘C for 180min Finally the glass plates were washedwith distilled water to remove the loosely attached catalyticparticles

23 Catalyst Characterization Techniques The crystal struc-ture particle size and morphology were examined with apowder X-ray diffraction (XRD) system and scanning elec-tron microscopy (SEM) respectively XRD patterns werecollected on a Rigaku DMAX-2000H rotating anode dif-fractometer (Cuk120572 radiation) equipped with a secondarypyrolytic graphite monochromator operating at 40 kV and80mA over the 2120579 collection range of 10ndash80∘ The scan ratewas 005min with a step size of 001 Surface morphologyof the catalytic plates was carried out on a JEOL JSM-6400VSEM instrument

24 Photocatalytic Experiments Photocatalytic experimentswere performed using a solar simulator (Newport model96000) equipped with a 150W xenon ozone-free lamp andan Air Mass 15 Global Filter (Newport model 81094)simulating solar radiation reaching the surface of the earthat a zenith angle of 482∘

The incident radiation intensity on the photochemicalreactor in the UV region of the electromagnetic spectrumwas measured actinometrically using 2-nitrobenzaldehyde(purchased from Sigma-Aldrich) as the chemical actinometer[21] and it was found to be 165 10minus5 einsteinm2 In a typicalphotocatalytic run 64mL of the water matrix spiked withthe appropriate amount of the organic substance was fed ina cylindrical pyrex cell and the ZnO or TiO

2catalytic plate

was added while the cell was open to the atmosphere Thesolar simulator was placed on top of the liquid surface whilethe catalytic glass plate was held by a Ti support dipped into

International Journal of Photoenergy 3

Inte

nsity

(au

)

A

A A

R

A

10 20 30 40 50 60 70 802120579 Cuk120572

Figure 1 XRD pattern of the TiO2immobilized particles on glass

plate (A anatase R rutile)

the reactionmixture Samples of about 1mLwere periodicallytaken from the cell and analyzed as follows

25 Analytical Techniques High-performance liquid chro-matography (Alliance 2690 Waters) was employed to mon-itor the concentrations of BPA and EE2 Separation wasachieved on a Luna C-18(2) column (5120583m 250mm times46mm) and a security guard column (4mm times 3mm) bothpurchased from Phenomenex The mobile phase consistsof 35 65 UPW acetonitrile eluted isocratically at 1mLminand 30∘C while the injection volume was 100120583L Detectionwas achieved through a fluorescence detector (Waters 474)in which the excitation wavelength was 280 nm and theemission wavelength was 305 nm Under these conditionsthe retention time for BPA was 43min the limit of detectionwas 068120583gL and the limit of quantitation was 232 120583gLthe respective values for EE2 were 51min 063 120583gL and211 120583gL Residual H

2O2concentration was monitored using

Merck peroxide test strips in the range 0ndash100mgL Changesin effluent pH during photocatalytic treatment were checkedusing a Toledo 225 pH meter

3 Results and Discussion

31 TiO2Catalyst Plates Figure 1 shows XRD pattern of the

TiO2immobilized particles on glass plate subjected to heat

treatment at 500∘C for 3 h Peaks at 2120579 values of 25∘ and27∘ correspond to the anatase (101) and rutile (110) planesrespectively The crystalline size (119863) was calculated at 17 nmusing the Scherrer equation

119863 =119896120582

120573 cos 120579 (1)

where 119896 is a constant equal to 09 120582 is the wavelength ofcharacteristics X-ray applied (015418 nm) 120573 is the full widthat half maximum of the anatase (101) peak obtained by XRDand 120579 is the Bragg angle

The phase content of TiO2particles can be calculated as

follows

119891119860=

1

1 + 119868119877079119868

119860

(2)

where 119891119860is the content of anatase and 119868

119860and 119868119877are the

integrated intensities of the anatase (101) and rutile (110)peaks respectively The TiO

2catalytic plate mainly consists

of the anatase phase with mirror rutile phase (70 30)Figure 2 shows SEM images of the immobilized catalytic

particles on glass plates with different amounts of TiO2in the

range 813ndash3392mg (361ndash1507mgcm2) The TiO2layer is

homogeneouswith a porous surface while themorphology ofTiO2particles is amorphous As the amount of TiO

2increases

the homogeneity increases and so does the film thickness inthe range 2ndash6120583m

The effect of increasing the amount of immobilized TiO2

on BPA removal is shown in Figure 3 the 90min conversionincreases from 60 to 80 as TiO

2increases from 361 to

1507mgcm2 and this is expected sincemore catalyst surfacesites are available for reaction at higher catalyst loadingsAn additional run was performed in the absence of catalystyielding only 15photolytic removal after 90min Since TiO

2

in slurry has extensively been used for photocatalytic pur-poses an extra runwas carried out to compare the efficienciesof slurry and immobilized catalysts Hence 065mg TiO

2

powder was added to the reaction mixture and completeremoval of 100 120583gL BPA could be achieved after 35min ofreaction (data not shown) This shows that slurry catalystseven at extremely low concentrations yield higher reactionrates than the immobilized systems presumably due to lowermass transfer limitations

32 ZnO Catalyst Plates Figure 4 shows XRD pattern of theZnO immobilized particles on glass plate subjected to heattreatment at 500∘C for 3 h The sharp intense peaks of ZnOconfirm the good crystalline nature of ZnO and form (100)(002) (101) (102) (110) (103) (200) and (112) reflections ofhexagonal ZnO The size of the particles was calculated at47 nm using (1)

Figure 5 shows SEM images of the immobilized catalyticparticles for the fresh and used ZnO Moreover the initialglass plate as well as the HF-treated surface is shown Itis evident that the glass surface becomes rough after acidtreatment (Figure 5(b)) thus facilitating catalyst attachmentFigure 5(c) shows the dispersion of fresh ZnO onto theglass surface where agglomeration of the particles takesplace to some extent Conversely Figure 5(d) shows the SEMimage of a plate that has been employed for more than30 h of photocatalytic experiments under various conditions(including runs with wastewater) It is observed that particlesdispersion is more homogeneous than that of the fresh plateand this is probably due to the presence of several organicandor inorganic impurities accumulated onto the surfaceduring its photocatalytic use The film thickness is in therange 2ndash4120583m

The effect of increasing ZnO loading in the range 12ndash153mg (05ndash68mgcm2) on BPA removal is shown in

4 International Journal of Photoenergy

813mg TiO2

(a)

1018mg TiO2

(b)

1523mg TiO2

(c)

3392mg TiO2

(d)

Figure 2 SEM images of TiO2immobilized particles on glass plate with increasing amount of catalyst from 813 to 3392mg (361 to

1507mgcm2)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

0mg813mg1018mg

1523mg3392mg

[BPA

][BP

A] 0

Figure 3 Effect of TiO2loading on the conversion of 100 120583gL BPA

in UPW

Figure 6 where the 90min conversion is enhanced from52 to 90 Notably for ZnO loadings between 16 and25mgcm2 BPA degradation remains practically unchangedat about 65

112

200

103110

102

101

002

100

Inte

nsity

(au

)

20 30 40 50 60 70 802120579 Cuk120572

Figure 4 XRD pattern of the ZnO immobilized particles on glassplate

Another interesting finding is that for the same volume ofthe catalyst aqueous suspension (ie from 200120583L to 10mL)the quantity of ZnO attached onto the glass support is 1-2orders of magnitude lower than that of TiO

2 This is due to

the fact that TiO2is known to have more hydroxyl anions

on its surface than ZnO thus enhancing the adhesion of

International Journal of Photoenergy 5

(a) (b)

(c) (d)

Figure 5 SEM images of (a) glass plates (b) glass plates treated with HF solution (c) 37mg fresh ZnO (16mgcm2) immobilized onto theplate and (d) 37mg used ZnO (16mgcm2) immobilized onto the plate

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

12mg37mg41mg

56mg153mg

Figure 6 Effect of ZnO loading on the conversion of 100 120583gL BPAin UPW

powder onto the appropriate substrate Nevertheless thisdoes not seem to affect the catalytic activity of ZnO whichon a catalyst-loading basis is more efficient than TiO

2 for

example a common BPA conversion can be achieved after90min at 18mgcm2 ZnO or 452mgcm2 TiO

2 as can be

observed from Figures 3 and 6

33 Effect of Initial BPA Concentration The effect of initialBPA concentration (50 100 and 200120583gL) on its degradationover 1507mg cm2 TiO

2was investigated and concentration-

time profiles were followed (data not shown) The 90minBPA removal was 77 plusmn 3 irrespective of the initial BPAconcentration thus implying first-order kinetics that is

minus119889 [BPA]119889119905= 119896app [BPA] lArrrArr ln [

BPA]119900

[BPA]

= 119896app119905 lArrrArr ln (1 minus 119883) = minus119896app119905(3)

where 119896app is an apparent reaction rate constant and119883 is BPAconversion independent of its initial concentration [BPA]

119900

Figure 7(a) confirms that the reaction approaches indeedfirst-order kinetics Plotting the logarithm of normalizedBPA concentration against time results in straight lines (thecoefficient of linear regression of data fitting 1199032 is between993 and 996) with a nearly common slope whichcorresponds to the apparent reaction rate constant this is 15plusmn 1 10minus3minminus1

The effect of initial BPA concentration was also studied at16mgcm2 ZnO the 90min removal was 64plusmn2 irrespectiveof the initial concentration Figure 7(b) shows the respectivefirst-order degradation kinetics fromwhich the apparent rateconstant is computed at 11 plusmn 1 10minus3minminus1 (the coefficientof linear regression of data fitting 1199032 is between 994 and996)

6 International Journal of Photoenergy

002040608

112141618

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0

02

04

06

08

1

12

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(b)

Figure 7 Effect of initial BPA concentration on its degradation in UPW at (a) 1507mgcm2 TiO2and (b) 16mgcm2 ZnO Plot of (3)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

00005

0010015

0020025

003

0 25 50 100

[BPA

][BP

A] 0

0mgL H2O2

25mgL H2O2

50mgL H2O2

100mgL H2O2

H2O2 concentration (mgL)

k(m

inminus1)

Figure 8 Effect of H2O2on the conversion of 100120583gL BPA in

UPW at 16mgcm2 ZnO Inset graph change of 119896app with H2O2

concentration

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

UPW (37mg ZnO)WW (37mg ZnO)UPW (153mg ZnO)

DW (153mg ZnO)WW (153mg ZnO)

[BPA

][BP

A] 0

Figure 9 Effect of water matrix on the conversion of 100120583gL BPAat two ZnO loadings

From the results presented so far it is evident that bothcatalysts exhibit a similar performance for BPA degradationthrough first-order kinetics We decided to expand exper-imentation with ZnO since (a) TiO

2has extensively been

studied in the literature for several environmental applica-tions and (b) ZnO has the potential to achieve improvedphotocatalytic performance as it absorbs over a wide regionof the UV-A spectrum [22] It should be mentioned herethat ZnO is generally more susceptible to photo corrosionandor chemical corrosion (ie leaching) than TiO

2and this

is a point of concern nonetheless our previous studies [13]showed that ZnO was remarkably stable during the photo-catalytic oxidation of slightly alkaline wastewater matrices

34 Effect of Hydrogen Peroxide The addition of oxidizingspecies increases the efficiency of the photocatalytic processbecause H

2O2is an electron acceptor and reacts with the

electrons of the photo-activated surface of the catalyst

H2O2+ eminus 997888rarr ∙OH+OHminus (4)

Thus the addition of peroxide constitutes an extra source ofhydroxyl radicals and increases the photoreactivity of ZnOduring the photocatalytic degradation [23]

According to our findings (Figure 8) increasing hydro-gen peroxide concentration from 0 to 100mgL results inincreased removal for example the 90min conversion is66 78 85 and 92 at 0 25 50 and 100mgL H

2O2

respectively The inset of Figure 8 shows that the respectiveapparent rate constants increase almost linearly with theamount of H

2O2added up to 100mgL

It should be noted here that H2O2was only partly

consumed during the previous photocatalytic runs as con-firmed with the peroxide test strips unfortunately precisedetermination of residual peroxide was not possible with thismethod

35 Effect of Water Matrix Figure 9 clearly shows thatBPA degradation is impeded in complex water matrices

International Journal of Photoenergy 7

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

002040608

1

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

[BPA

][BP

A] 0

50 120583gL BPA100120583gL BPA200120583gL BPA

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 10 Degradation of a mixture of BPA and EE2 in UPW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200 120583gL BPA(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

containing organic and inorganic constituents for instancethe 90min conversion is 93 65 and 41 in UPW DWand WW respectively at 153mg (68mgcm2) ZnO Therespective apparent kinetic constants are computed equal to0342 (1199032 = 0955) 0128 (1199032 = 095) and 0064minminus1(1199032 = 0979) The discrepancy by an order of magnitudebetween kinetics in UPW and WW can be explained takinginto account that (a) the oxidizing agents are competitivelyconsumed in reactions involving the residual organic fractionpresent in treated WW (ie COD = 24mgL) but notin UPW Since this is known to be refractory to biologicalor chemical oxidation [24] and constitutes most of thematrixrsquos total organic content nonselective oxidizing agentswill partly be wasted attacking this fraction (b) hydroxylradicals may be scavenged by bicarbonates and chloridespresent in WW andor DW to form the respective radicalswhose oxidation potential is lower than that of hydroxylradicals [25 26]

The experiments were repeated at a reduced ZnO loadingof 37mg (16mgcm2) In this case the 90min BPA conver-sion is 60 in UPW and decreases to 44 in WW with therespective rate constants being 12 10minus3minminus1 (1199032 = 0994) and6 10minus3minminus1 (1199032 = 0992) the ratio 119896UPW119896ww is 53 and 2at 68 and 16mgcm2 ZnO respectively These results clearlyindicate that the degree of deceleration of the photocatalyticprocess due to the complexity of the water matrix stronglydepends on the catalyst-loading

36 Degradation of EDCsMixture Experiments were carriedout to investigate the possible interactions of BPA with EE2a synthetic hormone typically found in the contraceptivepill and well-known for its interference with the endocrinesystem of living beings [27]

Figure 10(a) shows BPA concentration-time profiles (50ndash200120583gL initial concentration) in UPW and in the presence

of 100120583gL EE2 while Figure 10(b) shows EE2 concentration-time profiles (100 120583gL initial concentration) in UPW and inthe presence of different BPA concentrations in the range 0ndash200120583gL Comparing Figures 7(b) and 10(a) (inset graph) itis deduced that BPA degradation is slightly impeded by thepresence of EE2 especially at 50 and 100 120583gL BPA initialconcentrations On the other hand Figure 10(b) shows anenhancement of EE2 degradation from 79 in the absenceof BPA to 87 945 and 99 in the presence of 50 100and 200120583gL BPA respectively These results are consistentwith our previous work [16] where the photocatalytic EE2degradation was studied in the presence of BPA Possibleexplanations of this observation would involve the following(a) differences in BPA and EE2 chemical structures EE2 hasa longer molecular chain with more complicated structurethan BPA and this could render it more readily susceptible tooxidative attack (b) the simultaneous BPA-EE2 degradationmay create active radicals that would also attack firstly EE2facilitating thus its degradation and (c) EE2 due to its longerandmore complexmolecule chain may act as a shield to BPAmolecule preventing its diffusion to the catalyst surface thusdecreasing its degradability

The experiments were then performed in WW and theresults are shown in Figure 11 The previous phenomenonis far less pronounced in this case and this is possiblydue to the fact that the WW matrix has already had astrong adverse impact (see Section 35) thus masking anyinteractions between BPA and EE2

A kinetic simulation of BPA degradation in the presenceof EE2 was performed for both UPW and WW matricesBased on the experimental data shown in Figures 10(a)and 11(a) BPA degradation seems to follow near first-orderkinetics as its degradation rate does not depend stronglyon its initial concentration The apparent rate constant fordegradation in UPW is 9 plusmn 2 10minus3minminus1 (computed from the

8 International Journal of Photoenergy

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

001020304050607

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

ln(C

0C

)

BPA 50120583gLBPA 100120583gLBPA 200120583gL

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 11 Degradation of a mixture of BPA and EE2 inWW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200120583gL BPA and(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

slope of the straight lines shown in inset Figure 10(a)) anddecreases to 6 plusmn 1 10minus3minminus1 in WW (inset Figure 11(a))

4 Conclusions

Overall the removal of BPAunder simulated solar irradiationand in the presence of either TiO

2or ZnO catalysts immo-

bilized onto glass plates was investigated It was observedthat the amount of catalyst attached onto the glass platecan affect process efficiency which generally increases atincreased catalyst loadings under the conditions tested BPAremoval follows a first-order reaction rate indicating thatthe removal is not practically affected by the initial BPAconcentration in the presence of either TiO

2or ZnO catalyst

At the conditions employed in this study apparent reactionrates increase with (a) increasing H

2O2concentration in a

proportional fashion and (b) decreasing complexity of thewater matrix (ie from wastewater to drinking water toultrapure water) The presence of other EDCs such as EE2spiked in the reactionmixture does not seem to obstruct BPAdegradation

Hence solar photocatalytic treatment using immobilizedTiO2or ZnO photocatalysts can be a promising with

low energy requirements and efficient process to removeendocrine disrupting compounds found at low concentra-tions from aqueous matrices The key advantage of the pro-posed setup is that there is no need for catalyst aftertreatmentand separation in train with the photocatalytic process thusdecreasing the overall cost of a large-scale treatment plant

References

[1] P K Jjemba Pharma-Ecology The Occurrence and Fate ofPharmaceuticals andPersonal Care Products in the EnvironmentJohn Wiley amp Sons Hoboken NJ USA 2008

[2] V Belgiorno L Rizzo D Fatta et al ldquoReview on endocrinedisrupting-emerging compounds in urban wastewater occur-rence and removal by photocatalysis and ultrasonic irradiationforwastewater reuserdquoDesalination vol 215 no 1ndash3 pp 166ndash1762007

[3] C Lindholst S N Pedersen and P Bjerregaard ldquoUptakemetabolism and excretion of bisphenol A in the rainbow trout(Oncorhynchus mykiss)rdquo Aquatic Toxicology vol 55 no 1-2 pp75ndash84 2001

[4] H Barndok M Pelaez C Han et al ldquoPhotocatalytic degra-dation of contaminants of concern with composite NF-TiO

2

films under visible and solar lightrdquo Environmental Science andPollution Research vol 20 no 6 pp 3582ndash3591 2013

[5] V M Daskalaki I Fulgione Z Frontistis L Rizzo and DMantzavinos ldquoSolar light-induced photoelectrocatalytic degra-dation of bisphenol-A on TiO

2ITO film anode and BDD

cathoderdquo Catalysis Today vol 209 pp 74ndash78 2013[6] S D Richardson ldquoWater analysis emerging contaminants and

current issuesrdquo Analytical Chemistry vol 81 no 12 pp 4645ndash4677 2009

[7] C I Kosma D A Lambropoulou and T A Albanis ldquoOccur-rence and removal of PPCPs in municipal and hospital wastew-aters inGreecerdquo Journal ofHazardousMaterials vol 179 no 1ndash3pp 804ndash817 2010

[8] J L Rodrıguez-Gil M Catala S G Alonso et al ldquoHeteroge-neous photo-Fenton treatment for the reduction of pharmaceu-tical contamination in Madrid rivers and ecotoxicological eval-uation by a miniaturized fern spores bioassayrdquo Chemospherevol 80 no 4 pp 381ndash388 2010

[9] G Gatidou E Vassalou and N S Thomaidis ldquoBioconcen-tration of selected endocrine disrupting compounds in theMediterranean musselMytilus galloprovincialisrdquoMarine Pollu-tion Bulletin vol 60 no 11 pp 2111ndash2116 2010

[10] M Gros M Petrovic and D Barcelo ldquoTracing pharmaceuticalresidues of different therapeutic classes in environmental watersby using liquid chromatographyquadrupole-linear ion trapmass spectrometry and automated library searchingrdquoAnalyticalChemistry vol 81 no 3 pp 898ndash912 2009

International Journal of Photoenergy 9

[11] A S Stasinakis G Gatidou D Mamais N S Thomaidis andT D Lekkas ldquoOccurrence and fate of endocrine disrupters inGreek sewage treatment plantsrdquoWater Research vol 42 no 6-7 pp 1796ndash1804 2008

[12] M Auriol Y Filali-Meknassi R D Tyagi C D Adams and RY Surampalli ldquoEndocrine disrupting compounds removal fromwastewater a new challengerdquo Process Biochemistry vol 41 no3 pp 525ndash539 2006

[13] Z Frontistis D Fatta-Kassinos D Mantzavinos and N P Xek-oukoulotakis ldquoPhotocatalytic degradation of 17120572-ethynylestra-diol in environmental samples by ZnO under simulated solarradiationrdquo Journal of Chemical Technology and Biotechnologyvol 87 no 8 pp 1051ndash1058 2012

[14] M A Behnajady N Modirshahla N Daneshvar and MRabbani ldquoPhotocatalytic degradation of CI Acid Red 27 byimmobilized ZnO on glass plates in continuous-moderdquo Journalof Hazardous Materials vol 140 no 1-2 pp 257ndash263 2007

[15] A R Khataee ldquoPhotocatalytic removal of CI Basic Red 46on immobilized TiO

2nanoparticles artificial neural network

modellingrdquo Environmental Technology vol 30 no 11 pp 1155ndash1168 2009

[16] V Κoutantou M Kostadima E Chatzisymeon et al ldquoSolarphotocatalytic decomposition of estrogens over immobilizedzinc oxiderdquo Catalysis Today vol 209 pp 66ndash73 2013

[17] T Nakashima Y Ohko D A Tryk and A Fujishima ldquoDecom-position of endocrine-disrupting chemicals in water by useof TiO

2photocatalysts immobilized on polytetrafluoroethylene

mesh sheetsrdquo Journal of Photochemistry and Photobiology A vol151 no 1ndash3 pp 207ndash212 2002

[18] V M Daskalaki Z Frontistis D Mantzavinos and A Katsaou-nis ldquoSolar light-induced degradation of bisphenol-A with TiO

2

immobilized on Tirdquo Catalysis Today vol 161 no 1 pp 110ndash1142011

[19] J Gunlazuardi andW A Lindu ldquoPhotocatalytic degradation ofpentachlorophenol in aqueous solution employing immobilizedTiO2supported on titanium metalrdquo Journal of Photochemistry

and Photobiology A vol 173 no 1 pp 51ndash55 2005[20] R Wang D Ren S Xia Y Zhang and J Zhao ldquoPhotocatalytic

degradation of Bisphenol A (BPA) using immobilized TiO2and

UV illumination in a horizontal circulating bed photocatalyticreactor (HCBPR)rdquo Journal of Hazardous Materials vol 169 no1ndash3 pp 926ndash932 2009

[21] E S Galbavy K Ram and C Anastasio ldquo2-Nitrobenzaldehydeas a chemical actinometer for solution and ice photochemistryrdquoJournal of Photochemistry and Photobiology A vol 209 no 2-3pp 186ndash192 2010

[22] M A Behnajady N Modirshahla and R Hamzavi ldquoKineticstudy on photocatalytic degradation of CI Acid Yellow 23 byZnOphotocatalystrdquo Journal ofHazardousMaterials vol 133 no1ndash3 pp 226ndash232 2006

[23] F Mendez-Arriaga M I Maldonado J Gimenez S Esplugasand S Malato ldquoAbatement of ibuprofen by solar photocatalysisprocess enhancement and scale uprdquo Catalysis Today vol 144no 1-2 pp 112ndash116 2009

[24] Z Frontistis and D Mantzavinos ldquoSonodegradation of 17120572-ethynylestradiol in environmentally relevant matrices labora-tory-scale kinetic studiesrdquo Ultrasonics Sonochemistry vol 19no 1 pp 77ndash84 2012

[25] L A T Espinoza M Neamtu and F H Frimmel ldquoThe effect ofnitrate Fe(III) and bicarbonate on the degradation of bisphenolA by simulated solar UV-irradiationrdquo Water Research vol 41no 19 pp 4479ndash4487 2007

[26] C Sirtori A Aguera W Gernjak and S Malato ldquoEffect ofwater-matrix composition on trimethoprim solar photodegra-dation kinetics and pathwaysrdquoWater Research vol 44 no 9 pp2735ndash2744 2010

[27] Z Frontistis C Drosou K Tyrovola et al ldquoExperimental andmodeling studies of the degradation of estrogen hormones inaqueous TiO

2suspensions under simulated solar radiationrdquo

Industrial and Engineering Chemistry Research vol 51 no 51pp 16552ndash16563 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

International Journal of Photoenergy 3

Inte

nsity

(au

)

A

A A

R

A

10 20 30 40 50 60 70 802120579 Cuk120572

Figure 1 XRD pattern of the TiO2immobilized particles on glass

plate (A anatase R rutile)

the reactionmixture Samples of about 1mLwere periodicallytaken from the cell and analyzed as follows

25 Analytical Techniques High-performance liquid chro-matography (Alliance 2690 Waters) was employed to mon-itor the concentrations of BPA and EE2 Separation wasachieved on a Luna C-18(2) column (5120583m 250mm times46mm) and a security guard column (4mm times 3mm) bothpurchased from Phenomenex The mobile phase consistsof 35 65 UPW acetonitrile eluted isocratically at 1mLminand 30∘C while the injection volume was 100120583L Detectionwas achieved through a fluorescence detector (Waters 474)in which the excitation wavelength was 280 nm and theemission wavelength was 305 nm Under these conditionsthe retention time for BPA was 43min the limit of detectionwas 068120583gL and the limit of quantitation was 232 120583gLthe respective values for EE2 were 51min 063 120583gL and211 120583gL Residual H

2O2concentration was monitored using

Merck peroxide test strips in the range 0ndash100mgL Changesin effluent pH during photocatalytic treatment were checkedusing a Toledo 225 pH meter

3 Results and Discussion

31 TiO2Catalyst Plates Figure 1 shows XRD pattern of the

TiO2immobilized particles on glass plate subjected to heat

treatment at 500∘C for 3 h Peaks at 2120579 values of 25∘ and27∘ correspond to the anatase (101) and rutile (110) planesrespectively The crystalline size (119863) was calculated at 17 nmusing the Scherrer equation

119863 =119896120582

120573 cos 120579 (1)

where 119896 is a constant equal to 09 120582 is the wavelength ofcharacteristics X-ray applied (015418 nm) 120573 is the full widthat half maximum of the anatase (101) peak obtained by XRDand 120579 is the Bragg angle

The phase content of TiO2particles can be calculated as

follows

119891119860=

1

1 + 119868119877079119868

119860

(2)

where 119891119860is the content of anatase and 119868

119860and 119868119877are the

integrated intensities of the anatase (101) and rutile (110)peaks respectively The TiO

2catalytic plate mainly consists

of the anatase phase with mirror rutile phase (70 30)Figure 2 shows SEM images of the immobilized catalytic

particles on glass plates with different amounts of TiO2in the

range 813ndash3392mg (361ndash1507mgcm2) The TiO2layer is

homogeneouswith a porous surface while themorphology ofTiO2particles is amorphous As the amount of TiO

2increases

the homogeneity increases and so does the film thickness inthe range 2ndash6120583m

The effect of increasing the amount of immobilized TiO2

on BPA removal is shown in Figure 3 the 90min conversionincreases from 60 to 80 as TiO

2increases from 361 to

1507mgcm2 and this is expected sincemore catalyst surfacesites are available for reaction at higher catalyst loadingsAn additional run was performed in the absence of catalystyielding only 15photolytic removal after 90min Since TiO

2

in slurry has extensively been used for photocatalytic pur-poses an extra runwas carried out to compare the efficienciesof slurry and immobilized catalysts Hence 065mg TiO

2

powder was added to the reaction mixture and completeremoval of 100 120583gL BPA could be achieved after 35min ofreaction (data not shown) This shows that slurry catalystseven at extremely low concentrations yield higher reactionrates than the immobilized systems presumably due to lowermass transfer limitations

32 ZnO Catalyst Plates Figure 4 shows XRD pattern of theZnO immobilized particles on glass plate subjected to heattreatment at 500∘C for 3 h The sharp intense peaks of ZnOconfirm the good crystalline nature of ZnO and form (100)(002) (101) (102) (110) (103) (200) and (112) reflections ofhexagonal ZnO The size of the particles was calculated at47 nm using (1)

Figure 5 shows SEM images of the immobilized catalyticparticles for the fresh and used ZnO Moreover the initialglass plate as well as the HF-treated surface is shown Itis evident that the glass surface becomes rough after acidtreatment (Figure 5(b)) thus facilitating catalyst attachmentFigure 5(c) shows the dispersion of fresh ZnO onto theglass surface where agglomeration of the particles takesplace to some extent Conversely Figure 5(d) shows the SEMimage of a plate that has been employed for more than30 h of photocatalytic experiments under various conditions(including runs with wastewater) It is observed that particlesdispersion is more homogeneous than that of the fresh plateand this is probably due to the presence of several organicandor inorganic impurities accumulated onto the surfaceduring its photocatalytic use The film thickness is in therange 2ndash4120583m

The effect of increasing ZnO loading in the range 12ndash153mg (05ndash68mgcm2) on BPA removal is shown in

4 International Journal of Photoenergy

813mg TiO2

(a)

1018mg TiO2

(b)

1523mg TiO2

(c)

3392mg TiO2

(d)

Figure 2 SEM images of TiO2immobilized particles on glass plate with increasing amount of catalyst from 813 to 3392mg (361 to

1507mgcm2)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

0mg813mg1018mg

1523mg3392mg

[BPA

][BP

A] 0

Figure 3 Effect of TiO2loading on the conversion of 100 120583gL BPA

in UPW

Figure 6 where the 90min conversion is enhanced from52 to 90 Notably for ZnO loadings between 16 and25mgcm2 BPA degradation remains practically unchangedat about 65

112

200

103110

102

101

002

100

Inte

nsity

(au

)

20 30 40 50 60 70 802120579 Cuk120572

Figure 4 XRD pattern of the ZnO immobilized particles on glassplate

Another interesting finding is that for the same volume ofthe catalyst aqueous suspension (ie from 200120583L to 10mL)the quantity of ZnO attached onto the glass support is 1-2orders of magnitude lower than that of TiO

2 This is due to

the fact that TiO2is known to have more hydroxyl anions

on its surface than ZnO thus enhancing the adhesion of

International Journal of Photoenergy 5

(a) (b)

(c) (d)

Figure 5 SEM images of (a) glass plates (b) glass plates treated with HF solution (c) 37mg fresh ZnO (16mgcm2) immobilized onto theplate and (d) 37mg used ZnO (16mgcm2) immobilized onto the plate

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

12mg37mg41mg

56mg153mg

Figure 6 Effect of ZnO loading on the conversion of 100 120583gL BPAin UPW

powder onto the appropriate substrate Nevertheless thisdoes not seem to affect the catalytic activity of ZnO whichon a catalyst-loading basis is more efficient than TiO

2 for

example a common BPA conversion can be achieved after90min at 18mgcm2 ZnO or 452mgcm2 TiO

2 as can be

observed from Figures 3 and 6

33 Effect of Initial BPA Concentration The effect of initialBPA concentration (50 100 and 200120583gL) on its degradationover 1507mg cm2 TiO

2was investigated and concentration-

time profiles were followed (data not shown) The 90minBPA removal was 77 plusmn 3 irrespective of the initial BPAconcentration thus implying first-order kinetics that is

minus119889 [BPA]119889119905= 119896app [BPA] lArrrArr ln [

BPA]119900

[BPA]

= 119896app119905 lArrrArr ln (1 minus 119883) = minus119896app119905(3)

where 119896app is an apparent reaction rate constant and119883 is BPAconversion independent of its initial concentration [BPA]

119900

Figure 7(a) confirms that the reaction approaches indeedfirst-order kinetics Plotting the logarithm of normalizedBPA concentration against time results in straight lines (thecoefficient of linear regression of data fitting 1199032 is between993 and 996) with a nearly common slope whichcorresponds to the apparent reaction rate constant this is 15plusmn 1 10minus3minminus1

The effect of initial BPA concentration was also studied at16mgcm2 ZnO the 90min removal was 64plusmn2 irrespectiveof the initial concentration Figure 7(b) shows the respectivefirst-order degradation kinetics fromwhich the apparent rateconstant is computed at 11 plusmn 1 10minus3minminus1 (the coefficientof linear regression of data fitting 1199032 is between 994 and996)

6 International Journal of Photoenergy

002040608

112141618

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0

02

04

06

08

1

12

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(b)

Figure 7 Effect of initial BPA concentration on its degradation in UPW at (a) 1507mgcm2 TiO2and (b) 16mgcm2 ZnO Plot of (3)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

00005

0010015

0020025

003

0 25 50 100

[BPA

][BP

A] 0

0mgL H2O2

25mgL H2O2

50mgL H2O2

100mgL H2O2

H2O2 concentration (mgL)

k(m

inminus1)

Figure 8 Effect of H2O2on the conversion of 100120583gL BPA in

UPW at 16mgcm2 ZnO Inset graph change of 119896app with H2O2

concentration

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

UPW (37mg ZnO)WW (37mg ZnO)UPW (153mg ZnO)

DW (153mg ZnO)WW (153mg ZnO)

[BPA

][BP

A] 0

Figure 9 Effect of water matrix on the conversion of 100120583gL BPAat two ZnO loadings

From the results presented so far it is evident that bothcatalysts exhibit a similar performance for BPA degradationthrough first-order kinetics We decided to expand exper-imentation with ZnO since (a) TiO

2has extensively been

studied in the literature for several environmental applica-tions and (b) ZnO has the potential to achieve improvedphotocatalytic performance as it absorbs over a wide regionof the UV-A spectrum [22] It should be mentioned herethat ZnO is generally more susceptible to photo corrosionandor chemical corrosion (ie leaching) than TiO

2and this

is a point of concern nonetheless our previous studies [13]showed that ZnO was remarkably stable during the photo-catalytic oxidation of slightly alkaline wastewater matrices

34 Effect of Hydrogen Peroxide The addition of oxidizingspecies increases the efficiency of the photocatalytic processbecause H

2O2is an electron acceptor and reacts with the

electrons of the photo-activated surface of the catalyst

H2O2+ eminus 997888rarr ∙OH+OHminus (4)

Thus the addition of peroxide constitutes an extra source ofhydroxyl radicals and increases the photoreactivity of ZnOduring the photocatalytic degradation [23]

According to our findings (Figure 8) increasing hydro-gen peroxide concentration from 0 to 100mgL results inincreased removal for example the 90min conversion is66 78 85 and 92 at 0 25 50 and 100mgL H

2O2

respectively The inset of Figure 8 shows that the respectiveapparent rate constants increase almost linearly with theamount of H

2O2added up to 100mgL

It should be noted here that H2O2was only partly

consumed during the previous photocatalytic runs as con-firmed with the peroxide test strips unfortunately precisedetermination of residual peroxide was not possible with thismethod

35 Effect of Water Matrix Figure 9 clearly shows thatBPA degradation is impeded in complex water matrices

International Journal of Photoenergy 7

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

002040608

1

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

[BPA

][BP

A] 0

50 120583gL BPA100120583gL BPA200120583gL BPA

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 10 Degradation of a mixture of BPA and EE2 in UPW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200 120583gL BPA(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

containing organic and inorganic constituents for instancethe 90min conversion is 93 65 and 41 in UPW DWand WW respectively at 153mg (68mgcm2) ZnO Therespective apparent kinetic constants are computed equal to0342 (1199032 = 0955) 0128 (1199032 = 095) and 0064minminus1(1199032 = 0979) The discrepancy by an order of magnitudebetween kinetics in UPW and WW can be explained takinginto account that (a) the oxidizing agents are competitivelyconsumed in reactions involving the residual organic fractionpresent in treated WW (ie COD = 24mgL) but notin UPW Since this is known to be refractory to biologicalor chemical oxidation [24] and constitutes most of thematrixrsquos total organic content nonselective oxidizing agentswill partly be wasted attacking this fraction (b) hydroxylradicals may be scavenged by bicarbonates and chloridespresent in WW andor DW to form the respective radicalswhose oxidation potential is lower than that of hydroxylradicals [25 26]

The experiments were repeated at a reduced ZnO loadingof 37mg (16mgcm2) In this case the 90min BPA conver-sion is 60 in UPW and decreases to 44 in WW with therespective rate constants being 12 10minus3minminus1 (1199032 = 0994) and6 10minus3minminus1 (1199032 = 0992) the ratio 119896UPW119896ww is 53 and 2at 68 and 16mgcm2 ZnO respectively These results clearlyindicate that the degree of deceleration of the photocatalyticprocess due to the complexity of the water matrix stronglydepends on the catalyst-loading

36 Degradation of EDCsMixture Experiments were carriedout to investigate the possible interactions of BPA with EE2a synthetic hormone typically found in the contraceptivepill and well-known for its interference with the endocrinesystem of living beings [27]

Figure 10(a) shows BPA concentration-time profiles (50ndash200120583gL initial concentration) in UPW and in the presence

of 100120583gL EE2 while Figure 10(b) shows EE2 concentration-time profiles (100 120583gL initial concentration) in UPW and inthe presence of different BPA concentrations in the range 0ndash200120583gL Comparing Figures 7(b) and 10(a) (inset graph) itis deduced that BPA degradation is slightly impeded by thepresence of EE2 especially at 50 and 100 120583gL BPA initialconcentrations On the other hand Figure 10(b) shows anenhancement of EE2 degradation from 79 in the absenceof BPA to 87 945 and 99 in the presence of 50 100and 200120583gL BPA respectively These results are consistentwith our previous work [16] where the photocatalytic EE2degradation was studied in the presence of BPA Possibleexplanations of this observation would involve the following(a) differences in BPA and EE2 chemical structures EE2 hasa longer molecular chain with more complicated structurethan BPA and this could render it more readily susceptible tooxidative attack (b) the simultaneous BPA-EE2 degradationmay create active radicals that would also attack firstly EE2facilitating thus its degradation and (c) EE2 due to its longerandmore complexmolecule chain may act as a shield to BPAmolecule preventing its diffusion to the catalyst surface thusdecreasing its degradability

The experiments were then performed in WW and theresults are shown in Figure 11 The previous phenomenonis far less pronounced in this case and this is possiblydue to the fact that the WW matrix has already had astrong adverse impact (see Section 35) thus masking anyinteractions between BPA and EE2

A kinetic simulation of BPA degradation in the presenceof EE2 was performed for both UPW and WW matricesBased on the experimental data shown in Figures 10(a)and 11(a) BPA degradation seems to follow near first-orderkinetics as its degradation rate does not depend stronglyon its initial concentration The apparent rate constant fordegradation in UPW is 9 plusmn 2 10minus3minminus1 (computed from the

8 International Journal of Photoenergy

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

001020304050607

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

ln(C

0C

)

BPA 50120583gLBPA 100120583gLBPA 200120583gL

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 11 Degradation of a mixture of BPA and EE2 inWW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200120583gL BPA and(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

slope of the straight lines shown in inset Figure 10(a)) anddecreases to 6 plusmn 1 10minus3minminus1 in WW (inset Figure 11(a))

4 Conclusions

Overall the removal of BPAunder simulated solar irradiationand in the presence of either TiO

2or ZnO catalysts immo-

bilized onto glass plates was investigated It was observedthat the amount of catalyst attached onto the glass platecan affect process efficiency which generally increases atincreased catalyst loadings under the conditions tested BPAremoval follows a first-order reaction rate indicating thatthe removal is not practically affected by the initial BPAconcentration in the presence of either TiO

2or ZnO catalyst

At the conditions employed in this study apparent reactionrates increase with (a) increasing H

2O2concentration in a

proportional fashion and (b) decreasing complexity of thewater matrix (ie from wastewater to drinking water toultrapure water) The presence of other EDCs such as EE2spiked in the reactionmixture does not seem to obstruct BPAdegradation

Hence solar photocatalytic treatment using immobilizedTiO2or ZnO photocatalysts can be a promising with

low energy requirements and efficient process to removeendocrine disrupting compounds found at low concentra-tions from aqueous matrices The key advantage of the pro-posed setup is that there is no need for catalyst aftertreatmentand separation in train with the photocatalytic process thusdecreasing the overall cost of a large-scale treatment plant

References

[1] P K Jjemba Pharma-Ecology The Occurrence and Fate ofPharmaceuticals andPersonal Care Products in the EnvironmentJohn Wiley amp Sons Hoboken NJ USA 2008

[2] V Belgiorno L Rizzo D Fatta et al ldquoReview on endocrinedisrupting-emerging compounds in urban wastewater occur-rence and removal by photocatalysis and ultrasonic irradiationforwastewater reuserdquoDesalination vol 215 no 1ndash3 pp 166ndash1762007

[3] C Lindholst S N Pedersen and P Bjerregaard ldquoUptakemetabolism and excretion of bisphenol A in the rainbow trout(Oncorhynchus mykiss)rdquo Aquatic Toxicology vol 55 no 1-2 pp75ndash84 2001

[4] H Barndok M Pelaez C Han et al ldquoPhotocatalytic degra-dation of contaminants of concern with composite NF-TiO

2

films under visible and solar lightrdquo Environmental Science andPollution Research vol 20 no 6 pp 3582ndash3591 2013

[5] V M Daskalaki I Fulgione Z Frontistis L Rizzo and DMantzavinos ldquoSolar light-induced photoelectrocatalytic degra-dation of bisphenol-A on TiO

2ITO film anode and BDD

cathoderdquo Catalysis Today vol 209 pp 74ndash78 2013[6] S D Richardson ldquoWater analysis emerging contaminants and

current issuesrdquo Analytical Chemistry vol 81 no 12 pp 4645ndash4677 2009

[7] C I Kosma D A Lambropoulou and T A Albanis ldquoOccur-rence and removal of PPCPs in municipal and hospital wastew-aters inGreecerdquo Journal ofHazardousMaterials vol 179 no 1ndash3pp 804ndash817 2010

[8] J L Rodrıguez-Gil M Catala S G Alonso et al ldquoHeteroge-neous photo-Fenton treatment for the reduction of pharmaceu-tical contamination in Madrid rivers and ecotoxicological eval-uation by a miniaturized fern spores bioassayrdquo Chemospherevol 80 no 4 pp 381ndash388 2010

[9] G Gatidou E Vassalou and N S Thomaidis ldquoBioconcen-tration of selected endocrine disrupting compounds in theMediterranean musselMytilus galloprovincialisrdquoMarine Pollu-tion Bulletin vol 60 no 11 pp 2111ndash2116 2010

[10] M Gros M Petrovic and D Barcelo ldquoTracing pharmaceuticalresidues of different therapeutic classes in environmental watersby using liquid chromatographyquadrupole-linear ion trapmass spectrometry and automated library searchingrdquoAnalyticalChemistry vol 81 no 3 pp 898ndash912 2009

International Journal of Photoenergy 9

[11] A S Stasinakis G Gatidou D Mamais N S Thomaidis andT D Lekkas ldquoOccurrence and fate of endocrine disrupters inGreek sewage treatment plantsrdquoWater Research vol 42 no 6-7 pp 1796ndash1804 2008

[12] M Auriol Y Filali-Meknassi R D Tyagi C D Adams and RY Surampalli ldquoEndocrine disrupting compounds removal fromwastewater a new challengerdquo Process Biochemistry vol 41 no3 pp 525ndash539 2006

[13] Z Frontistis D Fatta-Kassinos D Mantzavinos and N P Xek-oukoulotakis ldquoPhotocatalytic degradation of 17120572-ethynylestra-diol in environmental samples by ZnO under simulated solarradiationrdquo Journal of Chemical Technology and Biotechnologyvol 87 no 8 pp 1051ndash1058 2012

[14] M A Behnajady N Modirshahla N Daneshvar and MRabbani ldquoPhotocatalytic degradation of CI Acid Red 27 byimmobilized ZnO on glass plates in continuous-moderdquo Journalof Hazardous Materials vol 140 no 1-2 pp 257ndash263 2007

[15] A R Khataee ldquoPhotocatalytic removal of CI Basic Red 46on immobilized TiO

2nanoparticles artificial neural network

modellingrdquo Environmental Technology vol 30 no 11 pp 1155ndash1168 2009

[16] V Κoutantou M Kostadima E Chatzisymeon et al ldquoSolarphotocatalytic decomposition of estrogens over immobilizedzinc oxiderdquo Catalysis Today vol 209 pp 66ndash73 2013

[17] T Nakashima Y Ohko D A Tryk and A Fujishima ldquoDecom-position of endocrine-disrupting chemicals in water by useof TiO

2photocatalysts immobilized on polytetrafluoroethylene

mesh sheetsrdquo Journal of Photochemistry and Photobiology A vol151 no 1ndash3 pp 207ndash212 2002

[18] V M Daskalaki Z Frontistis D Mantzavinos and A Katsaou-nis ldquoSolar light-induced degradation of bisphenol-A with TiO

2

immobilized on Tirdquo Catalysis Today vol 161 no 1 pp 110ndash1142011

[19] J Gunlazuardi andW A Lindu ldquoPhotocatalytic degradation ofpentachlorophenol in aqueous solution employing immobilizedTiO2supported on titanium metalrdquo Journal of Photochemistry

and Photobiology A vol 173 no 1 pp 51ndash55 2005[20] R Wang D Ren S Xia Y Zhang and J Zhao ldquoPhotocatalytic

degradation of Bisphenol A (BPA) using immobilized TiO2and

UV illumination in a horizontal circulating bed photocatalyticreactor (HCBPR)rdquo Journal of Hazardous Materials vol 169 no1ndash3 pp 926ndash932 2009

[21] E S Galbavy K Ram and C Anastasio ldquo2-Nitrobenzaldehydeas a chemical actinometer for solution and ice photochemistryrdquoJournal of Photochemistry and Photobiology A vol 209 no 2-3pp 186ndash192 2010

[22] M A Behnajady N Modirshahla and R Hamzavi ldquoKineticstudy on photocatalytic degradation of CI Acid Yellow 23 byZnOphotocatalystrdquo Journal ofHazardousMaterials vol 133 no1ndash3 pp 226ndash232 2006

[23] F Mendez-Arriaga M I Maldonado J Gimenez S Esplugasand S Malato ldquoAbatement of ibuprofen by solar photocatalysisprocess enhancement and scale uprdquo Catalysis Today vol 144no 1-2 pp 112ndash116 2009

[24] Z Frontistis and D Mantzavinos ldquoSonodegradation of 17120572-ethynylestradiol in environmentally relevant matrices labora-tory-scale kinetic studiesrdquo Ultrasonics Sonochemistry vol 19no 1 pp 77ndash84 2012

[25] L A T Espinoza M Neamtu and F H Frimmel ldquoThe effect ofnitrate Fe(III) and bicarbonate on the degradation of bisphenolA by simulated solar UV-irradiationrdquo Water Research vol 41no 19 pp 4479ndash4487 2007

[26] C Sirtori A Aguera W Gernjak and S Malato ldquoEffect ofwater-matrix composition on trimethoprim solar photodegra-dation kinetics and pathwaysrdquoWater Research vol 44 no 9 pp2735ndash2744 2010

[27] Z Frontistis C Drosou K Tyrovola et al ldquoExperimental andmodeling studies of the degradation of estrogen hormones inaqueous TiO

2suspensions under simulated solar radiationrdquo

Industrial and Engineering Chemistry Research vol 51 no 51pp 16552ndash16563 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

4 International Journal of Photoenergy

813mg TiO2

(a)

1018mg TiO2

(b)

1523mg TiO2

(c)

3392mg TiO2

(d)

Figure 2 SEM images of TiO2immobilized particles on glass plate with increasing amount of catalyst from 813 to 3392mg (361 to

1507mgcm2)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

0mg813mg1018mg

1523mg3392mg

[BPA

][BP

A] 0

Figure 3 Effect of TiO2loading on the conversion of 100 120583gL BPA

in UPW

Figure 6 where the 90min conversion is enhanced from52 to 90 Notably for ZnO loadings between 16 and25mgcm2 BPA degradation remains practically unchangedat about 65

112

200

103110

102

101

002

100

Inte

nsity

(au

)

20 30 40 50 60 70 802120579 Cuk120572

Figure 4 XRD pattern of the ZnO immobilized particles on glassplate

Another interesting finding is that for the same volume ofthe catalyst aqueous suspension (ie from 200120583L to 10mL)the quantity of ZnO attached onto the glass support is 1-2orders of magnitude lower than that of TiO

2 This is due to

the fact that TiO2is known to have more hydroxyl anions

on its surface than ZnO thus enhancing the adhesion of

International Journal of Photoenergy 5

(a) (b)

(c) (d)

Figure 5 SEM images of (a) glass plates (b) glass plates treated with HF solution (c) 37mg fresh ZnO (16mgcm2) immobilized onto theplate and (d) 37mg used ZnO (16mgcm2) immobilized onto the plate

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

12mg37mg41mg

56mg153mg

Figure 6 Effect of ZnO loading on the conversion of 100 120583gL BPAin UPW

powder onto the appropriate substrate Nevertheless thisdoes not seem to affect the catalytic activity of ZnO whichon a catalyst-loading basis is more efficient than TiO

2 for

example a common BPA conversion can be achieved after90min at 18mgcm2 ZnO or 452mgcm2 TiO

2 as can be

observed from Figures 3 and 6

33 Effect of Initial BPA Concentration The effect of initialBPA concentration (50 100 and 200120583gL) on its degradationover 1507mg cm2 TiO

2was investigated and concentration-

time profiles were followed (data not shown) The 90minBPA removal was 77 plusmn 3 irrespective of the initial BPAconcentration thus implying first-order kinetics that is

minus119889 [BPA]119889119905= 119896app [BPA] lArrrArr ln [

BPA]119900

[BPA]

= 119896app119905 lArrrArr ln (1 minus 119883) = minus119896app119905(3)

where 119896app is an apparent reaction rate constant and119883 is BPAconversion independent of its initial concentration [BPA]

119900

Figure 7(a) confirms that the reaction approaches indeedfirst-order kinetics Plotting the logarithm of normalizedBPA concentration against time results in straight lines (thecoefficient of linear regression of data fitting 1199032 is between993 and 996) with a nearly common slope whichcorresponds to the apparent reaction rate constant this is 15plusmn 1 10minus3minminus1

The effect of initial BPA concentration was also studied at16mgcm2 ZnO the 90min removal was 64plusmn2 irrespectiveof the initial concentration Figure 7(b) shows the respectivefirst-order degradation kinetics fromwhich the apparent rateconstant is computed at 11 plusmn 1 10minus3minminus1 (the coefficientof linear regression of data fitting 1199032 is between 994 and996)

6 International Journal of Photoenergy

002040608

112141618

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0

02

04

06

08

1

12

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(b)

Figure 7 Effect of initial BPA concentration on its degradation in UPW at (a) 1507mgcm2 TiO2and (b) 16mgcm2 ZnO Plot of (3)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

00005

0010015

0020025

003

0 25 50 100

[BPA

][BP

A] 0

0mgL H2O2

25mgL H2O2

50mgL H2O2

100mgL H2O2

H2O2 concentration (mgL)

k(m

inminus1)

Figure 8 Effect of H2O2on the conversion of 100120583gL BPA in

UPW at 16mgcm2 ZnO Inset graph change of 119896app with H2O2

concentration

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

UPW (37mg ZnO)WW (37mg ZnO)UPW (153mg ZnO)

DW (153mg ZnO)WW (153mg ZnO)

[BPA

][BP

A] 0

Figure 9 Effect of water matrix on the conversion of 100120583gL BPAat two ZnO loadings

From the results presented so far it is evident that bothcatalysts exhibit a similar performance for BPA degradationthrough first-order kinetics We decided to expand exper-imentation with ZnO since (a) TiO

2has extensively been

studied in the literature for several environmental applica-tions and (b) ZnO has the potential to achieve improvedphotocatalytic performance as it absorbs over a wide regionof the UV-A spectrum [22] It should be mentioned herethat ZnO is generally more susceptible to photo corrosionandor chemical corrosion (ie leaching) than TiO

2and this

is a point of concern nonetheless our previous studies [13]showed that ZnO was remarkably stable during the photo-catalytic oxidation of slightly alkaline wastewater matrices

34 Effect of Hydrogen Peroxide The addition of oxidizingspecies increases the efficiency of the photocatalytic processbecause H

2O2is an electron acceptor and reacts with the

electrons of the photo-activated surface of the catalyst

H2O2+ eminus 997888rarr ∙OH+OHminus (4)

Thus the addition of peroxide constitutes an extra source ofhydroxyl radicals and increases the photoreactivity of ZnOduring the photocatalytic degradation [23]

According to our findings (Figure 8) increasing hydro-gen peroxide concentration from 0 to 100mgL results inincreased removal for example the 90min conversion is66 78 85 and 92 at 0 25 50 and 100mgL H

2O2

respectively The inset of Figure 8 shows that the respectiveapparent rate constants increase almost linearly with theamount of H

2O2added up to 100mgL

It should be noted here that H2O2was only partly

consumed during the previous photocatalytic runs as con-firmed with the peroxide test strips unfortunately precisedetermination of residual peroxide was not possible with thismethod

35 Effect of Water Matrix Figure 9 clearly shows thatBPA degradation is impeded in complex water matrices

International Journal of Photoenergy 7

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

002040608

1

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

[BPA

][BP

A] 0

50 120583gL BPA100120583gL BPA200120583gL BPA

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 10 Degradation of a mixture of BPA and EE2 in UPW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200 120583gL BPA(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

containing organic and inorganic constituents for instancethe 90min conversion is 93 65 and 41 in UPW DWand WW respectively at 153mg (68mgcm2) ZnO Therespective apparent kinetic constants are computed equal to0342 (1199032 = 0955) 0128 (1199032 = 095) and 0064minminus1(1199032 = 0979) The discrepancy by an order of magnitudebetween kinetics in UPW and WW can be explained takinginto account that (a) the oxidizing agents are competitivelyconsumed in reactions involving the residual organic fractionpresent in treated WW (ie COD = 24mgL) but notin UPW Since this is known to be refractory to biologicalor chemical oxidation [24] and constitutes most of thematrixrsquos total organic content nonselective oxidizing agentswill partly be wasted attacking this fraction (b) hydroxylradicals may be scavenged by bicarbonates and chloridespresent in WW andor DW to form the respective radicalswhose oxidation potential is lower than that of hydroxylradicals [25 26]

The experiments were repeated at a reduced ZnO loadingof 37mg (16mgcm2) In this case the 90min BPA conver-sion is 60 in UPW and decreases to 44 in WW with therespective rate constants being 12 10minus3minminus1 (1199032 = 0994) and6 10minus3minminus1 (1199032 = 0992) the ratio 119896UPW119896ww is 53 and 2at 68 and 16mgcm2 ZnO respectively These results clearlyindicate that the degree of deceleration of the photocatalyticprocess due to the complexity of the water matrix stronglydepends on the catalyst-loading

36 Degradation of EDCsMixture Experiments were carriedout to investigate the possible interactions of BPA with EE2a synthetic hormone typically found in the contraceptivepill and well-known for its interference with the endocrinesystem of living beings [27]

Figure 10(a) shows BPA concentration-time profiles (50ndash200120583gL initial concentration) in UPW and in the presence

of 100120583gL EE2 while Figure 10(b) shows EE2 concentration-time profiles (100 120583gL initial concentration) in UPW and inthe presence of different BPA concentrations in the range 0ndash200120583gL Comparing Figures 7(b) and 10(a) (inset graph) itis deduced that BPA degradation is slightly impeded by thepresence of EE2 especially at 50 and 100 120583gL BPA initialconcentrations On the other hand Figure 10(b) shows anenhancement of EE2 degradation from 79 in the absenceof BPA to 87 945 and 99 in the presence of 50 100and 200120583gL BPA respectively These results are consistentwith our previous work [16] where the photocatalytic EE2degradation was studied in the presence of BPA Possibleexplanations of this observation would involve the following(a) differences in BPA and EE2 chemical structures EE2 hasa longer molecular chain with more complicated structurethan BPA and this could render it more readily susceptible tooxidative attack (b) the simultaneous BPA-EE2 degradationmay create active radicals that would also attack firstly EE2facilitating thus its degradation and (c) EE2 due to its longerandmore complexmolecule chain may act as a shield to BPAmolecule preventing its diffusion to the catalyst surface thusdecreasing its degradability

The experiments were then performed in WW and theresults are shown in Figure 11 The previous phenomenonis far less pronounced in this case and this is possiblydue to the fact that the WW matrix has already had astrong adverse impact (see Section 35) thus masking anyinteractions between BPA and EE2

A kinetic simulation of BPA degradation in the presenceof EE2 was performed for both UPW and WW matricesBased on the experimental data shown in Figures 10(a)and 11(a) BPA degradation seems to follow near first-orderkinetics as its degradation rate does not depend stronglyon its initial concentration The apparent rate constant fordegradation in UPW is 9 plusmn 2 10minus3minminus1 (computed from the

8 International Journal of Photoenergy

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

001020304050607

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

ln(C

0C

)

BPA 50120583gLBPA 100120583gLBPA 200120583gL

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 11 Degradation of a mixture of BPA and EE2 inWW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200120583gL BPA and(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

slope of the straight lines shown in inset Figure 10(a)) anddecreases to 6 plusmn 1 10minus3minminus1 in WW (inset Figure 11(a))

4 Conclusions

Overall the removal of BPAunder simulated solar irradiationand in the presence of either TiO

2or ZnO catalysts immo-

bilized onto glass plates was investigated It was observedthat the amount of catalyst attached onto the glass platecan affect process efficiency which generally increases atincreased catalyst loadings under the conditions tested BPAremoval follows a first-order reaction rate indicating thatthe removal is not practically affected by the initial BPAconcentration in the presence of either TiO

2or ZnO catalyst

At the conditions employed in this study apparent reactionrates increase with (a) increasing H

2O2concentration in a

proportional fashion and (b) decreasing complexity of thewater matrix (ie from wastewater to drinking water toultrapure water) The presence of other EDCs such as EE2spiked in the reactionmixture does not seem to obstruct BPAdegradation

Hence solar photocatalytic treatment using immobilizedTiO2or ZnO photocatalysts can be a promising with

low energy requirements and efficient process to removeendocrine disrupting compounds found at low concentra-tions from aqueous matrices The key advantage of the pro-posed setup is that there is no need for catalyst aftertreatmentand separation in train with the photocatalytic process thusdecreasing the overall cost of a large-scale treatment plant

References

[1] P K Jjemba Pharma-Ecology The Occurrence and Fate ofPharmaceuticals andPersonal Care Products in the EnvironmentJohn Wiley amp Sons Hoboken NJ USA 2008

[2] V Belgiorno L Rizzo D Fatta et al ldquoReview on endocrinedisrupting-emerging compounds in urban wastewater occur-rence and removal by photocatalysis and ultrasonic irradiationforwastewater reuserdquoDesalination vol 215 no 1ndash3 pp 166ndash1762007

[3] C Lindholst S N Pedersen and P Bjerregaard ldquoUptakemetabolism and excretion of bisphenol A in the rainbow trout(Oncorhynchus mykiss)rdquo Aquatic Toxicology vol 55 no 1-2 pp75ndash84 2001

[4] H Barndok M Pelaez C Han et al ldquoPhotocatalytic degra-dation of contaminants of concern with composite NF-TiO

2

films under visible and solar lightrdquo Environmental Science andPollution Research vol 20 no 6 pp 3582ndash3591 2013

[5] V M Daskalaki I Fulgione Z Frontistis L Rizzo and DMantzavinos ldquoSolar light-induced photoelectrocatalytic degra-dation of bisphenol-A on TiO

2ITO film anode and BDD

cathoderdquo Catalysis Today vol 209 pp 74ndash78 2013[6] S D Richardson ldquoWater analysis emerging contaminants and

current issuesrdquo Analytical Chemistry vol 81 no 12 pp 4645ndash4677 2009

[7] C I Kosma D A Lambropoulou and T A Albanis ldquoOccur-rence and removal of PPCPs in municipal and hospital wastew-aters inGreecerdquo Journal ofHazardousMaterials vol 179 no 1ndash3pp 804ndash817 2010

[8] J L Rodrıguez-Gil M Catala S G Alonso et al ldquoHeteroge-neous photo-Fenton treatment for the reduction of pharmaceu-tical contamination in Madrid rivers and ecotoxicological eval-uation by a miniaturized fern spores bioassayrdquo Chemospherevol 80 no 4 pp 381ndash388 2010

[9] G Gatidou E Vassalou and N S Thomaidis ldquoBioconcen-tration of selected endocrine disrupting compounds in theMediterranean musselMytilus galloprovincialisrdquoMarine Pollu-tion Bulletin vol 60 no 11 pp 2111ndash2116 2010

[10] M Gros M Petrovic and D Barcelo ldquoTracing pharmaceuticalresidues of different therapeutic classes in environmental watersby using liquid chromatographyquadrupole-linear ion trapmass spectrometry and automated library searchingrdquoAnalyticalChemistry vol 81 no 3 pp 898ndash912 2009

International Journal of Photoenergy 9

[11] A S Stasinakis G Gatidou D Mamais N S Thomaidis andT D Lekkas ldquoOccurrence and fate of endocrine disrupters inGreek sewage treatment plantsrdquoWater Research vol 42 no 6-7 pp 1796ndash1804 2008

[12] M Auriol Y Filali-Meknassi R D Tyagi C D Adams and RY Surampalli ldquoEndocrine disrupting compounds removal fromwastewater a new challengerdquo Process Biochemistry vol 41 no3 pp 525ndash539 2006

[13] Z Frontistis D Fatta-Kassinos D Mantzavinos and N P Xek-oukoulotakis ldquoPhotocatalytic degradation of 17120572-ethynylestra-diol in environmental samples by ZnO under simulated solarradiationrdquo Journal of Chemical Technology and Biotechnologyvol 87 no 8 pp 1051ndash1058 2012

[14] M A Behnajady N Modirshahla N Daneshvar and MRabbani ldquoPhotocatalytic degradation of CI Acid Red 27 byimmobilized ZnO on glass plates in continuous-moderdquo Journalof Hazardous Materials vol 140 no 1-2 pp 257ndash263 2007

[15] A R Khataee ldquoPhotocatalytic removal of CI Basic Red 46on immobilized TiO

2nanoparticles artificial neural network

modellingrdquo Environmental Technology vol 30 no 11 pp 1155ndash1168 2009

[16] V Κoutantou M Kostadima E Chatzisymeon et al ldquoSolarphotocatalytic decomposition of estrogens over immobilizedzinc oxiderdquo Catalysis Today vol 209 pp 66ndash73 2013

[17] T Nakashima Y Ohko D A Tryk and A Fujishima ldquoDecom-position of endocrine-disrupting chemicals in water by useof TiO

2photocatalysts immobilized on polytetrafluoroethylene

mesh sheetsrdquo Journal of Photochemistry and Photobiology A vol151 no 1ndash3 pp 207ndash212 2002

[18] V M Daskalaki Z Frontistis D Mantzavinos and A Katsaou-nis ldquoSolar light-induced degradation of bisphenol-A with TiO

2

immobilized on Tirdquo Catalysis Today vol 161 no 1 pp 110ndash1142011

[19] J Gunlazuardi andW A Lindu ldquoPhotocatalytic degradation ofpentachlorophenol in aqueous solution employing immobilizedTiO2supported on titanium metalrdquo Journal of Photochemistry

and Photobiology A vol 173 no 1 pp 51ndash55 2005[20] R Wang D Ren S Xia Y Zhang and J Zhao ldquoPhotocatalytic

degradation of Bisphenol A (BPA) using immobilized TiO2and

UV illumination in a horizontal circulating bed photocatalyticreactor (HCBPR)rdquo Journal of Hazardous Materials vol 169 no1ndash3 pp 926ndash932 2009

[21] E S Galbavy K Ram and C Anastasio ldquo2-Nitrobenzaldehydeas a chemical actinometer for solution and ice photochemistryrdquoJournal of Photochemistry and Photobiology A vol 209 no 2-3pp 186ndash192 2010

[22] M A Behnajady N Modirshahla and R Hamzavi ldquoKineticstudy on photocatalytic degradation of CI Acid Yellow 23 byZnOphotocatalystrdquo Journal ofHazardousMaterials vol 133 no1ndash3 pp 226ndash232 2006

[23] F Mendez-Arriaga M I Maldonado J Gimenez S Esplugasand S Malato ldquoAbatement of ibuprofen by solar photocatalysisprocess enhancement and scale uprdquo Catalysis Today vol 144no 1-2 pp 112ndash116 2009

[24] Z Frontistis and D Mantzavinos ldquoSonodegradation of 17120572-ethynylestradiol in environmentally relevant matrices labora-tory-scale kinetic studiesrdquo Ultrasonics Sonochemistry vol 19no 1 pp 77ndash84 2012

[25] L A T Espinoza M Neamtu and F H Frimmel ldquoThe effect ofnitrate Fe(III) and bicarbonate on the degradation of bisphenolA by simulated solar UV-irradiationrdquo Water Research vol 41no 19 pp 4479ndash4487 2007

[26] C Sirtori A Aguera W Gernjak and S Malato ldquoEffect ofwater-matrix composition on trimethoprim solar photodegra-dation kinetics and pathwaysrdquoWater Research vol 44 no 9 pp2735ndash2744 2010

[27] Z Frontistis C Drosou K Tyrovola et al ldquoExperimental andmodeling studies of the degradation of estrogen hormones inaqueous TiO

2suspensions under simulated solar radiationrdquo

Industrial and Engineering Chemistry Research vol 51 no 51pp 16552ndash16563 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

International Journal of Photoenergy 5

(a) (b)

(c) (d)

Figure 5 SEM images of (a) glass plates (b) glass plates treated with HF solution (c) 37mg fresh ZnO (16mgcm2) immobilized onto theplate and (d) 37mg used ZnO (16mgcm2) immobilized onto the plate

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

12mg37mg41mg

56mg153mg

Figure 6 Effect of ZnO loading on the conversion of 100 120583gL BPAin UPW

powder onto the appropriate substrate Nevertheless thisdoes not seem to affect the catalytic activity of ZnO whichon a catalyst-loading basis is more efficient than TiO

2 for

example a common BPA conversion can be achieved after90min at 18mgcm2 ZnO or 452mgcm2 TiO

2 as can be

observed from Figures 3 and 6

33 Effect of Initial BPA Concentration The effect of initialBPA concentration (50 100 and 200120583gL) on its degradationover 1507mg cm2 TiO

2was investigated and concentration-

time profiles were followed (data not shown) The 90minBPA removal was 77 plusmn 3 irrespective of the initial BPAconcentration thus implying first-order kinetics that is

minus119889 [BPA]119889119905= 119896app [BPA] lArrrArr ln [

BPA]119900

[BPA]

= 119896app119905 lArrrArr ln (1 minus 119883) = minus119896app119905(3)

where 119896app is an apparent reaction rate constant and119883 is BPAconversion independent of its initial concentration [BPA]

119900

Figure 7(a) confirms that the reaction approaches indeedfirst-order kinetics Plotting the logarithm of normalizedBPA concentration against time results in straight lines (thecoefficient of linear regression of data fitting 1199032 is between993 and 996) with a nearly common slope whichcorresponds to the apparent reaction rate constant this is 15plusmn 1 10minus3minminus1

The effect of initial BPA concentration was also studied at16mgcm2 ZnO the 90min removal was 64plusmn2 irrespectiveof the initial concentration Figure 7(b) shows the respectivefirst-order degradation kinetics fromwhich the apparent rateconstant is computed at 11 plusmn 1 10minus3minminus1 (the coefficientof linear regression of data fitting 1199032 is between 994 and996)

6 International Journal of Photoenergy

002040608

112141618

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0

02

04

06

08

1

12

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(b)

Figure 7 Effect of initial BPA concentration on its degradation in UPW at (a) 1507mgcm2 TiO2and (b) 16mgcm2 ZnO Plot of (3)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

00005

0010015

0020025

003

0 25 50 100

[BPA

][BP

A] 0

0mgL H2O2

25mgL H2O2

50mgL H2O2

100mgL H2O2

H2O2 concentration (mgL)

k(m

inminus1)

Figure 8 Effect of H2O2on the conversion of 100120583gL BPA in

UPW at 16mgcm2 ZnO Inset graph change of 119896app with H2O2

concentration

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

UPW (37mg ZnO)WW (37mg ZnO)UPW (153mg ZnO)

DW (153mg ZnO)WW (153mg ZnO)

[BPA

][BP

A] 0

Figure 9 Effect of water matrix on the conversion of 100120583gL BPAat two ZnO loadings

From the results presented so far it is evident that bothcatalysts exhibit a similar performance for BPA degradationthrough first-order kinetics We decided to expand exper-imentation with ZnO since (a) TiO

2has extensively been

studied in the literature for several environmental applica-tions and (b) ZnO has the potential to achieve improvedphotocatalytic performance as it absorbs over a wide regionof the UV-A spectrum [22] It should be mentioned herethat ZnO is generally more susceptible to photo corrosionandor chemical corrosion (ie leaching) than TiO

2and this

is a point of concern nonetheless our previous studies [13]showed that ZnO was remarkably stable during the photo-catalytic oxidation of slightly alkaline wastewater matrices

34 Effect of Hydrogen Peroxide The addition of oxidizingspecies increases the efficiency of the photocatalytic processbecause H

2O2is an electron acceptor and reacts with the

electrons of the photo-activated surface of the catalyst

H2O2+ eminus 997888rarr ∙OH+OHminus (4)

Thus the addition of peroxide constitutes an extra source ofhydroxyl radicals and increases the photoreactivity of ZnOduring the photocatalytic degradation [23]

According to our findings (Figure 8) increasing hydro-gen peroxide concentration from 0 to 100mgL results inincreased removal for example the 90min conversion is66 78 85 and 92 at 0 25 50 and 100mgL H

2O2

respectively The inset of Figure 8 shows that the respectiveapparent rate constants increase almost linearly with theamount of H

2O2added up to 100mgL

It should be noted here that H2O2was only partly

consumed during the previous photocatalytic runs as con-firmed with the peroxide test strips unfortunately precisedetermination of residual peroxide was not possible with thismethod

35 Effect of Water Matrix Figure 9 clearly shows thatBPA degradation is impeded in complex water matrices

International Journal of Photoenergy 7

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

002040608

1

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

[BPA

][BP

A] 0

50 120583gL BPA100120583gL BPA200120583gL BPA

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 10 Degradation of a mixture of BPA and EE2 in UPW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200 120583gL BPA(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

containing organic and inorganic constituents for instancethe 90min conversion is 93 65 and 41 in UPW DWand WW respectively at 153mg (68mgcm2) ZnO Therespective apparent kinetic constants are computed equal to0342 (1199032 = 0955) 0128 (1199032 = 095) and 0064minminus1(1199032 = 0979) The discrepancy by an order of magnitudebetween kinetics in UPW and WW can be explained takinginto account that (a) the oxidizing agents are competitivelyconsumed in reactions involving the residual organic fractionpresent in treated WW (ie COD = 24mgL) but notin UPW Since this is known to be refractory to biologicalor chemical oxidation [24] and constitutes most of thematrixrsquos total organic content nonselective oxidizing agentswill partly be wasted attacking this fraction (b) hydroxylradicals may be scavenged by bicarbonates and chloridespresent in WW andor DW to form the respective radicalswhose oxidation potential is lower than that of hydroxylradicals [25 26]

The experiments were repeated at a reduced ZnO loadingof 37mg (16mgcm2) In this case the 90min BPA conver-sion is 60 in UPW and decreases to 44 in WW with therespective rate constants being 12 10minus3minminus1 (1199032 = 0994) and6 10minus3minminus1 (1199032 = 0992) the ratio 119896UPW119896ww is 53 and 2at 68 and 16mgcm2 ZnO respectively These results clearlyindicate that the degree of deceleration of the photocatalyticprocess due to the complexity of the water matrix stronglydepends on the catalyst-loading

36 Degradation of EDCsMixture Experiments were carriedout to investigate the possible interactions of BPA with EE2a synthetic hormone typically found in the contraceptivepill and well-known for its interference with the endocrinesystem of living beings [27]

Figure 10(a) shows BPA concentration-time profiles (50ndash200120583gL initial concentration) in UPW and in the presence

of 100120583gL EE2 while Figure 10(b) shows EE2 concentration-time profiles (100 120583gL initial concentration) in UPW and inthe presence of different BPA concentrations in the range 0ndash200120583gL Comparing Figures 7(b) and 10(a) (inset graph) itis deduced that BPA degradation is slightly impeded by thepresence of EE2 especially at 50 and 100 120583gL BPA initialconcentrations On the other hand Figure 10(b) shows anenhancement of EE2 degradation from 79 in the absenceof BPA to 87 945 and 99 in the presence of 50 100and 200120583gL BPA respectively These results are consistentwith our previous work [16] where the photocatalytic EE2degradation was studied in the presence of BPA Possibleexplanations of this observation would involve the following(a) differences in BPA and EE2 chemical structures EE2 hasa longer molecular chain with more complicated structurethan BPA and this could render it more readily susceptible tooxidative attack (b) the simultaneous BPA-EE2 degradationmay create active radicals that would also attack firstly EE2facilitating thus its degradation and (c) EE2 due to its longerandmore complexmolecule chain may act as a shield to BPAmolecule preventing its diffusion to the catalyst surface thusdecreasing its degradability

The experiments were then performed in WW and theresults are shown in Figure 11 The previous phenomenonis far less pronounced in this case and this is possiblydue to the fact that the WW matrix has already had astrong adverse impact (see Section 35) thus masking anyinteractions between BPA and EE2

A kinetic simulation of BPA degradation in the presenceof EE2 was performed for both UPW and WW matricesBased on the experimental data shown in Figures 10(a)and 11(a) BPA degradation seems to follow near first-orderkinetics as its degradation rate does not depend stronglyon its initial concentration The apparent rate constant fordegradation in UPW is 9 plusmn 2 10minus3minminus1 (computed from the

8 International Journal of Photoenergy

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

001020304050607

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

ln(C

0C

)

BPA 50120583gLBPA 100120583gLBPA 200120583gL

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 11 Degradation of a mixture of BPA and EE2 inWW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200120583gL BPA and(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

slope of the straight lines shown in inset Figure 10(a)) anddecreases to 6 plusmn 1 10minus3minminus1 in WW (inset Figure 11(a))

4 Conclusions

Overall the removal of BPAunder simulated solar irradiationand in the presence of either TiO

2or ZnO catalysts immo-

bilized onto glass plates was investigated It was observedthat the amount of catalyst attached onto the glass platecan affect process efficiency which generally increases atincreased catalyst loadings under the conditions tested BPAremoval follows a first-order reaction rate indicating thatthe removal is not practically affected by the initial BPAconcentration in the presence of either TiO

2or ZnO catalyst

At the conditions employed in this study apparent reactionrates increase with (a) increasing H

2O2concentration in a

proportional fashion and (b) decreasing complexity of thewater matrix (ie from wastewater to drinking water toultrapure water) The presence of other EDCs such as EE2spiked in the reactionmixture does not seem to obstruct BPAdegradation

Hence solar photocatalytic treatment using immobilizedTiO2or ZnO photocatalysts can be a promising with

low energy requirements and efficient process to removeendocrine disrupting compounds found at low concentra-tions from aqueous matrices The key advantage of the pro-posed setup is that there is no need for catalyst aftertreatmentand separation in train with the photocatalytic process thusdecreasing the overall cost of a large-scale treatment plant

References

[1] P K Jjemba Pharma-Ecology The Occurrence and Fate ofPharmaceuticals andPersonal Care Products in the EnvironmentJohn Wiley amp Sons Hoboken NJ USA 2008

[2] V Belgiorno L Rizzo D Fatta et al ldquoReview on endocrinedisrupting-emerging compounds in urban wastewater occur-rence and removal by photocatalysis and ultrasonic irradiationforwastewater reuserdquoDesalination vol 215 no 1ndash3 pp 166ndash1762007

[3] C Lindholst S N Pedersen and P Bjerregaard ldquoUptakemetabolism and excretion of bisphenol A in the rainbow trout(Oncorhynchus mykiss)rdquo Aquatic Toxicology vol 55 no 1-2 pp75ndash84 2001

[4] H Barndok M Pelaez C Han et al ldquoPhotocatalytic degra-dation of contaminants of concern with composite NF-TiO

2

films under visible and solar lightrdquo Environmental Science andPollution Research vol 20 no 6 pp 3582ndash3591 2013

[5] V M Daskalaki I Fulgione Z Frontistis L Rizzo and DMantzavinos ldquoSolar light-induced photoelectrocatalytic degra-dation of bisphenol-A on TiO

2ITO film anode and BDD

cathoderdquo Catalysis Today vol 209 pp 74ndash78 2013[6] S D Richardson ldquoWater analysis emerging contaminants and

current issuesrdquo Analytical Chemistry vol 81 no 12 pp 4645ndash4677 2009

[7] C I Kosma D A Lambropoulou and T A Albanis ldquoOccur-rence and removal of PPCPs in municipal and hospital wastew-aters inGreecerdquo Journal ofHazardousMaterials vol 179 no 1ndash3pp 804ndash817 2010

[8] J L Rodrıguez-Gil M Catala S G Alonso et al ldquoHeteroge-neous photo-Fenton treatment for the reduction of pharmaceu-tical contamination in Madrid rivers and ecotoxicological eval-uation by a miniaturized fern spores bioassayrdquo Chemospherevol 80 no 4 pp 381ndash388 2010

[9] G Gatidou E Vassalou and N S Thomaidis ldquoBioconcen-tration of selected endocrine disrupting compounds in theMediterranean musselMytilus galloprovincialisrdquoMarine Pollu-tion Bulletin vol 60 no 11 pp 2111ndash2116 2010

[10] M Gros M Petrovic and D Barcelo ldquoTracing pharmaceuticalresidues of different therapeutic classes in environmental watersby using liquid chromatographyquadrupole-linear ion trapmass spectrometry and automated library searchingrdquoAnalyticalChemistry vol 81 no 3 pp 898ndash912 2009

International Journal of Photoenergy 9

[11] A S Stasinakis G Gatidou D Mamais N S Thomaidis andT D Lekkas ldquoOccurrence and fate of endocrine disrupters inGreek sewage treatment plantsrdquoWater Research vol 42 no 6-7 pp 1796ndash1804 2008

[12] M Auriol Y Filali-Meknassi R D Tyagi C D Adams and RY Surampalli ldquoEndocrine disrupting compounds removal fromwastewater a new challengerdquo Process Biochemistry vol 41 no3 pp 525ndash539 2006

[13] Z Frontistis D Fatta-Kassinos D Mantzavinos and N P Xek-oukoulotakis ldquoPhotocatalytic degradation of 17120572-ethynylestra-diol in environmental samples by ZnO under simulated solarradiationrdquo Journal of Chemical Technology and Biotechnologyvol 87 no 8 pp 1051ndash1058 2012

[14] M A Behnajady N Modirshahla N Daneshvar and MRabbani ldquoPhotocatalytic degradation of CI Acid Red 27 byimmobilized ZnO on glass plates in continuous-moderdquo Journalof Hazardous Materials vol 140 no 1-2 pp 257ndash263 2007

[15] A R Khataee ldquoPhotocatalytic removal of CI Basic Red 46on immobilized TiO

2nanoparticles artificial neural network

modellingrdquo Environmental Technology vol 30 no 11 pp 1155ndash1168 2009

[16] V Κoutantou M Kostadima E Chatzisymeon et al ldquoSolarphotocatalytic decomposition of estrogens over immobilizedzinc oxiderdquo Catalysis Today vol 209 pp 66ndash73 2013

[17] T Nakashima Y Ohko D A Tryk and A Fujishima ldquoDecom-position of endocrine-disrupting chemicals in water by useof TiO

2photocatalysts immobilized on polytetrafluoroethylene

mesh sheetsrdquo Journal of Photochemistry and Photobiology A vol151 no 1ndash3 pp 207ndash212 2002

[18] V M Daskalaki Z Frontistis D Mantzavinos and A Katsaou-nis ldquoSolar light-induced degradation of bisphenol-A with TiO

2

immobilized on Tirdquo Catalysis Today vol 161 no 1 pp 110ndash1142011

[19] J Gunlazuardi andW A Lindu ldquoPhotocatalytic degradation ofpentachlorophenol in aqueous solution employing immobilizedTiO2supported on titanium metalrdquo Journal of Photochemistry

and Photobiology A vol 173 no 1 pp 51ndash55 2005[20] R Wang D Ren S Xia Y Zhang and J Zhao ldquoPhotocatalytic

degradation of Bisphenol A (BPA) using immobilized TiO2and

UV illumination in a horizontal circulating bed photocatalyticreactor (HCBPR)rdquo Journal of Hazardous Materials vol 169 no1ndash3 pp 926ndash932 2009

[21] E S Galbavy K Ram and C Anastasio ldquo2-Nitrobenzaldehydeas a chemical actinometer for solution and ice photochemistryrdquoJournal of Photochemistry and Photobiology A vol 209 no 2-3pp 186ndash192 2010

[22] M A Behnajady N Modirshahla and R Hamzavi ldquoKineticstudy on photocatalytic degradation of CI Acid Yellow 23 byZnOphotocatalystrdquo Journal ofHazardousMaterials vol 133 no1ndash3 pp 226ndash232 2006

[23] F Mendez-Arriaga M I Maldonado J Gimenez S Esplugasand S Malato ldquoAbatement of ibuprofen by solar photocatalysisprocess enhancement and scale uprdquo Catalysis Today vol 144no 1-2 pp 112ndash116 2009

[24] Z Frontistis and D Mantzavinos ldquoSonodegradation of 17120572-ethynylestradiol in environmentally relevant matrices labora-tory-scale kinetic studiesrdquo Ultrasonics Sonochemistry vol 19no 1 pp 77ndash84 2012

[25] L A T Espinoza M Neamtu and F H Frimmel ldquoThe effect ofnitrate Fe(III) and bicarbonate on the degradation of bisphenolA by simulated solar UV-irradiationrdquo Water Research vol 41no 19 pp 4479ndash4487 2007

[26] C Sirtori A Aguera W Gernjak and S Malato ldquoEffect ofwater-matrix composition on trimethoprim solar photodegra-dation kinetics and pathwaysrdquoWater Research vol 44 no 9 pp2735ndash2744 2010

[27] Z Frontistis C Drosou K Tyrovola et al ldquoExperimental andmodeling studies of the degradation of estrogen hormones inaqueous TiO

2suspensions under simulated solar radiationrdquo

Industrial and Engineering Chemistry Research vol 51 no 51pp 16552ndash16563 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

6 International Journal of Photoenergy

002040608

112141618

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0

02

04

06

08

1

12

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

50120583gL BPA100120583gL BPA200120583gL BPA

(b)

Figure 7 Effect of initial BPA concentration on its degradation in UPW at (a) 1507mgcm2 TiO2and (b) 16mgcm2 ZnO Plot of (3)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

00005

0010015

0020025

003

0 25 50 100

[BPA

][BP

A] 0

0mgL H2O2

25mgL H2O2

50mgL H2O2

100mgL H2O2

H2O2 concentration (mgL)

k(m

inminus1)

Figure 8 Effect of H2O2on the conversion of 100120583gL BPA in

UPW at 16mgcm2 ZnO Inset graph change of 119896app with H2O2

concentration

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

UPW (37mg ZnO)WW (37mg ZnO)UPW (153mg ZnO)

DW (153mg ZnO)WW (153mg ZnO)

[BPA

][BP

A] 0

Figure 9 Effect of water matrix on the conversion of 100120583gL BPAat two ZnO loadings

From the results presented so far it is evident that bothcatalysts exhibit a similar performance for BPA degradationthrough first-order kinetics We decided to expand exper-imentation with ZnO since (a) TiO

2has extensively been

studied in the literature for several environmental applica-tions and (b) ZnO has the potential to achieve improvedphotocatalytic performance as it absorbs over a wide regionof the UV-A spectrum [22] It should be mentioned herethat ZnO is generally more susceptible to photo corrosionandor chemical corrosion (ie leaching) than TiO

2and this

is a point of concern nonetheless our previous studies [13]showed that ZnO was remarkably stable during the photo-catalytic oxidation of slightly alkaline wastewater matrices

34 Effect of Hydrogen Peroxide The addition of oxidizingspecies increases the efficiency of the photocatalytic processbecause H

2O2is an electron acceptor and reacts with the

electrons of the photo-activated surface of the catalyst

H2O2+ eminus 997888rarr ∙OH+OHminus (4)

Thus the addition of peroxide constitutes an extra source ofhydroxyl radicals and increases the photoreactivity of ZnOduring the photocatalytic degradation [23]

According to our findings (Figure 8) increasing hydro-gen peroxide concentration from 0 to 100mgL results inincreased removal for example the 90min conversion is66 78 85 and 92 at 0 25 50 and 100mgL H

2O2

respectively The inset of Figure 8 shows that the respectiveapparent rate constants increase almost linearly with theamount of H

2O2added up to 100mgL

It should be noted here that H2O2was only partly

consumed during the previous photocatalytic runs as con-firmed with the peroxide test strips unfortunately precisedetermination of residual peroxide was not possible with thismethod

35 Effect of Water Matrix Figure 9 clearly shows thatBPA degradation is impeded in complex water matrices

International Journal of Photoenergy 7

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

002040608

1

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

[BPA

][BP

A] 0

50 120583gL BPA100120583gL BPA200120583gL BPA

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 10 Degradation of a mixture of BPA and EE2 in UPW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200 120583gL BPA(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

containing organic and inorganic constituents for instancethe 90min conversion is 93 65 and 41 in UPW DWand WW respectively at 153mg (68mgcm2) ZnO Therespective apparent kinetic constants are computed equal to0342 (1199032 = 0955) 0128 (1199032 = 095) and 0064minminus1(1199032 = 0979) The discrepancy by an order of magnitudebetween kinetics in UPW and WW can be explained takinginto account that (a) the oxidizing agents are competitivelyconsumed in reactions involving the residual organic fractionpresent in treated WW (ie COD = 24mgL) but notin UPW Since this is known to be refractory to biologicalor chemical oxidation [24] and constitutes most of thematrixrsquos total organic content nonselective oxidizing agentswill partly be wasted attacking this fraction (b) hydroxylradicals may be scavenged by bicarbonates and chloridespresent in WW andor DW to form the respective radicalswhose oxidation potential is lower than that of hydroxylradicals [25 26]

The experiments were repeated at a reduced ZnO loadingof 37mg (16mgcm2) In this case the 90min BPA conver-sion is 60 in UPW and decreases to 44 in WW with therespective rate constants being 12 10minus3minminus1 (1199032 = 0994) and6 10minus3minminus1 (1199032 = 0992) the ratio 119896UPW119896ww is 53 and 2at 68 and 16mgcm2 ZnO respectively These results clearlyindicate that the degree of deceleration of the photocatalyticprocess due to the complexity of the water matrix stronglydepends on the catalyst-loading

36 Degradation of EDCsMixture Experiments were carriedout to investigate the possible interactions of BPA with EE2a synthetic hormone typically found in the contraceptivepill and well-known for its interference with the endocrinesystem of living beings [27]

Figure 10(a) shows BPA concentration-time profiles (50ndash200120583gL initial concentration) in UPW and in the presence

of 100120583gL EE2 while Figure 10(b) shows EE2 concentration-time profiles (100 120583gL initial concentration) in UPW and inthe presence of different BPA concentrations in the range 0ndash200120583gL Comparing Figures 7(b) and 10(a) (inset graph) itis deduced that BPA degradation is slightly impeded by thepresence of EE2 especially at 50 and 100 120583gL BPA initialconcentrations On the other hand Figure 10(b) shows anenhancement of EE2 degradation from 79 in the absenceof BPA to 87 945 and 99 in the presence of 50 100and 200120583gL BPA respectively These results are consistentwith our previous work [16] where the photocatalytic EE2degradation was studied in the presence of BPA Possibleexplanations of this observation would involve the following(a) differences in BPA and EE2 chemical structures EE2 hasa longer molecular chain with more complicated structurethan BPA and this could render it more readily susceptible tooxidative attack (b) the simultaneous BPA-EE2 degradationmay create active radicals that would also attack firstly EE2facilitating thus its degradation and (c) EE2 due to its longerandmore complexmolecule chain may act as a shield to BPAmolecule preventing its diffusion to the catalyst surface thusdecreasing its degradability

The experiments were then performed in WW and theresults are shown in Figure 11 The previous phenomenonis far less pronounced in this case and this is possiblydue to the fact that the WW matrix has already had astrong adverse impact (see Section 35) thus masking anyinteractions between BPA and EE2

A kinetic simulation of BPA degradation in the presenceof EE2 was performed for both UPW and WW matricesBased on the experimental data shown in Figures 10(a)and 11(a) BPA degradation seems to follow near first-orderkinetics as its degradation rate does not depend stronglyon its initial concentration The apparent rate constant fordegradation in UPW is 9 plusmn 2 10minus3minminus1 (computed from the

8 International Journal of Photoenergy

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

001020304050607

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

ln(C

0C

)

BPA 50120583gLBPA 100120583gLBPA 200120583gL

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 11 Degradation of a mixture of BPA and EE2 inWW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200120583gL BPA and(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

slope of the straight lines shown in inset Figure 10(a)) anddecreases to 6 plusmn 1 10minus3minminus1 in WW (inset Figure 11(a))

4 Conclusions

Overall the removal of BPAunder simulated solar irradiationand in the presence of either TiO

2or ZnO catalysts immo-

bilized onto glass plates was investigated It was observedthat the amount of catalyst attached onto the glass platecan affect process efficiency which generally increases atincreased catalyst loadings under the conditions tested BPAremoval follows a first-order reaction rate indicating thatthe removal is not practically affected by the initial BPAconcentration in the presence of either TiO

2or ZnO catalyst

At the conditions employed in this study apparent reactionrates increase with (a) increasing H

2O2concentration in a

proportional fashion and (b) decreasing complexity of thewater matrix (ie from wastewater to drinking water toultrapure water) The presence of other EDCs such as EE2spiked in the reactionmixture does not seem to obstruct BPAdegradation

Hence solar photocatalytic treatment using immobilizedTiO2or ZnO photocatalysts can be a promising with

low energy requirements and efficient process to removeendocrine disrupting compounds found at low concentra-tions from aqueous matrices The key advantage of the pro-posed setup is that there is no need for catalyst aftertreatmentand separation in train with the photocatalytic process thusdecreasing the overall cost of a large-scale treatment plant

References

[1] P K Jjemba Pharma-Ecology The Occurrence and Fate ofPharmaceuticals andPersonal Care Products in the EnvironmentJohn Wiley amp Sons Hoboken NJ USA 2008

[2] V Belgiorno L Rizzo D Fatta et al ldquoReview on endocrinedisrupting-emerging compounds in urban wastewater occur-rence and removal by photocatalysis and ultrasonic irradiationforwastewater reuserdquoDesalination vol 215 no 1ndash3 pp 166ndash1762007

[3] C Lindholst S N Pedersen and P Bjerregaard ldquoUptakemetabolism and excretion of bisphenol A in the rainbow trout(Oncorhynchus mykiss)rdquo Aquatic Toxicology vol 55 no 1-2 pp75ndash84 2001

[4] H Barndok M Pelaez C Han et al ldquoPhotocatalytic degra-dation of contaminants of concern with composite NF-TiO

2

films under visible and solar lightrdquo Environmental Science andPollution Research vol 20 no 6 pp 3582ndash3591 2013

[5] V M Daskalaki I Fulgione Z Frontistis L Rizzo and DMantzavinos ldquoSolar light-induced photoelectrocatalytic degra-dation of bisphenol-A on TiO

2ITO film anode and BDD

cathoderdquo Catalysis Today vol 209 pp 74ndash78 2013[6] S D Richardson ldquoWater analysis emerging contaminants and

current issuesrdquo Analytical Chemistry vol 81 no 12 pp 4645ndash4677 2009

[7] C I Kosma D A Lambropoulou and T A Albanis ldquoOccur-rence and removal of PPCPs in municipal and hospital wastew-aters inGreecerdquo Journal ofHazardousMaterials vol 179 no 1ndash3pp 804ndash817 2010

[8] J L Rodrıguez-Gil M Catala S G Alonso et al ldquoHeteroge-neous photo-Fenton treatment for the reduction of pharmaceu-tical contamination in Madrid rivers and ecotoxicological eval-uation by a miniaturized fern spores bioassayrdquo Chemospherevol 80 no 4 pp 381ndash388 2010

[9] G Gatidou E Vassalou and N S Thomaidis ldquoBioconcen-tration of selected endocrine disrupting compounds in theMediterranean musselMytilus galloprovincialisrdquoMarine Pollu-tion Bulletin vol 60 no 11 pp 2111ndash2116 2010

[10] M Gros M Petrovic and D Barcelo ldquoTracing pharmaceuticalresidues of different therapeutic classes in environmental watersby using liquid chromatographyquadrupole-linear ion trapmass spectrometry and automated library searchingrdquoAnalyticalChemistry vol 81 no 3 pp 898ndash912 2009

International Journal of Photoenergy 9

[11] A S Stasinakis G Gatidou D Mamais N S Thomaidis andT D Lekkas ldquoOccurrence and fate of endocrine disrupters inGreek sewage treatment plantsrdquoWater Research vol 42 no 6-7 pp 1796ndash1804 2008

[12] M Auriol Y Filali-Meknassi R D Tyagi C D Adams and RY Surampalli ldquoEndocrine disrupting compounds removal fromwastewater a new challengerdquo Process Biochemistry vol 41 no3 pp 525ndash539 2006

[13] Z Frontistis D Fatta-Kassinos D Mantzavinos and N P Xek-oukoulotakis ldquoPhotocatalytic degradation of 17120572-ethynylestra-diol in environmental samples by ZnO under simulated solarradiationrdquo Journal of Chemical Technology and Biotechnologyvol 87 no 8 pp 1051ndash1058 2012

[14] M A Behnajady N Modirshahla N Daneshvar and MRabbani ldquoPhotocatalytic degradation of CI Acid Red 27 byimmobilized ZnO on glass plates in continuous-moderdquo Journalof Hazardous Materials vol 140 no 1-2 pp 257ndash263 2007

[15] A R Khataee ldquoPhotocatalytic removal of CI Basic Red 46on immobilized TiO

2nanoparticles artificial neural network

modellingrdquo Environmental Technology vol 30 no 11 pp 1155ndash1168 2009

[16] V Κoutantou M Kostadima E Chatzisymeon et al ldquoSolarphotocatalytic decomposition of estrogens over immobilizedzinc oxiderdquo Catalysis Today vol 209 pp 66ndash73 2013

[17] T Nakashima Y Ohko D A Tryk and A Fujishima ldquoDecom-position of endocrine-disrupting chemicals in water by useof TiO

2photocatalysts immobilized on polytetrafluoroethylene

mesh sheetsrdquo Journal of Photochemistry and Photobiology A vol151 no 1ndash3 pp 207ndash212 2002

[18] V M Daskalaki Z Frontistis D Mantzavinos and A Katsaou-nis ldquoSolar light-induced degradation of bisphenol-A with TiO

2

immobilized on Tirdquo Catalysis Today vol 161 no 1 pp 110ndash1142011

[19] J Gunlazuardi andW A Lindu ldquoPhotocatalytic degradation ofpentachlorophenol in aqueous solution employing immobilizedTiO2supported on titanium metalrdquo Journal of Photochemistry

and Photobiology A vol 173 no 1 pp 51ndash55 2005[20] R Wang D Ren S Xia Y Zhang and J Zhao ldquoPhotocatalytic

degradation of Bisphenol A (BPA) using immobilized TiO2and

UV illumination in a horizontal circulating bed photocatalyticreactor (HCBPR)rdquo Journal of Hazardous Materials vol 169 no1ndash3 pp 926ndash932 2009

[21] E S Galbavy K Ram and C Anastasio ldquo2-Nitrobenzaldehydeas a chemical actinometer for solution and ice photochemistryrdquoJournal of Photochemistry and Photobiology A vol 209 no 2-3pp 186ndash192 2010

[22] M A Behnajady N Modirshahla and R Hamzavi ldquoKineticstudy on photocatalytic degradation of CI Acid Yellow 23 byZnOphotocatalystrdquo Journal ofHazardousMaterials vol 133 no1ndash3 pp 226ndash232 2006

[23] F Mendez-Arriaga M I Maldonado J Gimenez S Esplugasand S Malato ldquoAbatement of ibuprofen by solar photocatalysisprocess enhancement and scale uprdquo Catalysis Today vol 144no 1-2 pp 112ndash116 2009

[24] Z Frontistis and D Mantzavinos ldquoSonodegradation of 17120572-ethynylestradiol in environmentally relevant matrices labora-tory-scale kinetic studiesrdquo Ultrasonics Sonochemistry vol 19no 1 pp 77ndash84 2012

[25] L A T Espinoza M Neamtu and F H Frimmel ldquoThe effect ofnitrate Fe(III) and bicarbonate on the degradation of bisphenolA by simulated solar UV-irradiationrdquo Water Research vol 41no 19 pp 4479ndash4487 2007

[26] C Sirtori A Aguera W Gernjak and S Malato ldquoEffect ofwater-matrix composition on trimethoprim solar photodegra-dation kinetics and pathwaysrdquoWater Research vol 44 no 9 pp2735ndash2744 2010

[27] Z Frontistis C Drosou K Tyrovola et al ldquoExperimental andmodeling studies of the degradation of estrogen hormones inaqueous TiO

2suspensions under simulated solar radiationrdquo

Industrial and Engineering Chemistry Research vol 51 no 51pp 16552ndash16563 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

International Journal of Photoenergy 7

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

002040608

1

0 10 20 30 40 50 60 70 80 90Time (min)

ln(C

0C

)

[BPA

][BP

A] 0

50 120583gL BPA100120583gL BPA200120583gL BPA

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 10 Degradation of a mixture of BPA and EE2 in UPW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200 120583gL BPA(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

containing organic and inorganic constituents for instancethe 90min conversion is 93 65 and 41 in UPW DWand WW respectively at 153mg (68mgcm2) ZnO Therespective apparent kinetic constants are computed equal to0342 (1199032 = 0955) 0128 (1199032 = 095) and 0064minminus1(1199032 = 0979) The discrepancy by an order of magnitudebetween kinetics in UPW and WW can be explained takinginto account that (a) the oxidizing agents are competitivelyconsumed in reactions involving the residual organic fractionpresent in treated WW (ie COD = 24mgL) but notin UPW Since this is known to be refractory to biologicalor chemical oxidation [24] and constitutes most of thematrixrsquos total organic content nonselective oxidizing agentswill partly be wasted attacking this fraction (b) hydroxylradicals may be scavenged by bicarbonates and chloridespresent in WW andor DW to form the respective radicalswhose oxidation potential is lower than that of hydroxylradicals [25 26]

The experiments were repeated at a reduced ZnO loadingof 37mg (16mgcm2) In this case the 90min BPA conver-sion is 60 in UPW and decreases to 44 in WW with therespective rate constants being 12 10minus3minminus1 (1199032 = 0994) and6 10minus3minminus1 (1199032 = 0992) the ratio 119896UPW119896ww is 53 and 2at 68 and 16mgcm2 ZnO respectively These results clearlyindicate that the degree of deceleration of the photocatalyticprocess due to the complexity of the water matrix stronglydepends on the catalyst-loading

36 Degradation of EDCsMixture Experiments were carriedout to investigate the possible interactions of BPA with EE2a synthetic hormone typically found in the contraceptivepill and well-known for its interference with the endocrinesystem of living beings [27]

Figure 10(a) shows BPA concentration-time profiles (50ndash200120583gL initial concentration) in UPW and in the presence

of 100120583gL EE2 while Figure 10(b) shows EE2 concentration-time profiles (100 120583gL initial concentration) in UPW and inthe presence of different BPA concentrations in the range 0ndash200120583gL Comparing Figures 7(b) and 10(a) (inset graph) itis deduced that BPA degradation is slightly impeded by thepresence of EE2 especially at 50 and 100 120583gL BPA initialconcentrations On the other hand Figure 10(b) shows anenhancement of EE2 degradation from 79 in the absenceof BPA to 87 945 and 99 in the presence of 50 100and 200120583gL BPA respectively These results are consistentwith our previous work [16] where the photocatalytic EE2degradation was studied in the presence of BPA Possibleexplanations of this observation would involve the following(a) differences in BPA and EE2 chemical structures EE2 hasa longer molecular chain with more complicated structurethan BPA and this could render it more readily susceptible tooxidative attack (b) the simultaneous BPA-EE2 degradationmay create active radicals that would also attack firstly EE2facilitating thus its degradation and (c) EE2 due to its longerandmore complexmolecule chain may act as a shield to BPAmolecule preventing its diffusion to the catalyst surface thusdecreasing its degradability

The experiments were then performed in WW and theresults are shown in Figure 11 The previous phenomenonis far less pronounced in this case and this is possiblydue to the fact that the WW matrix has already had astrong adverse impact (see Section 35) thus masking anyinteractions between BPA and EE2

A kinetic simulation of BPA degradation in the presenceof EE2 was performed for both UPW and WW matricesBased on the experimental data shown in Figures 10(a)and 11(a) BPA degradation seems to follow near first-orderkinetics as its degradation rate does not depend stronglyon its initial concentration The apparent rate constant fordegradation in UPW is 9 plusmn 2 10minus3minminus1 (computed from the

8 International Journal of Photoenergy

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

001020304050607

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

ln(C

0C

)

BPA 50120583gLBPA 100120583gLBPA 200120583gL

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 11 Degradation of a mixture of BPA and EE2 inWW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200120583gL BPA and(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

slope of the straight lines shown in inset Figure 10(a)) anddecreases to 6 plusmn 1 10minus3minminus1 in WW (inset Figure 11(a))

4 Conclusions

Overall the removal of BPAunder simulated solar irradiationand in the presence of either TiO

2or ZnO catalysts immo-

bilized onto glass plates was investigated It was observedthat the amount of catalyst attached onto the glass platecan affect process efficiency which generally increases atincreased catalyst loadings under the conditions tested BPAremoval follows a first-order reaction rate indicating thatthe removal is not practically affected by the initial BPAconcentration in the presence of either TiO

2or ZnO catalyst

At the conditions employed in this study apparent reactionrates increase with (a) increasing H

2O2concentration in a

proportional fashion and (b) decreasing complexity of thewater matrix (ie from wastewater to drinking water toultrapure water) The presence of other EDCs such as EE2spiked in the reactionmixture does not seem to obstruct BPAdegradation

Hence solar photocatalytic treatment using immobilizedTiO2or ZnO photocatalysts can be a promising with

low energy requirements and efficient process to removeendocrine disrupting compounds found at low concentra-tions from aqueous matrices The key advantage of the pro-posed setup is that there is no need for catalyst aftertreatmentand separation in train with the photocatalytic process thusdecreasing the overall cost of a large-scale treatment plant

References

[1] P K Jjemba Pharma-Ecology The Occurrence and Fate ofPharmaceuticals andPersonal Care Products in the EnvironmentJohn Wiley amp Sons Hoboken NJ USA 2008

[2] V Belgiorno L Rizzo D Fatta et al ldquoReview on endocrinedisrupting-emerging compounds in urban wastewater occur-rence and removal by photocatalysis and ultrasonic irradiationforwastewater reuserdquoDesalination vol 215 no 1ndash3 pp 166ndash1762007

[3] C Lindholst S N Pedersen and P Bjerregaard ldquoUptakemetabolism and excretion of bisphenol A in the rainbow trout(Oncorhynchus mykiss)rdquo Aquatic Toxicology vol 55 no 1-2 pp75ndash84 2001

[4] H Barndok M Pelaez C Han et al ldquoPhotocatalytic degra-dation of contaminants of concern with composite NF-TiO

2

films under visible and solar lightrdquo Environmental Science andPollution Research vol 20 no 6 pp 3582ndash3591 2013

[5] V M Daskalaki I Fulgione Z Frontistis L Rizzo and DMantzavinos ldquoSolar light-induced photoelectrocatalytic degra-dation of bisphenol-A on TiO

2ITO film anode and BDD

cathoderdquo Catalysis Today vol 209 pp 74ndash78 2013[6] S D Richardson ldquoWater analysis emerging contaminants and

current issuesrdquo Analytical Chemistry vol 81 no 12 pp 4645ndash4677 2009

[7] C I Kosma D A Lambropoulou and T A Albanis ldquoOccur-rence and removal of PPCPs in municipal and hospital wastew-aters inGreecerdquo Journal ofHazardousMaterials vol 179 no 1ndash3pp 804ndash817 2010

[8] J L Rodrıguez-Gil M Catala S G Alonso et al ldquoHeteroge-neous photo-Fenton treatment for the reduction of pharmaceu-tical contamination in Madrid rivers and ecotoxicological eval-uation by a miniaturized fern spores bioassayrdquo Chemospherevol 80 no 4 pp 381ndash388 2010

[9] G Gatidou E Vassalou and N S Thomaidis ldquoBioconcen-tration of selected endocrine disrupting compounds in theMediterranean musselMytilus galloprovincialisrdquoMarine Pollu-tion Bulletin vol 60 no 11 pp 2111ndash2116 2010

[10] M Gros M Petrovic and D Barcelo ldquoTracing pharmaceuticalresidues of different therapeutic classes in environmental watersby using liquid chromatographyquadrupole-linear ion trapmass spectrometry and automated library searchingrdquoAnalyticalChemistry vol 81 no 3 pp 898ndash912 2009

International Journal of Photoenergy 9

[11] A S Stasinakis G Gatidou D Mamais N S Thomaidis andT D Lekkas ldquoOccurrence and fate of endocrine disrupters inGreek sewage treatment plantsrdquoWater Research vol 42 no 6-7 pp 1796ndash1804 2008

[12] M Auriol Y Filali-Meknassi R D Tyagi C D Adams and RY Surampalli ldquoEndocrine disrupting compounds removal fromwastewater a new challengerdquo Process Biochemistry vol 41 no3 pp 525ndash539 2006

[13] Z Frontistis D Fatta-Kassinos D Mantzavinos and N P Xek-oukoulotakis ldquoPhotocatalytic degradation of 17120572-ethynylestra-diol in environmental samples by ZnO under simulated solarradiationrdquo Journal of Chemical Technology and Biotechnologyvol 87 no 8 pp 1051ndash1058 2012

[14] M A Behnajady N Modirshahla N Daneshvar and MRabbani ldquoPhotocatalytic degradation of CI Acid Red 27 byimmobilized ZnO on glass plates in continuous-moderdquo Journalof Hazardous Materials vol 140 no 1-2 pp 257ndash263 2007

[15] A R Khataee ldquoPhotocatalytic removal of CI Basic Red 46on immobilized TiO

2nanoparticles artificial neural network

modellingrdquo Environmental Technology vol 30 no 11 pp 1155ndash1168 2009

[16] V Κoutantou M Kostadima E Chatzisymeon et al ldquoSolarphotocatalytic decomposition of estrogens over immobilizedzinc oxiderdquo Catalysis Today vol 209 pp 66ndash73 2013

[17] T Nakashima Y Ohko D A Tryk and A Fujishima ldquoDecom-position of endocrine-disrupting chemicals in water by useof TiO

2photocatalysts immobilized on polytetrafluoroethylene

mesh sheetsrdquo Journal of Photochemistry and Photobiology A vol151 no 1ndash3 pp 207ndash212 2002

[18] V M Daskalaki Z Frontistis D Mantzavinos and A Katsaou-nis ldquoSolar light-induced degradation of bisphenol-A with TiO

2

immobilized on Tirdquo Catalysis Today vol 161 no 1 pp 110ndash1142011

[19] J Gunlazuardi andW A Lindu ldquoPhotocatalytic degradation ofpentachlorophenol in aqueous solution employing immobilizedTiO2supported on titanium metalrdquo Journal of Photochemistry

and Photobiology A vol 173 no 1 pp 51ndash55 2005[20] R Wang D Ren S Xia Y Zhang and J Zhao ldquoPhotocatalytic

degradation of Bisphenol A (BPA) using immobilized TiO2and

UV illumination in a horizontal circulating bed photocatalyticreactor (HCBPR)rdquo Journal of Hazardous Materials vol 169 no1ndash3 pp 926ndash932 2009

[21] E S Galbavy K Ram and C Anastasio ldquo2-Nitrobenzaldehydeas a chemical actinometer for solution and ice photochemistryrdquoJournal of Photochemistry and Photobiology A vol 209 no 2-3pp 186ndash192 2010

[22] M A Behnajady N Modirshahla and R Hamzavi ldquoKineticstudy on photocatalytic degradation of CI Acid Yellow 23 byZnOphotocatalystrdquo Journal ofHazardousMaterials vol 133 no1ndash3 pp 226ndash232 2006

[23] F Mendez-Arriaga M I Maldonado J Gimenez S Esplugasand S Malato ldquoAbatement of ibuprofen by solar photocatalysisprocess enhancement and scale uprdquo Catalysis Today vol 144no 1-2 pp 112ndash116 2009

[24] Z Frontistis and D Mantzavinos ldquoSonodegradation of 17120572-ethynylestradiol in environmentally relevant matrices labora-tory-scale kinetic studiesrdquo Ultrasonics Sonochemistry vol 19no 1 pp 77ndash84 2012

[25] L A T Espinoza M Neamtu and F H Frimmel ldquoThe effect ofnitrate Fe(III) and bicarbonate on the degradation of bisphenolA by simulated solar UV-irradiationrdquo Water Research vol 41no 19 pp 4479ndash4487 2007

[26] C Sirtori A Aguera W Gernjak and S Malato ldquoEffect ofwater-matrix composition on trimethoprim solar photodegra-dation kinetics and pathwaysrdquoWater Research vol 44 no 9 pp2735ndash2744 2010

[27] Z Frontistis C Drosou K Tyrovola et al ldquoExperimental andmodeling studies of the degradation of estrogen hormones inaqueous TiO

2suspensions under simulated solar radiationrdquo

Industrial and Engineering Chemistry Research vol 51 no 51pp 16552ndash16563 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

8 International Journal of Photoenergy

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

001020304050607

0 10 20 30 40 50 60 70 80 90Time (min)

[BPA

][BP

A] 0

ln(C

0C

)

BPA 50120583gLBPA 100120583gLBPA 200120583gL

50120583gL BPA100120583gL BPA200120583gL BPA

(a)

0010203040506070809

1

0 10 20 30 40 50 60 70 80 90Time (min)

[EE2

][E

E2] 0

50 120583gL BPA100120583gL BPA

200120583gL BPAAbsence of BPA

(b)

Figure 11 Degradation of a mixture of BPA and EE2 inWW at 16mgcm2 ZnO Effect of (a) 100120583gL EE2 on 50 100 and 200120583gL BPA and(b) 50 100 and 200 120583gL BPA on 100 120583gL EE2 Inset graph plot of (3)

slope of the straight lines shown in inset Figure 10(a)) anddecreases to 6 plusmn 1 10minus3minminus1 in WW (inset Figure 11(a))

4 Conclusions

Overall the removal of BPAunder simulated solar irradiationand in the presence of either TiO

2or ZnO catalysts immo-

bilized onto glass plates was investigated It was observedthat the amount of catalyst attached onto the glass platecan affect process efficiency which generally increases atincreased catalyst loadings under the conditions tested BPAremoval follows a first-order reaction rate indicating thatthe removal is not practically affected by the initial BPAconcentration in the presence of either TiO

2or ZnO catalyst

At the conditions employed in this study apparent reactionrates increase with (a) increasing H

2O2concentration in a

proportional fashion and (b) decreasing complexity of thewater matrix (ie from wastewater to drinking water toultrapure water) The presence of other EDCs such as EE2spiked in the reactionmixture does not seem to obstruct BPAdegradation

Hence solar photocatalytic treatment using immobilizedTiO2or ZnO photocatalysts can be a promising with

low energy requirements and efficient process to removeendocrine disrupting compounds found at low concentra-tions from aqueous matrices The key advantage of the pro-posed setup is that there is no need for catalyst aftertreatmentand separation in train with the photocatalytic process thusdecreasing the overall cost of a large-scale treatment plant

References

[1] P K Jjemba Pharma-Ecology The Occurrence and Fate ofPharmaceuticals andPersonal Care Products in the EnvironmentJohn Wiley amp Sons Hoboken NJ USA 2008

[2] V Belgiorno L Rizzo D Fatta et al ldquoReview on endocrinedisrupting-emerging compounds in urban wastewater occur-rence and removal by photocatalysis and ultrasonic irradiationforwastewater reuserdquoDesalination vol 215 no 1ndash3 pp 166ndash1762007

[3] C Lindholst S N Pedersen and P Bjerregaard ldquoUptakemetabolism and excretion of bisphenol A in the rainbow trout(Oncorhynchus mykiss)rdquo Aquatic Toxicology vol 55 no 1-2 pp75ndash84 2001

[4] H Barndok M Pelaez C Han et al ldquoPhotocatalytic degra-dation of contaminants of concern with composite NF-TiO

2

films under visible and solar lightrdquo Environmental Science andPollution Research vol 20 no 6 pp 3582ndash3591 2013

[5] V M Daskalaki I Fulgione Z Frontistis L Rizzo and DMantzavinos ldquoSolar light-induced photoelectrocatalytic degra-dation of bisphenol-A on TiO

2ITO film anode and BDD

cathoderdquo Catalysis Today vol 209 pp 74ndash78 2013[6] S D Richardson ldquoWater analysis emerging contaminants and

current issuesrdquo Analytical Chemistry vol 81 no 12 pp 4645ndash4677 2009

[7] C I Kosma D A Lambropoulou and T A Albanis ldquoOccur-rence and removal of PPCPs in municipal and hospital wastew-aters inGreecerdquo Journal ofHazardousMaterials vol 179 no 1ndash3pp 804ndash817 2010

[8] J L Rodrıguez-Gil M Catala S G Alonso et al ldquoHeteroge-neous photo-Fenton treatment for the reduction of pharmaceu-tical contamination in Madrid rivers and ecotoxicological eval-uation by a miniaturized fern spores bioassayrdquo Chemospherevol 80 no 4 pp 381ndash388 2010

[9] G Gatidou E Vassalou and N S Thomaidis ldquoBioconcen-tration of selected endocrine disrupting compounds in theMediterranean musselMytilus galloprovincialisrdquoMarine Pollu-tion Bulletin vol 60 no 11 pp 2111ndash2116 2010

[10] M Gros M Petrovic and D Barcelo ldquoTracing pharmaceuticalresidues of different therapeutic classes in environmental watersby using liquid chromatographyquadrupole-linear ion trapmass spectrometry and automated library searchingrdquoAnalyticalChemistry vol 81 no 3 pp 898ndash912 2009

International Journal of Photoenergy 9

[11] A S Stasinakis G Gatidou D Mamais N S Thomaidis andT D Lekkas ldquoOccurrence and fate of endocrine disrupters inGreek sewage treatment plantsrdquoWater Research vol 42 no 6-7 pp 1796ndash1804 2008

[12] M Auriol Y Filali-Meknassi R D Tyagi C D Adams and RY Surampalli ldquoEndocrine disrupting compounds removal fromwastewater a new challengerdquo Process Biochemistry vol 41 no3 pp 525ndash539 2006

[13] Z Frontistis D Fatta-Kassinos D Mantzavinos and N P Xek-oukoulotakis ldquoPhotocatalytic degradation of 17120572-ethynylestra-diol in environmental samples by ZnO under simulated solarradiationrdquo Journal of Chemical Technology and Biotechnologyvol 87 no 8 pp 1051ndash1058 2012

[14] M A Behnajady N Modirshahla N Daneshvar and MRabbani ldquoPhotocatalytic degradation of CI Acid Red 27 byimmobilized ZnO on glass plates in continuous-moderdquo Journalof Hazardous Materials vol 140 no 1-2 pp 257ndash263 2007

[15] A R Khataee ldquoPhotocatalytic removal of CI Basic Red 46on immobilized TiO

2nanoparticles artificial neural network

modellingrdquo Environmental Technology vol 30 no 11 pp 1155ndash1168 2009

[16] V Κoutantou M Kostadima E Chatzisymeon et al ldquoSolarphotocatalytic decomposition of estrogens over immobilizedzinc oxiderdquo Catalysis Today vol 209 pp 66ndash73 2013

[17] T Nakashima Y Ohko D A Tryk and A Fujishima ldquoDecom-position of endocrine-disrupting chemicals in water by useof TiO

2photocatalysts immobilized on polytetrafluoroethylene

mesh sheetsrdquo Journal of Photochemistry and Photobiology A vol151 no 1ndash3 pp 207ndash212 2002

[18] V M Daskalaki Z Frontistis D Mantzavinos and A Katsaou-nis ldquoSolar light-induced degradation of bisphenol-A with TiO

2

immobilized on Tirdquo Catalysis Today vol 161 no 1 pp 110ndash1142011

[19] J Gunlazuardi andW A Lindu ldquoPhotocatalytic degradation ofpentachlorophenol in aqueous solution employing immobilizedTiO2supported on titanium metalrdquo Journal of Photochemistry

and Photobiology A vol 173 no 1 pp 51ndash55 2005[20] R Wang D Ren S Xia Y Zhang and J Zhao ldquoPhotocatalytic

degradation of Bisphenol A (BPA) using immobilized TiO2and

UV illumination in a horizontal circulating bed photocatalyticreactor (HCBPR)rdquo Journal of Hazardous Materials vol 169 no1ndash3 pp 926ndash932 2009

[21] E S Galbavy K Ram and C Anastasio ldquo2-Nitrobenzaldehydeas a chemical actinometer for solution and ice photochemistryrdquoJournal of Photochemistry and Photobiology A vol 209 no 2-3pp 186ndash192 2010

[22] M A Behnajady N Modirshahla and R Hamzavi ldquoKineticstudy on photocatalytic degradation of CI Acid Yellow 23 byZnOphotocatalystrdquo Journal ofHazardousMaterials vol 133 no1ndash3 pp 226ndash232 2006

[23] F Mendez-Arriaga M I Maldonado J Gimenez S Esplugasand S Malato ldquoAbatement of ibuprofen by solar photocatalysisprocess enhancement and scale uprdquo Catalysis Today vol 144no 1-2 pp 112ndash116 2009

[24] Z Frontistis and D Mantzavinos ldquoSonodegradation of 17120572-ethynylestradiol in environmentally relevant matrices labora-tory-scale kinetic studiesrdquo Ultrasonics Sonochemistry vol 19no 1 pp 77ndash84 2012

[25] L A T Espinoza M Neamtu and F H Frimmel ldquoThe effect ofnitrate Fe(III) and bicarbonate on the degradation of bisphenolA by simulated solar UV-irradiationrdquo Water Research vol 41no 19 pp 4479ndash4487 2007

[26] C Sirtori A Aguera W Gernjak and S Malato ldquoEffect ofwater-matrix composition on trimethoprim solar photodegra-dation kinetics and pathwaysrdquoWater Research vol 44 no 9 pp2735ndash2744 2010

[27] Z Frontistis C Drosou K Tyrovola et al ldquoExperimental andmodeling studies of the degradation of estrogen hormones inaqueous TiO

2suspensions under simulated solar radiationrdquo

Industrial and Engineering Chemistry Research vol 51 no 51pp 16552ndash16563 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

International Journal of Photoenergy 9

[11] A S Stasinakis G Gatidou D Mamais N S Thomaidis andT D Lekkas ldquoOccurrence and fate of endocrine disrupters inGreek sewage treatment plantsrdquoWater Research vol 42 no 6-7 pp 1796ndash1804 2008

[12] M Auriol Y Filali-Meknassi R D Tyagi C D Adams and RY Surampalli ldquoEndocrine disrupting compounds removal fromwastewater a new challengerdquo Process Biochemistry vol 41 no3 pp 525ndash539 2006

[13] Z Frontistis D Fatta-Kassinos D Mantzavinos and N P Xek-oukoulotakis ldquoPhotocatalytic degradation of 17120572-ethynylestra-diol in environmental samples by ZnO under simulated solarradiationrdquo Journal of Chemical Technology and Biotechnologyvol 87 no 8 pp 1051ndash1058 2012

[14] M A Behnajady N Modirshahla N Daneshvar and MRabbani ldquoPhotocatalytic degradation of CI Acid Red 27 byimmobilized ZnO on glass plates in continuous-moderdquo Journalof Hazardous Materials vol 140 no 1-2 pp 257ndash263 2007

[15] A R Khataee ldquoPhotocatalytic removal of CI Basic Red 46on immobilized TiO

2nanoparticles artificial neural network

modellingrdquo Environmental Technology vol 30 no 11 pp 1155ndash1168 2009

[16] V Κoutantou M Kostadima E Chatzisymeon et al ldquoSolarphotocatalytic decomposition of estrogens over immobilizedzinc oxiderdquo Catalysis Today vol 209 pp 66ndash73 2013

[17] T Nakashima Y Ohko D A Tryk and A Fujishima ldquoDecom-position of endocrine-disrupting chemicals in water by useof TiO

2photocatalysts immobilized on polytetrafluoroethylene

mesh sheetsrdquo Journal of Photochemistry and Photobiology A vol151 no 1ndash3 pp 207ndash212 2002

[18] V M Daskalaki Z Frontistis D Mantzavinos and A Katsaou-nis ldquoSolar light-induced degradation of bisphenol-A with TiO

2

immobilized on Tirdquo Catalysis Today vol 161 no 1 pp 110ndash1142011

[19] J Gunlazuardi andW A Lindu ldquoPhotocatalytic degradation ofpentachlorophenol in aqueous solution employing immobilizedTiO2supported on titanium metalrdquo Journal of Photochemistry

and Photobiology A vol 173 no 1 pp 51ndash55 2005[20] R Wang D Ren S Xia Y Zhang and J Zhao ldquoPhotocatalytic

degradation of Bisphenol A (BPA) using immobilized TiO2and

UV illumination in a horizontal circulating bed photocatalyticreactor (HCBPR)rdquo Journal of Hazardous Materials vol 169 no1ndash3 pp 926ndash932 2009

[21] E S Galbavy K Ram and C Anastasio ldquo2-Nitrobenzaldehydeas a chemical actinometer for solution and ice photochemistryrdquoJournal of Photochemistry and Photobiology A vol 209 no 2-3pp 186ndash192 2010

[22] M A Behnajady N Modirshahla and R Hamzavi ldquoKineticstudy on photocatalytic degradation of CI Acid Yellow 23 byZnOphotocatalystrdquo Journal ofHazardousMaterials vol 133 no1ndash3 pp 226ndash232 2006

[23] F Mendez-Arriaga M I Maldonado J Gimenez S Esplugasand S Malato ldquoAbatement of ibuprofen by solar photocatalysisprocess enhancement and scale uprdquo Catalysis Today vol 144no 1-2 pp 112ndash116 2009

[24] Z Frontistis and D Mantzavinos ldquoSonodegradation of 17120572-ethynylestradiol in environmentally relevant matrices labora-tory-scale kinetic studiesrdquo Ultrasonics Sonochemistry vol 19no 1 pp 77ndash84 2012

[25] L A T Espinoza M Neamtu and F H Frimmel ldquoThe effect ofnitrate Fe(III) and bicarbonate on the degradation of bisphenolA by simulated solar UV-irradiationrdquo Water Research vol 41no 19 pp 4479ndash4487 2007

[26] C Sirtori A Aguera W Gernjak and S Malato ldquoEffect ofwater-matrix composition on trimethoprim solar photodegra-dation kinetics and pathwaysrdquoWater Research vol 44 no 9 pp2735ndash2744 2010

[27] Z Frontistis C Drosou K Tyrovola et al ldquoExperimental andmodeling studies of the degradation of estrogen hormones inaqueous TiO

2suspensions under simulated solar radiationrdquo

Industrial and Engineering Chemistry Research vol 51 no 51pp 16552ndash16563 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of