research article phenol photocatalytic degradation...

Hindawi Publishing CorporationJournal of Environmental and Public HealthVolume 2013 Article ID 815310 9 pageshttpdxdoiorg1011552013815310

Research ArticlePhenol Photocatalytic Degradation by Advanced OxidationProcess under Ultraviolet Radiation Using Titanium Dioxide

Ali Nickheslat1 Mohammad Mehdi Amin2 Hassan Izanloo3

Ali Fatehizadeh2 and Seyed Mohammad Mousavi4

1 Islamic Azad University Bandar Abbas Branch Hormozgan Bandar Abbas Iran2 Environment Research Center Isfahan University of Medical Sciences (IUMS) and Department of Environmental Health EngineeringSchool of Health Isfahan University of Medical Sciences (IUMS) Isfahan Iran

3 Research Center for Environmental Pollutants and Department of Environmental Health Engineering Health FacultyQom University of Medical Sciences Qom Iran

4 Isfahan Water and Wastewater Company Isfahan Iran

Correspondence should be addressed to Mohammad Mehdi Amin aminhlthmuiacir

Received 19 October 2012 Accepted 4 March 2013

Academic Editor Roya Kelishadi

Copyright copy 2013 Ali Nickheslat et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Background The main objective of this study was to examine the photocatalytic degradation of phenol from laboratory samplesand petrochemical industries wastewater under UV radiation by using nanoparticles of titanium dioxide coated on the inner andouter quartz glass tubes Method The first stage of this study was conducted to stabilize the titanium dioxide nanoparticles inanatase crystal phase using dip-coating sol-gel method on the inner and outer surfaces of quartz glass tubesThe effect of importantparameters including initial phenol concentration TiO

2catalyst dose duration of UV radiation pH of solution and contact time

was investigatedResults In the dip-coat lining stage the produced nanoparticles with anatase crystalline structure have the averageparticle size of 30 nm and are uniformly distributed over the tube surface The removal efficiency of phenol was increased with thedescending of the solution pH and initial phenol concentration and rising of the contact time Conclusion Results showed thatthe light easily passes through four layers of coating (about 105 nm) The highest removal efficiency of phenol with photocatalyticUVTiO

2process was 50 at initial phenol concentration of 30mgL solution pH of 3 and 300 min contact timeThe comparison

of synthetic solution and petrochemical wastewater showed that at same conditions the phenol removal efficiency was equal

1 Introduction

The most important problem that can threaten the waterecology and public health is the toxic and resistant com-pounds that can release to the environment through indus-trial wastewater [1] Among the chemical compounds thatare present in industrial wastewaters the phenol and itsderivatives are prevalent in industrial effluent in additionthey can be released to water resources through naturalways (degradation of algae or of organic vegetation) Alsodue to the physical structure phenol was found in chemicalsolutions and even in the municipal wastewater Due torelatively stability in environment solubility in water high

toxicity and associated health problems phenol removalfrom industrial wastewater is important [2]

The phenol compounds can be released to environmentthrough some industrial wastewater including coal industryresin industries paint industries pesticides medicine andcosmetic products oil refinery petrochemical coal minesaluminum and steel industries compost car productionand chemical industry which can lead to water resourcescontamination Phenol is also found in cleaningmaterials anddisinfectants cigarettes car exhausts and some pesticides[3 4]

Phenol is involved in toxic pollutants and the USEnvironmental Protection Agency reported that phenol is a

2 Journal of Environmental and Public Health

priority among pollutants group [5] Due to human healtheffect of phenol the restrict standards was passed WorldHealth Organization (WHO) recommended that phenolconcentration in water resources entering conventional watertreatment must be lt2120583gL Furthermore the concentrationof phenol chlorophenols 2 4 6 trichlorophenol in drinkingwater must be lt01 120583gL [6] According to USEPA standardand the permitted levels of phenol in water resources forhuman use and for fisheries are 03 and 26mgL respectivelyFurthermore based on the standards of Japan the permittedlevel in industrial wastewater effluent is 5mgL [7]

Somemethods were used in the treatment of wastewaterscontaining resistant organic matters such as phenol Degra-dation of phenol usually takes place by physicochemicalmethods including adsorption using activated carbon [8 9]biological treatment [10] emulsion liquidmembrane [11] ionexchanges advanced oxidation processes (AOPs) (includingcavitation Fenton and photocatalyst) [10 12] chemicaloxidation (methods in which ozone and water are used)photochemical and electrochemical and ultrasound wavessuch as sonochemical photochemical photosonochemical[13] and hybrid of mentioned methods

The hydrothermal oxidation process consists of wet airoxidation and oxidation in subcritical critical and supercrit-ical water and was used for phenol degradation but due totheir high cost and energy consuming they are used in specialconditions

Biological degradation usually takes longer time and isoften affected by temperature variations and phenomenon oftoxic pollutants [2 14] The ion exchanging and adsorptionprocesses are very expensive [2] However advanced oxida-tion processes (AOPs) are among themost effective processesin degradation of resistant compounds

Generally AOPs include processes in which activehydroxyl radicals (OH∙) as a strong oxidant for degrada-tion and destruction of polluting materials are producedusing different methods Due to high oxidation capacity ofhydroxyl radicals (28 V) most of the AOPs are based onthis active radical [15 16] One of the most effective methodsof advanced oxidation is the use of UV ray and oxidantsuch as H

2O2 O3 and TiO

2[4 17] In recent years com-

mon processes were used in the removal of organic matterincluding Fenton photofenton UVTiO

2 andUVH

2O2O3

In photocatalytic degradation the pollutants are degradedunder theUV radiation in the presence of particles ofmetallicoxides such as ZnO and TiO

2[8 14 18] Titanium dioxide is a

metallic oxide well known for degradation of organic matters[19] and is of relatively low cost nontoxic and insoluble inwater [20 21]

UVTiO2process is one of the latest and most effective

methods for the treatment of these pollutants In this processtitanium dioxide nanoparticles were extensively used inphotocatalytic reactions as a catalystThe small particle size ofthis metallic oxide can lead to the increase of special surfaceof catalyst and the improvement of the photocatalytic activityIn recent research titanium dioxide nanoparticles in anatasecrystalline phase are used and in order to description ofproduced XRD spectrum and their SEM images was used[22 23]

When titanium dioxide was used as suspension formnanoparticles separation from liquid needed in which sepa-ration needed to high investment and operational costs Alsoin this method thedesigning and operation at continuoussystemwere impossibleThus stabilizing titaniumdioxide ona solid film caused the removal of the above difficulties andmade the industrial application of these processes possibleThe improvement of AOP and its application in the industrialprojects necessitate the stabilization of photocatalyst on asolid film

Various methods were applied for the synthesis of tita-nium dioxide photocatalyst These methods are divided intotwo main groups (1) wet chemistry methods such as sol-gel method and (2) dry method such as aerosol [24 25]Also different methods are used for the preparation oftitanium dioxide films such as chemical vapor depositionhot oxidation electron beam evaporation sol-gel methodwith rotating coating and dip coating of titanium dioxidecompound [26 27]

In recent year sol-gel technique is a new method thatis used for the synthesis of mineral oxide materials in lowtemperatures and in nanoscale In fact sol-gel is an efficientphysicalchemical method for producing materials in formof powder ceramic coating fibers thin layers and porousmaterials In this method hydrolysis and repetitive conden-sation reactions of an alkoxide in presence of humidity canproduce mineral oxides with particle size that is adjustablefrom nanometer to the micron

PrecursorsHydrolysis997888997888997888997888997888997888997888997888rarr Sol Condensation

997888997888997888997888997888997888997888997888997888997888rarr Gel (1)

In photocatalytic degradation light energy was used inphoton formwithwavelength less than 3875 nm as ultravioletradiation or sunlight The exposure of electrons surface oftitanium atoms with light was caused exciting the surfaceelectron and moving from valance layer to transition layer(eCB-) The changing in energy level can form the freeelectron in form of OH∙ or other radicals that they canoxidize organic matters and reduced of metals [2 8 14 28]Photocatalytic destruction of phenol follows the first-orderreaction (Figure 1)

The advantages of AOP were including the low coststability and high efficiency [16 28]

This study was attempts to coating layers of titaniumdioxide on the inner and outer surface of quartz tubes andapplication of AOP (UVTiO

2) for phenol remove from

industrial and petrochemical wastewater

2 Materials and Methods

21 Fixation of TiO2on Surfaces of Quartz Tubes For produc-

tion of photocatalytic coatings a solution from nanoparticlesof TiO

2with 1 (ww) was preparedThe TiO

2nanoparticles

were purchased from Nanosav Co with specification ofSAV2104 The TiO

2has an oval shape with diameter of

gt30 nm and the anatase crystalline phase is formed in waterThe TEM image of TiO

2nanoparticles and XRD spectrum of

anatase TiO2nanoparticles are shown in Figures 2 and 3

Journal of Environmental and Public Health 3

H2O

H2O2

O2

O2

∙minus

∙OH

∙OHConduction bandecbminus

vb+

H2O OHminus

+Pollutant

Valence band

Degradation product

120582 lt 387nmℎ

ℎ

Figure 1 Schematic of photocatalytic mechanism of TiO2

Figure 2 TEM image of titanium dioxide nanoparticles

22 Preparation of Underlayer For proper coating of nanolayers on surface there should be no presence of any contami-nation on the underlayer as it can affect the quality of the coatsand create nonuniform layers Underlayers are comprisedof quartz tubes with 20 cm lengths Cleaning method ofunderlayers is follows as

(1) Washing up with soap and water to remove thecontaminants and fats

(2) Acetone washing(3) Heating up in a kiln to 500∘C for 30min(4) Placing underlayers in H

2O2 H2SO4solution at 3 7

ratio (ww) for 1 h For this purpose H2O2was slowly

added to sulfuric acid to prevent bubbles formationThis solution was called piranha solution (strongoxidant) and was able to produce hydroxyl groups onthe surface and create them in a hydrophilic way

(5) After washing underlayers with deionized water wereremained in NH

4OH H

2O2 H2O solution (1 1 5

ww) for 1 h washed with deionized water and driedAfter this glass underlayers are ready for coating

40

20

0

20 30 40 50 60 70

Anatase

Cou

nts

2120579

Figure 3 XRD spectrum related to anatase TiO2nanoparticles

23 Coating The used coating method was a dip coating Inthis method coat layers are formed by dipping the underlayer into solution and extracting them at constant speedThickness of coat was determined by speed of extractingand solution viscosity Dip coating is an efficient and quickmethod but it was suffering from some disadvantages includ-ing difference between thickness-coated layersThe thicknessof top layers is slightly less than bottom layer Figure 4 showsthe system used for coating The cleaned glass under layerwas connected to mechanical hoist and under layer wasvertically dipped into nanoparticle cell and kept for 1mintill the solution becomes undistributed So the under layerwas extracted at a constant speed and layer thickness wascontrolled by variation of speed of hoisting up Figures 45 and 6 showed stages of dip coating schematic of dip-coating set up method and quartz tubes coated with TiO

2

nanoparticle respectively To perform the coating of quartztubes dip-coating method 180mL of TiO

2nanoparticle

solution was used to create coating layer with thicknessasymp400 nm on the surfaces of tubes

24 Photocatalysis Reactor Set Up Thephotocatalysis reactorconsisted of 8 coated quartz tubes with TiO

2nanoparticles

with 30mm inside diameter as parallel arrangement andcontact tank The contact tank was constructed of plexiglasswith dimensions of 50 10 15 cm and 35 L working volumeThe quartz tubs were immersed in open top water bath Thefeed solution was introduced to system by means of twoperistaltic pumps and flowed insideoutside tubes at uniformconstant speed In photocatalysis reactor in order to provideUV radiation four UV lamps with maximum wavelengths of365 nm and 250w were used on top of reactorThe schematicof photocatalysis reactor and applied UV lamps is shown ifFigure 7

25 Operational Conditions An investigation program com-prising 5 different phases was performed Each phase cor-responded to certain intensity of light and distance fromUV source (15 30 50 100 and 150 cm) initial phenol


(a) (b)

(c) (d)

Figure 4 Stages of dip-coating method

Figure 5 The schematic of dip-coating set up

concentrations (30 40 60 80 and 100mgL) solution pH(3 65 9 and 11) contact time (from 0 to 300min) andphenol removal of Bandar Abbas oil refinery wastewater Allexperiments were performed at 25∘C

26 Chemicals and Instrument All chemical substances werepurchased from Merck Co The amounts of phenol wereanalyzed using the standard methods [29] The spectropho-tometer was used for phenol analysis at wavelength of670mm

3 Results

31 Optical Properties of TiO2Layers After coating glass

underlayers their optical transmission spectrum was deter-mined by spectrophotometer UV-Vis at wavelength range


Figure 6 The quartz tubes coated with TiO2nanoparticle

Figure 7 Photocatalysis laboratory-scale plant

of 200 to 1100 nm accuracy of 1 nm and scanning speed of400 nmmin and air as reference

The TiO2(1wt) cell was used for coating with 3mmsec

for speed of coating layers As shown in Figure 8 after firstlayer coating the edge of TiO

2film adsorption has slightly

moved from glass position which indicated that coating pro-cess successfully performed This slight movement showedthat TiO

2film deposit on glass was low and thin TiO

2is a

semiconductor with indirect energy in range of 3ndash32 ev andit could not properly absorb light in the range of UVA (320ndash380 nm) which includes sun UV rays For this reason edge ofadsorption could not clearly appear at thin film of TiO

2 and

oscillations could not be observe due to interference effectTherefore only a thin film of TiO

2was produced

To increase layers thickness coating was repeated fewtimes Optical transmission spectrum of TiO

2film after

coating layers was depicted in Figure 9 For preventing theremoval of TiO

2film of tube surface and for confident

estimating of TiO2film thickness after each coating layers

were placed in a kiln at 200∘C for 10min In thisway the layerswere made dry and hard

According to Figure 9 at first coating the transmittanceof visible light was 85 and the transmittance of visiblelight was reduced with the increasing number of coat layers(thickness of TiO

2film)This reduction in transmittancemay

be related to interference effects and light scattering In thisstage the coating speed was 3mmsec and after each layerlayers were placed in a kiln at 200∘C for 10min

In a thicknesses less than 100 nm optical transmissionspectrum was not indicating oscillations due to interference

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

Glass

minus2

TiO2 film

Figure 8 Optical transmission spectrum through glass only and athin TiO

2layer (coating speed 3mmsec)

1 layer2 layer

3 layer4 layer

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

Figure 9 Optical transmission spectrum through some layers ofTiO2after each coating

effects For this the optical transmission spectrum could notbe done for the first and second layer As the thickness of TiO

2

film was increased the effect of oscillations clearly appearedFigure 10 showed the results of optical transmittance for thethird and fourth layers of TiO

2film

As seen in Figure 10 the experimental and calculatedtransmitted spectrum in wavelengths of 400ndash1100 nm wasagreed to large extent Results showed that in monolayercoating 30 nm of TiO

2film was adsorbed on under layer

and after dozen coating the TiO2film thickness reached to

360 nm

32 Effects of Intensity of Light and Distance from UV SourceDistance of UV lamps from phenol solution and water wasadjusted to 15 30 50 100 and 150 cmThe results of the effectsof intensity of UV source are shown in Figure 11 The phenolremoval by photocatalysiswas straight line decreasedwith therising of UV lamps from reactor

As in Figure 11 it appeared that optimum distance inwhich concentration reduction occursmost rapidlywas 15 cmfrom surface of phenol solution The reason for this may


ExpCal

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

(a)

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

ExpCal

(b)

Figure 10 Experimental and calculated optical transmission spectrum of TiO2layers (a) third layer and (b) fourth layer

05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(b)

Figure 11 Effect of various intensities of UV lamps on (a) effluent phenol concentration and (b) removal efficiency of phenol (1198620 40mgL

solution pH 65 and contact time 0ndash300min)

be due to lower light intensity and reduction of surfacephotocatalytic activities

33 Effect of Initial Phenol Concentrations and ContactTime To assess the effect of initial phenol concentrationsthe solutions with concentrations of 30 40 60 80 and100mgL were provided and were fed to reactor Figure 12showed the results related to of effect of initial phe-nol concentrations on photocatalysis phenol removal effi-ciency In terms of Figure 12 the phenol removal at initialconcentration of 25 30 and 40mgL by photocatalysislaboratory-scale plant was about 50 at 300min contacttime

The percentage of phenol removal (Figure 12) decreaseswith the mounting of the initial concentration of phenolfrom 50 to 20 This could be due to the saturation of thesurface coat of photocatalyst with by-product that resultedfrom degradation of phenol As clearly seen from Figure 12

the increase in the duration of photocatalysis process for over5 h led to further diminishment in phenol concentration

34 Effect of pH The reduction of phenol was studied fromthe aqueous solution at different pH values The solutionwith phenol concentration of 45mgL was provided andHCland NH

4OH were used in order to adjust solution pH at

values of 3 65 9 and 11 The results obtained are shown inFigure 13 which shows the effect of solution pH on the phenolremoval from the aqueous solution by photocatalysis processexpressed in terms of the effluent phenol concentration andphenol removed percent It is clear that phenol was effectivelyremoved at solution pH 3

35 Phenol Removal from Bandar Abbas Oil RefineryWastew-ater This study was performed in which a pilot scale pho-tocatalysis system was fed from Bandar Abbas oil refinerywastewaterThe composition of the Bandar Abbas oil refinerywastewater varied as follows phenol concentration (45mgL)


0

20

40

60

80

100

120

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(b)

Figure 12 Influence of initial phenol concentration and contact time (a) effluent phenol concentration and (b) phenol removal efficiency(1198620 25ndash100mgL solution pH 65 distance of UV source 15 cm and contact time 0ndash300min)

05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

pH 3pH 65

pH 9pH 11

(a)

0

10

20

30

40

50

60

70

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

pH 3pH 65

pH 9pH 11

(b)

Figure 13 Effect of solution pH on (a) effluent phenol concentration and (b) phenol reduction (1198620 40mgL distance of UV source 15

contact time 0ndash300min and various solution pH)

and pH (55) Figure 14 shows the evolution of phenolremoval from Bandar Abbas oil refinery wastewater

4 Discussion

Photocatalytic degradation of phenol with TiO2as catalyst

and UV radiation is the newest process In this research pho-tocatalytic degradation of phenol with emphasis on contacttime solution pH variations UV radiation and initial phenolconcentration was assessed

41 TiO2Coating Layers In the first stage of this research

solution of the cell containing TiO2nanoparticles with

anatase crystallinewas prepared So coating of solution of cellcontaining crystallized nanoparticles insideoutside quartztubes using dip-coating (sol-gel) method was induced The

particles size crystalline structure of coated surface withX-ray tests and SEM were assessed Results indicated thatthe obtained nanoparticles had anatase crystalline structurewith average particles size of 30 nm and were uniformlydistributed over tube surface Also results showed that inmonolayer coating 30 nm of TiO

2film was adsorbed on

under layer and after dozen coating the TiO2film thickness

reached to 360 nm It was clear that light could easily passthrough the four layers of coating (15mm)

42 Photocatalytic Degradation of Phenol These results indi-cated that increasing contact time and reducing initial phenolconcentration led to improvement in the removal percentageof phenol Results of the experiment showed that in thisprocess removal efficiency was higher in low solution pHSo with rising the solution pH from 3 to 11 phenol removalefficiency varied from 60 to 30


0

10

20

30

40

50

60

0

10

20

30

40

50

0 50 100 150 200 250 300

Rem

oval

effici

ency

()

Con

cent

ratio

n (m

gL)

ConcentrationRemoval

Time (min)

Figure 14 Phenol removal from Bandar Abbas oil refinery wastew-ater with phenol concentration of 45mgL

As mentioned previously from assessment of initialphenol concentration and with regard to contact time andsolution pH it could be deducted that for lower concentrationof phenol in wastewater removal efficiency is higher Theeffect of solution pH showed that pH is an importantvariable and plays an important role in the equilibriumof acid and alkalinity thereby affected on degraded andnondegraded concentration of phenol The maximum phe-nol efficiency was related to solution pH of 3 at phenolconcentration of 30mgL At constant amount of TiO

2film

on tubes increasing initial phenol concentration resultedin low phenol removal efficiency and greater contact timeneeded It can be predicted that by the increasing TiO

2

contact surface the removal of higher concentrations willbe possible Comparison obtained results of phenol degra-dation from laboratory sample and industrial wastewatershowed that at similar conditions the phenol removal wasequal

Photocatalysis laboratory scale studies showed that thisprocess could be suggested as an applicable method forremoving phenol as toxic and dangerousmatter from effluentand wastewater by degradation and converting it into safematter Application of these studies on laboratory scale couldprovide proper information for using this process as fullscale

It can be expected that AOP including UVTiO2with

advantages such as nonproduction of by-products produc-tion of nondangerous by-products environment friendly andhigh efficiency in comparison to the biological methods willhave a suitable layout in water and wastewater industriesPhotocatalytic UVTiO

2process in conjunction with other

processes such as membrane process application of fixedTiO2film (present research) and changing of semiconductor

TiO2surfaces and replacing of visible light in lieu UV

radiation could be one of the most effective methods forthe removal of organic solutions including phenol and itscompounds In addition we suggested that other studiesshould be performed to test this method for some resistanceand toxic compounds

Conflict of Interests

The authors declare that there is no conflict of interests

Acknowledgment

The authors would like to thank Islamic Azad UniversityBandar Abbas Branch Hormozgan Bandar Abbas Iran forits support

References

[1] W W Eckenfelder and A J Englande ldquoInnovative biologicaltreatment for sustainable development in the chemical indus-triesrdquoWater Science and Technology vol 38 no 4-5 pp 111ndash1201998

[2] C N Sawyer P L McCarty and G F Parkin ChemistryFor Environmental Engineering and Science McGraw-Hill NewYork NY USA 5th edition 2003

[3] N L Nemerow Industrial andHazardousWaste Treatment VanNostrand Reinhold New York NY USA 2nd edition 1991

[4] F V Santos E B Azevedo G L SantrsquoAnna and M DezottildquoPhotocatalysis as a tertiary treatment for petroleum refinerywastewatersrdquo Brazilian Journal of Chemical Engineering vol 23no 4 pp 451ndash460 2006

[5] B G Sullivan and G R Krieger Clinical Environmental Healthand Toxic Exposure Lippincott Williams amp Wilkins Philadel-phia Pa USA 2nd edition 2001

[6] J DeZuane Hand Book of Drinking Water Quality John Wileyamp Sons 2nd edition 1997

[7] E R Roberts Bioremediation of Peteroleum Contaminate SitesSmoley Taylor amp Francis 1992

[8] FAkbal andANOnar ldquoPhotocatalytic degradation of phenolrdquoEnvironmental Monitoring and Assessment vol 83 no 3 pp295ndash302 2003

[9] B Ozkaya ldquoAdsorption and desorption of phenol on activatedcarbon and a comparison of isotherm modelsrdquo Journal ofHazardous Materials vol 129 no 1ndash3 pp 158ndash163 2006

[10] K H Wang Y H Hsieh M Y Chou and C Y ChangldquoPhotocatalytic degradation of 2-chloro and 2-nitrophenol bytitanium dioxide suspensions in aqueous solutionrdquo AppliedCatalysis B vol 21 no 1 pp 1ndash8 1999

[11] Y H Wan X De Wang and X J Zhang ldquoTreatment of highconcentration phenolic waste water by liquid membrane withN503

as mobile carrierrdquo Journal of Membrane Science vol 135no 2 pp 263ndash270 1997

[12] M Petrovic and J Radjenovic ldquoAdvanced Oxidation Processes(AOPs) applied for wastewater and drinking water treatmentElementation of pharmaceuticalsrdquo The Holistic Approach toEnvironment vol 1 no 2 pp 63ndash674 2011

[13] J Lifka B Ondruschka and J Hofmann ldquoTheuse of ultrasoundfor the degradation of pollutants in water aquasonolysismdashareviewrdquo Engineering in Life Sciences vol 3 no 6 pp 253ndash2622003

[14] K H Lanouette ldquoTreatment of phenolic wastesrdquo ChemicalEngineering vol 17 pp 99ndash106 1997

[15] T Oppenlander Photochemical Purification of Water and AirWiley-VCH Weinheim Germany 2002

[16] USEPA Handbook Advanced Photochemical Oxidation Pro-cesses Office of Research and Development Washington DCUSA 1998 EPA625R-98004


[17] A R Torres E B Azevedo N S Resende and M Dezotti ldquoAcomparison between bulk and supported TiO

2photocatalysts

in the degradation of formic acidrdquo Brazilian Journal of ChemicalEngineering vol 24 no 2 pp 185ndash192 2007

[18] N Singh and J Singh ldquoAn enzymatic method for removal ofphenol from industrial effluentrdquo Preparative Biochemistry andBiotechnology vol 32 no 2 pp 127ndash133 2002

[19] K Tennakone C T K Tilakaratne and I R M KottegodaldquoPhotocatalytic degradation of organic contaminants in waterwith TiO

2supported on polythene filmsrdquo Journal of Photochem-

istry and Photobiology A vol 87 no 2 pp 177ndash179 1995[20] S Lakshmi R Renganathan and S Fujita ldquoStudy on TiO

2-

mediated photocatalytic degradation of methylene bluerdquo Jour-nal of Photochemistry and Photobiology A vol 88 no 2-3 pp163ndash167 1995

[21] A Vidal A I Dıaz A El Hraiki et al ldquoSolar photocatalysisfor detoxification and disinfection of contaminated water pilotplant studiesrdquo Catalysis Today vol 54 no 2-3 pp 283ndash2901999

[22] S Karthikeyan and A Navaneetha ldquoDegradation of phenol andm-cresol in aqueous solutions using indigenously developedmicrowave-ultraviolet reactorrdquo Journal of Scientific and Indus-trial Research vol 70 no 1 pp 71ndash76 2011

[23] C L Wong Y N Tan and A R Mohamed ldquoPhotocatalyticdegradation of phenol using immobilized TiO

2nanotube pho-

tocatalystsrdquo Journal of Nanotechnology vol 2011 Article ID904629 9 pages 2011

[24] X Chen and S S Mao ldquoTitanium dioxide nanomaterialssynthesis properties modifications and applicationsrdquoChemicalReviews vol 107 no 7 pp 2891ndash2959 2007

[25] A Fujishima T N Rao and D A Tryk ldquoTitanium dioxidephotocatalysisrdquo Journal of Photochemistry and Photobiology Cvol 1 no 1 pp 1ndash21 2000

[26] H Imai and H Hirashima ldquoPreparation of porous anatasecoating from sol-gel-derived titanium dioxide and titaniumdioxide-silica bywater-vapor exposurerdquo Journal of theAmericanCeramic Society vol 82 no 9 pp 2301ndash2304 1999

[27] K N P Kumar K Keizer A J Burggraaf T Okubo HNagamoto and S Morooka ldquoDensification of nanostructuredtitania assisted by a phase transformationrdquo Nature vol 358 no6381 pp 48ndash51 1992

[28] P Le-Clech E K Lee and V Chen ldquoHybrid photocatal-ysismembrane treatment for surface waters containing lowconcentrations of natural organic mattersrdquoWater Research vol40 no 2 pp 323ndash330 2006

[29] APHA Standard Methods for Examination of Water andWastewater Washington DC USA 2005

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priority among pollutants group [5] Due to human healtheffect of phenol the restrict standards was passed WorldHealth Organization (WHO) recommended that phenolconcentration in water resources entering conventional watertreatment must be lt2120583gL Furthermore the concentrationof phenol chlorophenols 2 4 6 trichlorophenol in drinkingwater must be lt01 120583gL [6] According to USEPA standardand the permitted levels of phenol in water resources forhuman use and for fisheries are 03 and 26mgL respectivelyFurthermore based on the standards of Japan the permittedlevel in industrial wastewater effluent is 5mgL [7]

Somemethods were used in the treatment of wastewaterscontaining resistant organic matters such as phenol Degra-dation of phenol usually takes place by physicochemicalmethods including adsorption using activated carbon [8 9]biological treatment [10] emulsion liquidmembrane [11] ionexchanges advanced oxidation processes (AOPs) (includingcavitation Fenton and photocatalyst) [10 12] chemicaloxidation (methods in which ozone and water are used)photochemical and electrochemical and ultrasound wavessuch as sonochemical photochemical photosonochemical[13] and hybrid of mentioned methods

The hydrothermal oxidation process consists of wet airoxidation and oxidation in subcritical critical and supercrit-ical water and was used for phenol degradation but due totheir high cost and energy consuming they are used in specialconditions

Biological degradation usually takes longer time and isoften affected by temperature variations and phenomenon oftoxic pollutants [2 14] The ion exchanging and adsorptionprocesses are very expensive [2] However advanced oxida-tion processes (AOPs) are among themost effective processesin degradation of resistant compounds

Generally AOPs include processes in which activehydroxyl radicals (OH∙) as a strong oxidant for degrada-tion and destruction of polluting materials are producedusing different methods Due to high oxidation capacity ofhydroxyl radicals (28 V) most of the AOPs are based onthis active radical [15 16] One of the most effective methodsof advanced oxidation is the use of UV ray and oxidantsuch as H

2O2 O3 and TiO

2[4 17] In recent years com-

mon processes were used in the removal of organic matterincluding Fenton photofenton UVTiO

2 andUVH

2O2O3

In photocatalytic degradation the pollutants are degradedunder theUV radiation in the presence of particles ofmetallicoxides such as ZnO and TiO

2[8 14 18] Titanium dioxide is a

metallic oxide well known for degradation of organic matters[19] and is of relatively low cost nontoxic and insoluble inwater [20 21]

UVTiO2process is one of the latest and most effective

methods for the treatment of these pollutants In this processtitanium dioxide nanoparticles were extensively used inphotocatalytic reactions as a catalystThe small particle size ofthis metallic oxide can lead to the increase of special surfaceof catalyst and the improvement of the photocatalytic activityIn recent research titanium dioxide nanoparticles in anatasecrystalline phase are used and in order to description ofproduced XRD spectrum and their SEM images was used[22 23]

When titanium dioxide was used as suspension formnanoparticles separation from liquid needed in which sepa-ration needed to high investment and operational costs Alsoin this method thedesigning and operation at continuoussystemwere impossibleThus stabilizing titaniumdioxide ona solid film caused the removal of the above difficulties andmade the industrial application of these processes possibleThe improvement of AOP and its application in the industrialprojects necessitate the stabilization of photocatalyst on asolid film

Various methods were applied for the synthesis of tita-nium dioxide photocatalyst These methods are divided intotwo main groups (1) wet chemistry methods such as sol-gel method and (2) dry method such as aerosol [24 25]Also different methods are used for the preparation oftitanium dioxide films such as chemical vapor depositionhot oxidation electron beam evaporation sol-gel methodwith rotating coating and dip coating of titanium dioxidecompound [26 27]

In recent year sol-gel technique is a new method thatis used for the synthesis of mineral oxide materials in lowtemperatures and in nanoscale In fact sol-gel is an efficientphysicalchemical method for producing materials in formof powder ceramic coating fibers thin layers and porousmaterials In this method hydrolysis and repetitive conden-sation reactions of an alkoxide in presence of humidity canproduce mineral oxides with particle size that is adjustablefrom nanometer to the micron

PrecursorsHydrolysis997888997888997888997888997888997888997888997888rarr Sol Condensation

997888997888997888997888997888997888997888997888997888997888rarr Gel (1)

In photocatalytic degradation light energy was used inphoton formwithwavelength less than 3875 nm as ultravioletradiation or sunlight The exposure of electrons surface oftitanium atoms with light was caused exciting the surfaceelectron and moving from valance layer to transition layer(eCB-) The changing in energy level can form the freeelectron in form of OH∙ or other radicals that they canoxidize organic matters and reduced of metals [2 8 14 28]Photocatalytic destruction of phenol follows the first-orderreaction (Figure 1)

The advantages of AOP were including the low coststability and high efficiency [16 28]

This study was attempts to coating layers of titaniumdioxide on the inner and outer surface of quartz tubes andapplication of AOP (UVTiO

2) for phenol remove from

industrial and petrochemical wastewater

2 Materials and Methods

21 Fixation of TiO2on Surfaces of Quartz Tubes For produc-

tion of photocatalytic coatings a solution from nanoparticlesof TiO

2with 1 (ww) was preparedThe TiO

2nanoparticles

were purchased from Nanosav Co with specification ofSAV2104 The TiO

2has an oval shape with diameter of

gt30 nm and the anatase crystalline phase is formed in waterThe TEM image of TiO

2nanoparticles and XRD spectrum of

anatase TiO2nanoparticles are shown in Figures 2 and 3


H2O

H2O2

O2

O2

∙minus

∙OH


vb+

H2O OHminus

+Pollutant

Valence band

Degradation product

120582 lt 387nmℎ

ℎ










4OH H



40

20

0

20 30 40 50 60 70

Anatase

Cou

nts

2120579



2


2nanoparticle



2nanoparticles




(a) (b)

(c) (d)





3 Results












2is a


2 and


2was produced


2film after









18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

Glass

minus2

TiO2 film



1 layer2 layer

3 layer4 layer

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2



2


2film




360 nm




ExpCal

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

(a)

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

ExpCal

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(b)












0

20

40

60

80

100

120

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

pH 3pH 65

pH 9pH 11

(a)

0

10

20

30

40

50

60

70

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

pH 3pH 65

pH 9pH 11

(b)




4 Discussion












0

10

20

30

40

50

60

0

10

20

30

40

50

0 50 100 150 200 250 300

Rem

oval

effici

ency

()

Con

cent

ratio

n (m

gL)


Time (min)



2film


2











Acknowledgment


References




















2photocatalysts






2-





2nanotube pho-













of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















H2O

H2O2

O2

O2

∙minus

∙OH


vb+

H2O OHminus

+Pollutant

Valence band

Degradation product

120582 lt 387nmℎ

ℎ










4OH H



40

20

0

20 30 40 50 60 70

Anatase

Cou

nts

2120579



2


2nanoparticle



2nanoparticles




(a) (b)

(c) (d)





3 Results












2is a


2 and


2was produced


2film after









18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

Glass

minus2

TiO2 film



1 layer2 layer

3 layer4 layer

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2



2


2film




360 nm




ExpCal

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

(a)

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

ExpCal

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(b)












0

20

40

60

80

100

120

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

pH 3pH 65

pH 9pH 11

(a)

0

10

20

30

40

50

60

70

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

pH 3pH 65

pH 9pH 11

(b)




4 Discussion












0

10

20

30

40

50

60

0

10

20

30

40

50

0 50 100 150 200 250 300

Rem

oval

effici

ency

()

Con

cent

ratio

n (m

gL)


Time (min)



2film


2











Acknowledgment


References




















2photocatalysts






2-





2nanotube pho-













of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















(a) (b)

(c) (d)





3 Results












2is a


2 and


2was produced


2film after









18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

Glass

minus2

TiO2 film



1 layer2 layer

3 layer4 layer

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2



2


2film




360 nm




ExpCal

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

(a)

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

ExpCal

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(b)












0

20

40

60

80

100

120

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

pH 3pH 65

pH 9pH 11

(a)

0

10

20

30

40

50

60

70

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

pH 3pH 65

pH 9pH 11

(b)




4 Discussion












0

10

20

30

40

50

60

0

10

20

30

40

50

0 50 100 150 200 250 300

Rem

oval

effici

ency

()

Con

cent

ratio

n (m

gL)


Time (min)



2film


2











Acknowledgment


References




















2photocatalysts






2-





2nanotube pho-













of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

























2is a


2 and


2was produced


2film after









18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

Glass

minus2

TiO2 film



1 layer2 layer

3 layer4 layer

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2



2


2film




360 nm




ExpCal

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

(a)

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

ExpCal

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(b)












0

20

40

60

80

100

120

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

pH 3pH 65

pH 9pH 11

(a)

0

10

20

30

40

50

60

70

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

pH 3pH 65

pH 9pH 11

(b)




4 Discussion












0

10

20

30

40

50

60

0

10

20

30

40

50

0 50 100 150 200 250 300

Rem

oval

effici

ency

()

Con

cent

ratio

n (m

gL)


Time (min)



2film


2











Acknowledgment


References




















2photocatalysts






2-





2nanotube pho-













of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















ExpCal

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

(a)

18

38

58

78

98

0 200 400 600 800 1000 1200

Tran

smitt

ance

()

Wavelength (nm)

minus2

ExpCal

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

15 cm30 cm50 cm

100 cm150 cm

(b)












0

20

40

60

80

100

120

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

pH 3pH 65

pH 9pH 11

(a)

0

10

20

30

40

50

60

70

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

pH 3pH 65

pH 9pH 11

(b)




4 Discussion












0

10

20

30

40

50

60

0

10

20

30

40

50

0 50 100 150 200 250 300

Rem

oval

effici

ency

()

Con

cent

ratio

n (m

gL)


Time (min)



2film


2











Acknowledgment


References




















2photocatalysts






2-





2nanotube pho-













of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















0

20

40

60

80

100

120

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(a)

0

10

20

30

40

50

60

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

25 mgL30 mgL40 mgL

60 mgL80 mgL100 mgL

(b)


05

1015202530354045

0 40 80 120 160 200 240 280 320

Con

cent

ratio

n (m

gL)

Time (min)

pH 3pH 65

pH 9pH 11

(a)

0

10

20

30

40

50

60

70

0 40 80 120 160 200 240 280 320

Rem

oval

effici

ency

()

Time (min)

pH 3pH 65

pH 9pH 11

(b)




4 Discussion












0

10

20

30

40

50

60

0

10

20

30

40

50

0 50 100 150 200 250 300

Rem

oval

effici

ency

()

Con

cent

ratio

n (m

gL)


Time (min)



2film


2











Acknowledgment


References




















2photocatalysts






2-





2nanotube pho-













of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















0

10

20

30

40

50

60

0

10

20

30

40

50

0 50 100 150 200 250 300

Rem

oval

effici

ency

()

Con

cent

ratio

n (m

gL)


Time (min)



2film


2











Acknowledgment


References




















2photocatalysts






2-





2nanotube pho-













of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of


















2photocatalysts






2-





2nanotube pho-













of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of





















of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















research article phenol photocatalytic degradation...

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