adsorption of bisphenol a on sediments in the yellow

ADSORPTION OF BISPHENOL A ON SEDIMENTSIN THE YELLOW RIVER

W. L. SUN1,∗, J. R. NI1, K. C. O’BRIEN2, P. P. HAO1 and L. Y. SUN1

1Department of Environmental Engineering, Peking University, The Key Laboratory of Water andSediment Sciences, MOE, Beijing 100871, China; 2Engineering Directorate, Lawrence Livermore

National Laboratory, 7000 East Ave., Livermore, CA 94550-9234, USA(∗author for correspondence, e-mail: [email protected], Tel.: +86-10-6276 7014;

Fax: +86-10-6275 1184)

(Received 11 March 2004; accepted 19 June 2005)

Abstract. Bisphenol A is widely used for the production of epoxy resins and polycarbonate plastics,and it has been found in many wastewaters or surface waters. Adsorption of bisphenol A on sedimentssampled from several representative hydrologic stations of the Yellow River was studied, and somefactors that may affect the sorption of bisphenol A were analyzed using the LC-MS/MS followingsolid-phase extraction. The results show that neither linear nor Freundlich isotherms is fit to theexperimental data due to the high carbonate content in sediments. Bisphenol A has greater adsorptionafter the elimination of the carbonate in the sediment, and the adsorption of bisphenol A on the treatedsediment can be described by both the linear and the Freundlich isotherms. The adsorption amountof bisphenol A is related to both the total organic carbon and dissolved organic carbon of sediments.The effects of Ca2+ and K+ on the adsorption of bisphenol A were also studied. It is found that Ca2+

and K+ showed different effects on the adsorption of bisphenol A because of their different valences.

Keywords: adsorption, bisphenol A, LC-MS/MS, sediment, SPE

1. Introduction

Bisphenol A (BPA) is mostly manufactured for the plastics industry. It is an inter-mediate in the production of epoxy resins and polycarbonate plastics. The plasticsare utilized in many food and drink packaging productions to line metal food cans,bottle tops and water supply pipes. Some polymers containing BPA are even usedin dental treatment. In recent years, negative effects have been reported on the en-docrine systems in humans and animals (Watts et al., 2001; Belfroid et al., 2002;Kashiwada et al., 2002; Matsumoto et al., 2003). BPA is mainly discharged in themanufacturing process (washing residue and wastewater), and it may also be inad-vertently released as fugitive dust emission from closed systems during processing,handling, and transportation (Staples et al., 1998). As BPA is widely used in bothhouseholds and industry, it may present in raw sewage, waste water effluents andconcentrated in sewage sludge. Some researchers have reported detection of BPAin some rivers and landfill leachates (Staples et al., 1998; Furhacker et al., 2000;Yamamoto et al., 2001).

Water, Air, and Soil Pollution (2005) 167: 353–364 C© Springer 2005

354 W. L. SUN ET AL.

Besides mixing within the water column, BPA is subject to biodegradation, ad-sorption to soils and suspended solids and sediments, and possibly photodegrada-tion. Adsorption reaction may influence the rate of other processes such as biodegra-dation and photolysis (Bekbolet et al., 1999). The adsorption reaction is governedby the chemical and physical properties of the solids or sediments and chemicalsinvolved, and the mineral or organic components of sediments, dissolved organicmatter and the major cations in solution may be involved in the adsorption reaction(Spark and Swift, 2002).

The Yellow River, as the second longest river of China, is noted for its high sedi-ment concentration and thus sediments’ effect on water quality must be considered.In recent years, increasing wastewaters, derived from point sources (industries andliving) and non-point sources (insecticides, fertilizers, waste residues, and landfills),are discharged into the Yellow River. There are numerous hazardous pollutants inthese wastewaters, which may pose a severe threat on the river ecosystem. This pa-per focuses on the adsorption behavior of BPA on the sediment of the Yellow Riverand relevant factors that may affect the adsorption. The results are of significanceto analyze and assess the transportation and transformation of BPA in water andsediment systems.

2. Materials and Methods

2.1. REAGENTS AND MATERIALS

All standards and chemicals used were of the highest purity commercially available.Purified water used in experiments was made by Milli-Q Gradient System (Milli-pore, USA). HPLC-grade methanol (Scharlau, Belgium), BPA (purity 97%, ACROSORGANICS, Geel Belgium) and standard of BPA (purity 98.5%, D-86199 Augs-burg Germany) were all purchased from J&K Chemical (Belgium). All the reagentsand solutions were stored in the dark at 4 ◦C to prevent photochemical degradation.

The solid samples used in this study were collected at Tong Guan, San Menxia,and Hua Yuankou sites of the Yellow River in August 2001. The samples wereair dried, grieved and screened into 0.063 mm. The characteristics and the mineralcomponents of sediments are shown in Tables I and II respectively. Total organiccarbon (TOC), chemical composition and grain size of the sediments were analyzedusing Muti 3000 TOC/TN analyzer (Analytic Jena, Germany), ICP (Jarvell-Ash,ICAP-9000, America), and FRITSCH A22 laser particle size analyzer (FRITSCH,Germany) respectively.

2.2. SAMPLE PREPARATION

Proper amount of sediment was added into a 250 mL triangular flask, and 150 mLpure water and 10–50 µL BPA solution (33.6 µg mL−1) were added and mixed.The concentration range of BPA (C0) is 2 to 12 ng mL−1; All the equilibrium

ADSORPTION OF BISPHENOL A 355

TABLE I

Characteristics of sediments at different sites in the Yellow River

Chemical components (%)

Sample d50 (mm) CaO MgO K2O Na2O SiO2 Al2O3 MnO P2O5 Fe2O3 TOC

TS 0.048 7.456 2.077 2.263 1.214 60.775 8.750 0.115 0.098 4.680 0.667

SS 0.048 6.604 1.762 2.023 1.685 66.970 7.633 0.119 0.194 3.712 0.316

HB 0.058 5.518 1.494 1.999 2.014 70.580 7.115 0.164 0.103 3.814 0.123

TB 0.050 5.905 1.562 2.065 1.920 70.570 7.214 0.122 0.280 3.288 0.125

SB 0.104 6.091 1.639 2.063 1.917 68.540 7.145 0.162 0.137 4.434 0.109

TS = Tong Guan suspended solid, SS = San Menxia suspended solid, TB = Tong Guan bottomsediment, SB = San Menxia bottom sediment, HB = Huan Yuankou bottom sediment.

experiments were carried out in water-bath shaker for 2 h at 25 ± 1 ◦C, and thenkept for 12 h. After equilibration, the suspensions were filtered through 0.45 µmglass fiber membrane. The filtrates (100 mL) were percolated through a BondElut-C18 SPE columns (200 mg, 3 mL, America), conditioned with 3 mL methanol and3 mL pure water, and subsequently washed with 4 mL of methanol. Finally, theextraction samples were evaporated to dryness using a flow of N2 and redissolved in1 mL methanol. Duplicate samples are conducted in this research, and the relativeerror is less than 10%.

2.3. LC-MS/MS ANALYSIS

A HP 1100 LC/MSn Trap SL System consisting of a series 1100 HPLC and trap massspectrometer equipped with electrospray interface (ESI) was used to separation andquantification of BPA. Chromatography was performed using a Zorbax EclipseXDB-C18 (150 × 2.1 mm) reversed-phase HPLC column. The BPA was elutedwith 45% solvent A (100% water) and 55% solvent B (100% methanol) in 10 min,and the flow rate was 0.4 mL min−1.

The MSD was tuned automatically using built-in calibrating delivery system.Operating parameters of ESI source were optimized in MRM mode using flowinjection analysis of BPA. Optimum conditions for the BPA analysis were as fol-lows: Capillary 3500 V, Nebulizer 35.0 psi, Dry Gas 8.0 L min−1, Dry Temperature330 ◦C.

3. Results and Discussion

3.1. ANALYTICAL METHOD OF LC-MS/MS

The analytical determination of BPA from surface and wastewater commonly usesof GC-MS or GC-MS/MS (Yamamtoto and Yasuhara, 1999, 2002; Belfroid et al.,


2002), HPLC (Fromme et al., 2002; Kubo et al., 2003; Yoon et al., 2003), andeach analytical technique has issues regarding pretreatment requirements, com-pound recoveries, detection limits, and compound specificities. However, LC-MSor LC-MS/MS is a selective and sensitive method for determination of BPA indrinking water, surface water, wastewater, and in liver and muscle tissue from arelevant aquatic fish species (Pedersen and Lindholst, 1999).

When MSn detector for n > 2 is used to analyze organic chemicals, quantitativeanalysis is often conducted with the mass spectrum of fragment ions (n = or > 2)to decrease background noises and develop a sensitive method. The extractive ionchromatography (EIC) of fragment ion m/z 212 and the fragment mass spectrumof BPA with a scan range of m/z 100–350 are shown in Figure 1. In addition tothe precursor ion, [M-H]− m/z 227, three fragment ions (m/z 212, 153, 133) canbe detected. The m/z 212 fragment probably resulted from a cleavage of one of theCH3 groups is the main fragment ion of BPA, so quantitative analysis was carriedout using MS/MS mode for the ion m/z 212. The retention time of the m/z 212fragment is 5.8 min. The calibration curve of BPA consisted of five points at theconcentrations of 27.8, 101.8, 305.5, 672.0, 1680.0 ng mL−1. Calibration curve wasgenerated using linear regression analysis with all values weighted equally, and theR2 of the calibration curve was >0.999. The limit of detection was determined ata signal-to-noise ratio (S/N) >3. The limit of quantification for BPA in water wasapproximately 0.16 ng mL−1, and the recovery of the samples is within the rangeof 80 to 120%.

x104

100 125 150 175 200 225 250 275 300 325

133 153

212

227

0.00

0.25

0.50

0.75

1.00

1.25

m/z

x104

0 1 2 3 4 5 6 7 8 Time (min)

EIC 212 m /z

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Inte

nsit

y

Figure 1. Fragment mass spectrum and EIC of bisphenol A.


3.2. ADSORPTION ISOTHERMS OF BPA

Adsorption of a chemical from solution to a solid phase can be described by usingthe Freundlich equation, which defines a nonlinear relationship between the amountadsorbed and the equilibrium solution concentration:

S = K f C1/ne

where S is the concentration of a chemical adsorbed by the solid sample (mg kg−1);K f is the Freundlich sorption coefficient; Ce is the equilibrium solution concen-tration (mg L−1) and 1/n is a power function related to the sorption mechanism.When the value of n is unity, we have the simple linear isotherm:

S = KdCe

where Kd is the sorption coefficient (L kg−1).The adsorption isotherm of BPA on bottom sediment at the site of San Menxia

(SB) in the Yellow River is given in Figure 2. The adsorption isotherm of the bottomsediment is of ‘S’ shapes demonstrating a slow increase initially and then a quickincrease of the adsorption amount with increasing equilibrium BPA concentration.The experimental data are fit to neither the linear isotherm (R2 = 0.8226) nor thenonlinear Freundlich isotherm (R2 = 0.7332), which is different from the resultsin previous studies. The same result was obtained for the suspended sediment ofSan Menxia. Ying et al. (2003) and Fent et al. (2003) used the nonlinear Freundlichisotherm to describe the BPA sorption on sediments and soils, and Freundlichisotherm parameters were fit to the experimental data of adsorption of BPA onpowered activated carbon (Yoon et al., 2003).

An adsorption isotherm of a chemical depends on the physiochemical propertiesof the chemical and the sorbent. The pH of the sediment from the Yellow River

0

10

20

30

40

50

0 3 6 9 12

Equilibrium concentration (ng/mL)

Ads

orpt

ion

amou

nt (

ng/g

)

T reated SB

SB

Figure 2. Adsorption isotherms of BPA on SB and treated SB (water/sediment = 30/1).


is alkaline (pH 7.5–8.5) due to its high carbonate content, and BPA has greaterwater solubility at alkaline pH values due to its disassociation constants, pKa 9.6to 10.2 (Staples et al., 1998). BPA dissolved predominantly in the water at lowerconcentrations, and is adsorbed by sediments at higher concentrations. Therefore,the adsorption isotherms of the solid samples in the Yellow River are of an ap-proximate ‘S’ type. The adsorption data suggest a modest adsorption of BPA onsediment, which is comparable to the reported values (Ying et al., 2003).

To analyze the effect of the carbonate on the BPA adsorption, carbonate in thebottom sediment of San Menxia was eliminated with acetic acid (Loeppert et al.,1984). Compared with the SB (Figure 2), the adsorption amount of BPA on treatedSB increases about 9 ng g−1 on average and the adsorption data can be described byboth the linear isotherm (R2 = 0.9402, Kd = 4.116) and the nonlinear Freundlichisotherm (R2 = 0.9345, K f = 6.248, n = 1.278). As shown in Table II, the carbonate(calcite) content of the solid samples in the Yellow River is from 6% to 17.5%, whichis of importance to the adsorption of BPA. The elimination of carbonate decreasesthe pH of the water-sediment system (pH 5.5–6.0), consequently increases theadsorption owing to the decreasing solubility of BPA at lower pH.

3.3. ADSORPTION OF BPA ON SAMPLES FROM DIFFERENT SITES

The adsorption amount of BPA measured on different solid samples are in thefollowing order TS>SS>SB>HB≈TB (Figure 3). The Total organic carbon (TOC)of different samples are in the order of TS>SS>TB≈HB>SB according to thecharacteristics of the solid samples (Table I), and the TOC of the suspended solidsare higher than those of bottom sediments evidently. For the suspended solids, theadsorption amount of BPA correlates with TOC, and it is contrary for the bottomsediments. The same results were reached at two different water-sediment ratios.

The adsorption of BPA on sediments may be affected by many factors. Con-centrations of target contaminants (nonylphenol (NP), octylphenol (OP), BPA, and

Figure 3. Adsorption of BPA on samples of different sites (C0 = 11.2 ng mL−1).


TAB

LE

II

Min

eral

com

pone

nts

ofse

dim

ents

atdi

ffer

ents

ites

inth

eY

ello

wR

iver

Min

eral

com

pone

nts

(%)

Sam

ple

Mon

tmor

illon

iteC

hlor

iteK

aolin

iteIl

lite

Qua

rtz

Feld

spar

Plag

iocl

ase

Cal

cite

Dol

omite

Am

phib

ole

TS

5.0

2.0

7.0

20.5

25.5

5.0

15.5

17.5

1.5

0.5

SS1.

52.

54.

013

.525

.017

.025

.57.

02.

51.

5

HB

1.0

2.5

4.0

11.0

31.5

11.0

27.5

6.0

2.0

3.5

TB

1.0

1.5

3.5

14.0

25.5

17.5

23.5

6.0

4.5

3.0

SB1.

02.

53.

511

.526

.517

.023

.56.

03.

55.

0


polychlorinated biphenyls (PCBs)) are not related to TOC (Khim et al., 1999). Forsoils that have higher organic matter levels (>5%), the mobility of the pesticides hasbeen related to TOC, and with the nature of the organic matter <5% TOC has littleinfluence on sorption processes (Spark and Swift, 2002). However, the adsorptionof chemicals may be related to both TOC and minerals, and the interactions ofmineral-mineral and mineral-organics can decrease the number of adsorption sitesof the sediment or soil (Bekbolet et al., 1999; Spark and Swift, 2002). Barriusoet al. (1992) showed that the adsorption of chemicals is related not only to the totalorganic matter of soils but also to the dissolved organic matter (DOM) in the waterand soil system.

The adsorption amount of BPA on the suspended solids with higher TOC contentin the Yellow River is positively correlated with the TOC and grain size (Table I).The adsorption amount of BPA on the bottom sediments is negatively correlatedwith the TOC and grain size, which may be resulted from: (1) The adsorptionof BPA on the bottom sediments may be related to the Ferric minerals due tothe complexation among the dissolved Fe3+ ion, organic matter, and BPA; (2)The adsorption of BPA may be related to DOM. The proportions of dissolvedorganic carbon (DOC/TOC) for the solid samples are shown in Figure 4. The DOCproportion of TS is lower than that of SS, and the DOC proportions of the bottomsediments are in the following order: HB≈TB>SB. This order is corresponding tothat for BPA adsorption that shows a negative correlation with the DOC proportionfor either the suspended solids or bottom sediments at different sampling locations.The DOM is endogenous (water soluble and humic compounds directly extractedfrom sediment) (Barruiso et al., 1992). BPA, which interacts with organic matter,will react with both the soluble and solid phase fractions, therefore, competitiveeffects, the reversibility of these two types of interaction, will govern the distributionof the BPA between the solid and soluble phases of the organic matter. Thus, theadsorption amount of BPA on SB with lower DOC proportion is higher than thoseof HB and TB evidently.

Figure 4. Proportion of dissolved organic matter (water/sediment = 20/1).


Figure 5. Effect of metal ions on the BPA adsorption (SS, water/sediment = 50/1, C0 =6.72 ng mL−1).

3.4. EFFECTS OF IONS ON BPA ADSORPTION

Different ions have different effects on the adsorption of BPA on solid samples(Figure 5). The adsorption amount of BPA increases with increasing Ca2+ anddecreases with increasing K+ within the ion concentration range of 0–4 mmol L−1.Furthermore, Ca2+ and K+ have greater effects on the adsorption of BPA for higherion concentrations (>2 mmol L−1). In the previous study, increasing the ionicstrength caused the adsorption of 2,4-dichlorophenoxy (2,4-D) to increase on soils,and had no significant effect on the adsorption of atrazine and isoproturon (Sparkand Swift, 2002).

The adsorption isotherms of BPA also change after adding the metal ions(Figure 6). The experimental data were subjected to regression analysis using a non-linear Freundlich isotherm and linear isotherm, and the parameters and correlation

0

15

30

45

60

75

90

0 2 4 6 8 10Equilibrium concentration (ng/mL)

Ads

orpt

ion

amou

nt (

ng/g

) Ca2+Pure waterK+

Figure 6. Effect of metal ions on the adsorption isotherms of BPA (SS, water/sediment = 25/1, ionconcentration = 4 mmol L−1).


TABLE III

Adsorption parameters of BPA

Freundlich isotherm Linear isotherm(S = K f C1/n

e ) (S = KdCe)

Metal ions K f n R2 Kd R2

Pure water 8.869 1.245 0.6032 6.963 0.8009

Ca2+ 18.41 1.740 0.7579 9.122 0.8389

K+ 8.367 1.448 0.4323 5.936 0.6402

coefficients (R2) of the adsorption isotherms are given in Table III. Adding Ca2+

and K+ can increase and decrease the BPA adsorption respectively, which is con-sistent with the above results (Figure 5). Furthermore, the correlation coefficientsincrease after adding the Ca2+, which is contrary to those of adding K+.

The interactions between moleculars involved in adsorption are Van der Waalsinteractions, hydrogen bonding, charge transfer, ion-bonding, direct and inducedion-dipole, dipole-dipole interactions and chemisorption (Bekbolet et al., 1999).BPA exists as charged species at alkaline pH values, so could engage in ion-bondingas well as the other bonding mechanisms referred to above. In addition, soil or sed-iment organic matter tends to exhibit predominantly negatively charged adsorptionsurfaces.

There may be two respects for the positive effect of Ca2+ on BPA adsorption. Onone hand, the charge interaction of the BPA ionic species with the negatively chargedsediment mineral and organic matter surfaces is more likely involve interaction withcationic species such as Ca2+ in salt bridge arrangements (Spark and Swift, 2002).On the other hand, increasing Ca2+ concentration may decrease the solubility ofcarbonate in the sediment, which results in the decrease of the pH in reactionsystems. So the solubility of the BPA decreases and adsorption increases.

Different from Ca2+, K+ is monovalent. It cannot act as salt bridge betweenorganic matter and BPA, but can bond with BPA in the solution, which will decreasethe adsorption amount of BPA.

3.5. EFFECT OF WATER-SEDIMENT RATIO ON BPA ADSORPTION

The adsorption proportion of BPA decreases with increasing water-sediment ratio(Figure 7). However, the adsorption proportion for suspended solid declined fasterthan that for bottom sediments from San Menxia, whilst both reach to nearly thesame value as the water-sediment ratio exceeds 75. The decrease of the water-sediment ratio results in greater difference of the elimination abilities between thesuspended solid and bottom sediment for contaminants. Therefore, the removal ofpollutants by the suspended solids and bottom sediments is of significance to the


0

6

12

18

24

30

0 20 40 60

Water-sediment ratio

Ads

orpt

ion

pro

port

ion

(%)

80

SS SB

Figure 7. Effect of water-sediment ratio on BPA adsorption (C0 = 4.48 ng mL−1).

improvement of water quality in the Yellow River, which is characterized with highsediment concentration.

4. Conclusions

(1) The extent of adsorption of BPA depends on the nature and properties of thesediment and the BPA. The adsorption isotherms of BPA are different from thosein other studies due to the high carbonate content of the sediments in the YellowRiver. BPA adsorption on treated sediment increases and the experimental dataare fit to both the linear and the nonlinear Freundlich isotherms due to theelimination of the carbonate.

(2) The adsorption of BPA is related to the total organic matter and dissolved or-ganic matter, and negative correlation is observed between adsorption amountsand dissolved organic carbon proportions for the suspended solids and sedi-ments respectively.

(3) Divalent and monovalent ions have different effects on the adsorption ofBPA.

Acknowledgement

Financial support is from the major state basic research program of the People’sRepublic of China under the Grant No. G1999043603.

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adsorption of bisphenol a on sediments in the yellow

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