Chemosphere xxx (2014) xxx–xxx

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Chemosphere

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S2O82�/UV-C and H2O2/UV-C treatment of Bisphenol A: Assessment

of toxicity, estrogenic activity, degradation products and results in realwater

http://dx.doi.org/10.1016/j.chemosphere.2014.06.0200045-6535/� 2014 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Tel.: +90 212 285 6579.E-mail address: tolmez@itu.edu.tr (T. Olmez-Hanci).

Please cite this article in press as: Olmez-Hanci, T., et al. S2O82�/UV-C and H2O2/UV-C treatment of Bisphenol A: Assessment of toxicity, estrogenic a

degradation products and results in real water. Chemosphere (2014), http://dx.doi.org/10.1016/j.chemosphere.2014.06.020

Tugba Olmez-Hanci a,⇑, Duygu Dursun a, Egemen Aydin a, Idil Arslan-Alaton a, Binhan Girit a, Luigi Mita b,Nadia Diano b,c, Damiano G. Mita b, Marco Guida b,d

a Istanbul Technical University, Civil Engineering Faculty, Environmental Engineering Department, 34469 Maslak, Istanbul, Turkeyb I.N.B.B. – National Laboratory on Endocrine Disruptors, Via Pietro Castellino 111, 80131 Napoli, Italyc Seconda Università di Napoli, Department of Experimental Medicine, Via de Crecchio 7, 80138 Napoli, Italyd Università di Napoli Federico II, Department of Biology, Via Cinthia ed. 7, 80126 Napoli, Italy

a r t i c l e i n f o

Article history:Received 30 December 2013Received in revised form 15 May 2014Accepted 11 June 2014Available online xxxx

Handling Editor: J. de Boer

Keywords:Bisphenol AAcute toxicityYeast Estrogen Screen (YES) assayS2O8

2�/UV-C and H2O2/UV-C treatmentsDegradation productsReal freshwater matrix

a b s t r a c t

The performance of S2O82�/UV-C and H2O2/UV-C treatments was investigated for the degradation and

detoxification of Bisphenol A (BPA). The acute toxicity of BPA and its degradation products was examinedwith the Vibrio fischeri bioassay, whereas changes in estrogenic activity were followed with the YeastEstrogen Screen (YES) assay. LC and LC–MS/MS analyses were conducted to determine degradation prod-ucts evolving during photochemical treatment. In addition, BPA-spiked real freshwater samples were alsosubjected to S2O8

2�/UV-C and H2O2/UV-C treatment to study the effect of a real water matrix on BPAremoval and detoxification rates. BPA removal in pure water was very fast (67 min) and complete viaboth H2O2/UV-C and S2O8

2�/UV-C treatment, accompanied with rapid and significant mineralization ratesranging between 70% and 85%. V. fischeri bioassay results indicated that degradation products being moretoxic than BPA were formed at the initial stages of H2O2/UV-C whereas a rapid and steady reduction intoxicity was observed during S2O8

2�/UV-C treatment in pure water. UV-C treatment products exhibiteda higher estrogenic activity than the original BPA solution while the estrogenicity of BPA was completelyremoved during H2O2/UV-C and S2O8

2�/UV-C treatments parallel to its degradation. 3-methylbenzoic and4-sulfobenzoic acids, as well as the ring opening products fumaric, succinic and oxalic acids could beidentified as degradation products. BPA degradation required extended treatment periods (>20 min)and TOC removals were considerably retarded (by 40%) in the raw freshwater matrix most probablydue to its natural organic matter content (TOC = 5.1 mg L�1). H2O2/UV-C and S2O8

2�/UV-C treatment inraw freshwater did not result in toxic degradation products.

� 2014 Elsevier Ltd. All rights reserved.

�1

1. Introduction

Bisphenol A (2,2-bis(4-hydroxyphenyl)propane; abbreviated asBPA herein), a potential endocrine disrupting compound (EDC), hasbeen widely used in the production of epoxy resins and polycar-bonate plastics, employed in food and drink packaging applica-tions, baby bottles and dental sealants (Staples et al., 1998). Ithas been reported that BPA is ubiquitous in the environment,including surface water, groundwater and treated drinking water(Umar et al., 2013). In natural waters, BPA is usually present atlower concentrations (<0.01–1.9 lg L�1), however, landfill leachate

concentrations as high as 17 mg L have been detected (Stapleset al., 1998; Yamamoto et al., 2001). Several studies indicate thatBPA might result in adverse health effects, such as human prostatecancer, cardiovascular diseases, diabetes mellitus type 2, hormonalimbalance and liver enzyme abnormalities, in addition to repro-duction and developmental effects, neurochemical and behavioraleffects (Wetherill et al., 2002; vom Saal and Hughes, 2005;Signorile et al., 2010). The widespread existence of BPA in theaquatic environment, at low but environmentally relevant levels,implies that conventional water and wastewater treatment tech-nologies are not sufficiently effective for BPA removal (Chenet al., 2006). Consequently, advanced remediation techniques haveto be applied for efficient BPA removal from the contaminatedenvironment including water, wastewater, sewage sludge, sedi-ments and soils (Mohapatra et al., 2010; Avila et al., 2014).

ctivity,

2 T. Olmez-Hanci et al. / Chemosphere xxx (2014) xxx–xxx

Advanced oxidation processes (AOPs) have received great atten-tion and academic interest in recent years as complementarymethods to conventional water treatment or as alternative treat-ment strategies for industrial wastewater prior to discharge intosewage or into receiving water bodies (Parsons, 2004). There is agrowing interest in investigating the use of ultraviolet (UV) irradi-ation and UV based AOPs for treatment of EDCs (Chen et al., 2006;Gultekin and Ince, 2007; Huang and Huang, 2009). The effective-ness of direct UV-C photolysis is governed by the absorption spec-tra of the contaminant and the quantum yield, the addition ofhydrogen peroxide (H2O2) or persulfate (S2O8

2�) to generate highlyactive free radicals such as hydroxyl (HO�) and sulfate (SO4

��) oftensignificantly lowers the UV dose required for oxidation as com-pared to direct photolysis (Antoniou et al., 2010; Gao et al., 2012;Olmez-Hanci and Arslan-Alaton, 2013).

Activation of symmetrical peroxides such as H2O2 and S2O82�

under UV-C radiation results in the formation of two HO� and SO4��,

respectively (Eqs. (1) and (2)) through the homolytic cleavage of theperoxide (–O–O–) bond (Baxendale and Wilson, 1957; Mark et al.,1990; Anipsitakis and Dionysiou, 2004):

H2O2 þ hm! 2HO� U ¼ 1:0 ð1Þ

S2O2�8 þhm!2SO��4 U¼1:4 ðde-oxygenatedÞ; 1:8 ðoxygen saturatedÞ ð2Þ

Both of these radicals are extremely active and short-lived(10�3 ls for HO� and 30–40 ls for SO4

��) due to their high reductionpotentials (Eo = 1.89–2.72 eV for HO� and Eo = 2.5–3.1 eV for SO4

��;Pikaev and Zolotarevskii, 1967; Buxton et al., 1988; Neta et al.,1988).

During the application of AOPs, the main concern relates to theformation of various degradation products that can potentially bemore toxic, estrogenic and persistent than the original compound(Ioan et al., 2007; Li et al., 2007). Thus, the identification of degra-dation products accompanied with a comprehensive toxicityassessment becomes important when deciding for the feasibilityand ecotoxicological risk of an oxidative treatment application(Huang and Huang, 2009; Rizzo, 2011; Catapane et al., 2013). Inorder to increase the reliability of toxicity assessment, especiallyif EDCs and their degradation products are questioning, bioassayscovering different modes of toxic action (e.g. estrogenicity ornon-specific toxicity) must be used. In recent works examiningoxidation and the corresponding removal of estrogenic activityassociated with EDCs via AOPs, a consistency between removal ofestrogenic activity, toxicity and parent compound abatementswas discovered (Chen et al., 2006; Neamt�u and Frimmel, 2006;Frontistis et al., 2011).

The presence of carbonate species (HCO3�, CO3

2�), natural organicmatter (NOM) and other organic and inorganic compounds in nat-ural water matrices might significantly affect the efficiency of AOPs(Trovó et al., 2009; Sánchez-Polo et al., 2013). Moreover, the degra-dation products formed during the application of AOPs in pure andnatural water might be different and consequently their ecotoxico-logical behavior might differ as well (Trovó et al., 2009; Aydin,2014). It is not exactly known how EDCs will behave in real watermatrices during photochemical treatment; probably different thanin pure water. From the practical point of view it would be of inter-est to investigate treatability of EDCs in real water samples (Fatta-Kassinos et al., 2011).

In the present study the treatability of BPA via H2O2/UV-C andS2O8

2�/UV-C was comparatively evaluated. Changes in acute toxic-ity and estrogenic activity patterns were studied by employing twodifferent bioassays; namely the Vibrio fischeri (V. fischeri) test pro-tocol and the Yeast Estrogen Screen (YES) assay. Liquid chromatog-raphy-tandem mass spectrometry-mass spectrometry (LC–MS/MS)analysis was carried out to identify the BPA degradation products.Moreover, carboxylic acids were quantified via high performance

Please cite this article in press as: Olmez-Hanci, T., et al. S2O82�/UV-C and H2O2

degradation products and results in real water. Chemosphere (2014), http://dx

liquid chromatography (HPLC) to enable comparison of reactionpathways of the selected treatment processes. In the final part ofthe study, a series of S2O8

2�/UV-C and H2O2/UV-C experiments wereconducted in raw freshwater spiked with BPA to elucidate thetreatability and detoxification behavior of BPA in real watermatrices.

2. Materials and methods

2.1. Materials

BPA (228 g mol�1; C15H16O2; CAS No: 80-05-7, purity: 99.9%)and potassium persulfate (K2S2O8; purity P99.5%) were purchasedfrom Sigma–Aldrich (USA) and used as received. Hydrogen perox-ide (H2O2; 35% w/w) of analytical grade and acetonitrile of chro-matographic grade were obtained from Merck (Germany).Aqueous BPA solutions were prepared with distilled water. Ultra-pure water for the chromatographic measurements was preparedwith an Arium 611UV water purification system (Sartorius AG,Germany). All other chemicals required for analytical and experi-mental procedures were at least of analytical grade.

2.2. The raw freshwater sample

Raw (untreated) freshwater sample was obtained from a localwater treatment plant of the Istanbul Metropolitan Municipality.Raw freshwater sample was shipped in 25 L plastic bottles andstored in a cool room at 4 �C until the experiments were per-formed. The environmental characterization of the raw freshwatersample is shown in Table 1. TOC and absorbance at 254 nm (UV254)constitute a significant indication of the NOM present in raw fresh-water. The experimental conditions for raw freshwater samplespiked with 20 mg L�1 BPA were similar to those carried out inpure water however the initial pH was the natural pH of raw fresh-water (8.6).

2.3. The UV-C photoreactor and experimental procedure

UV-C, H2O2/UV-C and S2O82�/UV-C treatment experiments were

conducted at room temperature (25 ± 2 �C) in an octagonal photo-chemical reaction chamber (diameter: 30 cm) equipped with a dig-itally controlled thermometer, a chronometer and a magneticstirrer. The chamber consisted of a maximum of six UV-C lamps(8 W each), with three of them being placed on two (left and right)reactor walls. The maximum emission band of the UV-C lamps was253.7 nm. The UV-C light fluency was determined as 2.27 W L�1

via H2O2 actinometry (Nicole et al., 1990). All experiments wererun in a 2500 mL-capacity cylindrical quartz reactor that was con-tinuously stirred at a constant rate of 100 rpm with a magnetic stirbar from the reactor bottom to keep the reaction mixture mixed.No temperature control was provided since the low pressure UV-C lamp used in the present work did not heat up during the exper-iments. 20 mg L�1 (88 lM) of BPA aqueous solutions were treatedat pH 6.5 in all experiments based on preliminary baseline exper-iments, where oxidant concentration, pH and photochemical treat-ment time were optimized (Olmez-Hanci et al., 2013). Sampleswere taken at regular time intervals for up to 120 min and ana-lyzed for BPA, total organic carbon (TOC), S2O8

2� or H2O2 and pH.Although the initial BPA concentration investigated was extremelyhigh as compared to the concentrations typically detected in waterand wastewater, it was decided to select a high BPA concentrationto enable accurate kinetic, toxicological and analytical assessmentof BPA and its degradation products. All experiments were done atleast in duplicate and average values were used in presenting theresults.

/UV-C treatment of Bisphenol A: Assessment of toxicity, estrogenic activity,.doi.org/10.1016/j.chemosphere.2014.06.020

Table 1Environmental characterization of the raw freshwater sample.

Parameter Unit Value

TOC mg L�1 5.1Alkalinity mg CaCO3 L�1 124Hardness mg CaCO3 L�1 116Color Pt–Co 10Turbidity NTU 1.5SS mg L�1 bdla

pH – 8.6UV254 – 0.0795UV280 – 0.0640UV400 – 0.0085UV436 – 0.0063Cl� mg L�1 25.5F� mg L�1 0.11NO2� mg L�1 bdla

NO3� mg L�1 1.6

SO42� mg L�1 13

PO43� mg L�1 bdla

BPA mg L�1 bdla

a Below the detection limit.

T. Olmez-Hanci et al. / Chemosphere xxx (2014) xxx–xxx 3

2.4. Analytical procedures

2.4.1. BPA analysisBPA was quantified with an Agilent 1100 Series HPLC equipped

with a Diode-Array Detector (DAD; G1315A, Agilent Series) set at214 nm. A C18 Symmetry column (3.9 mm � 150 mm; 5 lm parti-cle size; Waters, USA) was employed as a stationary phase, whilethe mobile phase was a mixture of acetonitrile/water used at aratio of 50/50 (v/v). The flow rate and temperature of the columnwere set as 1.0 mL min�1 and 25 �C, respectively. The instrumentdetection and quantification limit of BPA for an injection volumeof 50 lL was calculated as 70 lg L�1 and 210 lg L�1, respectively.

2.4.2. Vibrio fischeri bioassayThe acute toxicity toward the luminescent bacteria V. fischeri

was measured during UV-C, H2O2/UV-C and S2O82�/UV-C treat-

ments in pure and raw freshwater spiked with BPA using a com-mercial assay kit marketed as BioTox™ (Aboatox Oy, Finland)according to the test protocol ISO 11348-3 (2007). Prior to theassay the pH and salinity of all samples was adjusted to 7.0 ± 0.2and 2% (w/v), respectively. After mixing 500 lL of untreated orphotochemically treated BPA solutions with 500 lL luminescentbacterial suspensions, the light emission after 15 min contact timewas measured at a temperature of 15 �C. Percent relative inhibitionrates were calculated on the basis of a toxicant-free control. A posi-tive control sample with potassium dichromate was also includedfor each test and all bioassays were run in triplicate. In order toeliminate their positive effect on toxicity measurements, resid-ual/unreacted H2O2 or S2O8

2� in the reaction solution was removedwith sodium thiosulfate (Merck; Germany) and enzyme catalase(made from Micrococcus lysodeikticus; Fluka; Sweden), respec-tively. Control samples were prepared for catalase and thiosulfateexactly at the concentration used to remove the above mentionedoxidants. Their presence in the test solution did not cause any sig-nificant bioluminescence inhibition (<5%).

2.4.3. YES bioassayThe estrogenic activity of BPA samples in pure water before and

after UV-C, H2O2/UV-C and S2O82�/UV-C treatments was deter-

mined by YES bioassay. The yeast strain used in the YES test wasSaccharomyces cerevisiae RMY326. This strain contains the humanestrogen receptor a (gEPa) amd an estrogen-responsive element(ERE) bound to the reporter gene lacZ encoding for the enzymeb-galactosidase (Liu et al., 1999). The yeast cells were grown over-

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degradation products and results in real water. Chemosphere (2014), http://dx

night at 26 �C by shaking in minimal medium (Yeast NitrogenBase) and enriched with a solution of amino acids and glucose.After 24 h, cells were counted in a Bürker chamber and a specificaliquot of the culture was diluted in fresh minimal medium. Theobtained suspension was incubated, for 16–18 h, in the presenceof the samples to be tested (50% v/v). Each sample and different17b-estradiol concentrations, as positive control, were assayed intriplicate and error bars representing standard deviation aredepicted in figures. Control samples for the used catalase and thio-sulfate concentrations were also assayed. As the negative control,the pure water used for all experiments was employed. Then, yeastcells were collected by serial centrifugations at 4000 rpm for 5 minin Z-buffer (30 mM Na2HPO4�12H2O, 20 mM NaH2PO4�H2O, 5 mMKCl, 0.5 mM MgSO4�7H2O) plus a 0.025% b-mercaptoethanol,CH2Cl2 and SDS 0.1%. The b-galactosidase activity was determinedby the addition of 700 lL of ONPG (4 mg mL�1 in Z-buffer). Thechromogenic reaction was stopped by the addition of 500 lL of1 M Na2CO3. Thereafter, cell debris was removed by centrifugationat 14000 rpm for 2 min, and the absorbance of the sample at420 nm was measured, normalized for the cell growth of samples(OD600), and expressed in Miller units (MU) using the followingformula (Miller, 1972);

MU ¼ ðOD420 � 1000Þ=ðt � V � OD600Þ ð3Þ

where t is the time of chromogenic reaction before stopping (min);V the volume of culture used in the assay (mL); OD420 and OD600 =optical density at 420 and 600 nm, respectively.

2.4.4. Degradation products analysesLC–MS/MS analysis was carried out using Thermo Electron Cor-

poration Accela ultra performance liquid chromatography (UPLC)coupled with a TSQ Quantum Access triple quadrupole tandemmass spectrometer (MS) and a electrospray ionizer. Firstly, all sam-ples were introduced to the MS by means of the MS syringe pumpat negative ionization full can mode (spray voltage = �3000 V,sheath gas pressure = 15 arb., ion sweep gas pressure = 2 arb., aux-iliary gas pressure = 5 arb., capillary temperature = 270 �C, tubelens offset = �75). Ions between 30 m/z and 400 m/z were scannedthrough direct infusion of the samples. Possible transformationproducts were picked from full-scan spectra of the samples. Inthe second phase, the samples were injected to a Waters SymmetryC18 column (3.9 mm � 150 mm; 5 lm particulate size) with a gra-dient elution. Acetonitrile and 10 mM ammonium acetate wereused as mobile phase at a flow rate of 400 lL min�1. The injectionvolume was 25 lL. At the beginning of the gradient elution, aceto-nitrile was 50% and kept at this ratio for 2 min, followed by anincrease to 90% in 8 min and kept at this ratio for 3.5 min. Finally,the acetonitrile concentration was decreased to 50% in 0.1 min andkept at this ratio for 6.5 min. Potential degradation products werescanned throughout each run using single ion monitoring (SIM)mode with 0.002 s scan time, 0.01 m/z scan width and 0.4 half-value width (FWHM) resolution. In the last phase, MS/MS transi-tions of the possible transformation products were determinedusing the same chromatographic conditions. MS/MS transitionscould be recorded successfully for each selected possible transfor-mation product since they were separated chromatographically.Different collision energy values were applied to obtain differentMS/MS transition spectra of the possible transition products andthese transitions. Comparison of the obtained MS/MS spectra andMassbank LC–MS library was used to propose transformation ofBPA during studied oxidation processes (Horai et al., 2010).

The concentrations of carboxylic acid products were monitoredvia HPLC. An Acclaim OA (4 � 250 mm, 5 lm; Dionex Corporation,USA) analytical column was used for the identification of C1–C7aliphatic and aromatic carboxylic acids with the mobile phase con-sisting of sodium sulfate (100 mM) aqueous solution at pH 2.65

/UV-C treatment of Bisphenol A: Assessment of toxicity, estrogenic activity,.doi.org/10.1016/j.chemosphere.2014.06.020

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4 T. Olmez-Hanci et al. / Chemosphere xxx (2014) xxx–xxx

(adjusted with methanesulphonic acid). The flow rate and injectionvolume were 0.6 mL min�1 and 50 lL, respectively. The organicacids were qualified via DAD at 210 nm and the column tempera-ture was set as 30 �C.

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2.4.5. Other measurementsTOC was measured on a Shimadzu VPCN analyzer (Japan)

equipped with an autosampler by catalytic oxidative combustionat 680 �C, using an infrared detector. An Orion (USA) 720 + modelpH-meter was used for pH measurements. Residual H2O2 andS2O8

2� concentrations were traced by employing the iodometricmethod according to Wahba et al. (1959) and Official Methods ofAnalysis (1980), respectively. The UV absorbance of the pure andraw freshwater samples was measured on a Perkin Elmer Lambda25 spectrophotometer in 1 cm quartz cuvettes. Anion analysiswas conducted using a Dionex ICS-1500 ion chromatography unitequipped with a conductivity detector, a Dionex IonPac AG14A(4 � 50 mm) guard column and a Dionex IonPac AS14A(4 � 250 mm) analytical column. The ion chromatography unitwas operated in auto-suppression mode with 1 mM sodium bicar-bonate/8 mM sodium carbonate eluent at a flow rate of 1 mL min�1.

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Fig. 1. UV-C (a) H2O2/UV-C (b) and S2O82�/UV-C (c) treatment of aqueous BPA.

Experimental conditions: BPA = 20 mg L�1 (88 lM); TOC = 16 mg L�1; Oxidantdose = 2.5 mM; initial reaction pH = 6.5; Applied UV-C dose = 21 W h L�1.

3. Results and discussion

3.1. H2O2/UV-C and S2O82�/UV-C treatment of BPA

In order to assess the capacities of H2O2/UV-C and S2O82�/UV-C

treatment processes to degrade BPA and its organic carbon content,experiments were conducted with 20 mg L�1 (88 lM) aqueous BPAsolutions at an initial oxidant concentration and pH of 2.5 mM and6.5, respectively. Selection of these experimental reaction condi-tions was based on preliminary baseline experiments that wereconducted to establish most suitable oxidant concentration andreaction pH to enhance BPA treatment by H2O2/UV-C and S2O8

2�/UV-C processes (Olmez-Hanci et al., 2013).

Fig. 1 displays the time dependent changes in BPA and TOCremoval efficiencies for direct UV-C photolysis (a), H2O2/UV-C (b)and S2O8

2�/UV-C (c) treatment experiments which were conductedin order to evaluate the degradation pattern of BPA. The evolutionof the TOC content of degradation products (TOCDP; in mg L�1)being calculated by subtracting the organic carbon content comingfrom the remaining BPA (OCBPA; organic carbon equivalent of resid-ual BPA; in mg L�1) from the measured TOC (in mg L�1) were alsoshown in Fig. 1. As it is evident in Fig. 1(a), direct UV-C photolysisof BPA was slow and hence incomplete, resulting in an overall BPAremoval of 52% after 120 min.

In principle, complete mineralization of organic pollutants maybe achieved by means of UV-C photolysis. However, this wouldrequire extended irradiation times and large energy quantities. Itis generally expected that degradation (photolysis) products mightbe more problematic from a toxicological point of view, like in thecase of hydroxylamines (Huber et al., 2003), phenols, quinones car-boxylic acids and aldehydes (Toor and Mohseni, 2007). Thus, theoxidation efficiency measured in terms of the TOC parameter mightbe more important than the removal of the parent compound due toecotoxicological safety concerns. As expected, for a degradationprocess carried out in the absence of any enhancing oxidant and/or (photo)catalyst, no significant TOC removal was observed duringtreatment (Molkenthin et al., 2013). Furthermore, TOCDP graduallyincreased during the course of UV-C treatment supporting evidenceof the formation and subsequent accumulation of degradationproducts. Different from UV-C photolysis, BPA removal was veryfast and complete in a few min during H2O2/UV-C treatment. TOCremoval also proceeded rapidly; a gradual decrease was observedresulting in 85% TOC removal. After complete degradation of BPA,

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degradation products and results in real water. Chemosphere (2014), http://dx

the TOC content of the degradation products (TOCDP) reached theirhighest value of 13.8 mg L�1 and the removal of TOCDP coincidedwith the measured TOC. As it can be also followed from Fig. 1(c),BPA removal was complete after 5 min treatment for the S2O8

2�/UV-C process. As in the case of H2O2/UV-C oxidation, TOC graduallydecreased and the overall, final TOC removal efficiency of 70% wasreached at the end of 120 min treatment. Residual S2O8

2� concentra-tions followed a similar trend to TOC removal patterns; after120 min treatment time, S2O8

2� was completely consumed (datanot shown). After 5 min, where BPA was entirely converted to itsdegradation products, TOCDP concentration peaked at a level of13.5 mg L�1 and decreased steadily to 4.4 mg L�1 after 120 min.During photochemical treatment, oxidant abatement was also fol-lowed (not shown data). H2O2 and S2O8

2� were totally consumedin 60–90 and 120 min, respectively, indicating that sufficientamounts of oxidants to produce HO� and SO4

�� were available inthe reaction solution during treatment.

Under the studied reaction conditions, BPA and TOC removalsas well as S2O8

2� and H2O2 consumption rates followed pseudo

/UV-C treatment of Bisphenol A: Assessment of toxicity, estrogenic activity,.doi.org/10.1016/j.chemosphere.2014.06.020

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Fig. 2. Evolution of V. fischeri toxicity during UV-C, H2O2/UV-C and S2O82�/UV-C

treatment of BPA. Experimental conditions as in Fig. 1.

T. Olmez-Hanci et al. / Chemosphere xxx (2014) xxx–xxx 5

first-order kinetics with high correlation coefficients (R2 P 0.96).Table 2 presents the apparent first-order BPA and TOC removalsas well as S2O8

2� and H2O2 consumption rate constants k (in min�1)calculated for photochemical treatment in pure water (PW) andraw freshwater (RW). From Table 2 it can be seen that BPA removalrates were similar for both processes whereas TOC and oxidantabatements rates were slightly higher for H2O2/UV-C process.

3.2. Acute toxicity results

The toxicity analysis of the BPA solutions during different stagesof UV-C, H2O2/UV-C and S2O8

2�/UV-C treatments in pure water wasmonitored with V. fischeri (Fig. 2). Toxicity results indicated thatthe untreated BPA sample caused an inhibitory effect of 75%. Nev-ertheless, as UV-C photolysis progressed, a general reduction in theinhibitory effect of BPA was evident speaking for the fact that UV-Cphotolysis products of BPA were not more toxic than the originalBPA solution. However photo-intermediates generated duringUV-C photolysis were not further transformed and thus, they,and their associated toxicity (64%), remained in solution at theend of the 120 min treatment (corresponding to a UV dose of21 W h L�1). V. fischeri appeared to be very sensitive; reacting rap-idly to the decrease in BPA concentration as well as formation ofdegradation products during H2O2/UV-C treatment. As can be seenfrom Fig. 2, a prompt decrease down to 14% (5 min) was observed,followed by a re-increase to 94% after 30 min treatment. Beyondthis treatment period the inhibitory effect decreased to practicallynon-toxic levels (�1–3% relative inhibition) after 120 min oxida-tion due to the ultimate oxidation of BPA degradation productsthat resulted in over 80% TOC abatement. From the findings it isapparent that rapid BPA degradation accompanied with efficientTOC elimination during H2O2/UV-C treatment also decreased theacute toxicity of BPA and its degradation products. In case ofS2O8

2�/UV-C treatment, the toxic effect of BPA solution rapidlydecreased to practically non-toxic levels (<4%) after 10 min treat-ment and did not change or increase thereafter which was inagreement with the observed, progressive mineralization. Fromthe toxicity profiles it may be inferred that relatively less biotoxicdegradation products were formed during S2O8

2�/UV-C treatmentof BPA under the investigated experimental conditions as com-pared with H2O2/UV-C. Similar results were also reported bySánchez-Polo et al. (2013) who investigated the effectiveness ofoxidation processes based on UV radiation (UV, UV/H2O2, UV/K2S2O8, and UV/Na2CO3) to remove BPA from different watermatrices. In their study the highest inhibition toward V. fischeriwas obtained with the UV/H2O2 system, indicating the formationof degradation byproducts that are more toxic than BPA.

3.3. YES bioassay results

No estrogenic or toxic activity was detected in the wateremployed for solutions, and in catalase and thiosulfate concentra-tions used for experiments (data not shown). The estrogenic activ-ity decreased rapidly to non-detectable levels parallel to BPAremoval when AOPs were employed to treat BPA in pure water(Fig. 3). No substantial differences between the two AOPs were evi-dent in terms of effectiveness in removing estrogenic activity,

Table 2Apparent first-order abatement rate constants for BPA, TOC and oxidants in purewater (PW) and raw freshwater (RW).

Process kBPA (min�1) kTOC (min�1) kOx (min�1)

PW RW PW RW PW RW

H2O2/UV-C 0.5065 0.1875 0.0155 0.0048 0.0415 0.0111S2O8

2�/UV-C 0.5202 0.2685 0.0099 0.0024 0.0298 0.0050

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degradation products and results in real water. Chemosphere (2014), http://dx

which was expected considering the similarities in the removalefficiencies and kinetics being observed in terms of BPA and TOCabatements. A similar pattern in estrogenic activity decreasing par-allel to BPA removal was evidenced in previous related work (Chenet al., 2006; Neamt�u and Frimmel, 2006; Frontistis et al., 2011). Onthe other hand, in agreement with the results obtained for directUV-C treatment resulting in only moderate (52%) BPA and insignif-icant TOC (<5%) removals, UV-C photolysis was not effective indecreasing the estrogenic activity. Moreover, UV-C photolysis ledto formation of some degradation products exhibiting an estro-genic activity being higher than that of the untreated BPA sample.Experimental results highlight the importance of using the AOPsboth S2O8

2�/UV-C and H2O2/UV-C and not UV-C treatment inremoving the estrogenic activity of biorefractory of emerging pol-lutants including BPA.

3.4. Degradation products

29 Ions were selected as possible transformation products foreach oxidation process after detailed review of full-scan chromato-grams of the UV-C, S2O8

2�/UV-C and H2O2/UV-C treated BPA in purewater. However, most of the selected ions either could not beobserved or observed even in control samples during the SIM modeinjections.

Possible degradation products for UV-C photolysis were 133 m/z,149 m/z, 213 m/z, 218.9 m/z, and 308.9 m/z with 2.3 min, 5.52 min,3.60 min, 4.47 min, and 3.60 min retention times, respectively.133 m/z was observed starting from the 1st minute of the UV-C pho-tolysis and reached its maximum peak area after 30 min treatment.149 m/z was observed with very small peaks reaching its maximumat 30 min. 213 m/z appearance started after 60 min treatment andreached its maximum peak area in 120 min. 218.9 m/z was observedafter 10 min treatment and reached its maximum peak area in30 min. The maximum peak area for 308.9 m/z was present in the90 min sample and first appeared after 7 min (Supporting Informa-tion Fig. S1). Spectra of MS/MS transitions for possible transforma-tion products of BPA during UV-C treatment were provided inSupporting Information Figs. S2–S5. No matches were found forthese spectra in Massbank Library. 135 m/z, 194.6 m/z, 201 m/z,and 276 m/z with 2.60 min, 4.35 min, 2.32 min, and 2.16 min reten-tion times, respectively were the possible transformation productsfor H2O2/UV-C process. 135 m/z was formed 1st minute of the pro-cess and was observed in all samples. It was reached its maximumpeak area in 30 min. 194.6 m/z was observed between 1 and5 min. 201 m/z was observed between 3 and 60 min with a maxi-mum peak area in 10 min sample. 276 m/z was observed between3 and 30 min (Supporting Information Fig. S6). It might be proposed

/UV-C treatment of Bisphenol A: Assessment of toxicity, estrogenic activity,.doi.org/10.1016/j.chemosphere.2014.06.020

0

200

400

600

800

1000

1200

-11 -10 -9 -8

MU

Log [M]

E2

0

20

40

60

80

100

120

140

160

0 1 3 5 7 10 30 60 90 120

Est

roge

nic

acti

vity

red

ucti

on (

%)

Time (min)

UV-C

(a)

(b)

-H2O2/ UV C /UV-S2O82- C

Fig. 3. Estrogenic activity of estradiol expressed in MU (a) and changes inestrogenic activity of the reaction solutions during photochemical treatments (b).Estrogenic activity reductions were expressed as percent MU with respect to t = 0.Experimental conditions as in Fig. 1.

6 T. Olmez-Hanci et al. / Chemosphere xxx (2014) xxx–xxx

that 135 m/z is 3-methylbenzoic acid thanks to very good match(score = 0.94) with Massbank library (Fig. 4). 201 m/z was proposedas 4-sulfobenzoic acid with a match with Massbank library having0.88 score (Fig. 5). No Massbank library match could be found withthe MS/MS spectra of other ions (Supporting Information Figs. S7–S9). Since no MS/MS transitions can be found for the S2O8

2�/UV-Cprocess samples, any transformation product cannot be proposedfor this process.

In previous studies it was reported that oxidative cleavage ofaromatic compounds led to ring opening products consisting ofshort chain aliphatic acids such as maleic and fumaric acids as wellas simpler organic acids including acetic, formic, glyoxylic and oxa-lic acids (Skoumal et al., 2008; Karci et al., 2012). Oxalic and formicacids are regarded as the ultimate carboxylic acids because theyare directly oxidized to carbon dioxide (Garcia-Segura et al.,2012). In the present study HPLC analysis of H2O2/UV-C andS2O8

2�/UV-C treatment of BPA in pure water revealed the genera-tion of oxalic, succinic and fumaric acids. As aforementioned, UV-C photolysis was found to be inefficient in BPA degradation intoring opening products, as verified by the absence of carboxylicacids. Oxalic acid, being the common short-chain carboxylic acidfor the studied treatment processes was formed at 30–40 min oftreatment (Fig. 6). In case of H2O2/UV-C treatment, oxalic acidremained in the effluent at the end of 60 min treatment. In con-trast, succinic and fumaric acids were only generated during theinitial stages of H2O2/UV-C treatment only at relatively low levels.Conclusively, the presence of some common carboxylic acidsevolving as later-stage photochemical degradation at varying con-centrations products speak for similarities in the reaction path-ways of S2O8

2�/UV-C and H2O2/UV-C processes.

3.5. S2O82�/UV-C and H2O2/UV-C treatment of BPA in raw freshwater

Normalized BPA and TOC abatements being obtained duringapplication of S2O8

2�/UV-C and H2O2/UV-C processes in pure water

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degradation products and results in real water. Chemosphere (2014), http://dx

(PW) and raw freshwater (RW) are shown in Fig. 7(a) and (b),respectively. In addition, previously shown in Table 2 comparesapparent first-order rate constants in terms of BPA, TOC and oxidantabatements for raw freshwater with rate constants obtained in purewater. From Fig. 7 it is obvious that, as expected, BPA degradationwas appreciably faster in pure water than in raw freshwater; whensubjected to S2O8

2�/UV-C treatment, BPA removal in pure water wasvery rapid and complete in less than 4 min, whereas 99% removaltook 10 min in the raw freshwater matrix. In the case of H2O2/UV-C oxidation, BPA degradation carried out in pure water andraw freshwater was complete within 7 min and 20 min, respec-tively, implying that the raw water components cause a significantinhibition in BPA oxidation rates. Controversial to BPA abatements,appreciably faster TOC removal rates were observed for H2O2/UV-Ctreatment as compared to S2O8

2�/UV-C process. Similar results werereported for surfactant treatment, where S2O8

2�/UV-C appeared tobe more selective for the removal of the parent compound ratherthan for mineralization of oxidation intermediates (Arslan-Alatonet al., 2013; Olmez-Hanci et al., 2014). This retardation is also evi-dent from the TOC results of the same treatment experiments. Infact, inhibition rates were more pronounced for the TOC parameter.TOC removal efficiency decreased from 70% to 28% after 120 minS2O8

2�/UV-C treatment, whereas TOC removals dropped from 85%to 45% for H2O2/UV-C treatment for the same reaction period(Fig. 7(b)). The decrease in treatment efficiencies is thought to bea consequence of decreased UV-C photolysis of oxidants (S2O8

2�,H2O2) being hindered by the NOM content of the raw freshwatermatrix (TOC = 5.1 mg L�1; UV254 = 0.0794 cm�1) that competed forUV irradiation. In addition it should be mentioned that inhibitionof oxidation rates is also attributable to HO� and SO4

�� scavengingeffect of the raw freshwater components. Considering the low alka-linity, chloride, phosphate and sulfate content of the raw freshwa-ter sample (Table 1), the major parameter causing reducedtreatment performance is thought to be its NOM (TOC) content.

According to Table 2, BPA removal rates decreased by a factor ofapproximately 2 and 3 in raw freshwater for S2O8

2�/UV-C and H2O2/UV-C processes, respectively. Results in terms of the TOC parame-ter was also negatively affected; 4 and 3-fold reduction in TOCremoval rates were found for S2O8

2�/UV-C and H2O2/UV-C treat-ments, respectively. In the S2O8

2�/UV-C process S2O82� consumption

rate constant decreased from 0.0298 min�1 to 0.0050 min�1

whereas the same constant decreased from 0.0415 min�1 to0.0111 min�1 for the H2O2/UV-C process. These results impliedthat S2O8

2�/UV-C process was more selective in terms of BPAremoval and vulnerable in terms of ultimate oxidation thanH2O2/UV-C process.

Different degradation patterns resulting in different ecotoxico-logical responses depending on the water matrix have been shownby several researchers (Zwiener and Frimmel, 2000; Trovó et al.,2009; Richard et al., 2014). Thus the effect of S2O8

2�/UV-C andH2O2/UV-C treatments on the acute toxicity of BPA in raw freshwa-ter samples was also elucidated in the present study. Fig. 8 displayschanges in acute toxicity of raw freshwater samples spiked withBPA (20 mg L�1) for the S2O8

2�/UV-C and H2O2/UV-C treatments.Initial inhibition percentage of raw freshwater samples spiked withBPA was found as 71%, thus being very close to values obtained intoxicity tests with pure water samples. As can be seen from Fig. 8the acute toxicity evolutions showed similar trends for S2O8

2�/UV-Cand H2O2/UV-C treated raw freshwater BPA samples; a generalreduction in the relative inhibitions was observed being faster forS2O8

2�/UV-C process. Complete detoxification was achieved withthe S2O8

2�/UV-C and H2O2/UV-C treatments in raw freshwater,where relatively poor treatment efficiencies were obtained com-pared to pure water. Despite the H2O2/UV-C oxidation of BPA inpure water, where fluctuations were realized in inhibition values,no increase in toxicities was observed in raw freshwater. The

/UV-C treatment of Bisphenol A: Assessment of toxicity, estrogenic activity,.doi.org/10.1016/j.chemosphere.2014.06.020

Fig. 4. Massbank match of 135 m/z and 3-methylbenzoic acid.

Fig. 5. Massbank match of 201 m/z and 4-sulfobenzoic acid.

T. Olmez-Hanci et al. / Chemosphere xxx (2014) xxx–xxx 7

inhibitory effect occurred only in pure water and not in raw fresh-water with BPA might be associated to the matrix effect (Zwienerand Frimmel, 2000; Trovó et al., 2009; Richard et al., 2014). As a

Please cite this article in press as: Olmez-Hanci, T., et al. S2O82�/UV-C and H2O2

degradation products and results in real water. Chemosphere (2014), http://dx

consequence of competing reactions and different degradationmechanism, the H2O2/UV-C treatment of BPA in raw freshwaterdid not lead the formation of toxic degradation products.

/UV-C treatment of Bisphenol A: Assessment of toxicity, estrogenic activity,.doi.org/10.1016/j.chemosphere.2014.06.020

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 1 2 3 4 5 7 10 20 30 40 50 60

Con

cent

rati

on (

mg

L-1

)

Treatment time (min)

Oxalic Acid -H2O2/UV-COxalic Acid -S2O8

2-/UV-CSuccinic Acid -H2O2/UV-CFumaric Acid -H2O2/UV-C

Fig. 6. Evolution of carboxylic acids during H2O2/UV-C and S2O82�/UV-C treatment

of BPA. Experimental conditions as in Fig. 1.

S2O82-/UV-C - RW

S2O82-/UV-C - PW

H2O2/UV-C - RW H2O2/UV-C - PW

S2O82-/UV-C - RW

S2O82-/UV-C - PW

H2O2/UV-C - RW H2O2/UV-C - PW

0.0

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BPA

/BPA

o

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S2O82-/UV-C - RW

S2O82-/UV-C - DW

H2O2/UV-C - RW

H2O2/UV-C - DW

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 5 10 15 20

0 10 20 30 40 50 60 70 80 90 100 110 120

TO

C/T

OC

o

Treatment Time (min)

S2O82-/UV-C - RW

S2O82-/UV-C - DW

H2O2/UV-C - RW

H2O2/UV-C - DW

Fig. 7. Changes in normalized BPA (a) and TOC (b) concentrations during H2O2/UV-C and S2O8

2�/UV-C treatments of BPA in raw freshwater. Experimental conditions:BPA = 20 mg L�1 (88 lM); TOC = 21 mg L�1; oxidant dose = 2.5 mM; initial reactionpH = 8.6; applied UV-C dose = 21 W h L�1.

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100 110 120

Inhi

biti

on (

%)

Treatment Time (min)

H2O2/UV-C S2O82-/UV-C

Fig. 8. Evolution of V. fischeri toxicity during H2O2/UV-C and S2O82�/UV-C treatment

of BPA in raw freshwater samples. Experimental conditions as in Fig. 7.

8 T. Olmez-Hanci et al. / Chemosphere xxx (2014) xxx–xxx

4. Conclusions

The present work aimed at comparatively investigating thetreatability of BPA with the H2O2/UV-C and S2O8

2�/UV-C processesin pure and raw freshwater samples. The study mainly focusedon examination of toxicity and estrogenic activity changes beingobserved during photochemical treatment. Besides, identificationand quantification of photochemical degradation products viaLC–MS/MS and HPLC analyses was targeted. The following conclu-sions could be drawn from the obtained experimental results:

� UV-C photolysis of BPA solution resulted in poor BPA degrada-tion and TOC removals. This was also ecotoxicologically con-firmed by the V. fischeri and YES bioassays. Hence, advanced

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degradation products and results in real water. Chemosphere (2014), http://dx

oxidation processes have to be applied for the efficient treat-ment and complete detoxification of aqueous BPA.� H2O2/UV-C treatment in pure water resulted in a rapid and com-

plete BPA degradation accompanied with high TOC removalsexceeding 80%. Acute toxicity tests revealed that V. fischeri werevery sensitive to photochemically induced changes in the reac-tion solution. The YES test results indicated an abrupt reductionof the estrogenic activity within the first 5 min of photochemicaltreatment. As long as the organic carbon content of BPA wastransformed to various degradation products, V. fischeri toxicitykept on fluctuating, but decreased as TOC removal progressed.� S2O8

2�/UV-C treatment in pure water also brought about rapidand complete BPA as well as TOC removals. Different fromH2O2/UV-C oxidation, the inhibitory effect of BPA on V. fischeridecreased gradually, almost parallel to BPA abatement andremained stagnant thereafter. Concerning estrogenic activity,there were no significant differences, in terms of effectiveness,between the two AOPs.� 3-Methylbenzoic and 4-sulfobenzoic acid were proposed as the

H2O2/UV-C degradation products. Although at different concen-trations, oxalic acid was generated as the common ring openingproduct of H2O2/UV-C and S2O8

2�/UV-C treatments whereas suc-cinic and fumaric acids were additionally detected during H2O2/UV-C treatment.� The raw freshwater matrix (TOC: 5.1 mg L�1; pH: 8.6; alkalin-

ity: 124 mg L�1 CaCO3) exhibited a negative effect on BPA andTOC abatements. The reduced degradation and mineralizationof BPA might be attributable to the high natural organic mattercontent that significantly hindered UV-C absorption by S2O8

2�

and H2O2 but also acted as a SO4��/HO� scavenger. Nevertheless,

the raw freshwater samples were found to be non-toxic afterBPA treatment. The water matrix seemed to be playing a signif-icant role in the toxicity changes in the presence of BPA and itsdegradation products.

The presence of BPA in the environment is likely to disturb theecosystems and negatively affect human health. Thus, the need fordeveloping advanced processes for water and wastewatertreatment remains of major environmental concern. Comparisonof different photochemical processes on the basis of their treat-ment and detoxification performance for emerging contaminantsfound in real water and wastewater remains a challenging task.

Acknowledgements

The financial support of the Scientific and TechnologicalResearch Council of Turkey (TUBITAK) under Project No:

/UV-C treatment of Bisphenol A: Assessment of toxicity, estrogenic activity,.doi.org/10.1016/j.chemosphere.2014.06.020

T. Olmez-Hanci et al. / Chemosphere xxx (2014) xxx–xxx 9

111Y257 is gratefully acknowledged. The authors are thankful toProf. Dr. Is�ık Kabdas�lı for her support during Vibrio fischeri analysis.Idil Arslan-Alaton is a member of the Academy of Science, Turkey.

Appendix A. Supplementary material

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.chemosphere.2014.06.020.

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