Accepted Manuscript Advanced oxidation of iodinated X-ray contrast media in reverse osmosis brines: The influence of quenching Sara P. Azerrad , Shirra Gur-Reznik , Lilly Heller-Grossman , Carlos G. Dosoretz PII:

S0043-1354(14)00413-8

DOI:

10.1016/j.watres.2014.05.041

Reference:

WR 10695

To appear in:

Water Research

Received Date: 24 March 2014 Revised Date:

22 May 2014

Accepted Date: 25 May 2014

Please cite this article as: Azerrad, S.P., Gur-Reznik, S., Heller-Grossman, L., Dosoretz, C.G., Advanced oxidation of iodinated X-ray contrast media in reverse osmosis brines: The influence of quenching, Water Research (2014), doi: 10.1016/j.watres.2014.05.041. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

Advanced oxidation of iodinated X-ray contrast media in reverse osmosis brines: The ACCEPTED MANUSCRIPT influence of quenching

a

RI PT

Sara P. Azerrad, Shirra Gur-Reznik, Lilly Heller-Grossman and Carlos G. Dosoretz*

Faculty of Civil & Environmental Engineering and Grand Water Research Institute, Technion-

SC

Israel Institute of Technology, Haifa, Israel.

M AN U

*Corresponding author: Faculty of Civil and Environmental Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel. Tel.: +972 4 8294962; fax: +972 4 8228898.

AC C

EP

TE D

E-mail address: [email protected] (C.G. Dosoretz).

1

1

Abstract

2

Among the main restrictions for the implementation of advanced oxidation processes (AOPs) for

3

removal of micropollutants present in reverse osmosis (RO) brines of secondary effluents account

4

the quenching performed by background organic and inorganic constituents. Natural organic matter

5

(NOM) and soluble microbial products (SMP) are the main effluent organic matter constituents.

6

The inorganic fraction is largely constituted by chlorides and bicarbonate alkalinity with sodium

7

and calcium as main counterions. The quenching influence of these components, separately and

8

their mixture, in the transformation of model compounds by UVA/ TiO2 was studied applying

9

synthetic brines solutions mimicking 2-fold concentrated RO secondary effluents brines. The

SC

RI PT

ACCEPTED MANUSCRIPT

results were validated using fresh RO brines. Diatrizoate (DTZ) and iopromide (IOPr) were used as

11

model compound. They have been found to exhibit relative high resistance to oxidation process and

12

therefore represent good markers for AOPs techniques.

13

Under the conditions applied, oxidization of DTZ in the background of RO brines was strongly

14

affected by quenching effects. The major contribution to quenching resulted from organic matter (≈

15

70%) followed by bicarbonate alkalinity (≈30%). NOM displayed higher quenching than SMP in

16

spite of its relative lower concentration. Multivalent cations, i.e., Ca+2, were found to decrease

17

effectiveness of the technique due to agglomeration of the catalyst. However this influence was

18

lowered in presence of NOM.

19

Different patterns of transformation were found for each model compound in which a delayed

20

deiodination was observed for iopromide whereas diatrizoate oxidation paralleled deiodination.

TE D

EP

AC C

21

M AN U

10

22

Keywords: Advanced oxidation processes, radicals quenching, brines desalination, synthetic brines,

23

secondary effluents, titanium dioxide oxidation, iodinated X-ray contrast media.

24

2

25

1. Introduction

26

Safe reuse of treated wastewater in agriculture is of vital importance especially in countries with

27

scarcity of natural water resources. Reuse and discharge of conventionally treated wastewater

28

results in release of micropollutants into the environment that can contaminate ground/surface

29

water, accumulate in soils and perhaps adsorb into crops (Ternes and Hirsch, 2000; Kormos et al.,

30

2011; Shenker et al., 2011). High pressure-driven membranes such reverse osmosis (RO) applied to

31

treat wastewater effluents represent an useful technology that confines micropollutants into brines

32

(Kimura et al., 2004; Košutić et al., 2007; Oulton et al., 2010; Gur-Reznik et al., 2011a) while

33

releasing high quality water for unrestricted irrigation. However, a proper treatment of brines is

34

necessary before releasing them into de environment (Westerhoff et al., 2009; Gur-Reznik et al.,

35

2011b; Zhou et al., 2011).

36

Iodinated X-ray contrast media (ICM) used in medicine for imaging of organs or blood vessels are

37

metabolically stable in the body and are eliminated via urine or feces (Pérez and Barceló, 2007).

38

Conventional wastewater treatment plants (WWTPs) are not able to remove them effectively from

39

wastewater, and therefore they are expected contaminants in treated effluents (Ternes and Hirsch.,

40

2000; Carballa et al., 2004; Oulton et al., 2010; Kormos et al., 2011). Because of their chemical

41

stability and high solubility, ICM have been found at µg/L level in municipal effluents and at ng/L

42

level in surface water (Pérez and Barceló, 2007). ICM were found at almost undetectable levels in

43

groundwater. Reported concentrations of diatrizoate and iopromide (in µg/L) in surface water

44

ranged between 0.05 to 0.23, in municipal effluents from 0.25 to 9, and in groundwater from

45

undetectable levels to 0.05 (Putschew et al., 2000; Ternes and Hirsch, 2000; Ternes and Joss, 2006;

46

Pérez and Barceló, 2007). In RO brines results are expected to increase according to the recovery

47

ratio, up to 10-fold for the case of 90% recovery higher than those obtained in effluents. ICM were

48

chosen as model compounds in this work due to their multiple halogenation and aromatic structure,

49

which confers them relatively high resistance to oxidation, with the additional advantage of iodine

50

as an intrinsic labeling for tracking purposes (Gur Reznik et al., 2011b; Sugihara et al., 2013).

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

3

51

Several oxidation techniques have been studied in order to remove ICM from water and wastewater

52

effluents such as non-thermal plasma (NTP) (Gur-Reznik et al., 2011b), ozonation (Ternes et al.,

53

2003; Seitz et al., 2008), electrochemical oxidation (Zwiener et al., 2009; Lütke el al., 2014) as well

54

as advanced oxidation processes (AOPs) (Doll and Frimmel, 2004; Pereira et al., 2007a; Pérez et

55

al., 2009; Malato et al., 2009; Sugihara et al., 2013). These techniques exhibited only partial

56

transformation. Although removal efficiency is strongly dependent on the conditions applied,

57

reported transformations applying UV-TiO2 oxidation in UPW were ~65% for diatrizote after 1

58

hour (k1st≈0.02 min-1) and ~70% for iopromide after 5 minutes (k1st≈0.18-0.22 min-1) (Doll and

59

Frimmel, 2004; Sugihara et al., 2013). Scavenging capacity of the water matrix is a constraint for

60

significant removal of ICM by AOPs.

61

Secondary effluent is a complex water matrix composed by a variety of organic and inorganic

62

components. The effluent organic matter (EfOM) is constituted mainly by humic-like compounds

63

originated from natural water, better known as natural organic matter (NOM) and soluble microbial

64

products (SMP) resulting from biomass activity and decay during biological treatment and to a

65

minor extent by micropollutants (Shon et al., 2006; Jarusutthirak and Amy, 2007). It has been

66

reported that SMP represent most of the chemical oxygen demand in effluents (Aquino et al., 2003)

67

and contain polysaccharides, proteins, and organic colloids as the main chemical constituents

68

(Rosenberger et al., 2006). There were a few attempts to characterize influence of EfOM as OH·

69

radical scavenger. Dong et al. (2010) reported an inverse relationship between molecular weight

70

and OH· radical scavenging, i.e., the lower the molecular weight the higher is the reactivity with

71

hydroxyl radicals. Reactivity toward OH· radicals was measured in different water sources based on

72

different water matrix characteristics such as molecular weight, polarity, SUVA, hydrophobicity

73

and fluorescence (Rosario-Ortiz et al., 2010). Lin and Lin (2007) reported a decrease in

74

photodecomposition of model compounds due to presence of humic acids in TiO2/UV system. Gur-

75

Reznik et al. (2011b) using NTP system showed decrease in first order reaction rates of two ICM,

76

iopromide (IOPr) and diatrizoate (DTZ), as the organic matter and electrical conductivity in the

77

water matrix increased. The inorganic fraction of wastewater effluent is largely formed by

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

4

78

chlorides, alkalinity (constituted mainly by bicarbonate) and sulphate with sodium and calcium as

79

main counterions, whereas phosphate, nitrate, magnesium and potassium are to a lesser extent.

80

Influence of individual inorganic ions in water matrix, especially bicarbonate, was reported to

81

decrease the oxidation of target compounds by hydroxyl radicals. Degradation and reaction rate

82

constants for chloride, carbonate, bicarbonate and phosphate with hydroxyl radicals have been

83

studied (Jayson et al., 1973; Buxton and Elliott, 1986; Abdullah et al., 1990; Liao et al., 2001;

84

Piscopo et al., 2001; Neppolian et al., 2002; Wu and Linden, 2010).

85

However, the radical scavenging capacity of individual or combined main constituents of RO

86

brines is still not well defined. The aim of the present research was to evaluate the patterns and

87

factors governing the oxidation of micropollutants present in reverse osmosis brines by UVA/ TiO2.

88

Synthetic brines comprising the main RO brines components were designed and applied to

89

understand the quenching contribution of individual and groups of constituents on the extent and

90

kinetics of oxidation of the ionic ICM diatrizoate, used as model compound. In experiments aimed

91

to determine oxidation patterns, the non-ionic ICM iopromide was also used. Results were

92

validated using fresh RO brines (2-fold concentrated secondary effluents) and ultrapure water

93

(UPW) as reference.

94

2. Material and methods

95

2.1 Materials

96

TiO2 used in the experiments was Degussa P-25. Sodium diatrizoate dihydrate and iopromide were

97

purchase from Sigma-Aldrich and U.S. Pharmacopeia, respectively with purity ≥ 99%. Fulvic acid

98

sodium salts (technical grade) and soluble potato starch (reagent grade) were purchased from

99

Sigma-Aldrich. Yeast extract was of microbiological quality (Bacto BD). Other chemicals used for

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

100

the experiments (buffer, eluents, standards) were at least of analytical grade.

101

2.2 Water matrixes

102

Experiments were performed in ultrapure water, fresh RO brines and synthetic brines. Water

103

matrixes were spiked with DTZ (~700±70 µg/L) as model compound. In experiments addressed to

5

104

determine patterns of oxidation also IOPr (~700±70 µg/L) was spiked. The chemical structure of

105

model compounds is presented in Fig. 1.

106

Reverse osmosis brines: Brines were obtained from the Technion secondary effluent desalination-

107

pilot plant with a nominal capacity of 10 m3/h, located at a commercial activated sludge-WWTP

108

(Nir Etzyon, Israel). The pilot comprises an ultrafiltration stage (~40 nm molecular weight cut off –

109

MWCO, Dow) followed by a two stages-reverse osmosis system (8” and 4” BW Toray membranes,

110

respectively) as detailed elsewhere (Gur-Reznik et al., 2011b). A schematic diagram of the

111

desalination process is presented in Fig. 2. Fresh RO brines (2-fold concentrated with respect to the

112

feed) for this study were obtained from the first stage.

113

Synthetic brines: Synthetic brines were prepared mimicking composition of stage one-RO brines.

114

Dissolved organic matter (DOM) was set to ~20±1 mg/L of which approximately 80% was

115

attributed to SMP and 20% to NOM. SMP was reconstituted adding 10.4±0.5 mg/L (as C) soluble

116

potato starch (polysaccharide) plus 5.6±0.3 mg/L (as C) yeast extract (protein) whereas NOM were

117

reconstituted as 4±0.2 mg/L (as C) humic acid-sodium salts (HA). Inorganic components were

118

added as follows: 25±3 mg/L phosphate (as KH2PO4), 31±1 mg/L nitrate (as NaNO3), 373±31

119

mg/L carbonate alkalinity (as NaHCO3) and 240±7 mg/L sulfate (as Na2SO4). To reach the desired

120

concentration of chloride as well as calcium and potassium NaCl, CaCl2 and KCl were added to

121

obtain a final solution containing 613±25 mg/L chloride, 112±15 mg/L calcium, 63±0.14 mg/L

122

potassium. In experiments focused on study the influence of anions, either combined or

123

individually, UPW was supplemented with sodium as the main counterion.

124

Ultrapure water (0.055 µS/cm electrical conductivity) was generated from double distilled water

125

through purification in a Purelab system (Elga).

126

2.3 Photocatalysis experiments

127

Experiments were carried out at room temperature in 500 ml glass reactors containing 180 ml of

128

either water matrix spiked with the model compounds, as indicated. TiO2 at 1 g/L was added and

129

stirred prior to irradiation to achieve thermodynamic adsorption equilibrium. The reactors were

130

placed in a dark chamber on a magnetic stirrer to facilitate mixing and illuminated from the top

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

6

131

with a UVA lamp (Eversun, 40W) emitting radiation between 300 and 420 nm with a maximum at

132

350 nm. UVA lamps were preheated for 20 min prior to runs. At different times, aliquots of the

133

solution were collected for analysis and immediately supplemented with excess NaHCO3 to

134

facilitate TiO2 removal, and kept in ice in the dark. Then samples were centrifuged during 20 min at

135

4000 rpm (Heraeus, Megafuge 1.0R centrifuge) and filtered with 0.45 µm syringe filter units

136

(Millipore) prior to analysis. Light intensity was measured by ferrioxalate actinometry (Hatchard

137

and Parker, 1956) and was found to be 990 µW/cm2. The UV fluence was calculated multiplying

138

the light intensity by the exposure time and it was found to be 3564 mJ/cm2 per hour of experiment.

139

2.4 Analytic techniques

140

Determination of diatrizoate, iopromide, p-chlorobenzoic acid (pCBA) and organic bound iodine

141

were performed using liquid chromatography with electrospray tandem mass spectrometry LC-MS3

142

in an Agilent 1200 HPLC system (Hewellet Packard) coupled through a ion spray interface to an

143

API 3200 triple quadrupole mass spectrometer (Applied Biosystems). Chromatography was

144

performed on a reverse-phase column LiChroCART® Purospher STAR RP-18 (Merck) endcapped

145

column (4.6 mm×15 cm) with 5 µm pore size. The compounds were detected in multiple-reaction

146

monitoring (MRM) mode. Methods for determination of diatrizoate and iopromide were similar to

147

those described by Gur-Reznik et al. (2011a). pCBA determination was performed according to

148

Vanderford et al. (2007) with some modifications, using 0.1% formic acid (v/v) in water (A) and

149

100% methanol (B) as eluents. The gradient was as follows: 5% B was held for 2 min, than

150

increased linearly to 100% during another 8 min and held for 4 min, afterwards the gradient

151

decreased linearly again to 5% and finally held for 3 min. The total run time was 19 min, the flow

152

rate was 350 µL/min with injection volume of 15 µL and the column temperature was set at 30°C.

153

The quantification limit under these conditions was 5 µg/L.

154

Organic bound iodine was determined using ion negative electrospray ionization according to

155

Putschew and Jekel (2003) with some modifications. The first quadrupole was used in single ion

156

monitoring mode and was set to m/z 126.8. The source parameters were set as follow: curtain gas

157

25 psi, temperature 600°C, spray gas (GS1) 35 psi, dry gas (GS2) 40 psi, ion spray voltage -4500,

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

7

158

declustering potential -120 V, entrance potential -10 V. The same eluents as detailed before were

159

applied in a linear gradient as follows: from 5% B to 100 % B in 7 min, held for 3 min, then back to

160

5% B in 3 min and held for 3 min. The column temperature was set at 30°C.

161

Total adsorbable iodine was measured following the procedure described by Oleksy-Frenzel et al.

162

(2000) modified as reported by Gur-Reznik et al. (2011b). Dissolved organic carbon (DOC) was

163

analyzed on a total organic carbon (TOC) analyzer (multi N/C 2000, Analytic Jena) and ultraviolet

164

absorbance (UV) at a wavelength of 254 nm (A254) was measured in a UV-visible

165

spectrophotometer (Agilent 8453 series) with a 1 cm quartz cell. Fourier transform infrared (FTIR)

166

spectra of freeze-dried samples were recorded on an FTIR (iS10 Nicolet) using Smart iTR single

167

bounce attenuated total reflectance (ATR) Diamond/ZnSe crystal.

168

Total concentration of elements (Na, Ca, P, S, K) was measured by ICP-AES (iCAP-6300, Thermo

169

Sci). Anions concentration (nitrate, sulphate, phosphate, chloride, iodide) were measured in a 881

170

compact IC Pro ion chromatograph (Metrohm), equipped with Metrohm A supp 5-150 (with 4 µm

171

pore size) column. A solution of 3.2 mM sodium carbonate and 1.0 mM sodium bicarbonate in 5%

172

acetonitrile was used as eluent. Alkalinity was measured according to standard methods 2320

173

(APHA 2005).

174

3. Results and discussion

175

3.1 Effect of operating conditions on UVA/TiO2 oxidation in UPW

176

The effect of the operating conditions on the performance UVA/TiO2 on diatrizoate transformation

177

at trace concentrations was first characterized in UPW as water matrix. The results are presented in

178

Table 1. The effect of pH and TiO2 concentration were first studied. The highest pseudo-first order

179

rate constant for diatrizoate was detected at pH 3.5 (2-folds higher than at pH 7 and 3-folds higher

180

than at pH 10). These results denote that TiO2 is more effective under acidic conditions in line with

181

previous reports (Westerhoff et al., 2009). Furthermore, under acidic conditions (pH 3.5) approx.

182

50% DTZ is present in the anion form (pKa=3.4) and TiO2, which is positively charged under

183

isoelectric point (pH 6.3), may adsorb it promoting its direct oxidation. pH values in RO brines are in

184

the range of 7.5±0.5 and for this reason the experiments were performed at pH 7. The effect of TiO2

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

8

185

concentration on the rate of DTZ oxidation was carried out in the concentration range of 0.25-2 g/L

186

(see Table 1). Increasing TiO2 concentration over 1 g/L did not show significant improvement of

187

the pseudo-first order rate constant. Therefore 1 g/L TiO2 concentration was chosen as optimal dose

188

for this work.

189

In order to evaluate the extent of quenching due to alkalinity, transformation of DTZ in UPW

190

supplied with bicarbonate alkalinity was further studied. Total alkalinity in brines can be expressed

191

as in equation (1):

192

Alktotal = [HCO3− ] + 2[CO3−2 ] + [NH3 ] +[H2 PO4− ] + 2[HPO4−2 ] + 3[PO4−3 ] + [OH − ] −[H + ]

193

Since ammonia concentration was very low in the brines used in this study whereas phosphate was

194

negligible in comparison to the carbonate system and pH of brines was 7.4 ±0.5, bicarbonate

195

alkalinity was considered the dominant specie. Bicarbonate alkalinity at four different

196

concentrations 18, 54, 159 and 413 mg/L (as CaCO3) was therefore tested. The results are presented

197

in Table 1, showing a decrease in the pseudo-first order rate constant for DTZ as alkalinity

198

increases. At concentrations above 159 mg/L changes in DTZ rate constant were very small. At

199

alkalinity of 413 mg/L approx. 80% DTZ transformation could be achieved after 3 hours run,

200

indicating that quenching due to alkalinity in UPW is approx. 20%.

201

The influence of carbonate quenching was taken into account in models in where scavenging

202

capacity of the water matrix was studied (Pereira et al., 2007a; Pereira et al., 2007b; Rosario-Ortiz

203

et al., 2010; Wu and Linden, 2010).

204

Chloride is a major ionic component in brines. In order to test the direct effect of Cl- on DTZ

205

oxidation, typical concentrations ranging from tap water to reverse osmosis brines (200-800 mg/L

206

as Cl-) were spiked into UPW at neutral pH. Pseudo-first order rate constants values slightly

207

changed among the different concentrations tested (see Table 1). The extent quenching performed

208

by chloride was approximately 2% after 3 hours experiment. Other authors also reported the slight

209

influence of chlorides in degradation of model compounds (Neppolian et al., 2002; Wang et al.,

210

2000). The influence of chloride on DTZ transformation can be explained by : (1) Chloride

211

recombines with free radicals, decreasing the amount of free radicals available to react with model

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

(1)

9

212

compounds; (2) At pH lower than TiO2 isoelectric point (~6.3), chloride compete with organic

213

compounds for active sites on the TiO2 (Piscopo et al., 2001) whereas at pH higher than isoelectric

214

point the TiO2 surface is weakly negatively charged and adsorption of chloride may be hindered

215

(Wang et al., 2000), as in our experiments (pH of RO brines was 7.4±0.5). Competence for OH·

216

radicals appears to be the main quenching mechanism performed by chloride in brines. Jayson and

217

Parsons (1973) proposed the following reactions between chloride and hydroxyl radicals:

RI PT

OH • + Cl − ↔ HOCl •−

k eq = 0.70 ± 0.13 M −1

(2)

HOCl •− + H + ↔ Cl • + H 2O

k eq = 1.6x107 M −1

(3)

Cl − + Cl • ↔ Cl2•

k eq = 1.9x105 M −1

(4)

SC

218

ACCEPTED MANUSCRIPT

3.2 DTZ oxidation in reverse osmosis-brines

220

Experiments with 2 fold-concentrated RO brines were carried out in order to determine the overall

221

scavenging capacity of the water matrix, to quantify the quenching performed by alkalinity and to

222

estimate the influence of dilution. Characteristic composition of the RO brines applied in this study

223

is presented in Table 2.

224

3.2.1 Effect of alkalinity

225

Influence of alkalinity in brines on DTZ transformation was studied removing it from the water

226

matrix by acidification (Fig. 3). Alkalinity concentrations in the raw brines applied in the different

227

experiments ranged from 290-655 mg/L (as CaCO3) corresponding to a TOC value of 20.9±3.5

228

mg/L (see Table 2). Three sets of experiments were performed: raw brines (control), brines

229

acidified to pH 3.5 in a current of N2 to strip out CO2, and brines without CO2 at neutral pH

230

(performed by pH correction of acidified brines under N2). The last two sets represent the influence

231

of pH without influence of alkalinity. The extent of DTZ transformation achieved after 3 hour

232

experiments in raw brines, pH 3.5 and pH 7 where 2%, 49% and 33%, respectively. From these

233

results can be concluded that extent of quenching due to alkalinity is roughly 30%.

234

Taken together the results from RO brines and UPW suggest that natural alkalinity is responsible

235

for about 20-30% quenching of micropollutants oxidation in brines. Our results are in line with data

236

reported in other water matrixes for other target pollutants. Neppolian et al. (2002) found a decrease

AC C

EP

TE D

M AN U

219

10

237

in degradation of Reactive Blue 4 as the concentration of carbonate ions increased. Wu and Linden

238

(2010) obtained 10-15% and 50% reduction in reaction rates of two pesticides with an addition of

239

0.5 and 10 mM of bicarbonates, respectively.

240

3.2.2 Brines dilution

241

The effect of brines dilutions was tested at two ratios, 1:2 and 1:4 in which 18% and 61% DTZ

242

transformation were achieved respectively after three hours experiment compared to only 2%

243

transformation in undiluted fresh brines (inset in Fig. 3). The 1:2 dilution which corresponds to

244

secondary effluent concentration, still displayed a high radical scavenging capacity. However, high

245

diatrizoate transformation was observed at dilution ratio 1:4, most probably due to the dilution of

246

the radical scavenger components and divalent cations present in the water matrix that are known to

247

cause agglomeration of the photocatalyst (see section 3.3.2 below). Gur-Reznik et al. (2011b) using

248

NTP system obtained approximately 42% DTZ transformation in a background of RO brines, and

249

64 and 100 % transformation at dilution ratio of 1:2 and 1:5 respectively. These results clearly

250

depict a higher influence of dilution in UVA-TiO2 than in NTP.

251

3.3 Synthetic brines experiments

252

3.3.1 Characterization of synthetic brines

253

Synthetic brines made possible the evaluation of the individual and combined scavenging capacity

254

of the main organic and inorganic components in brines. In order to evaluate its similarities to fresh

255

RO brines, synthetic brines were first optimized for their composition and characterized for their

256

ability to oxidize pCBA.

257

Functional groups similarities of organic and inorganic constituents was performed by FTIR

258

spectroscopy (Fig. 4). Fresh and synthetic brines displayed very similar spectral pattern. Peaks at

259

wavenumbers between 960-1170 cm-1 represent polysaccharides or polysaccharides-like

260

substances. A peak around 1660 cm-1 (amine I, N-C=O stretch) indicates presence of N-acetyl

261

amino sugars. Peaks between 665-910 cm-1 (amine I, amine II, N-H wag) and a peak around 1416

262

cm-1 (amide I, stretch of aromatic bonds) suggest the presence of proteins. Peaks around 1410 cm-1

263

(COH bend) and 1495 cm-1 (COO- stretching) suggest the presence of humic matter (Cho et al.,

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

11

264

1998; Jarusutthirak and Amy, 2001; Drewes and Croue, 2002; Leenheer and Rostad, 2004; Ivnitsky

265

et al., 2005; Gur-Reznik et al., 2008). Peaks around 1090 cm-1 represent sulphate and peaks around

266

1420 cm-1 and 850 cm-1 represent bicarbonates (online NIST library). These results show a good

267

correspondence between synthetic and fresh brines in terms of functional groups structure.

268

The scavenging capacity of pCBA was then determined (Fig. 5). pCBA is a compound widely used

269

to test the quenching of OH· radicals in different water matrixes. It reacts with OH· with a rate

270

constant of 5.109 M-1s-1 (Rosenfeldt et al., 2006). Steady state OH· concentration were calculated

271

from the pseudo-first order rate constant (obtained from the slope in the graph ln(pCBA)/(pCBA)0

272

vs. time) (Westerhoff et al., 2009). Experiments were performed in comparison to UPW as a blank,

273

in fresh and synthetic RO brines. pCBA was spiked at concentration of 5 µM. Both brines,

274

synthetic and fresh, displayed a relatively similar strong quenching effect on pCBA oxidation

275

compared to UPW. Indeed, while complete pCBA disappearance of UPW was attained during the

276

first 30 min, only 20 and 30% transformation was achieved after 3 h run in fresh and synthetic

277

brines, respectively. Steady state OH· concentration resulted slightly higher in synthetic brines

278

7.32x10-15 M in comparison to 4x10-15 M in fresh brines. Similarly, an inverse relationship between

279

the scavenging capacity of the water matrix and the fraction of OH· radicals available to react with

280

pCBA was reported (Rosenfeldt et al., 2006; Rosario-Ortiz et al., 2010).

281

All in all, these results show a good correspondence between synthetic and fresh brines both in

282

terms of group’s functionality and scavenging capacity.

283

3.3.2 Contribution to quenching of individual and combined brines components on DTZ

284

transformation

285

In order to evaluate the contribution of each individual component and the overall mixture on DTZ

286

oxidation, a gradual reconstitution of the synthetic brines solution was performed and compared to

287

UPW as control. The results are summarized in Fig. 6, displaying a plot of the relative DTZ

288

concentration (Ce/Co) vs. time for each case.

289

In the presence of the complete mixture of synthetic brines approx. 8% DTZ degradation was

290

achieved after 3 h of oxidation (Fig.6- left). These results are fairly well correlated to those

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

12

291

obtained with fresh RO brines, which displayed around 2% DTZ transformation. Addition of SMP

292

(16±0.8 mg/L as C) and NOM (4 ±0.2 mg/L as C)-like materials representing the main components

293

of the organic matter fraction present in treated effluent-organic matter depicted a quenching effect

294

on DTZ transformation in the order of ~70±3%. These results are well correlated with those

295

obtained using fresh brines upon alkalinity removal where quenching was found to be ~70%. These

296

results confirm that organic matter present in brines performs the strongest quenching. Humic acid

297

sodium salts representing NOM was the individual largest contributor to quenching during DTZ

298

oxidation in synthetic brines, followed by alkalinity and SMP. Although OH· radicals are

299

unselective, they display affinity for carbon double and triple bonds (Haang and Yao, 1992;

300

Westernhoff 1999). Due to their high level of aromaticity, humic acids react faster with OH·

301

radicals than proteins and polysaccharides (typical SMP-like materials constituents). Moreover, HA

302

absorbs light in the wavelength range of 200-500 nm, leading to the formation of electronically

303

excited states and photochemically induced reactions (Frimmel, 1994). In consequence, hydroxyl

304

radicals and photons preferably react with HA over SMP-like compounds. This behavior along with

305

the adsorption of HA onto the TiO2 surface explain the higher quenching capacity of NOM

306

compared to SMP-like materials, in spite of a 4–fold higher TOC concentration of the latter.

307

Though HA follow anionic-type adsorption on TiO2, non-negligible amounts of HA can adsorb

308

onto the TiO2 surface, even at pH 7, due to the complex HA structure containing several functional

309

groups, such as carboxyl and phenol, having different acid dissociation constants (Yang et al.,

310

2006). Our results showed in presence of HA a lag phase of DTZ degradation during the first 60

311

min of reaction, followed by a decrease in DTZ concentration. It was reported that initial decrease

312

in TOC followed by an increase was attributed to TOC adsorption and the formation of

313

intermediate products as result of NOM oxidation (Huang et al., 2008). In consequence, NOM

314

might compete with model compounds for active sites in TiO2 surface, reducing their reaction rates

315

(Epling and Lin, 2002). Previous studies showed that NOM from lakes decreased model

316

compounds transformation to a higher extent than commercial humic acids (Lin and Lin, 2007),

317

representing a possible increase of scavenging capacity in fresh brines in comparison to synthetic

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

13

318

brines. In summary, the main effects of NOM in the photocatalyst system include

319

deactivation/competition for active sites in the surface of the semiconductor, scavenging effects,

320

light absorption and reduction in light transmittal (Frimmel, 1994; Epling and Lin, 2002; Lin and

321

Lin, 2007).

322

Interestingly, the quenching performed individually by NOM and SMP-like materials after 3 h of

323

experiment were 25±4 and 15±6%, respectively (see Fig.6- left), suggesting a synergistic effect

324

when combined together (~70%). The synergistic effect in presence of SMP-like materials and

325

NOM together might be explained by the abovementioned interactions between HA and TiO2

326

leaving less OH· radicals available to react with the model compounds. Indeed, as can be seen from

327

Fig. 6-left, an almost identical lag phase during the first hours of experiment was observed in

328

presence of HA alone and HA together with SMP, suggesting initial adsorption of HA on TiO2

329

surface.

330

A mixture of phosphate, sulphate and nitrate (Fig. 6-right) displayed negligible quenching effect

331

and after 3 h of experiment more than 99% DTZ transformation was achieved, most probably due

332

to their relative low concentration and the fact that at pH> isoelectrical point adsorption of anions

333

onto the TiO2 surface is hindered. It has been reported that H2PO4-/HPO4 and sulphate react with

334

OH· to form HPO 4 -• and a SO4-· respectively, which are less reactive than OH· radicals

335

(Maruthamuthu and Neta, 1978; Wang et al., 2000). Influence of nitrate in model compounds

336

mineralization was reported almost insignificant even at acidic pH (Abdullah and Matthews, 1990).

337

Bicarbonate displayed the main quenching effect among all anions tested, around 80% DTZ

338

transformation was found. These results indicated that bicarbonate alkalinity is the main

339

responsible for radical scavenging among the inorganic components. When calcium was present

340

along with sodium and potassium in the anions mixture, only 21% DTZ transformation was

341

achieved (see Fig. 6-right). It has been reported that at the same ionic strength, Ca+2 exhibited a

342

stronger influence on TiO2 particles than Na+. Addition of CaCl2 leaded to a faster aggregation than

343

NaCl due to reduction of surface charges in TiO2 at pH 8. As the Ca+2 concentration increases,

344

absolute value of zeta potential decreases and hydrodynamic diameter of TiO2 increases and above

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

14

345

1 mM CaCl2 no further change in TiO2 aggregation takes place (French et al., 2009; Thio et al.,

346

2011). However, when humic acid was supplemented to a solution of 130 mg/L Ca+2 as CaCl2

347

(≈3.25 mM Ca), corresponding to RO brines concentration, the effect of Ca+2 was almost

348

completely suppressed, achieving at the end of the experiment 65% DTZ transformation (compare

349

both panels in Fig. 6). This hindering of Ca+2 effect in water containing NOM can be attributed to:

350

(a) calcium promotes high adsorption of HA onto the catalyst surface by bridging, electric double

351

layer compression or charge neutralization, (b) possible formation of chelates in solution (Fang et

352

al., 1999; Zhang et al., 2009; Thio et al., 2011). Based on these interactions and our results, it is

353

clear that the effect of Ca+2 in the presence of NOM is weaker in either fresh RO or synthetic brines

354

as compared to ultrapure water.

355

To conclude this section, our findings clearly indicate that the whole synthetic brine solution and its

356

individual components as well as quenching factors considered, cover and explain the most relevant

357

issues involved in AOP of trace chemicals in brines and related water matrixes.

358

3.4 Transformation and deiodination of diatrizoate and iopromide in UPW

359

To take advantage of intrinsic iodine label in the model compounds, transformation and

360

deiodination were tracked by different procedures. Organic bound iodine technique has been used

361

successfully to test electrochemical reduction as a selective technique to remove organic iodine

362

from X-ray contrast media (Zwiener et al., 2009). In order to gain insights regarding the

363

deiodination mechanism, DTZ oxidation was compared with IOPr (Fig. 7). The transformation

364

mechanism for diatrizoate shows predominantly decrease in DTZ with scarce presence of

365

intermediates containing organic iodine (Fig. 7-bottom). During iopromide transformation,

366

decrease in its concentration and formation of a series of intermediates containing organic iodine

367

were observed (Fig. 7-top). Peak at 7.7 min represents organic bound iodine in IOPr, whereas peaks

368

at 7, 8.2 and 8.5 min represent other organic iodine containing compounds, i.e., oxidation products.

369

Inset graphs in Fig. 7 show percentage of transformation and deiodination of IOPr and DTZ vs.

370

time (deiodination was tested using adsorbable organic iodine). DTZ displayed higher resistance to

371

oxidation. The rate of IOPr transformation resulted higher than DTZ, and after 5 min oxidation

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

15

372

IOPr reached 95% transformation whereas DTZ only 55%. Furthermore, deiodination of IOPr

373

reached 45% in 5 min and 84% in 25 min whereas DTZ showed 34 and 77% deiodination in 5 and

374

45 min, respectively. During the five first minutes in the experiment ratio

375

deiodination/transformation was higher in DTZ than in IOPr with values of 0.72 and 0.44,

376

respectively. These results suggest that in IOPr, transformation starts at side chains, whereas in

377

DTZ seems to be deiodination the predominant transformation in the initial steps.

378

Previous studies reported transformation of IOPr and DTZ in non-thermal plasma, it was found that

379

DTZ oxidation mechanism involves direct deiodination of the aromatic ring, whereas in IOPr

380

oxidation of side chains preceded ring deiodination (Gur-Reznik et al., 2011b). Lütke et al. (2014)

381

identified IOPr transformation products (TPs) in electrochemical treatment. Three different starting

382

reactions were found in the anodic compartment where oxidation took place, and only TP-681 was

383

partial deiodinated. Four DTZ transformation products were identified by Sugihara et al. (2013) at

384

oxic conditions in UVA-TiO2, two of them exhibited partial deiodination. However iodide

385

measurements showed almost a complete dehalogenation of the DTZ at each time point. These

386

results support our findings that side chain transformation in IOPr is the main initial mechanism.

387

Our results differ from those reported by Jeong et al. (2010) for treatment of DTZ and IOPr with γ

388

radiation. They identified for DTZ TP-586, in which the triiodobenzene structure remained

389

unaltered, at high relative concentration. For IOPr they found TP-789, TP-665 and TP-681 as initial

390

starting reactions, in which only TP-789 maintained the triiodinated structure unaltered. A possible

391

explanation to these differences may be other mechanism acting in γ radiation out of hydroxyl

392

attack.

393

4. Conclusions

394

This study presented a systematic characterization of the pattern and extent of quenching of the

395

major individual constituents of RO brines during TiO2 oxidation of iodinated contrast media

396

through application of a specially designed synthetic brines solution. The major contribution to

397

quenching resulted from the organic matter followed by alkalinity. Among the organic matter

398

components, NOM-like materials present in wastewater effluent displayed a higher quenching

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

16

399

compared to soluble microbial products, in spite of their 4-times lower TOC concentration. This

400

behavior can be attributed both, to the interaction, i.e., adsorption, between humic acid and TiO2

401

and the significantly higher reactivity of hydroxyl radicals with the highly aromatic HA compared

402

to proteins and polysaccharides in SMP. A synergistic effect was observed when NOM and SMP

403

were present together resulting in a net higher decrease of available OH· radicals. Ca+2 reduced

404

TiO2 effectiveness due to agglomeration of the photocatalyst; however, this influence was reduced

405

in the presence of NOM. These interactions possess high importance in effluents and brines, and

406

have to be taken into account especially in oxidation processes catalyzed by particles. The

407

quenching performed by the main brines constituents individually can be categorized in the

408

following order: NOM>alkalinity≅ SMP >Cl->(NO3+PO4-3+SO4-2). Concluding, synthetic brines

409

are a useful tool for rational characterization of quenching made by the individual background

410

components present in effluents and brines whereas iodinated contrast media are good markers for

411

evaluation of AOP oxidation potential.

412

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

Acknowledgments

414

This work was funded by the Joint German-Israeli Research Program BMBF-MOST (Contract No.

415

WT 0903/2194). The financial support of Sanofi by a research grant through the Peres Center for

416

Peace and the generous support of the Rieger Foundation are gratefully acknowledged.

AC C

EP

TE D

413

17

417

5. References

418

Abdullah, M., Low, G., Matthews, R., 1990. Effects of common inorganic anions on rates of

419

photocatalytic oxidation of organic carbon over illuminated titanium dioxide. The Journal of

420

Physical Chemistry 94(17), 6820–6825.

421

APHA, AWWA, WEF, 2005. Standard Methods for the Examination of Water and Wastewater.

422

21st ed. American Public Health Association, Washington DC, USA.

423

Aquino, S., Stuckey, D., 2004. Soluble microbial products formation in anaerobic chemostats in the

424

presence of toxic compounds. Water Research 38(2), 255–266.

425

Buxton, G., Elliott, A., 1986. Rate constant for reaction of hydroxyl radicals with bicarbonate ions.

426

International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and

427

Chemistry 27(3), 241–243.

428

Carballa, M., Omil, F., Lema, J., Llompart, M., García-Jares, C., Rodríguez, I., Gómez, M., Ternes,

429

T., 2004. Behavior of pharmaceuticals, cosmetics and hormones in a sewage treatment plant. Water

430

Research 38(12), 2918–2926.

431

Cho, J., Amy, G., Pellegrino, J., Yoon, Y., 1998. Characterization of clean and natural organic

432

matter (NOM) fouled NF and UF membranes, and foulants characterization. Desalination 118(1-3),

433

101–108.

434

Doll, T., Frimmel, F., 2004. Kinetic study of photocatalytic degradation of carbamazepine, clofibric

435

acid, iomeprol and iopromide assisted by different TiO2 materials-determination of intermediates

436

and reaction pathways. Water Research 38(4), 955–964.

437

Dong, M., Mezyk, S., Rosario-Ortiz, F., 2010. Reactivity of effluent organic matter (EfOM) with

438

hydroxyl radical as a function of molecular weight. Environmental Science and Technology 44(15),

439

5714–5720.

440

Drewes, J., Croue, J., 2002. New approaches for structural characterization of organic matter in

441

drinking water and wastewater effluents. Water Science and Technology: Water Supply 2(2), 1–10.

442

Epling, G., Lin, C., 2002. Investigation of retardation effects on the titanium dioxide

443

photodegradation system. Chemosphere 46(6), 937–944.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

18

444

Fang, H., Sun, D., Wu, M., Phay, W., Tay, J., 2005. Removal of humic acid foulant from

445

ultrafiltration membrane surface using photocatalytic oxidation process. Water Science and

446

Technology 51 (6-7), 373–380.

447

French, R., Jacobson, A., Kim, B., Isley, S., Lee, R., Baveye, P., 2009. Influence of ionic strength,

448

pH, and cation valence on aggregation kinetics of titanium dioxide nanoparticles. Environmental

449

Science and Technology 43(5), 1354-1359.

450

Frimmel, F., 1994. Photochemical aspects related to humic substances. Environment International

451

20(3): 373-385.

452

Gur-Reznik, S., Katz, I., Dosoretz, C., 2008. Removal of dissolved organic matter by granular-

453

activated carbon adsorption as a pretreatment to reverse osmosis of membrane bioreactor effluents.

454

Water Research 42(6-7), 1595–1605.

455

Gur-Reznik, S., Koren-Menashe, I., Heller-Grossman, L., Rufel, O., Dosoretz, C., 2011a. Influence

456

of seasonal and operating conditions on the rejection of pharmaceutical active compounds by RO

457

and NF membranes. Desalination 277(1-3), 250–256.

458

Gur-Reznik, S., Azerrad, S., Levinson, Y., Heller-Grossman, L., Dosoretz, C.,et al., 2011b.

459

Iodinated contrast media oxidation by nonthermal plasma: The role of iodine as a tracer. Water

460

Research 45(16), 5047–5057.

461

Haag, W., Yao, C., 1992. Rate constants for reaction of hydroxyl radicals with several drinking

462

water contaminants. Environmental Science and Technology 26(5), 1005-1013.

463

Hatchard, C., Parker, C., 1956. A new sensitive chemical actinometer. II. Potassium ferrioxalate as

464

a standard chemical actinometer. Proceedings of the Royal Society of London, Series A.

465

Mathematical and Physical Sciences 235 (1203), 518–536.

466

Huang, X., Leal, M., Li, Q., 2008. Degradation of natural organic matter by TiO2 photocatalytic

467

oxidation and its effect on fouling of low-pressure membranes. Water Research 42(4-5), 1142–

468

1150.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

19

469

Ivnitsky, H., Katz, I., Minz, D., Shimoni, E., Chen, Y., Tarchitzky, J., Semiat, R., Dosoretz, C.,

470

2005. Characterization of membrane biofouling in nanofiltration processes of wastewater treatment.

471

Desalination 185(1–3), 255-268.

472

Jarusutthirak, C., Amy, G., 2001. Membrane filtration of wastewater effluents for reuse: effluent

473

organic matter rejection and fouling. Water Science and Technology 43(10), 225–232.

474

Jarusutthirak, C., Amy, G., 2007. Understanding soluble microbial products (SMP) as a component

475

of effluent organic matter (EfOM). Water Research 41(12), 2787–2793.

476

Jayson, B., Parsons, B., Swallow, A., 1973. Some simple, highly reactive, inorganic chlorine

477

derivatives in aqueous solution. Their formation using pulses of radiation and their role in the

478

mechanism of the Fricke dosimeter. Journal of the Chemical Society, Faraday Transactions 1:

479

Physical Chemistry in Condensed Phases 69, 1597-1607.

480

Jeong, J., Jung, J., Cooper, W., Song, W., 2010. Degradation mechanisms and kinetic studies for

481

the treatment of X-ray contrast media compounds by advanced oxidation/reduction processes.

482

Water Research 44(15), 4391–4398.

483

Kimura, K., Toshima, S., Amy, G., Watanabe, Y., 2004. Rejection of neutral endocrine disrupting

484

compounds (EDCs) and pharmaceutical active compounds (PhACs) by RO membranes. Journal of

485

Membrane Science 245(1-2), 71–78.

486

Kormos, J., Schulz, M., Ternes, T., 2011. Occurrence of iodinated X-ray contrast media and their

487

biotransformation products in the urban water cycle. Environmental Science and Technology

488

45(20), 8723–8732.

489

Košutić, K., Dolar, D., Ašperger, D., Kunst, B., 2007. Removal of antibiotics from a model

490

wastewater by RO/NF membranes. Separation and Purification Technology 53(3), 244–249.

491

Leenheer, J., Rostad, C., 2004. Fractionation and characterization of organic matter in wastewater

492

from a swine-waste retention basin. US geological survey scientific investigations report, 2004-

493

5217, US geological survey, Denver, CO.

494

Liao, C., Kang, S.,Wu, F., 2001. Hydroxyl radical scavenging role of chloride and bicarbonate ions

495

in the H2O2/UV process. Chemosphere 44(5), 1193–1200.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

20

496

Lin, C., Lin, K., 2007. Photocatalytic oxidation of toxic organohalides with TiO2/UV: The effects

497

of humic substances and organic mixtures. Chemosphere 66(10), 1872–1877.

498

Lütke Eversloh, C., Henning, N., Schulz, M., Ternes, T., 2014. Electrochemical treatment of

499

iopromide underconditions of reverse osmosis concentrates-elucidation of the degradation pathway.

500

Water Research 48, 237-246.

501

Malato, S., Fernández-Ibáñez, P., Maldonado, M., Blanco, J., Gernjak, W., 2009. Decontamination

502

and disinfection of water by solar photocatalysis: Recent overview and trends. Catalysis Today

503

147(1), 1–59.

504

Maruthamuthu, P., Neta, P., 1978. Phosphate radicals. spectra, acid-base equilibria, and reactions

505

with inorganic compounds. The Journal of Physical Chemistry 82(6), 710–713.

506

Neppolian, B., Choi, H., Sakthivel, S., Arabindoo, B., Murugesan, V., 2002. Solar light induced

507

and TiO2 assisted degradation of textile dye reactive blue 4. Chemosphere 46(8), 1173–1181.

508

Oleksy-Frenzel, J., Wischnack, S., Jekel, M., 2000. Application of ion-chromatography for the

509

determination of the organic-group parameters AOCl, AOBr and AOI in water. Fresenius Journal

510

of Analytical Chemistry 366(1), 89–94.

511

Oulton, R., Kohn, T., Cwiertny, D., 2010. Pharmaceuticals and personal care products in effluent

512

matrices: A survey of transformation and removal during wastewater treatment and implications for

513

wastewater management. Journal of Environmental Monitoring 12, 1956-1978.

514

Pereira, V., Linden, K., Weinberg, H., 2007a. Evaluation of UV irradiation for photolytic and

515

oxidative degradation of pharmaceutical compounds in water. Water Research 41(19), 4413–4423.

516

Pereira, V., Weinberg, H., Linden, K., Singer, P., 2007b. UV degradation kinetics and modeling of

517

pharmaceutical compounds in laboratory grade and surface water via direct and indirect photolysis

518

at 254 nm. Environmental Science and Technology 41(5), 1682–1688.

519

Pérez, S., Barceló, D., 2007. Fate and occurrence of X-ray contrast media in the environment.

520

Analytical and Bioanalytical Chemistry 387(4), 1235–1246.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

21

521

Pérez,S., Eichhorn, P., Ceballos, V., Barceló, D., 2009. Elucidation of phototransformation

522

reactions of the X-ray contrast medium iopromide under simulated solar radiation using UPLC-

523

ESI-QqTOF-MS. Journal of Mass Spectrometry 44(9), 1308–1317.

524

Piscopo, A., Robert, D.,Weber, J., 2001. Influence of pH and chloride anion on the photocatalytic

525

degradation of organic compounds part I . Effect on the benzamide and para-hydroxybenzoic acid

526

in TiO2 aqueous solution. Applied Catalysis B: Environmental 35(2), 117–124.

527

Putschew, A., Jekel, M., 2003. Induced in-source fragmentation for the selective detection of

528

organic bound iodine by liquid chromatography/electrospray mass spectrometry. Rapid

529

communications in Mass Spectrometry 17(20), 2279–2282.

530

Putschew, A., Wischnack, S., Jekel, M., 2000. Occurrence of triiodinated X-ray contrast agents in

531

the aquatic environment. Science of the Total Environment 255:129–134.

532

Rosario-Ortiz, F., Wert, E., Snyder, S., 2010. Evaluation of UV/H2O2 treatment for the oxidation of

533

pharmaceuticals in wastewater. Water Research 44(5), 1440–1448.

534

Rosenberger, S., Laabs, C., Lesjean, B., Gnirss, R., Amy, G., Jekel, M., Schrotter, J., 2006. Impact

535

of colloidal and soluble organic material on membrane performance in membrane bioreactors for

536

municipal wastewater treatment. Water Research 40(4),710-720.

537

Rosenfeldt, E., Linden, K., Canonica, S., von Guten, U., 2006. Comparison of the efficiency of OH

538

radical formation during ozonation and the advanced oxidation processes O3/H2O2 and UV/H2O2.

539

Water Research 40(20), 3695–3704.

540

Seitz, W., Jiang, J., Schulz, W., Weber, W., Maier, D., Maier, M., 2008. Formation of oxidation by-

541

products of the iodinated X-ray contrast medium iomeprol during ozonation. Chemosphere 70(7),

542

1238–1246.

543

Shenker, M., Harush, D., Ben-Ari, J.,Chefetz, B. 2011. Uptake of carbamazepine by cucumber

544

plants-A case study related to irrigation with reclaimed wastewater. Chemosphere 82(6), 905–910.

545

Shon, H., Vigneswaran, S., Snyder, S., 2006. Effluent Organic Matter (EfOM) in Wastewater:

546

Constituents, Effects, and Treatment. Critical Reviews in Environmental Science and Technology

547

36(4), 327–374.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

22

548

Sugihara, M., Moeller, D., Paul, T., Strathmann, T., 2013. TiO2-photocatalyzed transformation of

549

the recalcitrant X-ray contrast agent diatrizoate. Applied Catalysis B: Environmental 129, 114–122.

550

Ternes, A., Hirsch, R., 2000. Occurrence and behavior of X-ray contrast media in sewage facilities

551

and the aquatic environment. Environmental Science and Technology 34(13), 2741–2748.

552

Ternes, T.A., Joss A., 2006. Human pharmaceuticals, hormones and fragrances: the challenge of

553

micropollutants in urban water management, IWA Publishing, London.

554

Ternes, T., Stüber, J., Herrmann, N., McDowell, D., Ried, A., Kampmann, M., Teiser, B., 2003.

555

Ozonation: a tool for removal of pharmaceuticals, contrast media and musk fragrances from

556

wastewater? . Water Research 37(8), 1976–1982.

557

Thio, B., Zhou, D., Keller, A., 2011. Influence of natural organic matter on the aggregation and

558

deposition of titanium dioxide nanoparticles. Journal of Hazardous Materials 189(1-2), 556–563.

559

Vanderford, B., Rosario-Ortiz, F., Snyder, S., 2007. Analysis of p-chlorobenzoic acid in water by

560

liquid chromatography-tandem mass spectrometry. Journal of Chromatography A 1164(1-2), 219–

561

223.

562

Wang, K., Hsieh, Y., Wu, C., Chang, C., 2000. The pH and anion effects on the heterogeneous

563

photocatalytic degradation of o-methylbenzoic acid in TiO2 aqueous suspension. Chemosphere

564

40(4), 389–394.

565

Westerhoff, P., Aiken, G., Amy, G., Debroux, J., 1999. Relationships between the structure of

566

natural organic matter and its reactivity towards molecular ozone and hydroxyl radicals. Water

567

Research 33(10), 2265-2276.

568

Westerhoff, P., Moon, H., Minakata, D., Crittenden, J., 2009. Oxidation of organics in retentates

569

from reverse osmosis wastewater reuse facilities. Water Research 43(16), 3992–3998.

570

Wu, C., Linden, K., 2010. Phototransformation of selected organophosphorus pesticides: roles of

571

hydroxyl and carbonate radicals. Water Research 44(12), 3585–3594.

572

Yang, J., Lee, S., 2006. Removal of Cr(VI) and humic acid by using TiO2 photocatalysis.

573

Chemosphere 63(10), 1677-1684.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

23

574

Zhang, Y., Chen, Y., Westerhoff, P., Crittenden, J., 2009. Impact of natural organic matter and

575

divalent cations on the stability of aqueous nanoparticles. Water Research 43(17), 4249–4257.

576

Zhou, T., Lim, T., Chin, S., Fane, A., 2011. Treatment of organics in reverse osmosis concentrate

577

from a municipal wastewater reclamation plant: Feasibility test of advanced oxidation processes

578

with/without pretreatment. Chemical Engineering Journal 166(3), 932–939.

579

Zwiener, C., Glauner, T., Sturm, J., Wörner, M., Frimmel, F., 2009. Electrochemical reduction of

580

the iodinated contrast medium iomeprol: Iodine mass balance and identification of transformation

581

products. Analytical and Bioanalytical Chemistry 395(6), 1885–1892.

582

National Institute of Standards and Technology (NIST):

583

http://webbook.nist.gov/cgi/cbook.cgi?ID=B6000512&Mask=80

584

http://webbook.nist.gov/cgi/cbook.cgi?ID=B6004671&Mask=80

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

585

24

586

Figure legends

587

Figure 1. Chemical structures of diatrizoate and iopromide.

588

Figure 2. Schematic process diagram of the secondary effluents-desalination process applied in this

589

study.

590

Figure 3. Influence of alkalinity and pH of RO brines on DTZ transformation. Inset shows influece

591

of brines dilution on transformation. The undiluted brines (control) corresponds to the fresh brines

592

in the main graph.

593

Figure 4. FTIR spectra of fresh (left panel) and synthetic RO brines (right panel).

594

Figure 5. Effect of the water matrix in p-chlorobenzoic acid degradation. [pCBA]o ≈ 5 µM.

595

Figure 6. Influence of the water matrix components on DTZ transformation. Left: Solutions

596

containing organic matter, alkalinity and composite synthetic brines. Na+ was the main counterion.

597

In synthetic brines 112±15 mg/L Ca+2 were also added. Right: Solutions containing mono and

598

multivalent anions or their mixture (NO3-, SO4-2, PO4-3, Cl- and HCO3-) or humic acid. Na+ was the

599

main counterion. Where specified Ca+2 at 112±15 mg/L was added.

600

Figure 7. LC-MS chromatograms denoting the evolution of organic iodine during UVA-TiO2 in

601

UPW. Top: IOPr, Bottom: DTZ. Insets show transformation and deiodination time profiles.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

25

ACCEPTED MANUSCRIPT

Table 1. Pseudo-first order reaction rate constants (k’, in min-1) for diatrizoate oxidation in UPW. TiO2

Alkalinity

k'×10-2

R2

mg/L TiO2

k'×10-2

R2

mg/L as CaCO3

3.5

11.50±0.40

0.98

0.25

4.77±0.52

0.86

control UPW

7

5.70±0.11

0.99

0.5

6.35±0.10

0.99

18

10

2.36±0.04

0.99

1

9.37±0.30

0.99

84

2

11.70±0.60

0.96

Chloride

k'×10-2

R2

mg/L Cl-

k'×10-2

R2

5.70±0.11

0.99

control UPW

5.69±0.11

0.99

2.20±0.09

0.98

185

1.98±0.01

0.99

1.33±0.03

0.99

390

1.85±0.01

0.99

159

1.10±0.03

0.99

800

1.87±0.02

0.99

413

0.94±0.01

0.99

M AN U

SC

units

RI PT

pH

TE D

Values represent average±standard deviation (R2 coefficient of determination). In most cases at least 3 replicates were performed.

AC C

EP

Conditions: [TiO2] = 1g/L; pH= 7 for chloride and alkalinity, 5.5 in TiO2 dose; UV fluence = 3564 mJ/cm2; irradiation time = 3 hours.

ACCEPTED MANUSCRIPT Table 2. Characteristics of RO brines. Parameter

Units

Value

pH

-

7.4±0.5

UV-254

-

0.6±0.03 20.9±3.5

RI PT

TOC Alkalinity as

448.1±157.9 CaCO3

132.1±8.3

K

P S Cl-

mg/L

TE D

NO3-

63.7±6.1

NH4+ -N

353.4±9.9

M AN U

Na

SC

Ca

7.9±3.1

85.0±41.1

513.2±26.1 32.9±1.1 2.8±0.1

AC C

EP

Values represent average±standard deviation of at least 3 replicate samples.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT Highlights •

Contribution of main OH radical scavengers in RO brines were studied in UVA-TiO2

•

Quantitative quenching of individual components was studied with synthetic

•

RI PT

brines

Dissolved organic matter performs the higher quenching (≈ 70%) followed by alkalinity (≈30%)

NOM-like materials displayed higher quenching than SMP in spite of its lower

SC

•

concentration.

M AN U

Reduction of UVA-TiO2 effectiveness by Ca+2 is lowered in presence of NOM

AC C

EP

TE D

•