Ultraviolet Irradiation of Permanganate Enhanced the Oxidation of

Aug 24, 2018 - The Hong Kong University of Science and Technology, Clear Water Bay, ... The Supporting Information is available free of charge on the ...
0 downloads 0 Views 540KB Size
Subscriber access provided by UNIV OF DURHAM

Environmental Processes

UV Irradiation of Permanganate Enhanced the Oxidation of Micropollutants by Producing HO• and Reactive Manganese Species Kaiheng Guo, Jinsong Zhang, Ailin Li, Ruijie Xie, Zhuojian Liang, Anna Wang, Li Ling, Xuchun Li, Chuanhao Li, and Jingyun Fang Environ. Sci. Technol. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.estlett.8b00402 • Publication Date (Web): 24 Aug 2018 Downloaded from http://pubs.acs.org on August 26, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 22

Environmental Science & Technology Letters

1

UV Irradiation of Permanganate Enhanced the Oxidation of Micropollutants by Producing

2

HO• and Reactive Manganese Species

3

Kaiheng Guo†, Jinsong Zhang‡, Ailin Li†, Ruijie Xie†, Zhuojian Liang†, Anna Wang†, Li Ling§,

4

Xuchun Liǁ, Chuanhao Li†, Jingyun Fang*,†

5



6

Technology, School of Environmental Science and Engineering, Sun Yat-Sen University,

7

Guangzhou 510275, P. R. China

8



Shen Zhen Water Affairs (Group) Co.Ltd., Shenzhen 518031, P. R. China

9

§

The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999066, Hong

Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation

10

Kong

11

ǁ

12

310018, P. R. China

13

*Corresponding author: J. Fang, Phone: + 86-18680581522; e-mail: [email protected].

School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou

14

1

ACS Paragon Plus Environment

Environmental Science & Technology Letters

15

Abstract

16

Permanganate was activated by UV photolysis at 254 nm, resulting in the efficient degradation of

17

micropollutants. The degradation of four probe molecules (i.e., nitrobenzene, benzoic acid,

18

terephthalic acid and parachlorobenzoic-acid) and two micropollutants (i.e., gemfibrozil and

19

nalidixic acid) resistant to permanganate oxidation, was enhanced by the UV/permanganate system,

20

with pseudo first-order rate constants (k′) of 0.065-0.678 min-1 under the experimental conditions.

21

Hydroxyl radicals (HO•) and Mn(V) peroxide were responsible for the enhancement, which were

22

produced during the activation of permanganate by UV irradiation. The quantum yield of HO• was

23

0.025 (± 0.001) mol Es-1 in the system. HO• oxidation primarily accounted for the degradation of

24

nitrobenzene and gemfibrozil, while both HO• and Mn(V) were responsible for the degradation of

25

benzoic acid, terephthalic acid, para-chlorobenzoic acid and nalidixic acid. This study is the first

26

report on the activation of permanganate by UV irradiation for the abatement of micropollutants in

27

water treatment, which may lead to a new advanced oxidation process relying on both HO• and

28

reactive manganese species.

29

2

ACS Paragon Plus Environment

Page 2 of 22

Page 3 of 22

30

Environmental Science & Technology Letters

INTRODUCTION

31

Permanganate is widely used in water treatment to control organic pollutants.1 Compared with

32

other oxidants, the advantages of permanganate are its effectiveness over a wide pH range, easy and

33

safe storage and delivery, chemical stability, low cost, and the lack of toxic byproducts.1 However,

34

permanganate is a selective oxidant and has been reported to only react with pollutants containing

35

electron rich organic moieties (ERM) such as phenols and olefins,2-4 whereas it is less effective to

36

some micropollutants such as ciprofloxacin, lincomycin, and trimethoprim.5

37

To enhance the degradation of pollutants, some methods have been used to activate

38

permanganate to produce reactive manganese intermediates such as trivalent manganese (Mn(III)),

39

hypomanganate (Mn(V)) and manganate (Mn(VI)).6, 7 For instance, permanganate can be activated

40

by bisulfite to produce Mn(III), which rapidly reacts with aniline and bisphenol A with second rate

41

constants of 105−106 M-1 s-1.8, 9 Permanganate can also be activated to produce Mn(III) by some

42

ligands, such as pyrophosphate (PP), ethylenediaminetetraacetic acid (EDTA), and nitrilotriacetic

43

acid (NTA).2, 10 Mn(V) could be generated through the reduction of permanganate by As(III) under

44

acidic conditions,11 while Mn(VI) could be generated through the reduction of permanganate by

45

sulfite or temperature heating under alkaline conditions.6,

46

important intermediates via the transformation of permanganate by some polysaccharides under

47

alkaline conditions.14,

48

benzylamine and primary/secondary alcohols.11, 16 Mn(VI) rapidly reacts with the phenolate ion via

49

electron transfer,17 and primary/secondary alcohols with second rate constants of ~105 M-1 s-1.18 Thus,

50

activation of permanganate is a promising way to enhance the utilization of permanganate and

15

12, 13

Both Mn(V) and Mn(VI) are

Mn(V) is very reactive toward sulfides, benzaldehydes, formic acid,

3

ACS Paragon Plus Environment

Environmental Science & Technology Letters

Page 4 of 22

51

promote the removal of micropollutants. However, the current activation methods, such as bisulfite,

52

ligands and As(III), involve the addition of inorganic or organic reagents, which are toxic or lead to

53

an increase in organic carbon and thus are not applicable to water treatment.

54

UV is commonly used for disinfection and oxidation in water treatment.19 Additionally, UV has

55

been used to activate oxidants such as H2O2,20, 21 chlorine22-24 and persulfate25, 26 to produce highly

56

reactive radicals such as HO•, Cl• and SO4•- for the abatement of micropollutants.27,

57

hypothesize that UV is a possible method to activate permanganate and produce highly reactive

58

species. MnIIIO2- and MnIVO2 have been suggested as the ultimate products of permanganate

59

photodecomposition,29 while the formation of MnVO4- and MnVIO42- intermediates in the system has

60

also been proposed.29-32 The production of the intermediates from the photolysis of permanganate

61

indicates that the UV/permanganate system might be a promising technology for water treatment.

62

However, the efficiency and the underlying mechanisms of the UV/permanganate process for

63

micropollutant degradation are totally unknown.

28

We

64

Thus, the objective of this study was to investigate the feasibility of the UV/permanganate

65

process for the abatement of micropollutants in water treatment. Reaction kinetics and participating

66

reactive

67

para-chlorobenzoic acid were selected as probe molecules, while gemfibrozil and nalidixic acid were

68

selected as actual micropollutants.

69

MATERIALS AND METHODS

70

Materials. All solutions were prepared with reagent-grade chemicals and ultrapure water (18.2 MΩ

71

cm). Sources of reagents and the preparation of stock solutions are provided in the Supporting

species

were

investigated.

Nitrobenzene,

benzoic acid,

4

ACS Paragon Plus Environment

terephthalic

acid and

Page 5 of 22

Environmental Science & Technology Letters

72

Information (SI) Text S1.

73

Experimental Procedures. The photochemical experiments were performed in a 700-mL,

74

magnetically stirred cylindrical borosilicate glass reactor with a quartz tube in the center, into which

75

a low-pressure mercury lamp (Heraeus GPH 212T5L/4, 10 W) was placed, as described previously.24

76

The average UV fluence rate was determined to be 2.13 mW cm-2 by iodide/iodate chemical

77

actinometry (Text S2).33 The temperature was maintained at 25 (± 0.2) °C.

78

A 700-mL testing solution containing 5 µM of the target compound, buffered at pH 7.4 using 2.5

79

mM borate buffer, was dosed with the permanganate stock solution to achieve a concentration of 100

80

µM and was simultaneously exposed to UV irradiation. Samples were collected at different time

81

intervals and the residual oxidants were quenched with ascorbic acid at a molar ratio of ascorbic acid

82

to permanganate of 5:1. Control tests, which involved exposure to either UV photolysis or

83

permanganate oxidation alone, were carried out in a similar manner. Another test was conducted in a

84

similar manner to determine the formation of HO• by spiking t-butanol into the UV/permanganate

85

system and monitoring the formation of formaldehyde.34, 35 One data set (shown with error bars in

86

each figure) was duplicated for quality control. The error bars in all the data plots represent the

87

maximum and minimum of the experimental data of the duplicated test results.

88

Analytical Methods. The concentrations of nitrobenzene, benzoic acid, terephthalic acid,

89

para-chlorobenzoic acid, gemfibrozil and nalidixic acid were determined using a high-performance

90

liquid chromatography (HPLC, Agilent 1260) equipped with an Agilent C18 column (Poroshell, 4.6

91

× 50 mm, 2.7 µm) and a diode array detector. Formaldehyde was determined by HPLC after

92

derivatization with 2,4-dinitrophenylhydrazine.36 A UV−visible spectrophotometer (Shimadzu,

5

ACS Paragon Plus Environment

Environmental Science & Technology Letters

93

UV-2600) was used to monitor the absorbance at 200−800 nm in the solution in the absence of

94

organics. Electron paramagnetic resonance (EPR) spectroscopy (Bruker EMX-E spectrometer,

95

Germany) was applied for in situ investigation of radical generation, using 5,5-dimethyl-1-pyrroline

96

N-oxide (DMPO) as the spin trapping reagent. The particle size distribution of MnO2 was

97

determined by a laser particle size analyzer (Malvern, Mastersizer 3000).

98

RESULTS AND DISCUSSION

99

Degradation of Micropollutants in the UV/Permanganate Process.

100

The degradation of four probe molecules (i.e., nitrobenzene, benzoic acid, terephthalic acid

101

and para-chlorobenzoic acid) and two micropollutants (i.e., gemfibrozil and nalidixic acid) was

102

enhanced by the UV/permanganate system, with pseudo first-order rate constants (k′) of 0.065, 0.182,

103

0.293, 0.318, 0.110 and 0.678 min-1 respectively, at a permanganate dosage of 100 µM and pH 7.4

104

(Figure 1). Permanganate was insignificant for their degradation. UV photolysis at 254 nm was the

105

most efficient for the degradation of para-chlorobenzoic acid with k′ of 0.056 min-1 and the quantum

106

yield of 0.106 mol Es-1 (Table S1). The efficient degradation of selected micropollutants by

107

UV/permanganate indicated that some reactive species may be produced during the co-exposure of

108

UV and permanganate.

109

The addition of t-butanol inhibited the degradation of nitrobenzene and gemfibrozil more

110

significantly than benzoic acid, terephthalic acid, para-chlorobenzoic acid and nalidixic acid. The k′

111

by reactive species of nitrobenzene and gemfibrozil decreased by 100% and 93.5% in the presence of

112

2 mM t-butanol, while those of benzoic acid, terephthalic acid, para-chlorobenzoic acid and nalidixic

113

acid were suppressed by 71.0%, 48.2%, 52.7% and 0.8% respectively (Figure 2). The nearly

6

ACS Paragon Plus Environment

Page 6 of 22

Page 7 of 22

Environmental Science & Technology Letters

114

complete inhibition of nitrobenzene and gemfibrozil degradation by t-butanol might be attributed to

115

the scavenging effect on HO•. As for the other compounds, their degradation should be attributable to

116

other reactive species in the presence of t-butanol, which might be reactive manganese species

117

(RMnS). When the concentration of t-butanol increased from 2 mM to 10 mM, k′s of the four probe

118

molecules were not further inhibited, indicating that RMnS may not be scavenged by t-butanol.

119

Role of HO• in the UV/Permanganate Process.

120

To investigate the existence of HO•, EPR was used. A typical 1:2:2:1 quartet signal of

121

DMPO-OH spin adduct with spin Hamiltonian parameters (aN = 14.9 G, aH = 14.9 G, g = 2.006)37

122

was generated in UV/permanganate, consistent with that in UV/H2O2 (Figure 3a). As for UV alone or

123

permanganate alone, no signal was observed. Note that the other three-line signal of oxidized DMPO

124

radical was also observed.38, 39

125

To investigate the quantum yield of HO• in the UV/permanganate system, t-butanol was added

126

to scavenge HO• and further form formaldehyde, whose formation could indicate the yield of HO•.34,

127

35

128

generated in the UV/permanganate system increased linearly with increasing reaction time, and

129

increasing the t-butanol concentration from 1 mM to 10 mM didn’t enhance the generation of

130

formaldehyde (Figure S1a). Thus, the quantum yield of HO• was determined to be 0.0253 (± 0.001)

131

mol Es-1 at pH 7.4 (Shown in Text S3 and Figure S1b). The quantum yield of HO• in

132

UV/permanganate was much lower than those of UV/H2O2, UV/chlorine and UV/NH2Cl processes

133

(Table S2). However, the higher molar absorption coefficient (ε254 nm) of permanganate (637 M-1 cm-1,

134

determined in this study) than other oxidants made the generation of HO• and the degradation

The HO• yield is about four-fold of the formaldehyde yield.34 The concentration of formaldehyde

7

ACS Paragon Plus Environment

Environmental Science & Technology Letters

135

efficiency of the four probe micropollutants in UV/permanganate comparable with those in other UV

136

based advanced oxidation processes (AOPs) (Table S2 and Figure S2).

137

Varying conditions could alter the quantum yield of HO•. Increasing pH from 4.0 to 9.5 reduced

138

the quantum yield by 50.4% (Figure 3b and Figure S3a). The decreasing quantum yield with

139

increasing pH indicated that H+ may be involved in the generation of HO•. Note that the ε254 nm of

140

permanganate was stable with increasing pH (Figure S3b). Also, the quantum yield decreased by

141

42.8% with increasing permanganate dosage from 20 µM to 100 µM (Figure 3b and Figure S4), due

142

to the greater filter effect of UV light at higher permanganate dosage.

143

Role of Reactive Manganese Species (RMnS) in the UV/Permanganate System.

144

Theoretically, permanganate can be reduced to Mn(VI), Mn(V), Mn(IV), Mn(III) and Mn(II).

145

Mn(VI) was tested to be not reactive with nitrobenzene and benzoic acid (Figure S5), and it could

146

only exist in alkaline condition.6 Also, Mn(II) and Mn(IV) usually act as stable manganese reduction

147

products, and they are not reactive with most micropollutants.2, 9 Therefore, the RMnS may contain

148

Mn(V) and Mn(III), which are very reactive and unstable. Figure S6a shows the time-resolved

149

absorbance spectra of the UV/permanganate system. The absorbance at 525 nm (Mn(VII)) decreased

150

from 0.247 cm-1 to 0.209 cm-1 with increasing time from 0 to 30 min, while that at 375 nm increased

151

from 0.062 cm-1 to 0.517 cm-1, due to the accumulation of in situ formed MnO2.40 In the presence of

152

50 mM PP, the absorbance at 300−500 nm was inhibited significantly (Figure S6b), probably due to

153

the complexation of MnO2 with PP (Figure S7). Figure S8 confirms that the MnO2 particles were

154

produced in UV/permanganate, but it disappeared when adding 50 mM PP.

155

Mn(III) was recently reported to be an important oxidant in permanganate/bisulfite and

8

ACS Paragon Plus Environment

Page 8 of 22

Page 9 of 22

Environmental Science & Technology Letters

156

permanganate/Mn(II)/PP systems.9,

157

UV/permanganate, additional tests were conducted. (1) The characteristic peak of Mn(III) was

158

compared with permanganate/Mn(II)/PP system. By comparing Figures S6 and S9, the featured peak

159

of Mn(III) at 260 nm10 was not recorded in UV/permanganate system. Also note that Mn(III) was not

160

produced by permanganate alone in the presence of 50 mM PP (Figure S10). (2) The effect of PP on

161

the degradation of nitrobenzene and benzoic acid by UV/permanganate was investigated (Figure

162

S11). Their degradation was not suppressed by PP, which can react with Mn(III) to form Mn(III)-PP

163

complex. This result indicated that Mn(III) was not the dominant species for the degradation of

164

nitrobenzene and benzoic acid, as Mn(III)-PP was not reactive toward them (Figure S12). If Mn(III)

165

was important for the degradation of nitrobenzene and benzoic acid, the addition of PP would

166

compete with the target compounds to form Mn(III)-PP and to inhibit their degradation. Above all,

167

Mn(III) was ruled out.

168

10

To

ascertain

whether

Mn(III)

was

important

in

As reported, an excited-state [MnO2(η2-O2)-]* can be formed during the UV photolysis at 254

169

nm of permanganate.30,

170

oxidation agent than permanganate, may be formed via O-O formation from two Mn=O bonds of

171

permanganate.29,

172

micropollutants in UV/permanganate. As for the reactivity of Mn(V), it can oxidize α-C of primary

173

and secondary alcohols to aldehydes through hydrogen transfer.11 As such, it is rational to expect that

174

t-butanol cannot be oxidized by Mn(V) due to the lack of hydrogen at the α-C. So, the obvious

175

degradation of benzoic acid, terephthalic acid, para-chlorobenzoic acid and nalidixic acid by

176

UV/permanganate with the presence of t-butanol (Figure 2) was very likely attributable to Mn(V),

30, 42

40, 41

Then Mn(V) peroxide (MnO2(η2-O2)-), which is a more reactive

Thus, Mn(V) was proposed as the main RMnS for the degradation of

9

ACS Paragon Plus Environment

Environmental Science & Technology Letters

177

while the negligible degradation of nitrobenzene and gemfibrozil indicated their resistance to Mn(V).

178

This result also indicates that Mn(V) is a selective oxidant, which reactivity is compound specific.

179

In summary, the mechanism for the UV photolysis of permanganate is proposed in Scheme 1.

180

The UV photolysis of permanganate forms Mn(V) peroxide. The UV photolysis of O-O in Mn(V)

181

peroxide is likely to form HO•, similar like that of the UV photolysis of H2O2. Meanwhile, the

182

disproportionation 13 or UV photolysis of Mn(V) peroxide forms MnO2 as the final product.30, 40

183 184

Scheme 1. Proposed mechanism for the UV photolysis of permanganate

185 186

Engineering Implications.

187

UV and permanganate have been widely used for water treatment. This study is the first to show

188

the synergistic effect of co-exposure to UV photolysis and permanganate for micropollutant

189

degradation. The UV/permanganate system can produce reactive species of HO• and Mn(V) peroxide.

190

The former is a broad-spectrum oxidant, while the latter is selective. The multiple reactive species in

191

the system can complement each other in degrading a variety of contaminants. HO• is firstly

192

identified and proved in the UV/permanganate system. Mn(V) is a new reactive species in water

193

treatment, whose mechanism on micropollutant degradation is on-going in our group. The higher

194

removal efficiencies of benzoic acid, terephthalic acid and para-chlorobenzoic acid by

195

UV/permanganate compared with UV/H2O2 were responsible for both Mn(V) and HO• in 10

ACS Paragon Plus Environment

Page 10 of 22

Page 11 of 22

196

Environmental Science & Technology Letters

UV/permanganate (Figure S2).

197

Further research is needed to incorporate the effects of operational conditions (such as

198

permanganate dosage) and water matrix components (such as pH, dissolved organic matter and

199

alkalinity), to evaluate the application potential of the UV/permanganate process in real water

200

treatment. Initial experiments with treatment of nitrobenzene and benzoic acid indicated that: (1) the

201

degradation of nitrobenzene and benzoic acid was favored at acidic condition (Figure 4a) and higher

202

dosages of permanganate (Figure 4b); (2) nitrobenzene and benzoic acid could be efficiently

203

degraded with the presence of 1 mg L-1 natural organic matter (NOM), which are ubiquitous in

204

natural water and drinking water (Figure 4c). Thus, the UV/permanganate system can be a promising

205

AOP for the abatement of micropollutants in water treatment.

206 207

ASSOCIATED CONTENT

208

Supporting Information

209

The Supporting Information is available free of charge on the ACS Publications website at

210

http://pubs.acs.org.

211

Sources of reagents and the preparation of stock solutions (Text S1), determination of UV

212

photon flux and effective path length of UV light (Text S2), determination of the HO• quantum yields

213

of in the UV/permanganate system (Text S3), properties of selected micropollutants (Table S1), the

214

quantum yields of HO•, the molar absorption coefficients of oxidants at 254 nm and the formation

215

rates of HO• in different AOPs (Table S2), the formation of formaldehyde by the UV/permanganate

216

system in the presence of t-butanol (Figure S1), comparison of the degradation kinetics of

11

ACS Paragon Plus Environment

Environmental Science & Technology Letters

217

nitrobenzene, benzoic acid, terephthalic acid and para-chlorobenzoic acid by the UV/H2O2 and

218

UV/permanganate systems (Figure S2), effect of pH on the formation of formaldehyde (Figure S3),

219

effect of permanganate dosage on the formation of formaldehyde (Figure S4), degradation of

220

nitrobenzene and benzoic acid by pre-synthesized MnVIO42- in pure water (Figure S5), UV−vis

221

spectra at the wavelengths of 200−800 nm in the UV/permanganate system in the absence/presence

222

of PP (Figure S6), effect of PP on UV−vis spectra of pre-synthesized MnO2 (Figure S7), particle size

223

distribution of the solution during UV/permanganate treatment in the absence and presence of PP

224

(Figure S8), UV−vis spectra at the wavelengths of 200−800 nm (Figure S9), UV−vis spectra at the

225

wavelengths of 200−800 nm in the permanganate/PP system (Figure S10), effects of PP on

226

degradation of nitrobenzene and benzoic acid by UV/permanganate (Figure S11), degradation of

227

nitrobenzene and benzoic acid by Mn(III)-PP (Figure S12).

228

AUTHOR INFORMATION

229

*Corresponding author: J. Fang, Phone: + 86-18680581522; e-mail: [email protected].

230

ACKNOWLEDGMENTS

231

This work was financially supported by the Major Science and Technology Program for Water

232

Pollution Control and Treatment in China (No. 2015ZX07406004).

233 234 235

REFERENCES

236

(1) Guan, X. H.; He, D.; Ma, J.; Chen, G. H. Application of permanganate in the oxidation of

237

micropollutants: A mini review. Front. Environ. Sci. Eng. China. 2010, 4, 405-413.

238

(2) Jiang, J.; Pang, S.; Ma, J.; Liu, H. Oxidation of phenolic endocrine disrupting chemicals by

12

ACS Paragon Plus Environment

Page 12 of 22

Page 13 of 22

Environmental Science & Technology Letters

239

potassium permanganate in synthetic and real waters. Environ. Sci. Technol. 2012, 46, 1774-1781.

240

(3) Jiang, J.; Pang, S.; Ma, J. Oxidation of triclosan by permanganate (Mn(VII)): Importance of

241

ligands and in situ formed manganese oxides. Environ. Sci. Technol. 2009, 43, 8326-8331.

242

(4) Hu, L.; Martin, H. M.; Arce-Bulted, O.; Sugihara, M. N.; Keating, K. A.; Strathmann, T. J.

243

Oxidation of carbamazepine by Mn(VII) and Fe(VI): Reaction kinetics and mechanism. Environ. Sci.

244

Technol. 2009, 43, 509-515.

245

(5) Hu, L.; Martin, H. M.; Strathmann, T. J. Oxidation kinetics of antibiotics during water treatment

246

with potassium permanganate. Environ. Sci. Technol. 2010, 44, 6416-6422.

247

(6) Simandi, L. I.; Jaky, M.; Schelly, Z. A. Short-lived manganate(VI) and manganate(V)

248

intermediates in the permanganate oxidation of sulfite ion. J. Am. Chem. Soc. 1984, 16, 6866-6867.

249

(7) Kostka, J. E.; Luther, G. W.; Nealson, K. H. Chemical and biological reduction of

250

Mn(III)-pyrophosphate complexes: Potential importance of dissolved Mn(III) as an environmental

251

oxidant. Geochim. Cosmochim. Acta 1995, 59, 885-894.

252

(8) Sun, B.; Dong, H. Y.; He, D.; Rao, D. D.; Guan, X. H. Modeling the kinetics of contaminants

253

oxidation and the generation of Manganese(III) in the Permanganate/Bisulfite process. Environ. Sci.

254

Technol. 2016, 50, 1473-1482.

255

(9) Sun, B.; Guan, X. H; Fang, J. Y; Tratnyek, P. G. Activation of manganese oxidants with bisulfite

256

for enhanced oxidation of organic contaminants: The involvement of Mn(III). Environ. Sci. Technol.

257

2015, 49, 12414-12421.

258

(10) Jiang, J.; Pang, S. Y.; Ma, J. Role of ligands in permanganate oxidation of organics. Environ.

259

Sci. Technol. 2010, 44, 4270-4275.

13

ACS Paragon Plus Environment

Environmental Science & Technology Letters

260

(11) Simándi, L. I.; Záhonyi-Budó, É. Relative reactivities of hydroxy compounds with short-lived

261

manganese(V). Inorg. Chim. Acta 1998, 281, 235-238.

262

(12) Lee, D. G.; Chen, T. Reduction of manganate(VI) by mandelic acid and its significance for

263

development of a general mechanism of oxidation of organic compounds by high-valent transition

264

metal oxides. J. Am. Chem. Soc. 1993, 115, 11231-11236.

265

(13) Carrington, A.; Symons, M. C. R. 655. Structure and reactivity of the oxy-anions of transition

266

metals. Part I. The manganese oxy-anions. J. Chem. Soc. 1956, 186, 377-383.

267

(14) Jáky, M.; Szeverényi, Z.; Simándi, L. I. Formation of manganate(V) in oxidations by

268

permanganate ion in strongly alkaline solutions. Inorg. Chim. Acta 1991, 186, 33-37.

269

(15) Zaafarany, I. A.; AlArifi, A. A. S. N.; Fawzy, A.; Ahmed, G. A.; Ibrahim, S. A.; Hassan, R. M.;

270

Takagi, H. D. Further evidence for detection of short-lived transient hypomanganate(V) and

271

manganate(VI) intermediates during oxidation of some sulfated polysaccharides by alkaline

272

permanganate using conventional spectrophotometric techniques. Carbohyd Res. 2010, 345,

273

1588-1593.

274

(16) Dubey, R.; Kótai, L.; Banerji, K. K. Kinetics and mechanism of the oxidation of substituted

275

benzylamines by oxo(salen)manganese(V) complexes. J. Chem. Res. 2003, 2003, 56-57.

276

(17) Lee, D. G.; Sebastián, C. F. The oxidation of phenol and chlorophenols by manganate(VI) ion.

277

Can. J. Chem. 1981, 59, 2780-2786.

278

(18) Záhonyi-Budó, É.; Simándi, L. I. Oxidations with unstable manganese(VI) in acidic solution.

279

Inorg. Chim. Acta 1995, 237, 173-175.

280

(19) Pereira, V. J.; Linden, K. G.; Weinberg, H. S. Evaluation of UV irradiation for photolytic and

14

ACS Paragon Plus Environment

Page 14 of 22

Page 15 of 22

Environmental Science & Technology Letters

281

oxidative degradation of pharmaceutical compounds in water. Water Res. 2007, 41, 4413-4423.

282

(20) Wols, B. A.; Hofman-Caris, C. H. M.; Harmsen, D. J. H.; Beerendonk, E. F. Degradation of 40

283

selected pharmaceuticals by UV/H2O2. Water Res. 2013, 47, 5876-5888.

284

(21) Shu, Z.; Bolton, J. R.; Belosevic, M.; Gamal El Din, M. Photodegradation of emerging

285

micropollutants using the medium-pressure UV/H2O2 Advanced Oxidation Process. Water Res. 2013,

286

47, 2881-2889.

287

(22) Wu, Z.; Fang, J.; Xiang, Y.; Shang, C.; Li, X.; Meng, F.; Yang, X. Roles of reactive chlorine

288

species in trimethoprim degradation in the UV/chlorine process: Kinetics and transformation

289

pathways. Water Res. 2016, 104, 272-282.

290

(23) Jin, J.; El-Din, M. G.; Bolton, J. R. Assessment of the UV/Chlorine process as an advanced

291

oxidation process. Water Res. 2011, 45, 1890-1896.

292

(24) Guo, K. H.; Wu, Z. H; Shang, C.; Yao, B.; Hou, S. D.; Yang, X.; Song, W. H.; Fang, J. Y.

293

Radical chemistry and structural relationships of PPCP degradation by UV/Chlorine treatment in

294

simulated drinking water. Environ. Sci. Technol. 2017, 51, 10431-10439.

295

(25) Hou, S.; Ling, L.; Shang, C.; Guan, Y.; Fang, J. Degradation kinetics and pathways of

296

haloacetonitriles by the UV/Persulfate process. Chem. Eng. J. 2017, 320, 478-484.

297

(26) Lian, L. S.; Yao, B.; Hou, S. D; Fang, J. Y.; Yan, S. W.; Song, W. H. Kinetic study of hydroxyl

298

and sulfate radical-mediated oxidation of pharmaceuticals in wastewater effluents. Environ. Sci.

299

Technol. 2017, 51, 2954-2962.

300

(27) Lee, Y.; von Gunten, U. Oxidative transformation of micropollutants during municipal

301

wastewater treatment: Comparison of kinetic aspects of selective (chlorine, chlorine dioxide, ferrate

15

ACS Paragon Plus Environment

Environmental Science & Technology Letters

302

VI, and ozone) and non-selective oxidants (hydroxyl radical). Water Res. 2010, 44, 555-566.

303

(28) Wols, B. A.; Hofman-Caris, C. H. M. Review of photochemical reaction constants of organic

304

micropollutants required for UV advanced oxidation processes in water. Water Res. 2012, 46,

305

2815-2827.

306

(29) Lee, D. G.; Moylan, C. R.; Hayashi, T.; Brauman, J. I. Photochemistry of aqueous

307

permanganate ion. J. Am. Chem. Soc. 1987, 109, 3003-3010.

308

(30) Thornley, W. A.; Bitterwolf, T. E. Photochemistry of the permanganate ion in low-Temperature

309

frozen matrices. Inorg. Chem. 2015, 54, 3370-3375.

310

(31) Yu, J. T. Photochemical and thermochemical reactions of permanganate ions in ammonium

311

perchlorate and ammonium tetrafluoroborate crystals: An EPR study. J. Phys. Chem. 1992, 96,

312

5746-5748.

313

(32) Lin, Z.; Huang, T. T. S. Some interesting kinetic observations on the aqueous permanganate

314

solutions. Ind. Eng. Chem. Res. 1987, 26, 2148-2151.

315

(33) Bolton, J. R.; Linden, K. G. Standardization of methods for fluence (UV dose) determination in

316

bench-scale UV experiments. J. Environ. Eng. 2003, 129, 209-215.

317

(34) Flyunt, R.; Leitzke, A.; Mark, G.; Mvula, E.; Reisz, E.; Schick, R.; von Sonntag, C.

318

Determination of •OH, O2•- and hydroperoxide yields in ozone reactions in aqueous solution. J. Phys.

319

Chem. B 2003, 107, 7242-7253.

320

(35) Nöthe, T.; Fahlenkamp, H.; Sonntag, C. V. Ozonation of wastewater: Rate of ozone

321

consumption and hydroxyl radical yield. Environ. Sci. Technol. 2009, 43, 5990-5995.

322

(36) USEPA EPA method 8315A (SW-846): Determination of carbonyl compounds by high

16

ACS Paragon Plus Environment

Page 16 of 22

Page 17 of 22

Environmental Science & Technology Letters

323

performance liquid chromatography (HPLC). United States Environmental Protection Agency.

324

1996,.

325

(37) Hojo, Y.; Okado, A.; Kawazoe, S.; Mizutani, T. Direct evidence for in vivo hydroxyl radical

326

generation in blood of mice after acute chromium(VI) intake. Biol. Trace Elem. Res. 2000, 76, 75-84.

327

(38) Feng, G. D; Cheng, P.; Yan, W. F; Boronat, M.; Li, X.; Su, J. H.; Wang, J.; Li, Y.; Corma, A.;

328

Xu, R.; Yu, J. Accelerated crystallization of zeolites via hydroxyl free radicals. Science. 2016, 351,

329

1188-1191.

330

(39) Xing, M. Y.; Xu, W. J.; Dong, C. C.; Bai, Y. C.; Zeng, J. B.; Zhou, Y.; Zhang, J. L.; Yin, Y. D.

331

Metal Sulfides as Excellent Co-catalysts for H2O2 Decomposition in Advanced Oxidation Processes.

332

Chem 2018, 4, 1359-1372.

333

(40) Hu, X. N.; Shi, L. Y.; Zhang, D. S.; Zhao, X.; Huang, L. Accelerating the decomposition of

334

KMnO4 by photolysis and auto-catalysis: A green approach to synthesize a layered birnessite-type

335

MnO2 assembled hierarchical nanostructure. RSC Adv. 2016, 6, 14192-14198.

336

(41) Zimmerman, G. Photochemical decomposition of aqueous permanganate ion. J. Chem. Phys.

337

1955, 23, 825-832.

338

(42) Crandell, D. W.; Xu, S.; Smith, J. M.; Baik, M. Intramolecular oxyl radical coupling promotes

339

O–O bond formation in a homogeneous mononuclear mn-based water oxidation catalyst: A

340

computational mechanistic investigation. Inorg. Chem. 2017, 56, 4435-4445.

341

17

ACS Paragon Plus Environment

Environmental Science & Technology Letters

342

TOC Art

343

18

ACS Paragon Plus Environment

Page 18 of 22

Page 19 of 22

Environmental Science & Technology Letters

(b) Benzoic acid

(a) Nitrobenzene

1.0

1.0 y = e -0.005x R2 = 0.9962

0.8 UV photolysis Permanganate UV/permanganate

0.6

C/C0

C/C0

0.8

y = e -0.006x R2 = 0.9968

0.6 0.4

0.4 y = e -0.065x R2 = 0.9813

0.2

y = e -0.182x R2 = 0.9943

0.2 0.0

0.0 0

5

10

15

20

25

0

30

5

10

15

25

30

(d) Para-chlorobenzoic acid

(c) Terephthalic acid

1.0

1.0 0.8 0.6

UV photolysis Permanganate UV/permanganate

0.4 y = e -0.293x R2 = 0.9996

0.2

UV photolysis Permanganate UV/permanganate

0.8

y = e -0.011x R2 = 0.9996

C/C0

C/C0

20

Time (min)

Time (min)

0.6 0.4

y = e -0.056x R2 = 0.9955

0.2

y = e -0.318x R2 = 0.9985

0.0

0.0 0

5

10

15

20

25

0

30

5

10

15

20

25

30

Time (min)

Time (min)

(f) Nalidixic acid

(e) Gemfibrozil

1.0

1.0 y = e -0.048x R2 = 0.9977

0.8

UV photolysis Permanganate UV/permanganate

0.6 y = e -0.11x R2 = 0.9811

0.4

y = e -0.047x R2 = 0.9976

0.8 C/C0

C/C0

UV photolysis Permanganate UV/permanganate

0.6 UV photolysis Permanganate UV/permanganate

0.4 0.2

0.2

y = e -0.678x R2 = 0.9998

0.0

0.0 0

5

10

15

0

20

2

4

6

8

10

Time (min)

Time (min)

Figure 1. Comparison of the degradation kinetics of (a) nitrobenzene, (b) benzoic acid, (c) terephthalic acid, (d) para-chlorobenzoic acid, (e) gemfibrozil, and (f) nalidixic acid by UV, permanganate and UV/permanganate at pH 7.4. Conditions: [MnO4-]0 = 100 µM, [target compound]0 = 5 µM.

19

ACS Paragon Plus Environment

Environmental Science & Technology Letters

Page 20 of 22

0.8

0.6 k' (min-1)

Nalidixic acid

UV photolysis Permanganate Reactive species

Terephthalic Para-chlorobenzoic acid acid

0.4

Benzoic acid

0.2 Gemfibrozil Nitrobenzene

0.0 0 2 10

0 2 10

0 2 10

0 2 10

0 2

0 2

t-butanol concentration (mM)

Figure 2. Effects of t-butanol on the first order degradation rate constants (k′) of nitrobenzene, benzoic acid, terephthalic acid, para-chlorobenzoic acid, gemfibrozil, and nalidixic acid by the UV/permanganate system at pH 7.4. Conditions: [MnO4-]0 = 100 µM, [target compound]0 = 5 µM.

20

ACS Paragon Plus Environment

Page 21 of 22

Environmental Science & Technology Letters

(b) 20

40

HO· quantum yield (mol Es-1)

0.05

60

80

100

Permanganate dosage (µM)

0.04

0.03

0.02

0.01

0.00 4

5

6

7

8

9

10

pH

Figure 3. (a) Electron paramagnetic resonance (EPR) spectra for the UV/permanganate system after 2 min reaction at room temperature. Conditions: [MnO4-]0 = 0.5 mM, [DMPO]0 = 0.45 M. The EPR signals are marked as follows: red circles - hydroxyl radicals; green squares - oxidized DMPO radicals. (b) Effects of pH (blue symbol, [MnO4-]0 = 100 µM) and permanganate dosages (red symbol, pH 7.4) on HO• quantum yield by the UV/permanganate system at the initial concentration of t-butanol of 10 mM.

21

ACS Paragon Plus Environment

Environmental Science & Technology Letters

(a) Nitrobenzene

Page 22 of 22

(c)

(b) Benzoic acid

Nitrobenzene

Benzoic acid

Nitrobenzene Benzoic acid

0.3

k' (min-1)

UV photolysis Permanganate Reactive species

0.2

0.1

0.0 4.0 7.4 9.5

4.0 7.4 9.5

pH

50 100 200

50 100 200

Permanganate dosage (µM)

0

1

0

1 -1

NOM (mg L )

Figure 4. Effects of (a) pH, (b) permanganate dosages and (c) natural organic matter (NOM) on the degradation of nitrobenzene and benzoic acid by the UV/permanganate system. Conditions: [target compound]0 = 5 µM, (a) [MnO4-]0 = 100 µM; (b) pH = 7.4; (c) [MnO4-]0 = 100 µM, pH = 7.4.

22

ACS Paragon Plus Environment