Effects and Kinetics of Chlorine Dioxide for Removal of Benzo[a]pyrene in Water

Abstract

Benzo[a]pyrene (BaP) is one of the persistent organic pollutants (POPs) existing widely in the environment and presenting great threats to ecosystems. Chlorine dioxide (ClO₂) has been adopted as an effective alternative to chlorine for disinfection in potable water treatment. In this study, a series of experiments were conducted to investigate the feasibility of using ClO₂ as an oxidant for BaP degradation. We examined degradation kinetics and effects of ClO₂ dosage, reaction time, and pH on the BaP removal by ClO₂. Results demonstrated that ClO₂ could remove BaP effectively. ClO₂ dosage and reaction time were found to have a significant impact on BaP removal, whereas pH only affected slightly in the range of 3.2–9.7. Under optimal reaction conditions, the removal efficiency could reach an extremely high level of 99.8% within 30 min at a ClO₂ dosage of 5 mg/L, temperature of 20°C, and pH 7.2 for the BaP samples with initial concentration of 10 μg/L. The reaction between ClO₂ and BaP followed a second-order kinetic, and the corresponding rate constant was determined to be 7.795 L/(mol·s). The predominant end products of BaP degradation by ClO₂ were characterized as quinine derivatives. This study not only provides a feasible chemical method to efficiently degrade BaP in water treatment, but also suggests a new strategy to promote the development of technologies for POPs reduction in the environment.

Introduction

Benzo[a]pyrene (BaP) is a typical representative of polycylic aromatic hydrocarbons that exist widely in environment. BaP is known to have great carcinogenic potential and thus would trigger the development of diseases such as lung cancer, esophagus cancer, gastric cancer, and skin cancer (Knafla et al., 2006; Hakami et al., 2008; Kometani et al., 2009; Schmitz-Spanke et al., 2009). Additionally, BaP also presents teratogenic (Bang et al., 2009), mutagenic (Perera et al., 2005), and neurotoxic (Saunders et al., 2002; Tang et al., 2003) effects, which may cause serious damage to DNA and protein (Kim and Lee, 1997; Sigounas et al., 2010) and be highly toxic to immune system (Reynaud and Deschaux, 2006).

BaP has been arousing intensive concern for its inherent nature of wide distribution, high stability, and high toxicity. Trace BaP can be hardly removed by traditional water treatment facilities (Jiang et al., 2000). According to previous studies, the available methods for treating BaP include physical, chemical, and biological processes. For example, there have been a number of studies addressing biological removal of BaP by bacteria or fungi (Juhasz and Naidu, 2000; Su et al., 2007; Wang et al., 2008). Nevertheless, the formation of carcinogenic intermediate or end products remains a problem (Sutherland, 1992). Advanced oxidation processes (AOP) have been frequently reported to be able to mineralize majority of organic compounds unselectively. Depending on the AOP and oxidants used, the half-life of BaP in the reactions followed the elevated order of O₃=O₃/UV<O₃/H₂O₂<O₃/H₂O₂/UV (Trapido et al., 1995). Homem et al. (2009) have found that BaP could be well eliminated using Fenton reaction, and the efficiencies were positively correlated to temperatures and Fe²⁺ concentrations and adversely affected by excessive H₂O₂ dosage. Several investigations showed that improved removal efficiencies could be obtained through the combination of Fenton or Fenton-like system with microbes (Zanga et al., 2007; Rafin et al., 2009). However, it should be realized that there has been no previous report of chlorine dioxide (ClO₂) for BaP removal in potable water treatment.

The principal possibility of using ClO₂ to degrade BaP originates from the strong oxidizing capability of ClO₂, as a result of decomposing a variety of nondegradable organic containments (Ganiev et al., 2004; Luca et al., 2008; Navalon et al., 2008). Particularly, ClO₂-participating oxidation avoids the formation of toxic byproducts such as THMs. By virtue of these advantages, ClO₂ has been drawing an increasing interest as alternative to chlorine for water disinfection in recent years (Hrudey, 2009; Huang, 2010).

This study aims to examine the feasibility and effectiveness of chemical removal of BaP by using ClO₂ as oxidant. The effects of dosage, reaction time, and pH on the reaction between BaP and ClO₂ were investigated, followed by quantitative characterization of kinetic behavior and the end products of the reactions.

Materials and Methods

Chemicals

BaP (AR 99%) was purchased from Sigma-Aldrich Company. ClO₂ stock solution was prepared by the reaction of NaClO₂ and H₂SO₄ (Ji et al., 2008) and calibrated before use by sequential idiomatic method. The buffer solution used was composed of KH₂PO₄ and NaH₂PO₄. Methanol was in chromatographic grade and obtained from Tianjin Kermel Chemical Reagent Co., Ltd. If not stated specifically, other chemical agents were of analytical grade. All the aqueous samples were prepared using twice-distilled water.

Analytics and measurements

All the experiments were conducted at 20°C and dark environment. BaP was placed in a 250-mL conical flask to give 10 μg/L standard solution. Then the pH buffer solution and ClO₂ solution were added into BaP standard solution to start the reactions. After a certain reaction time, the reactions were terminated by adding excessive sodium thiosulfate. Thereafter, the reaction solution was transferred into separating funnels, and extracted triply with dichloromethane. The extract liquor was dehydrated and concentrated into 1 mL by purging the solvent with nitrogen, followed by analysis with high-performance liquid chromatography (HPLC) or gas chromatography–mass spectrometry (GC-MS). The experiments were carried out in triplicate.

The HPLC (Agilent Technologies) with a 1050 pump and a Rheodyne injector was used to quantify the BaP. The system was equipped with a G1321A fluorescence detector (λ_em=303 nm, λ_ex=425 nm) for the investigation of the efficacy and the effect of parameters, and it was equipped with a G1314A variable wave detector (wavelength at 295 nm) for studying the kinetics of the reaction. A Hypersil ODS C18 column (200 mm×4.6 mm) was used as a mobile phase of 85:15 (v/v) methanol/water mixtures with a flow rate of 0.5 mL/min. Column temperature was set at 30°C by an AT-130 Column Heater and a TC-100 Temperature Controller. The injection volume was 20 mL and the retention time was controlled as 35.92 min.

To identify the end products of BaP degradation, 1 mL extracted and dehydrated sample was injected into a gas chromatograph (6890N; Agilent Technologies) with a mass spectrometer (5973N; Agilent Technologies). A film HP-5MS (30 m×0.25 mm×0.25 mm) linked to a 5% phenyl methyl silicone column was used. The oven temperature program was set at 50°C for 2 min and ramped up to 260°C at a rate of 8°C/min and then held for 5 min. Mass spectra were recorded at 1 scan/s under electron impact at 70 eV with a mass range of 35–400 m/z. The carrier gas was helium.

Results and Discussion

The effect of ClO₂ on BaP removal

The performance of BaP degradation by ClO₂ depends preliminarily on the amount of ClO₂ used. First, the effect of ClO₂ dosage on BaP removal was investigated on the basis of 10 μg/L BaP samples at pH 7.2 and 20°C. The concentrations of ClO₂ applied to different samples were initiated over the range of 0–45 mg/L. The reactions were terminated at 120 min. As shown in Fig. 1, the removal efficiency of BaP increased from 59.43% to 87.22% as ClO₂ dosage was increased from 1 to 2 mg/L, reaching its maximum of 99.75% at ClO₂ dosage of 5 mg/L. This removal was in consistence with the finalized BaP concentration lower than 0.01 μg/L. It should be pointed out that 5 mg/L ClO₂ may be much higher for disinfection process in usually drinking water plants. The residual chlorite in the treated effluent would exceed water quality standards. Thus, it appears more suitable to use ClO₂ to control BaP in preoxidation process; otherwise, some measures should be taken into account to remove the superabundant chlorite.

FIG. 1.

BaP removal efficiency as function of ClO₂ dosage at pH 7.2, 20°C, and reaction time of 20 min. BaP, benzo[a]pyrene; ClO₂, chlorine dioxide.

Thereafter, the dependence of BaP removal on the magnitude of reaction time was further studied at initial BaP concentration of 10 μg/L and ClO₂ of 5 mg/L (pH 7.2 and 20°C). The reaction for each group was deactivated at a stepwise time of 5–240 min. It can be seen from Fig. 2 that BaP removal efficiency increased sharply to 90% at the first 10 min, followed by the plateaus of 99.7% at the end of 30 min. Judged from these results, the reaction of ClO₂ and BaP proceeds rapidly, such that the attainment of equilibrium can be achieved within a short period.

FIG. 2.

BaP removal as function of reaction time at pH 7.2, 20°C, and ClO₂ dosage of 5 mg/L.

The effect of pH on the BaP removal was examined at 20°C. The pH values in aqueous reaction system having 10 μg/L BaP and 5 mg/L ClO₂ were set as 3.2, 5.7, 7.2, 8.3, and 9.7, respectively. The reactions were then terminated at 30 min after being subject to chemical analyses. The results are given in Fig. 3, which shows that BaP removal efficiency was slightly higher (2%) at neutral pH (7.2) than that at acidic pH (3.2 and 5.7). Such inconspicuous improvement may result from the alteration of oxidability of ClO₂ with respect to the transformation of ClO₂ in water at different pH conditions (Huang, 2010). In the usual disinfection of water treatment facilities, ClO₂ undergoes single electron transformation from ClO₂ to ClO₂⁻: \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland, xspace} \usepackage{amsmath, amsxtra} \pagestyle{empty} \DeclareMathSizes {10} {9} {7} {6} \begin{document} \begin{align*}{ \rm ClO}_2 + e^ - = { \rm ClO}_2{^ - } \tag{1}\end{align*}\end{document}

FIG. 3.

Effect of BaP removal at 20°C, ClO₂ dosage of 5 mg/L, and reaction time of 120 min.

For pH≤2.0, ClO₂ can be reduced to Cl⁻ by gaining 5 mol electrons per mole of ClO₂ as \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland, xspace} \usepackage{amsmath, amsxtra} \pagestyle{empty} \DeclareMathSizes {10} {9} {7} {6} \begin{document} \begin{align*}{ \rm ClO}_2 + 5e^ - + 4{ \rm H}^ + = { \rm Cl}^ - + 2{ \rm H}_2{ \rm O} \tag{2}\end{align*}\end{document}

For pH>9.0, ClO₂ will proceed with a disproportionating reaction as \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland, xspace} \usepackage{amsmath, amsxtra} \pagestyle{empty} \DeclareMathSizes {10} {9} {7} {6} \begin{document} \begin{align*}2{ \rm ClO}_2 + 2{ \rm OH}^ - = { \rm ClO}_2{^ - } + { \rm ClO}_3{^ - } + { \rm H}_2{ \rm O} \tag{3}\end{align*}\end{document}

Overall, the effect of pH on BaP removal by ClO₂ appears insignificant. Because BaP removal efficiency was higher than 95% for pH of 3.2–9.7, it can be concluded that ClO₂ can degrade BaP effectively over a wide pH range.

Kinetics of BaP oxidation

This group of experiments was performed to determine the kinetics of ClO₂ oxidation at the condition of 20°C and pH 7.2. The initial concentration of BaP in the samples was 0.2 μmol/L, whereas initial ClO₂ dosages ([ClO₂]₀) were kept at 0.08, 0.12, 0.16, 0.20, and 0.24 mmol/L. Figure 4 reveals the BaP concentration time profiles at various initial ClO₂ concentrations, suggesting that the reaction could attain equilibrium within 30 min.

FIG. 4.

Variation of BaP concentration with time under different ClO₂ dosages at pH 7.2, 20°C, and initial BaP concentration of 0.2 μmol/L.

By plotting the experimental data of −lnC_t/C₀ (C_t denotes the concentration of BaP at time t, and C₀ denotes the initial concentration of BaP) versus reaction time (t), the linear correlation between the two variables can be identified, as indicated by correlation coefficients (r) above 0.97 (Fig. 5). Therefore, this reaction can be described with pseudo-first-order kinetics to BaP judged from the nature of first-order reaction.

FIG. 5.

Determination of kinetic constants and reaction order for BaP degradation at different ClO₂ dosages.

The slopes of the regressive lines shown in Fig. 5 demonstrate apparent first-order rate constants k′. As can be seen from k′ as function of [ClO₂]₀ (Fig. 6; y=−0.0029+0.48x, r²=0.9947), this reaction is also determined to be governed by a pseudo-first-order process for ClO₂.

FIG. 6.

Determination of reaction order for ClO₂ oxidation.

Taken together, the reaction is pseudo-first order to both ClO₂ and BaP, and thus the overall reaction is the second order. The rate equation can be written as \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland, xspace} \usepackage{amsmath, amsxtra} \pagestyle{empty} \DeclareMathSizes {10} {9} {7} {6} \begin{document} \begin{align*}- \ln \frac { C_t } { C_0 } = k [{\rm ClO}_2 ] t \tag {4} \end{align*}\end{document}

where [ClO₂] can be taken into account as a constant as [ClO₂]₀>> C₀ in the experiment; hence, \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland, xspace} \usepackage{amsmath, amsxtra} \pagestyle{empty} \DeclareMathSizes {10} {9} {7} {6} \begin{document} \begin{align*}k = k^{ \prime} / [{\rm ClO}_2 ] _0 \tag{5}\end{align*}\end{document}

Eq. 5 can thus be used to determine the second-order reaction rate constant k and the parameters are listed in Table 1. The average k is 7.795 L/(mol·s). All these results indicate that BaP removal can be accomplished in a short reaction time in normal water treatment condition.

Table 1.

Second-Order Reaction Rate Constant (k) of Benzo[a]pyrene Oxidation at Different Chlorine Dioxide Dosages

No.	[ClO₂]₀ (mmol/L)	Regression equation	r	k (L/(mol·s))
1	0.08	−ln(C_t/C₀)=0.1819+0.0374x	0.9812	7.792
2	0.12	−ln(C_t/C₀)=0.2595+0.0549x	0.9751	7.625
3	0.16	−ln(C_t/C₀)=0.2685+0.0746x	0.9884	7.771
4	0.20	−ln(C_t/C₀)=0.3653+0.0926x	0.9886	7.717
5	0.24	−ln(C_t/C₀)=0.3481+0.1162x	0.9923	8.069

[ClO₂]₀, initial chlorine dioxide dosage.

Identification of the products of BaP decomposition

In our previous study, the products of anthracene and benzo[a]-anthracene oxidized by ClO₂ were characterized as 9,10-anthraquinone and benzo[a]-anthracene-5,7-quinone plus benzo[a]-anthracene-7,12-quinone, respectively (Liu et al., 2007). Using the GC-MS analysis, two types of intermediate species, that is, benzo[a]-pyrene-1,6-quinone and benzo[a]-pyrene-6,12-quinone, were detected (Fig. 7), which appears quite similar to the results previously reported. The net charges of each atom involved in BaP illustrated in Fig. 8 were calculated using Chemoffice software, and the results are listed in Table 2. During the formation of quinone derivatives, carbonyls occurred predominately at the carbon atoms with more negative charge; hence, we assume that the atoms with more negative charges provide electrons, and the reaction activity is higher when there is more negative charge. It has been reported that these quinone derivatives lead to slight mutagenicity and cytotoxicity (Wislocki et al., 1976).

FIG. 7.

Schematic representation of BaP degradation by ClO₂.

FIG. 8.

Chemical structure of BaP molecule, and carbon and hydrogen atom distribution.

Table 2.

Net Charge of Atoms in Benzo[a]pyrene (eV)

Atom no.	Net charge
1	−0.1677
2	−0.0812
3	−0.1407
4	−0.1645
5	−0.1235
6	−0.2594
7	−0.1604
8	−0.0902
9	−0.1315
10	−0.0986
11	−0.0879
12	−0.167
13	0.0572
14	0.0192
15	0.0205
16	0.0726
17	−0.0224
18	−0.0408
19	0.1218
20	−0.0195
21	0.1278
22	0.1123
23	0.1188
24	0.1324
25	0.1233
26	0.1456
27	0.1228
28	0.1112
29	0.1184
30	0.1073
31	0.115
32	0.1292

Conclusion

Based on the experiments conducted on ClO₂ for oxidizing BaP in water, the conclusion can be drawn as follows. ClO₂ can remove BaP in water effectively under ordinary potable water treatment conditions. The main factors are ClO₂ dosage and reaction time. The reaction between BaP and ClO₂ is characterized as the second order with the reaction rate of 7.795 L/(mol·s). It can proceed so fast, such that above 90% BaP can be removed in 10 min. The end products of BaP-ClO₂ reaction are nontoxic quinone derivatives. This study proposed ClO₂ as an effective alternative to eliminate BaP for the general water treatment. Future work will focus on scaling up the system on BaP removal by ClO₂ in potable water treatment processes.

Footnotes

Acknowledgments

This study was funded by the National Hi-Tech Research and Development Program of China (2006AA06Z309) and State Key Lab of Urban Water Resource and Environment (HIT) (No. ES200903).

Author Disclosure Statement

The authors declare that no competing financial conflicts exist.

References

Bang

H.W.

, Lee

, Kwak

I.S.

2009. Detecting points as developmental delay based on the life-history development and urosome deformity of the harpacticoid copepod, Tigriopus japonicus sensu lato, following exposure to benzo(a)pyrene. Chemosphere, 76:1435.

Ganiev

I.M.

, Ganieva

E.S.

, Kabal'nova

N.N

. 2004. Oxidation of phenols with chlorine dioxide. Russ. Chem. Bull., 53:2281.

Hakami

, Mohtadini

, Etemadi

, Kamangar

, Nemati

, Pourshams

, Islami

, Nasrollahzadeh

, Saberi

F.M.

, Birkett

, Boffetta

, Malekzadeh

2008. Dietary intake of benzo(a)pyrene and risk of esophageal cancer in North of Iran. Nutr. Cancer, 60:216.

Homem

, Dias

, Santos

, Alves

2009. Preliminary feasibility study of benzo(a)pyrene oxidative degradation by Fenton treatment. J. Environ. Public Health, 2009:149034.

Hrudey

S.E.

2009. Chlorination disinfection by-products, public health risk tradeoffs and me. Water Res., 43:2057.

Huang

2010. Water Disinfection and Treatment Agent—Chlorine Dioxide. Beijing: China Architecture & Building Press.

, Huang

, Fu

, Wu

, Cui

2008. Degradation of microcystin-RR in water by chlorine dioxide. Min. Sci. Tech., 18:623.

Jiang

, Martens

, Schramm

K.W.

, Kettrup

, Xu

S.F.

, Wang

L.S.

2000. Polychlorinated organic compounds (PCOCs) in waters, suspended solids and sediments of the Yangtse Rive. Chemosphere, 41:901.

Juhasz

A.L.

, Naidu

2000. Bioremediation of high molecular weight polycyclic aromatic hydrocarbons: a review of the microbial degradation of benzo[a]pyrene. Int. Bioderter. Biodegr., 45:57.

10.

Kim

K.B.

, Lee

B.M.

1997. Oxidative stress to DNA, protein, and antioxidant enzymes (superoxide dismutase and catalase) in rats treated with benzo(a)pyrene. Cancer Lett., 113:205.

11.

Knafla

, Phillipps

K.A.

, Brecher

R.W.

, Petrovic

, Richardson

2006. Development of a dermal cancer slope factor for benzo[a]pyrene. Regul. Toxicol. Pharm., 45:159.

12.

Kometani

, Yoshino

, Miura

, Okazaki

, Ohba

, Takenaka

, Shoji

, Yano

, Maehara

2009. Benzo[a]pyrene promotes proliferation of human lung cancer cells by accelerating the epidermal growth factor receptor signaling pathway. Cancer Lett., 278:27.

13.

Liu

, Huang

, Su

, Cao

, Ji

2007. Degradation of anthracene, pyrene and benzo[a]-anthracene in aqueous solution by chlorine dioxide. Sci. Chin. Ser. B: Chem., 49:565.

14.

Luca

G.D.

, Sacchetti

, Zanetti

, Leoni

2008. Comparative study on the efficiency of peracetic acid and chlorine dioxide at low doses in the disinfection of urban wastewaters. Ann. Agr. Environ. Med., 15:217.

15.

Navalon

, Alvaro

, Garcia

2008. Chlorine dioxide reaction with selected amino acids in water J. Hazard. Mater., 164:1089.

16.

Perera

, Rauh

, Whyatt

R.M.

, Tang

, Tsai

W.Y.

, Bernert

J.T.

, Tu

Y.H.

, Andrews

, Barr

D.B.

, Camann

D.E.

, Diaz

, Dietrich

, Reyes

, Kinney

P.L.

2005. A summary of recent findings on birth outcomes and developmental effects of prenatal ETS, PAH, and pesticide exposures. Neurotoxicology, 26:573.

17.

Rafin

, Veignie

, Fayeulle

, Surpateanu

2009. Benzo[a]pyrene degradation using simultaneously combined chemical oxidation, biotreatment with Fusarium solani and cyclodextrins. Bioresour. Technol., 100:3157.

18.

Reynaud

, Deschaux

2006. The effects of polycyclic aromatic hydrocarbons on the immune system of fish: A review. Aquat. Toxicol., 77:229.

19.

Saunders

C.R.

, Ramesh

, Shockley

D.C.

2002. Modulation of neurotoxic behavior in F-344 rats by temporal disposition of benzo(a)pyrene. Toxicol. Lett., 129:33.

20.

Schmitz

S.S.

, Pink

, Rettenmeier

A.W.

2009. Proteomic study and correlated signalling network analysis of human bladder cancer cell line (RT4) exposed to benzo(a)pyrene. Toxicol. Lett., 182:13.

21.

Sigounas

, Hairr

J.W.

, Cooke

C.D.

, Owen

J.R.

, Asch

A.S.

, Weidner

D.A.

, Wiley

J. E.

2010. Role of benzo[α]pyrene in generation of clustered DNA damage in human breast tissue. Free Radical Biol. Med., 49:77.

22.

, Li

, Wang

, Xu

H.X.

2007. Degradation and kinetics of pyrene and benzo [a] pyrene by three bacteria in contaminated soil. Huan Jing Ke Xue, 28:913(Chinese).

23.

Sutherland

J.B.

1992. Detoxification of polycyclic aromatic hydrocarbons by fungi. J. Ind. Microbiol. Biotechnol., 9:53.

24.

Tang

, Donnelly

K.C.

, Tiffany-Castiglioni

, Mumtaz

M.M.

2003. Neurotoxicity of polycyclic aromatic hydrocarbons and simple chemical mixtures. J. Toxicol. Environ. Health A, 66:919.

25.

Trapido

, Veressinina

, Munter

1995. Ozonation and advanced oxidation processes of polycyclic aromatic hydrocarbons in aqueous solutions—a kinetic study. Environ. Technol., 16:729.

26.

Wang

, Gong

, Li

, Zhang

, Hu

2008. Degradation of pyrene and benzo(a)pyrene in contaminated soil by immobilized fungi. Environ. Eng. Sci., 25:677.

27.

Wislocki

P.G.

, Wood

A.W.

, Chang

R.L.

, Levin

, Yagi

, Hernandez

, Dansette

P.M.

, Jerina

D.M.

, Conney

1976. Mutagenicity and cytotoxicity of benzo(a)pyrene arene oxides, phenols, quinones, and dihydrodiols in bacterial and mammalian cells. Cancer Res., 36:3350.

28.

Zanga

, Li

, Zhang

, Hamilton

2007. Degradation mechanisms of benzo[a]pyrene and its accumulated metabolites by biodegradation combined with chemical oxidation. Chemosphere, 67:1368.

Effects and Kinetics of Chlorine Dioxide for Removal of Benzo[a]pyrene in Water

Abstract

Abstract

Introduction

Materials and Methods

Chemicals

Analytics and measurements

Results and Discussion

The effect of ClO2 on BaP removal

Kinetics of BaP oxidation

Identification of the products of BaP decomposition

Conclusion

Footnotes

Acknowledgments

Author Disclosure Statement

References

The effect of ClO₂ on BaP removal