Electrochemically reductive dechlorination of six dichlorophenol isomers:comparison of apparent kinetics

doi:10.11949/j.issn.0438-1157.20150031

Abstract

Abstract:

Chlorophenols are persistent organic pollutants with high toxicity. Dichlorophenols (DCPs) include six isomers due to different substituted position of chlorine atoms. Self-made Pd/polypyrrole(sodium dodecylbenzene sulfonate)/Ti electrode (Pd/PPy(SDBS)/Ti electrode) was employed to dechlorinate six DCP isomers. The effects of electrolysis current, initial pH and the initial concentration of target pollutant on the dechlorination process of 2,5-DCP were investigated. Under the selected conditions, i.e., applied current of 5 mA, initial pH of 2.5 and temperature of 25℃, dechlorination experiments of 2,3-DCP, 2,5-DCP, 2,4-DCP, 2,6-DCP, 3,4-DCP and 3,5-DCP with the same DCP concentration of 100 mg·L^-1 were conducted, respectively. Phenol was the main product and a small amount of monochlorophenol could be detected during the dechlorination of six DCPs. The reaction rate constants of six DCPs were 4.735×10^-2 min^-1, 4.609×10^-2 min^-1, 4.845×10^-2 min^-1, 4.317×10^-2 min^-1, 3.973×10^-2 min^-1 and 3.770×10^-2 min^-1, respectively. It showed that the degradation rates of DCPs were affected by pK_a, protonation and pH. The degradation difficulty of six DCPs was 2,4-DCP<2,3-DCP<2,5-DCP<2,6-DCP< 3,4-DCP<3,5-DCP.

Key words: chlorophenols, electrochemistry, catalytic reduction, reaction kinetics, rate constant

摘要：

采用自制的钯/聚吡咯(十二烷基苯磺酸钠)/钛(Pd/PPy(SDBS)/Ti)电极对二氯酚(DCP)的6种同分异构体进行了电化学还原脱氯研究。探讨了脱氯电流、溶液初始pH和污染物初始浓度对2,5-DCP脱氯过程的影响。在脱氯电流5 mA、溶液初始pH 2.5、温度25℃、污染物初始浓度100 mg·L^-1的条件下对2,3-DCP、2,4-DCP、2,5-DCP、2,6-DCP、3,4-DCP和3,5-DCP的脱氯过程进行了比较。6种DCP的脱氯产物均以苯酚为主,有少量的单氯酚产生,脱氯反应速率常数依次为4.735×10^-2、4.609×10^-2、4.845×10^-2、4.317×10^-2、3.973×10^-2、3.770×10^-2 min^-1。推测DCP的降解速率受pK_a、质子化效应和溶液pH等因素的影响,降解难度由小到大依次为2,4-DCP< 2,3-DCP< 2,5-DCP< 2,6-DCP< 3,4-DCP< 3,5-DCP。

关键词: 氯酚, 电化学, 催化还原, 反应动力学, 速率常数

CLC Number:

X131.2

ZHAO Sisi, WEI Xuefeng, SUN Zhirong. Electrochemically reductive dechlorination of six dichlorophenol isomers:comparison of apparent kinetics[J]. CIESC Journal, 2015, 66(11): 4452-4459.

赵思思, 魏学锋, 孙治荣. 6种二氯酚电催化还原脱氯:表观动力学过程比较[J]. 化工学报, 2015, 66(11): 4452-4459.

References 26

[1]	Igbinosa E O, Odjadjare E E, Chigor V N, Igbinosa I H, Emoghene A O, Ekhaise F O, Igiehon N O, Idemudia O G. Toxicological profile of chlorophenols and their derivatives in the environment: the public health perspective [J]. Scientific World Journal,2013, 2013: 460215.
[2]	Pi Yunzheng(皮运正), Wang Jianlong(王建龙). The mechanism and pathway of the ozonation of 4-chlorophenol in aqueous solution [J]. Science in China Series B: Chemistry (中国科学B辑:化学), 2006, 36(1): 87-92.
[3]	Järvinen K T, Puhakka J A. Bioremediation of chlorophenol contaminated ground water [J]. Environmental Technology, 1994, 15(9): 823-832.
[4]	Kuo W S, Lin I T. Biodegradability of chlorophenol wastewater enhanced by solar photo-Fenton process [J]. Water Science and Technology, 2009, 59(5): 973-978.
[5]	Thakur C, Dembla A, Srivastava V C, Mall I D. Removal of 4-chlorophenol in sequencing batch reactor with and without granular-activated carbon [J]. Desalination and Water Treatment, 2014, 52(22/23/24): 4404-4412.
[6]	Gaya U I, Abdullah A H, Zainal Z, Hussein M Z. Photocatalytic treatment of 4-chlorophenol in aqueous ZnO suspensions: intermediates, influence of dosage and inorganic anions [J]. Journal of Hazardous Materials, 2009, 168(1): 57-63.
[7]	Rashid J, Barakat M A, Pettit S L, Kuhn J N. InVO4/TiO2 composite for visible-light photocatalytic degradation of 2-chlorophenol in wastewater [J]. Environmental Technology, 2014, 35(17): 2153-2159.
[8]	Zhang L Z, Zeng H H, Zeng Y M, Zhang Z H, Zhao X F. Heterogeneous Fenton-like degradation of 4-chlorophenol using a novel Fe-Ⅲ-containing polyoxometalate as the catalyst [J]. Journal of Molecular Catalysis A: Chemical, 2014, 392: 202-207.
[9]	Zhang W H, Quan X, Zhang Z Y. Catalytic reductive dechlorination of p-chlorophenol in water using Ni/Fe nanoscale particles [J]. Journal of Environmental Sciences, 2007, 19(3): 362-366.
[10]	Feng L, Ge X P, Li Y, Wang D S, Tang H X. Dechlorination of 2,4-dichlorophenol by nickel nanoparticles under the acidic conditions [J]. Chinese Science Bulletin, 2011, 56(21): 2258-2266.
[11]	Yang B, Deng S B, Yu G, Lu Y H, Zhang H, Xiao J Z, Chen G, Cheng X B, Shi L L. Pd/Al bimetallic nanoparticles for complete hydrodechlorination of 3-chlorophenol in aqueous solution [J]. Chemical Engineering Journal, 2013, 219: 492-498.
[12]	Dabo P, Cyr A, Laplante F, Jean F, Menard H, Lessard J. Electrocatalytic dehydrochlorination of pentachlorophenol to phenol or cyclohexanol [J]. Environmental Science & Technology, 2000, 34(7): 1265-1268.
[13]	Cui C Y, Quan X, Yu H T. Electrocatalytic hydrodehalogenation of pentachlorophenol at palladized multiwalled carbon nanotubes electrode [J]. Applied Catalysis B: Environmental, 2008, 80(1/2): 122-128.
[14]	Yang Bo(杨波). Electrocatalytic reductive dechlorination of polychlorinated biphenyls by palladium-modified electrode [D]. Beijing: Tsinghua University, 2007.
[15]	Zheng Q, Wang L S. Studies on the quantitative structure-activity relationship of toxicity of chlorophenol serial compounds in the ab initio methods and substitutive position of chlorine atom(N-PCS) [J]. Chinese Journal of Structural Chemistry, 2007, 26(8): 933-938.
[16]	Wei X F, Du R, Sun Z R, Hu X. Optimization of a Pd-loaded composite electrode for reductive dechlorination of 2,4-dichlorophenol in neutral aqueous solution [J]. Fresenius Environmental Bulletin, 2015, 24(2): 539-545.
[17]	Sun Z R, Ge H, Hu X, Peng Y Z. Electrocatalytic dechlorination of chloroform in aqueous solution on palladium/titanium electrode [J]. Chemical Engineering & Technology, 2009, 32(1): 134-139.
[18]	Cong Yanqing(丛燕青). Degradation and treatment of chlorophenols by electrochemcial technologies [D]. Hangzhou: Zhejiang University, 2005.
[19]	Zhu K R, Baig S A, Xu J, Sheng T T, Xu X H. Electrochemical reductive dechlorination of 2,4-dichlorophenoxyacetic acid using a palladium/nickel foam electrode [J]. Electrochimica Acta, 2012, 69: 389-396.
[20]	Han J, Deming R L, Tao F M. Theoretical study of molecular structures and properties of the complete series of chlorophenols [J]. Journal of Physical Chemistry A, 2004, 108(38): 7736-7743.
[21]	Zhang Q Z, Qu X H, Wang H, Xu F, Shi X Y, Wang W X. Mechanism and thermal rate constants for the complete series reactions of chlorophenols with H [J]. Environmental Science & Technology, 2009, 43(11): 4105-4112.
[22]	He Zhong(何忠), Yang Shaogui(杨绍贵), Sun Cheng(孙成). Microwave-assisted photocatalytic degradation of tetrachlorophenol in aqueous Bi2WO6 suspensions [J]. Environmental Science & Technology(环境科学与技术), 2009, 32(11): 40-43.
[23]	Ugland K, Lundanes E, Greibrokk T, Bjorseth A. Determination of chlorinated phenols by high-performance liquid chromatography [J]. Journal of Chromatography, 1981, 213(1): 83-90.
[24]	Dombek T, Dolan E, Schultz J, Klarup D. Rapid reductive dechlorination of atrazine by zero-valent iron under acidic conditions [J]. Environmental Pollution, 2001, 111(1): 21-27.
[25]	Tishchenko O, Pham-Tran N N, Kryachko E S, Nguyen M T. Protonation of gaseous halogenated phenols and anisoles and its interpretation using DFT-based local reactivity indices [J]. Journal of Physical Chemistry A, 2001, 105(38): 8709-8717.
[26]	Li Z H, Matoska S J, Rohrer H. Effects of solution pH on adsorption of chlorophenols by cross-linked polyvinyl pyrrolidone (PVP XL) polymers [J]. Environmental Progress & Sustainable Energy, 2011, 30(3): 416-423.