A Kinetic and Mechanismic Study of Plasma-Induced Degradation of Monochloropropionic Acids in Water by Means of Anodic Contact Glow Discharge Electrolysis

Haiming Yang,Lixiang Li,Maowei Ju,Baigang An,Xiaotong Zhao,Shaoyan Wang

doi:10.1155/2016/9615865

Abstract

Decomposition of aqueous monochloropropionic acids (MCPAs) was investigated by means of anodic contact glow discharge electrolysis (CGDE). With the decay of MCPAs, the corresponding total organic carbon (TOC) also decreased smoothly. Furthermore, it was found that chlorine atoms in the MCPAs were released as chloride ions. As the main by-products, oxalic acid and formic acid were detected. The acetic acid (CA), monochloroacetic acid (MCA), and propanedioic acid (PDA) were also detected as the primary intermediates for decomposition of the corresponding MCPAs. The decay of both MCPAs and TOC obeyed the first-order kinetics, respectively. The apparent rate constant for the decay of MCPAs increased with the increase inpKavalues of MCPAs, while that for the decay of TOC was substantially unaffected. The reaction pathway involving the successive attack of hydroxyl radical and the carbon chain cleavage were discussed based on the products and kinetics.

Highlights

Chlorinated organic compounds (COCs), including chlorinated aromatic compounds (CACs) and chloroalkyl carboxylic acids (CACAs), have been used in polymer materials, herbicides, fungicides, insecticides, and solvents
The degradation of CACs had been systemically studied by both bioprocesses and advanced oxidation processes (AOPs) [6,7,8,9,10,11,12,13], while, for CACAs, the studies were focusing on chloroacetic acids with two carbon atoms in the carbon chain [14, 15]
Based on the product survey, it can be assumed that degradation of aqueous monochloropropionic acids (MCPAs) by contact glow discharge electrolysis (CGDE) proceeds in a successive manner as follows: (1) hydroxylation of MCPAs giving rise to substitution reaction of hydrogen or chlorine atom in the carbon chain, subsequently (2) oxidative carbon chain cleavage leading to the formation of carboxylates that includes oxalic acid and formic acid, and (3) mineralization to inorganic carbon (IC) and Cl−

Summary

Introduction

Chlorinated organic compounds (COCs), including chlorinated aromatic compounds (CACs) and chloroalkyl carboxylic acids (CACAs), have been used in polymer materials, herbicides, fungicides, insecticides, and solvents. The degradation of CACs had been systemically studied by both bioprocesses and advanced oxidation processes (AOPs) [6,7,8,9,10,11,12,13], while, for CACAs, the studies were focusing on chloroacetic acids with two carbon atoms in the carbon chain [14, 15]. Lei et al studied the decomposition of trichloroacetic acid (TCA) in water by CGDE [39]; our group reported the degradation of MCA [40]. The comprehensive degradation of two monochloropropionic acids (MCPAs), typical CACAs with three carbon atoms in the carbon chain, by means of anodic CGDE is investigated. The study mainly focused on the cleavage of the carbon chain and kinetic aspects

Experimental

Results and Discussion

H Cl OHCCC OH

Conclusions