Rapid degradation of brominated and iodinated haloacetamides with sulfite in drinking water

Degradation kinetics and mechanisms

Journal article (2018)

Authors

Shunke Ding Shanghai Institute of Pollution Control and Ecological Security, Tongji University
F. Wang Sanitary Engineering - CEG
Wenhai Chu Tongji University, Shanghai Institute of Pollution Control and Ecological Security
Zhongqi Cao Shanghai Institute of Pollution Control and Ecological Security, Tongji University
Yang Pan Nanjing University
Naiyun Gao Tongji University, Shanghai Institute of Pollution Control and Ecological Security
Research Group
Sanitary Engineering (CEG) (TU Delft)
Disinfection by-products Haloacetamides Reductive dehalogenation Sodium sulfite Sulfonate
More Info
expand_more

Published Date

15-10-2018

Language

English

Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Faculty

Civil Engineering & Geosciences

Department

Water Management

Research Group

Sanitary Engineering

Abstract

The effective removal of haloacetamides (HAMs) as a group of emerging disinfection by-products is essential for drinking water safety. This study investigated the degradation of 10 HAMs, including chlorinated, brominated, and iodinated analogues, by sodium sulfite (S(IV)) and the mechanism behind it. The results indicated that all HAMs, excluding chlorinated HAMs, decomposed immediately when exposed to S(IV). The reductive dehalogenation kinetics were well described by a second-order kinetics model, first-order in S(IV) and first-order in HAMs. The degradation rates of HAMs increased with the increase of pH and they were positively correlated with sulfite concentration, indicating that the reaction of S(IV) with HAMs mainly depends on sulfite. The rank order and relative activity of the reaction of sulfite with HAMs depends on bimolecular nucleophilic substitution reaction reactivity. The order of the reductive dehalogenation rates of HAMs versus the substitution of halogen atoms was iodo- > bromo- >> chloro-. During reductive dehalogenation of HAMs by sulfite, the α-carbon bound to the amide group underwent nucleophilic attack at 180° to the leaving group (halide). As a consequence, the halide was pushed off the opposite side, generating a transition state pentacoordinate. The breaking of the C-X bond and the formation of the new C-S bond occurred simultaneously and HAM sulfonate formed as the immediate product. Results suggest that S(IV) can be used to degrade brominated and iodinated HAMs in drinking water and therefore should not be added as a quenching agent before HAM analysis to accurately determine the HAM concentrations produced during water disinfection.