Chlorination decreases acute toxicity of iodophenols through the formation of iodate and chlorinated aliphatic disinfection byproducts. (15th April 2021)

• Record Type: Journal Article
• Authors: Wang, Xian-Shi; Song, Heng; Zhang, Jing; Liu, Yu-Lei; Ma, Jun; Wang, Lu
• Is Part Of: Water research. Volume 194(2021)
• Publication Date: 2021-04-15
• Subjects: Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2021.116951
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: HOCl was reactive with 2-iodophenol, 4-iodophenol and 2, 4, 6-triiodophenol Acute toxicity of iodophenols could be largely eliminated after chlorination Iodophenols were transformed into chlorinated aliphatic DBPs, iodinated-THMs and iodate The transformation products were verified with chemical standards Abstract: Highly toxic iodinated phenolic by-products were frequently detected in the oxidative treatment and disinfection of iodine-containing water. Herein, it was found that three model iodinated phenolic disinfection byproducts (DBPs), 2-iodophenol, 4-iodophenol and 2, 4, 6-triiodophenol, were reactive with HOCl, and the reaction rate constants (at pH 7.0 and 25℃) were 1.86 ×10 2, 1.62 ×10 2 and 7.5 ×10 1 M −1 s −1, respectively. When HOCl was in excess (HOCl/iodophenol = 40/1, [iodophenol]0 = 20 μM), acute toxicity of water sample containing iodophenols could be largely eliminated (> 85%), with the conversion of iodophenols into stable and non-toxic iodate (IO3 − ) and iodinated and chlorinated aliphatic DBPs. Besides IO3 −, seven kinds of aromatic intermediate products including iodophenols, chloroiodophenols, iodoquinones, chloroiodoquinones, chloroquinones, chlorophenols, and coupling products were detected. C-I bond of iodophenols was cleaved in the reaction and the resulted aromatic products were further transformed into chlorinated aliphatic DBPs [trichloromethane (TCM), trichloroacetic acid (TCAA), dichloroacetic acid (DCAA), and chloral hydrate (CH)] (mg/L level) and iodinated trihalomethanes (μg/L level). HOCl was effective for converting iodophenols into IO3 − and less toxic chlorinated aliphatic DBPs. Considering that chlorine was widely used as disinfectant, transformation and toxicity alteration of emerging DBPs during chlorination/booster chlorination warrant further investigations. Graphical abstract: Image, graphical abstract