Effects of exogenic chloride on oxidative degradation of chlorinated azo dye by UV-activated peroxodisulfate

• Published in: Chinese chemical letters Vol. 32; no. 8; pp. 2544 - 2550
• Main Authors: Peng, Wenya, Fu, Yu, Wang, Lingli, Wang, Yifan, Dong, Yongxia, Huang, Ying, Wang, Zhaohui
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2021; Shanghai Engineering Research Center of Biotransformation of Organic Solid Waste,Shanghai 200241,China; Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration,School of Ecological and Environmental Sciences,East China Normal University,Shanghai 200241,China%School of Civil and Environmental Engineering,Ningbo University,Ningbo 315211,China%Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration,School of Ecological and Environmental Sciences,East China Normal University,Shanghai 200241,China; Technology Innovation Center for Land Spatial Eco-Restoration in Metropolitan Area,Ministry of Natural Resources,Shanghai 200062,China; Jiangsu Provincial Key Laboratory of Environmental Science and Engineering,Suzhou University of Science and Technology,Suzhou 215009,China
• Subjects: AOX; Chlorinated byproducts; Kinetics; Sulfate radical; Chlorinated byproducts; Sulfate radical; AOX; Kinetics
• ISSN: 1001-8417; 1878-5964
• DOI: 10.1016/j.cclet.2021.01.028

The chromophore and chlorine group of AY-17 dye are effectively attacked by sulfate radicals. Addition of exogenic Cl− can improve the mineralization rate, but leads to the formation of several polychlorinated organic by-products. [Display omitted] Recently, the degradation of organic compounds in saline dye wastewater by sulfate radicals (SO4−)-based advanced oxidation processes (AOPs) have attracted much attention. However, previous studies on these systems have selected non-chlorinated dyes as model compounds, and little is known about the transformation of chlorinated dyes in such systems. In this study, acid yellow 17 (AY-17) was selected as a model of chlorinated contaminants, and the degradation kinetics and evolution of oxidation byproducts were investigated in the UV/PDS system. AY-17 can be efficiently degraded (over 98% decolorization) under 90 min irradiation at pH 2.0–3.0, and the reaction follows pseudo-first order kinetics. Cl‒ accelerated the degradation of AY-17, but simultaneously led to an undesirable increase of absorbable organic halogen (AOX). Several chlorinated byproducts were identified by liquid chromatography-mass spectrometry (LC–MS/MS) in the UV/PDS system. It indicates that endogenic chlorine and exogenic Cl– reacted with SO4− to form chloride radicals, which are involved in the dechlorination and rechlorination of AY-17 and intermediates. The possible degradation mechanisms of AY-17 photooxidative degradation are proposed. This work provides valuable information for further studies on the role of exogenic chloride in the degradation of chlorinated azo dyes and the kinetic parameters in the PDS-based oxidation process.