Resolving the kinetic and intrinsic constraints of heat-activated peroxydisulfate oxidation of iopromide in aqueous solution

Zhaohui Wang; Xiaoxiao Wang; Ruixia Yuan; Dongxue Xiao

doi:10.1016/j.jhazmat.2019.121281

Resolving the kinetic and intrinsic constraints of heat-activated peroxydisulfate oxidation of iopromide in aqueous solution

J Hazard Mater. 2020 Feb 15:384:121281. doi: 10.1016/j.jhazmat.2019.121281. Epub 2019 Sep 23.

Authors

Zhaohui Wang¹, Xiaoxiao Wang², Ruixia Yuan³, Dongxue Xiao⁴

Affiliations

¹ Shanghai Key Laboratory of Urbanization and Ecological Restoration, School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200241, China; College of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China; Institute of Eco-Chongming (IEC), Shanghai 200062, China. Electronic address: zhwang@des.ecnu.edu.cn.
² College of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China.
³ College of Chemistry and Chemical Engineering, Northeast Petroleum University, Daqing, 163318, China.
⁴ Chinese Academy of Fishery Sciences, East China Sea Fisheries Research Institute, Shanghai 200090, China.

PMID: 31585288
DOI: 10.1016/j.jhazmat.2019.121281

Abstract

Iopromide (IOP) has been identified as one of the most persistent pharmaceuticals in wastewater treatment processes, however, kinetic and intrinsic factors constraining its fast removal in advanced oxidation processes (AOPs) are yet to be resolved. Here oxidation of IOP by heat-activated peroxydisulfate (PDS) was investigated both experimentally and theoretically. Rates of IOP degradation were enhanced by elevating solution temperature and acidity. An apparent kinetic rate equation was developed, based on the pseudo-first-order reaction model and assumption of steady state of SO₄^-. The common water constituents showed inhibitory effects on IOP decomposition to various extent. An insufficient supply of SO₄^- was considered as the major kinetic constraint. Eight byproducts were identified and most of which had intact triiodinated benzene ring. O-demethylation, oxidation of amino moiety and oxidation/elimination of alcohol groups are proposed as the primary degradation pathways, in accordance with the incomplete mineralization and non-detectable release of inorganic iodine. Quantum chemical calculations predict that oxidation of alkyl chains of IOP preferentially occurs and IOP byproducts with shorter side chains and intact triiodinated ring are more reactive than IOP. By virtue of the identified kinetic and intrinsic constraints, strategies to maximize degradation efficiency of IOP are proposed.

Keywords: Alkyl chain; Degradation pathway; Peroxydisulfate; Reaction orders.

Publication types

Research Support, Non-U.S. Gov't