Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Oxidative degradation of iodinated X-ray contrast media (iomeprol and iohexol) with sulfate radical: An experimental and theoretical study Xiaoxiao Wang a , Zhaohui Wang a,b,c, ⁎ ,YizhenTang d , Dongxue Xiao e ,DongZhang e ,YingHuang a , Yaoguang Guo f , Jianshe Liu a,g a State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China b Shanghai Key Laboratory of Urbanization and Ecological Restoration, School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200241, China c Institute of Eco-Chongming (IEC), Shanghai 200062, China d School of Environmental and Municipal Engineering, Qingdao University of Technology, Fushun Road 11, 266033 Qingdao, China e Chinese Academy of Fishery Sciences, East China Sea Fisheries Research Institute, Shanghai 200090, China f School of Environmental and Materials Engineering, Shanghai Polytechnic University, Shanghai 201209, China g Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China HIGHLIGHTS • Iomeprol and iohexol can be efec- tively degraded by Co(II)-activated PMS. • IO 3 − is the major inorganic iodine released from iomeprol and iohexol. • The possible transformation pathways of iomeprol and iohexol are proposed. • Preferential deiodination order is the- oretically predicted. GRAPHICALABSTRACT ARTICLEINFO Keywords: Sulfate radical Iodinated X-ray contrast media Iodinated by-products Degradation pathways Theoretical calculations ABSTRACT Ithasalreadybeenknownthatoxidativedegradationoforganochlorine(e.g.chlorophenols)isaccompaniedby de novo formation of new polychlorinated compounds, however, whether the similar scenario can happen duringdecompositionofiodine-containingpollutantsiscompletelyunknown.Heredegradationoftwoiodinated X-ray contrast media (ICM), iomeprol and iohexol, by sulfate radical generated through Co(II)-mediated acti- vation of peroxymonosulfate (PMS) was investigated. The infuencing parameters, such as the initial con- centrationsofPMSandCo(II),theinitialsolutionpHandnaturalwaterconstituentswereexamined.Thepseudo- frst-order rate constant of iomeprol in the PMS/Co(II) system is more than twice of iohexol, with values of 7.7×10 −2 and3.5×10 −2 min −1 , respectively, indicating that iomeprol seems more susceptible to radicals attack than iohexol. The bimolecular rate constants for reaction of sulfate radical (SO 4 •− ) with ICM were de- termined to be 1.8×10 10 M −1 s −1 and 7.9 ×10 9 M −1 s −1 for iomeprol and iohexol, respectively. The low degreesofmineralizationandidentifcationofiodinatedintermediatesofiomeprolandiohexolindicatethatthe degradation of iomeprol and iohexol in the Co/PMS system were incomplete. A de novo formation of new polyiodinatedcompoundswouldnothappenbecausemostofreleasedinorganiciodinewereultimatelyoxidized to iodate (IO 3 − ), rather than the reactive iodinated agents. Based on the identifed byproducts and quantum https://doi.org/10.1016/j.cej.2019.02.194 Received 29 July 2018; Received in revised form 23 February 2019; Accepted 26 February 2019 ⁎ Corresponding author. E-mail address: zhwang@des.ecnu.edu.cn (Z. Wang). Chemical Engineering Journal 368 (2019) 999–1012 Available online 26 February 2019 1385-8947/ © 2019 Elsevier B.V. All rights reserved. T