Abstract
It has already been known that oxidative degradation of organochlorine (e.g. chlorophenols) is accompanied by de novo formation of new polychlorinated compounds, however, whether the similar scenario can happen during decomposition of iodine-containing pollutants is completely unknown. Here degradation of two iodinated X-ray contrast media (ICM), iomeprol and iohexol, by sulfate radical generated through Co(II)-mediated activation of peroxymonosulfate (PMS) was investigated. The influencing parameters, such as the initial concentrations of PMS and Co(II), the initial solution pH and natural water constituents were examined. The pseudo-first-order rate constant of iomeprol in the PMS/Co(II) system is more than twice of iohexol, with values of 7.7 × 10−2 and 3.5 × 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 (SO4•−) with ICM were determined to be 1.8 × 1010 M−1 s−1 and 7.9 × 109 M−1 s−1 for iomeprol and iohexol, respectively. The low degrees of mineralization and identification of iodinated intermediates of iomeprol and iohexol indicate that the degradation of iomeprol and iohexol in the Co/PMS system were incomplete. A de novo formation of new polyiodinated compounds would not happen because most of released inorganic iodine were ultimately oxidized to iodate (IO3−), rather than the reactive iodinated agents. Based on the identified byproducts and quantum chemical calculation, eight main transformation pathways are proposed for the degradation of iomeprol and iohexol as follows: (a) deiodination; (b) hydrogen abstraction; (c) amide hydrolysis; (d) amino oxidation; (e) hydroxyl substituent; (f) transformed alkyl aromatic amides to aromatic carbamoyl; (g) dehydration; (h) oxidized primary alcohol groups to carboxyl groups.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.