The solar/chlorine system degradation of iopamidol: Roles of reactive species, degradation pathway, and toxicity

Abstract

The study systematically examined the changing trends of the percentage contributions of reactive species to the degradation of Iopamidol (IPM) under various conditions in the solar/chlorine system. Results showed that compared with chlorine alone and solar radiation system, the solar/chlorine system had an obvious effect on the degradation of IPM under control experiment conditions. HO• and reactive chlorine species played major roles in the apparent pseudo-first-order rate constants of IPM degradation (kobs). The increase of oxidant dosage significantly promoted the steady-state concentration of RCS and the contributions of those to kobs. The concentrations of various radicals at pH 9 were lower than those of at pH 5, while only the percentage contribution of ClO• on kobs was increased. The presence of Cl- could increase the steady-state concentration of Cl•, which further promoted the kobs. NOM would significantly reduce the steady-state concentration of ClO• and Cl•, which leads to a significant increase in the percentage contribution of Cl2−• to kobs, indicating the important role of Cl2−• on organic removal in real water. HCO3-/CO32- had almost no effect on kobs. The degradation products of IPM were identified through HPLC-MS, and the Fukui function was employed to ascertain the sites of degradation, which were formulated by deiodination reactions and the production of organic radicals. According to structure Activity Relationships Program v.2.2 and acute toxicological tests, byproducts did not exhibit significant toxicity. The findings illustrate that the solar/chlorine system is effective in decomposing IPM into non-toxic and non-hazardous small molecules, with potential applications.