The performance and process analysis of copper ion activated chlorine system in the removal of Iopamidol
A Cu(Ⅱ)--activated NaOCl system was established to oxidize iopamidol(IPM),one of the typical non-ionic iodine X-ray contrast agents.The effects of Cu(Ⅱ)and NaOCl concentrations,halide ions on the IPM oxidation,and the formation of iodine disinfection by-products(Iodoform,CHI3)were examined.In addition,the crystallographic and morphological changes of Cu(Ⅱ)after the reaction were analyzed to explore its recovery and recycling.Combined with the cyclic voltammetry curves and chronoamperometry,the formation of Cu(Ⅲ)was confirmed,and the mechanism of Cu(Ⅱ)-activated NaOCl for oxidizing IPM was speculated.The results showed that compared with that of Co(Ⅱ),Fe(Ⅱ),and Mn(Ⅱ),Cu(Ⅱ)significantly improved NaOCl decomposition and IPM degradation,with IPM removal reaching 77.51％in 60min under the experimental condition of 25℃,initial pH=6.71,500r/min,NaOCl and Cu(Ⅱ)concentrations of 0.5 and 0.05mmol/L,respectively.HO·,reactive chlorine radicals,and Cu(Ⅲ)all contributed to IPM degradation.Meanwhile,the contribution of Cu(Ⅲ)increased with pH value.IPM removal increased with NaOCl concentration in the range of 0.1～2.5mmol/L.There was an optimum value for Cu(Ⅱ)concentration between 0.005 and 0.5mmol/L.A total of 13 intermediates were detected through HPLC/MS/MS analysis,degradation of IPM mainly followed hydrolysis and oxidation of side-chain amide bonds,iodine substitution,and hydroxyl addition.Cl-,Br-,and I-(1～5mmol/L)not only affected the IPM removal but also the formation of CHI3,with the maximum CHI3 formation of 48.28μg/L in the Cu(Ⅱ)/NaOCl/Br-system.
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