Mechanisms of iopamidol transformation catalyzed by a copper corrosion product (c-Cu2O) during peroxymonosulfate disinfection

Peroxymonosulfate (PMS) is an alternative disinfectant for drinking water . This study aimed to investigate the transformation of iopamidol (IPM) catalyzed by a main copper corrosion product ( c -Cu 2 O) with PMS as a disinfectant. The observed pseudo-first-order constant ( k obs ) for the IPM degradation in the c -Cu 2 O/PMS system (0.033 min −1 ) was 3 times that in the CuO/PMS system (0.011 min −1 ). The quenching tests and the electron paramagnetic resonance (EPR) experiments indicate that O 2 •− and 1 O 2 contributed to IPM degradation in the c -Cu 2 O/ PMS system. The complexation of metastable Cu(II) with a PMS molecule polarized the O O bond and then facilitated the electron transfer from the PMS molecule to other PMS and O 2 molecules, which directly and indirectly promoted the yield of O 2 •− and 1 O 2 . The iodine balance indicated that 26.0% of initial TOI was converted to IO 3 − , and CHI 3 only accounted for 0.6% of the residual TOI. In the c -Cu 2 O/PMS system, IPM conversion was started with amide C−N bond breakage, deiodination reaction and hydrogen abstraction. This study helps to better understand the conversion mechanisms of iodine-containing organic micropollutants when PMS is deployed as a disinfectant in copper pipes.