Degradation of organic contaminants through activating bisulfite by cerium (IV): A sulfate radical-predominant oxidation process

In this study, the activation of bisulfite by cerium(IV) (Ce(IV)/HSO3- process) is proposed for the first time to degrade organic contaminants. Experiments show that carbamazepine (CBZ), a representative recalcitrant contaminant of emerging concern, is oxidized by Ce(IV)/HSO3- treatment at pH(ini) 3.0-7.0 when O-2(aq) is present to promote HSO3- autoxidation. SO4 center dot -, HO center dot, and SO5 center dot - were identified as active oxidants of CBZ based on the ESR spectra and the results of alcohol quenching experiments. Quantitative analysis indicates that SO4 center dot - plays a major role, while HO center dot and other species play minor roles in the degradation of CBZ in the Ce(IV)/HSO3- process. SO4 center dot - radicals are derived from the reaction of SO5 center dot - with HSO3- and the activation of hydrogen peroxomonosulfate (HSO5-) by Ce(IV). Five degradation pathways of CBZ are proposed based on transformation products identified by UPLC-QToF-MS/MS, and proposed sites for radical attack are supported by the results of frontier electron density calculations. Elevated concentrations of Cl-, Fe(III), and humic acid (HA) inhibit CBZ degradation, while other non-target solutes have minimal effects on CBZ degradation in the Ce(IV)/HSO3 process. Finally, experiments demonstrating degradation of a suite of other organic contaminants suggests that the Ce(IV)/HSO3- system can be applied as a new advanced oxidation process for wastewater treatment.