Elucidating the enhanced role of carbonate radical in propranolol degradation by UV/peroxymonosulfate system

Carbonate radical (CO₃^•-) has been proved to be an important secondary radical in advanced oxidation processes due to various radical reactions involved HCO₃^-/CO₃^2-. However, the roles and contributions of CO₃^•- in organic micropollutant degradation have not been explored systematically. Here, we quantified the impact of CO₃^•- on the degradation kinetics of propranolol, a representative pollutant in the UV/peroxymonosulfate (PMS) system, by constructing a steady-state radical model. Substantially, the measured values were coincident with the predictive values, and the contributions of CO₃^•- on propranolol degradation were the water matrix-dependent. Propranolol degradation increased by 130% in UV/PMS system containing 10 mM HCO₃^-, and the contribution of CO₃^•- was as high as 58%. Relatively high pH values are beneficial for propranolol degradation in pure water containing HCO₃^-, and the contributions of CO₃^•- also enhanced, while an inverse phenomenon was shown for the effects of propranolol concentrations. Dissolved organic matter exhibited significant scavenging effects on HO^•, SO₄^•-, and CO₃^•-, substantially retarding the elimination process. The developed model successfully predicted oxidation degradation kinetics of propranolol in actual sewage, and CO₃^•- contribution was up to 93%, which in indicative of the important role of CO₃^•- in organic micropollutant removal via AOPs treatment.