The role of carbonate in sulfamethoxazole degradation by peroxymonosulfate without catalyst and the generation of carbonate racial.

Peroxymonosulfate (PMS) can be activated by various catalysts to degrade organic contaminants in wastewater treatment processes. In this research, the co-activation of PMS by sulfamethoxazole (SMX) and carbonate is investigated. The results show that SMX can be degraded in situ, and the main reactive oxygen species are singlet oxygen and carbonate radicals. Only singlet oxygen is detected when SMX is degraded by PMS without carbonate. However, both carbonate radicals and hydroxyl radicals are measured in the presence of carbonate. Among which, hydroxyl radicals are identified by electron paramagnetic resonance spectroscopy method, and carbonate radicals are confirmed by radical quenching experiments, as well as the variation of SMX degradation kinetic and the appreance of carbonyldioxy derivatives by-products in the presence of carbonate anions. Based on this phenomenon, it is proposed that carbonate can enhance the decomposition of PMS and the generation of secondary free radicals (carbonate radicals). Thus carbonate radicals can enhance the oxidizability for sulfonamide antibiotics in the PMS-based advanced oxidation systems. These results suggest that the addition of carbonate is an important enhancement method for the treatment of sulfonamide antibiotics in water.