Role of process parameters in the degradation of sulfamethoxazole by heat-activated peroxymonosulfate oxidation: Radical identification and elucidation of the degradation mechanism

The use of heat-activated peroxymonosulfate oxidation for the degradation of the antibiotic compound sulfamethoxazole (SMX) was studied in this paper. It was found that the degradation process follows a pseudo-first order kinetic model. Increasing the oxidant concentration and/or the activation temperature led to a higher sulfamethoxazole degradation efficiency. Increasing the pH from 3 to 9.5 resulted in a higher degradation efficiency as well, although the SMX degradation was significantly inhibited at a pH of 11. Through radical scavenging experiments, it was found that both •OH and •SO4− played a role in the SMX degradation mechanism. Seven transformation products were identified in the SMX degradation process. Both the radicals present and the initial pH value of the degradation process were found to influence the formation of several degradation products. Finally, the heat-activated peroxymonosulfate oxidation process was compared with the heat-activated persulfate process and the main intermediates formed in both processes were identified and compared with each other.