Copper in LaMnO3 to promote peroxymonosulfate activation by regulating the reactive oxygen species in sulfamethoxazole degradation

Perovskites with flexible texture structures and excellent catalytic properties have attracted considerable attention in peroxymonosulfate (PMS) activation for addressing organic contaminants in water. In this study, the role of copper to promote PMS activation performance of LaMnO3 was investigated. 100% sulfamethoxazole (SMX) degradation and 34% mineralization were achieved over copper doped LaMnO3 while only 60% SMX was removed without TOC removal by LaMnO3. Especially, compared with LaMnO3, the pseudo-first-order reaction rate constant was increased by 8.30 times when the atomic ratio of Cu/Mn was 1:3. It proved that only 1O2 was generated in LaMnO3 while 1O2, especially •OH and SO4•- were all detected in Cu-LaMnO3/PMS system. The characterization results showed that Cu induced the formation of LaMnO3 and La2CuO4 heterostructure with enhanced content of relatively low-valence Mn and Cu and abundant oxygen vacancies (OVs). Hence, the efficient PMS activation by Cu-LaMnO3 was due to regulating the produced reactive oxygen species (ROS). A radical dominant instead of 1O2 involved PMS activation mechanism over LaMnO3-La2CuO4 was proposed for efficient degradation of SMX. Finally, the possible degradation pathways of SMX were discussed based on HPLC-MS analysis. This study provided a new insight of improving the catalytic activity of perovskites in PMS activation in water treatment.