A comprehensive insight into a rapid degradation of sulfamethoxazole by peroxymonosulfate enhanced UV-A LED/g-C3N4 photocatalysis

In this study, a strategy combining graphitic carbon nitride (g-C3N4) and peroxymonosulfate (PMS) under UV-A LED irradiation was proposed to effectively degrade sulfamethoxazole (SMX), which is a frequently detected antibiotic. The presence of PMS doubled the SMX degradation efficiency by the PMS/UV-A LED/g-C3N4 system, which exhibited considerable reactivity for SMX removal. SMX degradation was enhanced by increases in the PMS and g-C3N4 dosage, and by a decrease in the initial SMX concentration. pH also dramatically affected SMX degradation, as acidic and alkaline conditions favored SMX degradation. The presence of Cl− had a negligible impact on SMX degradation; natural organic matter (NOM) and NO3− decreased SMX degradation efficiency, and CO32− increased SMX degradation efficiency. The intermediates produced during SMX degradation were identified in the PMS/UV-A LED/g-C3N4 system, and the possible degradation pathways included hydroxylation, photoisomerization, aldehyde addition, and nitration. The toxicity of the products was estimated using antimicrobial activity tests and the ECOSAR program and indicate that the PMS/UV-A LED/g-C3N4 system efficiently reduced the antimicrobial activity of SMX. However, some intermediate products that retain toxicities can also been generated. This study provides a comprehensive insight into PMS/UV-A LED/g-C3N4 systems as a new strategy for antibiotic degradation.