Photocatalytic degradation of sulfonamides in 4-phenoxyphenol-modified g-C3N4 composites: Performance and mechanism

Significant quantities of sulfonamide antibiotics are continuously released into the ambient environment; thus, they have emerged as serious pollutants that may inflict ecological damage. Herein, 4-phenoxyphenol-modified g-C3N4 (PCN) was initially prepared via the copolymerization of dicyandiamide and 4-phenoxyphenol, which demonstrated excellent performance for light-harvesting and the promotion of photon-generated carrier separation. Optimized PCN exhibited 4.5-fold higher photocatalytic degradation activity for sulfisoxazole (SIZ) than pure g-C3N4 under blue-light (LED) irradiation. Among SIZ, sulfapyridine (SPD), sulfadiazine (SDZ) and sulfadimethazine (SMZ), SIZ and SMZ are more vulnerable to attack in PCN photocatalytic system due to structure containing methyl. Electron spin resonance and photoelectrochemical experiments revealed that the faster charge separation of PCN promoted the formation of additional reactive oxygen species. Moreover, the potential transformation pathways of SIZ were hypothesized through the frontier molecular orbital theory and HRAM LCMS/MS. Hence, the present work is expected to be of important reference value for sustainable environmental restoration.

Automated summary

The study successfully improved the degradation activity of sulfonamide antibiotics by preparing a special photocatalyst PCN, with SIZ and SMZ being vulnerable possibly due to their methyl-containing structure; the faster charge separation of PCN promoted the formation of additional reactive oxygen species.