Rationally designed S-scheme heterojunction of BiOCl/g-C_(3)N_(4)for photodegradation of sulfamerazine:Mechanism insights,degradation pathways and DFT calculation

Antibiotics present in surface water have detrimental effects on both human health and the ecosystem.Additionally,they pose a threat to the effectiveness of biological water treatment processes.In this study,a visible photocatalytic system with Bi OCl/g-C_(3)N_(4)heterojunction was developed to remove sulfonamide antibiotic sulfamerazine(SMZ)in water.The removal rate reached 92.77%under visible light irradiation for 80 min.This photocatalyst remained active after 5 cycles of experiments and maintained a relatively stable removal rate of SMZ of over 80%.The ESR tests indicate that the main active species in this photocatalytic system were h^(+)and^(·)O_(2)^(-).The enhanced photocatalytic efficiency was mainly ascribed to the formation of a built-in electric field between Bi OCl and g-C_(3)N_(4)through the carrier transport mechanism of the S-scheme heterojunction.This heterojunction facilitated the photogenerated carrier shift and segregation,and improved the interfacial charge transfer efficiency,as confirmed by photoelectrochemical test and Density functional theory(DFT)calculations.The HPLC-QTOF-MS/MS and DFT analysis revealed possible degradation pathways of SMZ may involve deamination,hydroxylation,SO_(2)extrusion and bond breaking.This novel Bi OCl/g-C_(3)N_(4)heterojunction has proven to be essential for efficient visible-light photocatalysis.