In-situ synthesis of AgCl/WO3 loaded with g-C3N4 as dual Z-scheme heterojunction for boosting photocatalytic degradation of antibiotics

In this study, a new construction of dual Z-scheme heterojunction AgCl/WO3/g-C3N4 (AWC) was synthesized via a two-step process comprising hydrothermal treatment and ball milling for tetracycline (TC) and oxytetracycline (OTC) degradation. The effects of Ag:W molar ratio and the mass ratio of g-C3N4 on the crystal structure, microstructure, optical and photoelectrochemical properties, and photocatalytic activity were thoroughly investigated. Furthermore, the effects of catalyst dosage and antibiotic concentration on the degradation of TC were also discussed in detail. The result indicated that the ball milling method not only could enlarge the surface area of AgCl/WO3/g-C3N4 composites, offering a large number of reactive sites for the photocatalytic process, but also could increase the contact chance between the interfaces of WO3, AgCl and g-C3N4, resulting in effective charge separation and transfer. After optimizing the component ratio, the degradation efficiency of AgCl/WO3/g-C3N4 on TC and OTC reached 76.3 % and 59.8 % within 60 min. The capture experiments showed that superoxide radicals (•O2-) and photogenerated holes (h+) were the crucial active species during photocatalytic degradation and the dual Z-scheme transfer pathway of AgCl/WO3/g-C3N4 ternary composites was proposed.