Fabrication of g-C3N4 nanosheets immobilized Bi2S3/Ag2WO4 nanorods for photocatalytic disinfection of Staphylococcus aureus cells in wastewater: Dual S-scheme charge separation pathway

In this work, graphitic carbon nitride (g-C3N4) immobilized Bi2S3/Ag2WO4 (BS/AW/CN) heterojunction was successfully fabricated using a facile multi-step approach. The fabricated nanomaterials were characterized using different sophisticated technologies. The morphological investigations revealed the existence of g-C3N4 nano -sheets loaded with Ag2WO4 and Bi2S3 in a nanorod-like structure. The BS/AW/CN nanocomposite exhibited improved surface area, which was attributed to the regular deposition of Bi2S3/Ag2WO4 on the surface of g-C3N4 nanosheets. The obtained BS/AW/CN heterojunction displayed excellent light absorption ability with promoted photoelectrochemical properties, which was attributed to the lower band gap energy of Bi2S3 species. The BS/ AW/CN (0.25 g/L) showed superior photocatalytic antimicrobial activity against Staphylococcus aureus cells (similar to 1 x 107 CFU/mL) under 140 W of visible-light illumination, where complete inactivation activity was observed in 90 min. The disinfection kinetics verified the faster photoreaction process over BS/AW/CN compared with single and binary catalysts. The inactivated bacterial cells were further elucidated by fluorescence spectroscopy and electron microscopy techniques. The photocatalytic disinfection activity was also investigated under different operating conditions like pH, catalyst loading, and bacterial density. The stability studies verified the high photostability of the obtained heterojunction in five photoreaction runs, suggesting its potential applicability in wastewater disinfection systems. The electronic characteristics and radical trapping results were considered in justifying the dual-S-scheme heterojunction mechanism in the presence of BS/AW/CN. In conclusion, this work demonstrates the feasibility of an efficient visible-light responsive photocatalyst for Staphylococcus aureus cells disinfection in wastewater treatment systems.