Development of a Bi2WO6/BiVO4/ZnO (BBZ) dual S-scheme heterojunction composite enabling synergistic charge transfer mechanism for efficient photocatalytic removal of dimethyl phthalate

This study proposes the development of a dual S-scheme heterojunction Bi 2 WO 6 /BiVO 4 /ZnO (BBZ) composite for efficient photocatalytic degradation of the emerging pollutant, dimethyl phthalate (DMP), which may alter endocrine function and endanger both human health and ecosystems. The proposed ternary composite integrates the visible-light-responsive compounds Bi 2 WO 6 and BiVO 4 with ZnO, a material with a wide bandgap that exhibits high electron mobility, to form a dual S-scheme heterojunction. This configuration facilitates rapid charge separation and transport and minimizes electron-hole (e - & h + ) recombination, thereby enhancing photocatalytic activity under visible light. The BBZ-20 composite was prepared via a hydrothermal technique followed by thermal treatment, resulting in an evenly dispersed, stable material with an optimal molar ratio of 0.40:0.40:0.20 (Bi 2 WO 6 /BiVO 4 /ZnO). The structural and physicochemical characteristics were comprehensively analyzed, confirming the development of a ternary heterostructure composite having a surface area of 68.745 m 2 /g and broadened light-harvesting up to 667 nm, compared to Bi 2 WO 6 (415 nm), BiVO 4 (530 nm), and ZnO (392 nm). Photocatalytic degradation experiments demonstrated that the BBZ-20 composite surpassed both individual and binary composites, with a 92% removal of DMP and reaction rate constants ( k ) 2.92 and 6.63 times higher than Bi 2 WO 6 /BiVO 4 and ZnO, respectively. Kinetic studies showed adherence to a pseudo-first-order model, while recyclability assessments validated the exceptional stability and recyclability of the material over four cycles. This study introduces an economical, environmentally benign, and scalable photocatalyst that offers a viable option for the treatment of dimethyl phthalate-contaminated wastewater.