Preparation of vanadium slag-Fe_xO_y/Bi₂WO₆ photocatalysts and their application in dye wastewater treatment

The VS-Fe_xO_y/Bi₂WO₆ composite photocatalyst was successfully synthesized from vanadium slag (VS) as an iron source through a calcination-hydrothermal method. The catalyst performance was characterized by XRF, XRD, BET, FTIR, TEM, UV Vis DRS, XPS and other characterization techniques. The photocatalytic performance and degradation mechanism of the composite photocatalyst on Rhodamine B (RhB) were investigated under simulated visible light. The results show that, compared to pure Bi₂WO₆, the photocatalytic performance of VS-Fe_xO_y/Bi₂WO₆ is significantly enhanced. Under the optimal conditions (10 wt% VS-Fe_xO_y doping, pH=5.5, catalyst dosage of 0.4 g/L, and initial RhB concentration of 10 mg/L), the degradation rate of RhB reached a maximum of 97.88% after 3 hours of simulate visible light irradiation. The degradation process follow a pseudo-first-order kinetic model, with a reaction rate constant about 7.18 times greater than that of pure Bi₂WO₆. The chemical oxygen demand (COD) concentration in the treat effluent is 10.87 mg/L, which meets the Class I standard of the "Comprehensive Sewage Discharge Standards." Characterization analyses reveal that the main form of VS-Fe_xO_y is α-Fe₂O₃, which is tightly bound to Bi₂WO₆ in a rod-shaped structure, promoting the refinement of Bi₂WO₆ grains and improving its texture properties. The doping of VS-Fe_xO_y can significantly enhance the visible light absorption ability of Bi₂WO₆, broaden the visible light response range, promote the separation of photogenerated carriers, and thereby enhance photocatalytic efficiency. The main reason is the presence of Fe³⁺/Fe²⁺redox reactions on the catalyst surface. The degradation mechanism of RhB involve the H₂O₂-assisted photo-Fenton catalytic degradation by VS-Fe_xO_yBi₂WO₆. After five cycles, the removal efficiency remained at 92.5%, demonstrating the good photocatalytic performance of this catalyst. This study provides a theoretical foundation for the resource utilization of vanadium slag in the field of photocatalysis.