Synergistic adsorption-photocatalysis of In₂S₃/Bi₂₄Fe₂O₃₉ based on oxygen vacancy for efficient tetracycline removal

Environmental issues have emerged as a pivotal challenge in the realm of industrial development, rendering the prioritization of renewable energy and sustainable development imperative. Photocatalytic materials should align with these goals by being recyclable and reusable. In this work, spherical nano-Bi₂₄Fe₂O₃₉ was synthesized via a sol-gel method combined with calcination and loaded onto In₂S₃ to construct an S-scheme In₂S₃/Bi₂₄Fe₂O₃₉ heterojunction with superior photocatalytic degradation performance. The composite exhibited an extended light absorption range from 585 nm to 650 nm (IB-30), a narrowed apparent bandgap compared to pure In₂S₃, and significantly improved carrier separation and transfer efficiency. Under the optimal conditions of pH = 7, catalyst dosage = 10 mg, and tetracycline (TC) concentration = 10 mg l^-1, the IB-30 material achieved a removal rate of 85.8% for tetracycline, which is 1.7 times and 2.46 times higher than that of pure In₂S₃ and pure Bi₂₄Fe₂O₃₉, respectively. Driven by the built-in electric field, photogenerated electrons follow an S-scheme pathway for transfer, while・O₂^-(superoxide anion radicals) and h⁺(holes) serve as the primary active species, effectively facilitating the photocatalytic degradation reaction. This study provides new insights into developing efficient and stable visible-light-driven photocatalysts.