Visible-light-driven removal of bisphenol A using a Bi12SiO20/Bi2O3 S-scheme heterojunction: Performance and charge-transfer mechanism.

Efficient removal of the emerging organic contaminant bisphenol A (BPA) remains an important challenge for sustainable water treatment. Herein, a series of BSO-Bi2O3 heterojunction composites were synthesized via a facile in situ precipitation strategy to enhance visible-light photocatalytic degradation of BPA. Structural characterizations confirmed intimate interfacial contact between two components, facilitating strong electronic coupling across the BSO-Bi2O3 interface. Among all as-prepared samples, the composite BSO-5%Bi2O3 exhibited the highest photocatalytic performance, achieving nearly 90% BPA removal within 80 min, significantly outperforming pristine Bi2O3 and Bi12SiO20. The enhanced photocatalytic performance was mainly attributed to extended visible-light absorption, accelerated charge separation, and efficient interfacial charge transfer. Trapping experiments and ESR analyses revealed that superoxide radicals (·O2-) and holes (h+) were the dominant reactive species involved in the degradation process. Electrochemical measurements combined with density-functional theory (DFT) calculations further revealed favorable interfacial charge redistribution and enhanced charge-transfer kinetics, supporting an S-scheme charge-transfer pathway that preserves charge carriers with strong redox capabilities. Moreover, the composite BSO-5%Bi2O3 maintained excellent recycling stability and structural integrity after repeated use. This work provides an effective strategy for constructing efficient bismuth-based S-scheme photocatalysts for the photocatalytic removal of emerging organic contaminants.