Polarization electric field tuning interface electric field in full-spectral response double S-scheme heterojunction to drive synchronous removal of Cr(VI) and RBR X-3B

Photocatalytic technology provides a sustainable development strategy for the synchronous removal of azo dyes and mordant leaching of Cr(VI). To mitigate the shielding effect of free carriers on the built-in electric field during the photocatalytic process, a double S-scheme piezo-photocatalyst Bi₂WO₆/BiOCl/Bi₂S₃ (BW-C-S) with full spectral response that can continuously respond to the ultrasound-guided polarized electric field to adjust the built-in electric field to promote the separation and migration of photogenerated carriers was developed. BW-C-S effectively overcame the barriers of carrier separation and migration by utilizing an ultrasonic-optical coupling field, achieving the rapid synchronous removal of reactive brilliant red X-3B (RBR X-3B) (0.057 min^-1) and Cr(VI) (0.063 min^-1). The synergistic reaction mechanism, potential degradation pathways, and the ecological toxicity of intermediates associated with the RBR X-3B/Cr(VI) synchronous removal process and the RBR X-3B independent degradation process were further elucidated through LC-MS analysis, DFT calculations, and toxicity evaluations. The continuous removal efficiency of pollutants by BW-C-S under dynamic hydraulic conditions was validated through the construction of a continuous flow reaction device, which provided theoretical support for the sustainable purification of various pollutants in complex aquatic environments.