In-situ synthesis of nitrogen-deficient g-C3N4-BiOBr-Bi2WO6/PVDF heterojunction composite membrane with enhanced retention and degradation performance

A nitrogen-deficient g-C 3 N 4 -BiOBr-Bi 2 WO 6 /PVDF composite ultrafiltration membrane with high-efficiency retention and degradation capabilities for various dyes and antibiotics was prepared using a simple in situ deposition combined with phase inversion method. Under normal pressure, the membrane achieved a retention rate of over 95 % for multiple dyes, featured numerous hydrophilic sites, and demonstrated an average pollutant flux of 147.6L·m −2 ·h −1 . In a simulated visible solar light flow-circulation device, the composite membrane exhibited excellent efficiency and final degradation performance, achieving a degradation rate of 97.7 % for RhB within 1 h and a final degradation rate of 99.6 %. DFT calculations provided evidence for the potential distribution and interaction forces between nanoparticles and PVDF molecules, supporting the observed results. The in situ synthesized BiOBr nanomaterials grow and embed within the membrane, forming heterojunctions with an internal electric field alongside other materials. The incorporation of heterojunction materials improves the surface and internal physical structure of the PVDF membrane, endowing it with excellent photocatalytic degradation performance, enhanced hydrophilicity, and improved retention capabilities. Additionally, the composite membrane exhibits outstanding self-cleaning properties. This work provides a broad-spectrum and efficient solution for water pollution treatment.