Composite Membrane of Bi₂WO₆-NCQDs Laminated Hetero-junction Loaded on PES Support for Photo-catalytic Degradation of Organic Pollutants

Photo-catalysis is an effective way to remove organic pollutants in aqueous system since it can accelerate water splitting under solar energy to produce ∙O2-, which oxidizes toxic and harmful organic substances. Here, nitrogen-contained carbon quantum dots (NCQDs) were prepared by microwave-promoted co-carbonation of glucose and poly(hexamethylene guanidine) (PHMG) and loaded on the surface of poly(ether sulfone) (PES) micro-porous membrane through cross-flow filtration. Spherical Bi2WO6 particles were subsequently coated on NCQDs layer by vacuum filtration to fabricate a three-layer composite membrane (TLCM). Close contact between NCQD and Bi2WO6 layers in TLCM formed laminated hetero-junction structure, which decreased the band gap to 2.35 eV from 2.90 eV of Bi2WO6. TLCM showed 99.9% photo-catalytic degradation efficiency (DE) for azo-dye Congo red (CR) under 50 W white light LED for 2.3 h with reaction rate constant of 0.02317 min-1. Possible decomposition products of CR were naphthylamine, benzidine and aniline analyzed by GC-MS. TLCM also displayed 72.23% DE for tetracycline (TC).