Oily wastewater treatment via a visible-light-responsive slurry membrane photocatalytic reactor incorporating Bi2WO6-based photocatalysts

Abstract

This study focuses on the development and integration of Bi₂WO₆-based visible-light-responsive photocatalysts with a zirconia/alumina ultrafiltration membrane in a slurry photocatalytic ceramic membrane reactor (SPCMR) for oily wastewater treatment, highlighting the synergistic effect of combining photocatalysis with membrane separation. To this end, several visible-light-active photocatalysts, including NH₂-MIL-125(Ti)/Bi₂WO₆, WO₃/Bi₂WO₆, and Bi₂O₃/Bi₂WO₆, were synthesized via hydrothermal methods and characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and nitrogen adsorption–desorption analyses. The filtration performance of the system was evaluated under varying oil concentrations ranging from 1000 to 3000 ppm, at natural pH, with a photocatalyst dosage of 1 g/L over a 4-hour operational period. Removal efficiency was assessed based on total organic carbon (TOC) content. Results showed that membrane performance declined at higher concentrations (3000 ppm) due to surface fouling; however, this limitation was mitigated by incorporating the SPCMR system. TOC removal varied depending on parameters such as transmembrane pressure (TMP), flow rate, and light intensity. Among the tested photocatalysts, NH₂-MIL-125(Ti)/Bi₂WO₆ exhibited the highest efficiency, achieving up to 92% TOC removal. These findings highlight the potential of Bi₂WO₆-based composite photocatalysts in SPCMR systems as a promising approach for sustainable oily wastewater remediation.