Preparation and Performance of a Novel Photocatalytic Antibacterial Ag-Ag₂C₂O₄-TiO₂/PAMPS/PVDF-Based Membrane in an Immobilized Photocatalytic Membrane Reactor under Visible-Light Irradiation

Combining membrane separation with the photocatalysis process, which is named photocatalytic membrane reactor (PMR) technology, has received great consideration for the process of dyeing wastewater coupled with irradiation of visible light to reduce membrane fouling and improve rejection performance. In this paper, the photocatalytic membranes were modified using two different methods: (i) the deposition of Ag-Ag₂C₂O₄/TiO₂ photocatalysts on the membrane surface by the electrospray technology and (ii) the blending of Ag-Ag₂C₂O₄/TiO₂ photocatalyst into the membrane matrix. In addition, a novel amphiphilic copolymer [PVDF-g-2-acrylamido-2-methylpropane sulfonic acid (PVDF-g-PAMPS)] was also synthesized and utilized as a hydrophilic additive into the PVDF matrix to improve the hydrophobic membrane. The amphiphilic copolymer (PVDF-g-PAMPS) negatively charged could play a significant role in the degradation of organic pollutants. The performance of photocatalytic membranes with additives (NPs and copolymer) was evaluated and compared with the photocatalytic membranes without additives, during the cross-flow PMR process. The SEM/EDX images, porosity, and contact angle analysis were investigated to confirm the properties of photocatalytic membranes, such as hydrophilicity, permeability, and antifouling, and rejection performances were improved. Also, the surface plasmon resonance of Ag metals on Ag-Ag₂C₂O₄/TiO₂ heterojunction photocatalyst demonstrated significant light absorption and a low rate of electron-hole recombination under light irradiation, according to UV-visible differential reflectance spectra, photoluminescence spectra, and electrochemical impedance spectroscopy analyses. With an increase of Ag-Ag₂C₂O₄/TiO₂ NPs into copolymerized membranes (PVDF-g-PAMPS/PVDF), the flux decline was improved from 37 to 16%, and rejection was increased (about 96%) due to hydrophilicity of fabricated membranes. However, the electrospray-coated Ag-Ag₂C₂O₄/TiO₂ on the membrane surface showed the highest dye rejection (about 99%) in the optimum condition. The results demonstrated that the Ag-Ag₂C₂O₄/TiO₂/PAMPS/PVDF mixed matrix membrane with suitable photocatalytic activity and negatively charged surface could effectively reduce the fouling of membranes and improve rejection performance. This membrane is highly promising for water treatment due to the properties of antibacterial activity by blending of the Ag-Ag₂C₂O₄/TiO₂ NPs.