Application of BiVO4/TiO2/CNT Composite Photocatalysts for Membrane Fouling Control and Photocatalytic Membrane Regeneration during Dairy Wastewater Treatment

Abstract

This study aimed to investigate the performance of composite photocatalytic membranes fabricated by incorporating multiple nanoparticles (TiO2, carbon nanotubes, BiVO4) into polyvinylidene fluoride membrane material for real dairy wastewater treatment. The composite photocatalytic membranes exhibited superior antifouling behavior, lower filtration resistance, better flux, and higher flux recovery ratio than the pristine membrane. Salinity, pH, and lactose concentration are determinant factors that affect filtration resistance and rejection performance during the ultrafiltration of dairy wastewater. Generally, higher irreversible and total resistances and slightly lower chemical oxygen demand (COD) rejections were found at higher salinity (expressed by electric conductivity values of >4 mS/cm) than lower salinity (<4 mS/cm) levels. The presence of lactose in dairy wastewater increased irreversible resistance and severely reduced COD rejection during ultrafiltration due to the ability of lactose to pass through the membranes. It was ascertained that membranes require further treatment after filtrating such wastewater. Lower resistances and slightly better COD rejections were observed at pH 7.5 and pH 9.5 compared to those observed at pH 4. Photocatalytic membranes fouled during the ultrafiltration of real dairy wastewater were regenerated by visible light irradiation. The membrane containing all constituents (i.e., TiO2, carbon nanotubes, and BiVO4) showed the best regeneration performance, exceeding that of the pristine membrane by 30%.

Wastewater Treatment in the Dairy Industry from Classical Treatment to Promising Technologies: An Overview

“…Fouling remains a significant obstacle in membrane processes [83]. It generally arises through two main routes: foulant adhesion/deposition and the foulant layer filtering process [59].…”

PAN/TiO2 Ultrafiltration Membrane for Enhanced BSA Removal and Antifouling Performance

“…Thus, filtration membranes combined with photocatalytic oxidation technology can be an efficient method to alleviate the membrane fouling issues [20,21]. Specifically, an electron of the semiconductor photocatalyst inside the membrane can be excited from the valence band (VB) to the conduction band (CB) facilitated with visible or UV light [22,23]. Thus, a positive charge and electron-hole pair are formed in the VB band during the process, which can generate the hydroxyl radicals (•OH) and eventuate the degradation of contaminants on the membrane surface [24,25].…”