Composite Anion Exchange Membranes with Antibacterial Properties for Desalination and Fluoride Ion Removal

Abstract

The contamination of fluoride ions in groundwater and membrane fouling due to the growth of bacteria in wastewater are serious problems. We report the preparation of a composite anion exchange membrane (AEM) with enhanced antimicrobial properties for water desalination and fluoride ions removal from water by electrodialysis (ED). The composite membranes were prepared by impregnating silver nanoparticles (AgNPs) in the N-alkylated terpolymer of poly(acrylonitrile), poly(n-butyl acrylate), and poly[(2-dimethyl aminoethyl) methacrylate], followed by cross-linking by the reaction with hydrazine hydrate. The key factors are the variation of alkyl chain length attached with −N(CH3)2− in the membrane matrix, optimizing the water uptake and impregnation of AgNPs. The presence of AgNPs in the AEMs was confirmed by UV−visible spectroscopy, transmission electron microscopy, and EDAX mapping. The incorporation of 0.03 wt % AgNPs in the AEMs increases 8.5−12.5% water uptake and 8−12% ionic conductivity. The representative M-C10/AgNPs membrane exhibited 0.72−0.74 kWh/kg power consumption and 96−95% current efficiency during the removal of fluoride ions (5.5−11 mg/L) from water containing NaCl (concentration: 2000 mg/L) by ED process. No detectable leaching of AgNPs was observed by continuous exposure of the composite AEMs in water at 50 °C for 15 days.