Highly Cross-Linked butene grafted poly (Vinyl Alcohol)–co-Vinyl pyridine based anion exchange membrane for improved acid recovery and desalination efficiency

Abstract

Water treatment and waste acid reclamation are important in present situation due to huge industrialization. Different processes are available for the water treatment and waste treatment. Ion exchange membranes based electrodialysis (ED) and diffusion dialysis (DD) are attracted by the researchers since last decade due to its simplicity and economical operation. Acid reclamation by diffusion dialysis has been gained huge attention due to their absolute selectivity and energy less process. Here, we report the synthesis of efficient anion exchange membrane (AEM) by free radical co-polymerization of butene grafted poly (vinyl alcohol) and 4-vinyl pyridine followed by in-situ quaternization and cross-linking. Different amount 4-vinyl pyridine was chosen for the membrane preparation, and its impact on physiochemical and electrochemical properties has been studied. Structural and chemical characterisation of the membranes were studied using nuclear magnetic resonance (NMR), attenuated total reflectance-infrared spectroscopy (ATR-IR), while surface-phase morphology was investigated through scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermo-mechanical properties of prepared membranes were studied using thermogravimetric analysis (TGA), differential scanning colorimetry (DSC), dynamic mechanical analysis (DMA) and universal testing machine (UTM) analysis. The cross-linked PVA-x membranes showed high acidic stability as well as good antioxidation property. The synthesized membranes were studied for their salt removal performance by electrodialysis and acid recovery by diffusion dialysis. The optimised membrane (PVA-0.8) shows 0.90 kWh kg−1 energy consumption and 93.49 % current efficiency during salt removal from brackish water using electrodialysis. All cross-linked PVA-x membranes have diffusion coefficient of acid are in the range of 0.0556–0.0716 mh−1 and separation factor values are between the 79.51 to 91.33 at 25 °C, which comparable to commercial DF-120B membrane. This result shows that the prepared cross-linked AEMs may be a good candidate for the electrochemical applications.