Membrane-assisted capacitive deionization: Effect of Poly(vinyl alcohol) cross-linking on the properties of ion exchange membranes

Novel composite electrodes were developed for application in membrane capacitive deionization (MCDI). Activated carbon (AC) was dispersed in a solution of poly(vinyl alcohol) (PVA) mixed with polyacrylic acid (PAA) or poly dimethyl diallyl ammonium chloride (PDMDAAC), and cast onto the surface of an AC-based modified graphite electrode, prepared by phase inversion, to form a composite membrane further cross-linked with glutaraldehyde (GA). The effect of the cross-linking on the chemical structure of the PVA-based membranes was determined by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Cyclic voltammetry was conducted to examine the specific capacitance of the composite electrodes. Desalination experiments were then performed with MCDI unit cells to study the effect of cross-linking on the desalination efficiency. It was proved that after optimization, the synthesized composite electrodes exhibited one and a half times higher NaCl removal capacity and three times higher adsorption rate as compared to that of a conventional CDI cell using commercial ion exchange membranes (IEMs) with almost the same energy consumption. The enhanced desalination performance was attributed to the optimized properties of the selected polymers and the improved adhesion of IEMs to the electrodes. This research paves the way for the application of new materials in MCDI processes for improved water desalination. Desalination experiments in a continuous recirculating flow-by system. image