Reduced graphene oxide/polyaniline conductive anion exchange membranes in capacitive deionisation process

Ion exchange membranes used in the electrosorptive water purification process such as capacitive deionization (CDI) is required not only have high ion exchange capacity but also have good electrical conductivity to minimize the electrical resistance. One of the problems of available ion exchange membrane (IEM) is lack of high electrical conductivity. In this study, a series of novel more conductive anion exchange membranes were prepared by dry phase inversion method, where the reduced graphene oxide/polyaniline (RGO/PANI) was added in the polyvinydene fluoride (PVDF) polymer matrix. The prepared membranes possess both higher electrical conductivity and high ion exchange capacity (IEC). By adding RGO in the membrane solution, it allowed higher PANI loading (for up to 50% PANI) in the PVDF solution. It was found that the water content of the prepared membranes can be controlled by balancing the added RGO and hydrophilic material PANI in the polymer matrix, this strategy can avoid the water content becoming too high. The electrical conductivity of the samples added with RGO all showed significantly improvement; with the conductivity values were more than doubled against the one without RGO. More importantly, it was found that adding the RGO/PANI in the membranes formula has increased the salt removal efficiency and sorption capacity. It was found that sample LG 50, with low GO concentration, and 50% PANI/RGO composites in the membrane showed the best performance among all the membranes prepared.