Environmentally-safe anion exchange membranes of PVA/PDDA/SiO₂composite for reverse electrodialysis

Anion Exchange Membranes (AEMs) are positively charged polymer membrane used in many applications. In RED systems, AEMs could be used to separate ions to produce energy, and on the other hands remove unwanted molecules in wastewater. This study used three masses of colloidal silica (SiO₂) as inorganic filler, three mass ratios of polymer mixture (where; PVA as an inert polymer and PDDA as an active polymer) and three different solvents (H₂O, DMSO, and DMF), to produce composite AEMs. The properties of fabricated membranes, were measured to be used in the RED systems. RED membranes produced by DMSO showed the best yields where area resistance (AR), swelling degree (SD), and fixed charged density (FCD) were 1.69 k.Ω.cm², 31.56%, and 0.26 mmol/g H₂O, respectively, at the mixed mass ratio φ(PDDA/PVA)/SiO₂ of AEM (0.528:0.4; DMSO). SiO₂ can create a layer that can strengthen the matrix membrane, formed through -C(=O)-O-C- and -Si-O-Si- bonds. SiO₂ can also encourage the formation of quaternary ammonium bonds. The higher the ratio of the mixture used can increase the number of quaternary ammonium bonds to improve AR and permselectivity. The use of water as solvent in the preparation of AEMs from PVA/PDDA/SiO₂ mixture is also promising, by produce equivalent ion exchange properties, yet environmentally-safe.