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Physicochemical interactions of organic acids influencing microstructure and permselectivity of anion exchange membrane
- Chandra, Anusha, E, Bhuvanesh, Chattopadhyay, Sujay
- Colloids and surfaces 2019 v.560 pp. 260-269
- adsorption, anion-exchange membranes, anions, citric acid, colloids, diffusivity, formic acid, malic acid, microstructure, moieties, pH, propionic acid, water uptake
- Permselectivity and water uptake behaviors of anion exchange membrane (AEM) were investigated with organic acids. Contribution of the number of carboxyl group (acetic acid: AA, malic acid: MA, citric acid: CA) and hydrocarbon chain lengths (formic acid: FA, AA, propionic acid: PA and n-butyric acid: BA) in water uptake and permselectivity values were separately investigated with five different concentrations 0.025, 0.05, 0.075, 0.1 and 0.125 mol·L−1 of each acid at two different pH 2.0 and 7.5 conditions. Microstructural changes occurring due to interaction of carboxylate anion and NR4+ groups of AEM resulted in permselectivity behavior. Permselectivity trend: CA < MA < AA could be explained by counter-ion condensation resulting out of strong counter-ion interactions with AEM fixed charges. Co-ion mobility values could explain variation in permselectivity at pH 2.0 and 7.5. While, water uptake and ionic size were dominant factors to explain the permselectivity trend: FA > AA > PA > BA. Complex nature of interactions due to properties (size, charge, ionic charge density, mobility, diffusivity, stokes radius etc.) of carboxylate anions were explained using diffusivity ratio (counter/co-ion, D2/D1), adsorption equilibrium and fraction of dissociated species.