Competing Transport of Citric and Acetic Acids through Commercial and Modified Ralex AMH Anion-Exchange Membrane

This work investigates the competitive transport of acetic and citric acids from model solutions containing both salt and molecular forms of the acids. The study examines two membrane systems: a Ralex AMH heterogeneous membrane with a total concentration of 0.1 mol-eq/L of each acid and a Ralex AMH/MF-4SK bilayer membrane with a total concentration of 0.5 mol-eq/L of each acid. Experiments were conducted at solution pH values of 1.0, 4.8, and 9.0. The separation of organic acids by electromembrane processes is a key challenge when these acids are obtained from mixtures. The results show that electrodialysis extraction of citric acid from solution containing 0.1 mol-eq/L of organic acid ions and molecules, using Ralex AMH membrane at current density of about 3 A/dm2 and pH 9.0, yields a specific selective permeability coefficient PCit/Ac equal to 4 for citric acid compared to acetic acid. Electrodialysis removal of acetic acid from solution containing 0.5 mol-eq/L of organic acid ions and molecules using the Ralex AMH/MF-4SK membrane at current density of 0.17 A/dm2 and pH 9.0 results in PCit/Ac value of 0.025.