Influence of Fruit and Vegetable Juices on Transport Properties of Heterogeneous Membranes

Abstract

This work investigates the influence of natural juices on the specific conductivity and current–voltage curves of monopolar heterogeneous membranes of domestic (MK-40, MA-41) and foreign (Ralex CMHPES, Ralex AMHPES) production. It was found that storage in juices leads to a decrease in the conductivity of anion-exchange membranes by up to 80% due to their conversion from the chloride form to the form of large organic ions and fouling by organic juice components. At the same time, the conductivity of cation-exchange membranes in tomato and apple juices changes less significantly. Based on the study of the current–voltage curves of membranes before and after their immersion in juices, it is shown that an increase in the length of the limiting current plateau is observed, caused by the sorption of organic components of various natures by the membranes, which is more pronounced for anion-exchange membranes. For the MK-40 membrane, this effect is absent. A method for membrane regeneration after contact with juices is proposed, which allows restoring the specific conductivity of the samples to their initial values. The process of reagentless pH correction of apple juice by bipolar electrodialysis was investigated, where the current efficiency was 0.78–0.86, and the energy consumption for neutralizing 1 mol of molecular malic acid was 0.85 kW h.