Theoretical and Experimental Study of Neutralization Dialysis of Phenylalanine–Mineral Salt Equimolar Mixture of Different Concentrations

A non-steady state mathematical model of the separation of a solution of an amino acid (phenylalanine) and a mineral salt (NaCl) by the neutralization dialysis (ND) method in a circulating hydrodynamic mode has been proposed. The model takes into account the characteristics of the membranes (thickness, ion-exchange capacity, electrical conductivity) and the solution (concentration and nature of the components) and the flow rate of the solution in the dialyzer compartments. The new model, unlike the known models, takes into account the transport of phenylalanine cations and anions across membranes and diffusion layers of the ND system. In addition, the model takes into account the ability of an amino acid to undergo protonation/deprotonation reactions. Comparison of the simulation results with experimental data suggests that the model adequately describes the ND of solutions of a phenylalanine–NaCl mixture. It has been shown that, for a given pair of membranes (CSE cation-exchange membrane and ASE anion-exchange membrane, Astom, Japan) and studied concentrations, the pH of the mixed solution remains relatively low throughout the entire process, and the rate of decrease in the electrical conductivity is lower than that for an individual NaCl solution. The loss of phenylalanine in the ND process has been determined according to analysis of the experimental data and simulation results.