The competitive transport of sulphuric acid and magnesium sulphate through an anion-exchange membrane Neosepta-AFN (Astom Corporation, Japan) is investigated in a two-compartment counter-current dialyzer with single passes at steady state. The dialysis process is characterized by the recovery yield of acid and the rejection coefficient of salt. The experiments prove that the recovery yield of acid is in the limits from 61% to 87%, while the rejection coefficient of magnesium sulphate is in the limits from 87% to 97%. Moreover, the simultaneous transport of acid and salt is satisfactorily quantified by four phenomenological coefficients, which are functions of acid and salt concentrations in the feed. For this purpose, two ordinary differential equations describing the steady-state concentration profiles of both the components in both the compartments of the dialyzer are numerically solved in the combination with an optimizing procedure. The mathematical model used considers the mass trasfer resistances in liquid films on both the sides of the membrane. (c) 2010 Elsevier B.V. All rights reserved.