COMPETITIVE DIFFUSION OF HYDROCHLORIC-ACID AND SODIUM-CHLORIDE THROUGH AN ACID DIALYSIS MEMBRANE

Competition between HCl and NaCl in dialysis across the anion exchange membrane Neosepta AFN was studied by measuring the diffusion flux of each electrolyte from aqueous solutions containing the two electrolytes. The acid flux was in all cases higher than the salt flux. These results are analyzed on the basis of the Nernst-Planck equation and the Teorell-Meyer-Sievers (TMS) theory. Measurements of the amounts of acid and salt in the membrane at sorption equilibrium were performed by using radioactive tracers. The results of such measurements, in conjunction with the results for the membrane electrical resistance, enabled us to obtain calculated values of the flux. These values were in satisfactory agreement with the experimental values. The two factors forming the basis of the greater diffusion flux for the acid than for the salt are, on the one hand, the higher mobility in the membrane phase of protons with respect to the other cations and, on the other hand, the higher degree of sorption of the acid in the membrane.