Dialysis of aqueous solutions of nitric acid and ferric nitrate

The separation of an HNO3 + Fe(NO3)3 mixture using an anion-exchange membrane Neosepta-AFN has been investigated in a two-compartment dialysis cell with stirrers. The experiments have proved that this membrane is a very good separator for this mixture, because nitric acid permeates well through the membrane and ferric nitrate is efficiently rejected. The separation is very efficient at high acid concentrations or low content of the salt in the mixture to be dialyzed.

Research highlights▶ The separation of an HNO3 + Fe(NO3)3 mixture using an anion-exchange membrane Neosepta-AFN has been investigated in a two-compartment dialysis cell. ▶ The membrane is a very good separator for this mixture, because nitric acid permeates well through the membrane and ferric nitrate is efficiently rejected. ▶ The dialysis process can be quantified by four phenomenological coefficients, which are dependent upon the initial acid and salt concentrations in the compartment initially filled with the HNO3 + Fe(NO3)3 solution. ▶ The phenomenological coefficients can easily be determined by the numerical integration of the basic differential equations, which describe the time dependence of the concentrations of both the components in the compartment initially filled with distilled water, followed by an optimizing procedure.