Separation of an aqueous solution of HCl þ NiCl 2 by diffusion dialysis was investigated in a two-compartment mixed cell with an anion-exchange membrane Neosepta-AFN. The experiments proved that this membrane can be considered a good separator for the mixture mentioned, because nickel chloride is efficiently rejected, while hydrochloric acid permeates well through the membrane. The separation is very effective at high acid concentrations and low concentrations of nickel chloride. The separation efficiency of the membrane was evaluated by the partial flux of nickel chloride. The experiments revealed that the partial flux is very low, i.e. below 3.2%-it decreases with increasing acid concentration, but it increases with increasing content of salt in the solution separated. Moreover, the separation process was quantified by the permeability of the membrane based on four phenomenological coefficients which depend on the initial acid and salt concentrations.
ABSTRACT:Competitive transport of hydrochloric acid and zinc chloride has been investigated in a two-compartment mixed cell with an anion-exchange membrane Neosepta-AFN developed and produced by Tokuyama Soda Co. These experiments have proved that hydrochloric acid permeates well through the membrane used but, on the other hand, zinc chloride is not effectively rejected. The flux of zinc chloride has been found to be increasing with increasing acid and salt concentrations. Furthermore, it has been found that it is approximately one order of magnitude higher than that found in the case of simultaneous transport of sulfuric acid and zinc sulfate through the same membrane. The further calculations concerning the ionic equilibria with sorption isotherms for the HCl-ZnCl 2 system, which have been measured experimentally, have revealed that high flux of ZnCl 2 is due to the fact that a considerable amount of zinc chloride in the membrane is in the form of ZnCl 3 Ϫ complex, which is relatively small and passes well through this membrane.
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