Comparative Study of Different Ion-exchange Membrane Types in Diffusion Dialysis for the Separation of Sulfuric Acid and Nickel Sulfate

The application of diffusion dialysis using various types of ion-exchange membranes for the separation of sulfuric acid and nickel sulfate has been evaluated. The process of dialysis separation of a real waste solution from an electroplating facility containing 252.3 g/L of sulfuric acid, 20.9 g/L of nickel ions and small amounts of zinc, iron, copper ions, etc. has been studied. Heterogeneous cation-exchange membrane containing sulfo groups and heterogeneous anion-exchange membranes with different thicknesses (from 145 μm to 550 μm) and types of fixed groups (4 samples with quaternary amino groups and 1 sample with secondary and tertiary amino groups) are used. The diffusion fluxes of sulfuric acid, nickel sulfate, and the total and osmotic fluxes of the solvent are determined. The use of a cation-exchange membrane does not allow separation of the components, since the fluxes of both components are low and comparable in magnitude. The use of anion-exchange membranes makes it possible to efficiently separate sulfuric acid and nickel sulfate. At the same time, the thin dialysis membrane turns out to be the most effective, as well as the membranes with quaternary amino groups, and the membrane with secondary and tertiary amino groups proved to be the least effective.