Diffusion dialysis for the treatment of H2SO4-CuSO4 solutions from electroplating plants: Ions membrane transport characterization and modelling

Diffusion dialysis (DD) is proposed to separate and recover mineral acids and transition metals from electroplating industry process waters promoting a circular approach of resources recovery. In this work, a DD module with two anionic membranes (Fumasep FAD and Neosepta AFN) are used for the separation of H2SO4 from Cu2+ containing solutions. The membrane performances with sole H2SO4 solutions (0.2–2 M) and sole CuSO4 solutions (0.8–1.1 M Cu2+) and with mixtures of H2SO4 (0.6 M) and CuSO4 (0.2–1.1 M Cu2+) as feed are studied. H2SO4 recovery efficiency decreases as the concentration of acid increases. For H2SO4 solutions, the water drag flux from the retentate to the diffusate prevails against the osmotic flux for all concentrations investigated. Conversely, the presence of CuSO4 in solution enhanced the osmotic flux and slightly negatively affected the acid recovery. The osmotic flux is higher for Fumasep FAD. A distributed parameter model consisting of a set of spatial differential equations for the DD channels and a dynamic section including time-dependent differential equations for batch operations is constructed and then validated using experimental results.