Electrokinetic characteristics of electrodialysis purification of zinc-containing solutions from zinc, iron, and sodium ions

In this paper, we present an experimental setup and investigate the process of electrodialysis separation using model solutions simulating spent industrial electrolytes containing Zn²⁺, Fe³⁺, and Na⁺ ions. To justify the selection of the study objects, we carry out a literature review of publications on the feasibility of using electromembrane methods for the purification and concentration of industrial wastewater. The study of current–voltage characteristics revealed two distinct regions of the curve and found that solutions with greater concentrations of metal cations exhibit a higher level of current over almost the entire range. Based on the investigation of purification degree of the initial solution from cations, the dynamics of Zn²⁺ ion removal were analyzed. It was found that an increase in the current density to 20 A/m² enhances ion migration rates and thereby improves the degree of electrodialysis purification. This is evidenced by the presented kinetic curves, where the profiles corresponding to different initial concentrations diverge more significantly. It is concluded that the use of MA-41 and MK-40 ion-exchange membranes in electrodialysis separation is effective for solutions containing zinc, iron, and sodium compounds. In a number of cases, these membranes enable satisfactory separation into dialysate and concentrate. A methodology for the process design calculation of electrodialysis units is proposed, allowing determination of the limiting current density, current efficiency, the area of concentration and desalination compartments, as well as the required number of sections in the setup.