Efficiency of Electrodialysis Purification of Electroplating Industry Solutions Containing Magnesium Sulfate and Iron(III) Chloride

Electrodialysis is one of the most popular methods of electrochemical purification using membranes, and the scope of its application is constantly expanding. The aim of the work is to study the kinetic characteristics of multicomponent solution electrodialysis purification of electroplating plants from Mn2+, Fe (common), $${\text{SO}}_{4}^{{2 - }}$$ and Cl– ions. To achieve this aim, a number of applied tasks are solved. Measures are taken for the preparation and conditioning of membranes and experimental studies are carried out on electrodialysis purification of several series of model solutions. These solutions contain MnSO4·5H2O and FeCl3 in various concentrations up to 0.4 kg/m3 and are similar to wastewater from a some segments of the electroplating industry. Analysis of the results obtained on changes in kinetic characteristics in the purification process depending on the time and initial concentration of the solutions is carried out. The separation process is carried out on a laboratory electrodialysis plant using a package of alternating MK-40L and MA-41P ion-exchange membranes manufactured by IP Shchekinoazot LLC, Russia. The plant consists of an electrodialysis cell and three independent circulation lines, each of which is designed for desalinated, concentrated, and near-electrode solutions. The solutions are purified with a current density of 20 A/m2. As a result of the work, it is found that a change in the initial concentration of substances in the multicomponent solutions under consideration has a different effect on the electrodialysis purification process, depending on the removal of a specific type of ions. For example, at initially low ion concentrations, high purification rates are observed, that reach values of 99.5%. However, as the concentration increases, for most of the studied solutions of the “M,” “ZH,” and “ZHM” series, a significant decrease in purification efficiency occurs when a certain threshold value of the initial concentration is reached. It is important to note that this threshold value can vary significantly depending on the type of ion.