Electrokinetic characteristics of electrodeionization purification and concentration of electroplating solutions containing cobalt, copper, and cadmium ions

In this work, we investigate the electrochemical and electrokinetic characteristics of electrodeionization extraction of cobalt, copper, and cadmium ions from process solutions of electroplating plants for subsequent recycling. The research objects were selected following a review of publications on the possibility of using electromembrane methods for purification and concentration of industrial wastes. The current–voltage characteristics of the electrodeionization process were studied experimentally. The I–V curves showed the presence of a minimal linear ohmic section at voltages from 1 to 3 V and a plateau with a slight upward slope at the section from 3 to 5 V. Under a further increase in voltage, a region of supercritical current is observed, which is related to the formation of H + and OH - ions at the membrane–ion-exchange resin interfaces. The kinetic dependencies of the concentrations of retained substances on the residence time in the desalting and concentration chambers of the electrodeionization unit at different current densities and flow rates were analyzed. At a low current density of 5 A/m 2 , three main sections were observed: (1) in the range from 0 to 900 s, where ion accumulation on ion-exchange membranes in desalting and concentration chambers occurs; (2) in the range from 900 to 2700 s, where intensive ion transfer is observed; (3) in the range from 2700 to 3600 s, where electrochemical regeneration of ions in purification chambers takes place. The results obtained were used to develop a technological scheme for wastewater treatment from heavy metal ions.