The separation and recovery of copper(II), nickel(II), cobalt(II), zinc(II), and cadmium(II) in a sulfate-based solution using a mixture of Versatic 10 acid and Mextral 984H

We studied the separation and recovery of copper(II), nickel(II), cobalt(II), zinc(II), and cadmium(II) from magnesium and calcium, using synergistic solvent extraction (SSX) in a typical hydrometallurgical waste solution. A mixture of Versatic 10 acid and Mextral 984H, diluted with Mextral DT100, was used to obtain fundamental data on pH and distribution isotherms, as well as the kinetics of extraction and stripping. We also investigated the main effects and interactions of common solvent extraction factors: the extraction pH at equilibrium, the temperature, and the extractant concentration. The synergistic effect for extracting metals was confirmed. The results showed that the addition of Mextral 984H enhanced the separation factors of copper, nickel, cobalt, zinc, and cadmium over magnesium and calcium. Compared with Versatic 10 acid alone, for a mixture of 0.5 mol·L− 1 Versatic 10 acid/0.5 mol·L− 1 Mextral 984H, ΔpH50 values of copper, nickel, cobalt, zinc, and cadmium were found to be > 2.0, 3.30, 2.85, 0.95, and 1.32 pH units, respectively. The ΔpH50(Zn-Mg) and ΔpH50(Zn-Ca) values were 3.27 and 2.25, respectively, indicating easy separation and recovery of copper, nickel, zinc, cobalt, and cadmium. The extraction and stripping of copper, cobalt, zinc, and cadmium were fast, with 90% of the metal transferred in 2 min. We next studied whether the metals could be stripped from the extracted liquid selectively in sequence, by using sulfuric acid at different concentrations. The influence of the molecular structure of the oxime and carboxylic acid components upon the synergistic effects was identified by numerical analysis. Excellent separation of copper, nickel, cobalt, and zinc over magnesium and calcium was achieved with this synergistic solvent extraction system.