Selective recovery and separation of nickel and vanadium in sulfate media using mixtures of D2EHPA and Cyanex 272

In this research, selective recovery and separation of nickel and vanadium in sulfate media was investigated by solvent extraction using D2EHPA, Cyanex 272, and their mixtures in various proportions. For this purpose, synthetic sulfate solutions of nickel and vanadium were prepared in 2 g/L of each metal. After dilution of the organic solvents in kerosene with the ratio of 1-4, experiments were carried out in the pH range of 1.0-7.0 in steps of 0.5 at ambient temperature. Solvent extraction of nickel and vanadium by sole D2EHPA was performed and the extraction percentages were determined to be 90% and 80% for nickel and vanadium, respectively. However, the co-extraction of nickel and vanadium by D2EHPA can be increased with increasing equilibrium pH and temperature. It was shown that using sole D2EHPA, pH(50) (the pH at 50% metal extraction) values for nickel and vanadium were 3.5 and 2, respectively; which is not appropriate for the efficient simultaneous separation of nickel and vanadium. Adding Cyanex 272 to D2EHPA in the organic phase, leads to a right shifting of extraction isotherm of nickel and a slight left shifting of the extraction isotherm of vanadium; thus, improves the separation of nickel over vanadium. To optimize the recovery and separation process of nickel and vanadium from the sulfate leach liquor, the influence of different D2EHPA to Cyanex 272 ratios and various temperatures (25, 35, 45, and 55 degrees C) were studied. As a result, optimum separation of vanadium over nickel was achieved with a Cyanex 272 to D2EHPA ratio of 0.35 M: 0.25 M. Based on the optimum results, pH(50) values for nickel and vanadium were shifted from 3.5 to 4.75 and from 2 to 1.75, respectively. (C) 2014 Elsevier B.V. All rights reserved.