Separation of Co and Ni from a chloride leach solutions of laterite ore by solvent extraction with extractant mixtures

Leaching Kinetics and Mechanism of Laterite with NH4Cl-HCl Solution

Following the growing demand for Ni and Co and the dwindling supplies of sulfide nickel ore, attention has turned toward the more efficient exploitation and utilization of laterite ore. Using ammonium chloride acid solution to leach is an effective method. Our research concerned investigations on the leaching mechanism and leaching kinetics of laterite. XRD was used to demonstrate the leaching mechanism through analysis of the pattern of the leaching residue and raw ore, showing that acid concentration affects the leaching process more significantly than other factors, and that valuable metals are mainly released from goethite and serpentine. The leaching order of these materials are as follows: Goethite > serpentine > magnetite and hematite. The leaching kinetics were analyzed and this leaching process followed a shrinking core model controlled by a combination of interfacial transfer and diffusion across the solid film. Leaching data fitted to the kinetic equation perfectly, and the apparent activation energies for the leaching of nickel, cobalt, and iron were calculated to be 4.01 kJ/mol, 3.43 kJ/mol, and 1.87 kJ/mol, respectively. The Arrhenius constants for Ni, Co, and Fe were 204.38, 16.65, and 7.12 × 10−3, respectively, with reaction orders of Ni (a 1.32, b 0.85, c 1.53), Co (a 1.74, b 1.12, c 1.22), and Fe (a 2.52, b −0.11, c 0.94).

Cobalt Extraction from Sulfate/Chloride Media with Trioctyl(alkyl)phosphonium Chloride Ionic Liquids

The application of phosphonium-based ionic liquids (ILs) on the selective extraction of cobalt is presented. The extraction mechanism is established, and different parameters of the process are evaluated. It has been found that it is possible to extract cobalt from aqueous solutions in sulfate media, with the addition of sodium chloride, using phosphonium ILs. The cobalt extraction was selective with respect to nickel and strongly dependent on the chloride concentration in the aqueous solution. The cobalt extraction is given by an anion exchange mechanism through an endothermic process. Cobalt extractions greater than 98% were obtained using the proposed methods. Cobalt stripping from the loaded IL phase using water was proved. Therefore, an alternative extraction process to traditional organic solvents is proposed. This alternative has additional advantages such as easy handling, lower costs in reagents and equipment, and risk reduction.