Recovery of nickel and cobalt from nickel laterite leach solution using chelating resins and pre-reducing process

The aim of this work was to recover nickel and cobalt from a nickel laterite leach solution using chelating resins combined with a pre-reducing process. Sodium sulphite was used as a reducing agent to convert Fe(II) from Fe(III) and increase adsorption efficiency. Batch experiments were performed using synthetic solutions to study the effect of pH in recovering these metals using chelating resins Lewatit TP 207 and Lewatit TP 220. Column experiments were performed to simulate the fixed-bed column process in the following two steps: first, removing copper; and second, recovering nickel and cobalt. Two acids were tested as eluent, namely, sulphuric and hydrochloric acid 1M and 2M. Batch experiments showed that increasing the recovery of the metals accompanied an increase in pH. Copper recovery was maximal at pH 2.00, and the resin selectivity changed in pH above 2, decreasing copper adsorption. However, batch experiments showed that nickel and cobalt recovery was higher at pH 3.50, and resin adsorbed a high concentration of contaminants such as iron, zinc, and chromium. For this reason, nickel and cobalt recovery at pH 2.00 was better in column experiments, with less of the contamination in the metals being adsorbed by the resin and a high selectivity for nickel and cobalt. Hydrochloric acid 2M showed to be more efficient as eluent than sulphuric acid. A precipitation process using NaOH was used to remove contaminants present in the eluent solution, and Cyanex 272 was used to separate cobalt and nickel through the solvent extraction process.