Effect of Impurities in the Recovery of Critical Metals: The Case of Nickel Laterite in the Solvent Extraction Process

The search for new sources of critical metals faces a content decrease in mineral resources. Consequently, high impurities are present in the solution obtained in hydrometallurgical processing, which must be removed. For cobalt, it is crucial for Li-ion battery production, and iron is the main contaminant. However, there is a lack of literature about the co-extraction of target metals in impurities removal. The present work's goal was to study the co-extraction of cobalt from nickel limonite leach solution by solvent extraction. Experiments were carried out with Cyanex 272 in kerosene, and the effect of pH, temperature, and iron concentration were evaluated. Results showed that the extraction of iron and co-extraction of cobalt increased as the pH and temperature increased, achieving 85.1% and 37%, respectively, at 60 °C and pH 1.75. Cobalt extraction in solution without iron reached less than 8%. In bi-elementary solutions, co-extraction of cobalt was similar to the real solution when the Fe/Co concentration ratio was 225 and declined as the Fe/Co ratio decreased. The present study demonstrated that the presence of iron in different concentrations contributes to the co-extraction of cobalt. Graphical Abstract