The effect of calcination as pre treatment to enhance the nickel extraction from low-grade laterites

The effect of a thermal pre treatment on the leaching behavior of a low-grade nickeliferous laterite ore, obtained from the north of Colombia, was investigated. The lateritic ore was first calcined at different temperatures, and then leached for 48 h in 3.2 M hydrochloric acid. An increase in nickel extraction from 15.8% to 57.1%, 98.0%, 91.9% and 26.1% was achieved in the leach, when the ore was previously calcined at 250 °C, 430 °C, 550 °C and 800 °C for 2 h, respectively. The increased nickel extraction from the pre-treated ore was believed to be partly due to increased surface area created through water removal from the goethite structure during the dehydroxylation process. Nickel showed congruent dissolution with Fe, indicating that Ni was uniformly incorporated into the iron oxides structure. Consequently, the use of calcination as a pre treatment can enhance the nickel extraction and significantly decrease the time required for the atmospheric acid leaching step.