Investigation of the effect of mechanical activation on nickel and cobalt extraction from laterite at atmospheric pressure by kinetics and leach residue analysis

Nickel and cobalt extraction from laterite has been studied for years but has not been investigated enough by leach residue analysis. Also, the kinetic approach and leach residue analysis become important when mechanical activation improves nickel and cobalt extraction. Various kinetic assumptions were applied to understand the dissolution behaviour of Ni, Co, and Fe. The ore was activated mechanically in a planetary ball mill as a pre-treatment. The effects of liquid-to-solid ratio, acid ratio, leaching time, and temperature on the leaching of non-activated ore were studied to fix the parameters for the leaching of pre-treated ore. Leaching efficiencies of activated ore for 15 and 60 min exhibited better results at lower temperatures and shorter times than non-activated ore. Nickel extraction has 70% efficiency for 5 min leaching at 95°C in mechanically activated ore. Besides higher dissolution efficiency, apparent activation energy (Ea) decreased. Dissolution of metals from non-activated and activated ore was found to be mixed-controlled. Two different diffusion-controlled mechanisms that differ in the diffusion coefficient-time relationship were detected. An analysis of leach residue supported this finding.