Optimization of process parameters and dissolution kinetics of nickel and cobalt from lateritic chromite overburden using organic acids

Abstract

Abstract BACKGROUND Leaching kinetics of the roasted (at 600°C) chromite overburden of Sukinda mines Orissa, India, was studied with optimized data generated through response surface methodology ( RSM ) coupled with Box‐Behnken design ( BBD ). The effects of oxalic, citric and gluconic acid concentration (50–150 mmol L −1 ), reaction temperature (60° to 80°C) and period (up to 3 h) on metal (nickel and cobalt) dissolution were examined. RESULTS Extraction of nickel and cobalt to the extent of 63.61% and 44.33%, respectively, was achieved using 150 mmol L −1 oxalic acid at 80°C in 3 h; compared with other acids, oxalic acid leached more of the metals. Associated apparent activation energy for Ni was 74 kJ mol −1 , and that for cobalt was 84.37 kJ mol −1 during the first hour, and 80.99 kJ mol −1 for the remaining period since cobalt leaching followed biphasic kinetics. CONCLUSION Dissolution of nickel and cobalt from the roasted chromite overburden was highly dependent on the amenability of ore minerals to organic acid attack. Nickel leaching data fit the three‐dimensional diffusion mechanism of the type Ginstling Brounsthein ( GB ) equation while a mixed kinetic model consisting of spherical geometry and the GB equation was followed for cobalt. This work presents maximum recovery of nickel and cobalt from chromite overburden using organic acid reported to date. © 2013 Society of Chemical Industry