Effect of mechanical activation on nickel and cobalt extraction in refractory nickel laterite ore

The kinetics of atmospheric stirred tank leaching of nickel and cobalt from complex, low grade laterite ores at low to moderate temperatures are inherently slow, warranting efficacious strategies for improvement. In this work, the effect of mechanical activation as a pre-treatment method on pulp acid leaching behaviour of cobalt and nickel from low-grade goethitic nickel laterite ore was studied. At pH 1, 70 °C, and 4 h H 2 SO 4 leaching, Ni and Co recoveries for the 60 min mechanically activated sample both increased by a factor of ~2, achieving ~15 % recovery. Extended leaching times further improved recoveries, with Ni and Co extractions reaching ~63 % and ~ 72 %, respectively, for the MA sample, compared to ~39 % and ~ 54 % for the as-received sample. At higher acid concentrations and temperatures, Ni and Co recoveries exceeded 90 % for the MA sample due to enhanced leaching kinetics. The study demonstrates that phase alterations, induced by mechanical activation, and concomitant increase in surface area significantly improved leaching efficiency. However, increased acid consumption was observed due to gangue leaching. These findings highlight the potential of stirred milling-based mechanical activation as a scalable pre-treatment method to enhance nickel and cobalt recovery from refractory laterite ores while addressing kinetic limitations in atmospheric leaching processes. • The refractory nature of goethitic nickel laterite ore necessitates pretreatment strategies such as mechanical activation to enhance extraction. • Mechanical activation significantly reduces particle size, increases surface area, and induces structural alterations, improving leaching kinetics and reaction efficiency. • Prolonged mechanical activation does not always enhance ore processability, emphasizing process optimisation to avoid unnecessary operational costs. • Increased leach time and lower acid concentrations translate to pronounced impact of mechanical activation on leach rates. • Reduced gangue dissolution, offering better selectivity compared to higher acid concentrations