Statistically-designed experiments were conducted to study and optimize column leaching, simulating heap leaching, of low-grade nickel oxide ores with sulphuric acid at ambient temperature. The ore tested was hematitic laterite with Ni 0.91percent, Co 0.065percent, Fe 31.97percent, Mg 1.65percent, Al 3.14percent, Cr 1.54percent, Ca 0.065percent and SiO_2 33.49percent. Its mineralogical analysis is also given. Leach columns were made of PVC with internal diameter 25cm and height 2.5m. The variables studied were: feed grain size, sulphuric acid concentration in the leach solution, ratio of the leach solution volume to the ore weight, and leach solution flowrate. Responses measured included: nickel, cobalt, iron, magnesium, aluminium, chromium, calcium, silicon, potassium and manganese extraction, Fe/Ni ratio in the leach liquor and sulphuric acid consumption. Nickel recoveries up to 85percent were obtained in less than 40 days. The ratio Fe/Ni in the leach liquors averaged 4/1, much lower than the value of this ratio in the ore (35/1). Mineralogical analyses of the leach residues were also conducted and the mechanism of laterite heap leaching established.
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