Pressure acid leaching of Çaldağ lateritic nickel ore: An alternative to heap leaching

• The optimum conditions of HPAL for Çaldağ limonitic Ni laterite ore were determined.
• They were: 325 kg H2SO4 acid/tonne ore, 250 °C, 1 h with 100% − 1 mm particle size.
• Extraction efficiencies (%): 94.1 Ni, 94.0 Co, 1.7 Fe, 51.1 Al, 84.0 Mg and 82.2 Mn
• Scandium extraction was 90.9% with an obtained PLS concentration of 24.1 ppm.
• The leach residue obtained was characterized by SEM.

In this study, the leachability of Çaldağ lateritic nickel ore under high pressure acid leaching (HPAL) conditions was investigated. Several HPAL parameters were tested in a comparative manner since in many cases, the extraction efficiencies of Çaldağ ore sample were more than 90% for nickel and cobalt. After the optimization of the process parameters, it was found that 94.1% nickel and 94.0% cobalt could be extracted under the conditions of 325 kg sulfuric acid/tonne of dry ore, 250 °C leaching temperature, 1 h leaching duration and 100% − 1 mm particle size. Under these conditions, scandium also present in the ore was highly extracted into the pregnant leach solution. The results obtained were compared with the reported pilot plant testing results of atmospheric heap leaching by European Nickel PLC.