Extraction of nickel and cobalt from lateritic ores by nitric acid /

Saka, Onur
This thesis study is related to the extraction kinetics of nickel and cobalt from lateritic nickel ores from Gördes/Manisa region of Turkey. The experimental studies involved the optimization of nitric acid leaching of nickel laterite ores at atmospheric pressure for high nickel and cobalt extraction. The main parameters optimized after the characterization of laterites were the nitric acid concentration, leaching temperature, duration of leaching and the particle size of the ore sample. The atmospheric leaching experiments were conducted on the 70% limonitic 30% nontronitic ore mixture obtained from the Gördes open pit mine. Considering the similar studies from literature and highest nickel and cobalt extraction into account, the process parameters optimized as; leaching at 104°C with 378 g/L nitric acid concentration, 48 hours of experiment duration, -600 µm particle size using S/L ratio of 1/5 wt/vol. 95.4% nickel and 96.6% cobalt were extracted at the given leaching conditions. Atmospheric leaching produced a contaminated pregnant leach solution (PLS) due to high iron and aluminum contents. A stock of PLS was produced for the selective precipitation for the impurities. Iron, aluminum and chromium which are the main impurity elements were almost completely removed from leach liquor with low nickel and cobalt losses.