Extraction Of Nickel And Cobalt From Ramu Laterite Ore ? Papua New Guinea

The extraction of nickel (Ni) and cobalt (Co) from the laterite deposit of Ramu nickel-cobalt Project in Papua New Guinea was performed in this study. Chemical analysis by Inductively Coupled Plasma (ICP-AES) atomic emission spectrometer, SPS-3000 (Seiko Instruments (Inc.), shows the ore contains 48% Fe, 1% Ni, 0.1% Co, 1.8% Al, 0.14% Mg, and 0.8% Mn. Characterization by X-ray diffraction (XRD) analysis of the laterite ore obtained from the mine site shows the ore contains 70 to 80% goethite (FeOOH), assuming Fe content of 48% is mainly from geothite. The main leaching parameters investigated include; slurry temperature, leaching time and sulphuric acid (H2SO4) concentration to evaluate nickel and cobalt extraction. For all experiments, 10g batch samples are put into 300 ml beaker containing 100 ml of sulphuric acid of varying concentrations (1M, 2M, 4M). During the leaching period, 5 ml slurry samples are withdrawn at different times and filtered to obtain filtrate for ICP analysis to monitor nickel and cobalt extraction. Solid samples at the end of all tests are also obtained by filtration and after drying, XRD and ICP tests are performed to monitor nickel and cobalt contents. According to the test results performed at normal atmospheric pressure, over 99% of nickel and over 50% cobalt were extracted into solution within 120 min at 95ºC in 2M H2SO4 solution. Similar results were obtained when only temperature was reduced to 90ºC, but cobalt extraction increased to over 70% when leaching time was increased to 240 min. Further reduction in temperature to 80 and 60ºC resulted in reduction of nickel and cobalt extraction. At the end of each leaching test, magnetite was seen to attach to magnetic stirrer. The study showed nickel can be completely leached into solution but cobalt only up to 70%. Keywords: atmospheric pressure, sulphuric acid leaching, nickel laterite