Perpustakaan Digital ITB

Ferronickel (FeNi) alloy is one of primary products of nickel laterite ore processing, especially from saprolite ore type. However, the processing that has been carried out up to recently is still focused on extracting its nickel metal, when in fact, the slag contains a relatively high amount of magnesium that may potentially be economically recovered. The ferronickel slag originates from the Harita Group ferronickel plant in Obi Island, North Maluku Province. The price of pure magnesium metal and the oxide is considered expensive compared to other elements. Therefore, processing of high-magnesium ferronickel slag was conducted with objectives of characterizing the slag, determining the effect of different acid solutions used, the effect of different acid concentrations used, and the effect of different solid-to-liquid ratios used on producing magnesium from ferronickel slag through acid leaching. This research divided into four stages. First, characterization of slag was carried out by analysing using XRF and ICP to determine the chemical compositions present in the raw materials. The processing of magnesium is carried out through a leaching process with 50 g of slag at 80 oC and atmospheric pressure for 6 hours with rotational speed of 450 rpm. Variations of this research are the acid solutions used (HCl; H2SO4), the acid concentrations (2 M; 6 M), and the S/L ratio (1/7.5; 1/15). Next, purification of MgCl2 solution is performed by precipitation to remove impurities by adding MgO(s) to control the pH. The MgCl2 solution results are heated at a 95 oC and pH increased gradually. Then, NH4OH is added to the increase the pH to 11-12 at room temperature to precipitate Mg in the form of Mg(OH)2(s). The precipitates are then calcined at about 1000 oC for 4 hours, and are analyzed by XRD afterwards. The %-Mg extracted for all samples are then attained using the mass of the final sample precipitate with the mass of the initial sample. In conclusion, it was found that the optimum concentration of both HCl and H2SO4 obtained is 6 M with a particle size of 100 mesh at 95 oC for 6 hours; H2SO4 is able to extract higher amount of Mg than HCl; the optimum S/L ratio of both HCl and H2SO4 obtained is 1/15. The final optimum % extraction (Mg) attained for HCl and H2SO4 are 40.1% and 48.3%, respectively. This research also concludes that the method used has achieve the objectives determined based on the XRF and ICP comparison results.