#TITLE_ALTERNATIVE#

• Main Author: FARIDA ULYA , DIYAH
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/12013
• Institution: Institut Teknologi Bandung

Indonesia is one of the countries which have large amount of nickel laterite resources. Nickel extraction from these resources via hydrometallurgical processes, especially for low grade nickel ores (e.g. LGSO), is convinced profitable to be implemented in industry. Leaching nickel from low grade saprolite ore (LGSO) in a sulfuric acid medium under atmospheric pressure has been expected to yield high percentage of nickel extraction and enable it to be applied commercially.<p> <br /> <br /> <br /> <br /> A series of leaching tests of nickel from LGSO has been carried out for 8 hours in several leaching media and at different temperatures. Leaching tests for studying kinetics of leaching process are conducted in 1 M sulfuric acid solution at 60, 85, and 950C. Since the concentration of SiO2 of the ore is high and because of this material does not dissolve during leaching, the kinetic model that is applied for the kinetics study is the shrinking core model (particle is not change with time). Plotting results of fractional conversion (XT) vs. leaching time (t) exhibit fast dissolution rate at the beginning of leaching process (?5 minutes) and the rate is significantly decreased at end of the process. Since leaching experiments are conducted with rigorous stirring, the most possible rate which controls the process is; (i) rate of chemical reaction at the interface, (ii) rate of ionic diffusion through the solution in porous ash layer, or (iii) combination of the both rates (mixed control). It is found that the determination of the step which controls the leaching process is difficult by comparing the correlation coefficients (r) from the linear relation between each fractional conversion function with leaching time (t), therefore it is then determined by considering the predicted activation energy. The study concludes that the rate of chemical reaction at the interface has controlled the rate of leaching process with activation energy of 17.76 kcal/mole at ? 5 minutes and after 10 minutes of leaching the rate of mixed control has controlled the leaching process. Besides temperature, other variables that influence the leaching process are the size of particle and the sulfuric acid concentration. Leaching with smaller particle (-200 + 325 mesh) results in higher percentage of Mg, Fe and Al dissolution, and lower nickel extraction. The effects of sulfuric acid concentration to the dissolution rate of nickel have been studied at 950C by conducting leaching tests in 3 solutions (0.2 M, 0.4 M and 1 M H2SO4). Higher nickel extraction and impurities dissolution (e.g. iron dissolution) are obtained in 1 M sulfuric acid solution. Extraction of nickel can reach 94.75% in 1 M sulfuric acid at 950C however the leaching process is not selective. Addition 20 gpl NaCl has decreased nickel extraction and slightly reduced iron dissolution but increased magnesium and aluminium dissolution. This fact is not in line with that leaching of nickel from limonitic ore in the same leaching medium[12].