REASSESMENT LEACHING KINETICS OF SOUTHEAST-SULAWESI LIMONITIC ORE AND EFFECTIVENESS OF SEPARATION OF IRON FROM LEACHING SOLUTION BY ELECTROOXIDATION

• Main Author: GUSMAHARANI (NIM : 12506026), MIA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/23058
• Institution: Institut Teknologi Bandung

Limonite ore is one of nickel laterite ore types, this ore contains low nickel (Ni <1.5%). The nickel production recommended for this ore is through the hydrometallurgical route. During leaching process under atmospheric pressure using an excess sulfuric acid, metal impurities such as Fe, Mg and Al will dissolve together with Ni and Co. Based on Potential-pH diagram, in an acid environment, stable species in acid solution are Ni, Co, Mg, and Al ions so that the oxides of those elements present in the ore dissolve to their ions. Therefore, the solubility of Fe, Mg and Al can not be avoided during the leaching process. The soluble iron is separated from the solution by electrooxidation process followed by pH adjustment. A series of limonite ore leaching experiments was conducted at a temperature of 100oC with sulfuric acid concentration 126.678 gr / L and 190.017 g / L for 8 hours under atmospheric pressure. Increasing concentrations of sulfuric acid increases the percent extraction of Ni and Al. The highest percent extraction of Ni and Co that can be obtained from the leaching process are 86.510% and 92.401% respectively. Study results show that the reaction kinetics of leaching was controlled by the rate of diffusion through the diffusion layer in the fluid. The kinetics follows the shrinking core model during leaching. Leaching process was followed by electrooxidation to separate iron ion from the leaching solution. The first electrooxidation processes were performed by varying the current density (i.e. 2.483 mA/cm2, 1.986 mA/cm2 and 1.490 mA/cm2) and oxidation time (1 hour, 2 hours and 4 hours) followed by addition of NaOH to raise the pH to 4. Amount of Fe that can be separated from the leaching solution reached 99.971%. Second electrooxidation experiments were performed by varying the temperature (30, 45, 60 and 75oC) and pH (3 and 4) and they are conducted at constant current density 2.483 mA/cm2 for one hour. Amount of Fe that can be separated from the leaching solution reached 99.9%. In this elektrooxidation experiment, besides precipitation of iron, Ni, Mg, Al and Co are also codeposited.