STUDY OF EXTRACTION SCANDIUM FROM RED MUD OF ALUMINA REFINING BY SULFATION METHOD USING AMMONIUM SULFATE, ROASTING, AND WATER LEACHING

• Main Author: Nurul Falah, Fiqri
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/66501
• Institution: Institut Teknologi Bandung

Red mud is a waste generated from the refining process of bauxite into alumina. Despite being classified as hazardous waste, red mud actually contains high levels of rare earth elements, especially scandium (Sc). This metal is widely used for strategic applications, such as aluminium (Al) alloys for aircraft materials, cathode dopants for lithium manganese oxide (LMO) batteries, and solid oxide fuel cell (SOFCs). Extraction of Sc from red mud has been studied previously by direct leaching process. However, the selectivities of the leaching by this method against iron (Fe), Al, and titanium (Ti) are low. In this experiment, the extraction of Sc from red mud produced by PT. ICA in West Kalimantan was carried out by sulfation using ammonium sulfate ((NH4)2SO4)-roasting-water leaching and the effects of several variables on Sc extraction and the leaching selectivity to Fe, Al, and Ti were studied. The series of experiments started with the red mud sample preparation which includes blending, sampling, grinding, and sieving. The initial characterization of red mud consisted of analyses with X-ray fluorescence (XRF), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), and scanning electron microscope-energy dispersive X-ray (SEM-EDX). The experiments were carried out by investigating the effect of five variables at four levels of variation for each variable on the extraction of Sc, Fe, Al, and Ti. The variables that were investigated were the ratio of (NH4)2SO4/red mud (g/g), roasting temperature (oC), roasting time (min), liquid/solid ratio (L/S) (ml/g) used in leaching, and leaching time (min). The experiment consisted of the sulfation process, roasting in a muffle furnace, and leaching in deionized water. The pregnant leach solutions and residues were analyzed using ICP-MS to determine extraction percentages of Sc, Fe, Al, Ti, and other metals. The determination of the optimum condition was carried out by analyzing the effect of each variable on the extraction percentages of Sc, Fe, Al, Ti, and the leaching selectivity. The results of the experiments showed that %extraction of Sc tended to increase with increasing (NH4)2SO4/red mud ratio up to 1.5 g/g and L/S up to 10 ml/g. The roasting’s temperature and time that exceeded 750 oC and 60 minutes tend to reduce the Sc extraction. Extraction of Sc increased significantly in the leaching time period of 30-60 min and decreased significantly in the period of 60-120 min. There was no significant change in the Sc extraction beyond this period. Based on the analysis of the experimental results, the optimum condition was obtained at the ratio (NH4)2SO4/red mud of 0,5 (g/g), roasting temperature of 750 oC, roasting time of 80 min, leaching time 30 min, and L/S ratio of 12 (ml/g). Under this condition, the average extraction percentages of Sc, Fe, Ti, and Al were 92.57%, 6.55%, 0.65%, and 31.43%, respectively, with an average selectivity of Sc/Fe, Sc/Ti, and Sc/Al of 0.93, 0.99, and 0.75, respectively.