BIOLEACHING OF RARE EARTH METALS FROM RED MUD WASTE FROM BAUXITE ORE PROCESSING INDUSTRY IN TAYAN, WEST KALIMANTAN USING PAENIBACILLUS PASADENENSIS STRAIN SKC/S-7 BACTERIA

• Main Author: Supriyono, Anggi
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69077
• Institution: Institut Teknologi Bandung

Red mud is a residue produced from the Bayer process of processing bauxite ore into alumina. Red mud contains precious metals such as Fe, Al, Ti and rare earth elements (REE) such as Ce, Sc, Y, Nd and Gd which cause this waste to be toxic and can cause environmental pollution. Metal extraction from red mud waste is generally carried out by hydrometallurgical methods. As an alternative to the hydrometallurgical process, a metal extraction method from red mud was developed using the biohydrometallurgical pathway. Biohydrometallurgy is an environmentally friendly method, requires little energy and can extract metals at very low concentrations. In this study, the extraction of REE from red mud from the bauxite ore processing industry in Tayan, West Kalimantan was studied by the bioleaching method using the bacterium Paenibacillus pasadenensis Strain SKC/S- 7 as a leaching agent. A series of bioleaching experiments were carried out to study the effect of pulp density and bioleaching medium on the percent of REE extraction. The bioleaching process was carried out at room temperature (± 25 °C), medium pH 1, red mud particle size -200# +270# (-75 ?m +53 ?m), 10% (v/v) bacterial inoculum and rotary shaker speed 183 rpm for 7 days. Bioleaching experiments were carried out at variations of 2% and 5% pulp density and four variations of the medium as follows: 4 g/L molasses, adding 5 g/L sulfur, adding 5 g/L sulfur and 2.8 g/L pyrite and adding 10 g /L sulfur and 5.6 g/L pyrite. Percentage of REE extraction as a function of time under various bioleaching conditions was periodically determined by ICP-MS (inductively coupled plasma-mass spectrometry) analysis. Based on the experimental results, the best bioleaching process parameter is the variation of 2% pulp density in medium 4 (4 g/L molasses, 10 g/L sulfur, 5.6 g/L pyrite) with a percent REE extraction value of 73.35% Tm ; 68.11% Eu; 61.32% La; 58.85% Y; 51.7% Nd; 38.46% Pr; 22.48 Ce; 6.8% Yb; 4.84% Sc; 4.3% Ho; 4.75% Gd; 3.47% Lu and 2.45% Tb. The increase in pulp density causes a decrease in the percent REE extraction due to cell damage, a decrease in O2 concentration and agitation effects due to increased solution viscosity and inhibited bacterial growth due to an increase in metal concentration in the bioleaching medium which is toxic. The decrease in the percentage of REE extraction in the medium without the addition of sulfur and pyrite was caused by bacteria lacking energy supply. Sulfur acts as a source of sulfide compounds which are needed as electron donors for bacterial metabolism, while pyrite acts as a source of Fe2+ to increase the redox potential value in the bioleaching process.