BIOLEACHING OF RARE EARTH ELEMENTS (REE) FROM RED MUD WASTE OF BAUXITE ORE PROCESSING IN TAYAN, WEST KALIMANTAN USING ALICYCLOBACILLUS SP. STRAIN SKC-23 WITH SELECTIVE BIOFLOCCULATION PRE-TREATMENT

• Main Author: Talya, Shayne
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/77588
• Institution: Institut Teknologi Bandung

Red mud is a waste generated from alumina production from bauxite via the Bayer process. Untreated red mud can pollute the environment because it has fine particle size, is corrosive and contains toxic elements. Red mud contains valuable metals such as Fe, Al, Ti amd REEs which has high values in international market. Extraction of REE from red mud through biohydrometallurgical approach has attracted the researchers. However, the percentage of extraction is relatively low because some of the REEs are trapped in the solid matrix of iron minerals. In this study, red mud originating from the bauxite ore processing industry in Tayan, West Kalimantan was pretreated in the form of selective iron bioflocculation using Bacillus nitratireducens strain SKC/L-2 as a bioflocculant. Next, bioleaching of the precipitate resulting from bioflocculation was carried out using the bacteria Alicyclobacillus sp. strain SKC-23 to extract REE. A series of selective bioflocculation and bioleaching experiments were carried out to study the effect of pre-treatment, pulp density and bioleaching time on the percentage of REE extraction. After the red mud has been prepared, a pre-treatment process of selective bioflocculation of iron from the red mud is carried out. Selective bioflocculation experiment using Bacillus nitratireducens strain SKC /L- 2 was carried out at pH 7, slurry concentration of 10 g/L, volume ratio of slurry and bioflocculant 8:2 and settling time of 5 minutes in a 100 mL graduated cylinder. Furthermore, bioleaching experiments were carried out at room temperature (±25?), medium pH 1, 10% (v/v) bacterial inoculum and rotary shaker speed of 183 rpm for 14-21 days. The bioleaching experiment was carried out on variations of red mud feed without pre-treatment, precipitate from bioflocculation and supernatant precipitate, 2% and 5% pulp density variation, and 14 and 21 days bioleaching variation. The percentage of REE extraction as a function of time under various bioleaching conditions is periodically determined by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) analysis. Pre-treatment of selective iron bioflocculation from red mud can increase the percentage of REE extraction in the bioleaching process because it is able to separate some of the REEs trapped in a solid matrix of iron minerals. Bioleaching of precipitate from bioflocculation results in a higher percentage of REE extraction than bioleaching of red mud without pre-treatment with a total REE extraction of 39.28%. At a lower pulp density, the EPS produced is higher so that the attachment of bacteria to the mineral surface is stronger and the REE extraction increases. The longer the bioleaching time, the amount of metal extracted will also increase but if it takes too long the bacteria can reach the death phase due to the accumulation of toxic substances from the red mud which hinders the extraction process. The best bioleaching parameter is 2% pulp density with precipitate from bioflocculation as feed for 14 days. The percent extraction values obtained were 81.93% Eu; 83.71% Ce; 74.73% Nd; 73.48% Gd; 64.95% LA; 69.06% Dy; 61.84% Er; 43.29% Yb; 29.43% Sc; 26.97% Y; 28.1% Pr; 24.59% Ho; 24.05% Tb; 19.75% Sm; 14.86% Lu; 12.63% Tm.