BIOLEACHING OF RARE EARTH ELEMENTS (REE) FROM RED MUD WASTE OF THE BAUXITE ORE PROCESSING INDUSTRY IN TAYAN, WEST KALIMANTAN USING THE BACILLUS ARYABHATTAI STRAIN SKC-5 BACTERIA WITH IRON-SELECTIVE BIOFLOCCULATION PRE-TREATMENT

• Main Author: Daffa Alfarisi, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/77308
• Institution: Institut Teknologi Bandung

Red mud is a residue produced from the bayer process which processed bauxite ore into alumina. Red mud contains precious metals such as Fe, Al, Ti and rare earth elements (REEs) such as Sc, Y, La, Ce, and Pr which causing this waste to be toxic and could cause environmental pollution. Generally, metal extraction from red mud waste usually carried out by hydrometallurgical methods. However, there is an alternative to the hydrometallurgical process to extract metal from red mud that is called biohydrometallurgy. Biohydrometallurgy method is an environmental friendly method, only needs a little energy, and able to extract metals with very low concentrations. In this study, bioflocculation pre-treatment is conducted to the initial red mud sample then the metal extraction of red mud is carried out using bioleaching method using Bacillus aryabhattai Strain SKC-5 bacteria as a leaching agent. Series of experiments are conducted to optimize the bioleaching experiment and to study the effect of bioflocculation pre-treatment, variations of pulp density, bioleaching time, and feed on the percent of REE extraction. The bioflocculation pre-treatment was carried out with slurry pH condition of 7 and 5-8 minutes settling time using Bacillus nitratireducens strain SKC/L-2 bacteria. The bioleaching process was conducted in a room temperature (± 25 oC), medium pH 1, red mud particle size of 200# (74?m), 10% (v/v) bactery inoculation, and rotary shaker speed of 183 rpm for 14 days. This experiments were carried out at variations of 2% and 5% pulp density, 14 and 21 days of bioleaching time, and feed variations of dry red mud, slurry precipitate from bioflocculation, and supernatant precipitate from biofloculation. 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, bioflocculation pre-treatment on red mud generates better extraction rates than red mud without bioflocculation. The value of average REE extraction percentage is 61,71%. The higher pulp density level could cause more toxic environment and reduce the bacteria ability to extract metal. Bioleaching time that are too long could cause the environment to became different and also could cause the bacteria to reach their death phase thus hinder the extraction process. The difference of feed could also reduce the bacteria ability to extract metals because different red mud feed contains different kind of metal and also contain inhibitory compound such as sodium hydroxide and sodium carbonate the best bioleaching process parameter is the 2% pulp density with the feed of slurry precipitate from bioflooculation pre-treatment with bioleaching time of 14 days. The value of REE extraction percentage are 92,15% Ce; 89,37% La; 86,72% Er; 85,08% Y; 84,99% Ho; 83,24% Eu; 80,28% Yb; 79,71% Pr; 77,21% Nd; 75,37% Gd; 74,75% Dy; 74,75% Tb; 73,46% Sm; 70,92% Tm; 59,75% Lu; dan 41,57% Sc.