A STUDY OF CALCIUM BIOLEACHING FROM THE KRAKATAU POSCO STEEL SLAGS USING THE BACTERIUM DIETZIA PSYCHRALCALIPHILA STRAIN SKC-1

• Main Author: Sains Ilhami Ahmada, Alvin
• Format: Final Project
• Language: Indonesia
• Subjects: Metalurgi
• Online Access: https://digilib.itb.ac.id/gdl/view/68783
• Institution: Institut Teknologi Bandung

Calcium is a chemical element that belongs to the group IIA alkaline earth metals. Calcium is used as a sulfur binding agent in steel refining and used as a cementation agent to strengthen soils. Calcium is often found as limestone (CaCO3), gypsum (CaSO4.2H2O), complex silicates, and fluorite (CaF2). In addition, calcium is also found in secondary sources such as steel slag. Steel slag has been used in various worlds, one of which is as a cementation agent to increase soil strength by utilizing high calcium content. So it is necessary to dissolve calcium from steel slag, one of the methods is using bioleaching. In this experiment, bioleaching of steel slag from PT. Krakatau Posco with Dietzia psychralcaliphila strain SKC-1 through direct bioleaching method. The research begins with ore preparation through comminution, sieving, and sampling. The samples were characterized using X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Fourier Transform Infrared (FTIR). The growth and adaptation process was carried out on five bacteria that would be used for bioleaching, namely Proteus mirabilis strain SKC-7 (CCorr), Bacillus nitratireducens strain SKC-2A (MPKU), Dietzia psychralcaliphila strain SKC-1 (APKU), Bacillus altitudinis strain SKC/YLP-1 (YLP-1), and Citrobacter freundii strain SKC-4 (BS-5). The two best adapted bacteria were selected and used for the core experiment. The variations carried out in the leaching process are the type of bacteria, the bioleaching condition, pulp density, and sample size fraction. Leaching was carried out using a gyratory shaker at a speed of 180 rpm and room temperature (250C). The results of sample characterization showed that the sample had high calcium and iron content. The best calcium extraction was achieved under leaching conditions using Dietzia psychralcaliphila strain SKC-1 (APKU), aerobic conditions, pulp density 10%, and sample size fraction 88-125 microns. This condition resulted in calcium extraction of 2916.981 ppm or 9.98%. This relatively low extraction yield due to the formation of calcium carbonate deposits as a result of the reaction between carbonate ions and calcium ions, as seen in the residue analysis using FTIR. However, when compared with previous studies, this experiment obtained higher calcium extraction results.