STUDY OF BIOOXIDATION EFFECT OF ROCK-TYPE GOLD WASTE MINERAL USING THE BACTERIUM Neisseria perflava STRAIN SKC/VA-3 ON GOLD EXTRACTION AFTER CYANIDATION

• Main Author: Nurul Fadhilah, Nadira
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/39854
• Institution: Institut Teknologi Bandung

Direct cyanidation on the refractory gold ore resulting in low gold extraction due to the presence of sulfide minerals included the gold, or preg-robbing minerals adsorbing gold during the leaching process. Biological oxidation pre-treatment has been developed as an alternative to ultra-fine grinding, roasting, chemical oxidation or pressured oxidation. The rock-type gold waste mineral is a mineral that surrounds ore deposit that contains low grade of valuable minerals which tend to be refractory. In this study, pre-treatment of gold waste rock mineral from Central Kalimantan was investigated by biooxidation method using iron-and sulfur-oxidizing bacteria. First, the experiment began with grinding to obtain a particle size of -75?m, then homogenization and sampling were performed for characterization, direct cyanidation process, and biooxidation. Sample characterization was carried out using X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), mineragraphy analysis, Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), Fourier-Transform Infrared Spectroscopy (FTIR), diagnostic leaching, head grade analysis, and preg-robbing analysis. A preliminary biooxidation experiment was conducted using several iron- and sulfur-oxidizing bacteria to determine the most optimum bacteria to be used in the main biooxidation experiment. The main biooxidation experiments were optimized under several variations: bacterial inoculum concentration, pyrite concentration, and FeSO4.7H2O concentration. Subsequently, cyanidation and aqua regia digestion were carried out for all samples with and without biooxidation residues for further characterization using AAS to measure the gold extraction. The analysis showed that the gold rock-type waste mineral contained sulfide minerals associated with preg-robbing minerals. The most optimum bacteria from the preliminary biooxidation experiment which further was used for the next experiment was Neisseria perflava strain SKC/VA-3 at the incubation time of 2.4 days. Under the most optimum biooxidation condition: bacterial inoculum concentration of 5% (v/v), pyrite concentration of 9 g/l, and FeSO4.7H2O concentration of 4.4 g/l, the gold extraction was 82.96% which significantly increased by 18.11% compared to direct cyanidation. This study suggested that biooxidation pre-treatment has been proven as a low-cost and environmentally friendly method to enhance the gold extraction for the refractory gold ore and thus, is potentially applicable to the field scale with further optimization.