STUDY OF THE EFFECT OF BIOOXIDATION OF BANYUWANGI REFRACTORY GOLD ORE USING CITROBACTER FREUNDII STRAIN SKC-4 BACTERIA ON GOLD EXTRACTION THROUGH CYANIDATION

• Main Author: Arif Kurniawan, Satrio
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/39453
• Institution: Institut Teknologi Bandung

As time passed, the availability of non-refractory gold ore which is easier to process is decreasing, causing the refractory gold ore becomes more valuable source by the gold processing industry. Prior to processing the refractory gold ore, pre-treatment is required, one of them is biooxidation method which began to be a proven alternative method for pre-treatment due to its eco-friendliness. In this study, gold ore from Banyuwangi contains low grade of gold and high impurity minerals which leads to ore processing problems. Therefore, biooxidation experiment of Banyuwangi gold ore was carried out using iron- and sulfur-oxidizing bacteria. A series of the experiment was initiated with ore preparation by crushing and grinding followed by sieving to obtain a particle size of 200 mesh (-200#) or 75 microns (-75 ?m). Later, the ore was homogenized and sampled for the purpose of ore sample characterization and biooxidation experiments. The ore characterization was performed using XRD, XRF, mineragraphy analysis, head grade analysis, diagnostic leaching, and FTIR. First, the experiment was started by constructing the bacterial growth curve to determine the optimal incubation time of bacteria to be used in the experiments and bacterial screening. Then, the preliminary biooxidation experiment was carried out using selected iron- and sulfur-oxidizing bacteria from screening results which aimed to determine the most optimum bacteria in the experiment. In parallel, direct cyanidation was also carried out on ore without biooxidation treatment which aimed to investigate the effect of biooxidation step in increasing the gold extraction. After that, the core biooxidation experiment was conducted using the most optimum bacteria with several variations including media, bacterial inoculum concentration, and biooxidation time. All of the residual biooxidation experiments were treated by cyanidation, followed by aqua regia digestion of cyanidation residues. Finally, characterization of the biooxidation residue which resulted from the highest gold recovery were analyzed using XRD and FTIR. The characterization results showed that Banyuwangi gold ore contained impurities, including quartz, sulfide, carbonate, and clay minerals. The most optimum iron- and sulfur-oxidizing bacteria was Citrobacter freundii strain SKC-4. Direct cyanidation without biooxidation treatment resulted in 19.7% of gold extraction. Under the most optimum condition, gold extraction can be enhanced up to 43.7% on SKC-Broth modified 1 medium with the composition of seawater, 9 g/l pyrite, 4 g/l molasses, 2 g/l FeSO4.7H2O, and with pH adjustment to 1, 10% (v/v) bacterial inoculum, for 7 days biooxidation.