CHARACTERIZATION OF GOLD TAILING FROM PONGKOR AND STUDY THE EFFECT OF BIOOXIDATION BY USING Citrobacter youngae AND Bacillus megaterium BACTERIA ON GOLD EXTRACTION

• Main Author: PURNOMO (NIM : 22116013), ITO
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/28173
• Institution: Institut Teknologi Bandung

Gold extraction from secondary sources is continuosly developed due to the increase of the world's gold demand. One of the secondary gold sources comes from tailings resulted from cyanidation process. The discharge of gold into the tailing caused by refractory gold characteristics or dissolved gold trapped in the fine carbon fraction either those which are present in ore or those from activated carbon which passed through the safety screen and discharged to the tailings. The selection of the effective pre-treatment method for recovering gold depends on the characteristics of the tailings. The purpose of this study was to study the characteristics of gold from tailings and the effect of bio-oxidation by using Citrobacter youngae and Bacillus megaterium on the improvement of gold extraction percentage by cyanidation. <br /> <br /> Diagnostic leaching result from tailings of Pongkor Gold Processing Plant, PT. Antam Tbk shows that the gold in tailings is mostly trapped in complex oxide minerals (48%) and pyrite (30%), while a small portion in calcite minerals (4%), silicate (2%), carbon (2%) and about 14% is free gold. Based on the XRD analysis, the complex oxide minerals in Pongkor gold tailings consist of sanidine (KAlSi3O8) and albite (NaAlSi3O8). Gold trapped in pyrite can be oxidized using iron and sulfur-oxidizing bacteria, while gold in complex oxide minerals can be liberated in a process of pre-cyanidation by using hydrochloric acid leaching. <br /> <br /> The experiments show that the biooxidation process using Citrobacter youngae and Bacillus megaterium able to increase the recovery of gold in the cyanidation process from 17.85% to 23.95% and 25.43%, respectively. This result was reached from the biooxidation parameters at 5% solids, the addition of 7 g/L FeSO4.7H2O and the particle size of -100+200 mesh. The addition of pyrite as iron and sulfur source causes a decreasing of estimated gold extraction because the addition of pyrite causes passivation of gold grains in the cyanidation stage. Based on the these results, C. youngae was able to oxidize gold in pyrite in tailings samples by 20.33% <br /> <br /> of the total gold locked in the pyrite, while B. megaterium was able to oxidize 25.27% gold in pyrite. In the pre-cyanidation process using 1 molar HCl, the highest percentage of gold extraction was 57.34% which was indicated that gold could be liberated as much as 82.27% of the total gold trapped in complex oxide minerals.