STUDY OF THE EFFECT OF BIOOXIDATION OF GOLD ORE FROM KATINGAN (KALIMANTAN) ISLAND USING Citrobacter youngae, Comamonas testosteroni, AND Neisseria flavescens ON GOLD RECOVERY THROUGH LEACHING

• Main Author: SINAGA - Nim: 12514050 , SUPRADONA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/31142
• Institution: Institut Teknologi Bandung

<p align="justify">Refractory gold ore is not effective to be extracted by direct leaching. Some types of refractory gold ores are sulfidic gold ore, carbonaceous gold ore, telluride gold ore, and their combination. Extraction of refractory gold ore to oxidize gangue minerals is conducted by roasting or pressure oxidation. However, these methods are not economical due to high operation cost. One of the considered methods to treat refractory gold ore is biooxidation method. Biooxidation is a new method with simply operation, and enviromentally friendly way, and offers the economic cost of operation. The present study, hence focused on using mixotrophic bacteria to oxidize gangue minerals that entrap gold particle especially carbonaceous minerals. <br /> <br /> <br /> A series of experiments consisting of sample preparation, biooxidation processes, and leaching process were carried out to study some effects of biooxidation on gold recovery. Sample preparation included crushing, grinding, and sieving to obtain a particle size of 75 micrometer. Biooxidation of pyrite was carried out to study the capability of bacteria to oxidize iron and to obtain the optimum concentration of pyrite for bioxidation of gold ore. Biooxidation of gold ore was undertaken by varying three types of bacteria, pulp density, and NaCl addition. Experiments were conducted in a 500 mL Erlenmeyer flasks with 350 mL working volume and bacterial inoculation of 10% (v/v), a strirring speed of 180 rpm for 7 days. Analysis of pH and redox potential (Eh) were also carried out during the biooxidation process. The characterization of biooxidation residue using X-ray diffraction was carried out to evaluate the change of mineral components due to biooxidation. Direct leaching and cyanidation of biooxidation residue were also carried out under leaching parameters of 10% solid (w/v), 1000 ppm of NaCN, pH adjustment in the range of 10-11, and dissolved oxygen in the range of 7-15 ppm for 24 hours. Dissolved gold and iron were measured using AAS to determine the leaching efficiency. <br /> <br /> <br /> Recovery of Au obtained by direct cyanidation process was 70,74%. The highest gold recovery by cyanidation of biooxidation residue was obtained at 15% (w/v) pulp density and 29.25 g/L NaCl, which reached 88.89% and 82.55%, respectively, by using the bacterium Neisseria flavescens. On the other hand, the addition of NaCl decreased gold recovery. This might be caused by the high concentration of Cl- ion which was toxic for bacterial growth. Based on the gold recovery obtained, the best bacterium for biooxidation of gold ore was Neisseria flavescens.<p align="justify"> <br />