STUDY OF THE EFFECT OF BIOOXIDATION OF SULFIDIC GOLD CONCENTRATE ON GOLD RECOVERY THROUGH INTENSIVE LEACHING

• Main Author: DZIKRA ULYA SOEFIHARA (NIM : 12513049), MUHAMMAD
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/23214
• Institution: Institut Teknologi Bandung

The most commonly used refractory gold ore pretreatment methods are roasting, high pressure oxidation and chlorination. However, the cost of capital and operating activities of the pretreatment process is very high. The biooxidation pretreatment method has begun to be an alternative method because it has been technically proven to be an economical and environmentally friendly method. Iron- and sulfuroxidizing bacteria in the biooxidation process have been proposed that are able to liberate the gold which is locked in sulphide minerals. Therefore, the present study investigated the biooxidation parameters of sulfidic gold concentrate and their effects on the enhancement of gold recovery. <br /> <br /> <br /> A series of experiments were carriout out, consisting of sample preparation, biooxidation and intensive leaching experiments. Sample preparation included crushing and grinding processes to obtain a P80 particle size of 75 microns for further process (i.e., flotation). The characterization of flotation concentrate included fire assay, ICP-OES, XRD, LECO and mineragraphy analysis. The concentrates from flotation were subsequently used for biooxidation and diagnostic leaching experiments. Experiments of direct intensive leaching were also conducted for the gold concentrates without biooxidation treatment. Biooxidation experiments were carried out in a 500-ml Schott Duran bottle with the 350 ml working volume at 5% solids and a stirring speed of 180 rpm. Analysis of pH, potential and dissolved base metal content was also performed. Residues resulting from biooxidation treatment were then feeded into the intensive leaching experiments under leaching parameters of 10% solids, 5% NaCN, 0.7% NaOH and 2% leachwell. Intensive leaching was run at parameters of 10% solids, 1.5% NaCN and pH adjustment in the range of 10.5-11 by using lime. Dissolved gold content was measured using AAS to determine gold leaching efficiency. <br /> <br /> <br /> Experimental results of diagnostic leaching showed that free gold particles were only 16.8% of which gold particles were mainly associated with pyrite (23%) and arsenopyrite minerals (36.5%). Direct Intensive leaching test gave 52% of gold recovery. Citrobacter youngae as sulfur-oxidizing bacterium was the best bacteria for biooxidation process, which achieved the gold recovery of 53%, and the highest gold leaching efficiency (60.2%) was obtained for intensive leaching feeded with biooxidation residue of 15 g/l molasses under intensive leaching condition of 5% NaCN concentration and lime use for pH adjustment. The addition of elemental sulfur and pyrite to the biooxidation process did not give a significant effect on gold recovery, presumably as a result of their passivation effect on the gold particles, thereby decreasing gold recovery.