Primary Copper Ore Leaching by Leaching Solution Adjusted Oxidation-Reduction Potential in Column

Abstract

Copper ore is classified into three groups; primary copper sulfide, copper oxide and secondary copper sulfide. Leaching copper from primary copper sulfide, such as chalcopyrite, with sulfuric acid takes longer time than from copper oxide and secondary copper sulfide. As such, an oxidant is required to extract copper from chalcopyrite. In this study, column leaching tests were carried out using primary copper sulfide ores produced in an iron oxide copper gold (IOCG) deposit and rich in iron in coparison to porphyry copper ores. The columns of 10 cm diameter and 100 cm long had a double tube structure so that the column temperature can be kept at desired temperature by circulating warm water in the outer tube. The oxidation-reduction potential (ORP) of the leaching solutions were adjustedto 400, 450 and 500 mV vs Ag/AgCl. The column leaching test using just pH 2.0 sulfuric acid without adjustment of ORP at 45 °C got a copper recovery rate of 37 % in 400 days. On the other hand, with ORP adjusted leaching solutions of pH 2.0 sulfuric acid containing 500 mg/L Fe, the copper recovery rate reached up to 87 % in 400 days.In addition, it was necessary to keep the temperature above 45 oC to enhance copper leaching by ORP adjusted leaching solution. The result of the column leaching test at room temperature (around 30 °C) using ORP adjusted leaching solution shows that the recovery rate of copper is lower than the result at 45 °C. The ORP adjustment of leaching solution is effective for leaching copper from primary copper sulfide ore, however, the leaching temperature needs to be kept above 45 °C. As a result, it makes clear that copper leaching is enhanced by utilization of ORP adjusted leaching solutions and suggests that the solution ORP control is important to the application of bioleaching.