Comparative analysis of copper dissolution and mineral transformations in coarse chalcopyrite for different oxidant/lixiviant systems at elevated temperature (110 °C and 170 °C)

Abstract Chalcopyrite (CuFeS2) is the most common copper-bearing mineral and represents more than half of global copper mineral reserves. The decrease in copper reserves and increase in demand for copper has led to an increased interest in hydrometallurgical approaches to copper mining. Copper extraction from copper sulfides such as chalcopyrite, requires oxidant addition for dissolution. Although numerous lixiviants have been evaluated, limited information is available regarding fluid–rock interactions during the leaching of coarse chalcopyrite samples at high temperature, including their stabilities and secondary product formation. This study compares the thermal stability of eleven oxidant/lixiviant systems (sulfuric acid, methanesulfonic acid, ammonium hydroxide, hydrochloric acid and glycine, and oxidants, including oxygen, iron(III), copper(II), dichromate, sodium nitrate, peroxydisulfate and hydrogen peroxide) and their ability to leach copper from chalcopyrite at 110 °C (below the sulfur melting point) and 170 °C (above the sulfur melting point) under similar conditions. Tests were conducted for up to 576 h using solid cuboids (4 mm side lengths) to simulate in situ recovery conditions. Sealed batch and Parr reactors were used to simulate an anoxic environment that may be encountered in a subterranean application. This paper presents the findings from the study and compares the leaching systems at 110 °C and 170 °C based on copper release into solution, reaction products, passivation phenomena and textural analysis. The application potential of the systems for in situ recovery from deep copper ore bodies is discussed based on the performance of the chosen systems.