Extraction of metals from chalcopyrite concentrate by two stage leaching

Copper production from sulphide ores and concentrates, to a large extent, have been accomplished by using pyrometallurgical techniques that consists thesmelting processes at high temperatures. Production of copper from chalcopyrite concentrate by pyrometallurgical methods occurs the basic steps which obtained matte exposes the converting process to get blister copper. However, this high temperature process has been plagued with environmental issues concerning pollution, not only with SO2 gas emissions but also with emissions of toxic compounds of arsenic, antimony, and other heavy metals. About 80% of the world's copper comes from copper sulphide ores and the remaining 20% of primary of copper production comes from hydrometallurgical processing of Cu oxide ores. Alternatively, the leaching of chalcopyrite concentrates has been considered for many years as available option to minimizing atmospheric pollution during copper production. In the hydrometallurgical copper production, the copper is recovered by leaching, solvent extraction and electrowinning. Chalcopyrite requires strong oxidants because it is an insoluble, covalent compound, like most sulphide minerals. Nevertheless, the use of oxidizing agents brings some problems, such as non-selective leaching, low metal extraction (occurring to elemental sulphur on the particle surface, depending on oxidizing of S2- to S°). In this study, hydrometallurgical selective metal extraction from chalcopyrite concentrate was performed with two-stage leaching processes. First stage leaching included the leaching of chalcopyrite concentrate with oxalic acid in presence of hydrogen peroxide. Optimum conditions of first stage leaching was determined as 100 g/L of H2C2O4, 3 M of H2O2, 45 ºC leaching temperature, 400 rpm of stirring speed, 25 mL/g of liquid-solid ratio, and 120 min leaching time. Under these conditions, copper and iron dissolution from chalcopyrite was achieved as 1.6% and 65.5%, respectively. In the second stage leaching process, first stage leaching residue was leached with HCl to obtain copper extraction. Optimum leaching conditions were found as follows: HCl concentration is 5 M; leaching temperature is 45 ºC; stirring speed is: 400 rpm; liquid-solid ratio is 25 mL/g; and leaching time is 120 min. Under these conditions, copper extraction yield was obtained at about 75% while iron dissolution was obtained at about 4%. According to obtained the experimental results, it was presented that selective leaching of chalcopyrite concentrate with two-stage process may be accomplished based on different dissolution ratio of copper and iron oxalate compounds.