Decomposition of organic additives in the oxidative chalcopyrite leaching with hydrogen peroxide

Abstract

Recent investigations have shown that the addition of short-chain organic additives (methanol, ethanol, ethylene glycol, acetone, isopropanol, formic and acetic acids), surfactants (Tween 20 and 80) and organic ligands (EDTA, oxalic and citric acids) in acidic leaching solutions with hydrogen peroxide, significantly promote chalcopyrite dissolution. However, despite these positive findings, until now, the relation between the percentage of dissolution of chalcopyrite, hydrogen peroxide decomposition by Fenton and Fenton type reactions, and the level of decomposition (partial or complete oxidation to CO2 and H2O) of organic additives due to electrophilic attack by the OH* radical, has not been reported. For that reason, a systematic study was undertaken to explore those aspects. The results demonstrated that all the organic additives slowed, but did not prevent the decomposition of hydrogen peroxide, which favored the production of OH*, a radical with elevated oxidizing power capable of promoting the oxidation of organic additives. The degree of organic compound (RH) mineralization (complete oxidation to CO2 and H2O) was structure-dependent, as well as the R* reactivity with H2O2, dissolved copper and iron, although it was not proportional to H2O2 decomposition. Finally, it was found that cyclohexanol is the most promising organic additive because it greatly slows the decomposition of hydrogen peroxide, but it is not mineralized by the OH* radical, and substantially improves chalcopyrite dissolution.