New insights into oxidative-reductive leaching of chalcopyrite concentrate using a central composite factorial design

Abstract

• A response surface with high statistical confidence (R 2 = 0.997) was obtained using CCD. • The optimum condition for chalcopyrite dissolution (∼90%) was obtained using CCD. • High copper extraction was obtained for [Fe 2+ ] i :ρ pulp ratio around to 80. • Response surface methodology with the parameters [Fe 2+ ] i and ρ pulp is a new approach. • For an efficient leaching, the Fe 3+ ions concentration cannot be so high that E S > E 1 . A response surface capable of describing the extraction of copper with high statistical confidence (R 2 = 0.9973) was obtained using a central composite factorial design (CCD). The parameters used were the initial concentration of Fe 2+ ions ([Fe 2+ ] i ) and pulp density (ρ pulp ). The results evidenced that chalcopyrite leaching was strongly influenced by the solution potential, which was a function of the [Fe 2+ ] i :ρ pulp ratio. The optimal parameters obtained for maximizing the copper extraction percentage were those that satisfied a [Fe 2+ ] i :ρ pulp ratio of ≈ 80 (mmol L −1 /%), in the range from 200 to 398 mmol L −1 of Fe 2+ . The [Fe 2+ ] i :ρ pulp ratio of ≈ 80 allowed an optimal range of solution potential for most of the experiment duration, which provided a copper extraction of 91 ± 3% in 28 days, under moderate conditions. The leaching residues were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffractometry (XRD), and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS). The mathematical model, together with the calculated Nernst potentials of the main oxidation–reduction reactions of chalcopyrite, indicated that the copper extraction was governed by experimental conditions that favored chalcopyrite reduction coupled with the chalcocite oxidation reaction. Hypotheses to explain the reasons for certain experimental conditions that could increase or decrease chalcopyrite dissolution were formulated and are extensively discussed. These findings contribute to the development of new routes for the processing of chalcopyrite mineral.