Abstract
In Chile, the hydrometallurgical plants are operating below their capacity due to a depletion of copper oxide ores. To obtain suitable pregnant leach solutions (PLSs) for hydrometallurgical plants, leaching solutions combining iodine-based oxidants and hydrogen peroxide in a chloride–acid medium, at room temperature and pressure were studied. Factorial experiments were conducted to evaluate the effects of the different leaching solution reagents (KI, NaIO3, NaCl, H2O2, and H2SO4). The results showed that the most influential variable is the H2O2 concentration; increasing the PLS concentration from 3 g/L to 15 g/L increased the copper extraction percentage by ~25%. In decreasing order of importance, the factorial experimental results showed that the H2O2, H2SO4, NaCl, NaIO3, and KI concentrations affect the copper extraction percentage. The highest copper extraction percentage (i.e., 60.6%) was obtained using a leaching solution containing the highest reagent concentrations. At these conditions, the copper concentration in the PLS was 16.9 g/L. An economic evaluation of the laboratory-scale leaching experiments showed an increase in the unit cost (USD/t Cu) for experiments involving leaching solutions without H2O2 because of poor copper concentration in the PLS. As the concentrations of the reagents NaIO3 and KI, increase, the unit cost increases, because the reagents are relatively expensive and have a limited effect on the copper extraction percentage.
Highlights
Copper in the earth’s crust occurs as native copper or copper-bearing minerals such as copper sulfides and copper oxides
This study aims to develop an alternative leaching process to treat copper sulfide concentrate that yields suitable pregnant leach solutions (PLSs) for SX–EW processes, minimizing changes in the current installations
The results indicated that the copper presented a chloride complex that was bonded as a copper cation into the extractant reagent after the wash
Summary
Copper in the earth’s crust occurs as native copper or copper-bearing minerals such as copper sulfides (e.g., chalcopyrite, chalcocite, covellite, bornite, and enargite) and copper oxides (e.g., cuprite, tenorite, chrysocolla, atacamite, and brochantite). Chalcopyrite is the most abundant, accounting for 70% of all copper-bearing minerals in the earth’s crust [1]; most current reserves contain approximately 0.5% copper and are steadily depleting [2]. Because of the nature of mineral deposits and the deepening pits, copper sulfide ore extraction is increasing, whereas copper oxide ore extraction is decreasing [3,4]. According to Cochilco, Comisión Chilena del Cobre [5], the hydrometallurgical production of copper in Chile will decrease by 52% by 2030 compared to the production in 2018. Owing to the scarcity of leaching resources and no new projects in this area, it is estimated that approximately 15 Chilean hydrometallurgical plants will be closed before 2030 [6]
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