Abstract
A study of the pretreatment stage and subsequent leaching of a mixed copper ore with different chloride solutions containing iron was carried out. The first stage considered pretreatment tests to decide the best conditions. Two levels of each factor were analyzed, 20 and 50 kg/t of NaCl, 17 and 25 kg/t of H2SO4, 0 and 25 kg/t of Fe2(SO4)3·9.2H2O, 0 and 25 kg/t of Fe2SO4·7H2O, and a curing time of 15 and 30 days. The results showed a significant effect of NaCl and curing time on the extraction, and less effect was found with the variation of acid and iron salts. The second stage included column leaching using a solution with 0.5 g/L of Cu+2, 80 g/L of Cl−, 10 g/L of H2SO4, and variable concentrations of ferric and ferrous ions (0 and 2 g/L). The best copper extraction of 80.2% was found considering a pretreatment of 30 days, 25 kg/t of H2SO4, 50 kg/t of NaCl, and a leaching solution concentration described previously with 2 g/L of Fe+2. The results showed the leaching of all copper oxide species and 20% of the copper sulfide species. In addition, there was a reduction in the acid consumption as the resting time increases. Furthermore, to evaluate a possible decrease in time and acid in pretreatment and chloride in leaching, tests including 10 and 25 kg/t of H2SO4 and 1, 15, and 30 days of curing and a diminution of the NaCl concentration to 20 g/L (content from seawater) were executed. The results showed a significant effect on curing time below 15 days. Furthermore, the slight influence of the decrease of acid on copper extraction gives cost reduction opportunities. The diminution of chloride concentration (80 to 20 g/L) in leaching solution decreases the extraction from 79% to 66.5%. Finally, the Mellado leaching kinetic model was successfully implemented.
Highlights
Copper oxide and copper sulfide ores are processed in hydrometallurgical and concentrator plants, respectively
Due to the nature of deposits and the deepening of the pits, there is a depletion of the oxide copper ores and greater presence of sulfide ores [1]
Many authors concluded that chloride media is effective in copper sulfide ore dissolution for many reasons
Summary
Copper oxide and copper sulfide ores are processed in hydrometallurgical and concentrator plants, respectively. On the other hand, according to the Pourbaix diagram, copper sulfides as Chalcopyrite (CuFeS2), Bornite (Cu5FeS4), Chalcocite (Cu2S), and Covellite (CuS) need low pH (less than pH 4) and redox potentials above 0.4 V (SHE) These potential levels can be achieved using oxidants as ferric ions in the leaching solution [16]. In the case of leaching of secondary copper sulfide ores, it was demonstrated that the agglomeration with acid and chloride ions and curing for an extensive period increases the copper extraction with a maximal extraction of 72% considering 50 days of curing. Once the best condition on pretreatment that maximizes the copper extraction is identified, the second set of tests is executed, evaluating the incorporation of ferric ions (0 or 2 g/L) or ferrous ions (0 or 2 g/L) into the leaching solution to continue increasing the copper extraction. A final evaluation of the pretreatment/leaching cycle and acidification is performed
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