Effects of Fe+2 and Fe+3 in Pretreatment and Leaching on a Mixed Copper Ore in Chloride Media

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.

Effect of Pretreatment on a Copper Concentrate with High Arsenic Content

“…This highlights the significant influence of sodium chloride in achieving higher copper extractions, particularly when the sulfuric acid addition is insufficient to satisfy sulfation reactions. These results are difficult to compare with other published studies [7,8,23], as most studies focus on the effect of chloride ion addition under specific pretreatment conditions, without considering the synergy with acid levels. However, this influence is related to proton activity.…”

“…Researchers Olvera and Dixon [5] propose hydrometallurgy as a treatment alternative since it keeps arsenic species stable in solution. Additionally, authors such as Cerda et al [6], Hernández et al [7], Taboada et al [8], Liu et al [9], and Vargas et al [10] suggest that hydrometallurgical plants could harness new capabilities to process sulfide minerals as a result of the depletion of oxidized minerals. According to the Chilean Copper Commission (Cochilco), copper production through hydrometallurgical processes represented 25.1% of the total in the year 2021, and this figure is projected to decrease to 6.3% by the year 2033 [2].…”

“…Authors such as Cerda et al [6], Hernández et al [7], Taboada et al [8], and Quezada et al [16,17] propose a pretreatment (acid curing) before the leaching stage. This pretreatment involves the sulfation of the mineral through the addition of sulfuric acid and other agents under investigation, such as sodium chloride and ferric salts.…”

Gangues and Clays Minerals as Rate-Limiting Factors in Copper Heap Leaching: A Review

“…Among the copper minerals on the planet, the vast majority correspond to sulfide ores [3]. Within these copper minerals, chalcopyrite stands out as the most abundant, representing 70% of all minerals that contain copper in the Earth's crust [4][5][6][7]. Copper is recovered from these minerals mainly through flotation, followed by pyrometallurgical processing, representing 80-85% of world's copper production [8,9].…”