Effect of Pretreatment on Leaching Primary Copper Sulfide in Acid-Chloride Media

Abstract

Abstract:The aim of this study was to improve the dissolution of copper sulfide ore composed mainly of chalcopyrite (1.21 wt %) and bornite (0.54 wt %) using a pretreatment before leaching. The effect of the pretreatment on copper sulfide dissolution was investigated using different types of leaching. Three sets of experimental tests were performed (flask, reactor and mini-column). Using experimental design, three operational variables in the ore pretreatment were evaluated: chloride concentration (20, 50 and 90 kg/t), repose time (7, 20 and 40 days) and repose temperature (20 and 50 • C). A maximum of 93% copper dissolution was obtained when the ore was treated with 90 kg Cl − /t ore, 40 d of repose time and 50 • C in flask leaching. Without any ore pretreatment, 53% copper dissolution was achieved. Using reactor leaching, an 85% copper dissolution was obtained using pretreatment stage. Without this pretreatment, only 55% copper dissolution was obtained. The final test, which involved leaching a pretreated ore in a mini-column at room temperature, yielded 49% copper dissolution. The data showed that repose time and temperature were the most important variables affecting copper extraction in the pretreatment stage. This study indicates that pretreatment has a positive effect on copper dissolution from primary copper sulfide ore in an acid-chloride medium. It also provides a feasible alternative for treating primary copper sulfide ores at the industrial level.

Accelerating Copper Leaching from Sulfide Ores in Acid-Nitrate-Chloride Media Using Agglomeration and Curing as Pretreatment

“…This is because the mineral is exposed to a high ionic charge provided by sodium nitrate, sodium chloride and sulfuric acid, which, along with a low amount of water, allow dissolution reactions to occur rapidly. This concurs with Cerda et al [48], Velásquez-Yévenes and Quezada-Reyes [21], and Velásquez-Yévenes et al [51] who found that a higher extraction was obtained with a longer repose period.…”

“…The final pH levels in all the tests were in the range of 2.2 to 3.3, which indicates complete consumption of the aggregate acid in the pretreatment. Redox potential values ranged between 637 and 792 mV (vs SHE), which were higher than the values reported by Cerda et al [48]. This is attributed to the presence of nitrate, which has a high redox potential.…”

“…Dissolution reactions are more rapid with higher temperatures because less energy is necessary to activate dissolution and to break molecular bonds and thus dissolve mineralogical species in contact with the leaching agents [48]. Table 7 shows the main proposed reactions that can occur during agglomeration and curing.…”

“…Curing also solubilizes iron, contributing the ferric ions necessary to dissolve sulfides and inhibit the formation of colloidal silica to minimize silica passing to the leaching solutions [45]. Cerda et al [48] studied the effect of a pretreatment stage at the laboratory level on dissolving a copper sulfide ore in a chloride-acid medium, and obtained a copper extraction of 93% leaching ore pretreated with 90 kg Cl − /ton of ore and 40 days of repose at 50 • C. A copper extraction of only 55% can be achieved without pretreatment, indicating the significant effect of the pretreatment stage. Bahamonde et al [49] determined the positive effect of pretreating bornite and chalcopyrite in acid-chloride media to extract copper from these minerals.…”

Reducing-Effect of Chloride for the Dissolution of Black Copper

“…On the other hand, pre-treatment processes that involve agglomeration and curing stages have shown positive results to improve mineral reaction rates [20,21]. In the study conducted by Bahamonde et al [22], pre-treatment with sodium chloride and sulfuric acid was carried out to enhance copper extractions in a concentrate formed mainly by bornite and chalcopyrite.…”