At concentrations higher than 0.5 M, the effect starts to be counterproductive by giving a higher loading capacity to the leaching solution and sulfating the remaining copper resulting in a slower copper dissolution rate. However, according to the graph, a high amount of sulfuric acid is detrimental to extraction. Therefore, the presence of sulfuric acid has a positive effect in providing the right environment for chalcopyrite dissolution. The low copper extraction in the absence of sulfuric acid suggests that the added iodide reacts and transforms into a reducing agent according to its dissociation and subsequent oxidation. This system shows extractions of up to 4.7% at the end of the leaching time. In addition to the sulfuric acid systems, the figure shows a leaching system with no acidity and 100 ppm KI. A sample for mineralogical characterization and particle size determination was taken. The solid residues were carefully filtered, washed with distilled water, and dried at 60 ☌ to constant weight. All experiments were performed in triplicate. Redox potential (ORP) and pH were measured throughout the test with a portable Hanna meter (model HI991003). A 10 mL aliquot of the solution was taken periodically during the test for copper analysis using the Atomic Absorption Spectroscopy method (AAS). The pulp was stirred to obtain a homogenous mix using a propeller with a rotation speed of 450 rpm. Before the leaching tests, the concentrate sample was washed with distilled water and acetone (C 3H 6O) with the purpose to remove any flotation reagents left used in the process of concentration. Once the solution reached the desired temperature, 50 g of the solid sample was added to the reactor. Each reactor was loaded with 1 L of leaching solution (sulfuric acid, seawater, iodide potassium or iodate potassium, and sodium chloride) and was sealed with a film to avoid evaporation. The mineral surface was analyzed using SEM/EDS and XRD analyses for the identification of precipitates on the surface, finding porous elemental sulfur and precipitated jarosite.Ĭoncentrate leaching tests were performed in 2 L jacketed glass reactors (See Figure 2). The recovery rate improves at potentials between 600 and 650 mV, while at lower potentials, the copper extraction decreases. Copper extraction reached 45% within the first 96 h, while at 216 h, it reached an extraction of close to 70% copper. As a result, part of the iodide required to oxidize copper tends to sublimate or is associated with other ions producing iodinated compounds such as CuI. An increase in iodide ions improves the leaching kinetics in the chalcopyrite concentrate, observing that it improves copper extraction at low concentrations of 100 ppm KI compared to high concentrations of 5000 ppm KI. The mineral surface was analyzed using SEM/EDS and XRD analyses for the identification of precipitates on the surface, finding porous elemental sulfur and precipitated jarosite. According to the results obtained, adding iodide ions to a medium acid enhances the leaching kinetics in the chalcopyrite concentrate, observing that it improves copper extraction at low concentrations of 100 ppm KI compared to high concentrations of 5000 ppm KI. Parameters such as iodide salt concentration and acidity were evaluated in ranges of 0–5000 ppm and 0–1.0 M, respectively. Leaching tests were carried out in glass reactors stirred at 45 ☌. The main objective of this paper is to evaluate the leaching potential of iodide ions in copper extraction from chalcopyrite concentrate in an acidic seawater medium. One of the main problems in processing chalcopyrite ore with hydrometallurgical methods is its refractoriness, which is due to the formation of a layer that inhibits the contact of the ore with the leaching solution, thus reducing the dissolution rate.
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