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Copper leaching presents an environmentally friendly alternative to traditional sulfide ore processing methods. This study investigates an efficient leaching process for copper concentrate, utilizing a solution of sulfuric acid (H2SO4) and potassium iodide (KI) in a chloride medium (NaCl), enhanced by hydrogen peroxide (H2O2) at room temperature. A significant aspect of this research was optimizing the KI concentration to minimize iodide sublimation into iodine gas (I2). Through the experimental design, the optimal dosages of reagents were determined, leading to maximized copper extraction of approximately 27% in 45 min of testing at room temperature. The results showed that it is possible to obtain a suitable pregnant leach solution (PLS) (i.e., in the range of 3 to 8 g/L of Cu) for treatment in available copper solvent extraction (SX) plants with a cost of less than 4.5 USD/t Cu, according to the economic analysis carried out. The results of this study determine the most effective operational conditions for leaching and ensure a suitable PLS for SX plants in a cost-effective and environmentally friendly manner. This approach could significantly contribute to more sustainable practices in the mining and processing of copper ores. [ABSTRACT FROM AUTHOR]

This article presents the results on speciation of ferric iron generated by the dissolution of chemical reagent hydromolysite (ferric chloride hexahydrate, FeCl:6HO) in water at 298.15 K, 313.15 K, and 333.15 K (25 °C, 40 °C, and 60 °C). Experiments were performed with a thermoregulated system up to the equilibrium point, as manifested by solution pH. Solution samples were analyzed in terms of concentration, pH, and electrical conductivity. Measurements of density and refractive index were obtained at different temperatures and iron concentrations. A decrease of pH was observed with the increase in the amount of dissolved iron, indicating that ferric chloride is a strong electrolyte that reacts readily with water. Experimental results were modeled using the hydrogeochemical code PHREEQC in order to obtain solution speciation. Cations and neutral and anion complexes were simultaneously present in the system at the studied conditions according to model simulations, where dominant species included Cl, FeCl, FeCl , FeOHCl, and H. A decrease in the concentration of Cl and Fe ions took place with increasing temperature due to the association of Fe-Cl species. Standard equilibrium constants for the formation of FeOHCl obtained in this study were log $$ K_{f}^{0} $$ = −0.8 ± 0.01 at 298.15 K (25 °C), −0.94 ± 0.02 at 313.15 K (40 °C), and −1.03 ± 0.01 at 333.15 K (60 °C). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: The densities and viscosities of unsaturated solutions of sodium perchlorate+poly(ethylene glycol)+water were experimentally measured at temperatures of 288.15, 298.15 and 308.15K. The solution concentrations of poly(ethylene glycol) with an average molecular weight of 4000 ranged from 0.25 to 33.91 (mass%) and from 10.12 to 37 (mass%) of NaClO4. The electrolyte and polymer non-random two liquid models were extended for representing of the excess molar volume and the dynamic viscosity of the above system. At these specific temperatures, the model correlations compared favorably with the experimental data for both the density and the viscosity. [Copyright &y& Elsevier]

Abstract: The cloud-point (CP) temperatures and phase separation of {H2O+poly(ethylene glycol)+NaNO3} ternary system is studied by the turbidimetry method using a reaction calorimeter. The phase separation was also observed by visual inspection. Differences between the CP measured using the turbidimetry method and visual inspection, was up ±0.5K. The Flory–Huggins model with a temperature and concentration-dependent interaction parameter was employed to correlate the phase diagram of the system. As a result of the correlation an average absolute deviation of 0.002 is obtained. [Copyright &y& Elsevier]

Abstract: The objective of the present work is to represent the solid–liquid equilibrium of potassium sulfate in diverse water+organic solvent mixtures. This representation is carried out between 288.15 and 318.15K in the following solvent mixtures: water+1-propanol, water+methanol, water+ethanol and water+acetone. The experimental solubility data of the potassium sulfate in the diverse mixed solvents were obtained from literature, and the thermodynamic representation of the phase equilibrium is based on a simple methodology reported in the literature. Good agreements are observed between the results obtained in this work and the experimental solubility data of K2SO4 in the different solvent mixtures. Since these systems present a notable decrease in solubility owing to the effect of the cosolvent, making them potentially suitable for separating potassium sulfate by drowning-out the crystallization process, the amounts of salt precipitated, as a function of the weight percent of cosolvent, was calculated for the four systems analyzed. In addition, the optimum yield was estimated as function of the mass fraction of 1-propanol for the K2SO4 +water+1-propanol system. [Copyright &y& Elsevier]

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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. [ABSTRACT FROM AUTHOR]

The leaching of copper from industrial copper ore with 4.8 wt % chalcopyrite by acidified nitrate with seawater based media was investigated. Water quality (pure water and seawater), temperature (25–70 °C), reagent concentration, and nitrate type (sodium and potassium) were studied variables. Leaching conditions were: 100 g ore/1 L solution; P80 of 62.5 µm; 400 rpm and leaching time, varying between 3 and 7 days. Nitrates in sulfuric acid are known to be good oxidants for sulfide ores. This study showed that up to 80 wt % copper could be extracted at 45 °C in 7 days. In the absence of nitrate, under the same leaching conditions, only a 28 wt % copper extraction was achievable. The extraction rate increased to 97.2 wt % when leach temperature was increased to 70 °C in nitrate-chloride-acid media. The presence of chloride ions also increased the copper extraction rate. The copper extraction achieved in seawater systems were higher than in water systems under the same leaching conditions (increased by an average of 18 wt %). This effect can be attributable to the contribution of chloride that increases proton (H+) activity. [ABSTRACT FROM AUTHOR]

Abstract: The activity coefficients of sodium chloride in the NaCl+NaBF4 +H2O ternary system were experimentally determined at 298.15K, at ionic strengths of 0.3. 0.5, 1, 2 and 3molkg−1 from emf from the bi-ISE cell without liquid junction: The activity coefficients were fit to the Harned, Scatchard, Pitzer and Lim-HOLL models and compared to those of similar systems such as NaCl+NaClO4 +H2O and NaCl+NaNO3 +H2O. Other related magnitudes, such as the activity coefficients in trace quantities, osmotic coefficients, activity of water, and change in excess Gibbs energy of mixing, were evaluated and discussed in terms of ion–ion and ion–solvent interactions. [Copyright &y& Elsevier]