In this study, the surface optimization methodology was used to assess the effect of three independent variables—time, particle size and sulfuric acid concentration—on Mn extraction from marine nodules during leaching with H2SO4 in the presence of foundry slag. The effect of the MnO2/Fe ratio and particle size (MnO2) was also investigated. The maximum Mn extraction rate was obtained when a MnO2 to Fe molar ratio of 0.5, 1 M of H2SO4, −320 + 400 Tyler mesh (−47 + 38 μm) nodule particle size and a leaching time of 30 min were used.

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Chalcocite is the most important and abundant secondary copper ore in the world with a rapid dissolution of copper in an acid-chloride environment. In this investigation, the methodology of surface optimization will be applied to evaluate the effect of three independent variables (time, concentration of sulfuric acid and chloride concentration) in the leaching of pure chalcocite to extract the copper with the objective of obtaining a quadratic model that allows us to predict the extraction of copper. The kinetics of copper dissolution in regard to the function of temperature is also analyzed. An ANOVA indicates that the linear variables with the greatest influence are time and the chloride concentration. Also, the concentration of chloride-time exerts a significant synergic effect in the quadratic model. The ANOVA indicates that the quadratic model is representative and the R2 value of 0.92 is valid. The highest copper extraction (67.75%) was obtained at 48 h leaching under conditions of 2 mol/L H2SO4 and 100 g/L chloride. The XRD analysis shows the formation of a stable and non-polluting residue; such as elemental sulfur (S0). This residue was obtained in a leaching time of 4 h at room temperature under conditions of 0.5 mol/L H2SO4 and 50 g/L Cl−.

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The unique properties of ionic liquids (ILs) drive the growing number of novel applications in different industries. The main features of ILs are high thermal stability, recyclability, low flash point, and low vapor pressure. This study investigated pure chalcopyrite dissolution in the presence of the ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate, [BMIm]HSO4, and a bromide-like complexing agent. The proposed system was compared with acid leaching in sulfate media with the addition of chloride and bromide ions. The results demonstrated that the use of ionic liquid and bromide ions improved the chalcopyrite leaching performance. The best operational conditions were at a temperature of 90 °C, with an ionic liquid concentration of 20% and 100 g/L of bromide.

The effect of NaCl on the leaching of white metal from a Teniente Converter was investigated in NaCl-H2SO4 media under environmental conditions. The copper dissolution from white metal was studied using ferric ions in the range of 1–10 g/L, NaCl in the range of 30–210 g/L, and sulfuric acid in the range of 10–50 g/L. The test without NaCl produced a dissolution of 55%; through the addition of NaCl, the dissolution increased to nearly 90%. The effect of sulfuric acid on the copper dissolution was not significant in the studied range, as the excess sulfuric acid simply increased the iron precipitation. The positive effect of NaCl seems to be related to the action of chloro-complex oxidizing agents in relation to the Cu+2/Cu+ couple. A simplified two-stage mechanism is proposed for the leaching of white metal. In the first stage, the white metal produces covellite and Cu2+, and in the second stage it produces elemental sulfur and Cu2+. The first stage is very rapidly compared to the second stage.

BACKGROUND: This work is focused on the removal of Cu(II) ions from aqueous solutions by means of different hydrophobic imidazolium-based ionic liquids containing 1,1,1-trifluoro-2,4-pentanedione (TFA) as extractant and the subsequent extraction of the metal complexes formed in the IL by means of supercritical fluid extraction. RESULTS: Solutions containing between 250 and 500 mg L -1 of Cu(II) ions were contacted with [bmim][PF 6 ], [hmim][PF 6 ] and [bmim][Tf2 N] containing TFA. After liquid-liquid extraction, both phases were analysed, verifying the formation of neutral complex Cu(TFA) 2 as the predominant extraction mechanism in [bmim][PF 6 ] and [bmim][Tf 2 N]. Meanwhile, the extraction of Cu(II) in [bmim][PF 6 ] was strongly influenced by the direct interaction between the metal ion and the IL. ILs used in L-L extractions were regenerated using supercritical CO 2 at 18 MPa and 40 ∘ C. [bmim][Tf 2 N] showed the highest accumulative extraction percentage (≈ 80%) after sequential loads of Cu(II) ions. CONCLUSION: From these tests, [bmim][Tf 2 N] was the solvent that showed the best performance in terms of accumulative extraction and recycling capacity in sequential extraction cycles mediated by regeneration with supercritical CO 2 . This study demonstrates that this process could be considered an alternative separation technique for metal ions using green solvents, and with extractant requirements lower than in conventional solvent extraction operations.