Electrometallurgy ‐ Now and in the Future

Free, Michael L.; Moats, Michael S.; Robinson, Tim; Neelameggham, Neale R.; Houlachi, Georges; Ginatta, Marco V.; Creber, D. K.; Holywell, George

doi:10.1002/9781118371350.ch1

Cited by 9 publications

(5 citation statements)

References 11 publications

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“…The formation of anglesite during industrial-scale processing of Pb ores is one of the main factors limiting Pb recovery and increasing the processing cost. For example, the Fluobor process, developed by Doe Run and Engitec Technologies, uses ferric fluoroborate to selectively extract Pb at 80 °C. , The process precipitates anglesite during the H 2 SO 4 addition step, resulting in an extension of the processing aiming to liberate Pb from anglesite. Likewise, the Albion leach processing of Pb–Zn concentrates in ferric sulfate medium produces anglesite and plumbojarosite, which require smelting…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of Surface Passivation during Galena Leaching by Hydrogen Peroxide in Acetate and Citrate Solutions at 25–50 °C

Nikkhou

Xia

Knorsch

et al. 2020

ACS Sustainable Chem. Eng.

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Organic solutions are promising lixiviants for fast and environmentally sustainable Pb extraction from ore minerals at low temperatures. However, engineering of novel leaching flowsheets has been hindered by poor understanding of the leaching mechanism, particularly the formation of surfacepassivating phases. Here, we studied leaching of galena (PbS), the most abundant Pb ore mineral, in citrate and acetate solutions at 25−50 °C. The results show faster and higher Pb extraction in citrate solutions than in acetate solutions. For example, leaching of 53−106 μm galena particles at 35 °C for 2 h achieved 69.3% Pb extraction in a pH 7 citrate solution but only 30.1% in a pH 3 acetate solution. Investigation of solid residues by SEM, EDS, quantitative powder X-ray diffraction, and Raman spectroscopy proved the formation of a porous yet poorly permeable layer of anglesite during acetate leaching by pseudomorphic replacement of galena and subsequent overgrowth, hindering further leaching after 55.6% Pb extraction. In contrast, in citrate solutions, no anglesite was observed, but the formation of an impermeable thin Pb-oxide layer caused surface passivation after 87.1% Pb extraction. Our experimental results and thermodynamic calculations suggest that Pb-citrate complexes [e.g., Pb 2 (C 6 H 5 O 7 ) 2 2− , Pb(C 6 H 5 O 7 ) 2 4− , and Pb(C 6 H 5 O 7 ) − ] are far more effective than Pb-acetate complexes [e.g., Pb(CH 3 COO) + and Pb(CH 3 COO) 2 ] in suppressing the precipitation of anglesite because of the high solubility of Pb-citrate complexes in sulfate-rich solutions. This work provides a scientific basis for developing greener approaches such as in situ leaching and heap leaching for recovering Pb from galena-bearing ores.

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Section: Discussionmentioning

confidence: 99%

Mechanisms of Surface Passivation during Galena Leaching by Hydrogen Peroxide in Acetate and Citrate Solutions at 25–50 °C

Nikkhou

Xia

Knorsch

et al. 2020

ACS Sustainable Chem. Eng.

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“…In the process, lead is based on ferric leaching and electrochemical reduction of galena concentrate in a fluoroboric acid-based solution. Electro-winning is carried out in split cells using stainless steel cathodes and graphite anodes [15]. On the other hand, Buzatu et al, stated that they performed their studies in the production of Pb from wastes containing PbSO4, PbO, and Pb in a NaOH based electrolyte, using stainless steel anodes and cathodes, at a current density of 600 A/m 2 , at an electrolyte temperature of 35 °C [16].…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Reduction of Lead Sulphide in NaCl-KCl and NaCl-KCl-%2Na2S

Kartal¹

2022

Sakarya University Journal of Science

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In this study, the lead production from lead sulfide (PbS) by molten salt electrolysis was investigated under potentiostatic and galvanostatic conditions using NaCl-KCl and NaCl-KCl-2%Na2S electrolytes. Stable cell voltage and current were aimed with the addition of Na2S to the NaCl-KCl electrolyte. Reduction experiments were carried out at constant 700 °C temperature and for 15 min. duration. The current density was set to 250 mA/cm 2 for the galvanostatic reduction experiments. It was observed that there was an increase in cell voltage in both electrolytes due to the decrease in the amount of PbS in galvanostatic experiments. In these experiments, it was determined that the reduction occurred at higher cell voltages in the NaCl-KCl electrolyte compared to the NaCl-KCl-2%Na2S electrolyte. Although the cell voltage was aimed to remain constant with the Na2S addition, the cell voltage decreased slightly compared to the NaCl-KCl electrolyte, but increased with the experiment duration as in the NaCl-KCl electrolyte. Potentiostatic reduction experiments carried out at a constant cell voltage of 3.0 V under the electrolyte decomposition voltage. The morphology of the cathode products was examined by SEM-EDS analysis and, the phases were examined by X-ray diffractometry. Higher current values were obtained in the NaCl-KCl-%2Na2S electrolyte compared to the NaCl-KCl electrolyte. Current variation with electrolysis duration showed similar trends in both electrolytes. According to structural characterization, it was determined that the metallic lead mass did not contain any impurities.

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“…Those impurity ions then gradually form an anode and/or floating slimes, not only possibly entering the copper cathode by electrolyte entrainment but also influencing the migration of copper cations onto the cathode within cells. This can cause problems during processes of copper production including anode passivation, cathode contamination (codeposition with copper or mechanical inclusion), low current efficiency, etc., which, as a result, worsen commercial copper cathode quality and increase operating costs. − However, complete removal of these impurity ions is very difficult. Among those, one of the main challenges is the formation of floating slimes which is believed to be caused by the coexistence of various valences of As and Sb (III and V) in the electrolyte.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Modeling of the Fe(II)–Fe(III)–Cu(II)–H₂SO₄–H₂O Solution and Its Application to Determination of Redox Potential during Copper Electrorefining up to 70 °C

Dong

Wesstrom

Olave

et al. 2021

Ind. Eng. Chem. Res.

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A thermodynamic model of the Fe(II)–Fe(III)–Cu(II)–H2SO4–H2O system is developed and shown to reliably simulate the species distribution in the industrial copper electrorefining electrolyte from 25 to 70 °C. The previously developed model of the Fe(II)–Fe(III)–H2SO4–H2O system under leaching conditions was first evaluated, and it proved that its applicability can be extended to a much higher acid concentration (185 g/L). Cu(II) species were then identified, and their thermodynamic data were collected and assessed for modeling calculations. Results reveal that after addition of a high amount of copper (40–50 g/L), Fe(II) is still distributed as free Fe2+, FeHSO4 +, and FeSO4°; Fe(III) is distributed as free Fe3+, FeSO4 +, FeHSO4 2+, and Fe(SO4)2 –. Cu(II) is dissolved as Cu2+, CuSO4°, and CuHSO4 +. The proposed model was validated by reliable and accurate prediction of the measured redox potential throughout all solution conditions. An expression developed previously to predict the redox potential can still be applied in this work. Analysis of speciation results strongly supports that the redox potential of acidic iron sulfate solutions with such a high acid and copper concentration can still be solely determined by the Fe3+/Fe2+ couple. The pH and effective ionic strength were also obtained and discussed. These findings contribute to further investigation on speciation of other solutions during copper production.

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Electrometallurgy ‐ Now and in the Future

Cited by 9 publications

References 11 publications

Mechanisms of Surface Passivation during Galena Leaching by Hydrogen Peroxide in Acetate and Citrate Solutions at 25–50 °C

Mechanisms of Surface Passivation during Galena Leaching by Hydrogen Peroxide in Acetate and Citrate Solutions at 25–50 °C

Electrochemical Reduction of Lead Sulphide in NaCl-KCl and NaCl-KCl-%2Na2S

Thermodynamic Modeling of the Fe(II)–Fe(III)–Cu(II)–H₂SO₄–H₂O Solution and Its Application to Determination of Redox Potential during Copper Electrorefining up to 70 °C

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Electrometallurgy ‐ Now and in the Future

Cited by 9 publications

References 11 publications

Mechanisms of Surface Passivation during Galena Leaching by Hydrogen Peroxide in Acetate and Citrate Solutions at 25–50 °C

Mechanisms of Surface Passivation during Galena Leaching by Hydrogen Peroxide in Acetate and Citrate Solutions at 25–50 °C

Electrochemical Reduction of Lead Sulphide in NaCl-KCl and NaCl-KCl-%2Na2S

Thermodynamic Modeling of the Fe(II)–Fe(III)–Cu(II)–H2SO4–H2O Solution and Its Application to Determination of Redox Potential during Copper Electrorefining up to 70 °C

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Thermodynamic Modeling of the Fe(II)–Fe(III)–Cu(II)–H₂SO₄–H₂O Solution and Its Application to Determination of Redox Potential during Copper Electrorefining up to 70 °C