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12 pages, 1271 KiB

Open AccessArticle

Melt–Vapor Phase Transition in the Aluminum–Selenium System in Vacuum

by Alina Nitsenko, Valeriy Volodin, Xeniya Linnik, Nurila Burabayeva and Sergey Trebukhov

Metals 2023, 13(7), 1297; https://doi.org/10.3390/met13071297 - 19 Jul 2023

Cited by 4 | Viewed by 730

The boundaries of liquid and vapor coexistence fields at pressures of 101.3 and 0.133 kPa were calculated based on the partial vapor pressure values of the components in the Al-Al₂Se₃ and Al₂Se₃-Se partial systems. The vapor [...] Read more.

The boundaries of liquid and vapor coexistence fields at pressures of 101.3 and 0.133 kPa were calculated based on the partial vapor pressure values of the components in the Al-Al₂Se₃ and Al₂Se₃-Se partial systems. The vapor pressures of the more volatile aluminum selenide and selenium in the above systems were determined by the isothermal version of the boiling-point method. The partial pressures of the fewer volatile components were determined by numerical integration of the Gibbs–Duhem equation. The partial and integral values of the thermodynamic functions of the formation and evaporation of solutions were calculated based on the values of the partial vapor pressure of the system components. Based on the analysis of the complete phase diagram, it was found that the purification of aluminum by vacuum distillation in a single operation can remove aluminum selenide and selenium at an appropriate rate. The distillation of selenium from melts in vacuum in the whole concentration range of the Al₂Se₃-Se system will proceed from the mixture of the solution with Al₂Se_3 cryst., with accumulation of the latter in the distillation residue. Full article

(This article belongs to the Special Issue Separation and Purification of Metals)

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23 pages, 6877 KiB

Open AccessArticle

Effect of Glue, Thiourea, and Chloride on the Electrochemical Reduction in CuSO₄–H₂SO₄ Solutions

by Érika D. Nevárez-Llamas, Eugenia A. Araneda-Hernández, Víctor R. Parra-Sánchez and Eduardo A. Villagrán-Guerra

Metals 2023, 13(5), 891; https://doi.org/10.3390/met13050891 - 05 May 2023

Cited by 1 | Viewed by 1311

Abstract

The effect of glue, thiourea, and chloride on the kinetics of copper reduction in CuSO₄–H₂SO₄ solutions of copper composition, and temperatures like those used in the copper electrorefining plants, were studied. The kinetic study was conducted by determining [...] Read more.

The effect of glue, thiourea, and chloride on the kinetics of copper reduction in CuSO₄–H₂SO₄ solutions of copper composition, and temperatures like those used in the copper electrorefining plants, were studied. The kinetic study was conducted by determining the kinetic parameters

i_{0}

and

β

under the activation control of the Tafel approximation, which is applied to polarization curves obtained via linear voltammetry. The results show that the incorporation of glue and thiourea decreases the exchange current density, while chloride does not significantly affect the kinetic parameters. The data on the fraction of the surface covered by glue and thiourea fitted to the Temkin adsorption isotherm indicate that the mechanism of action during the reduction of copper to low overpotentials is the adsorption of these additives on the electrode surface. The adsorption of additives reduces the cathodic area available for Cu²⁺ adsorption and lateral diffusion of Cu atoms to continue the reduction process and the growth of the crystalline deposit. The kinetic study was complemented with a comprehensive analysis of the effect of the additives on the morphological and textural characteristics of the deposits. The results of this work contribute to the understanding of the mechanisms of the main additives used during the copper electrorefining process. Full article

(This article belongs to the Special Issue Separation and Purification of Metals)

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19 pages, 4572 KiB

Open AccessFeature PaperArticle

Chromatographic Separation of Rare Earth Elements as MGDA Complexes on Anion Exchange Resins

by Santeri Kurkinen, Sami Virolainen and Tuomo Sainio

Metals 2023, 13(3), 600; https://doi.org/10.3390/met13030600 - 16 Mar 2023

Viewed by 1826

Abstract

Chromatographic separation of rare earth elements (REE) as anionic complexes with chelating aminopolycarboxylate ligand methylglycine N,N-diacetate (MGDA) was studied experimentally. A synthetic mixture of La, Nd, and Eu were used to model a REE mixture obtained from processed secondary sources [...] Read more.

Chromatographic separation of rare earth elements (REE) as anionic complexes with chelating aminopolycarboxylate ligand methylglycine N,N-diacetate (MGDA) was studied experimentally. A synthetic mixture of La, Nd, and Eu were used to model a REE mixture obtained from processed secondary sources such as phosphogypsum (PG). In the REE extraction from PG, the REEs can be recovered with MGDA to obtain the REE–MGDA mixture. Three strong base anion exchange resins (Dowex 1X8, IRA-402, and IRA-410) were used as the separation materials. Successful separation of the REEs by elution with dilute HNO₃ and HCl was attributed to differences in the stabilities of the REE–MGDA complexes. The pKa values of the complexes were determined by titration to be 3.81, 3.25, and 2.96 for La, Nd, and Eu, respectively. Fractionation of the ternary La-Nd-Eu mixture (with a 1:1:1 mole ratio) were studied. La was recovered at approximately 80% purity and 80% yield, but strong trade-offs between the yield and the purity of Nd and Eu must be made. Chromatographic separation was found to be an efficient process option, considering its simplicity and the recovery of several product fractions. The initial process design offers a promising starting point for investigating more advanced process configurations for the efficient recovery of pure REE from phosphogypsum. Full article

(This article belongs to the Special Issue Separation and Purification of Metals)

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14 pages, 1859 KiB

Open AccessArticle

Pyrometallurgical Scheme Intended to Process Arsenic-Containing Concentrates with Recovery of Precious Metals

by Valeriy Volodin, Sergey Trebukhov, Alina Nitsenko, Xeniya Linnik, Farkhat Tuleutay, Alexey Trebukhov and Galiya Ruzakhunova

Metals 2023, 13(3), 540; https://doi.org/10.3390/met13030540 - 07 Mar 2023

Cited by 2 | Viewed by 1385

Abstract

The practicability of a pyrometallurgical scheme for raw material processing is established as a result of the analysis of methods intended to dearsenate and process gold-arsenic concentrates as well as equipment for the process execution. The conceptual design of vacuum equipment without forced [...] Read more.

The practicability of a pyrometallurgical scheme for raw material processing is established as a result of the analysis of methods intended to dearsenate and process gold-arsenic concentrates as well as equipment for the process execution. The conceptual design of vacuum equipment without forced movement of the dispersed material in the sublimator and of the reaction zone materials is proposed. In-process tests for the sublimation of arsenic sulfides from gravity and flotation concentrates received from the Bakyrchik deposit were executed at the pilot facility. As a result, it was found that more than 97–99% of arsenic passes into the gas phase and condenses in a sulfide form suitable for compaction by smelting. More than 99.5% of precious metals are concentrated in the sublimation residue. As a result of smelting residue from the sublimation of arsenic sulfides in a cyclone furnace, together with copper concentrates to copper matte, the gold recovery was 93.7–93.9% of the total amount loaded. Silver was 65.7–68% concentrated in copper matte, with a considerable amount in the dust. If the cyclone smelting dust is involved, the recovery rate of gold and silver can be increased to 97–99% and 94–95%, respectively. As a result of crucible smelting, the degree of recovery of gold in matte was 95.4%, with its content in slag being 3.6 g/t. The received matte according to the proposed scheme can be directed to the conversion process by obtaining blister copper, which is subjected to electrolytic refining with the recovery of gold from slimes. Full article

(This article belongs to the Special Issue Separation and Purification of Metals)

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11 pages, 2731 KiB

Open AccessArticle

Static Crystallization, an Alternative Methodology for Synthesis of High-Purity Aluminum

by Michaela Gotenbruck, Danilo C. Curtolo, Semiramis Friedrich, Clemens J. Müller, Nico Rademacher and Bernd Friedrich

Metals 2023, 13(2), 280; https://doi.org/10.3390/met13020280 - 31 Jan 2023

Viewed by 1446

Abstract

Due to its outstanding properties and wide range of applications, high-purity to ultra-high-purity aluminum represents a strategic material for meeting the future challenges of the 21st century. The purification of aluminum towards higher purity levels is usually performed via a combination of three-layer [...] Read more.

Due to its outstanding properties and wide range of applications, high-purity to ultra-high-purity aluminum represents a strategic material for meeting the future challenges of the 21st century. The purification of aluminum towards higher purity levels is usually performed via a combination of three-layer electrolytic refining and fractional crystallization using zone-melting processes. New methods and processes are being researched in the search for more time-saving and less costly options. Metal refining using static crystallization represents one of these new, alternative processes. This work investigated the feasibility of metal refining by means of a static crystallization furnace using aluminum as an example metal. In particular, the effects of the temperature gradient and the cooling rate on the reduction factor of the impurities iron (Fe), silicon (Si), and lead (Pb) were investigated. In addition, the effects of the process parameters on the grain structure formed were investigated, and correlations to the resulting purity level were made. Full article

(This article belongs to the Special Issue Separation and Purification of Metals)

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9 pages, 1329 KiB

Open AccessArticle

On the Distillation Separation of Aluminum–Tellurium System Melts under Equilibrium Condition

by Nurila Burabaeva, Valeriy Volodin, Sergey Trebukhov, Alina Nitsenko and Xeniya Linnik

Metals 2022, 12(12), 2059; https://doi.org/10.3390/met12122059 - 29 Nov 2022

Cited by 1 | Viewed by 1129

Abstract

The problem to purify secondary aluminum raw materials from tellurium can be solved by the distillation method based on phase diagrams with liquid and vapor coexistence fields. Similar diagrams can be generated based on the vapor pressure values of the components. In this [...] Read more.

The problem to purify secondary aluminum raw materials from tellurium can be solved by the distillation method based on phase diagrams with liquid and vapor coexistence fields. Similar diagrams can be generated based on the vapor pressure values of the components. In this regard, the vapor pressure values of tellurium and aluminum telluride were determined by the boiling point method. The aluminum vapor pressure values are found by integration of the Gibbs-Duhem equation. The boundaries of the system vapor-liquid equilibrium fields for the Al-Te system at 101.32 kPa and 6.67 kPa were calculated based on the vapor pressure values of the components. The following conclusion can be made from the consideration of the position of the liquid and vapor coexistence field boundaries under atmospheric pressure and in a vacuum. Aluminum can be quite completely purified from Al₂Te₃ and Te by distillation in a vacuum in one operation at temperatures above 1273 K. Tellurium will be in a complete vapor state under these conditions—above the boiling line in the Al₂Te₃-Te system. Full article

(This article belongs to the Special Issue Separation and Purification of Metals)

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17 pages, 3763 KiB

Open AccessArticle

The Effectiveness of Cooled-Finger and Vacuum Distillation Processes in View of the Removal of Fe, Si and Zn from Aluminium

by Michaela Gotenbruck, Danilo C. Curtolo, Semiramis Friedrich and Bernd Friedrich

Metals 2022, 12(12), 2027; https://doi.org/10.3390/met12122027 - 25 Nov 2022

Viewed by 1735

Abstract

The increasing demand for ultra-high purity aluminum for technological applications has led to the improvement of refining methods in recent decades. To achieve ultra-purity levels (>5N), the common industrial way is to firstly purify aluminum from 2N8 up to 4N8 via three-layer electrolysis, [...] Read more.

The increasing demand for ultra-high purity aluminum for technological applications has led to the improvement of refining methods in recent decades. To achieve ultra-purity levels (>5N), the common industrial way is to firstly purify aluminum from 2N8 up to 4N8 via three-layer electrolysis, followed by fractional crystallization (usually zone melting). Since both of these methods are very cost- and time-intensive, this paper aims at providing other alternatives of purification. For this purpose, here, the purification of some selected impurities through cooled-finger fractional crystallization method and vacuum distillation have been the focus of this investigation. Both processes are more environmentally friendly than three-layer electrolysis and require less time than zone melting. In this paper, both methods were explored for the aluminum purification. Moreover, the effect of process parameters on the purification efficiency of iron, zinc, and silicon has been investigated. At the end, the effectiveness of the two processes was compared and advantages and disadvantages were summarized. The results showed that the cooling finger process effectively removed iron and silicon impurities, but the removal efficiency of zinc was low. The vacuum distillation process successfully removes zinc in the first stage of distillation. Iron and silicon removal requires additional distillation stages to achieve lower impurity levels. Full article

(This article belongs to the Special Issue Separation and Purification of Metals)

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Review

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29 pages, 8330 KiB

Open AccessReview

A Critical Review on the Removal and Recovery of Hazardous Cd from Cd-Containing Secondary Resources in Cu-Pb-Zn Smelting Processes

by Guihong Han, Jingwen Wang, Hu Sun, Bingbing Liu and Yanfang Huang

Metals 2022, 12(11), 1846; https://doi.org/10.3390/met12111846 - 28 Oct 2022

Cited by 5 | Viewed by 3417

Abstract

Due to the advancement of industrialization and the development of the metal smelting industry, cadmium (Cd), as a highly toxic heavy metal element, is discharged into the natural environment in the form of dust, slag, and waste solutions during the Cu-Pb-Zn smelting process, [...] Read more.

Due to the advancement of industrialization and the development of the metal smelting industry, cadmium (Cd), as a highly toxic heavy metal element, is discharged into the natural environment in the form of dust, slag, and waste solutions during the Cu-Pb-Zn smelting process, causing great harm to the soil, water environment, and human health. Meanwhile, Cd is a key component of Ni-Cd batteries and CdTe semiconductor materials. The removal and recovery of Cd from the Cu-Pb-Zn smelting process faces a dual concern with respect to resource recycling and environmental protection. This paper briefly introduces the Cd-containing secondary resources produced in the Cu-Pb-Zn smelting process, systematically reviews the recovery methods of Cd from dust, slag and waste solutions, and compares the technical principles, process parameters, separation efficiency, advantages and disadvantages, and application requirements. In addition, a new route to treat Cd-containing solutions via the foam extraction method was proposed, which has the advantages of a short reaction time, large handling capacity, high removal efficiency, and simple operation equipment, showing superior application prospects, especially for industrial bulk waste solutions with ultralow concentrations. Full article

(This article belongs to the Special Issue Separation and Purification of Metals)

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