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14 pages, 6643 KiB

Open AccessFeature PaperArticle

Utilization of Galvanizing Flue Dust Residue: A Sustainable Approach towards Complete Material Recycling

by Jana Pirošková, Jakub Klimko, Silvia Ružičková, Martina Laubertová, Vladimír Marcinov, Erika Múdra, Marek Vojtko and Dušan Oráč

Metals 2024, 14(3), 253; https://0-doi-org.brum.beds.ac.uk/10.3390/met14030253 - 20 Feb 2024

Viewed by 834

Abstract

During hot-dip galvanization, wastes such as bottom dross, zinc ash, spent pre-treatment solutions, and galvanizing flue dust (GFD) are generated. In scientific publications, research devoted to GFD waste recycling is absent, and companies generating this waste require a solution to this complex problem. [...] Read more.

During hot-dip galvanization, wastes such as bottom dross, zinc ash, spent pre-treatment solutions, and galvanizing flue dust (GFD) are generated. In scientific publications, research devoted to GFD waste recycling is absent, and companies generating this waste require a solution to this complex problem. GFD is often landfilled in hazardous waste landfills. However, it is possible to process this waste hydrometallurgically, where GFD is first leached, the solution is refined, and finally, zinc metal is obtained by electrowinning. During specific environmentally friendly leaching, not all solid GFD is dissolved, and the aim of this study is to process the remaining solid GFD residue. The analysis shows that the GFD residue material mainly contains zinc (42.46%) in the form of oxides, but there is also a small amount of polluting elements such as Al, Fe, and Pb. This study examines the leaching of the samples in HCl and H₂SO₄ under different conditions with the aim of obtaining a solution with a high concentration and high leaching efficiency of zinc. The L/S ratio of 3, 4 M H₂SO_4, and ambient temperature proved to be optimal for the leaching of the GFD residue, where 96.24% of zinc was leached out, which represents a zinc concentration of 136.532 g/L. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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18 pages, 19520 KiB

Open AccessArticle

Enhanced Coal Fly Ash Desilication Using Atmospheric NaOH Leaching with Simultaneous Magnetic Separation

by Andrei Shoppert, Dmitry Valeev, Irina Loginova, Leonid Chaikin and Jinhe Pan

Metals 2023, 13(10), 1647; https://0-doi-org.brum.beds.ac.uk/10.3390/met13101647 - 25 Sep 2023

Cited by 1 | Viewed by 1174

Abstract

Coal fly ash (CFA) is a technogenic waste formed during coal combustion in thermal power plants (TPPs). The extraction of valuable components from CFA is complicated by the presence of a large amount of amorphous glassy mass and iron. Herein, a novel method [...] Read more.

Coal fly ash (CFA) is a technogenic waste formed during coal combustion in thermal power plants (TPPs). The extraction of valuable components from CFA is complicated by the presence of a large amount of amorphous glassy mass and iron. Herein, a novel method of CFA desilication with complete extraction of the amorphous glassy mass without desilication product (DSP) precipitation and simultaneous magnetic fraction recovery in one stage is presented. The Fe recovery in the magnetic fraction using the proposed method was significantly improved from 52% to 68%. After conventional wet magnetic separation, followed by the proposed method for desilication and magnetic fraction separation, the Fe recovery was increased to 73.8%. Because of the absence of DSP precipitation, the Na₂O content in the solid residue after desilication was lower than 1 wt.%. The simultaneous desilication and magnetic separation of magnetite was achieved by installing a belt of permanent magnets on the outer surface of the reactor, where the CFA was leached by the highly concentrated NaOH solution. The effects of different parameters on the extraction of Si, Al, and Fe from the raw CFA were elucidated by varying the liquid-to-solid ratio (L:S ratio) from 5 to 10, the temperature from 100 to 120 °C, the leaching time from 10 to 30 min, and the particle size from −50 µm to −73 µm. The optimal leaching parameters were determined to be temperature = 110 °C, L:S ratio = 7.5, and leaching time = 20 min. The extraction of Si and Fe under these conditions was higher than 66 and 73%, respectively. The Al extraction was lower than 10%. The solid residue of NaOH leaching and the magnetic fraction were examined by X-ray diffraction, X-ray fluorescence spectrometry, vibrating sample magnetometry, scanning electron microscopy with energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller, and laser diffraction analyses. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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27 pages, 10131 KiB

Open AccessFeature PaperArticle

Novel Method of Bauxite Treatment Using Electroreductive Bayer Process

by Andrei Shoppert, Dmitry Valeev and Irina Loginova

Metals 2023, 13(9), 1502; https://0-doi-org.brum.beds.ac.uk/10.3390/met13091502 - 22 Aug 2023

Cited by 1 | Viewed by 1386

Abstract

Reductive leaching in the Bayer cycle using iron (2+) allows for Al extraction to be significantly increased through the magnetization of Al-goethite and Al-hematite. However, the use of expensive iron (2+) salts or iron powder as a source of iron (2+) leads to [...] Read more.

Reductive leaching in the Bayer cycle using iron (2+) allows for Al extraction to be significantly increased through the magnetization of Al-goethite and Al-hematite. However, the use of expensive iron (2+) salts or iron powder as a source of iron (2+) leads to a significant increase in production costs. In this work, the feasibility of a new method, the reductive leaching of bauxite using an electrolysis process, was investigated. The reduction of iron minerals of boehmitic bauxite in both the Bayer solution and purely alkaline solutions was carried out. Experiments were performed using a plate cathode and a bauxite suspension in an alkaline solution, as well as using a bulk cathode with a stainless-steel mesh at the bottom of a cell as the current supply. During the electrolysis process, the potential of the cathode relative to the reference electrode was measured as a function of the current at different concentrations of solid (100–300 g L⁻¹) and suspension temperatures (95–120 °C). It was shown that the current efficiency using the suspension and plate cathode with the predominant deposition of Fe did not exceed 50% even with the addition of magnetite to increase the contact of the solid phase with the current supply. With the use of a bulk cathode, the reduction of iron minerals led predominantly to the formation of magnetite with the efficiency of using the electric current at more than 80%. As a result of the preliminary desilication and electroreduction, it was possible to extract more than 98% of Al from bauxite and to increase the iron content in the bauxite residue to 57–58%. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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14 pages, 4531 KiB

Open AccessArticle

Phase Transformations and Tellurium Recovery from Technical Copper Telluride by Oxidative-Distillate Roasting at 0.67 kPa

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

Metals 2022, 12(10), 1774; https://0-doi-org.brum.beds.ac.uk/10.3390/met12101774 - 21 Oct 2022

Cited by 1 | Viewed by 1654

Abstract

This paper presents the results of a study of phase transformations occurring in copper-telluride by-products during its processing of oxidation-distillate roasting at low pressure. The results show that copper telluride is oxidized through intermediate compounds to the most stable tellurate (Cu₃TeO [...] Read more.

This paper presents the results of a study of phase transformations occurring in copper-telluride by-products during its processing of oxidation-distillate roasting at low pressure. The results show that copper telluride is oxidized through intermediate compounds to the most stable tellurate (Cu₃TeO₆) at low temperatures. The increase in the roasting temperature above 900 °C and the presence of an oxidizer favor the copper orthotellurate decomposition. Thus, the tellurium extraction rate is 90–93% at a temperature of 1000 °C, the oxidant flow rate is 2.2 × 10⁻² m³/m²·s, and the roasting time is 60–90 min. One of the decomposition products is copper oxide alloy, which is the basis of the residue. The second product is tellurium in oxide form, which evaporates and then condenses in the cold zone of the condenser in crystalline form. The main constituent phase of the condensate is tellurium oxide (TeO₂), which can be further processed during one operation to elemental chalcogen by thermal reduction or electrolytic method. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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15 pages, 8768 KiB

Open AccessFeature PaperArticle

Effect of Al Dross Addition on Temperature Improvements in Molten Steel by Blowing Dry Air

by Sun-Joong Kim

Metals 2022, 12(7), 1170; https://0-doi-org.brum.beds.ac.uk/10.3390/met12071170 - 9 Jul 2022

Cited by 1 | Viewed by 1480

Abstract

The CO₂ emissions of electric arc furnaces (EAFs) can be reduced by decreasing the electrical energy consumed in the melting of iron scraps by utilizing chemical energy. In general, the chemical energy efficiency of the EAF process can be improved using oxidation [...] Read more.

The CO₂ emissions of electric arc furnaces (EAFs) can be reduced by decreasing the electrical energy consumed in the melting of iron scraps by utilizing chemical energy. In general, the chemical energy efficiency of the EAF process can be improved using oxidation reaction heat and carbon combustion. When carbon is added to molten steel, it is not completely dissolved because of its high melting point, and it floats to the slag layer, owing to its low density. Al dross is a byproduct of aluminum smelting, and it contains over 27 mass% metallic aluminum. As the exothermic heat of aluminum oxidation is larger than that of carbon oxidation, the Al dross is a useful source of exothermic heat in the EAF process. In this study, to utilize the mixtures of cokes and Al dross as chemical energy sources in the EAF process, we investigated the dissolution concentrations, dissolution ratios, and dissolution rate constants of carbon and aluminum in molten steel. The improvement in the molten steel temperature was investigated by blowing dry air into the melt after the dissolution of the mixtures of cokes and Al dross. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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16 pages, 3309 KiB

Open AccessArticle

A Study on the Wet Process Conditions That Affect the Selective Recovery of Si from Photovoltaic Cells by Using the Cavitation Effect

by Jei-Pil Wang, Dong-Hun Lee, Min-Seok Go and Eun-Kyu So

Metals 2022, 12(2), 222; https://0-doi-org.brum.beds.ac.uk/10.3390/met12020222 - 25 Jan 2022

Cited by 8 | Viewed by 1874

Abstract

In this research, a study to selectively recover Si from end-of-life photovoltaic cells by using acid solutions (HNO₃ and HCl) and the cavitation effect of an ultrasonic cleaner was carried out. To selectively recover Si from an end-of-life photovoltaic cell, after a [...] Read more.

In this research, a study to selectively recover Si from end-of-life photovoltaic cells by using acid solutions (HNO₃ and HCl) and the cavitation effect of an ultrasonic cleaner was carried out. To selectively recover Si from an end-of-life photovoltaic cell, after a leaching process was conducted by using an acid solution, the photovoltaic cell that had completed the reaction was cleaned with distilled water and dried in a drying oven (100 °C) for 24 h. The experiment was conducted with acid solution concentration, reaction temperature, reaction time, and ultrasonic intensity as variables. In the results of the experiment, the optimal process was determined to be a concentration of 3M, a reaction temperature of 60 °C, a reaction time of 90 min, and an ultrasonic intensity of 150 W when using the HNO₃ solution and a concentration of 3M, a reaction temperature of 60 °C, a reaction time of 120 min, and an ultrasonic intensity of 150 W when using the HCl solution. At this time, Si purity was 99.78% for HNO₃ and 99.85% for HCl and the Si recovery rate was 98.9% for HNO₃ and 99.24% for HCl. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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12 pages, 6170 KiB

Open AccessArticle

Separating Silver from Tin Silver Alloy Residue: Effect of Agitation Rate

by Juliette Confiance Kabatesi and Jei-Pil Wang

Metals 2022, 12(2), 177; https://0-doi-org.brum.beds.ac.uk/10.3390/met12020177 - 19 Jan 2022

Cited by 2 | Viewed by 2997

Abstract

In this paper, research on the effects of agitation rate for desilvering tin silver alloy residue by using pyrometallurgy was carried out. SnAg alloy residue with 92 wt.% tin and 3.56 wt.% silver was used in this study, and 99.999 wt.% zinc was [...] Read more.

In this paper, research on the effects of agitation rate for desilvering tin silver alloy residue by using pyrometallurgy was carried out. SnAg alloy residue with 92 wt.% tin and 3.56 wt.% silver was used in this study, and 99.999 wt.% zinc was added as metal solvent. Residues were melted to a temperature of 400 °C for enriching tin silver alloy. The obtained tin silver alloy was melted in a temperature range of 450 °C to 500 °C by adding zinc to evaluate zinc dissolution. The obtained tin silver zinc was agitated at different agitation rates for 20 min at a temperature of 480 °C, then cooled down while stirring to an eutectic point of tin zinc alloy (198.9 °C) to remove silver zinc dross. X-ray Fluorescent-1800 (XRF-1800) and Field Emission Scanning Electron Microscopy Energy Dispersive Spectroscopy (FE-SEM-EDS) analyses were performed in this research. Different factors including holding time, zinc dissolution, agitation time and agitation rate were evaluated. The results revealed that an agitation rate of 600 RPM, 25% Zn and 60 min at a temperature of 198.9 °C were efficient. Zinc silver was removed as dross every 20 min to get 92% silver separation efficiency, and the use of supergravity centrifuge is highly recommended to get best separation efficiency. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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18 pages, 6750 KiB

Open AccessArticle

Hydrometallurgical Recycling of Copper Anode Furnace Dust for a Complete Recovery of Metal Values

by Dušan Oráč, Jakub Klimko, Dušan Klein, Jana Pirošková, Pavol Liptai, Tomáš Vindt and Andrea Miškufová

Metals 2022, 12(1), 36; https://0-doi-org.brum.beds.ac.uk/10.3390/met12010036 - 24 Dec 2021

Cited by 7 | Viewed by 3158

Abstract

Copper anode furnace dust is waste by-product of secondary copper production containing zinc, lead, copper, tin, iron and many other elements. Hydrometallurgical Copper Anode Furnace dust recycling method was studied theoretically by thermodynamic calculations and the proposed method was verified experimentally on a [...] Read more.

Copper anode furnace dust is waste by-product of secondary copper production containing zinc, lead, copper, tin, iron and many other elements. Hydrometallurgical Copper Anode Furnace dust recycling method was studied theoretically by thermodynamic calculations and the proposed method was verified experimentally on a laboratory scale. The optimum condition for leaching of zinc from dust was identified to be an ambient leaching temperature, a liquid/solid ratio of 10 and H₂SO₄ concentration of 1 mol/L. A maximum of 98.85% of zinc was leached under the optimum experimental conditions. In the leaching step, 99.7% of lead in the form of insoluble PbSO₄ was separated from the other leached metals. Solution refining was done by combination of pH adjustment and zinc powder cementation. Tin was precipitated from solution by pH adjustment to 3. Iron was precipitated out of solution after pH adjustment to 4 with efficiency 98.54%. Copper was selectively cemented out of solution (99.96%) by zinc powder. Zinc was precipitated out of solution by addition of Na₂CO₃ with efficiency of 97.31%. ZnO as final product was obtained by calcination of zinc carbonates. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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12 pages, 2806 KiB

Open AccessArticle

The Recovery of Metallic Tin from an Industrial Tin-Bearing By-Product Containing Na₂SO₄ by Reduction Smelting Process

by Jongshin Chang and Hosang Sohn

Metals 2021, 11(11), 1697; https://0-doi-org.brum.beds.ac.uk/10.3390/met11111697 - 25 Oct 2021

Cited by 1 | Viewed by 2467

Abstract

Tin was recovered in metal from an industrial tin-bearing byproduct containing Na₂SO₄ by carbothermic reduction smelting, and the effects of basicity (Na₂O/SiO₂), temperature, and reaction time on the recovery of tin were studied. Na₂SO [...] Read more.

Tin was recovered in metal from an industrial tin-bearing byproduct containing Na₂SO₄ by carbothermic reduction smelting, and the effects of basicity (Na₂O/SiO₂), temperature, and reaction time on the recovery of tin were studied. Na₂SO₄ was reduced by carbon and formed into sodium silicate slag (Na₂O–SiO₂) in the presence of SiO₂. Tin content in slag decreased with the increase of Na₂O/SiO₂ ratio in slag, temperature, and reaction time, but the recovery of tin was affected by volatilization of tin in high temperature and high silica region of basicity. In this study, the maximum recovery rate of tin was 94.8% at the experimental condition of 1200 °C, 2 h, and 0.55 of Na₂O/SiO₂ ratio. The major impurities in produced metal were Bi, Pb, Cu, Fe, and most of Bi, Pb, Cu were distributed to the metal phase, but the distribution of Fe was closely related to basicity. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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11 pages, 2783 KiB

Open AccessArticle

Separation of Sn, Sb, Bi, and Cu from Tin Anode Slime by Solvent Extraction and Chemical Precipitation

by Wei-Sheng Chen, Shota Mesaki and Cheng-Han Lee

Metals 2021, 11(3), 515; https://0-doi-org.brum.beds.ac.uk/10.3390/met11030515 - 21 Mar 2021

Cited by 1 | Viewed by 2904

Abstract

Tin anode slime is a by-product of the tin electrolytic refining process. This study investigated a route to separate Sn, Sb, Bi, and Cu from tin anode slime after leaching with hydrochloric acid. In the solvent extraction process with tributyl phosphate, Sb and [...] Read more.

Tin anode slime is a by-product of the tin electrolytic refining process. This study investigated a route to separate Sn, Sb, Bi, and Cu from tin anode slime after leaching with hydrochloric acid. In the solvent extraction process with tributyl phosphate, Sb and Sn were extracted into the organic phase. Bi and Cu were unextracted and remained in the liquid phase. In the stripping experiment, Sb and Sn were stripped and separated with HCl and HNO₃. Bi and Cu in the aqueous phase were also separated with chemical precipitation procedure by controlling pH value. The purities of Sn, Sb, Cu solution and the Bi-containing solid were 96.25%, 83.65%, 97.51%, and 92.1%. The recovery rates of Sn, Sb, Cu, and Bi were 76.2%, 67.1%, and 96.2% and 92.4%. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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