Journal of Sustainable Metallurgy最新文献

Global concerns about climate change are driving increased demand of electric vehicles for sustainable transportation and turbines in emerging energy solutions, where permanent magnets (PMs) and rare earth elements (REEs) play a critical role. However, global REEs recycling rates are only 3% and 8% for light and heavy REEs, respectively. This work proposes an effective approach to separate the REEs and iron via high-pressure selective leaching by low-concentrated nitric acid from the end-of-life NdFeB magnet and investigates the impurities behavior during the leaching and precipitation steps. The results from the optimized leaching conditions demonstrated over 95% REEs leaching efficiency with less than 0.3% Fe dissolution. Approximately 70% of Al and B were leached as well, while other elements (Co, Ni, Cu) had leaching efficiencies below 40%, leaving a hematite rich residue. Adjusting the pH removes Al and Fe in leachate but minimally affects Cu, Co, and Ni. Na₂S addition is more effective against transition metals, but both methods result in around 10% REEs loss. Direct oxalate precipitation is suggested for the obtained leachate, which can yield over 97.5% REEs oxides with approximately 1.0% alumina, which is acceptable for magnet remanufacturing due to the aluminum content commonly found in magnets. The technology developed in this study offers opportunities for closed-loop recycling and remanufacturing of PMs, benefiting the environment, economy, and supply chain security.

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The chemical and thermophysical properties of carbon make it essentially irreplaceable for non-reductant uses in many high-temperature metallurgical processes. At present, biocarbon substitutes are not technically feasible for large-scale application in electrode and refractory materials that are such vital consumables in the steel, aluminum, and non-ferrous metal industries. Carbon electrodes of all types, including Söderberg, prebaked, and anodes/cathodes for Al, graphite electrodes, as well as carbon lining pastes are all similar in that they are comprised of a granular carbon aggregate bonded in a carbon-based binder matrix. Similarly, refractories such as MgO–C utilize both natural (mined) graphite and carbon-based binders. Replacement of fossil carbon materials with biocarbon substitutes has the potential to dramatically reduce the carbon footprints of these products. However, there are considerable materials engineering challenges that must be surmounted. The technological demands for these applications and potential for substitution with biogenic carbon are explored.

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The steel industry is one of the main contributors to global greenhouse gas emissions, responsible for about 7 to 9% of the world’s total output. The steel sector is under pressure to move toward net-zero emissions by reducing its consumption of coke as the main method of reducing iron-rich feed materials to iron. Due to its well-developed synthesis process, high supply chain, straightforward handling technologies, and highly developed long-standing infrastructure, ammonia has the potential to become a replacement for coke as a future iron ore reductant. This work reviews previous research on ammonia direct reduction of iron oxides and the possible formation of iron nitrides. A thermodynamic assessment using FactSage 8.2 thermochemical software was carried out examining the behavior of ammonia gas as the reductant upon heating, detailed evaluations of the stable phases present under different reaction conditions and using different feed materials, and the formation and stability of iron nitride phases. The results suggest that the reduction of hematite with ammonia occurs in two steps below 570 °C and three steps above 570 °C. The ratio of Fe₂O₃/NH₃ was predicted to affect the reduction reactions by promoting a greater reduction degree and simultaneously lowering the initial temperature needed for reduction, while the excess gas concentration can suppress FeO formation. A predominance area diagram was developed showing the main areas of stable phases as a function of the partial pressure of NH₃ and temperature. The formation of iron nitrides during the process was predicted and these were not expected to cause issues for the formation of iron due to their instability under the conditions studied. This analysis can be used to inform further experimental studies regarding ammonia reduction of iron oxide.

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Carbochlorination was employed to synergistically extract valuable components (Al and Si) and critical metals (Li, Ga, and Sc) from high-alumina fly ash (HAFA). The effects of gas flow, chlorination time, oxygen content, coking coal addition amount, and chlorination temperature on HAFAcarbochlorination were experimentally investigated. Then, the phase transformation of HAFA was systemically investigated via XRD, SEM/EDS, and FT-IR analysis to determine the carbochlorination mechanism. Experimental investigation shows that under the optimal experimental conditions (gas flow, 10 L/min; oxygen concentration, 15%; C/O molar ratio, 1.379; chlorination temperature, 1100 °C; and chlorination time, 60 min), the chlorination rates of Al₂O₃, SiO₂, Li₂O, Ga₂O₃, and Sc₂O₃ reach 89.04%, 72.02%, 96.15%, 97.02%, and 95.30%, respectively. Chlorination residue characterizations show that the main phase mullite in HAFA is involved in carbochlorination, the aluminum in mullite is the first to complete chlorination, and the unreacted silicon is transformed into the cristobalite phase. Part of the aluminum and silicon in mullite participate in carbochlorination, resulting in the defects of mullite structure and transformation into mullite mesophase (Al_1.69Si_1.22O_4.85). Finally, SiO₂ participated in carbochlorination to produce SiCl₄. Since Li, Ga, and Sc are coated in aluminum–silicon glass, they all participate in the carbochlorination after the mullite structure is broken, transforming into the corresponding metal chlorides. AlCl₃, SiCl₄, GaCl₃, and ScCl₃ are collected in the condensing tubes, while LiCl and CaCl₂ remain in the chlorination residues.

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The experimentation allowing comparison of manganese ore fines pellet sintering and traditional sintering of manganese ore fines in terms of sintering performance are studied. The results show that, compared with traditional sintering, the pellet-sintering process can significantly reduce the coke level while ensuring the quality of sinter. Pellet sintering required 10.54 kgce/t lower solid fuel rate in total and 26.28 kgCO₂/t lower CO₂ emission rate than traditional one, of which solid fuel consumption and CO₂ emission rate are 88.7 kgce/t and 221.13 kgCO₂/t, respectively. In addition, pellet-sintering products exhibit higher electrical resistivity and a superior tumble index compared to traditional manganese sintered products. Compared with traditional sintering, the electrical resistivity and tumbling index of pellet-sintering products are changed from 30.6 MΩ·m, 51.7% to 49.9 MΩ·m, and 62.5%, respectively. It provides a new method for low-carbon production of manganese ore fines.

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This study explores the isothermal hydrogen reduction of sintered pellets made of a mixture of bauxite residue and calcite with varying compositions at different reduction temperatures. Sintered pellets with varying compositions show three primary iron-containing oxide phases including brownmillerite, srebrodolskite, and fayalite; however, brownmillerite is the major phase in all the sintered pellets. The sintered pellets were reduced in a thermogravimetry furnace to establish instantaneous weight reduction with respect to time. Phases and microstructural analysis were carried out using X-ray diffraction and scanning electron microscopy, respectively. Mercury intrusion porosimeter and pycnometer were utilized to assess the porosity and density of the reduced pellets. Thermochemistry calculations were performed using the thermodynamics software FactSage 8.2. The reduction rate is most pronounced at a temperature of 1000 °C for all pellet compositions. It is intriguing to note that the rate of reduction shows minimal variance across pellets with different compositions; however, the higher calcite pellets exhibit a higher initial rate of reduction. Various kinetic models were examined to determine the activation energies for three different composition pellets, and the three-dimensional diffusion model has been well suited for this process. Close activation energies in the range of 84.6 to 94.8 kJ were obtained. A slightly higher activation energy was obtained for lower CaCO₃ added pellets, and it was attributed to their reduced porosity and increased sintering, impeding the reaction kinetics. There were no significant differences in the formation of mayenite with varying the calcite amount; however, higher calcite pellets indicated more mayenite formation.

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End-of-life lithium-ion batteries (LIBs) are waste from electric vehicles that contain valuable and critical metals such as cobalt and lithium in their composition. These metals are at risk of supply due to the increase in demand in the manufacture of technological products and the concentration of reserves in specific countries. When we talk about urban mining, the step of separation and purification is difficult and crucial for development of technology to recover metals because there are many problems when we have a mix and different concentration of these metals. Thus, this study aim is to clarify the techniques used in the recovery of LIBs residues for the NCA type. The NCA-type batteries, which contain, in addition to lithium (Li), cobalt (Co) and nickel (Ni), the element aluminium (Al) in their cathode structure. It is observed was carried out on the recovery of LIBs of all types, and a gap was observed regarding NCA type. Although many studies cover the recovery of metals in cathode structures from LIBs, it is not observed for batteries containing Al. Its observed that aluminium is a problem for the separation process because of its chemical characteristics. Based on this analysis, the recovery of metals presents in the NCA type batteries, the route proposed is that the first step should be the precipitation of aluminium, followed by solvent extraction of cobalt, and the last step is the precipitation of nickel, followed by lithium precipitation.

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Biochar from seaweed, specifically sugar kelp, cultivated on the Norwegian coastline has been investigated as a possible biocarbon source for the metal industry to reduce the dependency on terrestrial biomass. Pre-processing of the biomass prior to pyrolysis is needed to reduce the water and ash content and was performed by water and acid washing followed by drying. The three types of biochar were obtained after pyrolysis at a temperature of 550 °C. Characterization of the three batches of biochars showed that pre-processing of the seaweed as was done during the water and acid washing, plays an important role on the removal of ash content. Due to the enormous amount of woody biomass needed for example in the ferroalloy industry to replace fossil coal, replacing only parts of the woody biomass with kelp biochar could have a significant impact. Water washing combined with acid washing had the best results considering the ash and fixed carbon contents. Microstructural analysis of the seaweed biochars showed a very porous material with the crystal structure resembling that of charcoal, albeit a lower degree of crystallinity.

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The burgeoning accumulation of vanadium-titanium magnetite tailings (VTMT) presents a dual challenge of environmental hazard and loss of valuable metal resources. This review arrives at a crucial juncture in global efforts towards a circular economy, focusing on innovative and effective metal recovery technologies. We explore the forefront of recycling methodologies, including suspension magnetization roasting, chlorination roasting, hydrometallurgical methods, and emerging approaches like MnO₂ roasting, magnesia and calcium roasting, and microwave oxidation roasting. Our analysis juxtaposes these advanced methods against traditional techniques, emphasizing their superior environmental and resource recovery benefits. Despite promising advancements, these technologies are still in nascent stages, each presenting unique merits and limitations that necessitate further research. This paper delves into the future trajectory of VTMT recycling, emphasizing the integration of technological innovation with environmental and resource stewardship. By tackling the specific challenges of VTMT, we underscore the urgency for holistic, efficient, and eco-friendly solutions. The future of VTMT metal recovery hinges on the progressive refinement and amalgamation of these technologies, underscored by a commitment to balancing ecological concerns with societal demands.

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It is crucial to control the sulfur and oxygen in the steel liquid to produce high-cleanliness rare earth steel. This study attempted to investigate the effect of rare earth Ce content on purifying the produced 7CrSiMnMoV steel from scrap steel by modified rare earth inclusions based on a proposed integrated process of high-alkalinity refining slag desulfurization, Si–Mn deoxidation, Al-enhanced deoxidation, and rare earth Ce alloying. The results show that the evolution mechanism of rare earth inclusions is 25% Al₂O₃⋅25% MgO⋅50% Ce₂O₃ → 25% Al₂O₃⋅75% Ce₂O₃, 12.5% Al₂O₃⋅MnS⋅Ce₂O₂S → Ce₂O₃, Ce₂O₂S → Ce₂S₃, Ce₂O₂S → (Mn Ce)₂S₃, Ce₂O₂S, with the rare earth Ce-added content of 0.009%, 0.012%, and 0.100%, respectively. And rare earth Ce can improve the cleanliness of steel liquid by controlling the rare earth Ce-added content to form the M1-Ce₂O₃ (M1 is Al, Mg, etc.) and M2-Ce₂SO₂ (M2 is Ca, Mn, etc.) rare earth inclusions; the oxygen and sulfur concentrations can reach 0.0031% and 0.0026%, respectively, with a rare earth Ce content of 0.012%. However, excessive amounts of rare earth Ce could deteriorate the cleanliness of steel liquid.

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To produce 7CrSiMnMoV rare earth steel by scrap steel based on an integrated process of high-alkalinity refining slag desulfurization, Si–Mn deoxidation, Al-enhanced deoxidation, and rare earth Ce alloying and purifying steel liquid.Purifying 7CrSiMnMoV rare earth steel liquid by modified rare earth inclusion.Rare earth Ce can improve the cleanliness of steel liquid by controlling the rare earth Ce-added content to form M-Ce2O3 (M is Al, Mg, etc.) and M-Ce2SO2 (M is Ca, Mn, etc.) rare earth inclusions; the oxygen and sulfur concentrations can reach 0.0031% and 0.0026%, respectively, with a rare earth Ce content of 0.012%.