Search Results (176)

The electric arc furnace (EAF) process includes key stages: charging scrap metal, melting using electric arcs, refining through oxygen injection and slag formation, and tapping molten steel. Recently, EAF steelmaking has become increasingly important due to its flexibility with recycled materials, lower environmental impact, and reduced investment costs. This study focuses specifically on select aspects of the refining stage, analysing decarburization and the associated exothermic oxidation reactions following the removal of carbon with oxygen injection. Particular attention is given to FeO generation during refining, as it strongly affects slag chemistry, yield losses, and overall efficiency. Using a Computational Fluid Dynamics (CFD)-based refining simulator validated with industrial data from EVRAZ North America (showing an 8.57% deviation), this study investigated the impact of oxygen injection rate and burner configuration. The results in a three-burner EAF operation showed that increasing oxygen injection by 10% improved carbon removal by 5%, but with an associated increase of FeO generation of 22%. Conversely, reducing oxygen injection by 15% raised the residual carbon content by 43% but lowered FeO by 23%. Moreover, the impact of the number of burners was analysed by simulating a second scenario with 6 burners. The results show that by increasing the number of burners from three to six, the target carbon is reached 33% faster while increasing FeO by 42.5%. Moreover, by reducing the oxygen injection in the six-burner case, it is possible to reduce FeO generation from 42.5 to 28.5% without significantly impacting carbon removal. This set of results provides guidance for burner optimization and understanding the impact of oxygen injection on refining efficiency. Full article

This study signifies the development and characterization of a composite material with a metallic matrix of aluminum reinforced with a steel mesh, utilizing centrifugal casting technology. An evaluation was conducted to ascertain the influence of the formulation process and the presence of the insert on the mechanical behavior with regard to tensile strength. The aluminum matrix was obtained from commercial and scrap alloys, elaborated by advanced methods of degassing and chemical modification. Meanwhile, the steel mesh reinforcement was cleaned, copper plated, and preheated to optimize wetting and, consequently, adhesion. The structural characterization was performed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy analyses (EDX), which highlighted a well-defined interface and uniform copper distribution. The composite was produced by means of horizontal-axis centrifugal casting in a fiberglass mold, followed by cold rolling to obtain flat specimens. A total of eight tensile specimens were examined, with measured ultimate tensile strengths ranging from 78.5 to 119.8 (MPa). A thorough examination of the fractured specimens revealed a brittle fracture mechanism, devoid of substantial plastic deformation. The onset of failures was frequently observed at the interface between the aluminum matrix and the steel mesh. The use of SEM and EDX investigations led to the confirmation of the uniformity of the copper coating and the absence of significant porosity or interfacial defects. A bimodal distribution of tensile strength values was observed, a phenomenon that is likely attributable to variations in mesh positioning and local differences in solidification. A correlation was established between the experimental results and an analytical polynomial model, thereby confirming a reasonable fit. In sum, the present study provides a substantial foundation for the development of metal matrix composites with enhanced performance, specifically designed for challenging structural applications. This method also demonstrates potential for recycling aluminum scrap into high-performance composites with controlled microstructure and mechanical integrity. Full article

Recent archaeological sites dating to the late 19th and early 20th centuries have rarely been studied to date. Among the 500 “glassy” beads excavated from Dohouan (Côte d’Ivoire), elemental analyses reveal that fewer than half contain abnormally high alumina contents, associated with a soda–potash–lime flux (three compositional groups). The remaining beads are typical lead-based glass. The Raman spectra of the alumina-rich beads are quite complex due to their glass–ceramic nature, combining features similar to the vitreous phase of porcelain glaze with the presence of various crystalline phases (quartz, wollastonite, calcium phosphate, calcite). Organic residues are also observed. Colors are primarily produced by transition metal ions, although some specific pigments have also been identified. These characteristics suggest that the alumina-rich beads were manufactured by pressing followed by sintering, as described in patents by Richard Prosser (1840, UK) and Jean Félix Bapterosse (1844, France). A comparison is made with beads from scrap piles at the site of the former Bapterosse factory in Briare, France. This process represents one of the earliest examples of replacing traditional glassmaking with a ceramic process to enhance productivity and reduce costs. Full article

Today, lithium-ion batteries (LIBs) are widespread and play a vital role in advancing portable electronics (laptops and mobile phones), green energy technology (electrical vehicles), and renewable energy systems. There is about 30% off-spec scrap LIB production during manufacturing. This trend has caused the accumulation of a huge number of spent LIBs. In addition to containing chemicals that are harmful to the environment, these batteries also contain critical metals; their recycling will greatly help to maintain a green and sustainable economic transition. Therefore, this issue has forced researchers to seek cost-effective and eco-friendly strategies for recycling LIBs. The pretreatment of waste batteries is an essential part of LIB recycling. This article aims to comprehensively review the basic structure of LIBS and existing pretreatment methods in recycling critical metals from LIBs, with a special focus on recent innovations. This manuscript has been prepared to help researchers conduct cutting-edge and novel research in LIB pretreatment and recycling. This approach not only helps researchers to understand the concepts, but also helps to identify and evaluate the strengths and weaknesses of different pretreatment methods. Also, in addition to mentioning the existing research limitations, suggestions for future research perspectives and less investigated areas that need further research have been presented. Full article

The recycling of cable scrap, particularly from discarded electrical wiring, is gaining significant attention due to the rising demand for copper and the need for sustainable management of electronic waste. Traditionally, mechanical and thermal processings have been used to recover copper and plastic from cables. However, these approaches are often energy-intensive, time-consuming, and costly in terms of equipment and labor. In this study, we present a simple and effective method for recovering materials from cable scrap using a domestic microwave oven. Cable pieces (2–2.5 cm long) were exposed to 700 W of microwave irradiation under rotation for 30 s, enabling the rapid and efficient separation of high-quality copper metal from the core wire, and activated carbon from the carbonized plastic sheath. Microwaves facilitate this process through Ohmic heating, which induces electrical resistance in the metal, generating heat that mechanically loosens the metal and carbonized plastic components. The process demonstrates high efficiency, achieving an 80% reduction in energy consumption compared to conventional processings. This fast and energy-efficient method shows strong potential for scaling up to industrial recycling, offering a cost-effective and environmentally friendly way to recover high-quality materials for further use or repurposing. Full article

Rare earth elements (REEs) possess unique physical and chemical properties that render them indispensable in various industries, including electronics, energy production and storage, hybrid and electric vehicles, metallurgy, and petro-chemical processing. The criticality of REE underscores the need to enhance the efficiency of primary resource extraction and promote circularity through increased recycling from secondary sources. This paper provides a brief overview of REE recovery from secondary sources, particularly waste from electronic and electric equipment (WEEE). The discussion encompasses direct reuse of magnets, short-loop recycling (direct recycling), hydro- and pyrometallurgical processes, highlighting microwave (MW) technology. Original results are presented, focusing on the recovery of neodymium (Nd) from permanent magnet scraps from hard disk drives (HDD-PC) using microwave-assisted liquid metal extraction (LME) with magnesium (Mg) as the extractant. The subsequent separation of Nd from the Mg-Nd alloy via vacuum Mg distillation that is reused in the process is described. The experimental study demonstrates that the LME process, conducted in a microwave furnace, is a viable method for recovering Nd from permanent magnet scraps, which are essential for reducing the environmental impact of REE extraction and promoting a circular economy. By separating Nd from the alloy through vacuum distillation (450–550 mmHg), at temperatures of 850–900 °C for 8 h, a Nd sponge with a content of 95–98 wt.% Nd was obtained. The extracted content of Nd in the Mg alloy increases with increasing temperature and holding time. It was found that ≈ 97% of the Nd in the scrap was extracted from 2 to 5 mm crushed scrap at 800 °C for 8 h, using a LiF-LiCl-MgF₂ protecting flux in a furnace Ar atmosphere. Full article

Due to the scarcity of high-grade minerals on the Earth’s surface and the ever-increasing demand for critical metals required in the production of clean energy, the search for alternative sources has become essential. Ferromanganese crusts, a mineral resource located in the depths of the ocean, contain high concentrations of valuable metals, particularly cobalt (Co) and manganese (Mn). A leaching process using sulfuric acid, with the addition of steel scrap, has been proposed for processing this resource. The study investigated the extraction of manganese (Mn) and cobalt (Co) under acidic conditions at 25 °C, employing a factorial experimental analysis. Statistical models were adjusted using response surface methodology to evaluate the effects of time and the ferromanganese crust/Fe(res) (iron residue) ratio as predictive variables. The results demonstrated that the extraction of Mn and Co could be effectively modeled through multiple regression, with strong goodness-of-fit indicators. Optimal extraction was achieved at extended durations (30 min) and lower ferromanganese crust/Fe(res) ratios (1/3) for the sampled values. Gradient analysis revealed that extraction efficiency was directly proportional to time and inversely proportional to the ferromanganese crust/Fe(res) ratio, except in the case of Co extraction at higher durations and lower ratio levels. Additionally, no precipitation of Mn or Co species was observed in the analyzed residues. Full article

Acid mine drainage (AMD) forms in mining areas during or after mining operations cease. This is a primary cause of environmental pollution and poses risks to human health and the environment. The hydrographic system from the Maramureș mining industry (especially the Baia Mare area) was heavily contaminated with heavy metals for many years due to mining activity, and after the closing of mining activity, it continues to be polluted due to water leaks from the abandoned galleries, the pipes, and the tailing ponds. The mineralization in the Băiuț area, predominantly represented by pyrite and marcasite associated with other sulfides, such as chalcopyrite, covelline, galena, and sphalerite, together with mine waters contribute to the formation of acid mine drainage. The Breiner-Băiuț mining gallery (copper mine) permanently discharges acidic water into the rivers. The efficiency of iron scrap (low-cost absorbent) for the treatment of mine water from this gallery was investigated. The treatment of mine water with iron shavings aimed to reduce the concentration of toxic metals and pH. Mine water from the Breiner-Baiut mine, Romania, is characterized by high acidity, pH = 2.75, and by the association of many heavy metals, whose concentration exceeds the limit values for the pollutant loading of wastewater discharged into natural receptors: Cu—71.1 mg/L; Zn—42.5 mg/L; and Fe—122.5 mg/L. Iron scrap with different weights (200 g, 400 g, and 600 g) was put in contact with 1.5 L of acid mine water. After 30 days, all three treatment variants showed a reduction in the concentrations of toxic metals. A reduction in Cu concentration was achieved below the permissible limit. In all three samples, the Cu concentrations were 0.005 for Sample 1, 0.001 for Sample 2, and <LOQ for Sample 3. The Zn concentration decreased significantly compared to the original mine water concentration from 42.5 mg/L to 1.221 mg/L, 1.091 mg/L, and 0.932 mg/L. These values are still above the permissible limit (0.5 mg/L). The Fe concentration increased compared to the original untreated water sample due to the dissolution of iron scrap. This research focuses on methods to reduce the toxic metal concentration in mine water, immobilizing (separating) certain toxic metals in sludge, and immobilizing various compounds on the surface of iron shavings in the form of insoluble crystals. Full article

The study explored the possibility of producing thick coatings of fully metallic composite phase change materials with suitable microstructure for thermal energy storage or thermal energy management purposes. The composite materials are based on Al-Si-based alloys with Sn additions, potentially obtainable from scraps. This leads to an Sn-rich low-melting phase which is able to store/release heat when it melts/solidifies. The material can thus be considered as a composite phase change material (C-PCM). A thick coating was deposited on an Al alloy substrate by plasma spray, mixing AlSi10Mg and Sn powders in a 60:40% mass ratio. Optical scanning microscopy and X-ray diffraction revealed a microstructure suitable for a C-PCM, presenting Sn basins interrupted by a matrix made up of primary Al and Al–Si eutectic. Preliminary investigation into the reliability of the coating was conducted by performing up to 10 heat cycles across the melting temperature of the low-melting phase, simulating service in TES/TEM devices. No significant changes in its coating microstructure were observed. Minor surface leakage of molten Sn occurred, mainly during the first heat cycle. No detachment of the coating or cracks formed within the coating were observed, which could have been expected due to the mismatch in the coefficients of thermal expansion of the main phases and to the expansion/shrinkage due to Sn melting/solidification. Full article

In view of the increasing demand for secondary aluminum, which is intended to partially replace the very energy- and resource-intensive primary aluminum production, effective treatment methods can maintain the high quality level of light metal castings. The transition from a linear to a circular economy can result in an accumulation of oxides or carbides in aluminum. Therefore, melt purification is crucial, especially as foundries aim to increase the use of often dirty end-of-life scrap. Nonmetallic inclusions in the melt can impact its flowability and mechanical properties. As the purity of the melt increases, its flow length also tends to increase. Available assessment methods like reduced pressure test or K-mold are capable of ensuring high levels of purity. This study demonstrates the implication of inclusions originating from dirty scrap. An experimental test run deals with various scrap contents in an AlSi7Cu0.5Mg alloy and shows correlations between impurity and performance, expressed by flowability and mechanical properties. These performance indicators have been connected to inclusion and porosity rates. In conclusion, these findings emphasize the need for further extensive research on contaminants in the field of scrap melting and the development of methods for easy-to-handle assessment methods. Full article

This study employed dynamic material flow analysis (MFA) and mass balance principles to examine copper flows in Indonesia, Malaysia, the Philippines, Thailand, and Vietnam from 1960 to 2020, with projections extending to 2050 using five shared socioeconomic pathway (SSP) scenarios. We applied the secondary resources classification framework to assess secondary copper resources and their recoverability in these countries. The results indicated that total copper stocks across these countries would continue to rise, with Indonesia’s copper stock projected to reach around 5000–12,000 kt by 2050, the highest among the five nations. In 2022, Malaysia had the highest per capita copper stock at 100 kg/person, although all countries were expected to remain below the per capita stock levels seen in major copper-consuming developed countries by 2050. Copper demand was projected to increase by 118–238 kt annually from 2023 to 2050, leading to a significant rise in end-of-life copper scrap. By 2050, secondary copper reserves in Indonesia were estimated to reach 4096 kt, with similar growth trends observed in other countries (3898 kt in Thailand, 3290 kt in Vietnam, 3096 kt in Malaysia, and 2564 kt in the Philippines). This highlights both the potential for resource recovery and the need for improved waste management. If recycling rates increase to 80–90%, secondary reserves could meet up to 42–65% of the copper demand in 2050. However, current recycling rates remain well below this potential, underscoring the urgent need for better waste management systems. This study emphasizes the balance between economic development and resource sustainability, offering critical insights for policymakers to improve recycling efficiency and reduce reliance on primary copper sources. Full article

This study aims to provide insights into the experimental conditions used during the melting/casting process and subsequent thermal treatments of low-alloy steels, particularly regarding recycled scrap metals. As sustainable practices in metallurgy gain importance, optimizing scrap metal recycling is crucial for producing steel grades with desired chemical compositions, microstructures, and physical properties. Understanding these conditions is vital for enhancing the efficiency and quality of steel production from recycled materials. This study emphasizes the critical role of specific experimental conditions in the steelmaking process, especially with recycled scrap metals. It closely examines the atmosphere during melting/casting to identify key parameters that must be rigorously controlled in lab-scale steel production using a vacuum induction furnace. The findings indicate that both the chemical composition and recyclability of low-alloyed steels are significantly influenced by the surrounding atmosphere during melting and casting. Inert environments, such as vacuum or argon, are shown to be ideal for steelmaking with induction technology, particularly when recycling scrap metals. Additionally, this study highlights the importance of precise heat treatments, including homogenization and normalization, by controlling both thermal conditions and the atmosphere to produce high-quality steel from recycled scraps. Full article

Traditionally, precious metals are processed by either lost-wax casting or the casting of semi-finished products followed by cold or hot working, machining, and surface finishing. Long process chains usually conclude in a high material input factor and a significant amount of new scrap to be refined. The maturing of Additive Manufacturing (AM) technologies is advantageous with regard to resources among other criteria by opening up new processing techniques like laser-based powder bed fusion (LPBF) for the production of near net shape metal products. This paper gives an insight into major advantages of the powder-based manufacturing of precious metal components over conventional methods focusing on product carbon footprints (PCF). Material Flow Cost Accounting (MFCA) for selected applications show energy and mass flows and inefficient recoverable losses in detail. An extended MFCA approach also shows the greenhouse gas (GHG) savings from avoiding recoverable material losses and provides PCF for the products. The PCF of the precious metals used is based on a detailed Life Cycle Assessment (LCA) of the refining process of end-of-use precious metals. In the best case, the refining of platinum from end-of-life recycling, for example, causes 60 kg CO_2e per kg of platinum. This study reveals recommended actions for improvements in efficiency and gives guidance for a more sustainable production of luxury or technical goods made from precious metals. This exemplary study on the basis of an industrial application shows that the use of AM leads to a carbon footprint of 2.23 kg CO_2e per piece in comparison with 3.17 kg CO_2e by conventional manufacturing, which means about a 30 percent reduction in GHG emissions and also in energy, respectively. Full article

This study investigates the optimization of liquid metal leaching for recycling rare earth elements (REEs) from NdFeB magnets, a critical step in addressing the increasing demand for these materials in various high-tech applications. We explored the effects of leaching time, stirring, and magnet demagnetization on the yield of the leaching process using molten magnesium. Conducted at 900 °C, our experiments assessed the leaching process over periods of 2, 3.5, and 5 h, with and without the application of stirring. Our findings show that longer leaching times considerably increase neodymium (Nd) and praseodymium (Pr) leaching yield, with a notable peak in efficiency found at 5 h. Stirring improved the uniformity of REEs significantly and resulted in up to 80% yield. Furthermore, our data show that pre-leaching magnet demagnetization improves leaching specificity, significantly reducing the presence of non-target metals like nickel and copper. These insights offer a pathway to more cost-effective recycling of REEs from magnet scrap, which is essential for environmentally conscious management of resources amid the escalating global demand for REEs. Full article

The development of hydrometallurgical recycling processes for lithium-ion batteries is challenged by the heterogeneity of the electrode powders recovered from end-of-life batteries via physical methods. These electrode materials, known as black mass, vary in composition, containing differing amounts of nickel, manganese, and cobalt (NMC), as well as other chemicals, such as lithium iron phosphate (LFP). This study presents the results of the hydrometallurgical treatment of mixed NMC and LFP black masses aimed at creating flexible recycling processes. This approach leverages the reducing power of LFP to optimize the leach liquor composition for re-synthesizing NMC precursors. In particular, the leaching conditions were optimized based on the LFP content in the solid feed to maximize the extraction of key metals (Ni, Mn, Co, and Li). The leaching solid residue, graphite, was treated and characterized as a secondary raw material for new anode preparation. Iron phosphate was recovered by increasing the pH of the leach liquor, and the NMC precursors were obtained via coprecipitation. This process achieved a recycling rate of 51%, based on the black mass input and the mass of recovered elements in the output products. Additionally, substituting LFP scraps as the reducing agent in place of H₂O₂ reduced the recycling process’s environmental impact by avoiding 1.7 tons of CO₂-equivalent emissions per ton of NMC black mass. Full article