Global crises caused by the pandemic of COVID-19, since early 2020, can compromise the world commitment to the 2030 Agenda for Sustainable Development. This study discusses critical aspects of the ...global pandemic for the achievement of the Sustainable Development Goals (SDGs). More precisely, we analyze how the new circumstances created by the pandemic have affected the interdependencies between SDGs. Following a synopsis of the current literature, we focus on effects regarding SDG3 (Health & Well-Being), SDG4 (Quality Education), SDG8 (Decent Work & Economic Growth), SDG12 (Consumption & Production) and SDG13 (Climate Action). Following a qualitative research approach, we based our analysis on moderated focus group discussions (FGD). Our observations reveal a unique pattern of interconnectedness between SDGs that can be related to COVID-19 consequences. Qualitative interpretations of focus group discussions also depict, that additional spillover effects can be obstacles for achieving SDG 5 (Gender Equality), SDG 9 (Infrastructure & Innovation) and SDG 10 (Reducing Inequalities), SDG 17 (partnerships for the goals), SDG 11 (sustainable cities). Therefore, we consider the interdependent implications and recent trends in international development related to sustainability as a useful framework in the post-pandemic recovery period.
Raising social awareness and environmental specifications on cyanide application force gold industry to search for alternative leaching reagents. Therefore, researchers worldwide investigate cyanide ...alternatives for gold recovery since several decades. Often the research activities cannot be compared directly, since different input materials and experimental conditions are used. Over the course of this study, different promising cyanide alternative reagents were investigated in terms of their capability of pure gold dissolution at different temperatures. All experiments took place under identical conditions by using uniform samples of 99.99% gold disks, to enable a comparability. Thiosulfate as one of the most promising reagent thiosulfate according to literature revealed an insufficient leaching behavior. The gold dissolution was hindered due to the formation of a sulfide passive layer. Also in the thiourea trials, a surface precipitation took place, though gold dissolution did not stop. The halogens iodine, bromine and the well-known gold solvent aqua regia dissolved gold very fast (up to ~1,000 mg·h
·cm
). Methanosulfonic acid (MSA) was not capable to extract any gold. The experiments were compared with cyanide trials at identical conditions. The average dissolution rate of investigated reagents at 25 °C shows following order: aqua regia > iodine > bromine > cyanide > thiourea > thiosulfate > MSA.
The metallurgical industry is a major source of anthropogenic greenhouse gas emissions. This study explores the replacement of fossil-reducing agents with potentially CO2-neutral bio-based reducing ...agents. Since reducing agents remove oxygen bonded with metal oxides present in the ore, they are a necessity for the production of metallic elements. The investigated metal is chromium, a major part of stainless steel, and therefore a highly relevant element for the transition from a fossil-based energy system to a renewable one. The state-of-the-art smelting reduction and pre-reduction process followed by subsequent smelting using various reducing agents are investigated in this article. The obtained products, metallurgical efficiencies, energy consumption and off-gas generation were compared. While the products produced with bio-based reducing agents are comparable with the reference trials using metallurgical coke regarding the major components in the metal, the concentration of detrimental phosphorus is significantly higher using bio-based reducing agents. The metallurgical efficiency of the process is comparable to the usage of bio-based reducing agents and coke. However, the energy consumption and the generation of off-gas is higher, when coke is replaced by bio-based reducing agents.
The production of ferroalloys and alloys like ferronickel, ferrochromium, ferromanganese, silicomanganese, ferrosilicon and silicon is commonly carried out in submerged arc furnaces. Submerged arc ...furnaces are also used to upgrade ilmenite by producing pig iron and a titania-rich slag. Metal containing resources are smelted in this furnace type using fossil carbon as a reducing agent, which is responsible for a large amount of direct CO2 emissions in those processes. Instead, renewable bio-based carbon could be a viable direct replacement of fossil carbon currently investigated by research institutions and companies to lower the CO2 footprint of produced alloys. A second option could be the usage of hydrogen. However, hydrogen has the disadvantages that current production facilities relying on solid reducing agents need to be adjusted. Furthermore, hydrogen reduction of ignoble metals like chromium, manganese and silicon is only possible at very low H2O/H2 partial pressure ratios. The present article is a comprehensive review of the research carried out regarding the utilization of bio-based carbon for the processing of the mentioned products. Starting with the potential impact of the ferroalloy industry on greenhouse gas emissions, followed by a general description of bio-based reducing agents and unit operations covered by this review, each following chapter presents current research carried out to produce each metal. Most studies focused on pre-reduction or solid-state reduction except the silicon industry, which instead had a strong focus on smelting up to an industrial-scale and the design of bio-based carbon for submerged arc furnace processes. Those results might be transferable to other submerged arc furnace processes as well and could help to accelerate research to produce other metals. Deviations between the amount of research and scale of tests for the same unit operation but different metal resources were identified and closer cooperation could be helpful to transfer knowledge from one area to another. Life cycle assessment to produce ferronickel and silicon already revealed the potential of bio-based reducing agents in terms of greenhouse gas emissions, but was not carried out for other metals until now.
When classifying impurities in commercial pure antimony (Sb, 99.8%), arsenic (As) and lead (Pb) should be brought to the forefront consideration. Due to the known difficulty of As removal through ...zone refining, it is meaningful to investigate its separation tendency through alternative methodologies such as vacuum distillation, promoted by the large difference of their vapor pressures. Here, a series of vacuum distillation trials with different process parameters were at first conducted with the aim of As removal. Pb, as an always accompanying impurity, seemed to be able to be significantly separated from Sb, so that its content in the refined phase could be reduced too, e.g. from 1200 ppm to less than 30 ppm. The reduction of As, however, is highly dependent on the distillation ratio of Sb and hence limited just to 450 ppm. The biggest obstacle here was the simultaneous evaporation of Sb and As when using high temperature and low pressure. In order to suppress the evaporation of As more intensely in vacuum distillation or selectively capture As in zone refining process, the additives – aluminum (Al) and zinc (Zn) – were studied and selected by using the respective phase diagrams as well as thermochemical Software FactSage and then individually added to Sb as alloying elements with the aim of intermetallic formation with As. The addition of Al led to a considerable reduction of As in vacuum distillation as well as while zone refining process. During vacuum distillation, 67% less As was obtained in the condensate in comparison to the trial without additive. Meanwhile, a huge As concentration gradient appeared in the residual Sb. During zone refining process, As concentration in the whole bar was considerably reduced from 456 ppm to below 150 ppm after only one zone pass, due to the enrichment of Al at the end of the bar in accompanying with As in form of an intermetallic compound. The addition of Zn, on the contrary, did not convince as an effective improvement in purification of Sb. In order to achieve a higher efficiency of As removal from Sb, the authors at the first priority suggest an addition of Al directly into the zone refining process. If specifically a vacuum distillation process is preferred, a multi-stage condenser, equipped with controlled temperatures, attendant with the addition of Al in the charge material, can deliver effective results as well.
Unit operations (UO) are mostly used in non-ferrous extractive metallurgy (NFEM) and usually separated into three categories: (1) hydrometallurgy (leaching under atmospheric and high pressure ...conditions, mixing of solution with gas and mechanical parts, neutralization of solution, precipitation and cementation of metals from solution aiming purification, and compound productions during crystallization), (2) pyrometallurgy (roasting, smelting, refining), and (3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). The high demand for critical metals, such as rare earth elements (REE), indium, scandium, and gallium raises the need for an advance in understanding of the UO in NFEM. The aimed metal is first transferred from ores and concentrates to a solution using a selective dissolution (leaching or dry digestion) under an atmospheric pressure below 1 bar at 100 °C in an agitating glass reactor and under a high pressure (40–50 bar) at high temperatures (below 270 °C) in an autoclave and tubular reactor. The purification of the obtained solution was performed using neutralization agents such as sodium hydroxide and calcium carbonate or more selective precipitation agents such as sodium carbonate and oxalic acid. The separation of metals is possible using liquid (water solution)/liquid (organic phase) extraction (solvent extraction (SX) in mixer-settler) and solid-liquid filtration in chamber filter-press under pressure until 5 bar. Crystallization is the process by which a metallic compound is converted from a liquid into a crystalline state via a supersaturated solution. The final step is metal production using different methods (aqueous electrolysis for basic metals such as copper, zinc, silver, and molten salt electrolysis for REE and aluminum). Advanced processes, such as ultrasonic spray pyrolysis, microwave assisted leaching, and can be combined with reduction processes in order to produce metallic powders. Some preparation for the leaching process is performed via a roasting process in a rotary furnace, where the sulfidic ore was first oxidized in an oxidic form which is a suitable for the metal transfer to water solution. UO in extractive metallurgy of REE can be successfully used not only for the metal wining from primary materials, but also for its recovery from secondary materials.
Metallic materials play a vital role in the economic life of modern societies; hence, research contributions are sought on fresh developments that enhance our understanding of the fundamental aspects ...of the relationships between processing, properties, and microstructures. Disciplines in the metallurgical field ranging from processing, mechanical behavior, phase transitions, microstructural evolution, and nanostructures, as well as unique metallic properties, inspire general and scholarly interest among the scientific community. Three of the most important elements are included in unit operations in non-ferrous extractive metallurgy: (1) hydrometallurgy (leaching under atmospheric and high-pressure conditions, mixing of a solution with a gas and mechanical parts, neutralization of a solution, precipitation and cementation of metals from a solution aiming at purification, and compound productions during crystallization), (2) pyrometallurgy (roasting, smelting, and refining), and (3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). Advances in our understanding of unit operations in non-ferrous extractive metallurgy are required to develop new research strategies for the treatment of primary and secondary materials and their application in industry.
The thermal treatment of lithium-ion batteries is an already industrially implemented process step in some recycling chains. It provides the advantages of controlled organic removal and conditioning ...of the black mass for further process steps, such as water-based early-stage lithium recovery. Therefore, a deep understanding of ongoing reactions and the influence of the process parameters on the reaction products is crucial. This study investigates the inert thermal treatment of an industrial end-of-life NMC 622 battery shredder in a 200 g scale regarding the influence of process parameters on the reaction products, separation of black mass, and its water leaching. Therefore, the off-gas produced during the thermal treatment was analyzed by FTIR, and afterwards, a sieve classification of the shredder was carried out. The separated black mass was further analyzed for residual organics by pyrolysis GC-MS and for its phase composition by XRD. A water leaching of the different thermally treated black masses was carried out for Li recovery. Occurring reactions during the thermal treatment process, such as the different stages of organic removal and reduction reactions in the active material, were derived based on the collected data. These reactions mainly affect the water-based Li recovery, which is related to Li2CO3 generation. The maximum pyrolysis temperature has the greatest effect on the Li recovery. After a treatment at 642 °C, 62.4% of Li was leached. Reactions of the co-elements F, P and Al with Li during the thermal treatment were identified as the limiting factors regarding Li recovery.
The recycling of lithium-ion batteries (LIBs) is becoming increasingly important regarding the expansion of electromobility and aspects of raw material supply. Pre-treatment and liberation are ...crucial for a sufficient recovery of all relevant materials from LIBs. Organic removal and phase transformations by thermal pre-treatment are beneficial in many respects. This study deals with the influence of flow-gas composition on reaction products and water-based lithium recovery after thermal treatment. Therefore, a spent NMC black mass was thermally treated at 610 °C in a moved bed batch reactor under an N2 atmosphere and mixtures of N2 with 2.5% and 5% O2. Since the phase transformation of the lithium content to Li2CO3 is targeted for water leaching, a treatment under a CO2 atmosphere was studied as well. The resulting off-gas was analyzed by FTIR, and the black mass was characterized by XRD. Afterward, water washing of the black mass was carried out for selective lithium recovery. The gained lithium product was analyzed for the purity and phases present. The addition of O2 resulted in reduced reduction reactions of lithium metal oxides and lower Li-yields in the water leaching compared to the other two atmospheres. In the case of CO2, the formation of Li2CO3 is favored compared to LiF, but the Li-yield of 56% is comparable to N2 treatment.
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