Mine tailings, a substantial global waste stream, often contain recyclable metals with economic and environmental potential. This study focuses on the Rammelsberg mine’s Bollrich tailings pond, where residues from more than 50 years of mining and flotation processes pose contamination risks due to heavy metals. Building on prior projects aimed at recovering valuable metals from these tailings, this study optimizes the leaching of base metals, copper (Cu), zinc (Zn), and lead (Pb), using both inorganic and organic acid approaches. Leaching experiments conducted with sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) demonstrated up to 52

Colloidal silica acts as a multifunctional reagent in the froth flotation process of semi-soluble salt-type minerals, enabling the selective depression of calcite. This study investigates its effect on four key minerals—calcite, scheelite, apatite, and fluorite—using a comprehensive suite of techniques to identify the flotation subprocesses modulated by colloidal silica. This work also aims to determine the specific flotation zones affected by colloidal silica, assessing the influence of its dosage, surface modification, and specific surface area on metallurgical outcomes. Atomic force microscopy revealed mineral-specific surface responses to colloidal silica conditioning: calcite exhibited localized nanoparticle adsorption, whereas apatite underwent a dissolution–reprecipitation mechanism. Scheelite and fluorite, in contrast, showed minimal surface modifications. These differences are attributed to variations in surface reactivity, hydration behavior, and crystallographic structure, with calcite offering a uniquely favorable environment for colloidal silica attachment. Mechanistic insights show that colloidal silica—especially the aluminate-modified type with high specific surface area—influences both the pulp and froth zones by producing small, stable bubbles, enhancing fine scheelite recovery, stabilizing froth, and effectively depressing calcite. In contrast, non-functionalized colloidal silica resulted in poor bubble control and unstable froth. These findings elucidate the subprocess-specific mechanisms by which colloidal silica operates and highlight its potential as a tunable, multifunctional reagent for improving selectivity in the flotation of semi-soluble salt-type minerals.

We introduce a unique approach for faster and more systematic optimization and upscaling of reagent systems in froth flotation processes. By integrating the statistical design of experiments with numerical optimization techniques, our method ensures a seamless transition from laboratory experimentation to pilot and industrialscale implementation. This approach uses comprehensive lab-scale experimental data to assign the effects of reagent system operating parameters and pre-identify optimal conditions. These predictions streamline the optimization algorithm for continuous process improvement, minimizing its convergence issues and, consequently, the test work time and resource consumption. We validated this methodology with a case study on a low-grade scheelite ore, demonstrating a reduction of 60 % in required test work at pilot scale. A four-day industrial campaign resulted in a 16 % increase in concentrate grade without hindering recovery. Additionally, we discuss the influence of variations in ore feed properties on froth flotation performance while optimizing the reagent system. Within this context, we introduce the Grade-Recovery-Performance (GRP) index, a two-dimensional metric to quantify the performance of separation processes according to grade and recovery simultaneously.

Due to changes in the German government’s energy concept, the amount of gypsum produced in flue gas desulfurisation plants (FGD gypsum) will fall from 5 million tons per year to 1 million tons or less by 2038 at the latest. As of 2016, FGD gypsum accounts for 55% of German gypsum mix. The resulting raw material gap must be closed through innovative recycling concepts, such as the processing of existing mine dumps. The process development aims to achieve a calcium sulfate dihydrate content of 85% and a reduction in the stockpile volume by 50%. The main components of the stockpiles are calcium sulfate in the form of gypsum stone as well as clay minerals and organic matter. Successful laboratory tests were transferred to a pilot scale jigging machine with dewatering screening. The process water is circulated throughout the entire process. The gypsum content in the heavy fraction is 76% when measured with ICP OES and 87% when measured via thermogravimetric methods. Furthermore, pilot-scale dry screening on the stockpile took place, and up to 1500 tons of material could be processed. Due to fluctuating weather conditions, the screening quality was subject to significant variations. Under optimal conditions, up to 60% of the feed could be recovered as gypsum stone; however, the screening process was nearly impossible during rain; therefore, a process combination of screening and a downstream jigging machine is recommended.

Among the technologies used for spent lithium-ion battery recycling, the common approaches include mechanical treatment, pyrometallurgical processing and hydrometallurgical processing. These technologies do not stand alone in a complete recycling process but are combined. The constant changes in battery materials and battery design make it a challenge for the existing recycling processes, and the need to design efficient and robust recycling processes for current and future battery materials has become a critical issue today. Therefore, this paper simplifies the current treatment technologies into three recycling routes, namely, the hot pyrometallurgical route, warm mechanical route and cold mechanical route. By using the same feedstock, the three routes are compared based on the recovery rate of the six elements (Al, Cu, C, Li, Co and Ni). The three different recycling routes represent specific application scenarios, each with their own advantages and disadvantages. In the hot pyrometallurgical route, the recovery of Co is over 98%, and the recovery of Ni is over 99%. In the warm mechanical route, the recovery of Li can reach 63%, and the recovery of graphite is 75%. In the cold mechanical route, the recovery of Cu can reach 75%, and the recovery of Al is 87%. As the chemical compositions of battery materials and various doping elements continue to change today, these three recycling routes could be combined in some way to improve the overall recycling efficiency of batteries.

More than 218 million tonnes of mineral construction waste are produced in Germany every year. In view of the shortage of domestic raw materials and an increasing demand for lightweight aggregates and gypsum, it is important to find alternative sources of raw materials for the production of light aggregates. The main focus of our investigations is on construction and demolition waste and industrial by-products, which have so far only been used at a low level. Chemical analyses can be used to classify potential substances in the ternary diagram according to RILEY and to examine their basic suitability. However, the results show that the suitability of a raw material for the production of lightweight aggregates cannot be determined solely on the basis of the classification in the ternary diagram. Experimental investigations are necessary in any case. From the range of residual and waste materials investigated, the rhyolite fractions showed the best bloating properties. Without the addition of bloating agents, bloating values of 1.4 can be achieved. The addition of iron slurry to a reduction in the bloating temperature by about 100 °C, however, is associated with a slight reduction in the bloating value. With our investigations, we were able to show that an expansion of the raw material base for the production of lightweight aggregates is also possible beyond the use of classic, heterogeneous building rubble containing bricks.

This contribution to the journal “Gruppe. Interaktion. Organisation. (GIO)” delves into the critical role of Sustainable Development Goal 17 (SDG 17), “Partnership for the Goals,” in fostering interdisciplinary collaboration to further circular economy objectives. Aiming to address the existing research focus on isolated technical aspects within the circular economy, this study uses an expertise- and interaction-based foresight process to integrate perspectives from business, engineering, social sciences, and work and organizational psychology to unearth broader, interconnected challenges and solutions for the implementation of circular economy practices. Based on the pooled experience of experts within the foresight process, this contribution elucidates major challenges, ongoing issues, and prospective hurdles to be tackled by 2030 in circular economy, presenting an action plan centered on interdisciplinary cooperation and stakeholder engagement to advance labor conditions and continuous learning, sustainable and regenerative systems, minimize waste, and optimize resource efficiency. The collaborative action plan serves as a pivotal resource for the transformation task for researchers and practitioners, offers insights and strategic directions for implementing circular economy practices, and emphasizes collective responsibility and action in achieving global sustainability, all while aligning with the principles of SDG 17. The presented collaborative approach propels the discourse on sustainability forward, highlighting the potential of the circular economy in realizing a more sustainable world by 2030.

This study investigated two bioleaching strategies for removing heavy metals from three mine tailings fractions generated by flotation processes. On the one hand, bioleaching with microbial consortia of acidophilic mesophiles and moderate thermophiles efficiently extracted Co, Cu, Zn, and As, while the leaching of Pb was facilitated through the use of organic acids produced by a heterotrophic bacterium and a fungus. Approximately 100% Co, 68% Zn, 63% As, and 31% Cu were bioleached with acidophilic mesophiles from the barite tailings (BT) sample after 14 days, whereas for the barite concentrate (BC) sample the results showed about 100% Co, 70% Zn and As, and 45% Cu removal at the same period. The sulfide concentrate (SC) sample underwent bioleaching with both consortia, acidophilic mesophiles and moderate thermophiles over 28 days. Approximately, 67% of Co, 28% of Zn, 56% of As, 28% of Cu, and 6% of Mn were extracted from the sample using mesophiles, whereas the leaching efficiency with the moderate thermophiles was about 72% of Co, 50% of Zn, 28% of As, 36% of Cu, and 5% of Mn in 20 L bioreactors. On the other hand, bioleaching of Pb was explored using the bacterium Gluconobacter oxydans and the fungus Penicillium simplicissimum for the production of gluconic acid and citric acid, respectively. Additionally, besides glucose-based media, glycerol and crystal sugar were tested as alternative and cheaper carbon sources. The metabolic activity of P. simplicissimum allowed a maximum Pb leaching of 39-43% from the BT sample in 28 days in glycerol-based medium, while for the BC sample, the maximum Pb extraction was around 60% in glucose-based medium. A lower extraction of Pb was achieved with G. oxydans for both samples. The maximum extraction of 34% and 39% of Pb was reached within 7 days when glucose was used as the carbon source. Further optimization should address both the enhancement of metals removal and - especially for the organic acid bioleaching - the reduction of costs related to media formulation and fungal biomass production on a larger scale.

The increasing demand for lithium in lithium-ion battery (LIB) applications necessitates innovative recycling strategies. Combined pyrometallurgical–hydrometallurgical recycling has gained increased attention for lithium recovery from slags. One challenge in the technological advancement of recycling lithium from spent LIBs with lithium-nickel-manganese-cobalt-oxide cathodes (NMC), characterized by a Li–Al–Si–Ca–Mn–O slag system, lies in the distribution of lithium across multiple silicate and oxide phases. Hence, the goal of this work is to significantly enrich the lithium in the single target phase γ-LiAlO2 with thermodynamic-based optimization for tailored slag designs. This is achieved by coupling a sophisticated thermodynamic database and model reassessment related to practical NMC-type LIB slag system composition fields with Pareto optimization. Extensive experimental investigations are performed for model and design validations, and procedures for selecting the best phase candidates with individual lithium content are systematically presented. A strong nonlinear influence of CaO on the formation of the target product γ-LiAlO2 could be revealed, where the addition of SiO2 for lithium slagging needs to be limited to enrich lithium in the target phase. Higher amounts of added CaO and SiO2, such as both at 30 wt %, result in the undesired transfer of lithium into other Li-containing phases. Based on this approach, an artificial slag is computationally designed for the first time, where theoretically 100% of the lithium is trapped in γ-LiAlO2. After production of this slag and experimental analysis, it was found that 96% of lithium was transferred into γ-LiAlO2. This demonstrates the great potential of thermodynamics-based artificial slag design for enhancing lithium recycling efficiency in LIB recycling processes.

Pyro-metallurgical processing technology is widely used in the spent lithium-ion batteries recycling to recover valuable metals such as cobalt, nickel and copper, while lithium primarily remains in the slag. The effective valorization of slag, especially lithium recovery, constitutes a significant issue in contemporary pyrometallurgical processes due to the paucity of studies. This paper proposes a novel perspective by defining slag as an aggregate of engineered artificial minerals. Thus, not only the parameters of the beneficiation process can be studied to optimize the separation efficiency during treatment, but also the slag can be re-designed to optimize the carrier minerals of target elements and gangue mineral composition in the initial step with thermodynamic tools. In this paper, the engineering of artificial minerals (EnAM) method was applied to the slag design of the Li2O-CaO-Al2O3-SiO2-MnO system, and an initial attempt was made to apply EnAM method to the flotation study. A flotation study on enrichment effect of the target phase gamma-LiAlO2 from thermodynamic controlled slags is conducted.

Currently, MSWI (municipal solid waste incineration) ashes are predominantly landfilled, although they can have copper contents comparable to those of low-grade ores. Based on a previously published characterization of MSWI-BA, this paper presents investigations on the identification of potential collectors for copper recovery from MSWI-BA by flotation. The studies were conducted with single minerals (mainly copper oxide and sulfide) and synthetic slag components. Collector screening included thiourea-, thiophosphate-, and thiocarbamate-based collectors. In addition to commercial collector mixtures, pure ureas were also examined. At least one representative from each collector group was selected for the more in-depth studies: the thiourea S-n-dodecyle-iso-thiourea hydrochloride, the thiophosphate Danaflot 245, AERO 3473, and AERO MX-5160 as a mixture of a thiocarbamate and thiophosphates. Studies of the influence of collector concentration and pH were carried out with these. In addition, the contact angles of various metal oxides and the matrix composition with and without collector treatment were determined. Subsequently, flotation tests were carried out with mixtures of copper oxide and the individual matrix components (quartz, glass, cement, gypsum). AERO MX-5160 proved to be the most suitable collector, although alginic acid was added as a depressant due to a lack of selectivity towards gypsum.

The mining industry generates large amounts of tailings every year. The most common destination for the tailings is deposition in tailings storage facilities (TSFs), which can have enormous dimensions. The management and storage of such large volumes of material pose many challenges in terms of dam stability and immobilization of hazardous contaminants that represent human-health and environmental risks, particularly for sulfidecontaining materials. In addition, considerable amounts of precious and base metals can be lost in the tailings. Due to the economic value and growing industrial demand for precious and base metals, tailings may therefore be potential sources of secondary raw materials. This contribution investigates the flotation of pyriterich tailings, containing residual chalcopyrite, galena, and sphalerite, and high amounts of ultrafine particles. Flotation was used to recover the sulfide minerals and generate tailings with low sulfur content. The Cu-Pb-Znrich product could go to further treatment (e.g. (bio)hydrometallurgy) to recover the metals, while the low sulfur fraction could be used in the civil construction industry. Automated mineralogy (MLA) was used to provide quantitative mineralogical and textural data. Bench-scale experiments were performed by combining classic flotation and floc flotation (flotation of flocs of targeted minerals). Flotation of the material as received, as well as after classification into two fractions was performed. The samples as received and the coarser fraction (+37 & mu;m) underwent classic flotation, while the finer fraction (-37 & mu;m) was processed either by using the classic or the floc flotation approach. The flotation of the coarser particles provided higher sulfide recoveries, higher combined CuPb-Zn grades in the concentrate (3.66 %), cleaner residues (1.6 % S), faster flotation rates, and reduced reagent consumption. Likewise, the results from the fine particle flotation allowed lower S content in the residues (3.4 % S) as compared to the flotation of the original material. The results of the use of floc flotation for the finer fraction show an increase in the mass pull with a slight increase in the recovery of sulfides. Overall, the development of a route to process the tailings proved to be promising and the use of a two-route approach indicates advantages as compared to a single route.

Solid-state batteries (SSBs) are promising next-generation batteries due to their potential for achieving high energy densities and improved safety compared to conventional lithium-ion batteries (LIBs) with a flammable liquid electrolyte. Despite their huge market potential, very few studies have investigated SSB recycling processes to recover and reuse critical raw metals for a circular economy. For conventional LIBs, hydrometallurgical recycling has been proven to be able to produce high-quality products, with leaching being the first unit operation. Therefore, it is essential to establish a fundamental understanding of the leaching behavior of solid electrolytes as the key component of SSBs with different lixiviants. This work investigates the leaching of the most promising Al- and Ta-substituted Li7La3Zr2O12 (LLZO) solid electrolytes in mineral acids (H2SO4 and HCl), organic acids (formic, acetic, oxalic, and citric acid), and water. The leaching experiments were conducted using actual LLZO production waste in 1 M of acid at 1:20 S/L ratio at 25 °C for 24 h. The results showed that strong acids, such as H2SO4, almost completely dissolved LLZO. Encouraging selective leaching properties were observed with oxalic acid and water. This fundamental knowledge of LLZO leaching behavior will provide the basis for future optimization studies to develop innovative hydrometallurgical SSB recycling processes.

Imidazolium salts were prepared which possess 2-ethoxyethyl pivalate or 2-(2-ethoxyethoxy)ethyl pivalate groups as amphiphilic side chains with oxygen donors as well as n-butyl substituents as hydrophobic groups. The N-heterocyclic carbenes of the salts, characterized by 7Li and 13C NMR spectroscopy as well as by Rh and Ir complex formation, were used as starting materials for the preparation of the corresponding imidazole-2-thiones and imidazole-2-selenones. Flotation experiments in Hallimond tubes under variation of the air flow, pH, concentration and flotation time were performed. The title compounds proved to be suitable collectors for the flotation of lithium aluminate and spodumene for lithium recovery. Recovery rates up to 88.9% were obtained when the imidazole-2-thione was used as collector.

The high volume of mine tailings generated during mining activities poses significant worldwide storage risks. However, these tailings often contain valuable metals that can be recovered. Therefore, reprocessing mine tailings has emerged as a crucial strategy to assess secondary metals resources and mitigate storage risks. Furthermore, the mining industry’s extensive use of freshwater necessitates exploring alternative water sources. In this study, the leaching of base metals from mine tailings in chloride-based media was investigated. Approximately 52% Cu, 73% Zn, and 100% Pb were leached from the sample in the presence of HCl and NaCl. The substitution of freshwater with seawater yielded comparable results, demonstrating the potential of seawater as an alternative freshwater source that does not compromise leaching effectiveness. Additionally, 77% of Pb precipitated as PbSO4 from the pregnant leach solution. Through solvent extraction, approximately 100% Cu was recovered using LIX 984 as an extractant, and 71% Zn with D2EHPA. The use of Fe0 significantly reduced the co-extraction of Fe in the Zn recovery step. Overall, this study provides a potential route for reprocessing mine tailings, ensuring maximum leaching and efficient recovery of metals from sulfide mine tailings.

Resource efficiency, energy, and mobility transition are crucial strategies to mitigate climate change. The focus is on reducing the consumption of resources, especially energy and raw materials. While raw materials are the basis of our material world, their excessive consumption over the last decades has also contributed significantly to climate change. However, raw materials, and here especially metals, play a key enabling role as well for climate protection technologies, such as electro mobility, the hydrogen economy, and solar and wind power plants, and also for digitalization. Accordingly, it is necessary to make the use of raw materials much more resource-efficient than before and to use them as purposefully as possible instead of consuming them. Advanced circular economy systems and sophisticated recycling technologies build the backbone for the development of a resource efficient and sustainable society. Closed metal cycles contribute for a paramount share to this by securing relevant parts of the raw material supply for high-tech products and by reducing CO 2 emissions in their production at the same time. Interacting steps in multistage treatment processes by mechanical, chemical, and thermal unit operations are challenging but will give a competitive advantage for networks of industry and science that are able to handle that.

This work investigates the comprehensive recycling of graphite and cathode active materials (LiNi0.6Mn0.2Co0.2O2, abbreviated as NMC) from spent lithium-ion batteries via pretreatment and flotation. Specific analytical methods (SPME-GC-MS and Py-GC-MS) were utilized to identify and trace the relevant influencing factors. Two different pretreatment methods, which are Fenton oxidation and roasting, were investigated with respect to their influence on the flotation effectiveness. As a result, for NMC cathode active materials, a recovery of 90% and a maximum grade of 83% were obtained by the optimized roasting and flotation. Meanwhile, a graphite grade of 77% in the froth product was achieved, with a graphite recovery of 75%. By using SPME-GC-MS and Py-GC-MS analyses, it could be shown that, in an optimized process, an effective destruction/removal of the electrolyte and binder residues can be reached. The applied analytical tools could be integrated into the workflow, which enabled process control in terms of the pretreatment sufficiency and achievable separation in the subsequent flotation.

In the future, it will become increasingly important to recover critical elements from waste materials. For many of these elements, purely mechanical processing is not efficient enough. An already established method is pyrometallurgical processing, with which many of the technologically important elements, such as Cu or Co, can be recovered in the metal phase. Ignoble elements, such as Li, are known to be found in the slag. Even relatively base or highly redox-sensitive elements, such as Zr, REEs, or Ta, can be expected to accumulate in the slag. In this manuscript, the methods for determining the phase formation and the incorporation of these elements were developed and optimized, and the obtained results are discussed. For this purpose, oxide slags were synthesized with Al, Si, Ca, and the additives, P and Ti. To this synthetic slag were added the elements, Zr and La (which can be considered proxies for the light REEs), as well as Ta. On the basis of the obtained results, it can be concluded that Ti or P can have strong influences on the phase formation. In the presence of Ti, La, and Ta, predominantly scavenged by perovskite (Ca1−wLa2/3wTi1−(x+y+z)Al4/3xZryTa4/5zO3), and Zr predominantly as zirconate (Ca1−wLa2/3wZr4−(x+y+z)Al4/3xTiyTa4/5zO9), with the P having no effect on this behavior. Without Ti, the Zr and Ta are incorporated into the pyrochlore (La2−xCa3/2x−yZr2+2/4y−zTa4/5zO7), regardless of the presence of phosphorus. In addition to pyrochlore, La accumulates primarily in britholite-type La oxy- or phosphosilicates. Without P and Ti, similar behavior is observed, except that the britholite-like La silicates do not contain P, and the scavenging of La is less efficient. Lithium, on the other hand, forms its own compounds, such as LiAlO2(Si), LiAl5O8, eucryptite, and Li silicate. Additionally, in the presence of P, Li3PO4 is formed, and the eucryptite incorporates P, which indicates an additional P-rich eutectic melt.

Historical slags from primary Pb/Ag and Cu smelting can have high contents of valuable metal(loid)s. So far, there are hardly any studies that provide quantitative information on metal(loid) partitioning (deportment) between all slag phases based on automated mineralogy which is important for designing metal recovery from such slags. In this study, slags from the Kanstein Pb/Ag smelter, belonging to the Rammelsberg ore deposit, were studied by SEM-based automated mineralogy (here MLA), EPMA, and LA-ICP-MS on polished sections and by XRF and LA-ICP-MS on sieve fractions of bulk samples. The slags are rich in Fe (21-32 wt%), Zn (7.9-19 wt%), Pb (1.8-3.3 wt%), Cu (0.7-1.4 wt%) with slightly elevated concentrations of Co (309-586 ppm), Sb (155-459 ppm), Sn (84-204 ppm), Ag (19-115 ppm), In (18-64 ppm), Ga (15-25 ppm), Bi (2-20 ppm). A Ba-S-rich slag and a SiO2-rich slag can be distinguished; the first probably formed under more reducing conditions, at higher temperatures (> 1200 C) and without roasting. The weathering phases are the main carriers of all metal(loid)s (up to 45-94 % of total metal(loid) content in individual samples). Larger amounts of up to 13-83 % can be contained in glass (Ga, Sn, Zn, Fe, Ag, In, Co, Ge, Sb, Cu, Pb, Ni), pure metals and intermetallic compounds (Bi, Ag, Sb), sulphides (esp. sphalerite; Zn, Cu, Ag, In, Co), silicates (esp. fayalite; Ni, Co, Zn, Fe, Ga, Ag, In, Sn, Ge), or oxides (esp. wustite; Fe, Co, Ge, Zn, In, Ga), if their modal proportions in the slags are high enough. Due to the complex and variable metal deportment, processing of the entire slag using leaching or pyrometallurgy is most promising for recovery.

In the present work experiments for single mineral flotation against LiAlO2 and melilite s.s. were carried out for seven ionic liquids (ILs). From these, IL-1 with an imidazolium cation and a bromide anion and IL-7 with a pyridinium cation and a bromide anion were selected for further flotation experiments (dosage, pH). Flotation experiments were also conducted using naphthenic acid, a conventional flotation fatty acid-based collector, and FS-2, a commercial collector in order to compare the results with ILs. Moreover, the effects of different anions in the ILs on the flotation were evaluated and a significant influence on the hardness of anions was found on the flotation process. Finally, a pre-functionalization was also explored with modified cholesterol derivatives, comparing the effect of cholesterylsulfate and cholesterylphosphate on the flotation of LiAlO2 and melilite s.s. This study is vital for the further optimization of lithium recovery from the pyrometallurgical recycling path of lithium-ion batteries and the flotation of primary minerals such as aluminosilicates.