Recovery Of Critical Elements Research Articles

Stability of Crystalline Compounds in Slag Systems Mainly Composed of Li2O-SiO2-CaO-MnOx

The challenge of obtaining sufficient raw materials is a major concern when it comes to extracting lithium from spent lithium-ion batteries. One way to address this is through pyrometallurgical processing, which leaves undesirable elements such as lithium, aluminum and manganese in the slag. The engineered artificial minerals approach focuses on the effective recovery of critical elements. Different slag systems have been studied in the literature, and understanding the phase relationships in the Li2O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Li}_2{\ ext {O}}$$\\end{document}-SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {SiO}_2$$\\end{document}-CaO-MnOx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {MnO}_x$$\\end{document} system can lead to optimization of the recycling process. In this context, the stability of undesirable silicates can affect the maximum separation of Li from the slag. In order to contribute to the development of the Li recycling process, the stability of crystalline compounds was experimentally investigated in the present work for different slag compositions. The melted and solidified microstructures were characterized by SEM/EDX, EPMA, and XRD. Phase diagram data of binary and ternary systems were used to describe the solidification paths. As a result of solidification, crystals of Li2SiO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Li}_{2}\ ext {SiO}_{3}$$\\end{document} and LiMnO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {LiMnO}_2$$\\end{document} were observed in a matrix consisting of Ca3Si2O7\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Ca}_{3}\ ext {Si}_{2}\\hbox {O}_{7}$$\\end{document} and CaSiO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CaSiO}_{3}$$\\end{document}.

Engineering Compounds for the Recovery of Critical Elements from Slags: Melt Characteristics of Li5AlO4, LiAlO2, and LiAl5O8.

Engineered artificial minerals (EnAMs) are the core of a new concept of designing scavenger compounds for the recovery of critical elements from slags. It requires a fundamental understanding of solidification from complex oxide melts. Ion diffusivity and viscosity play vital roles in this process. In the melt, phase separations and ion transport give rise to gradients/increments in composition and, with it, to ion diffusivity, temperature, and viscosity. Due to this complexity, solidification phenomena are yet not well understood. If the melt is understood as increments of simple composition on a microscopic level, then the properties of these are more easily accessible from models and experiments. Here, we obtain these data for three stoichiometric lithium aluminum oxides. LiAlO2 is a promising EnAM for the recovery of lithium from lithium-ion battery pyrometallurgical processing. It is obtained through the addition of aluminum to the recycling slag melt. The high temperature properties spanning from below to above the liquidus temperature of three stoichiometric Li-Al-Oxides: Li5AlO4, LiAlO2, and LiAl5O8 are determined using molecular dynamic simulations. The compounds are also synthesized via the sol-gel route. The Li+ ion exhibits the largest diffusivity. They are quite mobile already below the liquidus temperature, i.e., for LiAlO2 at T = 1700 K, the diffusion coefficient of the lithium ion equals D = 3.0 × 10-9 m2 s-1. The other ions Al3+ and O2- do not move considerably at that temperature. The diffusivity of Li+ is largest in the lithium-rich compound Li5AlO4 with D = 32 × 10-9 m2 s-1 at 2500 K. The lower the viscosity, the higher the lithium content. The Li5AlO4 exhibits a viscosity of η = 2.2 mPa s at 1328 K which matches well with the experimentally determined 2.5 mPa s at this temperature. The viscosity of LiAlO2 at 1800 K is more than two times higher. These data sets can help to describe the melts on a microscopic level and understand how the melt properties will change due to gradients in the Li/Al concentration.

Circular And Sustainable: Evaluating Lithium-Ion Battery Recycling using a Combined Statistical Entropy and Life Cycle Assessment Methodology.

While there has been a growing interest on the concept of Circular Economy (CE), its correlation with sustainability remains controversial. In this work, the combination of Statistical Entropy Analysis (SEA) and Life Cycle Assessment (LCA) is proposed as a new methodology to evaluate recycling processes from the perspective of materials circularity and environmental impacts using a Li-ion battery recycling process as a case study. This work addresses the need of quantitative circularity indicators, as SEA evaluates the concentration of materials at a systems level, while LCA measures the environmental impact of recycling processes in comparison with virgin raw materials production. It was found that process optimization points can be found by simultaneously accounting for materials recovery and the LCA categories of global warming potential, ozone depletion and mineral resource scarcity. Furthermore, a strong correlation was found for the first time between the recovery of critical elements and the environmental impact of raw materials production. The proposed methodology thus offers a robust analysis of a product lifecycle that aids in its design and optimization from the CE perspective.

A two-stage process of alkali fusion and organic acid leaching for recovery of critical elements from coal fly ash

Coal fly ash (CFA) is a promising alternative source for critical elements. Most of the critical elements in CFA are associated with the aluminosilicate glassy phase, which hinders their ability to solubilize during acid leaching. In this study, critical elements (Li, Be, Rb, Sr, Zr, Nb, Cs, Hf, Ta, Ga, Ge, Se, Cd, and Tl) were recovered from CFA of Pingwei power plant in China by alkali fusion-organic acid leaching. The results showed that the leaching rate of critical elements after alkali fusion was higher than that of direct organic acid leaching. The leaching rate of total critical elements was 72.56% under the optimal conditions. Among them, the highest leaching rate of Li, Be and Ga was more than 90%, and the highest leaching rate of Ge, Se, Rb, Sr, Zr, Nb, Cd, Cs and Hf was 70%-90%. Characterization analysis revealed that the amorphous aluminosilicate and silica phases in the raw CFA were destroyed by alkali fusion, resulting in nepheline and soluble aluminosilicate phases which were easily dissolved by citric acid. This study provides theoretical basis and technical support for the extraction of critical elements from CFA.

Modelling of selective ion partitioning between ion-exchange membranes and highly concentrated multi-ionic brines

In recent years, the growing interest in the use of Ion-Exchange Membranes, in the treatment of highly concentrated multi-ionic brines for the selective recovery of critical elements, has prompted the research of fundamental models capable of predicting the IEMs selectivity towards like-charged species. Prior studies have proposed ion partitioning models limited to single-salt solutions that were validated only up to moderate salt concentrations. In this work, we developed a novel multi-ionic extension of the Manning counter-ion condensation model, aiming to predict the sorption selectivity of like-charged counter-ions. Furthermore, the peNRTL model was coupled with the extended Manning model to broaden its applicability range, encompassing membrane equilibrated with very highly concentrated solutions. Novel experimental ion sorption tests with single-salt and binary solutions including NaCl, KCl, MgCl2, and CaCl2 at high concentrations were performed with the commercial cation-exchange membrane Fumasep FKE-50. To the best of Authors’ knowledge, the proposed model for the first time successfully provided quantitative predictions of multi-ionic ion partitioning for all the systems investigated up to extremely high external salt concentrations. The outcomes of this work suggest a strong influence of the local non-electrostatic interactions on the activity coefficients in the membrane phase at high external concentration and highlight the key role of counter-ions hydration state in the condensation phenomenon.

Bio-metallurgical recovery of lithium, cobalt, and nickel from spent NMC lithium ion batteries: A comparative analysis of organic acid systems

With the increasing demand for lithium-ion batteries, key elements like lithium, graphite, cobalt, and nickel face heightened demand and classification as critical by the European Commission. This study investigates a bio-metallurgical approach for recovering these elements from NMC/C electrode material. The method leverages Aspergillus niger's acid production capacity. Lab experiments involved leaching pyrolyzed black mass using diverse multi-acid systems, including citric, DL-malic, gluconic, and oxalic acid. Parameters such as temperature, leaching time, solid-to-liquid ratio, and molasses as a reductant were varied. Nickel and cobalt recovery rates were modest, with highest rates (13% for Ni, 25.8% for Co) in DL-malic and gluconic acid-rich setups. Maximum lithium recovery (87.9%) occurred in a citric-rich medium. Analysis revealed organo-metallic components in solid residues and formed precipitates, implying oxalic acid's role in inhibiting recovery. Therefore, optimization of acid generation is crucial for effective bio-metallurgical recovery. In summary, this study highlights the potential of Aspergillus niger-mediated bio-metallurgical processes with organic acid mixtures for sustainable recovery of critical elements from spent lithium-ion batteries. The findings contribute crucial insights into optimizing leaching parameters and underscore the significance of bioleaching in addressing the demand for key battery materials. This work has important implications for advancing eco-friendly e-waste recycling practices and aligns with the principles of resource conservation and circular economy in the energy storage sector.

Identifying the circularization opportunities for organic wastes generated in a Mediterranean region

AbstractUnderstanding the extent and characteristics of biomass resources is important for managing it effectively within the bioeconomy and leveraging biomass towards the highest value uses or those which are most appropriate. To this end, a large regional study was conducted to characterize the main physicochemical characteristics of common biomasses and identify potential limitations to use or opportunities for. Valencia is fourth most populous autonomous region of Spain, having a large importance for the European vegetable and citrus product markets, among others. Across 164 municipalities, 625 samples were characterized for contents of organic matter, total nitrogen, total phosphorus, pH, electrical conductivity, and polyphenol contents, and 224 samples were characterized for metal and metalloid contents. The different biomass types included in the study were expert-classified into a total of 54 biomass subcategories. Overall, nutrient contents were the parameter most associated with waste type, while electrical conductivity had the highest variability within groups. Considering all the samples, nutrient contents were sufficient to reach established minimums for marking as an EU-labelled fertilizing product in 479/625 cases, and pertinent limits on heavy metal contents were exceeded in 20/224 cases. The highest polyphenol contents were found in the pomegranate and citric wastes, which were substantially higher than in the organic wastes from olive oil and wine production. Machine learning techniques (k-means and hierarchical clustering analysis) applied to the datasets showed that biomasses were best classified into two groups based on pH, electrical conductivity, organic matter, and N, P, and Na contents, and three groups based on metal and metalloid contents. The summary data are presented in appendices for regional and European nutrient budgeting and modelling use. Based on the analyzed properties, the most appropriate uses can be identified, whether for transformation in biological processes, energy generation, recovery of critical elements, or extraction of high value compounds.

Recovery of Critical Elements (Dysprosium and Ytterbium) from Alkaline Process of Indonesian Zircon Tailings: Selective Leaching and Kinetics Study

Recovery of Critical Elements (Dysprosium and Ytterbium) from Alkaline Process of Indonesian Zircon Tailings: Selective Leaching and Kinetics Study

Grand challenges in recovery of critical elements from end-of-life lithium-ion batteries (LIBs)

Grand challenges in recovery of critical elements from end-of-life lithium-ion batteries (LIBs)

Nanoscale Mg-Depleted Layers Slow Carbonation of Forsterite (Mg2SiO4) When Water Is Limited

Passivation of silicate surfaces by accumulated reaction products is an obstacle to efficient CO2 mineralization. In this study, we investigate a unique passivation effect during the carbonation of the basalt mineral forsterite (Mg2SiO4) in humid supercritical CO2 (50 °C, 90 bar). Using in situ high-pressure infrared spectroscopy, we demonstrate that dissolution of forsterite into a thin water film slows significantly after reaction for ≈24 h, even under far-from-equilibrium conditions. 29Si magic angle spinning nuclear magnetic resonance spectroscopy detects a highly polymerized amorphous silica at this stage. On the basis of transmission electron microscopy and energy dispersive X-ray spectroscopy, we show that the silica is present as a Mg-depleted layer that is just 2–3 nm thick on the reacted forsterite particles. The decrease in the level of forsterite dissolution in the presence of an extraordinarily thin Mg-depleted layer can be strongly linked to properties of the thin fluid film at the surface, highlighting the importance of water during mineral carbonation. This study furthers our understanding of silicate mineral carbonation under select low-water, humidified fluid conditions relevant to basaltic geologic reservoirs, recovery of critical elements by carbonation of mafic ores, and sequestration of atmospheric CO2 by enhanced rock weathering.

Sustainable recovery of critical elements from seawater saltworks bitterns by integration of high selective sorbents and reactive precipitation and crystallisation: Developing the probe of concept with on-site produced chemicals and energy

The availability of raw mineral resources containing elements included in the Critical Raw Materials (CRMs) list is a growing concern for the European Union. Sea mining has been identified as a promising secondary source. In particular, brines obtained in solar saltworks (bitterns) contain relevant amounts of valuable CRMs such as Mg(II), B(III), other alkaline/alkaline earth metals (Rb(I), Cs(I), Sr(II)) and transition/post-transition elements (Co(II), Ga(III), Ge(IV)). However, the low concentration of some of these elements (µg/L) requires an effort to develop recovery routes that are sustainable and economically feasible where the required chemicals and energy are produced on-site from the saltworks bitterns (i.e. HCl and NaOH). Even the conventional recovery processes such as ion exchange, sorption and precipitation, which have proved to be competitive for metals recovery, are challenged in the case of Trace Elements (TEs). This work studies the recovery of TEs included in the CRMs list from saltworks bitterns after ion exchange processes. First, batch crystallisation and reactive precipitation were tested for some target elements in single-component solutions: Sr(II), Co(II), Ga(III), Ge(IV) and B(III). Then, the experiments were carried out with multi-component synthetic solutions assuming different scenarios of bittern streams coming out a selective extraction stage using sorption and ion exchange processes. The targeted elements were recovered except for Ge(IV), where alternative routes need to be evaluated, as its precipitation involves the use of tannic acid or sulphide solutions that could not be produced from the bitterns. However, a further concentration step would be necessary to achieve element concentrations closer to the mineral phases saturation. Moreover, model simulations were performed using the PHREEQC program, which provided a good prediction of the experimental trends obtained in most cases.

The Effect of Physical Separation and Calcination on Enrichment and Recovery of Critical Elements from Coal Gangue

Critical metallic elements in coal gangue have great utilization potential, especially due to the current shortage of these metals. This paper focused on examining the feasibility of physical separation (screening and float-sink tests) and calcination treatment for the enrichment of critical elements (Li, Ga, and rare earth elements plus yttrium (REY)) from coal gangue. The impacts of these enrichment methods on the acid leaching recovery of these elements were then studied. Screening tests indicated that Li and Ga were enriched in >0.125 mm size fraction and the content of REY was highest in <75 μm size fraction. Float-sink tests showed that high-density fractions were enriched in Li and Ga, and low-density fractions were enriched in REY. Physical separation cannot significantly improve the leaching rate of Li, Ga, and REY. Notably, Li, Ga, and REY were enriched significantly, and their acid leaching recoveries were increased by 54~68% after calcination under 400 °C. Sequential chemical extraction tests showed that the majority of insoluble Li, Ga, and REY was converted into soluble forms at the above temperature, which is attributed to the formation of amorphous metakaolinite and the decomposition of organic matter. Based on the results, a conceptually combined flowsheet was proposed for the extraction of Li and Ga from coal gangue.

Selective precipitation of rare earth and critical elements from acid mine drainage - Part II: Mechanistic effect of ligands in staged precipitation process

Recovery of critical elements from secondary resources, such as acid mine drainage (AMD), has been deemed a potential path to support the raw materials needed to support the increasing high-tech and green energy developments. The precipitation patterns of critical elements in AMD treatment ponds differ when NaOH and Na2CO3 are used. In order to determine the reason for the difference in precipitation pattern of REEs and critical elements in these two conditions as well as the prospects of selective recovery of these elements, surface charge, particle size, and formation of the precipitates obtained from the treatment of AMD using a 3-stage precipitation process were studied. It was shown that the REEs surface complexation and co-precipitation with Al precipitates are unlikely. Particle size analysis concluded that the Al and Co-Mn precipitates tend to agglomerate after the initial precipitation of very fine particles. However, no agglomeration of the REE precipitates was observed.

Distribution and preconcentration of critical elements from coal fly ash by integrated physical separations

With the rising demand and exhaustion of conventional ores of critical elements, recovery of critical elements from metalliferous coal ash is regarded as a stable alternative source. The recovery procedures of critical elements include preconcentration, activation, extraction, enrichment and purification. Among them, preconcentration of critical elements influence the subsequently extraction efficiency and energy consumption directly. The enrichment characterizations of critical elements vary among different particle size, magnetic, density and host minerals in combustion ash and worthy of further elucidated. The fly ash was collected from a full-scale circulated fluidized boiler in Xinganmeng, Inner Mongolia, China, where the coal contains elevated concentrations of Ga, Ge, and other critical elements. Various physical separations, i.e., particle size, magnetic, and density separations combined with desilicication were conducted to investigate the technical feasibility of physical separations of critical elements from coal ash. The chemical components, mineralogical compositions, and trace element concentrations were measured by XRF, XRD, ICP-MS, respectively. Results show that amorphous glass is the primary component in fly ash (49.8%), the mainly mineral phases are composed of mullite (39.2%), hematite (4.1%), and quartz (5.2%) in the selected fly ash. Critical elements are mainly enriched in amorphous glass, fine particle size (<96 μm), non-magnetic, and moderate density (2.4–2.8 g/ml) fractions. The preconcentration behavior of critical elements are determined by their physico-chemical properties, host minerals, transformation characteristics during combustion. Integrated physical separation combined with desilicication processes are regarded as the promising approach for critical elements recovery from fly ash.

Optimizing Battery Manufacturing Decision-Making Using Lifecycle Assessment

The global demand for batteries is projected to increase by 25% annually, reaching ~2,600 GWh in 2030. As the world shifts to electric mobility, particularly EVs, to reduce greenhouse gas emissions and mitigate the effects of climate change, research efforts on recycling and recovery of critical elements from lithium-ion batteries (LIB) have increased, leading to the development and advancement of technologies that utilize conventional and state-of-the-art recycling processes. Hydrometallurgical processing continues to be the most widely used method for recycling metals from LIB, but over the last few years, direct recycling has gained attention as a more sustainable and efficient process. While direct-recycling technologies are promising, most direct-recycling processes remain small in scale and are costly in terms of the equipment needed to recover metals from spent LIB. As such, materials selection in battery manufacturing and overall battery chemistry and design have become increasingly important. The development of new battery chemistries that are less reliant on critical metals, such as cobalt, has become a prominent area of interest, and material criticality has become a major driver for battery recycling and reuse.Battery manufacturing is at a crossroads of decision-making with growing demands that overshadow available resources, reliance on imports, challenges in developing sustainable recycling processes that achieve increasingly stringent materials specifications, changing environmental regulations, and the need to identify and reduce potential environmental impacts for this growing waste stream. The best solutions will engage stakeholders from a variety of specialties who consider the battery lifecycle and the impact of each decision on the entire battery lifecycle. This presentation highlights one set of challenges - tradeoffs in materials selection with environmental regulatory compliance burdens and risks.

E-waste mining and the transition toward a bio-based economy: The case of lamp phosphor powder.

Replacement of conventional hydrometallurgical and pyrometallurgical process used in E-waste recycling to recover metals can be possible. The metallurgical industry has been considered biohydrometallurgical-based technologies for E-waste recycling. Biorecovery of critical metals from phosphor powder from spent lamps is an example of transition to a bio-based circular economy. E-waste contains economically significant levels of precious, critical metals and rare-earth elements (REE), apart from base metals and other toxic compounds. Recycling and recovery of critical elements from E-waste using a cost-effective technology are now among the top priorities in metallurgy due to the rapid depletion of their natural resources. This paper focuses on the perceptions of recovery of REE from phosphor powder from spent fluorescent lamps regarding a possible transition toward a bio-based economy. An overview of the worldwide E-waste and REE is also demonstrated to reinforce the arguments for the importance of E-waste as a secondary source of some critical metals. Based on the use of bioprocesses, we argue that the replacement of conventional steps used in E-waste recycling by bio-based technological processes can be possible. The bio-recycling of E-waste follows a typical sequence of industrial processes intensely used in classic pyro- and hydrometallurgy with the addition of bio-hydrometallurgical processes such as bioleaching and biosorption. We use the case study of REE biosorption as a new technology based on biological principles to exemplify the potential of urban biomining. The perspective of transition between conventional processes for the recovery of valuable metals for biohydrometallurgy defines which issues related to urban mining can influence the mineral bioeconomy. This assessment is necessary to outline future directions for sustainable recycling development to achieve United Nations Sustainable Development Goals.Graphical

Easy recovery of Li-ion cathode powders by the use of water-processable binders

The continuous growth of the lithium battery market calls for strategies that simultaneously target high energy/power system performance, sustainable manufacturing processes, exploitation of green raw materials and easy recycling of batteries. Here we propose the use of pullulan, a water-soluble and biodegradable polymer, as a binder for the production of LIB cathodes based on Li(Ni0.5Mn0.3Co0.2)O2 (NMC532). We aim to contribute to the development of a sustainable LIB value chain, where devices are designed in view of the recovery of critical elements at their end-of-life. In fact, the aqueous manufacturing of the cathodes represents a green, cheap and easy procedure to produce electrodes with reduced environmental impact and recover Li-ion cathode powders from spent LIBs. The cathodes exhibited up to 135 mAh g−1 of composite material and 167 mAh g−1 of NMC, and excellent cycling stability over 500 cycles along with good capacity retention at high C-rates. NMC and carbon black were directly recovered by dissolving the binder through a water-fed aerograph in less than 2 min. Notably, the waste waters used to wash and recover the NMC-carbon powders were biodegradable, which is of great importance to close the “sustainability chain” loop.

Resources from coal beneficiation waste: Chemistry and petrology of the Ayrshire coal tailings ponds, Chandler, Indiana

Tailings (refuse) material, a mixture of fine coal and rock from the beneficiation of high volatile C bituminous Pennsylvanian Illinois Basin coals, was recovered from the tailings pond near the site of the former preparation plant. The material has widely varying concentrations of some elements, such as Sn, which might reflect non-coal contamination of the product stream at any point from mining and beneficiation of the coal to disposal of the waste product. The rare earth elements have a strong M-type enrichment. Concentration of the rare earths is below what would normally be considered to be an economic grade. The mix of coal and REE-lean rock, though, implies that the resource must be examined with an eye towards the recovery of critical elements, not just for the reconnaissance bulk characterization, as was done here. Despite the low concentration of REE and other critical elements, factors such as the ease of moving the comminuted, near-surface material and its proximity to highway, rail, and river transport implies that such resources must be carefully examined; not simply dismissed because the grade is below a cutoff level developed for coal, not mixed rock + coal.

Copper slag as a potential source of critical elements - A case study from Tsumeb, Namibia

SYNOPSIS At a time of resource consumption, it is important to study the chemical composition of mining and metallurgical wastes to prevent the dissipative loss of metals and metalloids from the mining value chain. In particular, the recovery of critical elements from wastes is an option to increase the resources of such materials that are economically significant and have an overall supply risk. In this paper we report on the chemical composition, in particular the critical element content, of granulated slag originating from historical smelting activities in the Tsumeb area, Namibia. Laboratory-based inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray fluorescence (XRF) analyses as well as portable X-ray fluorescence (pXRF) demonstrate that the slags are on average enriched in base metals (Cu 0.7 wt%, Pb 2.7 wt%, Zn 4.7 wt%), trace metals and metalloids (Cd approx. 50 mg/kg, Mo approx. 910 mg/kg) as well as critical elements (As approx. 6300 mg/kg, Bi approx. 3 mg/kg, Co approx. 200 mg/kg, Ga approx. 100 mg/kg, In approx. 9 mg/kg, Sb approx. 470 mg/kg). While metals and metalloids such as As, Mo and Pb can be determined reliably using pXRF instruments, the technique has inherent limitations in evaluating the contents of certain critical elements (Ga, Sb). However, there are positive correlations between the As, Mo, and Pb contents determined by pXRF and the Ga and Sb contents obtained through ICP-MS and XRF. Thus, quantitative pXRF analysis for As, Mo, and Pb allows calculation of Ga and Sb abundances in the slags. This work demonstrates that pXRF analysers are a valuable tool to screen smelting slags for their chemical composition and to predict the likely contents of critical elements. Keywords: base metal slag, portable XRF, critical elements, secondary resource.

Li-Distribution in Compounds of the Li2O-MgO-Al2O3-SiO2-CaO System—A First Survey

The recovery of critical elements in recycling processes of complex high-tech products is often limited when applying only mechanical separation methods. A possible route is the pyrometallurgical processing that allows transferring of important critical elements into an alloy melt. Chemical rather ignoble elements will report in slag or dust. Valuable ignoble elements such as lithium should be recovered out of that material stream. A novel approach to accomplish this is enrichment in engineered artificial minerals (EnAM). An application with a high potential for resource efficient solutions is the pyrometallurgical processing of Li ion batteries. Starting from comparatively simple slag compositions such as the Li-Al-Si-Ca-O system, the next level of complexity is reached when adding Mg, derived from slag builders or other sources. Every additional component will change the distribution of Li between the compounds generated in the slag. Investigations with powder X-Ray diffraction (PXRD) and electron probe microanalysis (EPMA) of solidified melt of the five-compound system Li2O-MgO-Al2O3- SiO2-CaO reveal that Li can occur in various compounds from beginning to the end of the crystallization. Among these compounds are Li1−x(Al1−xSix)O2, Li1−xMgy(Al)(Al3/2y+xSi2−x−3/2y)O6, solid solutions of Mg1−(3/2y)Al2+yO4/LiAl5O8 and Ca-alumosilicate (melilite). There are indications of segregation processes of Al-rich and Si(Ca)-rich melts. The experimental results were compared with solidification curves via thermodynamic calculations of the systems MgO-Al2O3 and Li2O-SiO2-Al2O3.