List Of Critical Raw Materials Research Articles

Selective recovery of boron, cobalt, gallium and germanium from seawater solar saltworks brines using N-methylglucamine sorbents: Column operation performance

The European Union (EU) identified a list of Critical Raw Materials (CRMs) crucial for its economy, aiming to find alternative sources. Seawater is a promising option as it contains almost all elements, although most at low concentrations. However, to the present, the CRMs' recovery from seawater is technically and economically unfeasible. Other alternatives to implement sea mining might be preferred, such as reverse osmosis brines or saltworks bitterns (after sodium chloride crystallisation). The CRMs' extraction in a selective way can be achieved using highly selective recovery processes, such as chelating sorbents. This study focuses on extracting Trace Elements (TEs) from solar saltworks brines, including boron, cobalt, gallium and germanium, using commercial N-methylglucamine sorbents (S108, CRB03, CRB05). The application of these sorbents has shown potential for boron recovery, but their selectivity for cobalt, gallium, and germanium requires further investigation. This research aims to assess these sorbents' kinetics and column mode performance for TEs recovery from synthetic bitterns. Boron and germanium were rapidly sorbed, reaching equilibrium (>90 %) within 1 h, except for S108, which took 2 h. In column mode, 20–25 pore volumes of bittern were treated to remove boron and germanium, but competition from other elements reduced treatment capacity. An acidic elution (1 M hydrochloric acid) allowed to elute them (>90 %), reaching concentration factors for germanium and boron of 35 and 11, respectively, while cobalt and gallium had less affinity for the sorbents. In addition, the experiments performed were fitted by a mass transfer model to determine the equilibrium constants and selectivities. Therefore, bittern mining has been proven as a secondary/alternative source to obtain CRMs, which can lead the EU to a position in which its dependence on other countries to obtain these raw materials would be decreased.

Electrochemical Oxidation of Cobalt at a Platinum Electrode in a Chloride Medium

Cobalt is a highly important metal that is widely used in lithium-ion batteries, cemented carbide, magnetic materials, chemical, and medical industries. The current global cobalt reserves (in total around 6.9 million tons) are unevenly distributed mainly between the Democratic Republic of Congo (48%) and Australia (21%) [1]. One of the main sources of cobalt is nickel production where Co is as a byproduct. Nevertheless, research related to cobalt extraction from both primary or secondary resources must be accelerated to address the current imbalance between supply and demand, that has resulted in cobalt being classified as highly critical by the EU [2]. Currently, primary and secondary raw materials are refined using pyro-hydrometallurgical or hydrometallurgical processing routes, followed by e.g. cobalt crystallization, or electrowinning. Battery grade cobalt salts can be further subjected for calcination to form battery grade oxides. In the current study, we investigate a novel approach of electrifying metallurgy - attempting for direct electrochemical cobalt recovery as cobalt oxide from a hydrometallurgical chloride based process solution.Potentiostatic electrolysis was performed in synthetic cobalt chloride solution, mimicking the industrial concentrations. SEM and EDX were used for microstructural characterization and determination of sample compositions, respectively. Cyclic voltammetry (CV) was also carried out to understand the anodic behavior of cobalt on the Pt electrode. CV studies suggested the formation of different cobalt-containing phases and the obtained precipitates in potentiostatic experiments were identified as Co3O4 and CoOOH. However, the precipitate composition was strongly dependent on the conditions of electrolysis, such as potential, temperature, and pH. At the highest studied potential (1150 mV vs. Ag/AgCl) the precipitate obtained had a saturated black color indicating desired formation of Co3O4, while at lower potentials the brown colour indicated dominance of other phases. The microstructure of the electrodes due to different potentials was investigated by SEM, indicating also morphology changes as a function of recovery potential. EDX analysis suggested that the precipitates recovered included not only cobalt and oxygen but also traces of chloride ions.Overall, this study highlights the possibility of cobalt recovery in oxide form in a chloride medium as an alternative method for the recovery of cobalt from industrial process solutions. The proposed approach can be suggested as an alternative to the traditional process of crystallization or electrowinning. In addition, cobalt obtained in a form of oxide is an important class of materials characterized by good electrochemical, catalytic, and optical properties and can be used as a final product in a variety of applications if quality requirements can be achieved. Acknowledgment The ENICON project (https://enicon-horizon.eu/) has received funding from the European Union’s Framework Program for Research and Innovation Horizon Europe under Grant Agreement No. 101058124 References Rahimpour Golroudbary, S.; Farfan, J.; Lohrmann, A.; Kraslawski, A. Environmental Benefits of Circular Economy Approach to Use of Cobalt. Global Environmental Change (2022) 76, doi:10.1016/j.gloenvcha.2022.102568.Blengini, G.A.; EL Latunussa, C.; Eynard, U.; Torres de Matos, C.; Wittmer, D.; Georgitzikis, K.; Pavel, C.; Carrara, S.; Mancini, L.; Unguru, M.; et al. Study on the EU’s List of Critical Raw Materials (2020) Final Report., doi:10.2873/904613.

Towards Sustainable Lithium-Ion Battery Anodes: Addressing the Critical Need for Graphite Recycling

Graphite is the predominant anode material for all lithium-ion batteries (LIB) currently manufactured. However, despite comprising between 10 and 20 percent of a LIB's weight, graphite is not typically recycled. Graphite has a wide variety of applications outside of LIB, but the value of use in other applications is very low, so only recycling graphite back into anode material will be economically viable. Since graphite is such a stable substance, it should in theory be highly desirable for direct recycling back into anode material. As a result of this stability, several sources of graphite can become intermixed and impossible to separate later, posing a traceability issue. As is the case with cathode materials, there is currently no policy mandating the recycling of graphite.At the same time, graphite (natural) is on the EU's list of critical raw materials (98% imports), and the global supply of graphite for anode materials is entirely dominated by China. The production of natural and synthetic graphite has significant environmental costs, with recent studies indicating a CO2 footprint in the range of 10 to 30 kgCO2/kg graphite, which is significantly higher than what was previously reported in LCA literature. There is a need to establish processes for recycling this valuable material, as its demand is expected to increase dramatically over the next decade.In recent years, Vianode has developed a one-of-a-kind method for converting graphite concentrates from LIB production scrap and end-of-life batteries (black mass) back into anode-grade graphite for use in new LIB. Using a high temperature purification stage, impurities and flaws in graphite can be effectively removed and a purity of over 99.99% can be attained. Cell testing reveals that recycled graphite can achieve the same properties as virgin graphite, including outstanding reversible capacity, first cycle efficiency, fast charge capability, and cycle life. The results indicate that graphite recycling should be implemented as soon as possible to lessen the EU's reliance on graphite imports and significantly reduce the environmental impact of anode materials in LIB.

The properties of laser-clad coatings made of NiCrBSi alloy and recycled tungsten carbides

Tungsten carbide hard metals are one of the most known and successful powder metallurgical products used in environments where severe wear conditions prevail. Since tungsten belongs to the list of critical raw materials for the European Union (EU), its recycling is highly desirable. In this paper, recycled tungsten carbide powders fabricated by the zinc-reclaim process where mixed with NiCrBSi matrix and deposited with one-step laser cladding using a coaxial powder feeding on mild steel substrates. Prepared clads were tested in low-stress rubber wheel abrasion tests and compared with clads produced from commercial macrocrystalline (WC) and cast and crushed eutectoid WC/W2C reinforced clads. The results showed that recycled WC induced porosity in clads when produced with ‘production’ laser cladding parameters due to small carbide size resulting in poor wear performance. When laser-clad with lower heat input and productivity, pore-free clads with excellent wear performance were obtained.

From sewage sludge ash to a recycled feed phosphate – digestibility of precipitated calcium phosphate in broiler chickens and growing pigs

Today, EU is largely (∼92%) dependent on the import of phosphates as most mines are located outside Europe. Because of the limited availability, phosphorus (P) is included on the list of Critical Raw Materials. Precipitated calcium phosphate (PCP) recovered from sewage sludge ash is a novel and sustainable option to replace mined P as raw material in feed phosphates, e.g. monocalcium phosphate (MCP) or dicalcium phosphate, but the digestibility has not yet been tested in vivo. The aim was therefore to determine PCP and MCP apparent ileal digestibility (AID) of P in broiler chickens and apparent (ATTD) and true (TTTD) total tract digestibility of P in growing pigs. A chicken study comprised 240 Ross 308 chickens that were housed in groups of eight from day 21 to day 28. Five diets were used, a basal diet and two test diets, which contributed either 0.075% (low) or 0.150% (high) additional P for each of the test sources (MCP and PCP). The basal and test diets were composed to achieve increasing levels of P and AID was calculated with regression analysis. In the pig study, eight individually housed pigs were used in a change-over study with two experimental periods. The pigs were fed a basal P-free diet in a preperiod to be able to estimate endogenous P losses and then two different diets in two periods using a change-over design, where MCP and PCP were the only P source, providing in total 0.33 (basal diet), 4.42 (MCP) and 3.53 (PCP) g kg-1P, respectively. The AID of P in PCP and MCP for chickens was 58.4 and 75.1% (P = 0.166). The ATTD and TTTD of P in PCP for pigs were 58.4 and 67.2%, respectively, which was lower (P < 0.001) than the corresponding values for MCP (82.1 and 89.1%), respectively. The digestibility of calcium (Ca) did not differ in the chicken diets with high inclusion levels of PCP and MCP (54.7 and 55.3%, respectively, P = 0.535), but was lower for PCP than MCP in the pig study (57.8 and 70.8% respectively, P = 0.001). In conclusion, the digestibility of P in PCP for chickens did not differ from conventional MCP, whereas for pigs, it was lower, but could be a viable alternative to other common sources of P.

Critical Raw Materials recovery potential from Spanish mine wastes: A national-scale preliminary assessment

In Spain, due to its important mining past, there are many abandoned mine waste facilities. This study evaluates the potential of Spanish mine wastes for the recovery of critical and strategic raw materials and other elements of economic relevance. For this purpose, 20 mine waste facilities have been selected in different parts of Spain based on criteria such as tonnage, element content or metal market price. Surface samples were taken at the facilities, considered representative of these, for subsequent granulometric, mineralogical and chemical analysis. The grain size data were obtained by standard sieving (ASTM 5000), while the mineralogy was obtained by X-ray Diffraction (XRD). For chemical characterization, Wavelength Dispersion X-ray Fluorescence Spectrometry (WDXRF) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) were used to analyze 38 chemical elements (Be, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, Sn, Sb, I, Cs, Ba, La, Ce, Nd, Sm, Hf, Ta, W, Tl, Pb, Bi, Th and U), many of them included in the European Union’s list of Critical Raw Materials (CRMs). In addition, leachate data from mine wastes in the Iberian Pyritic Belt were analyzed to assess their bioleaching potential. The calculated enrichment factors (EF) indicate that some critical elements, as well as others with strategic and economic interest, are highly enriched in the wastes, including Sb, Bi, As, Pb, Cu, Ag, Zn, Cd, Sn, Se and Th. The most promising facilities with the highest recovery potential are located in the historic Riotinto and Tharsis mines (both in Huelva, Iberian Pyrite Belt) and the Rubiais mine in Lugo, whose tailings could contribute up to 3.2 billion dollars gross, according to the current market metal prices. This paper aims to provide a first step to promote mine waste recycling and circular mining in Spain, an initiative that would also help to mitigate the environmental damage derived from abandoned mine wastes.

Lightweight design versus raw materials criticalities

The 4th list of Critical Raw Materials has been published by the European Commission at the beginning of September 2020. A trend of increased criticality is observed for all raw materials in 2020 compared to 2017 and four new critical raw materials appeared (bauxite, titanium, lithium, and strontium) that pose new restrictions in lightweight design of metallic components. Based on a materials selection methodology developed in literature to face such emerging issues, the criticality assessment of light alloys is evaluated and rationally considered in lightweight design by using a trade-off material selection strategy. A simplified case-study is proposed as an example.

Occurrences of Niobium and Tantalum Mineralization in Mongolia

Niobium and tantalum are two rare metals that have similar physical and chemical properties and occur together in nature. They are considered to be strategic and critical materials for the economy and national security of many industrial countries. Both elements are on the 2022 List of Critical Minerals of the USA as well as on the European Union’s List of Critical Raw Materials. They rarely substitute for common elements in rock-forming minerals but are essential components in a range of rare minerals, particularly oxides and subordinately silicates. The economically important minerals are oxides. The columbite-tantalite and pyrochlore-microlite groups are the most common Ta- and Nb-bearing minerals. In Mongolia, primary niobium and tantalum mineralization includes two main types. The first type is mineralization associated with alkaline to peralkaline granites, pegmatites and syenites whereas the second type is related to the lithium-fluorine-rich peraluminous granites and related rocks (pegmatites and ongonites). The host rocks of both types of mineralization are the fractionated felsic rocks, which contain the primary magmatic ore assemblages associated with fractionation of magma rich in rare metals. Both assemblages were subsequently overprinted by the late magmatic to hydrothermal fluids, which remobilized and enriched the original mineralization. The newly formed ore mineral assemblages display complex replacement textures. In the case of peralkaline felsic rocks the processes produced the mineralization of Zr, Nb, heavy REE, Y, U, Th and Ta whereas peraluminous Li-F felsic rocks contain mainly mineralization of Sn, W, Ta, Li, and Nb. Mongolia hosts several promising occurrences of both types of Nb-Ta mineralization. However, they have not yet been sufficiently explored. Currently, the most promising is the occurrence in the Devonian Khalzan Buregtei peralkaline granites in northwestern Mongolia, where Nb-Ta is associated with REE and Zr mineralization. Mesozoic carbonatites of southern Mongolia do not host significant Nb and Ta mineralization.

Modeling coking coal indexes by SHAP-XGBoost: Explainable artificial intelligence method

Coking coal is still on the list of critical raw materials in many countries since it is the main element integrated into the blast furnace. While the energy consumption and steelmaking efficiency in the furnace depends on the coke quality, understanding and modeling coking indexes based on their coal parent properties would be a substantial approach for the steelmaking industry. As an innovative approach, this short comminucation has been considered explainable artificial intelligence (XAI) for modeling coal coking indexes (Free Swelling index “FSI” and maximum fluidity “Log (MF)”). XAIs can convert black-box models into human basis systems and develop a significant learning performance and estimation accuracy. SHapley Additive exPlanations (SHAP), as one of the most recently developed XAI models in combination with eXtreme gradient boosting (XGBoost), were used to model coal samples from Illinois, USA. For the first time, FSI and Log (MF) treat as ordinal variables for modeling. Modeling outcomes relieved that SHAP-XGBoost could accurately show interdependency between features, demonstrate the magnitude of their multi relationships, rank them based on their importance, and predict the coking index quite accurately compared with conventional machine learning methods (random forest and support vector regression). These significant results would be opened a new window by applying XAI tools for controlling and modeling complex systems in the energy and fuel sectors.

Роль критически важных сырьевых материалов в условиях экономической неопределенности: опыт ЕС

The demand for minerals is set to increase in the future due to the global competition, industrialization in the developing countries, digitalization of the developed economies as well as the social and economic shocks in the course of a deep transformation of the international economic order. Dependence on the critical raw materials may soon replace the dependence on oil and gas. A reliable and sustainable supply of both primary and secondary raw materials, especially of the critical raw materials for the key technologies and strategic sectors such as the renewable energy, electric mobility, digital technologies, space and defense, is a prerequisite for achieving national security and independence. The new EU Industrial Strategy addresses security and sustainable development and calls for active action on critical raw materials and creation of sector-specific raw material alliances. This EU policy pursues a strategy of diversification in providing non-energy raw materials for EU value chains and ensuring the social welfare. Diversification of supply is related to reducing the dependencies in all areas by supplying primary raw materials from the EU, by increasing the supply of secondary raw materials through efficient use of resources, and by finding alternatives to scarce raw materials. One of the priority actions was to create a list of critical raw materials at the EU level.

Coal free-swelling index modeling by an ordinal-based soft computing approach

ABSTRACT Coking coal is the most important reductant agent in the steel-making industry and approximately does not have any substitution. Thus, it is globally still on the list of critical raw materials. The free swelling index (FSI) as a qualitative index is used to assess and rank the coking-ability of coal samples. Although the accurate classification of FSI values is one of the most crucial issues in the coke-making industry, it has become one of the most challenging data-driven problems due to the specific difficulties that lie in coal data characteristics. In this study, by analyzing a robust dataset with over 3600 records from U.S. Geological Survey Coal Quality, an insight was obtained into the FSI classification problem factors that have led to the poor performance of machine learning models. By settling the class imbalance at the data level and applying an efficient model training strategy based on the ordinal classification at the algorithmic level, a novel structure for FSI modeling has been proposed. This study also demonstrates direct relation between the model accuracy and the impact of nonlinear feature selection using Mutual Information instead of traditional linear methods.

Stream sediment analysis for Lithium (Li) exploration in the Douro region (Portugal): A comparative study of the spatial interpolation and catchment basin approaches

Lithium (Li) was recently added to the list of critical raw materials by the European Union due to its significance for the green energy transition. Thus, the development of new toolchains to make Li exploration more economic and more effective is needed. Stream sediment analysis can play an important part in these new tool chains. In this work, two historical stream sediment datasets covering parts of the Fregeneda-Almendra pegmatite field in the Douro region (Portugal) were reprocessed considering two distinct approaches: spatial interpolation through inverse distance weighting (IDW) and the catchment basin approach using the concentration area (C-A) fractal analysis. The following objectives were delineated: (i) determine pathfinder elements for Li, considering relevant associations in the mineralization sources; (ii) compare the performance of both approaches; (iii) identify new target areas for Li. In the case of spatial interpolation, the highest Li values were associated to granites although the use of key elements allowed lithological discrimination and the delineation of target areas. In the catchment basin approach, fractal analysis proved to be effective in decreasing the number of areas of interest with high accuracy (>75%) when considering the previously mapped Li-pegmatites. One of the limitations identified was the number of anomalous basins related to the granites, despite the use of pathfinder elements allowing discriminating granite- from pegmatite-related Li anomalies. Comparing the two approaches, the spatial interpolation method is more adequate for the early stages of exploration (reconnaissance), while the catchment basin approach is more suited for prospect-scale exploration. Field validation of the results identified one pegmatite containing Li mineralization and three others with favorable signs for Li mineralization in the Douro region.

The Economics of Coking Coal Mining: A Fossil Fuel Still Needed for Steel Production

Coking coal has been on the European list of critical raw materials since 2014 due to its high economic importance and high supply risk. In 2017, coking coal narrowly missed passing the threshold of economic importance. However, out of caution, it remained on the list of critical raw materials, as the steel industry still needs it. It is likely to be phased out of the list below when it does not fully meet the required criteria. As there are no significant alternatives for this energy intensive industry and neither electrification nor material or energy efficiency improvements are yet available at a sufficient level of technological readiness, the European Union remains dependent on coking coal imports. Therefore, any coking coal mining project in Europe is of great importance and an important alternative to solving the problems of providing this raw material. In this study, the Dębieńsko coking coal project in Poland is analyzed using a scientifically proven methodology based on world-class analysis of coking coal projects submitted for financing to financial institutions.

Cadmium Recovery from Spent Ni-Cd Batteries: A Brief Review

The significant increase in the demand for efficient electric energy storage during the past decade has promoted an increase in the production and use of Cd-containing batteries. On the one hand, the amount of toxic Cd-containing used batteries is growing, while on the other hand, Cd is on a list of critical raw materials (for Europe). Both of these factors call for the development of effective technology for Cd recovery from spent batteries. The present paper is aimed at providing a short review of the recent progress in Cd recovery from spent batteries. Statistical data from the past decade on the source of Cd, its global production, and Ni-Cd battery recycling are given in the introduction. A short overview of the pyro-and hydro-metallurgical methods of metal production is provided. Recent progress in Cd recovery by commercial methods during the past decade is reviewed.

Modeling and Characterization of Complex Concentrated Alloys with Reduced Content of Critical Raw Materials.

The continuous development of society has increased the demand for critical raw materials (CRMs) by using them in different industrial applications. Since 2010, the European Commission has compiled a list of CRMs and potential consumption scenarios with significant economic and environmental impacts. Various efforts were made to reduce or replace the CRM content used in the obtaining process of high-performance materials. Complex concentrated alloys (CCAs) are an innovative solution due to their multitude of attractive characteristics, which make them suitable to be used in a wide range of industrial applications. In order to demonstrate their efficiency in use, materials should have improved recyclability, good mechanical or biocompatible properties, and/or oxidation resistance, according to their destination. In order to predict the formation of solid solutions in CCAs and provide the optimal compositions, thermodynamic and kinetic simulations were performed. The selected compositions were formed in an induction furnace and then structurally characterized with different techniques. The empirical results indicate that the obtained CCAs are suitable to be used in advanced applications, providing original contributions, both in terms of scientific and technological fields, which can open new perspectives for the selection, design, and development of new materials with reduced CRM contents.

Metamorphic graphite from Szendr\u0151l\xe1d (Szendr\u0151 Mts., NE-Hungary) detected by simultaneous DTA-TG

Graphite, one of the polymorphic forms of carbon, has become a versatile industrial material of nowadays due to its particular attributes. It is used mainly in the automobile industry, metal extractive industry and in the high-tech industry. Moreover, it is also included in the list of critical raw materials for the EU. Our aim was to prove the presence of graphite by thermal analysis beyond X-ray powder diffraction (XRD) and Raman spectroscopy. Thermogravimetry yields comparable results with quantitative XRD. The formation conditions are described by Raman spectrometry and microscopy examinations of drill core samples from Szendrőlád (Szendrő Mts, NE-Hungary; (Szendrőlád Limestone Formation, middle-late Devonian, shelf-basin facies). Polished rock slabs were made for optical microscopy, scanning electron microscopy with energy dispersive spectrometry (SEM–EDS) and Raman spectroscopy. X-ray powder diffraction (XRD) and thermal analysis (DTA-TG) measurements were made on powders. Based on our results, the graphite is epigenetic; its quantity varies between 1.5–3 mass% in the samples. It was developed in 20–50 μm sized flakes, which are often arranged in > 300 μm sized aggregates. Graphite was formed during regional metamorphism from the organic matter-rich shales. The average formation temperature, calculated from the results of Raman spectroscopy, is around 410 °C (± 30 °C). The Raman measurements also indicated the presence of a partially graphitized (disordered graphite) material beside graphite.

New developments in biological phosphorus accessibility and recovery approaches from soil and waste streams.

Phosphorus (P) is a non‐renewable resource and is on the European Union's list of critical raw materials. It is predicted that the P consumption peak will occur in the next 10 to 20 years. Therefore, there is an urgent need to find accessible sources in the immediate environment, such as soil, and to use alternative resources of P such as waste streams. While enormous progress has been made in chemical P recovery technologies, most biological technologies for P recovery are still in the developmental stage and are not reaching industrial application. Nevertheless, biological P recovery could offer good solutions as these technologies can return P to the human P cycle in an environmentally friendly way. This mini‐review provides an overview of the latest approaches to make P available in soil and to recover P from plant residues, animal and human waste streams by exploiting the universal trait of P accumulation and P turnover in microorganisms and plants.

Critical raw materials as a part of sustainable development

The presented article deals with the issue of critical raw materials in the European Union with an emphasis on sustainable development and also barite, as an only one critical raw material mined in Slovakia. The article points out in detail the deposits of individual critical raw materials within the European Union. They clearly profile the European area´s dependence on imports of critical raw materials in accordance with the Communication from the Commission to the Council, the European Economic and Social Committee and the Committee of the Regions on the European Union's list of critical raw materials. Based on a defined Herfindahl-Hirschman index, which is clearly methodologically described, the article also points to the exploitation of critical raw materials in the European Union, what is in consideration of sustainable development crucial because some inventions are fundamentally dependent on them, as is their production on world markets. This article deals with critical raw materials in the EU, because it is in this area that we would like to experience the 4th industrial revolution, which is characterized by "new products" with a short life cycle, products with the least possible impact on the environment, i.e. innovations that are often impossible without important raw materials. Is it at all possible to talk about sustainable development with such raw material sources in European Union?

EC announces actions to increase security and sustainability of Europe's raw materials supply.

Currently, the coronavirus crisis is leading many parts of the world to look critically at how they organize their supply chains, especially where public safety or strategic sectors are concerned. In September, the European Commission (EC) released its “Action Plan on Critical Raw Materials,” the “2020 List of Critical Raw Materials,” and a foresight study on critical raw materials for strategic technologies and sectors from the 2030 and 2050 perspectives. The Action Plan looks at the current and future challenges and proposes actions to reduce Europe's dependency on third countries, diversifying supply from both primary and secondary sources, and improving resource efficiency and circularity while promoting responsible sourcing worldwide.

Municipal waste incineration fly ashes: from a multi-element approach to market potential evaluation

BackgroundFly ashes from municipal solid waste incineration contain significant amounts of (technology critical) elements. Processes to recover Cu or Zn are already in practice, but it still remains difficult to evaluate the full secondary resource potential of the ashes. One reason is the absence of a worldwide comparable analytical basis for detailed market analyses. To encounter this, (i) an advice on how to analyse 65 elements after microwave-assisted digestion by ICP-OES and ICP-MS is delivered, (ii) the heterogeneity (hours to annual cycle) is evaluated for a incineration plant, (iii) leaching efficiency with three different eluents and (iv) the market potential of the elements as commodities are evaluated.Results and conclusionsAqua regia digestion was found to be sufficient to evaluated the recovery potential; except for the mass constituents Al, Si, Sn, Ti and the trace components Cr, Hf, Nb, U and W, for which HF-containing digestions delivered better recoveries. On different time scales, ashes were very homogenous and HCl- as well as H2SO4-supported leaching delivered, satisfying results within an hour (exceptions are, e.g., Bi and Sb). By applying characterisation factors of the life cycle assessment impact category “Resource depletion—minerals and metals” supplemented by the list of critical raw materials of the EU: Ag, Bi, Cd, Ga, In and Sb are most interesting elements to be recovered in future activities.