Rare Earth Production Research Articles

A novel and versatile precursor for the synthesis of highly preorganized tetradentate ligands based on phenanthroline and their binding properties towards lanthanides(III) ions

Rare earth elements (REEs) are vitally important for both high-tech industry and homeland security. Current industrial production and purification of REEs rely mostly on solvent extraction, for which, the overall extraction efficiency is largely determined by the organic ligands used as extractants. Ligands based on 1,10-phenantroline-2,9-diamides (PhenDA) are promising candidates and have been intensively investigated for both lanthanides (Lns) and/or lanthanides/actinides (Lns/Ans) separations. The synthetic drawback for current PhenDA derivatives lies in the equivalent usage of acyl chloride for the key precursors, thus limiting functional group tolerance and large-scale production of the extractants. Herein, we have demonstrated a new synthetic approach for mild reaction condition, high-yield synthesis of various types of PhenDA derivatives ranging from alkyl, aromatic to amino acid substituents. The synthetic procedures are relatively green for the absence of corrosive, volatile reagents and easy of product purification. The in-group Lns discrimination of one ligand is investigated in detail to demonstrate the separation potential. Considering the broad functional group tolerance of the current method and ease of large-scale production, we believe the methodology will broaden the ligands scope based on PhenDA and inspire new functionalities of Lns complexes.

Conceptual Process Development for the Separation of Thorium, Uranium, and Rare Earths from Coarse Coal Refuse

ABSTRACT Increasing disruption in the rare earth supply chain creates an urgency to develop alternative resources, in which utilization of coal-based materials presents great potential. Nevertheless, environmental control is a significant challenge in rare earth extraction processes. This study was conducted to contribute to the limited information on removing thorium and uranium from rare earths while coal-based products are used as feedstock. The laboratory studies suggested that the selective precipitation and solvent extraction approach yields the most favorable separation performance. Complete thorium precipitation was achieved around a pH value of 4.8. Due to the close precipitation pH ranges of uranium and rare earths, further separation by solvent extraction was applied to achieve an enhanced separation. Based on a Box-Behnken experimental design, the effect of extractant concentration, pH, strippant concentration, and O/A ratio was investigated. Best separation performance was achieved using 50 v% TBP at a pH of 3.5 with an O/A ratio of 3 and 1 mol/L H2SO4, which resulted in 1.8% uranium and 73.4% rare earth extraction. The extraction and precipitation behavior of the elements were further assessed with the distribution ratio, separation factor, thermodynamic parameters, and species distribution diagrams to provide a thorough understanding of the separation mechanisms. The results were statistically analyzed, and a model was developed to predict uranium recovery. The developed experimental protocol was validated using a rare earth oxalate sample produced at the pilot-scale processing facility. Finally, a conceptual process flowsheet was developed to effectively separate radionuclides while producing rare earth oxide products.

Allocating environmental costs of China's rare earth production to global consumption

China provides over 80% of global rare earth (RE) that caused serious domestic environmental impacts. However, how much RE-related pollution was transferred to China along global supply chain remains poorly understood. Here we, for the first time, established the RE industry-specific input-output approaches to trace environmental costs transfer through China's RE exports from whole supply chain perspective. We found that foreign consumption contributed over half of the environmental costs from China's RE production, with a gross value increasing from $4.8 billion (65% of total environmental costs) in 2010 to $5.4 billion in 2015 (74% of total environmental costs). Countries in the East Asia (i.e., Japan and South Korea) made the largest contribution (27–37%) to the exports induced environmental costs, followed by North America (i.e., the United States, Mexico, and Canada) with a contribution of 20–27% and the rest East Asia (including countries in Asia-Pacific except China Mainland, by 16–23%). Exports induced environmental costs were mainly from RE raw materials (60%) and high value-added products (22%). Suggestions such as rationalizing RE cost as well as production- and consumption-based measures to mitigate environmental impacts were proposed to enhance RE utilities for global sustainable development.

Development and beneficiation technology of rare earth ores in China

The demand for rare earth elements (REE) is increasing rapidly owing to the emergence of new clean-energy and defense-related technologies. China's dominates the world production of REE. In this paper, we review the ore characteristics of four typical REE deposits in China and discuss the conventional beneficiation techniques, including gravity and magnetic separation, flotation, and hydrometallurgical processing of these ores. Some of the latest laboratory findings and industrial applications, as well as the development of novel reagents for REE processing in China are presented. The REE beneficiation technologies developed and employed in China could constitute a good case study for many other emerging projects being explored around the world.

Ресурсный потенциал гряды Чернышева (Тимано-Печорский бассейн) в контексте новых данных о строении и продуктивности соленосных надвиговых поясов

The salt bearing thrust belts are among the most prolific petroleum provinces in the world, including the fold belts flanking the Persian Gulf Basin, the Tarim Basin, the Terek-Sunzha Zone of the Eastern PreCaucasus etc. They are characterized by peculiar structural styles of deformation, large oil and gas pool sizes, significant flow rates. The Chernyshev Swell is among prospective salt bearing thrust belts. It is located in the Cis-Uralian part of the Timan Pechora Basin. Several exploration wells have been drilled in the area so far failed to deliver the anticipated oil and gas deposits. Post mortem study indicated that the main reason for the past failures was the mismatch between the complexities of the geological settings and the used exploration technologies. Integrated study of the area, conducted by the North Uralian Petroleum Company, using modern technologies, including 3D seismic surveying and magnetotelluric sounding, has enabled a far better understanding of this area’s structure and petroleum habitat. It is shown that high petroleum potential is attributed to the transition zone between the Chernyshev Swell and the Kosyu Rogov Foredeep Basin. This study indicated that the area of the Povarnitsa High is of priority interest for explration. This area provides supplementary opportunities in addition to the commercialization of the petroleum exploration potential. It includes production of rare earth and metals in brine of the evaporate deposits. The subsalt reservoirs of the Chernyshev Swell could be used for the storage of gas and CO2 sequestration. Integrated development of the resource potential of the Povarnitsa High may become a key driver of the economic development of the north-eastern part of the Republic of Komi.

China’s Global Monopoly on Rare-Earth Elements

This article delivers a novel economic analysis of US dependence on China for rare-earth elements and sheds light on how Western nations may exploit the limitations of limit pricing to break China’s global monopoly in rare-earth element production and refinement. This analytical framework, supported by a comprehensive literature review, the application of microeconomic and industrial organization concepts, and two case-study scenarios, provides several policy recommendations to address the most important foreign policy challenge the United States has faced since the end of the Cold War.

Recent advances in the global rare-earth supply chain

The current global rare-earth element (REE) supply chain is highly imbalanced and tightly controlled by just a few countries. Such an imbalance of the critical metals supply chain poses a significant challenge to the energy-transition strategies and the national security of many countries. This issue of MRS Bulletin delves into the materials science aspects of the REE supply chain, including fundamental REE mineralogy, REE separation and extraction, REE mining economics, the environmental impacts of REE mining and processing, and circular economy potential for REEs. This issue of MRS Bulletin is meant to inform the materials science community of some of the constraints on REE production from the mining of ore deposits, through processing technologies, and then finally, the possibility of recycling.Graphical abstract

A Hybrid Experimental and Theoretical Approach to Optimize Recovery of Rare Earth Elements from Acid Mine Drainage Precipitates by Oxalic Acid Precipitation

The development of processing techniques for the extraction of rare earth elements and critical minerals (REE/CM) from acid mine drainage precipitates (AMDp) has attracted increased interest in recent years. Processes under development often utilize a standard hydrometallurgical approach that includes leaching and solvent extraction followed by oxalic acid precipitation and calcination to produce a final rare earth oxide product. Impurities such as Ca, Al, Mn, Fe and Mg can be detrimental in the oxalate precipitation step and a survey of the literature showed limited data pertaining to the REE precipitation efficiency in solutions with high impurity concentrations. As such, a systematic laboratory-scale precipitation study was performed on a strip solution generated by the acid leaching and solvent extraction of an AMDp feedstock to identify the optimal processing conditions that maximize REE precipitation efficiency and product purity while minimizing the oxalic acid dosage. Given the unique chemical characteristics of AMDp, the feed solution utilized in this study contained a moderate concentration of REEs (440 mg/L) as well a significant concentration (>7000 mg/L total) of non-REE contaminants such as Ca, Al, Mn, Fe and Mg. Initially, a theoretical basis for the required oxalic acid dose, optimal pH and predicted precipitation efficiency was established by solution equilibrium calculations. Following the solution chemistry calculations, bench-scale precipitation experiments were conducted and these test results indicate that a pH of 1.5 to 2, a reaction time of more than 2 h and an oxalic acid dosage of 30 to 40 g/L optimized the REEs recovery of at ~95% to nearly 100% for individual REE species. The test results validated the optimal pH predicted by the solution chemistry calculations (1.5 to 5); however, the predicted dosage needed for complete REE recovery (10 g/L) was significantly lower than the experimentally-determined dosage of 30 to 40 g/L. The reason for this discrepancy was determined to be due to the large concentration of impurities and large number of potential metal complexes that cause inaccuracies in the solution equilibrium calculations. Based on these findings, a hybrid experimental and theoretical approach is proposed for future oxalic acid precipitation optimization studies.

Liquid-liquid extraction of rare earth elements using systems that are more environmentally friendly: Advances, challenges and perspectives

• Alternative liquid–liquid techniques for rare earth extraction are reviewed. • Properties and green characteristics of alternative methods are assessed. • Comparisons with traditional solvent extraction method are presented. • Cloud point extraction demonstrates analytical pre-concentration method potential. • Aqueous biphasic systems demonstrate potential for large scale implementation. The rare earth elements, a group of metals consisting of the lanthanide series, together with yttrium and scandium, are increasingly important in high technology industries worldwide. Given the need to expand production of these elements, there is a search for processes to obtain them that are less environmentally damaging, since the rare earths production chain is associated with several environmental problems and concerns. Solvent extraction, one of the important steps involved in the obtaining of rare earth elements, is receiving much attention in the scientific and industrial community, with a renewed search for approaches that avoid the use of organic solvents. Among the various options, cloud point extraction and the use of aqueous two-phase systems are alternatives to the use of traditional organic solvents. This review considers these two more environmentally friendly techniques and their use for the extraction and/or separation of rare earth elements. The issues addressed include their potential to replace traditional liquid–liquid extraction, in terms of the efficiency, toxicity, and biodegradability of the components forming the systems, as well as their potential applications and future perspectives.

Bacterial cellulose nanofibrous ion imprinted aerogel for highly efficient recognition and adsorption of Dy(III)

The highly selective recovery of Dy(III) from used rare earth products has high environmental and economic benefits. In this paper, biocompatible bacterial cellulose with a unique 3D network structure was used as the basic structure, graphene oxide and polyethylene glycol were introduced to increase the adsorption capacity, and the ion imprinting technology was used to prepare a green aerogel that could adsorb dysprosium ions with a high selectivity. The various properties of aerogels were characterized by SEM, FT-IR and BET. Experiments proved that the introduction of graphene oxide and polyethylene glycol brought a higher stability and repeatability to aerogel, and the introduction of a large number of carboxyl groups also promoted the effective coordination of aerogel with dysprosium. Adsorption experiments showed that I-GO-OBC-pDA-PEG aerogel could effectively adsorb dysprosium, and its maximum adsorption capacity for Dy(III) was 49.904 mg g−1, and its maximum adsorption capacity was 10 mg g−1 higher than that of the non-imprinted aerogel, which was a good proof of the effectiveness of the ion imprinting technology. The repeatability test showed that after five adsorption-desorption cycles, the adsorption capacity of the imprinted aerogel was maintained at about 80% of the maximum adsorption capacity. All results showed that I-GO-OBC-pDA-PEG aerogel could efficiently recover dysprosium ions.

Advances in the Fate of Rare Earth Elements, REE, in Transitional Environments: Coasts and Estuaries

The production of rare earth elements, REE, has significantly increased over the past years, in parallel with the latest advances in nanotechnologies and representing a new group of emerging contaminants. They find application in construction, transport, agriculture, electronics, catalysis, and biomedicine. Their extraordinary intrinsic characteristics are fundamental for overcoming current technological challenges. The accumulation of REE is consistent in near-shore waters being affected by runoff, wastewater discharge, and proximity to built-up areas. Bioavailability in water, sediments, and accumulation in marine biota as well their endocrine disruptor effect is mostly unknown. There is a significant gap of knowledge on the ecotoxicological behaviour of REE in marine areas. The existing investigations have been performed inside well-mixed estuarine systems, due to complex hydrodynamics and multiple sediment transport situations. This hampers the definition of regulatory thresholds for REE concentrations and emissions. The review summarizes the existing information on REE geochemistry and physicochemical conditions influencing dissolution, surface complexation reactions, and distribution at the continent–ocean interface, as well as their speciation, bioavailability, and detrimental effects on living organisms. Strategies for reducing REE usage and inputs are also discussed.

Rare earth element resource evaluation of coal byproducts: A case study from the Powder River Basin, Wyoming

Domestic Rare Earth Element sources and production are limited in the United States and currently rely on final processing overseas. Increasing demand and resource security domestically has led to significant investigation into rare earth element domestic resources. Much of this work focuses on unconventional potential ore stocks, including coal and coal byproducts. This investigation focuses on coal byproducts generated as ash from coal burning power stations. Wyoming's Powder River Basin hosts the largest U.S. coal stocks for energy production, providing approximately 40% of all thermal coal mined in the U.S. In this effort, in section I, we have studied coal byproducts for rare earth element concentrations and compare these data to current alternative resource knowledge. We find that coal byproducts in this investigation are consistently high enough in rare earth element concentration (above the current Department of Energy 300 ppm cutoff grade) to warrant consideration as a promising potential resource. Rare earth element behavior within the host coal seams is also considered in an effort to better understand resource prospecting and ore body description. In Section II, we evaluate the economic feasibility of rare earth extraction from Powder River Basin coal byproducts using net present value analysis and the rare earth concentrations data from Section I. We calculate the break-even ash-to-oxide output and input unit costs for four coal stations in the Powder River Basin. All four stations have break-even unit costs that are higher than the mine-to-oxide operating cost reported for a traditional rare earth element mine. This is a promising result, especially given that it is more costly to refine rare earths from mined material than from ash. The results are highly sensitive to rare earth prices: given low long-term prices, none of the four stations can feasibly break even. Section III summarizes federal policy considerations in rare earth element resource development. The history of policy development, most recent focus on rare earth element specific funding legislation, paired with section I and II herein, suggest a robust opportunity for development of Wyoming based coal byproducts as a partial solution to current domestic rare earth element short falls and strategic needs.

Study on factors affecting rare earth leaching rate in acid leaching process of fly ash

There is a large amount of enrichment of rare earth elements in Zhungeer coal and coal ash, making it possible to use fly ash as a source for industrial production of rare earth elements. In order to optimize the leaching process of rare earth elements in fly ash and increase the leaching rate, the circulating fluidized bed fly ash of Zhungeer Power Plant was used as the material, and the single factor test and orthogonal test were used to influence the leaching rate of rare earth elements in the acid leaching process of fly ash The factors were discussed, and the results showed that when fly ash and 3mol/L hydrochloric acid were leached at a ratio of 1:10 for 2h at 130 0C, the element leaching effect was the best, and the leaching rate could reach 97%.

중국 희토류 무기화와 미얀마 군부 쿠데타의 관계 고찰

This paper deals with the history and recent trends of how China has weaponized rare earthelements, a strategic resource called Vitamins of high-tech industries. China is the world slargest producer and reserve of rare earths, and has pursued so-called ‘rare earth hegemony’against the United States and other competitors in terms of energy security. Using its superiorposition, rare earths have been used as leverage in disputes and negotiations against Japanand the United States. However, China s market share and influence in the global rare earthmarket have gradually declined due to domestic and foreign concerns over environmentalpollution in the process of rare earth production and the reorganization of the domestic rareearth industry. Instead of controlling the production of rare earth in the country, China needsa new source of rare earth. China early paid attention to Myanmar, a neighboring countryfacing the border and the largest resource rich country in southwest Asia. Myanmar rareearths were imported into China and exported back to the global market after refining. Myanmar quickly became China s largest importer of rare earth. China has maintainedfriendly relations through political and economic support, including the military, which hasruled Myanmar for a long time, as well as the civilian government, which emerged in 2015after democratization. Unlike Western countries, which criticized the military dictatorshipand the Rohingya crisis and imposed economic sanctions, China has always defended theMyanmar regime. In return, it has enjoyed various preferential treatment in raising resources,including rare earths. In particular, the military coup in Myanmar earlier this year was anopportunity for China. The military has used control over resources to secure black moneyfrom China, and China has condoned and virtually supported the coup caused by such amilitary. China, which has secured a stable supply of Myanmar s rare earth based on its closeties with the Myanmar military, is now actively weaponizing rare earths again.

Efficient and sustainable separation of yttrium from heavy rare earth using functionalized ionic liquid [N1888][NDA

The separation of adjacent rare earth (RE) is one of the most difficult separation tasks, especially the separation and purification of yttrium (Y) from heavy rare earth (HREE). In the traditional Y separation process, the organic phase composed of acidic extractants such as naphthenic acid (HA) and neodecanoic acid (NDA) need to be saponified with sodium hydroxide or ammonia in each cycle. The resulting alkali consumption and saponification wastewater have negative impacts on the environment. In this article, a bifunctional ionic liquid [methyltrioctyl ammonium][neodecanoate] ([N1888][NDA]) was synthesized. The extraction capacity, stripping property and recycling stability of [N1888][NDA] were systematically studied. On this basis, the separation process of Y was developed. The separation factors (β) of Ho/Y and Er/Y were 2.64 and 4.32, especially the Lu/Y reached 16.27. A higher separation factor is of significance for the separation of Y from HREEs. The extraction sequence of rare earth elements (REEs) with [N1888][NDA] follows the positive sequence extraction, which is the same as that in neodecanoic acid system. In addition, the separation process of industrial HREE feed liquid containing 0.20 mol L−1 REEs (Y, 88.87 mol.%) was studied. By adjusting the extraction conditions, salting-out reagent such as NaCl did not need to be used in the aqueous phase, which helps to avoid high salt components in RE products. Through the fractional extraction experiment of 11-stage extraction and 4-stage scrubbing, the Y product with a purity of 99.03 mol.% was obtained. The organic phase composed of [N1888][NDA] was stable after being regenerated with NaOH for recycling extraction.

Greenland and the geopolitics of critical minerals

Greenland and the geopolitics of critical minerals

A Fundamental Economic Assessment of Recovering Rare Earth Elements and Critical Minerals from Acid Mine Drainage Using a Network Sourcing Strategy

In recent years, acid mine drainage (AMD) has emerged as a promising unconventional source of rare earth elements (REEs) and other critical minerals (CMs) such as cobalt and manganese. In this regard, AMD provides a natural heap leaching effect that extracts and concentrates REE/CM from the host strata creating a partially enriched feedstock suitable for downstream extraction, separation, and recovery. While several prior studies have described processes and approaches for the valorization of AMD, very few have described the supply chain and infrastructure requirements as well as the associated economic assessment. To that end, this paper provides a fundamental economic assessment of REE/CM recovery from AMD using a network sourcing strategy in addition to a robust, flexible feedstock separations and refining facility. The methodology of this paper follows that of a typical techno-economic analysis with capital and operating costs estimated using AACE Class IV (FEL-2) guidelines. To demonstrate the range of possible outcomes, four pricing scenarios were modeled including contemporary prices (September, 2021) as well as the minimum and maximum prices over the last decade. In addition, five production scenarios were considered reflecting variations in the product suite, ranging from full elemental separation to magnet REE and CM production only (i.e., Pr, Nd, Tb, Dy, Y, Sc, Co, and Mn). The results of this analysis show that, with the exception of the minimum price scenario, all operational configurations have positive economic indicators with rates of return varying from 25% to 32% for the contemporary price scenario. The optimal configuration was determined to be production of Co, Mn, and all REEs except for mischmetal, which is not recovered. Sensitivity analysis and Monte Carlo simulation show that capital cost and HCl consumption are the two major factors influencing rate of return, thus indicating opportunities for future technology development and cost optimization. Implications of the study and a cooperative profit-sharing model for sourcing are also described.

A dynamic evaluation on the international competitiveness of China's rare earth products: An industrial chain and tech-innovation perspective

In the past decades, China's rare earth products have occupied a very important position in the international market. However, the existing literature still lacks an in-depth investigation on how competitive China's rare earth element (REE) products are, especially from an industrial chain and tech-innovation perspective. In this study, we developed a new revealed comparative advantage (NRCA) method by projection pursuit modeling and adopted the constant market share (CMS) model for measuring the long-term dynamic trends of the international competitiveness of China's REE exports. The results show that: (1) The international competitiveness of China's REE products has declined sharply in the past decade, and rebounded only in recent years; (2) The comparative advantages of China's REE products in the industrial chain vary greatly, the mid- and down-stream products have strong comparative advantages, while those in the upstream have no competitive edge; (3) China's REE market share is highly concentrated, and its market structure evolution reveals that the up- and mid-streams have been optimizing, but deteriorating in the down-stream. Based on these findings, we proposed relevant policy recommendations accordingly.

Organic and inorganic compounds as corrosion inhibitors to reduce galvanic effect for the hybrid structure AA2024-CFPR

The effect of the galvanic corrosion process taking place between aluminium alloy (AA2024-T3) and carbon fiber reinforced plastic (CFRP) immersed in 0.05 M NaCl was studied using organic and inorganic compounds as corrosion inhibitors. Electrochemical approaches such as electrochemical noise analysis (ENA) and electrochemical impedance spectroscopy (EIS) were carried out to evaluate efficiencies of 1,2,4-triazole (C2H3N3) and cerium nitrate hexahydrate (Ce(NO3)3·6H2O) as corrosion inhibitors. The highest efficiency was reached for Ce(NO3)3.6H2O, with some improvement observed by adding C2H3N3 in a mixed inhibitor solution. The noise resistance (Rn) and polarization resistance (Rp) values calculated from ENA and EIS data showed almost identical behavior with different magni­tudes but similar trends. Adsorption isotherm models estimated with fractional surface coverage (q) parameter were fitted better to Langmuir model for C2H3N3 and Temkin model for Ce(NO3)3·6H2O. The calculated values of Gibbs free energy suggested physi­sorption and chemisorption as spontaneous interactions between a metal surface and both inhibitors. Energy-dispersive X-ray spectroscopy (EDS) was carried out before and after immersing AA2024-T3 in the electrolyte, identifying rich zones in copper with cerium deposited over it and confirming the presence of rare-earth oxide deposition and oxide film products. The EDS analysis for CFRP revealed the deposition of Ce and Al particles over its surface after immersion in the electrolyte, especially in the areas rich in carbon.

Interfacial effects in the electro(co)deposition of Nd, Fe, and Nd-Fe from an ionic liquid with controlled amount of water

Neodymium is one of the most important rare earth elements due to its various applications, above all, in permanent magnets in consumer electronics and renewable power sources. Production of primary Nd is a rather complex and expensive process characterized by significant import dependency, which brings to the forefront Nd recovery from secondary sources. Electrowinning as one of the cheapest and processible solutions is not applicable for electropositive rare earths in aqueous systems but is a good option in the case of solutions based on ionic organic solvents. Nd electrodeposition and its induced codeposition with Fe are studied at room temperature in a fluorine-free dicyanamide ionic liquid (IL) using a complex set of electrochemical and physical (spectroscopic and microscopic) methods in dry solutions and in the presence of water. We show that the addition of water significantly promotes electrodeposition of individual metals in the respective single-component solutions but produces a hindering effect on the induced codeposition of Nd with Fe. We suggest an explanation for the acceleration of individual Nd and Fe in the presence of water based on the effects at the IL/electrode interface and for the inhibition of Nd-Fe deposition in the presence of water owing to the decelerating effect of formation of Nd oxide/hydroxide film. This is the first systematic study of the effect of water on the rare earth–transition metal codeposition in ILs providing information that can be essential for production of secondary rare earths and fabrication of novel lanthanide-based materials.