Rare Earth Production Research Articles

Mechanism and experimental study on the recovery of rare earth elements from neodymium iron boron waste by NaBF4 fluorination method

Pyrometallurgical recovery of rare-earth elements from NdFeB wastes is affected by the quality of the raw materials, and mixed rare-earth products add little value. Therefore, this study investigates NaBF4 fluoride roasting for the recovery of rare-earth elements and its underlying mechanisms. Reasonable roasting temperatures were determined based on thermodynamic calculations, and single-factor experiments were conducted. When roasted at 600 °C for 30 min with 65 % NaBF4, the fluorination rate of rare-earth elements reached 95.83 %. The composition of the clinker mesophase after roasting under different conditions was analyzed. At high temperatures, oxygen heteroatoms entered the crystal lattice of the rare-earth fluorides, which were subsequently removed during acid leaching, thereby reducing the recovery rate. A three-factor, three-level Box–Behnken test was conducted using the response surface methodology to analyze the effects of various factors and their interactions on the fluorination rate. Thus, an experimental basis for the recovery of rare-earth elements from NdFeB by fluoridation roasting was established. The roasting temperature had the greatest effect on the fluorination rate, followed by the roasting time and amount of NaBF4. The model predicted an optimal fluorination rate of 98.63 % when the material was roasted at 573 °C for 25 min with 59 % NaBF4. The clinker was acid-leached under optimal conditions (2.5 h at 80 °C with 9 M HCl and a liquid–solid ratio of 4 mL/g), and the fluorination rate reached 99.39 %. These results provide theoretical and experimental support for the application of pyrometallurgy in the recovery of rare-earth elements from NdFeB wastes.

Rare Earth Elements: A Global Scenario and Understanding of Their Impacts, Challenges, and Recycling Processes in Bangladesh through Global Literature

Over the last decade, rare earth elements (REEs) have gained international attention due to their multiple usages. Because of their unique properties, the elements play a vital role in electronics, defense, aerospace, transportation, agriculture, and communications technology. They are also critical to the high technology and low carbon economy. These applications drive demand for rare earth products and promote the steady development of the rare earth industry. In this paper, we have reviewed the current scenario, applications, challenges, and impacts of REEs from a global perspective. It is seen that China leads in the production of REEs worldwide. Globally, REE production is associated with a range of environmental issues, including mining-related pollution, the generation of radioactive waste, water scarcity, soil contamination, and deforestation, all of which impact both humans and animals. Drawing from global literature, we discussed a comparative scenario of REEs in Bangladesh. In Bangladesh, the rising population has led to increased REE demand, and we utilized secondary sources to deduce REE impacts. We overviewed aspects such as 100% electricity coverage, import opportunities from the other countries, and government initiatives, all contributing to the growing REE demand and e-waste generation in Bangladesh. Currently, there is no recycling process available. Subsequently, we highlighted the situation in Bangladesh regarding REE management, presented suggestions for recycling based on recent global literature, and provided recommendations for the future.

Determination of rare earth elements in ferrocarbonatite using ICP-AES and ICP-MS

AbstractA method has been developed for the determination of Rare Earth Elements (REEs) in ferrocarbonatite using Inductively Coupled Plasma—Atomic Emission Spectrometer (ICP-AES) and Inductively Coupled Plasma—Mass Spectrometer (ICP-MS). The conventional dissolution procedures are tedious, with large measurement uncertainty and are thus not suitable for certified reference material (CRM) production and exploration of REEs. The described method involves leaching of sample using 3 M HCl followed by dissolution of residue (silica and REEs) by HF then determined REEs using ICP-AES and ICP-MS. The leaching step prevents formation of fluoride precipitates of matrix (Ca, Mg, Ba and Al). The method has been validated using CRMs.

Simultaneous rare earth sulfate transformation and carbon dioxide mineralization

The wet metallurgical process route for recovering rare earth elements usually uses sulfuric acid. To obtain marketable individual rare earth products, converting rare earth sulfates to chlorides is essential. Conventional chemical precipitation and solvent extraction methods result in significant amounts of ammonia wastewater and greenhouse gas emissions. Therefore, we propose a novel process that integrates CO2 mineralization with rare earth sulfates transformation. By utilizing a base-catalyzed mechanism with trioctylamine (TOA), CO2 is effectively employed for selective precipitation of more than 95 % of rare earths from magnesium and calcium under optimized conditions. Subsequently, dissolution in hydrochloric acid allows for enrichment of the concentration of rare earths up to 188.3 g/L. The reaction mechanism is examined through Visual MINTEQ simulations and various analytical techniques. This process not only offers a sustainable approach to rare earth sulfates transformation but also contributes to carbon capture, utilization, and sequestration efforts.

Coal ash resources and potential for rare earth element production in the United States

The renewable energy industry is heavily reliant on rare earth elements, underscoring the need to develop resources and production. The objective of this work was to estimate coal ash resources and potential for extraction of rare earth elements using data for the US. Data on spatiotemporal variability in coal ash resources and disposition were compiled from various federal databases and rare earth elements levels in ash were compiled from the literature. Results show that ~ 52 gigatons (Gt) of coal were produced in the US (1950–2021). Power plants account for most of the coal use, particularly since 1980. Coal ash (5.3 Gt) represents a mean of 10% of coal by weight, ranging from 6% for subbituminous to 14% for lignite. About 70% of coal ash is potentially accessible for rare earth element extraction (1985–2021) and was disposed in landfills and ponds with the remaining coal ash used onsite or sold. Median values of total rare earth elements are much higher in ashes derived from the Appalachian Basin (median 431 mg/kg) than in the Illinois (282 mg/kg) or Powder River basins (264 mg/kg). Considering the market value of rare earth oxides, potentially accessible ash volumes, and percent rare earth element extraction (30% Appalachian and Illinois Basins; 70% Powder River Basin) results in an estimated $8.4 billion value. This study provides fundamental information on accessible coal ash resources in the US, linkages to coal sources, and preliminary estimates of rare earth element levels for future development within the US.

Mapping complexity: Analyzing rare earth production life cycle inventories with network analysis

Understanding the significance of process clusters in life cycle inventory networks is crucial for optimizing supply chains, especially for critical elements like rare earth elements (REEs) production. This study employs network analysis (NA) to examine life cycle networks using facility-level energy/material data, extracting information from LCA networks. Based on Chinese facility reports, the investigation evaluates the environmental footprint of various rare earth production pathways, vital to the clean energy sector. It also considers rare earth permanent magnet manufacturing and magnet recycling. Using network metrics, including indegree/outdegree strength, closeness centrality, and betweenness centrality, the study assesses the resilience and sustainability of REEs production networks. Results highlight vulnerable nodes like "Neodymium Oxide" and "Nd Metal," aiding in identifying environmentally impactful materials and energy flows to develop more sustainable processes for meeting growing demand while enhancing environmental performance.

Summary of the Research Progress on Advanced Engineering, Processes, and Process Parameters of Rare Earth Green Metallurgy.

The addition of rare earth metals to aluminum alloys can effectively improve their corrosion resistance and has been widely used in the aerospace and military industries. However, the current methods for the preparation of rare earth metals involve long processing steps, high energy consumption, and high carbon emissions, which severely constrains the development of aluminum alloys. Its output is further developed. To this end, this paper reviews mainstream rare earth production processes (precipitation methods, microemulsion methods, roasting-sulfuric acid leaching methods, electrochemical methods, solvent extraction methods, and ion exchange methods) to provide basic information for the green smelting of rare earth metals and help promote the development of green rare earth smelting. Based on the advantages and disadvantages of each process as well as recent research results, the optimal process parameters and production efficiency were summarized. Studies have concluded that the precipitation method is mostly used for the recovery of rare earth elements and related valuable metals from solid waste; the microemulsion method is mostly used for the preparation of nanosized rare earth alloys by doping; the roasting-sulfuric acid leaching method is mostly used for the treatment of raw rare earth ores; and the molten salt electrolysis method is a more specific method. This is a green and environmentally friendly production process. The results of this study can provide direction for the realization of green rare earth smelting and provide a reference for improving the existing rare earth smelting process.

Forecasting synergistic pathways between rare earth elements, renewable energy, and product and economic complexities in achieving a low-carbon future

Recent decades have witnessed an unprecedented transformation in the global energy landscape, driven by environmental concerns and the quest for sustainable economic growth. As the world grapples with the urgent need for decarbonization, the utilization of renewable energy technologies with the instrumental role of rare earth elements (REEs) has come to the forefront. However, empirical investigations into their synergistic pathways for product and economic complexities concerning achieving a low-carbon future remain scarce. Therefore, we forecast synergistic pathways between the REE supply, renewable energy, economic and product complexities, and GDP growth using a panel dataset of 11 REE-producing countries from 1990 to 2023. We used Common Correlated Effects and Temporal Causal Models as primary methods to estimate panel long-run elasticities and subsequently forecast mutual causal synergies between the variables. The results indicated that REE supply led to renewable energy and economic growth that further elevated the countries’ product and economic complexities rankings. GDP growth increased REE production, economic complexity, and renewable energy directly, and consequently, product complexity and REE production through them. This underscores the positive role of REE production coupled with renewable energy technologies in achieving a low-carbon future based on economic diversification, enhanced industrial capabilities, and technological sophistication.

Rare earth elements-A review of exploration, processing, environmental impact, recycling and prospect analysis

In high-tech and low-carbon economies, rare earth elements are becoming increasingly important. Global demand for REEs is increasing as society transitions to a more sustainable model with the goal of reducing reliance on fossil fuels. The study on rare earth elements (REEs) is reviewed in this document, including estimations of the world's reserves, categorization of REE deposits, key REE production paths and processing techniques, environmental effects, and the possibility for recycling in the rare earth business. This paper's main goal is to present a comprehensive environmental and socioeconomic perspective on REEs, emphasizing the environmental effects of various REE-related activities and looking at how REEs can be used more effectively and scientifically, such as by investigating the viability of recycling REEs. and offer an outlook for the future. In order to address the issues with their demand and lower the dangers involved with supplying rare earths, researchers are further developing the methods for mining and using rare earth elements as well as recycling and reusing them.

Geo-economics of China's rare earths production: Concurrent green transition and environmental vulnerability

Serving as a regional assessment of China's ongoing mining and application of REEs, this article addresses the concurrence of green transition and environmental degradation contextualized in the global sphere of the Critical Mineral mining and application. It narrates a history of China's developmental strategies for REEs mining and production since the late 1970s and addresses the environmental outcomes from the state-determined, globalized national economy and the state-initiated environmental regulations on domestic REEs mining. Focusing on a historical assessment of China's geopolitically-strategized Critical Mineral production and the high environmental cost of the REEs-based green transition, this article discusses how UN's concept of sustainable development is being indigenized in China through the Chinese state's policy practices as well as through the receptiveness of the Chinese populace, and supports the ongoing argument of just transition as an unjust energy transition creating unjustified environmental dispossession, particularly in the local societies in China and elsewhere in the world.

Exploring synergistic and individual causal effects of rare earth elements and renewable energy on multidimensional economic complexity for sustainable economic development

The ongoing global energy transition has highlighted the instrumental role of rare earth elements (REEs) in achieving green growth through the deployment of renewable energy technologies, establishing a hypothetical progressive synergistic association between them. Therefore, testing this hypothetical synergy and its potential causal effects on economic and technological proxies based on empirical foundations becomes imperative in addressing rampant climatic change. First, we employed Deep Learning algorithms to explore the combined effects of this synergy on Multidimensional Economic Complexity (MEC) as an index using panel data of the largest producers of REEs from 1990 to 2023. Second, Temporal Causal Modelling (TCM) was employed to unveil the directional causality between REEs and renewable energy, as well as their causal roles in driving economic complexities. The deep learning models accurately predicted the positive role of this synergistic relationship in promoting overall MEC. Then, the results of TCM reveal that REE production increases renewable energy use and reduces CO2 emissions. Renewable energy promotes Research and Technology complexities while REE production affects them indirectly through renewables. It implies that harnessing this synergy to enhance economic complexities can, in turn, bolster green economic and technological development while mitigating CO2 emissions and addressing pervasive climate change.

Geochemical characteristics of rare earth elements in late Palaeozoic coals from North China

Introduction: China is a large country of REE resources and production, supplying more than 90% of the world’s rare earth consumption market, China’s traditional REE resources, although rich, but reserves are also declining, in recent years, scholars have shown that the REEs in the specific geological conditions in the coals can be enriched, and even reach the industrial grade, the search for more REE mineral resources will be of great strategic significance.Methods: The article has selected the Zibo, Taozao, Huainan, Datong, Huozhou, Jungar, and Weibei coalfields in North China as the research objects. Based on inductively coupled plasma mass spectrometry (ICP-MS) analyses, the study provides a detailed analysis of the enrichment rules and distribution patterns of rare earth elements (REEs) in coal under different geological conditions.Results: The REE distribution patterns in Late Palaeozoic coals in North China are characterized by enrichment of LREEs, deficit of HREEs with gentle changes, and obvious negative anomalies of Eu, the enrichment of REE in coal is controlled by provenance and volcanism, and is related to distance of transport terrigenous material and the sedimentary environment. The REEs concentrations in North China indicates that Late Palaeozoic coals in the mining areas of the north, northwest, and western parts of North China are significantly enriched in REEs. In addition, REEs in Late Palaeozoic coals in the southeastern mining areas are relatively enriched, and the central and eastern regions are significantly depleted.Discussion: Large coal-type rare earth deposits are expected to be developed in North China, particularly the Datong coalfield, Jungar coal mine and the Weibei coal mine in the eastern margin of the Ordos Basin, and the Zibo coalfield.

Innovative pilot-scale process for sustainable rare earth oxide production from coal byproducts: A comprehensive environmental impact assessment

This study developed a pilot-scale process feeding with two different materials resulting from a column leaching process and acid mine drainage (AMD) streams to recover rare earth elements (REEs). A life cycle assessment (LCA) study was done to evaluate the environmental impacts of rare earth production from deleterious material in the form of highly contaminated leachate (HCL) and low-contaminated leachate (LCL). The results indicate that the main contributors to environmental categories that produce RE-hydroxide stages are NaOH and electricity. Also, oxalic acid, Na2CO3, and hydrochloric acid significantly contribute to the production stage of individual rare earth oxides (REOs), including solvent extraction (SX) and precipitation steps. The HCL route has higher environmental impacts than LCL due to higher chemical/energy and H2SO4 usage, so 468 and 292 kg of carbon dioxide are generated to produce 1 t of individual REOs from HCL and LCL routes, respectively. Moreover, the carbon dioxide emitted from the process, including the RE-hydroxide production, SX, and REOs production, is less than 10 t CO2. A sensitivity analysis was also performed to assess the changeability of the environmental footprints of the main inputs in the SX process, as the main stage has a higher contribution to the whole process. This LCA study is the first step toward understanding the environmental influence of new processing methods to produce REEs from coal by-products through a developed pilot-scale process.

The impact of apatite on sulfuric acid baking of a monazite concentrate and the benefit of goethite addition on rare earth leaching

Sulfuric acid baking of monazite ((Ce,La,Th)PO4) bearing ores is one of the major processes used in commercial production of rare earth elements. In hydrothermal vein type rare earth deposits, apatite is often found together with monazite. Rare earth enriched fluorapatite ores may also contain significant amounts of rare earths hosted in monazite. An understanding of the effect of apatite on the sulfuric acid baking of monazite is therefore important for the development of effective sulfuric acid based treatment methods for such ores. In this work, the addition of a natural hydroxyapatite (Ca5(PO4)3(OH)) sample to a monazite acid bake followed by acid leach was investigated using a combination of chemical analyses, SEM-EDS, XRD and TG-DSC. Hydroxyapatite addition significantly decreased the dissolution of rare earth elements from monazite in the leach after baking at temperatures above 300 °C. For a bake temperature of 500 °C, the rare earth dissolution in the leach dropped from 80% for monazite alone, to 30% for a 1:1 (w/w) addition of hydroxyapatite. This decrease in rare earth leaching was attributed to the formation of an insoluble thorium and rare earth bearing polyphosphate. The rare earth elements were incorporated into this polyphosphate phase in preference to calcium. At 800 °C, monazite was re-formed, causing a further reduction in rare earth extraction, while simultaneous formation of calcium pyrophosphate (Ca2P2O7) led to an increase in calcium and phosphorus dissolution. The detrimental effect of apatite could be partially overcome by the addition of goethite. Addition of goethite to the acid bake of a monazite/apatite mixture at 500 °C improved the total rare earth dissolution from 29% to 85% in the subsequent leach. Results also demonstrated that the order of reactivity, in terms of formation of polyphosphates is Fe > REE > Ca.

Preparation of Lanthanum by the Lithium-thermic Method

Purification of unwanted impurities from rare earth products was carried out using inorganic and organic precipitating reagents. A 1 M solution of 8-hydroxycholine was used as organic precipitants. The use of organic precipitants forms stable intracomplex compounds with metal cations. Solutions of barium chloride and ammonia solution were used as inorganic precipitants. For the precipitant, specific and highly volatile precipitant reagents were chosen when heated. Iron, aluminum, sodium and sulfate ions were extracted from the product under study, because the chemical composition of the slag contains more of them. Enriched concentrated lanthanum chloride powder was reduced with lithium to lanthanum metal. Lanthanum is obtained in the form of large crystals with a purity of 99.6% by weight.

RARE EARTH METALS: KEY COMPONENTS OF MODERN TECHNOLOGIES

Purpose. The aim of the article is to conduct a comprehensive analysis of the supply routes for rare earth elements and forecast the development of the market for these elements in the current conditions arising from the war and other factors. Methodology of research. The scientific research methodology was used in the process of writing the article to determine generalised synthetic indicators on strategic ways of development and diversification of rare earth elements supply, as well as statistical and graphical methods to analyse the rare earth elements market and forecast supply and demand using time series. Graphs were used to visualise this data. Findings. It has been found that lithium, cobalt, neodymium and graphite, as well as other elements, are becoming increasingly important in modern technologies and everyday life, which leads to an increase in demand for these rare earth elements. The market for rare earth elements is analysed and demand is forecasted to grow in the future due to the development of green technologies and high-tech devices. The ways of developing and diversifying the supply of rare earth elements are investigated, which made it possible to consider them critical due to possible shortages, supply restrictions and the lack of local concentrations for mining. The global REE market is dominated by Chinese production of REE oxides. That is why, in order to avoid potential risks in the supply of rare earth materials, it is important to consider alternative sources and modern processing technologies to meet demand and ensure further production of rare earth elements. Originality. The article analyses the ways of supplying rare earth elements and their important role in modern technologies. A forecast is made, with an analysis of the market for rare earth materials, which will grow in connection with the transition to a climate-neutral economy. The work is relevant because it is the first to analyse the integrated use of rare earth elements in technologies such as lithium-ion battery technology, fuel cell (FCs) technology and permanent magnet motors. Potential risks in the supply of rare earth materials were determined and ways to avoid them were proposed. Practical value. The practical significance of this research is that in the 20th century, rare earth elements became a key to the production of electronics and other technologies. China, which has significant REE resources, controls a large share of global production, which leads to geopolitical tensions in the supply sector. The results of the study can be used to analyse and forecast the ways of supplying rare earth materials, as well as to solve issues related to future challenges and the development of competition for resources. Key words: rare earth elements (REEs); critical material; lithium-ion battery technology; Fuel cells (FCs) technology; permanent magnet motors; statistical method; forecasting.

Selective recovery of rare earth elements by smelting of magnets

Rare earth elements (REEs) play a crucial role in many technologies from daily appliances in cell phones to more advanced wind turbines and electric cars. Permanent magnets account for a quarter of total global REEs production and have high recycling value. In this study, smelting process was used to selectively oxidize REEs in the permanent magnets by adding Fe2O3. This separates REEs into a slag phase from an iron-rich metallic phase. B2O3 was also added to the system as a flux to lower the slag melting temperature. This minimizes REEs loss to the metallic phase and allows a more efficient phase separation. The effect of flux and oxidizing agent addition was investigated on both regular and cerium-rich NdFeB (NdCeFeB) magnets. At 1350 °C and for 1 h, the slag phase was successfully separated from the metallic phase with the addition of 0.8 stoichiometric amount of Fe2O3 and 40 wt% of B2O3. Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDX) analysis reveals that REEs in the magnet do not migrate to the metal phase while the REE-rich slag phase contains almost no iron. After the selective removal of iron into the metallic phase, REEs are recovered from the slag phase through an acid leaching process allowing >99% of REEs recovery. Boron in the magnet can also be recovered as useful boric acid by evaporation and crystallisation technique. The proposed process in this study is reagent and energy-efficient with almost complete valorisation of both NdCeFeB and NdFeB magnets.

Preparation of magnetic oil-based gel microspheres containing di(2-ethylhexyl)phosphoric acid for extraction of scandium ions at low concentrations in aqueous solutions

Extraction of low-concentration rare earths is one of the important paths for the sustainability of the rare earth industry. The research and development of materials suitable for the extraction of rare earth ions at low concentrations is of great significance. Currently, the application of solvent extraction in the rare earth production industry is highly mature. However, it is not economical to use it for the extraction of low concentration rare earths with problems of phase separation and organic phase loss. This work innovatively proposes to encapsulate the extractant and diluent in magnetic oleogel microspheres, which are obtained by solubilizing magnetic poly (phenyl divinylbenzene)(PS-DVB) microspheres with the extractant and diluent.. The magnetic PS-DVB microspheres of 3 ∼ 16 μm were prepared by suspension polymerisation, followed by encapsulation of di(2-ethylhexyl)phosphoric acid (D2EHPA) and dichloroethane in magnetic PS-DVB microspheres using emulsion swelling, and then magnetic oil-based gel microspheres containing D2EHPA with a particle size of 10 ∼ 32 μm were obtained. The magnetic oil-based gel microspheres containing D2EHPA consist of about 96 wt% liquid phase and about 4 wt% solid phase, with D2EHPA accounting for more than 4.19 wt%. The magnetic oil-based gel microspheres are very close to small oil droplets and are superparamagnetic. The magnetic oil-based gel microspheres containing D2EHPA could completely extract 60 ppm of scandium ions(Sc3+) under the conditions of O:A = 1:50,1:60,1:70, and the extraction equilibrium times were 6, 9 and 12 min, respectively. This extractant encapsulation scheme inherits the selectivity of traditional extractants while simultaneously preserving the advantages of rapid extraction by solvent extraction.

Exploring the Unexpected: An AI Model Uncovers Rare Earth Elements

Throughout Earth’s history, powerful geological processes have shaped the planet, formed diverse landscapes, and hidden valuable resources. Like silent architects, these processes play a crucial role in creating the world we see today. One important aspect of this geological story is the formation of critical minerals—essential elements for modern technology. These minerals are not random features but are closely tied to the larger narrative of Earth’s evolution. Scientists and engineers are exploring the connections between geological processes and the creation of critical mineral deposits to understand better how to identify, extract, and produce these deposits to help meet the demand for resources considered the building blocks of an electrified future. Used in various applications, from energy production and national defense to transportation and communication technologies (think batteries for electric vehicles, permanent magnets for wind turbine generators), critical minerals are defined as non-fuel minerals or mineral materials essential to economic or national security and have a supply chain vulnerable to disruption. The International Energy Agency (IEA), in its latest Critical Minerals Market Review, reported that the record deployment of clean energy technologies has propelled the huge demand for critical minerals such as lithium, cobalt, nickel, and copper. “From 2017 to 2022, the energy sector was the main factor behind a tripling in overall demand for lithium, a 70% jump in demand for cobalt, and a 40% rise in demand for nickel,” the report said. “The market for energy transition minerals reached $320 billion in 2022 and is set for continued rapid growth, moving it increasingly to center stage for the global mining industry.” In the US, critical mineral supply chains are heavily dependent on imports. In 2021, the US was 100% import-reliant for 14 of the 50 critical minerals identified by the US Geological Survey (USGS) in 2022. Additionally, according to the USGS, most of the critical minerals that are essential for meeting decarbonization goals have a net import reliance of greater than 50%. Securing Supply of Rare Earth Elements Critical minerals categorized as rare earth elements (REE) are particularly important to reaching decarbonization goals. With a name reminiscent of science fiction superheroes, the lanthanides are a series of 15 elements—plus scandium and yttrium—collectively regarded as REE. REEs range from light (LREE) to heavy (HREE). While not geologically rare, extraction and processing are complex, expensive, and environmentally hazardous. In addition to being a leading source of critical minerals gallium, germanium, and graphite, China dominates REE production and processing. According to a report by The Oxford Institute for Energy Studies, the country is home to some of the most productive and lowest-cost REE-containing geological formations, which the government has been developing since the 1970s. China holds 37% of the world’s REE reserves, as compared to the US, which held only 1% of the reserves in 2019. US critical mineral supply chains have the potential to be disrupted by adverse foreign actions, pandemics, natural disasters, and other global events. For this reason, developing domestic resources to secure supply chains and meet future critical mineral demand has become a national priority, with the signing of Executive Order No. 14017 by US President Joe Biden in February 2021.

Neodymium Metal Production Via Chloride Based Molten-Salt Electrolysis

The extraction and purification of metals such as aluminum has relied on the electrowinning process for decades. The Hall-Héroult process, developed in 1885, utilizes a molten salt electrolyte to electrochemically produce aluminum metal (Al) and carbon dioxide (CO2).1–3 Similar molten salt techniques exist for a variety of other metals including the rare earth metal Neodymium (Nd). Neodymium has seen significant increases in demand from increased production of wind turbines, electric vehicles, and hard disk drives that use neodymium–iron–boron (Nd–Fe–B) permanent magnets. 4,5 The current procedure for neodymium processing uses a neodymium and lithium fluoride molten salt electrolyte with a sacrificial carbon anode to convert neodymium oxide (Nd2O3) and carbon to neodymium metal and CO2.4,6 As an unfortunate byproduct of the fluoride containing molten salt, perfluorocarbons (PFCs) can also be produced simultaneously. The formation of PFCs combined with the emission of other greenhouse gases (CO,CO2) makes the current process dangerous and undesirable from an environmental standpoint. Due to this, few places currently produce neodymium metal and virtually none is produced in the United States, creating supply chain risks with dire consequences.5 An alternative molten salt process has been proposed where rather than directly converting neodymium oxide to neodymium metal, the oxide is first converted to chloride salt form by reaction with hydrochloric acid. The neodymium salt is then dissolved into a chloride salt based melt and neodymium is electroplated via the below set of reactions.7,8 Cathode: 2NdCl3 + 6e- → 2Nd(solid) + 6Cl- Anode: 6Cl- → 3Cl2 + 6e- Overall: 2NdCl3 → 2Nd(solid) + 3Cl2 This process has several distinct advantages. The chlorine reaction eliminates the need for a sacrificial anode material as well as the production of carbon dioxide. The chloride based molten salt also eliminates the formation of PFCs. The chlorine is then recycled to make more hydrochloric acid for use in converting neodymium oxide to chloride.This talk focuses on recent advances to improve purity and lower energy consumption (kWh/kg). We evaluate anode and cathode behavior during this neodymium chloride molten salt process. Over-potential and stability of various anode materials are investigated in order to minimize energy consumption and ensure long life of process materials. A new stable analytic cathode is demonstrated which is lowers chlorine over-potential by more than 200 mV at current density of 250 mA/cm2.The effect of various plating conditions such as current density and substrate material are investigated to determine impact on deposit quality, coulombic efficiency, and metal purity. Highly porous Nd deposits are known to form in chloride molten salt but are undesirable due to the energy required to separate out the high volume fraction of salt remaining in the solid sponge. Effects of temperature and electrolyte composition on deposit morphology are investigated and improvements toward densifying the sponge to minimize post electrolysis purification are reported. This proof of concept work aims to develop a safe, sustainable and environmentally friendly path towards large scale production of rare earth elements. Reactor design and cathode efficiency results are based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy under the Advanced Manufacturing Office, Award Number DE-EE0009434. Anode design work was supported through the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government. Portions of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. T. R. Beck, Electrochem. Soc. Interface, 23, 36–37 (2014).G. G. Botte, Electrochem. Soc. Interface, 23, 49–55 (2014).W. E. Haupin, J. Chem. Educ., 60, 279–282 (1983).M. F. Chambers and J. E. Murphy, Electrolytic production of neodymium metal from a molten chloride electrolyte.B. Sprecher, R. Kleijn, and G. J. Kramer, Environ. Sci. Technol., 48, 9506–9513 (2014).V. S. Cvetković et al., Met. 2020, Vol. 10, Page 576, 10, 576 (2020).R. Akolkar, J. Electrochem. Soc., 169, 043501 (2022).D. Shen and R. Akolkar, J. Electrochem. Soc., 164, H5292–H5298 (2017).