Production Of Rare Earth Metals Research Articles

(Invited) Rare Earth 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) from aluminum oxide (Al2O3) and carbon.1–3 Similar molten salt techniques have been developed for a variety of other metals including the rare earth metal Neodymium (Nd). Neodymium is of particular interest recently with significant increases in demand being driven by the increased production of technologies such as wind turbines, electric vehicles, and hard disk drives that require neodymium in the form of 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 a significant amount of other greenhouse gases (CO,CO2) make the current process for neodymium electrowinning is dangerous and undesirable from an environmental standpoint. However rare earth metal production remains profitable enough that illegal processing operations make up a significant portion of the world’s supply of rare earth elements like neodymium. 7,8 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 in which the fluoride salts have been replaced with chloride salts consisting of lithium chloride (LiCl) and potassium chloride (KCl). 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 the LiCl-KCl molten salt and neodymium is electroplated via the below set of reactions.9,10 Cathode: 2NdCl3 + 6e- → 2Nd(solid) + 6Cl- Anode: 6Cl- → 3Cl2 + 6e- Overall: 2NdCl3 → 2Nd(solid) + 3Cl2 This process has several distinct advantages. Utilizing 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 produced could then be 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). Our work evaluates anode and cathode behavior during this neodymium chloride molten salt process in order to determine its viability. Overpotential and stability of various anode materials are investigated in order to minimize energy consumption and ensure long life of process materials. 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. Additional purification techniques such as vapor distillation procedures are developed to ensure a product that is viable for industrial use. 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).H. Vogel, B. Friedrich, H. Vogel, and B. Friedrich, Int. J. Nonferrous Metall., 6, 27–46 (2017).J. C. K. Lee and Z. Wen, Nat. Sustain. 2018 110, 1, 598–605 (2018).R. Akolkar, J. Electrochem. Soc., 169, 043501 (2022).D. Shen and R. Akolkar, J. Electrochem. Soc., 164, H5292–H5298 (2017).

Редкоземельная промышленность – реализовать имеющиеся возможности

The article analyzes the features of the formation and development of the industry associated with the extraction and processing of rare earth metals (REM). REM are widely used in modern high-tech devices and products. A distinctive feature of REMs is the integration of their extraction and production into global chains. At present, China has a dominant position in the REM supply market. This situation is a consequence of state policy, which includes a wide range of support and lobbying measures. Russia has one of the largest potential for the extraction and production of rare earth metals, but this potential is not being properly realized. The volume of extraction and production is small, and a significant part of the production is exported. Russia is forced to import many types of highly purified rare earth metals. Authors believe that the current economic situation – a change in the configuration of global REM value chains – creates a unique chance for Russia to bring potential opportunities in line with its real situation.

Analysis of the use of rare earth metals in ferrous metallurgy of Russia and world

The analysis of the current state of production of rare earth metals (REM) in Russia and in the world was made. Information about REM production in different countries of the world and about new foreign projects for REM production and processing is provided. The article presents the balance of production, export and import of raw materials and products with REM, including scandium and yttrium, in Russia. The maximum volume of REM consumption in Russia was calculated taking into account imported products with REM. This data was compared with other countries, including the former USSR. Much attention is paid to the use of REM in metallurgy. Data on the influence of REM on the properties of cast iron and steel are presented. Information is given about the forms of REM used for their use in the Russian ferrous metallurgy. We have studied the structure of REM consumption in ferrous and non-ferrous metallurgy. On the example of two enterprises (one of them specializes in mass production, and the second – on production of special steels), the structure of REM consumption for steel alloying was studied by type and scope of its application. The development peculiarities of REM consumption in Russian ferrous metallurgy were investigated. The volume of consumption was calculated; data on imports of raw materials with REM for metallurgy and the producers of ferroalloys with REM in Russia is given. We have analyzed the spectrum of steel products with REM. A comparison of the consumption of REM in the metallurgy of Russia and foreign countries is presented. The reasons for insufficient consumption of REM in the Russian metallurgy are considered, an assessment is given on the change in production volumes of certain types of steel and cast iron, and recommendations are made on the growth of REM consumption in metallurgy.

PRODUCTION OF RARE EARTH METALS IN THE INTERESTS OF DEFENSE AND THE IMPACT OF REGULATORY RESTRICTIONS ON THE INDUSTRY IN THE UNITED STATES

The article presents the results of the analysis of the global market of rare earth metals for the needs of the armed forces abroad. The Article also estimates the direction of development of the US legislative system in this area, as well as presents the results of comparing the levels of development of production of rare earth metals in the US and China.

Estimating direct CO2 and CO emission factors for industrial rare earth metal electrolysis

Rare earth (RE) metals are now being widely applied in new material industries with rapidly increasing production. However, there is limited research on greenhouse gas emission factors from RE metals production by electrolysis and currently no method exists to account for this industry’s CO2 emissions in the ‘2006 IPCC Guidelines for National Greenhouse Gas Inventories’. This study employed two independent methods to determine direct carbon emission factors for industrial rare earth metals production by molten-salt electrolysis: continuous emissions monitoring by FTIR and time-integrated sampling with offline lab analysis, both measuring CO2 and CO concentrations in the exhaust gases from Pr-Nd, Dy-Fe and La potlines in three companies in China. The study confirmed that CO2 contributes >97% of the total carbon emission factor. Direct carbon emissions per tonne RE metal electrolysis is equivalent to one tenth to a half of the emission factor for aluminum production (due to much lighter molar mass of Al) but is similar on a mole basis (carbon emissions per mole metal). Emission factors vary with the type of rare earth metal or alloy produced and from one facility to another, ranging from 165.0 to 672.4 kg/t-RE metal for CO2, 3.00 to 8.23 kg/t-RE metal for CO and 46.4 to 186.8 kg/t-RE metal for total carbon. Direct CO2 and CO emission factors from the two exhaust gas monitoring methods agreed well considering the uncertainties.

Assessing the environmental footprint of the production of rare earth metals and alloys via molten salt electrolysis

Much attention has been given in recent years to the rare earth elements, considering their significance in a number of high-tech and clean energy applications. Despite the environmental destructive operations to produce rare earth elements, limited life cycle assessment investigations have yet been carried out. This is specifically true regarding the reduction of rare earth compounds to produce rare earth metals and alloys. In combination with mass/energy balance and stoichiometry, life cycle inventories of molten slat electrolysis process were developed in this study using industrial datasets gathered from different facilities in China and the Ecoinvent v3 database. The results showed that although mining, chemical treatment, and solvent extraction stages are the dominant contributors to the whole neodymium metal production process for most impact categories, molten salt electrolysis significantly impacts ecotoxicity, carcinogenics, non-carcinogenics, and eutrophication categories. Moreover, neodymium fluoride production, electricity consumption, and molybdenum use in cathodes are the dominant contributors in the molten salt electrolysis process. In addition, the neodymium metal production at facilities which produce larger amounts of heavy rare earth metals/alloys demonstrates relatively lower impacts on all impact categories compared to the production of neodymium metal at refining facilities which produce light rare earth metals/alloys.

Estimating perfluorocarbon emission factors for industrial rare earth metal electrolysis

Rare earth (RE) metals have been widely applied in new materials, leading to their drastic production increase in the last three decades. In the production process featured by the molten-fluoride electrolysis technology, perfluorocarbon (PFC) emissions are significant and therefore deserve full accounting in greenhouse gas (GHG) emission inventories. Yet, in the ‘2006 IPCC Guidelines for National Greenhouse Gas Inventories’, no method currently exists to account for PFC emissions from rare earth metal production. This research aims to determine emission factors for industrial rare earth metals production through on-site monitoring and lab analysis of PFC concentrations in the exhaust gases from rare earth metal electrolysis. Continuous FTIR measurements and time-integrated samples (analysed off-site by high-precision Medusa GC–MS) were conducted over 24–60 h periods from three rare earth companies in China, covering production of multiple rare earth metals/alloys including Pr-Nd, La and Dy-Fe. The study confirmed that PFC emissions are generated during electrolysis, typically in the form of CF4 (∼90% wt of detected PFCs), C2F6 (∼10%) and C3F8 (<1%); trace levels of c-C4F8 and C4F10 were also detected. In general, PFC emission factors vary with rare earth metal produced and from one facility to another, ranging from 26.66 to 109.43 g/t-RE for CF4 emissions, 0.26 to 10.95 g/t-RE for C2F6, and 0.03 to 0.27 g/t-RE for C3F8. Converted to 211.60 to 847.41 kg CO2-e/t-RE for total PFCs, this emissions intensity for rare earths electrolysis is of lower (for most RE production) or similar (Dy-Fe production) level of magnitude to industrial aluminium electrolysis.

Cement-free Binders for Radioactive Waste Produced from Blast-furnace Slag using Vortex Layer Activation Technology

The paper addresses the issue of recycling granulated blast-furnace slag (gBFS) as a source for production of cement-free binder materials for further usage in rare-earth metals production for radioactive waste disposal. The use of the vortex layer activator was provided as main technique allowing to produce high-dispersed chemically activated binders. The paper examines the effect of processing conditions on the physical-chemical and mechanical properties of the resulting BFS-based cement-free materials and gBFS-based concretes.

Determination of thermodynamic stability of neodymium chloride hydrates (NdCl3·xH2O) by dynamic transpiration method

Synthesis of rare earth chlorides in the anhydrous form is crucial for the production of rare earth metals in the electrolysis process. Knowledge of thermal stability of rare earth chloride hydrates is therefore of great interest which may help in deciding the experimental condition for its production. In this study, dehydration scheme of NdCl3·6H2O(s) was investigated by thermal analysis techniques. Thermal decomposition of NdCl3·6H2O(s) to NdCl3(s) is found to proceed through the formation of NdCl3·3H2O(s), NdCl3·2H2O(s) and NdCl3·H2O(s) in the temperature range 330–450 K. Thermodynamic stability of the NdCl3·6H2O(s) and its intermediate products has been determined by measuring the vapor pressure of water over the compounds employing dynamic transpiration technique. The standard molar Gibbs energy of formation of NdCl3·6H2O(s) and its intermediate hydrates have been derived from the measured vapor pressure data.

Trends in the development of industrially assimilated renewable energy: the problem of resource restrictions

An analysis of the dynamics of the development of wind and solar energy and potential resource restrictions of the dissemination of these technologies of energy generation associated with intensive use of rare earth metals and some other mineral resources are presented. The technological prospects of various directions of decisions of the problem of resource restrictions, including escalating of volumes of extraction and production of necessary mineral components, creating substitutes of scarce materials and development of recycling are considered. The bottlenecks of each of the above-mentioned decisions were founded. Conclusions are drawn on the prospects of development of the Russian high-tech sectors of the economy in the context of the most probable decisions of the problem of resource restrictions of wind and solar energy. An increase in extraction and production of rare earth metals and some other materials, stimulation of domestic research and development (R&D) to create the permanent magnets of new types and new technologies of wind-powered generation, and reduction of the resource-demand and technology development of recycling the components of power equipment are the most prospective directions of progress. The innovations in these directions will be in demand on the European, Chinese, and North American markets in the near decades due to the end of the life cycle (approximately 30 years) of wind and solar energy projects started at the turn of the 20th–21st centuries (the beginning of exponential growth in plants). The private investors and relevant regional and federal government agencies can use the qualitative characteristics of the dynamics of industrially assimilated renewable energy to choose the most promising investment orientations in energy projects and selection of the most economically sound development methods of energy and related industries.

Rare-earth elements recovery from post-consumer hard-disc drives

The recovery of neodymium from post-consumer products is gaining significant interest. To study the recycling feasibility of neodymium in end-of-life (EOL) computer hard disc drives (HDDs), NdFeB magnets were collected using a steel grate during commercial shredding, followed by thermal demagnetisation, grinding and screening to yield an upgraded scrap. Two metallurgical extraction routes were investigated. The first is a high temperature molten slag extraction followed by H2SO4 leaching at room temperature. Both CaO–SiO2–Al2O3 and CaO–CaF2 slag systems were tested with more than 99% rare earths recovery, but with incomplete leaching. In the second route, the upgraded scrap was directly leached to dissolve 97% rare earth content. In both cases, 98% of the rare earths in the leach solution were subsequently converted into a high purity (98·4%) rare earths double salt (NaNd(SO4)2·H2O) that can be converted to either RF3 or R2O3, the two common raw materials in the production of rare earth metals.

Rare Earth Metals: Resourcefulness and Recovery

When we appreciate the digital revolution carried over from the twentieth century with mobile communication and the Internet, and when we enjoy our high-tech lifestyle filled with iDevices, hybrid cars, wind turbines, and solar cells in this new century, we should also appreciate that all of these advanced products depend on rare earth metals to function. Although there are only 136,000 tons of annual worldwide demand, (Cho, Rare Earth Metals, Will We Have Enough?)1 rare earth metals are becoming such hot commodities on international markets, due to not only to their increasing uses, including in most critical military hardware, but also to Chinese growth, which accounts for 95% of global rare earth metal production. Hence, the 2013 technical calendar topic, planned by the TMS/Hydrometallurgy and Electrometallurgy Committee, is particularly relevant, with four articles (including this commentary) contributed to the JOM October Issue discussing rare earth metals’ resourcefulness and recovery.

Powerful Pull To New Magnets

If necessity is the mother of invention, science and technology must be due soon to give birth to new materials and methods for making powerful permanent magnets. The magnets are crucial to an enormous number of products in the automobile, electronics, power-generation, and clean-energy industries. But worldwide, it has been difficult to secure the supply of neodymium, dysprosium, and other rare-earth metals in these powerful magnets, which are stronger yet much smaller than those made with other materials. Recently rare-earth metal prices have fluctuated wildly. In 2010, many publications, including this one, reported on China’s global monopoly on production of rare-earth metals and oxides and the country’s plans to drastically cut exports ( C&EN, Aug. 30, 2010, page 9). The news caused demand for and prices of these materials, especially of dysprosium, one of the scarcest rare-earth metals, to soar. But then other market factors caused prices to fall sharply. ...

Combined approaches for comprehensive processing of rare earth metal ores

Technologies for processing rare earth ores (Chuktukon deposits, East Siberia, Russia) have been developed. The ores are composed of iron-manganese oxides and contain 3–7% of rare-earth oxides in the phosphate form (turnerite, florencite) and 0.5–1% of niobium oxide (chalcolamprite). These ores are refractory and do not lend themselves to concentration, therefore various processes for their direct chemical processing have been considered. A number of investigations to estimate the technological behavior of the Tomtor and Chuktukon ores, and to develop various processes for their treatment, have been carried out. Two approaches for processing the Chuktukon ores have been suggested. The first one comprises extraction of the rare earth metals and production of a niobium concentrate; the second one provides a method for processing the complex ores resulting in the production of rare earth metals, iron and manganese alloys.

Thermal dehydration of lanthanum chloride heptahydrate: thermodynamic approach

Production of rare-earth metals from molten chloride electrolysis demands the use of anhydrous chloride in order to increase current efficiency. The main difficulty in obtaining these chlorides is due to oxychloride formation. Any thin film of the oxychloride or oxide will tend to inhibit the reduction process. The main purpose of this work was to develop an operational diagram related to the dehydration of lanthanum chloride heptahydrate. This diagram agrees with previous experimental data which have shown that dehydration of light rare-earth chlorides can be effective at relatively low temperatures in a dry HCl gas atmosphere.

Recovery of Rare Earths from Magnet Sludge by FeCl&lt;SUB&gt;2&lt;/SUB&gt;

A large amount of neodymium magnet sludge is generated during the manufacture process. Because the sludge is considerably contaminated by oxygen, it is difficult to reuse it as it is. The present basic study has been carried out to establish efficient recycling process of the sludge. The rare earths in the neodymium magnet sludge were extracted by chlorination with FeCl2. An activated carbon was used as a de-oxidation reagent. Metallic iron in the sludge was not chlorinated because the iron monochloride is not stable. The extracted rare earth chlorides were easily separated from Fe-alloy and the excess of FeCl2 by vacuum distillation. In this study, 96% of neodymium and 94% of dysprosium in the sludge were extracted into chloride phase. By the vacuum distillation, a mixture of neodymium and dysprosium trichlorides of 99.2% purity was recovered with the rare earth element’s yield of 76% for the charged sludge. In addition, it was confirmed that the rare earth chlorides can be converted to the corresponding oxides by a pyrohydrolysis reaction accompanied by a formation of HCl gas. The HCl gas can chlorinate metallic iron to FeCl2. Therefore, a new recycling process for rare earth magnet waste can be realized as a chlorine circulation type process. During the process, only carbon and water are consumed, and there are no toxic pollutants. Moreover, the obtained rare earth oxide can be directly used as raw material in the oxide electrolysis, which is the conventional industrial reduction process for rare earth metal production.

Rare-earth metal prices in the USA ca. 1960 to 1994

Rare-earth metal prices were compiled from the late 1950s and early 1960s through 1994. Although commercial demand for rare-earth metals began in 1908, as the alloy mischmetal, commercial quantities of a wide range of individual rare-earth metals were not available until the late 1950s.The discovery of a large, high-grade rare-earth deposit at Mountain Pass, CA, USA, in 1949, was significant because it led to the production of commercial quantities of rare-earth elements that reduced prices and encouraged wider application of the materials.The availability of ore from Mountain Pass, and other large rare-earth deposits, especially those in Australia and China, has provided the world with abundant resources for rare-earth metal production. This availability, coupled with improved technology from Government and private-sector metallurgical research, has resulted in substantial decreases in rare-earth metal prices since the late 1950s and early 1960s.Price series for the individual rare-earth metals (except promethium) are quoted on a kilogram basis from the late 1950s and early 1960s through 1994. Prices are given in US dollars on an actual and constant dollar basis. Industrial and economic factors affecting prices during this time period are examined.

Electrochemistry of rare earth fluoride molten salts

This study deals with fundamental research on the production of rare earth metals by electrolysis. We use fluoride fused salts and rare earth oxides as raw materials. In the design of our electrolytic cell we have to know the types of electrochemical reaction, the critical current densities and the melting points of the fused salts. We have measured the polarization curves and melting points of the electrolytes and we discuss the electrochemical reactions of rare earth oxides and fluoride fused salts. We have confirmed the reactions of oxygen evolution, fluorine evolution and electrodeposition of rare earth metals or alloys. The anodic critical current density of the cerium molten salt is 9 A cm −2 at 890°C and that of the neodymium molten salt is 1.6 A cm −1 at 920°C.

希土類金属の製造とそのリサイクル

希土類金属の製造とそのリサイクル

Neodymium Production Processes

This overview describes the major processes for rare earth metals production, including chloride electrolysis for producing cerium, lanthanum and misch metal; oxide electrolysis for producing neodymium metal and its alloys; calciothermic reduction for producing neodymium commercially; a reduction-diffusion process for making powders of SmCO5; and a co-reduction process for producing powders of rare earth metal alloys. A new molten salt extraction process, “NE0CHEM,” has been developed by which neodymium metal or its alloys can be produced by the reduction of Nd203, with sodium in the presence of CaCl2 by the reaction Nd2O3 + 3 CaCl2 + 6 Na → 2 Nd + 3 CaO + 6 NaCl. In comparison to existing processes, the proposed process holds great promise toward lowering the cost of neodymium.