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Efficient Recovery of Neodymium from Neodymium–Iron–Boron Magnet: Proceedings of the First Global Conference on Extractive Metallurgy
Supercritical carbon dioxide (sc-CO2) is an emerging green solvent for recovery of metals from secondary resources. The sc-CO2 is a non-polar solvent; thus, a suitable chelating agent is required to accommodate the polarity difference between the solute and solvent during the extraction of metal ions with organometallic compounds. This study investigates four different organophosphorus ligands including triethyl phosphate (TEP), tri-n-butyl phosphate (TBP), tributyl phosphine oxide (TBPO), and trioctyl phosphine oxide (TOPO), and their effect on the extraction of neodymiumNeodymiumfrom NdFeB magnetNdFeB magnet in sc-CO2. A COSMO-vac model is developed to estimate solubility of the four agents in sc-CO2. The results show that the order of solubility is TEP > TBPO ~ TBP > TOPO. The coordination environment of neodymium was determined by UV–Vis spectroscopy, resulting a TEP:Nd = 1, TBP:Nd = 3, TBPO:Nd = 3, and TOPO:Nd = 4 coordination chemistry. The highest extraction for neodymium is achieved with TEP, because of low coordination number which results in less hydrophobic interactions between aliphatic functionalities. Also, the smaller micellar assemblies have a higher solubility in sc-CO2; thus, a higher extraction efficiency is achieved.
Some rare earth elements (REEs) are classified under critical materials, i.e., essential in use and subject to supply risk, due to their increasing demand, monopolistic supply, and environmentally unsustainable and expensive mining practices. To tackle the REE supply challenge, new initiatives have been started focusing on their extraction from alternative secondary resources. This study puts the emphasis on technospheric mining of REEs from bauxite residue (red mud) produced by the aluminum industry. Characterization results showed the bauxite residue sample contains about 0.03 wt% REEs. Systematic leaching experiments showed that concentrated HNO3 is the most effective lixiviant. However, because of the process complexities, H2SO4 was selected as the lixiviant. To further enhance the leaching efficiency, a novel process based on microwave pretreatment was employed. Results indicated that microwave pretreatment creates cracks and pores in the particles, enabling the lixiviant to diffuse further into the particles, bringing more REEs into solution, yielding of 64.2% and 78.7% for Sc and Nd, respectively, which are higher than the maximum obtained when HNO3 was used. This novel process of “H2SO4 leaching-coupled with-microwave pretreatment” proves to be a promising technique that can help realize the technological potential of REE recovery from secondary resources, particularly bauxite residue.
Raw materials form the basis of Europe's economy to ensure jobs and competitiveness, and they are essential for maintaining and improving quality of life. Although all raw materials are important, some of them are of more concern than others, thus the list of critical raw materials (CRMs) for the EU, and the underlying European Commission (EC) criticality assessment methodology, are key instruments in the context of the EU raw materials policy. For the next update of the CRMs list in 2017, the EC is considering to apply the overall methodology already used in 2011 and 2014, but with some modifications. Keeping the same methodological approach is a deliberate choice in order to prioritise the comparability with the previous two exercises, effectively monitor trends, and maintain the highest possible policy relevance. As the EC's in-house science service, the Directorate General Joint Research Centre (DG JRC) identified aspects of the EU criticality methodology that could be adapted to better address the needs and expectations of the resulting CRMs list to identify and monitor critical raw materials in the EU. The goal of this paper is to discuss the specific elements of the EC criticality methodology that were adapted by DG JRC, highlight their novelty and/or potential outcomes, and discuss them in the context of criticality assessment methodologies available internationally.
In recent decades, rare-earth elements (REEs) have seen a considerable increase in usage in modern technologies and the so-called green energy sources. The REEs are currently regarded to be among the most critical elements by the European Union (EU) and the United States (USA). Large investments are made in the research of recycling of the REEs from end-of-life products and E-scrap. One potential source for recycling of larger amounts of neodymium and dysprosium are end-of-life neodymium magnets. In this work, the selective extraction of REEs from a sulfuric media leachate (containing Nd, Dy, Pr, Gd, Co, and B) obtained by selective roasting of NdFeB waste and leaching was investigated. The extracting agent D2EHPA (di-(2-ethylhexyl) phosphoric acid) diluted in Solvent 70, hexane, octane, cyclohexanone, chloroform, 1-octanol, and toluene was used for the investigation of the effects of using different diluents on the extraction of REEs and the separation between the light and the heavy REEs. The concentrations of D2EHPA in the used diluents were 0.3, 0.6, 0.9, and 1.2 M. The highest separation factors between the heavy and the light REEs were achieved using 0.3 M D2EHPA in hexane, while no B or Co extraction was measurable. The REEs were completely extracted as a group using 0.9 M or 1.2 M D2EHPA in either octane or hexane, also with no B or Co extraction. The aliphatic nonpolar diluents showed better properties than the aromatic and polar ones. The complete stripping of REEs from the loaded organic phases was proven to be efficient using hydrochloric acid at concentrations of 2 M or higher.
NdFeB permanent magnets have different life cycles, depending on the applications: from as short as 2–3 years in consumer electronics to 20–30 years in wind turbines. The size of the magnets ranges from less than 1 g in small consumer electronics to about 1 kg in electric vehicles (EVs) and hybrid and electric vehicles (HEVs), and can be as large as 1000–2000 kg in the generators of modern wind turbines. NdFeB permanent magnets contain about 31–32 wt% of rare-earth elements (REEs). Recycling of REEs contained in this type of magnets from the End-of-Life (EOL) products will play an important and complementary role in the total supply of REEs in the future. However, collection and recovery of the magnets from small consumer electronics imposes great social and technological challenges. This paper gives an overview of the sources of NdFeB permanent magnets related to their applications, followed by a summary of the various available technologies to recover the REEs from these magnets, including physical processing and separation, direct alloy production, and metallurgical extraction and recovery. At present, no commercial operation has been identified for recycling the EOL NdFeB permanent magnets and the recovery of the associated REE content. Most of the processing methods are still at various research and development stages. It is estimated that in the coming 10–15 years, the recycled REEs from EOL permanent magnets will play a significant role in the total REE supply in the magnet sector, provided that efficient technologies will be developed and implemented in practice.
Today’s world relies upon critical green technologies that are made of elements with unique properties, irreplaceable by other materials. Such elements are classified under strategic materials; examples include rare earth elements that are in increasingly high demand, but facing supply uncertainty and near zero recycling. To tackle the sustainability challenges associated with rare earth elements supply, new strategies have been initiated to mine these elements from secondary sources. Waste electrical and electronic equipment contain considerable amounts of rare earth elements; however, the current level of their recycling is less than 1%. Current recycling practices use either pyrometallurgy, which is energy intensive, or hydrometallurgy that rely on large volumes of acids and organic solvents, generating large volumes of environmentally unsafe residues. This study put the emphasis on developing an innovative and sustainable process for the urban mining of rare earth elements from waste electrical and electronic equipment, in particular nickel metal hydride battery. The developed process relies on supercritical fluid extraction utilizing CO2 as the solvent, which is inert, safe, and abundant. This process is very efficient in a sense that it is safe, runs at low temperature, and does not produce hazardous waste, while recovering about 90% of rare earth elements. Furthermore, we propose a mechanism for the supercritical fluid extraction of rare earth elements, where we considered a trivalent rare earth element state bonded with three tri-n-butyl phosphate molecules and three nitrates model for the extracted rare earth tri-n-butyl phosphate complex. The supercritical fluid extraction process has the double advantage of waste valorization without utilizing hazardous reagents, thus minimizing the negative impacts of process tailings.
Nd-Fe-B permanent magnets are a strategic material for a number of emerging technologies. They are a key component in the most energy efficient electric motors and generators, thus, they are vital for energy technologies, industrial applications and automation, and future forms of mobility. Rare earth elements (REEs) such as neodymium, dysprosium and praseodymium are also found in waste electrical and electronic equipment (WEEE) in volumes that grow with the technological evolution, and are marked as critical elements by the European Commission due to their high economic importance combined with significant supply risks. Recycling could be a good approach to compensate for the lack of rare earths (REs) on the market. However, less than 1% of REs are currently being recycled, mainly because of non-existing collection logistics, lack of information about the quantity of RE materials available for recycling and recycling-unfriendly product designs. To improve these lack of information, different waste streams of electrical and electronic equipment from an industrial recycling plant were analyzed in order to localize, identify and collect RE permanent magnets of the Nd-Fe-B type. This particular type of magnets were mainly found in hard disk drives (HDDs) from laptops and desktop computers, as well as in loudspeakers from compact products such as flat screen TVs, PC screens, and laptops. Since HDDs have been investigated thoroughly by many authors, this study focusses on other potential Nd-Fe-B resources in electronic waste. The study includes a systematic survey of the chemical composition of the Nd-Fe-B magnets found in the selected waste streams, which illustrates the evolution of the Nd-Fe-B alloys over the years. The study also provides an overview over the types of magnets integrated in different waste electric and electronic equipment.
Many technologies relied upon by modern society, such as portable electronics and renewable energy systems, require the use of rare-earth elements (REEs). The global demand for REEs is increasing rapidly, and new developments for their recovery from secondary sources have been sparked. Phosphogypsum (PG), the byproduct of phosphoric acid production, is considered a secondary source for REEs. This research builds upon previous studies investigating the hydrometallurgical recovery of REEs from PG via acid leaching. The current study put the emphasis on developing processes to recover consumed acid in the leaching process. Here we propose an innovative process that relies upon the addition of calcium sulfate anhydrite seeds to the leached solution. Anhydrite seeding results in the rejection of calcium sulfate from the leached solution and reduced calcium concentration. Because the REE leaching efficiency is controlled by the solubility limit of PG, which is correlated to the calcium concentration, the drop i...
Rare earth element (REE) containing neodymium-iron-boron (NdFeB) magnets play a major role in green technologies, including motor and generator applications. Recycling of REE from NdFeB magnets is expected to be beneficial from an environmental point of view compared to the production of magnets using primary REE currently practiced. This study gives a broad overview of global recycling potentials from end-of-life magnets from eleven different application groups and industrial scrap, quantified through dynamic material flow analysis. Data was obtained through a review of the literature, complemented by expert estimations. Recycling potentials achievable for REEs used in NdFeB magnets, namely neodymium (Nd), praseodymium (Pr), terbium (Tb) and dysprosium (Dy), were calculated for years 2020–2030, derived from two demand scenarios to reflect uncertainties in historic NdFeB demand figures and future demand development, taking into account the recent success in heavy REE reduction efforts. The most important NdFeB application groups in terms of recycling potentials are identified. The modelled scenarios show that between 18 and 22 percent of global light REE (Nd and Pr) and 20–23 percent of heavy (Dy and Tb) REE demand for use in NdFeB magnet production can be met by supply from secondary sources from end-of-life magnets and industrial scrap in years 2020, 25 and 30 (ranges of values for individual years and scenarios).
This manuscript describes the development of an efficient process for the recovery of rare earth elements from materials mixtures such as in motors with a recovery rate of >80%. While heat treatment is required for processing, all other steps can be performed at room temperature, thus resulting in a process designed for energy efficiency. Selective dissolution enables efficient separation of steel and copper by taking advantage of the different reduction potentials of the materials in the mixture, while selective precipitation of RE salts is the key for obtaining pure RE products. Overall, the established process applies green chemistry principles for designing a hydrometallurgical process.
Let's start with a few definitions. There are three magnetic vectors: (1) H Magnetic field (2) M Magnetization (3) B Magnetic induction There is some confusion in the literature over units. SI units are now the preferred units over the older CGS . Confusion prevails because there are two ways that magnetostatics is presented: 1. fictitious magnetic poles (CGS: centimeter, gram, second) 2. current sources (SI: systéme internationale) As a result, the form of many of the basic equations are different between the two systems. What this all means is that some arbitrary constant has units in one system but is equal to unity and dimensionless in the other system. There are also factors of 4 π floating around. The difference between the pole and current approach is only significant in the subject of units. The older (pre 1980) paleomagnetic and rock magnetic literature is primarily in CGS units. Because SI are now the units of choice, we begin with current loops. Consider a loop of radius r and current i, roughly equivalent to an atom with orbiting electrons.
Neodymium-iron-boron (Nd-Fe-B) magnets were most widely applied to permanent magnetic products in the world due to their high magnetic force. The increasing growth of scrap Nd-Fe-B magnets resulted in disposal problems and the reduction of neodymium (Nd) valuable resources. In this study, we developed a simple hydrometallurgical precipitation process with pH adjustment to separate and recover Nd 100 pct recovery from scrap Nd-Fe-B magnets. Several physical and chemical methods such as demagnetization, grinding, screening, and leaching processes were also adopted to investigate the recovery of Nd and other metals from scrap Nd-Fe-B magnets. The leaching process was carried out with four leaching reagents such as NaOH, HCl, HNO3, and H2SO4. Batch studies were also conducted to optimize the leaching operating conditions with respect to leaching time, concentration of leaching reagent, temperature, and solid/liquid ratio for both HCl and H2SO4 leaching reagents. Nd was successfully separated and recovered with 75.41 wt pct from optimized H2SO4 leaching solution through precipitation. Further, the purity and weight percentage of the obtained Nd product was analyzed using scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS) analysis. An X-ray diffraction (XRD) study confirmed the obtained product of Nd was in the form of NdOOH and Nd(OH)3.
Davenport, rare earths: science, technology, production and use
- J Lucas
- P Lucas
- Le Mercier
- T Rollat
- Jacques Lucas