Chromatographic Separation of Rare Earth Elements
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07 ISOTOPE AND RADIATION SOURCES↗
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Assessing and Improving Biooxidation for Acid Generation and Rare Earth Element Extraction
Microorganisms (Acidithiobacillus ferrooxidanns) are effective in oxidizing ferrous ions that can be used to oxidize pyrite and produce sulfuric acid. Many coal waste resources contain significant concentrations of rare earth elements (REE) and critical materials (CM) that can be extracted using sulfuric acid. These coal waste resources often contain significant concentrations of pyrite, which if not utilized or removed present a future environmental liability for potential acid mine drainage. Thus, the combination of pyrite and REE/CM in coal waste provides a significant resource opportunity for sulfuric acid generation that can be utilized using biooxidation. In addition, the pyrite concentrate used for acid generation also contains REE/CM content that is released during biooxidation of the pyrite concentrate that augments the REE/CM release from the main ore being leached with the acid generated from the pyrite. Thus, this approach provides a very significant environmental advantage as well as augmented REE/CM recovery. Although there are many studies associated with biooxidation in relation to mineral oxidation, there is a lack of information regarding the effects of operating parameters on biooxidation performance and optimization for practical applications. In this study, findings from research in assessing and improving biooxidation for acid generation for REE/CM extraction are presented. Results show that bacteria can very effectively and efficiently oxidize ferrous ions to ferric ions, which oxidize pyrite to produce acid for REE/CM extraction. The factors that showed significant impact on biooxidation performance include air flow rate, stirring speed, residence time, solids concentration, and temperature. The dominance of Leptospirillum ferriphilum species was noted in the bioreactor after a prolonged period of operation, although Acidithiobacillus ferrooxidanns was used in the beginning.
Free, Michael L.↗
Development of Leaching Processes for the Recovery of Rare Earth Elements from Acid Mine Drainage Precipitates
Acid mine drainage (AMD) has been a challenge for mine operators to address and has had significant environmental impacts when there is a failure to address it. Fortunately, there is a regulation in the US that requires the treatment of AMD before water can be discharged into the environment. AMD is generated when sulfide minerals are exposed to water and air from mining. The acidic water then leaches metals from the surrounding rock, creating the potential for environmental contamination of this acidic water containing dissolved metals. AMD can contain high concentrations of metals like iron, aluminum, and manganese and also have been shown to contain trace concentrations of critical minerals, including rare earth elements (REEs). This environmental waste stream is now being researched as a potential source for REEs. There is a patented process for processing and extracting REEs from AMD which produces rare earth oxide preconcentrate (REOP) from AMD treatment precipitates and a final stage mixed rare earth oxide (MREO) product. This body of research examines a selective leaching process for each of these products and determines the activation energy associated with the leaching processes. Acid leaching with HCl was examined to selectively leach REEs from REOP while contaminant metals remained in the solid residue. The maximum leaching recovery of the REEs from the REOP was approximately 90% and an activation energy of 6.4 kJ/mol at pH 3.0. Ammonium chloride leaching was examined to selectively remove contaminant metals from a MREO product. The ammonium chloride process successfully leached major contaminant metals in excess of 85% recovery and had a maximum activation energy of 40.0 kJ/mol.
01 COAL, LIGNITE, AND PEAT↗
Hydrothermal Liquid Recovery of Rare Earth Elements and Critical Materials
This project demonstrated the technical viability of using tunable hydrothermal liquid (HTL) solutions to recover valuable minerals from a range of source materials. The effort focused upon rare earth elements (REE) and other minerals critical to the industrial security of the United States. This effort demonstrated, for the first time, that s, supercritical water (SCW) in particular, can: Extract critical and valuable minerals from a range of matrices ranging from rock ore to biomass; The process can be used to recover a wide range of minerals; This novel extraction chemistry can be cheap, simple, and nontoxic/”green”: The chemical extraction uses water, the cheapest industrial acid (sulfuric), and simple salts (i.e. sodium sulfate). However, other acids, salts, and additives could be used as appropriate. This Laboratory Directed Research and Development (LDRD) project identified that the process is complex with many interacting factors, but the benefits are significant if the complexities can be resolved. Challenges remain in the development of this technology and are described in this report. However, the results are positive, and commercial partners have already expressed interest. In summary, a novel, green, inexpensive mineral extraction process has been developed and demonstrated in a small batch reactor system. The effort provided information for an invention disclosure, proposal to DOE, and will support future business development efforts.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Sampling and Characterization of Coal Basins as an Alternative Rare-Earth Element Resource
Conference presentation at TechConnect World Innovation Conference & Expo, Washington, D.C., June 13–15, 2022. The University of North Dakota (UND) through the Energy & Environmental Research Center (EERC) and the Institute for Energy Studies teamed with the University of Kentucky Center for Applied Energy Research, Microbeam Technologies Inc., the Kentucky Geological Survey (KGS), the North Dakota Geological Survey (NDGS), and the mining industry to execute a contract with the U.S. Department of Energy National Energy Technology Laboratory (NETL) to obtain and characterize samples of U.S. domestic precombustion coal and coal-related materials with a minimum concentration of 300 parts per million (ppm) total rare-earth elements (TREEs) as the material is removed from the ground, with no processing other than drying.
01 COAL, LIGNITE, AND PEAT↗
Structure Activity Relationship Approach toward the Improved Separation of Rare-Earth Elements Using Diglycolamides
The separation of adjacent lanthanides continues to be a challenge worldwide because of the similar physical and chemical properties of these elements and a necessity to advance the use of clean-energy applications. In this paper, a systematic structure–performance relationship approach toward understanding the effect of N-alkyl group characteristics in diglycolamides (DGAs) on the separation of lanthanides(III) from a hydrochloric acid medium is presented. In addition to the three most extensively studied DGA complexants [N,N,N',N'-tetra(n-octyl)diglycolamide, TODGA; N,N,N',N'-tetra(2-ethylhexyl)diglycolamide, TEHDGA; N,N'-dimethyl-N,N'-di(n-octyl)diglycolamide, DMDODGA], 12 new extracting agents with varying substitution patterns were designed to study the interplay of steric and electronic effects that control rare-earth element extraction. Subtle changes in the structure around diglycolamide carbonyl oxygen atoms result in dramatic shifts in the lanthanide extraction strength and selectivity. The effects of the chain length and branching position of N-alkyl substituents in DGAs are elaborated on with the use of experimental, computational, and solution-structure characterization techniques.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Fundamental Studies on the Recovery of Rare Earth Elements from Coal and Coal Byproducts (Final Product Report)
The objective of this project was to collect fundamental information that can be used to develop disruptive physical and chemical separation methods that may be used to extract the rare earth elements (REEs) from coal-based feedstocks in a highly efficient, cost-effective, and environmentally benign manner. To meet the stated objective, a set of interrelated fundamental studies have been conducted. The project has been subdivided into three broad areas of tasks as follows, (1) measurement of surface forces in the thin liquid films (TLFs) of water confined between two macroscopic surfaces to establish the optimal conditions for efficiently collecting the ultrafine particles of rare earth minerals (REMs) present in the coal-based feedstocks using the flotation and/or the hydrophobic-hydrophilic separation process(es), (2) identification of the fundamental mechanisms by which REE ions adsorb and desorb on clay minerals present in coal byproducts, and the characterization of the ion-adsorption clays (IACs) present in U.S. coals, and (3) developing methods of extracting the REEs from the REMs and IACs present in US coal byproducts in a cost-effective and sustainable manner.
01 COAL, LIGNITE, AND PEAT↗
Impact of organic acids on extraction of rare earth elements: Mechanisms and optimization
Organic acids are increasingly recognized as an environmentally friendly and efficient selective leaching agent of critical minerals. However, their impact on subsequent extraction processes remains unclear. This study investigates the extraction behavior of rare earth elements (REEs), representative of critical minerals, in the presence of various organic acids, including citric acid, maleic acid, malonic acid, DL-malic acid, L(+)-tartaric acid, and L-ascorbic acid. The results show that organic acids slightly reduce the extraction of REEs but greatly increase the extraction of aluminum (Al³⁺), making it harder to separate REEs from other elements. To avoid this, it is best to keep organic acid concentrations as low as possible in practical applications. However, by optimizing extraction conditions, these negative effects can be minimized. Specifically, adjusting the contact time between solutions allows for efficient REE extraction while limiting unwanted aluminum extraction. Among the acids tested, malonic acid and L(+)-tartaric acid were found to be the most effective for selectively extracting REEs. Mechanistically, organic acids are likely to form complexes with REEs and D2EHPA during extraction, except for Y (III), offering practical guidelines for optimizing REE recovery. Beyond extraction, this study also highlights a way to recover organic acids by precipitating REEs from stripping solutions using oxalic acid, which adds both environmental and economic benefits. Furthermore, these findings provide useful insights for optimizing REE recovery and offer a reference for extracting other critical minerals from solutions containing organic acids.
D2EHPA↗
Heating events in the nascent solar system recorded by rare earth element isotopic fractionation in refractory inclusions
Equilibrium condensation of solar gas is often invoked to explain the abundance of refractory elements in planets and meteorites. This is partly motivated, by the observation that the depletions in both the least and most refractory rare earth elements (REEs) in meteoritic group II calcium-aluminum–rich inclusions (CAIs) can be reproduced by thermodynamic models of solar nebula condensation. We measured the isotopic compositions of Ce, Nd, Sm, Eu, Gd, Dy, Er, and Yb in eight CAIs to test this scenario. Contrary to expectation for equilibrium condensation, we find light isotope enrichment for the most refractory REEs and more subdued isotopic variations for the least refractory REEs. This suggests that group II CAIs formed by a two-stage process involving fast evaporation of preexisting materials, followed by near-equilibrium recondensation. The calculated time scales are consistent with heating in events akin to FU Orionis– or EX Lupi–type outbursts of eruptive pre–main-sequence stars.
58 GEOSCIENCES↗
Detecting rare earth elements via optically detected magnetic resonance (ODMR) and spin-relaxometry using nitrogen vacancy centers in nanodiamonds
Nanodiamonds embedded with nitrogen-vacancy (NV) centers are emerging as powerful tools in quantum sensing due to their remarkable sensitivity to local variations in electromagnetic fields, temperature, and pressure. These point defects in the diamond lattice can be probed using optically detected magnetic resonance (ODMR) and spin relaxometry techniques, allowing for the detection and characterization of magnetic nanoparticles and ions. The sensing mechanism relies on laser-induced excitation of the NV center's non-degenerate triplet ground state, which promotes electrons to an excited state. Subsequent photoluminescence (PL) emission, which is spin-state dependent, is then measured. These spin states are highly responsive to magnetic perturbations in the surrounding environment. By analyzing changes in the ODMR spectra and spin relaxation times, we can effectively monitor how magnetic species influence the NV center's spin dynamics, thus enabling sensitive and selective characterization of nanoscale magnetic materials. These techniques have been applied for the characterization of transition metals and rare earth elements which shows natural ferromagnetic properties.
magnetic nanopartgicles and ions↗
Predicting Rare Earth Element Potential in Produced and Geothermal Waters of the United States via Emergent Self-Organizing Maps
This work applies emergent self-organizing map (ESOM) techniques, a form of machine learning, in the multidimensional interpretation and prediction of rare earth element (REE) abundance in produced and geothermal waters in the United States. Visualization of the variables in the ESOM trained using the input data shows that each REE, with the exception of Eu, follows the same distribution patterns and that no single parameter appears to control their distribution. Cross-validation, using a random subsample of the starting data and only using major ions, shows that predictions are generally accurate to within an order of magnitude. Using the same approach, an abridged version of the U.S. Geological Survey Produced Waters Database, Version 2.3 (which includes both data from produced and geothermal waters) was mapped to the ESOM and predicted values were generated for samples that contained enough variables to be effectively mapped. Results show that in general, produced and geothermal waters are predicted to be enriched in REEs by an order of magnitude or more relative to seawater, with maximum predicted enrichments in excess of 1000-fold. Cartographic mapping of the resulting predictions indicates that maximum REE concentrations exceed values in seawater across the majority of geologic basins investigated and that REEs are typically spatially co-associated. The factors causing this co-association were not determined from ESOM analysis, but based on the information currently available, REE content in produced and geothermal waters is not directly controlled by lithology, reservoir temperature, or salinity.
Engle, Mark A. (ORCID:0000000152587374)↗
Green Approach for Rare Earth Element (REE) Recovery from Coal Fly Ash
Not Available
54 ENVIRONMENTAL SCIENCES↗
Recent advances in acid-free dissolution and separation of rare earth elements from the magnet waste
The availability of REEs is limiting the successful deployment of some environmentally friendly and energy-efficient technologies. In 2019, the U.S. generated more than 15.25 billion pounds of e-waste. Only ~15% of it was handled, leaving ~13 billion pounds of e-waste as potential pollutants. Of the 15% collected, the lack of robust technology limited REE recovery for re-use. Key factors that drive the recycling of permanent magnets based on rare earth elements (REEs) and the results of our research on magnet recycling will be discussed, with emphasis on neodymium and samarium-based rare earth permanent magnets.
36 MATERIALS SCIENCE↗
Surrogate modeling of the leaching process in a rare earth elements recovery plant
The data are summarized in the slides for a poster as presented at the 2024 AIChE annual meeting in San Diego, California, USA. The slides summarize our work on the PrOMMiS project over the past year. The slides describe the systematic design and optimization of a flowsheet for the recovery of critical minerals and rare earth elements. Then, it summarizes the results of our benchmarking of surrogate modeling methodologies for the optimization of these flowsheets.
Fardis, Dimitrios↗
Decision-Making Framework to Evaluate Opportunities for Recovery of Rare Earth Elements and Critical Minerals in Produced Water Networks
Oil and gas development activities require a significant amount of water. Given the environmental impacts associated with high consumption and subsequent disposal of this water, there is a need for strategies to support effective reuse of, treatment of, and/or resource recovery from this produced water. These streams can contain appreciable concentrations of rare earth elements (REE) and critical minerals (CM) (e.g., Lithium), which are critical for many important applications in electronics, technology, manufacturing, energy, and medicine [1]. Along with REE/CM present in produced water, other waste streams such as fly ash from coal-fired power plants and acid mine discharge present other potential sources for recovery of REE/CM [2-4]. And with increases in demand for REE/CM, the need for recovery from wastewater streams is becoming even more important. There is a need to develop effective decision-making tools to evaluate the economic and environmental potential for REE/CM recovery from produced water networks while supporting the needs of drilling and hydraulic fracturing activities. In this work, we present our progress in developing a decision-making framework to efficiently design and operate produced water networks for REE/CM recovery. Our approach considers REE/CM recovery from produced water streams alongside other potential wastewater sources. The models consider the location and capacity of storage and decentralized treatment processes as well as the design and operation of pipeline and transportation networks to connect different sources and effectively schedule inventories, reuse, and recovery opportunities. We focus on the evaluation of opportunities for REE/CM recovery with treatment constraints on composition and flow. We demonstrate this framework with an illustrative case study that features diverse production sites, storage facilities, transportation, and treatment sites. This proposed framework will be deployed in an open-source software package that is compatible with the PARETO framework to deliver analysis and decision-making tools that allow stakeholders to quantitatively evaluate potential opportunities for REE/CM recovery in produced water networks.
Pulsipher, Joshua↗
Life-Cycle Inventory of Critical Materials: Nickel, Copper, Titanium, and Rare-Earth Elements
The United States has developed a list of critical minerals/materials whose sustained and reliable supply is pivotal to the robust functioning of critical industrial sectors. A key concern with these minerals is their environmental effects as a function of their production location. This requires material and energy flow details for their processing steps. This report provides a life-cycle inventory (LCI) for producing four critical minerals and/or material systems (nickel, copper, titanium, and rare-earth elements) incorporated in the updated GREET® (Greenhouse gases, Regulated Emissions, and Energy use in Technologies) model. For these systems, we provide an LCI as a function of production location – domestic (within the United States) and international (geographies from where the US imports these minerals). Our LCI also considers variations in ore grades for nickel and copper. This report also provides an LCI for all intermediate materials used to produce these critical materials.
58 GEOSCIENCES↗
Method embodiments for making lanthanide metal complexes from lanthanide metal oxides and separating the same from heavy lanthanide metal oxides, actinide oxides, and non-lanthanide rare earth element oxides
The present disclosure is directed to method embodiments for making anhydrous lanthanide halide complexes. At least some embodiments comprise making a lanthanide halide complex by reacting a lanthanide metal oxide with an oxygen scavenger and catalyst in the presence of a donor solvent. The method is selective toward light lanthanide metal oxides and thus further provides a method for separating light lanthanide metal oxides from heavy lanthanide metal oxides, actinide oxides, and non-lanthanide rare earth element oxides.
Kiplinger, Jaqueline Loetsch↗
Development of a separation method for rare earth elements using LN resin
The lanthanide elements and isotopes are analytes of significant interest for several nuclear-related fields. Chemical separation among these elements is uniquely challenging due to their nearly identical chemical properties. This difficulty in interelement separation can create obstacles for quantitative radiometric analysis, specifically for isotopes without distinct energy emissions easily measured by gamma spectroscopy, for example Tb-161. Presented in this work is an optimized method for the isolation of individual rare earth elements using Eichrom’s LN resin.
Arrigo, Leah M.↗