Separation Of REEs Research Articles

A simplified rare earth element mining project cost estimator - a new tool for evaluating future mine supply

AbstractRare earth elements (REE) are essential for the future of electric vehicles and renewable energy production, but currently there is limited REE production outside of China. Forecasting global future supplies of REE often relies on the valuation of advanced mining projects to assess if projects will initiate production. Classical valuation methods, such as net present value (NPV), require knowledge of initial capital and operating expenditures to assess the economic feasibility of a given project. Typical industry unit expenditure projections are highly precise but are extremely project dependent and require detailed knowledge of a site that is far beyond the level that a domestic and/or global supply-demand model can obtain. To model future REE supplies we developed a new globally representative, simplified, mining project cost model that can be used to approximate the capital and operating expenditures of greenfield REE mining projects. Results from this model allow users to estimate expenses of open-pit and underground mines with mineral processing operations that range from solely beneficiation to individual REE separation. Using our new model and an estimate of NPV, we evaluate several REE mining projects and assess the economic variables impacting the likelihood for these projects to advance to the production stage. Of 12 assessed projects located outside of China, in the early to advanced development stages, nine had positive NPV at 2011 peak REE prices, but none had positive NPV when prices reached bottom in 2016. Two projects yielded positive NPV’s using 2022 and projected 2028 prices. The viability of these projects given the impact of the volatility in REE prices explains the high uncertainty in the future supply for these mineral commodities.

Antisolvent crystallization of rare earth sulfate hydrates: Thermodynamics, kinetics and impact of iron

The thermodynamics and kinetics of ethanol antisolvent crystallization of rare earths from sulfate solutions has been explored, with a view towards separating the rare earths as part of a NdFeB magnet recycling process. The solubility of single and binary metal (Nd, Pr, Fe) phases in aqueous ethanol solutions has been determined. The impact of Fe and Pr on the crystallization of Nd is evaluated, the oxidation kinetics of Fe(II) to Fe(III) quantified, and the influence of Fe oxidation state on the thermodynamics and kinetics of crystallization investigated. Oxidation to Fe(III) is slow, with a half life of approx. 600 h. For pure Nd, the solubility of the obtained, stable sulphate octahydrate decreases exponentially with increased molar organic:aqueous (O/A) ratio, and is well described by the OLI model until O/A=0.2. Pr crystallizes as an isostructural octahydrate with similar solubility. Fe(II) precipitates as a mixed solid phase, with a solubility approximately 40 times higher than the rare earths at O/A=0.2. Fe(III) solutions exhibit liquid–liquid phase separation without precipitation at all evaluated concentrations. Nd and Pr coprecipitate together in proportion to their relative concentrations, with Pr precipitating at concentrations well below its pure component solubility. Fe(II) does not precipitate with Nd at O/A≤0.2 even at high concentration, with significant precipitation as separate particles at higher O/A for all concentrations. The crystallization kinetics and the morphology of the Nd phase is affected by the Fe oxidation state. The work highlights the potential of antisolvent crystallization for selective and efficient separation of REE from Fe.

Synergistic Nanoarchitectonics: Precision Membrane Engineering for Rare Earth Selective Separation

AbstractRare earth elements (REEs) are vital in high‐tech industries and defense due to their strategic significance. Crafting an efficient membranes channel for REE separation poses a significant challenge. Employing 2‐methylimidazole‐hydrolyzed OH−, dopamine polymerization is initiated and then Zn2+ coordinates with 2‐methylimidazole on PDA surfaces. The confined symbiotic reaction yields 2D vertical heterojunctions of GO/ZIF‐8/PDA (G/Z/P). During separation, partially dehydrated smaller hydrated lanthanide ions preferentially access interlayers, expanding and stabilizing the interlayer space by coordinating with PDA, thus excluding larger hydrated scandium ions from the membranes. Some scandium ions entering interlayer channels are sequestered by N in size‐matched ZIF‐8 pores. This distinctive mechanism facilitates selective scandium separation from other REEs (other REEs/Sc selectivity ≈68.73), achieving nearly complete Sc3+ rejection in a single step. The methodology offers unprecedented insights into precise nano‐space material synthesis, indicating promising strides in advancing scandium production.

Protein-based approach for high-purity Sc, Y, and grouped lanthanide separation

Rare earth elements (REEs: Sc, Y, La- Lu) are irreplaceable components in many clean energy and consumer technologies. However, the extraction and subsequent separation of individual REEs from ore-based feedstocks remains a significant economic and environmental challenge. In this work, we investigated the intra-REE separation potential of lanmodulin (LanM), a natural protein from Methylorubrum extorquens that has emerged as a sustainable potential alternative to conventional solvent extraction-based separation. By determining the intra-REE selectivity of immobilized LanM and systematically testing pH-based and small chelator-based (i.e., citrate and malonate) desorption processes, we established the framework and methodology for achieving select individual and grouped REE separations from a mixed REE feedstock. We show that Sc forms the tightest complex with LanM among REEs but can be readily and selectively desorbed using malonate to generate high-purity Sc (>99 % purity, >99 % yield) in a single adsorption/desorption cycle. We further show that the intrinsic REE selectivity of LanM is sufficient to achieve heavy REE (HREE) separation from light and middle REEs (L-MREEs), yielding an yttrium-enriched product. This separation effect is further magnified by pairing LanM’s unique M−LREE preference with a HREE-preferring chelator in the desorption process, which enriches HREE and MREE fractions relative to low value, abundant La/Ce. Finally, by combining pH- and citrate-based desorption processes in a two-cycle separation scheme, we demonstrate the generation of fractions highly enriched in Y, Gd-Lu, Pr-Eu, and La-Ce. Collectively, these data support the application of a LanM-based approach for achieving impactful REE separations from mixed REE feedstocks.

Distinct Extraction Behaviors of La/Ce and Sc/Y in the Phosphoric Acidic Leachate of Bauxite Residues and Their Sequential Extraction with Di-(2-Ethylhexyl) Phosphoric Acid as Extractant

Bauxite residue is a hazardous solid waste produced in the alumina production process and has also become a significant rare earth resource. The extraction behaviors of La, Ce, Sc and Y solubilized in the phosphoric acidic leachate of bauxite residue were investigated in this study with di-(2-ethylhexyl) phosphoric acid as the extractant. With a relatively low concentration of 2% at an aqueous solution pH of 1.5, 90% Sc and 98% Y were extracted by di-(2-ethylhexyl) phosphoric acid. Less than 5% La and Ce and impurities of Fe, Al, Ti and Ca were extracted in this situation. As the concentration of di-(2-ethylhexyl) phosphoric acid increased to 20%, almost all the Sc and Y were extracted and the extraction ratios of La and Ce were 87% and 95%, respectively. A good separation of REEs against impurities was simultaneously obtained in the solvent extraction process and their separation coefficients were much higher than 1. A stepwise extraction process was proposed and established to extract Sc/Y and La/Ce sequentially from the phosphoric acidic leachate. It was further revealed that the Sc and Y in the acidic leachate were extracted by di-(2-ethylhexyl) phosphoric acid through an ion exchange process, and that the extraction of La and Ce was due to an antagonistic process where both an ion exchange reaction and a solvation reaction occurred.

HPLC separation of REE, U and Pu from uranium silicide fuel

ABSTRACT Experimental burn-up determination of spent nuclear fuel samples by mass spectrometry requires separation of major actinides and rare earth fission products. An HPLC method is developed for the separation of uranium, plutonium and REEs from the dissolved solution of spent U3Si2 fuel sample. The task was challenging due to the presence of aluminum and uranium in large proportions. The established ion interaction chromatography-based method was found unsuccessful to overcome the interference caused by aluminum matrix. Extraction chromatography using reversed phase stationary phase modified with HDEHP and TODGA was explored for the separation problem. Good separation among aluminum, REEs, U and plutonium was achieved using a column modified with TODGA. The optimized method exhibited good tolerance to large proportions of aluminum, uranium and nitrate salt present in the dissolved fuel solution.

REE ultra-rich karst bauxite deposits in the Pedernales Peninsula, Dominican Republic: Mineralogy of REE phosphates and carbonates

Karst bauxites have recently received renewed attention for their potential as non-conventional REE sources. Karst bauxites from the Pedernales Peninsula in the Dominican Republic stand among the world’s richest in REE. Bauxite ore from two deposits from this bauxite district, Aceitillar and El Turco, have been selected for this study due to their outstanding REE contents and contrasting mineralogy. REE (La to Lu) contents in Aceitillar, range from 0.07 to 0.16 wt%, and Y from 0.01 to 0.13 wt%, whereas El Turco contains between 0.28 and 1.40 wt% REE, and 0.33 to 1.48 wt% Y. The characterisation of REE mineralisation was performed through powder and monocrystal XRD, SEM-EDS, and EMP analyses. REE phosphates and carbonates reveal textural features that suggest significant REE mobilisation and re-deposition within the bauxite profile. The identified REE minerals can be classified into: i) primary monazite(-Ce) and minor monazite(-La); ii) secondary Y- and Nd-dominant phosphates; and iii) secondary Gd- and Nd-carbonates of the (hydroxyl)bastnäsite group. While monazites are ubiquitous in the two studied deposits, secondary phosphates are predominant in El Turco while secondary carbonates are exclusive of Aceitillar. This contrasting mineralogy is explained by the total concentration of carbonate and/or phosphate in the karst bauxite groundwater solutions. REE phosphates are the most stable phases at [CO32−]total/[PO43−]total ≤ 2; whereas REE carbonates are stable at near neutral pH when the total aqueous carbonate concentration is two orders of magnitude higher than that of phosphate. Results of this investigation contribute to a better understanding of the formation REE minerals in the supergene environment and can be applied in REE separation methods.

An efficient method for the separation of REEs from Ba for the accurate determination of REE content in Ba-rich samples by ICP-MS

A new efficient method for the separation of Ba from REEs for the accurate determination of REE content in Ba-rich samples by ICP-MS.

Separation of TPE and REE by Displacement Chelating Chromatography in the Presence of Iron, Chromium and Aluminum Impurities

Separation of TPE and REE by Displacement Chelating Chromatography in the Presence of Iron, Chromium and Aluminum Impurities

Preparation of pyrrolidinyl diglycolamide bonded silica particles and its rare earth separation properties

The separation of rare earth elements by solid phase containing diglycolamide-type ligands is a hot topic. In this study, 2-[2-oxo-2-(1-pyrrolidinyl)ethoxy]acetic acid (PYRDGA) was synthesized and attached to the silica. The binding strength of SiO2@PYRDGA for rare earths showed a single increasing trend with the radius of rare earth atoms. IR and XPS spectra demonstrated that carbonyl oxygen and ether bond oxygen are binding sites for rare earth ions. SiO2@PYRDGA was used for the chromatographic separation of REEs, and the primary separation of 16 REEs was achieved at pH = 2.0 using HNO3 solution as the eluent, and La, Ce, Pr, Nd, Sm, and Eu reached the baseline separation level.

Alkali treatment–acid leaching of rare earth elements from phosphogypsum fertilizer: insight for additional resource of valuable components

Phosphogypsum (PG) is the main by-product of phosphoric acid, which is produced by the sulfuric acid attack of phosphate rocks, wet process. This by-product, which contains around 2.0% phosphoric acid, is used as a low-cost soil fertilizer, PGF. PGF consists mainly of gypsum (CaSO4·2H2O), P2O5, SiO2, and other impurities, including a minor amount of rare earth elements, REEs. In general, phosphate rocks contain from about 0.04 to 1.0% REE, which are precipitated with PG. Now, REEs are considered as strategic elements. Therefore, PG is now regarded as a secondary source of REE. This paper address a process for the separation of REEs and sodium sulphate as a product from PGF. This paper is based on the metathesis of the bulk of PGF with sodium carbonate to obtain calcium carbonate precipitated contain REEs. Furthermore, sodium sulphate was obtained as a product. Calcium carbonate containing REEs was leached out by citric acid as a green acid or nitric acid. At optimum conditions, maximum leaching of REEs from CaCO3 after one cycle of leaching by 3.0 mol/L nitric acid at L/S = 3/1, agitation time of 180.0 min., and at a temperature of 25 °C is 75.1%, 361.10 mg/kg from the total REEs present in PGF. While, the maximum leaching of 87.4%, 420.2 mg/kg of REEs from CaCO3 after one cycle of leaching by 1.0 mol/L citric acid, L/S = 5/1, agitation time of 15.0 min., and 85 °C. The REEs that were obtained in the leaching citrate solutions were purified by solvent extraction using 10% of di-2-ethyl hexyl phosphoric acid, HDEHP, in kerosene. The extracted REEs were stripped by 0.5 mol/L H2SO4. The stripped solutions were further treated with 10.0% oxalic acid to precipitate the REEs. The developed procedure can recover REEs from PGF with an efficiency of 85.2% and a purity of 97.7%.

Tuning the sorption properties of amidoxime-functionalized algal/polyethyleneimine beads for La(III) and Dy(III) using EDTA: Impact of metal speciation on selective separation

Amidoximated algal/polyethyleneimine beads are successfully applied for the sorption of two rare earths elements (REEs, Ln(III)): La (light) and Dy (heavy). The sorption properties are characterized by FTIR and SEM-EDX analyses. The pH effect on metal sorption is investigated with a double objective: optimizing metal recovery and separation. In binary solutions, Dy(III) shows slightly higher affinity for the sorbent than La(III); without significant differences in the selectivity. The difficult separation of REEs can be modulated using EDTA. Playing with the pH and the concentration of the ligand, La(III) can be separated from Dy(III). Selectivity coefficient, SCLa/Dy, may reach up to 40–50. Speciation diagrams show that the preferential formation of Dy-EDTA complexes limits Dy(III) sorption while La(III) remains predominant and highly sorbed (reduced effect of Dy-competition). Optimum conditions for Ln(III) separation can be predicted by the calculation of speciation diagrams. The concept is verified for the separation of La(III) from Er(III) (heavy REE). In the presence of EDTA, sorption isotherms (mono-component solutions) present sigmoidal shapes due to the effect of metal complexation. Converting the total concentration to the concentration of sorbable species (non-complexed by EDTA) allows plotting favorable curves (Langmuir equation). The fits of experimental profiles with the modified Langmuir equation confirm the preference of the sorbent for non-complexed species. The kinetic profiles fitted by the Crank equation highlight the contribution of the resistance to intraparticle diffusion in the control of uptake kinetic; this effect is reinforced by the presence of EDTA. Metal desorption using CaCl2 (50 mM, pH 2) or EDTA (0.5 mM, pH 6) is used for La(III) and Dy(III) desorption (yield: 80–95%), while sorption capacity progressively decreases over 3 cycles.

Effect additional pH on separation extraction gadolinium from terbium and europium with Di-2-(ethylhexcyl)phosphate acid

Rare earth elements are strategic materials, difficult to obtain, and have wide uses. Currently, it is still difficult to separate and refine REE’s because it has similar physical and chemical properties. Solvent extraction is most successful method used for the separation of REE’s. Di-2-ethylhexyl phosphoric acid has been widely used in industry for the separation and of REE’s. Purpose of this study is effect of pH on basic parameters extraction which include distribution coefficient, extraction efficiency and separation factor in extraction gadolinium, terbium and europium through complex with D2EHPA. Determination effect pH is a parameter determined in process extracting standard solutions gadolinium, terbium and europium using D2EHPA with n hexane. Basic parameters in extraction gadolinium, terbium and europium with D2EHPA at pH 4 are as follows KdGd = 89.90; αGd/Tb = 5.63, Gd/Eu = 1.83; %E = 98.90. KdTb = 15.94; αTb/Gd = 0.17; Tb/Eu = 0.32; % E = 94.10; KdEu = 1.40; αEu/Gd = 0.01, Eu/Tb = 0.08; %E = 98.29. From these valuesit can be concluded that gadolinium, can be separated from terbium and europium by the solvent extraction method by forming complex D2EHPA with best separation results obtained at pH 4.

Pilot Plant for Studies of REE Separation by Extraction Chromatography Based on a Cascade of Centrifugal Extractors

Pilot Plant for Studies of REE Separation by Extraction Chromatography Based on a Cascade of Centrifugal Extractors

Separation of REE(III) and Am(III) by Extraction with Compounds of Zirconium and Dibutyl Phosphoric Acid from Solutions of Nitric and Hydrochloric Acids

Separation of REE(III) and Am(III) by Extraction with Compounds of Zirconium and Dibutyl Phosphoric Acid from Solutions of Nitric and Hydrochloric Acids

Long-chain ligand design in creating magnetic nano adsorbents for separation of REE from LTM

A series of magnetic adsorbents was created by grafting selected functional ligands directly on the surface of iron oxide nanoparticles (NP). The produced materials were characterized by SEM-EDS, TEM, AFM, FTIR, XRD, Mössbauer spectroscopy, low temperature gas sorption, and in relation to functional properties. Each of the applied ligands carried two functional groups including phosphonic acid involved in grafting, and either alcohol, thiol, amino, carboxylic- or phosphonic acid. The kinetics and thermodynamics of metal cation adsorption were investigated for Rare Earth (REE, Sm3+, Nd3+, Dy3+ and Tb3+) and Late Transition Metals (LTM, Co2+ and Ni2+) as representative for the content of magnetic materials, requiring recycling. Long linear alkyl chain (C10-C12) and, in case of phosphonic acid, even a shorter one (C6), were used to trace potential stabilization of the particles against iron leaching on desorption of adsorbed cations in acidic medium. The NP demonstrated high adsorption capacity, efficient desorption and considerable selectivity in separation of REE from LTM. Modification with ligands offers appreciable protection of magnetic particles against iron leaching.

Non-conventional recovery of uranium and associated valuable metals from Rosetta monazite mineral concentrate

ABSTRACT Citric acid has a very important role in the extraction process of uranium from the matrix such as hydrous oxide cake formed after alkali breakdown of Egyptian Rosetta monazite mineral concentrate. This manner involved leaching of uranium selectively (94%) using 150 g L−1 citric acid concentration at solid liquid (S/L) ratio of 1:5 at room temperature for 120 min. The kinetics of the concerning leaching process and the reaction mechanism between citric acid and uranium have been discussed in detail. From the latter, it was found that the reaction was diffusion controlled and the calculated apparent activation energy value was 12.724 KJ mole−1. The work then explained the separation of Th and REEs from hydrous oxide as conventional techniques in published data.

Separating Rare-Earth Elements on Centrifugal Extractors: Developing Technology, Designing Equipment, and Engineering Production

The results of studies on the extraction separation of REE concentrate isolated from phosphogypsum into 75 vol % TBP in a diluent are presented. The proposed technology has been tested in a pilot plant using an automated cascade of centrifugal extractors of the ETs-10FA model. The design of a centrifugal extractor made of high-molecular-weight polyethylene ETs-1000PB has been developed and its serial production has been mastered. An experimental production has been organized for the separation of REEs with the production of high-purity compounds of cerium, lanthanum, neodymium, and praseodymium on centrifugal extractors.

Separation of La(III), Eu(III), and Ho(III) with Sorbents Impregnated by Mixtures of Acidic Phosphoryl Podands and Amines in Nitric Acid Solutions

ABSTRACTThe possibility of separation of La(III), Eu(III), and Ho(III) as respective individual representatives of light, medium, and heavy rare earth elements was studied using sorbents impregnated by mixtures of acidic phosphoryl podands derived from diethylene glycol and octyl, dioctyl, and trioctyl amines from nitric acid solutions of various concentrations. The influence of the phosphoryl podands structure, their percentage content, and proportion in a sorbent and the nature of an acid on the efficiency of separation of La(III), Eu(III), Ho(III) was studied. It is shown that the greater is the concentration of HNO3, the smaller are the separation factors of REEs, and remarkably so. The most efficient separation is achieved with the concentration of HNO3 not over 0.04 mol/L. The optimal conditions of separation of La(III), Eu(III), and Ho(III) with the developed sorbent were found. Repeated use of the sorbent for the separation of La(III), Eu(III), and Ho(III) after its regeneration with 0.04 mol/L HNO3 was estimated. It was found that the efficiency of separation of REEs with the sorbents impregnated by a mixture of 1,5-bis(2-oxyethoxyphosphoryl-4-ethylphenoxy)-3-oxapentane and trioctylamine (TOA) exceeds markedly that made of a mixture of di-(2-ethylhexyl)phosphoric acid (DEHPA) and TOA.

Effect of super gravity on successive precipitation and separation behaviors of rare earths in multi-components rare-earth system

Re-concentrate is a complex multi-components Re-system consisting of Ce, La, Pr and Nd, which brings great difficulties for investigating the transformation and separation behaviors of REEs. The effect of super-gravity field on the mass transfer and phase separation behaviors of REEs was investigated in this paper, and the phenomenon of successive precipitation and separation of REEs was discovered. The Re3+ was firstly precipitated into Re-oxyfluoride phase with OF3-, which overcame the interface tension to be evidently separated into the bottom layer under the action of super gravity. Subsequently, the Re3+ were successively precipitated with FeO33-, SiO44- and PO43- into Re-ferrate phase and britholite phase, which were separated further into the middle and top layers along the super gravity direction. Moreover, various REEs were efficiently recovered into the different Re-phases, respectively. The theoretical and experimental results verified the significant enhancement of super gravity on the mass transfer and phase separation of REEs, and its efficient application in REEs recovery from multi-component Re-system.