REE Recovery Research Articles

Recycling of Rare Earth Elements from Nickel Metal Hydride Battery Utilizing Supercritical Fluid Extraction

Nickel Metal Hydride (NiMH) batteries are widely used in hybrid vehicles. The anode of this battery consists a mischmetal alloy of lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd) [1]. These four elements are part of rare earth elements group, and among them, praseodymium and neodymium are considered critical materials, since they are in increasing high demand and facing supply uncertainty and near zero recycling. On the basis of the historic data, the annual demand for REEs has been increasing at a rate of 8.6% annually [1,4], and it is predicted that the rate could increase to above 20% annually to accommodate the increased utilization of renewable power generation (in particular wind and solar) and electrified transportation in the society [5]. To address the sustainability hurdles associated with NiMH battery and REE supply, new strategies have been initiated to mine these elements from secondary sources. Waste electrical and electronic equipment (WEEE) including NiMH batteries contain considerable amounts of REEs, which make them an attractive source.The number of NiMH batteries manufactured up to this date is significant, and the global annual production is also increasing, as Toyota plans to increase the sale of Prius hybrid model by 2020 [2]. Although REEs account for more than 30 wt% of a NiMH battery, the global recycling rates of REEs from end of life NiMH batteries is less than 1% [1,3]. Considering the great opportunity, it is essential to develop efficient processes for the recovery of REEs from this class of WEEE.Current recycling practices rely on either pyrometallurgy or hydrometallurgy. The former in highly energy intensive and the latter relies on large volumes of acids and organic solvents, generating large volumes of hazardous residues. This study is focused on developing an innovative and sustainable process for the urban mining of REEs from NiMH battery. The developed process relies on supercritical fluid extraction (SCFE) utilizing carbon dioxide as the solvent, which is inert, safe, and abundant. This process is very efficient because it runs at low temperature, and does not produce hazardous waste, while recovering about 90% of REEs. Furthermore, we proposed a mechanism for the SCFE of REEs, where we considered a trivalent REE state bonded with three Tri-n-butyl phosphate (TBP) molecules and three nitrates model for the extracted rare earth TBP complex. The SCFE process is an efficient and environmentally friendly process to valorize postconsumer NiMH battery without utilizing hazardous reagents; therefore, it minimizes the negative impacts of process tailings. This novel process proves to be a promising technique that can help realize the technological potential of REE recovery from post consumer WEEE, particularly NiMH battery

Extraction of Rare-Earth Elements from Hydrochloric Acid by Carbamoyl Methyl Phosphine Oxides in the Presence of Ionic Liquids

The distribution of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y between aqueous HCl solutions and solutions of carbamoyl methyl phosphine oxides (CMPOs) has been studied in the presence of the 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ionic liquid (IL). The efficiency and selectivity of REE(III) extraction by CMPO solutions increase considerably in the presence of the ionic liquid in the organic phase. The stoichiometry of the extractable complexes has been determined; the effects of the IL cation, organic solvent, CMPO structure, and aqueous HCl concentration on the efficiency of REE(III) recovery into the organic phase has been considered.

Selective electrochemical extraction of REEs from NdFeB magnet waste at room temperature

A closed loop room temperature electrochemical process for selective recovery of REEs from NdFeB magnet waste.

Nature of influence exerted by Na2SiF6 on REE recovery from orthophosphoric acid solution in the course of CaSO4·0.5H2O crystallization

Chemical and X-ray phase analyses were used to study the influence exerted by Na2SiF6 on the isomorphic inclusion of cerium into the structure of CaSO4∙0.5H2O precipitates formed from solutions of phosphoric acid hemihydrate (38 wt % P2O5). The poorly soluble suspensions of CaSO4∙0.5H2O precipitates can serve as adsorbents for cerium compounds, with CaSO4∙0.5H2O–NaCe(SO4)2∙H2O and CaSO4∙0.5H2O–CePO4∙0.5H2O solid solutions formed. The introduction of Na2SiF6 makes the sorption properties CaSO4∙0.5H2O several times better because the Na2SiF6 phase is a source of sodium cations and creates the necessary Na: Ce ratio of 1: 1 for extracting cerium from the liquid phase into a precipitate in the form of a CaSO4∙0.5H2O–[NaCe(SO4)2∙H2O + CePO4∙0.5H2O] solid solution. Under the industrial conditions in which extraction phosphoric acid is manufactured, a similar isomorphous capture of rare-earth elements of the cerium group (La–Sm) may occur in joint precipitation of CaSO4∙0.5H2O and Na2SiF6.

Recovery of rare earth elements with ionic liquids

This review focuses on the recovery of REEs from waste with ionic liquids (ILs) as dilutants and extractants to tackle the REE supply challenge.

Recovery of rare earth elements from spent fluid catalytic cracking catalysts using leaching and solvent extraction techniques

This paper investigates the recovery of rare earth elements (REEs, mainly lanthanum and cerium) from spent fluid catalytic cracking (FCC) catalysts via the hydrometallurgical processes of leaching and liquid-to-liquid extraction. The maximum leaching efficiency (99.3% for REEs) was achieved under the following conditions: 2mol/L HCl, a solid-to-liquid (S/L) ratio of 1:10, leaching at 60°C for 2h, and 2h of roasting at 750°C prior to leaching. Because the main impurity element in the leachate was aluminum, the extractions of REEs and aluminum using di-2-ethylhexyl phosphoric acid (D2EHPA) and 2-ethylhexylphosphonic mono-2-ethylhexyl ester (HEHEHP) under different conditions were compared. The results indicated that D2EHPA and HEHEHP exhibited large extraction differences for REEs but small extraction capacity differences for aluminum. Based on the analysis of the experiments, the optimum extraction conditions for REEs were determined to be 0.5mol/L D2EHPA, equilibrium pH=2.5, ambient temperature and then stripping with 2mol/L HCl. The overall REEs recovery efficiency was 62.88%.

Acid retardation method in analysis of strongly acidic solutions by inductively coupled plasma mass-spectrometry

Acid retardation on the sorbents as a technique for reduction of the acidity of the solutions prior to their analysis by inductively coupled plasma mass spectrometry was proposed and investigated. The proposed scheme provides substantial separation of the analytes and nitric acid, which allows direct introduction of the eluates in plasma without dilution. Two sorbents were examined – AV-17 anion-exchange resin and the Stirosorb 584 sorbent. Sorption and desorption of 38 elements on these sorbents were investigated. The efficiencies of the REEs' sorption on the anion-exchange and neutral sorbents were compared. The higher efficiency of the REEs and HNO3 separation was revealed for the neutral Stirosorb 584 sorbent. It was also found that most elements come out quantitatively of the column filled with the AV-17 resin after pumping 2–4mL of the solution. Wherein, the concentration of nitric acid decreased by 20 times. The anomalous behaviour of Ag, Pb, Th and U on the AV-17 resin was found. These analytes were eluted only after pumping 4 column volumes of deionized water. Na, K, Fe, Al and Li in concentrations within (50–1000mgL−1) range did not affect the recovery of REEs. The potential of ARM technique was demonstrate by the analysis of puriss. HNO3 and silverware. ARM enables to avoid dilution of highly acidic solutions prior to their introduction in ICP-MS.

Extraction of Ce (IV), Yb (III) and Y(III) and recovery of some rare earth elements from Egyptian monazite using CYANEX 923 in kerosene

Separation and recovery of some rare earth elements, including cerium (Ce (IV)), ytterbium (Yb(III)) and yttrium (Y(III)) from nitric acid solution using CYANEX 923 in kerosene at 25°C was studied. The parameters which influence the extraction process were separately investigated. On the basis of the slope analysis method on the obtained data, the composition of the extracted species was found to be [Ce (NO3)3(OH)·2CY], [Yb (NO3)2(OH)·2CY·H2O], and [Y (NO3)2(OH)·2CY·H2O], for Ce (IV), Yb (III) and Y (III), respectively, where CY denotes CYANEX 923. The structures of the extracted metal species showed by FT-IR investigations indicated the presence of OH– and NO3− groups. Moreover, the thermodynamic parameters associated with the extraction process were evaluated. Based on the obtained results, as well as those obtained in a previous publication for the extraction of Pr (III), Sm (III) and Nd (III) with CYANEX 923 under similar conditions, a process for the recovery of REE from the Egyptian monazite was proposed and evaluated.

Extraction of rare earths and scandium by 2-phosphorylphenoxyacetic acid amides in the presence of ionic liquids

The distribution of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc between aqueous solutions of their salts and solutions of 2-phosphorylphenoxy acid amides in dichloroethane containing an ionic liquid (1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide) have been studied. Metal ion extraction has been found to increase considerably in the presence of this ionic liquid in the organic phase. The stoichiometries of extractable complexes have been determined. The influence of aqueous HNO3 concentration and of the nature of extractant and ionic liquid on the efficiency of REE(III) and scandium(III) recovery to the organic phase has been considered.

Selective recovery of heavy rare earth elements from apatite with an adsorbent bearing immobilized tridentate amido ligands

Abstract Apatite, which is used in the production of phosphorus fertilizers, contains small amounts of rare earth elements (REEs; 0.1–1%). Apatite deposits occur all over the world and thus have the potential to be a secure source of REEs. We investigated a method for recovery of REEs from an apatite sample; specifically, REEs were leached from the sample with an H2SO4 solution, the acid that is most commonly used for fertilizer production. At high H2SO4 concentrations, most of the REEs in the solution were lost to precipitation as insoluble gypsum (CaSO4·2H2O). However, at H2SO4 concentrations of

The rare earth elements in municipal solid waste incinerators ash and promising tools for their prospecting

Bottom and fly ashes from Municipal Solid Waste Incinerators (MSWI) are hazardous products that present concern for their safe management. An attractive option to reduce their impact both on the environment and the financial commitment is turning MSWI ashes into secondary raw materials. In this study we present the REE content and distribution of bottom and fly ashes from MSWI after a highly effective digestion method and samples analysis by ICP–MS. The chondrite-normalised REE patterns of MSWI bottom and fly ash are comparable with that of crustal averages, suggesting a main geogenic source. Deviations from typical crustal pattern (e.g., Eu, Tb) disclose a contribution of likely anthropogenic provenance. The correlation with major elements indicates possible sources for REE and facilitates a preliminary resource assessment. Moreover, magnetic susceptibility measurements can be a useful prospecting method in urban ores made of MSWI ashes. The relationship between REE and some influencing parameters (e.g., Pricing Influence Factor) emphasises the importance of MSWI ash as alternative source of REE and the need of further efforts for REE recovery and purification from low concentrations but high flows waste.

Recovery of yttrium and lanthanides from sulfate solutions with high concentration of iron and low rare earth content

To overcome the low recovery, generally obtained for the heavy and middle rare earth elements (HREE and MREE) by sodium double sulfate precipitation, the recovery of the MREE and HREE as phosphate salts was investigated. High recovery yields (≥ 95%) were obtained even for sulfate solutions containing low concentrations of REE and a high concentration of iron(II). The influence of many industry-relevant parameters (temperature, pH, stoichiometric excess of phosphate, aluminum contamination, residence time) is discussed in order to optimize the REE recovery and to minimize the precipitation of iron. The developed process was also validated in continuous operation at a pilot scale. Finally, the REE phosphate concentrate could be converted into REE hydroxides which allows its dissolution into diluted HCl. Taking into account the phosphate precipitation, the conversion into hydroxides and the dissolution in HCl(aq), high recovery yields were obtained for Y, Gd and La (68%, 77% and 86% respectively). The results show that it is possible to economically obtain purified REE solutions starting from industrial solutions which are usually discarded.

Supercritical Fluid Dissolution and Extraction of Trivalent Metal Cations from Different Matrices

Studies on the recovery of trivalent metal ions such as Nd3+Eu3+ (taken as homologs of Am(III)) from solid oxide (Nd2O3), Thorium concentrate (obtained from Monazite ore processing), tissue paper/surgical gloves (rubber), and plant samples have been carried out by supercritical fluid extraction (SFE) using supercritical CO2 and ethanol/nitric acid. N,N,N’,N’-tetraoctyl diglycolamide (TODGA) was used as the extractant in these studies. The results showed that the recovery of Nd increased with TODGA concentration from 50% (no TODGA) to 70% (10% TODGA) at 3 M HNO3 in ethanol. However, the extraction of Nd at 1 M HNO3 was invariant with 1-3% (v/v) TODGA concentration (73 ± 4%). Interestingly, REEs recovery from Th concentrate was ˜ 60% even without TODGA using ethanol/3 M HNO3 mixture. On the other hand, quantitative recovery of 152,154Eu from tissue paper and surgical gloves sample could be achieved using 3 M HNO3/ethanol mixture. This suggested that it would be possible to decontaminate the contaminated laboratory waste papers using SFE technique.

Partitioning of REE(III) and TPE(III) with an extractant based on chlorinated cobalt dicarbollide and polyethylene glycol

Theoretical principles and practical characteristics are reported for an extraction process for REE and TPE partitioning using an extractant based on chlorinated cobalt dicarbollide (CCD) and polyethylene glycol (PEG). Joint extraction of REE and TPE is performed from a ≤1 M HNO3 solution with a solution of CCD and PEG in a polar diluent. The TPE stripping is performed with an aqueous solution of a complexing agent (diethylenetriaminepentaacetic acid) and an organic base (urea or thiourea). Trials on an extraction rig in Gatchina showed that the process can be successfully used for exhaustive recovery of REE and TPE from real Purex process raffinates and for their subsequent partitioning, with reaching the required process parameters. The results of semicommercial trials of the REE/TPE partitioning process on the extraction installation of the Mayak Production Association are reported. The trials were performed on such scale for the first time in the world. In reprocessing of 40 m3 of high-level raffinates, good results were obtained with respect to the process hydrodynamics, REE/TPE partitioning, and their separation from impurity elements. The process has high potential for use in HLW reprocessing technologies at new radiochemical plants.

Hydrotalcite formation facilitates effective contaminant and radionuclide removal from acidic uranium mine barren lixiviant

An assessment of hydrotalcite (HT) formation as a method to neutralise acidity and remove trace elements was undertaken using barren lixiviant from Heathgate Resources’ Beverley North in situ recovery (ISR) U mine in South Australia. This study demonstrated proof of concept in terms of the neutralisation of acidity and concomitant removal of a range of trace elements and U–Th series radionuclides from the barren lixiviant using MgCl2 as a supplementary Mg source to optimise Mg:Al mol ratios and NaOH as the neutralising agent. Hydrotalcite was the predominant mineral formed during neutralisation, hosting a range of elements including substantial U (∼0.2%) and rare earth elements (REE ∼0.1%). High U and REE recovery (∼99%) from barren lixiviant after HT precipitation indicates a potential to both remediate barren lixiviant and to offset remediation costs. Alternatively, HT precipitates formed during barren lixiviant neutralisation may be further stabilised via calcination, silicification or a combination thereof forming minerals potentially amenable for inclusion in a long-term waste repository at the cessation of ISR mining. Importantly, the composition of the neutralised barren lixiviant produced via HT precipitation is similar to that of existing groundwater allowing for the possibility of direct aquifer re-injection after remediation. A potential exists to apply this HT-based remediation technology to conventional or ISR U mines (or mines exploiting other commodities) and allows for the prospect of a fully integrated ISR mining, processing and lixiviant remediation strategy consistent with stringent environmental and mine closure standards.

Extraction of REEs(III), U(VI), and Th(IV) with acidic phosphoryl-containing podands from nitric acid solutions

The extraction of microamounts of REEs(III), U(VI), and Th(IV) from HNO3 solutions with solutions of acidic phosphoryl-containing podands in 1,2-dichloroethane was studied. The stoichiometry of the extractable complexes was determined. The influence of the extractant structure and aqueous phase composition on the efficiency and selectivity of the recovery of REEs(III), U(VI), and Th(IV) into the organic phase was considered.

Extraction of rare earth elements(III) from HNO3 and HCl solutions with mixtures of carbamoylmethylphosphine oxides and picrolonic acid

Extraction of REE(III) microamounts from HNO3 and HCl solutions with mixtures of mono- and bis-carbamoylmethylphosphine oxides with picrolonic acid in 1,2-dichloroethane was studied. The strong synergistic effect observed is due to increased hydrophobicity of the extractable complexes. The influence of the structure of carbamoylmethylphosphine oxides on the REE(III) extraction efficiency was considered, and the stoichiometry of the extractable complexes was determined. The possibility of REE(III) recovery and preconcentration from nitric acid solutions with a complexing sorbent prepared by noncovalent immobilization of the reagent mixture on the surface of a macroporous polymeric sorbent was demonstrated.

Solid phase separation and ICP-OES/ICP-MS determination of rare earth impurities in nuclear grade uranium oxide

A simple, effective and low cost solid phase extraction procedure was standardized for the trace and ultra-trace level determination of rare earth impurities, such as, Ce, Dy, Sm, Gd, Eu, Er etc. which act as neutron poisons, in nuclear grade uranium oxide (U3O8 > 99.9% by weight). The method involves selective separation of these elements as their fluorides with the help of activated charcoal from major uranium matrix followed by determination by ICP-MS and high resolution ICP-OES. The residual uranium content of the solution was <10 μg/mL. The recovery of REEs ranges from 85 to 105%. The method was validated with nuclear grade uranium oxide standards CRM-I to CRM-V (BARC, Mumbai, India) in addition to some synthetic standards. The RSD of the method was ±12% (n = 3).

Extraction of U(VI), Th(IV), and REE(III) from nitric acid solutions with (N,N-dialkylcarbamoylmethyl)- and (N-alkylcarbamoylmethyl)phenylphosphinic acids

Extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO3 solutions with solutions of (N,N-dialkylcarbamoylmethyl)- and (N-alkylcarbamoylmethyl)phenylphosphinic acids in dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the influence exerted on the efficiency of the U(VI), Th(IV), and REE(III) recovery into the organic phase by the extractant structure, organic diluent, and aqueous phase composition was examined. The possibility of selective recovery and concentration of U(VI), Th(IV), and REE(III) from nitric acid solutions with a complexing sorbent prepared by noncovalent immobilization of the examined polyfunctional organophosphorus acids on a macroporous polymeric matrix was demonstrated.

Extraction of rare-earth elements from nitric acid solutions with bidentate neutral organophosphorus compounds in the presence of l-butyl-3-methylimidazolium hexafluorophosphate

The distribution of microamounts of La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y nitrates between aqueous HNO3 solutions and solutions of tetraphenylmethylenediphosphine dioxide, diphenyl(diethylcarbamoylmethyl)phosphine oxide, and dibutyl(diethylcarbamoylmethyl)phosphine oxide in organic solvents in the presence of l-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6) was studied. The stoichiometry of the extractable complexes was determined. The influence of the HNO3 concentration and the nature of the extractant and organic solvent on the synergistic effect observed in the REE extraction in the presence of BMImPF6 in the organic phase was analyzed. The possibility of using a macroporous polymeric sorbent impregnated with a mixture of tetraphenylmethylenediphosphine dioxide and BMImPF6 for the recovery of REE(III), U(VI), and Th(IV) from HNO3 solution was demonstrated.