Separation of rare earth and Al with high-value Al transformation from fluorite-kaolin associated ion-adsorption type ore

The extraction and separation of rare earths (REs) from nitrate medium or chloride medium using bifunctional ionic liquid extractants (Bif-ILEs) [trialkylmethylammonium][di(2-ethylhexyl)orthophosphinate] ([A336][P507]) and [trialkylmethylammonium][di-2-ethylhexylphosphate] ([A336][P204]) in n-heptane were investigated in this report. The separation factor (β) values indicated that [A336][P507] and [A336][P204] could be suitable for the separation of heavy REs(III) in nitrate medium and suitable for the separation of light REs(III) in chloride medium. Especially, in nitrate medium, the β values using [A336][P204] as the extractant were Tm/Er (3.36), Yb/Tm (7.92), and Lu/Yb (8.55), respectively, and in chloride medium, the β values using [A336][P507] as the extractant were Nd/Pr (9.52) and Sm/Nd (4.70), respectively. The β̅z+1/z values of REs(III) extracted by [A336][P507] and [A336][P204] in nitrate medium were 3.61 and 3.67, respectively, and in chloride medium, they were 2.75 and 2.59, respectively.

Development and optimization of high-performance extraction chromatography method for separation of rare earth elements

Study on separation of heavy rare earth elements by solvent extraction with organophosphorus acids and amine reagents

In the search for more efficient purification and separation methods for rare earths, remarkable results were obtained in the field of solvometallurgy. Replacing the aqueous phase partially or largely by polar molecular organic solvents can significantly improve extraction efficiency and selectivity in the separation of rare earths and transition metals. The effect of polar organic solvents on the sorption of rare-earth elements and transition metals was investigated for strong anion exchanger Amberlite IRA 402 (Cl−), and for extraction chromatography resins, TEVA (Cl−) and DGA. The sorption of metal ions was tested from ethanol, ethylene glycol, water and formamide. While Amberlite IRA 402 selectively recovered the iron, copper and cobalt, while leaving the rare-earth elements in solution, the DGA resin was selective for rare-earth elements and could be used for the separation of heavy rare earths from light rare earths. The efficiency of metal uptake by the resins increased with decreasing dielectric constant of the feed solvent. These results were compared to non-aqueous solvent extraction using Aliquat 336 and TODGA from the different polar organic solvents. Significant mutual miscibility observed during these solvent extraction tests demonstrated the advantage of using ion-exchange resins over solvent extraction. However, in the case of chromatographic resins, the functional molecules are only physically bonded by the resin, and loss of sorption capacity due to extractant loss was observed with both TEVA and DGA resin, especially in combination with ethanolic solutions.

Solvent extraction technology for the separation of rare earths is a recent one. This is mainly due to the low separation factors between the adjacent rare earths for any type of extractants that have been investigated so far. In spite of this inherent weakness arising due to the gradual small changes in basicity in the series of rare earths few extractants have been used on commercial scale for the separation of high purity rare earths. In this paper the mechanisms involved in the extraction of rare earths using different types of extractants like tributylphosphate, di (2-ethylhexyl) phosphoric acid, 2-ethylhexyl 2-ethylhexyl phosphonic acid and quaternary ammonium salts have been discussed. The development of suitable mathematical models of the extraction behaviour of rare earths, particularly for the liquid cation exchangers, and their suitability for the development of the processes for the separation of rare earths is highlighted. Various process parameters that have been optimised using the computer programs developed by incorporating the mathematical models have been used in the purification of rare earths. The flow sheets designed for the separation of various rare earths are also given.

Extraction and separation of rare-earth elements by tri-n-octylmethylammonium nitrate (TOMAN) and β-diketone (α-acetyl-m-dodecylacetophenone: LIX54) in the presence of water-soluble complexing agent (ethylenediaminetetraacetic acid: EDTA) was investigated. All EDTA make 1:1 complex with rare earth, and only free (not complexed) rare-earth ions can take part in the extraction. Although the distribution ratio of the metals decreases by addition of EDTA, the separation factor increases since extractability of the heavier rare earth is further reduced by formation of inactive EDTA complex. The effect of EDTA on the separation factor can be predicted using the distribution ratio of each element in the absence of EDTA, the ratio of stability constants of the complexes and the feed concentration of the species. Separation and recovery of rare-earth elements from the aqueous raffinate solution was feasible by extraction of metals using tri-n-butylphosphate (TBP) in acidic conditions. Simulation of Nd/Pr separation by continuous counter-current batteries showed that Pr was highly purified by addition of EDTA in aqueous phase.

Synergistic extraction and separation of rare earths from chloride medium by the mixture of HEHAPP and D2EHPA

Sodium triphosphate has been used probably for the first time for the ion‐exchange separation of rare earths. A complexing elution on a cation exchanger with sodium triphosphate has given a more satisfactory separation of the light rare earths than the elution of their triphosphato complexes on an anion exchanger with dilute mineral acids. Equilibration studies with Amberlite IRA‐400 resin indicate that the rare earths form anionic complexes with sodium triphosphate over a wide range of pH.

This project developed a hydrometallurgical-based technology to extract and concentrate rare earth elements (REEs) from a representative group of coal combustion residuals (CCRs) from major coal sources in the United States. The approach for REE recovery comprises two general components: (1) Leaching of REEs from CCRs and (2) Separation of REEs from other major ions in the CCR leachate. The leaching step entails acid leaching with nitric or hydrochloric acid, and in some cases, pretreatment of CCRs with alkaline roasting prior to acid leaching. The follow-up REE recovery steps involve a series of membrane-based methods to separate and concentrate rare earth ions from other major ions in acid leachates of CCRs. These methods include liquid emulsion membranes, supported liquid membranes and electrodeposition with carbon nanotube electrochemical filters. The advantage of these separation approaches (relative to conventional approaches such as solvent extraction) is a reduction in the usage of solvents and other costly chemicals and a reduction of hazardous waste products that are challenges in conventional REE separation methods. In the testing of our process, we selected a representative set of CCR samples from our collection and performed a suite of characterization measurements (total REE content and major mineralogy). The major results of this work demonstrated that heated acid leaching could efficiently extract REEs from PRB-based coal fly ashes while the Appalachian and Illinois Basin CCRs required alkaline roasting with NaOH prior to acid leaching at room temperature. The supported liquid membrane (SLM) configuration and electrochemical deposition (ED) system yielded the most promising methods of REE recovery from the acid leachates of fly ash. Our most concentrated product to date comprised 1 wt.% (dry basis) REEs produced from an Appalachian-based fly ash leached and purified by SLM. The SLM separation process was more selective for heavy REEs over the light REEs. When SLM was combined with ED, preliminary results demonstrated that a final product of >2 wt.% REEs was possible.

This project developed a hydrometallurgical-based technology to extract and concentrate rare earth elements (REEs) from a representative group of coal combustion residuals (CCRs) from major coal sources in the United States. The approach for REE recovery comprises two general components: (1) Leaching of REEs from CCRs and (2) Separation of REEs from other major ions in the CCR leachate. The leaching step entails acid leaching with nitric or hydrochloric acid, and in some cases, pretreatment of CCRs with alkaline roasting prior to acid leaching. The follow-up REE recovery steps involve a series of membrane-based methods to separate and concentrate rare earth ions from other major ions in acid leachates of CCRs. These methods include liquid emulsion membranes, supported liquid membranes and electrodeposition with carbon nanotube electrochemical filters. The advantage of these separation approaches (relative to conventional approaches such as solvent extraction) is a reduction in the usage of solvents and other costly chemicals and a reduction of hazardous waste products that are challenges in conventional REE separation methods. In the testing of our process, we selected a representative set of CCR samples from our collection and performed a suite of characterization measurements (total REE content and major mineralogy). The major results of this work demonstrated that heated acid leaching could efficiently extract REEs from PRB-based coal fly ashes while the Appalachian and Illinois Basin CCRs required alkaline roasting with NaOH prior to acid leaching at room temperature. The supported liquid membrane (SLM) configuration and electrochemical deposition (ED) system yielded the most promising methods of REE recovery from the acid leachates of fly ash. Our most concentrated product to date comprised 1 wt.% (dry basis) REEs produced from an Appalachian-based fly ash leached and purified by SLM. The SLM separation process was more selective for heavy REEs over the light REEs. When SLM was combined with ED, preliminary results demonstrated that a final product of >2 wt.% REEs was possible.

The extraction and subsequent separation of individual rare earth elements (REEs) from REE-bearing feedstocks represent a challenging yet essential task for the growth and sustainability of renewable energy technologies. As an important step toward overcoming the technical and environmental limitations of current REE processing methods, we demonstrate a biobased, all-aqueous REE extraction and separation scheme using the REE-selective lanmodulin protein. Lanmodulin was conjugated onto porous support materials using thiol-maleimide chemistry to enable tandem REE purification and separation under flow-through conditions. Immobilized lanmodulin maintains the attractive properties of the soluble protein, including remarkable REE selectivity, the ability to bind REEs at low pH, and high stability over numerous low-pH adsorption/desorption cycles. We further demonstrate the ability of immobilized lanmodulin to achieve high-purity separation of the clean-energy-critical REE pair Nd/Dy and to transform a low-grade leachate (0.043 mol % REEs) into separate heavy and light REE fractions (88 mol % purity of total REEs) in a single column run while using ∼90% of the column capacity. This ability to achieve, for the first time, tandem extraction and grouped separation of REEs from very complex aqueous feedstock solutions without requiring organic solvents establishes this lanmodulin-based approach as an important advance for sustainable hydrometallurgy.

Rare earth elements (REE) are essential ingredients of sustainable energy technologies, but separation of individual REE is one of the hardest problems in chemistry today. Biosorption, where molecules adsorb to the surface of biological materials, offers a sustainable alternative to environmentally harmful solvent extractions currently used for separation of rare earth elements (REE). The REE-biosorption capability of some microorganisms allows for REE separations that, under specialized conditions, are already competitive with solvent extractions, suggesting that genetic engineering could allow it to leapfrog existing technologies. To identify targets for genomic improvement we screened 3,373 mutants from the whole genome knockout collection of the known REE-biosorbing microorganism Shewanella oneidensis MR-1. We found 130 genes that increased biosorption of the middle REE europium, and 112 that reduced it. We verified biosorption changes from the screen for a mixed solution of three REE (La, Eu, Yb) using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) in solution conditions with a range of ionic strengths and REE concentrations. We identified 18 gene ontologies and 13 gene operons that make up key systems that affect biosorption. We found, among other things, that disruptions of a key regulatory component of the arc system (hptA), which regulates cellular response to anoxic environments and polysaccharide biosynthesis related genes (wbpQ, wbnJ, SO_3183) consistently increase biosorption across all our solution conditions. Our largest total biosorption change comes from our SO_4685, a capsular polysaccharide (CPS) synthesis gene, disruption of which results in an up to 79% increase in biosorption; and nusA, a transcriptional termination/anti-termination protein, disruption of which results in an up to 35% decrease in biosorption. Knockouts of glnA, pyrD, and SO_3183 produce small but significant increases (≈ 1%) in relative biosorption affinity for ytterbium over lanthanum in multiple solution conditions tested, while many other genes we explored have more complex binding affinity changes. Modeling suggests that while these changes to lanthanide biosorption selectivity are small, they could already reduce the length of repeated enrichment process by up to 27%. This broad exploratory study begins to elucidate how genetics affect REE-biosorption by S. oneidensis, suggests new areas of investigation for better mechanistic understanding of the membrane chemistry involved in REE binding, and offer potential targets for improving biosorption and separation of REE by genetic engineering.

Rare earth elements (REE) are highly requested by modern industry, being indispensable for construction of electric vehicles and environmentally friendly energy sources. Challenge in their production lies in their joint occurrence and similar chemical properties. It can be answered by using solid phase extraction, applying highly selective nanostructured adsorbents. The latter are bearing organic ligands with high specific affinity to particular REE grafted on their surface via covalent bonding. This work is a comparative study to demonstrate the ligand properties in relation to distinct REE as a function of various operating conditions, such as concentration of solutions and pH. Mechanisms of adsorption are elucidated with a variety of techniques including FTIR (Fourier-transform infrared spectroscopy), solid-state NMR spectroscopy (Nuclear Magnetic Resonance), and EXAFS spectroscopy (extended X-ray absorption fine structure) in combination with analysis of particles bearing adsorbed cations by SEM-EDS (scanning electron microscopy/energy dispersive X-ray spectroscopy) and of solutions by complexometric titration. Recommendations are elaborated for specific choice of ligands and adsorption–desorption conditions for improved separation of single REE. The results are verified in separation of REE from complex leachates both by magnetic nanoadsorbents and by mesoporous microparticles applied as a sorbent in High Performance Chelation Ion Chromatography (HPCIC).

Recent advances in selective separation technologies of rare earth elements: a review

A combined procedure for separating Lu, Hf, Sm, Nd, and rare earth elements (REEs) from a single sample digest is presented. The procedure consists of the following five steps: (1) sample dissolution via sodium peroxide sintering; (2) separation of the high field strength elements from the REEs and other matrix elements by a HF-free anion-exchange column procedure; (3) purification of Hf on a cation-exchange resin; (4) separation of REEs from other matrix elements by cation exchange; (5) Lu, Sm, and Nd separation from the other REEs by reversed-phase ion chromatography. Analytical reproducibilities of Sm-Nd and Lu-Hf isotope systematics are demonstrated for standard solutions and international rock reference materials. Results show overall good reproducibilities for Sm-Nd systematics independent of the rock type analyzed. For the Lu-Hf systematics, the reproducibility of the parent/daughter ratio is much better for JB-1 (basalt) than for two analyzed felsic crustal rocks (DR-N and an Archaean granitoid). It is demonstrated that this poorer reproducibility of the Lu/Hf ratio is truly caused by sample heterogeneity; thus, results are geologically reasonable.