Extraction Of Lanthanides Research Articles

Efficient enrichment and selective recovery of rare earths from sulfate leachate of ion-adsorption type rare earth ore by extraction with HPOAc

The efficient enrichment and separation of rare earth elements (REEs) from sulfate leachates of ion-adsorption type rare earth ore (IATREO) is still a challenge. This work presents a novel extractant 2-(bis((2-ethylhexyl)oxy)phosphoryl)-2-hydroxyacetic acid (HPOAc) for the selective extraction and efficient enrichment of REEs from sulfate leachates of IATREO. HPOAc exhibits higher extraction ability for all fifteen REEs(III) than naphthenic acid (NA) at pHini = 1.56. Furthermore, it has no drawbacks of di-(2-ethylhexyl) phosphoric acid (P204) and 2-ethylhexyl phosphoric acid mono-2-ethylhexylester (P507) such as weak extraction ability towards light REEs(III) and high stripping acidity for heavy REEs(III). It has better separation performance for metal ion impurities than P204 and P507, especially for the typical impurity Al(III). Furthermore, the HPOAc system has better phase separation behavior and extraction phenomena. A simulated operation with two-stage counter-current extraction and single-stage stripping of REEs was carried out using unsaponified HPOAc. The recovery of REEs reaches 98.7%. The concentration of REEs increases from 0.44 to 130.35 g/L, indicating a nearly 300-fold increase. Furthermore, the content of REEs increases from 77.8 wt% to 97.6 wt%. So HPOAc has the potential to selectively recover REEs from sulfate leachates of IATREO.

Extraction of Rare Earth Elements from Brown Coals of the Sergeevskoe Deposit (Amur Region) According to Experimental Data

A series of experiments on the leaching of rare earth elements (REEs) from Miocene brown coals of the Sergeevskoe deposit with water and alkaline and acid solutions was carried out. Using a set of methods (ICP MS, XRD analysis, heavy concentrate analysis, SEM EDS, and IR spectrometry), it was revealed that acid leaching was the most effective: 72–99% of REEs was extracted with a 1 M solution of hydrochloric acid in 24–48 h. This fact indicates that most of the REEs in the brown coals of the Sergeevskoe deposit were associatedwith the organic matrix in the form of complexes with the carboxyl groups of humic and fulvic acids. The high percentage of REE extraction indicates the possibility of using coals from the Sergeevskoe deposit as an easily enriched source of REEs.

Effect of Bridging Group Nature on the Extraction Ability of Diphenylphosphorylketones toward Actinides and Lanthanides

Effect of structure of phosphorylketones containing flexible alkyl and conformationally rigid fragments in the linker on extraction ability toward actinides and lanthanides has been studied. It has been shown that the introduction of conformationally rigid cycloalkanediyl and alkenediyl fragments in the bridge between P=O and C=O groups in the structure of molecule decreases efficiency of extractants for both actinides and lanthanides. At the same time, the introduction of flexible alkyl groups in linker structure increases complexing and extraction ability. This dependence has been explained theoretically by modeling complexation (DFT, PBE, cc-pVDZ), monodentate coordination was observed for all studied phosphorylalkanones

Assessment of Viability of Coal Mines in Tanzania for Extraction of Rare Earth Elements

This study aimed at determining the concentrations of rare earth elements (REEs) in coal and coal fly ash (CFA) from three coal mines in Tanzania: Kiwira, Ngaka and Rukwa. The goal was to assess if these resources could be commercially viable for extracting REEs. Coal and CFA samples were analysed using X-ray fluorescence (XRF) spectrometry and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The total concentrations of REEs in the coal samples ranged from 89.48 parts per million (ppm) to 196.30 ppm, while in CFA samples, ranged from 362.55 ppm to 475.77 ppm. Computed percentage of critical REEs (REYdef, rel%) and outlook coefficient (Coutl) values ranged from 27.41% to 50.74% and 0.62 to 2.00, respectively. Based on the evaluation criteria proposed for assessing coal and coal ash as sources of REEs, the results suggest that the studied coal and CFA samples have the potential to be used as sources of REEs for economic development. These findings have important implications for the Tanzanian government and other relevant authorities, as they provide valuable insights into the feasibility of investing in the coal and coal ash as promising sources of REEs. This is particularly significant considering the high global demands for REEs.

Determination and prediction of micro scale rare earth element geochemical associations in mine drainage treatment wastes

Acid mine drainage (AMD) has been proposed as a novel source of rare earth elements (REE), a group of elements that includes critical metals for clean energy and modern technologies. REE are sequestered in the Fe–Al–Mn-rich precipitates produced during the treatment of AMD. These AMD solids are typically managed as waste but could be a REE source. Here, results from AMD solids characterization and geochemical modeling are presented to determine the minerals/solid phases that are enriched in REE and identify the mechanism(s) of REE attenuation.AMD solids collected from limestone-based AMD treatment systems were subjected to sequential extraction and synchrotron microprobe analyses to characterize the binding nature of the REE. The results of these analyses indicated REEs were mainly associated with Al or Mn phases. Only selected REE (Gd, Dy) were associated with Fe phases, which were less abundant than Al and Mn phases in analyzed samples. The sequential extractions demonstrated that acidic and/or reducing extractions effectively mobilize REE from the AMD solids evaluated. The observed element associations in solids are consistent with geochemical model results that indicate dissolved REE can be effectively attenuated by adsorption on freshly precipitated Fe, Al, and Mn oxides/hydroxides. The model, which simulates dissolution of CaCO3 and the precipitation of Fe, Al, and Mn oxides with increased pH, accurately predicts the pH dependent accumulation of dissolved REE with Al, Mn, and Fe oxides/hydroxides in the studied AMD treatment systems.The methods and results presented here can be used to identify conditions favorable for accumulation of REE-enriched AMD solids and possible passive or active treatment(s) to extract REE from AMD. This information can be used to design AMD treatment systems for the recovery of REE and is an opportunity to transform the challenges of addressing polluted mine drainage into an environmental and economic asset.

Constrained Model Predictive Control Based on Event Triggering for the Rare Earth Extraction Process.

Since the reagent dosage is manually adjusted according to work conditions, an event-triggered constrained model predictive control is proposed for rare earth extraction. First, the linear predictive system, based on a state space model, is established. Subsequently, the feedback correction link is fine-tuned to reduce the prediction error. Following this, an objective optimization function, incorporating input and output constraints, is introduced to calculate the appropriate reagent dosage. Finally, an event-triggering mechanism, underpinned by a designated threshold, is designed to update the controller. Simulation outcomes substantiate the efficacy of the proposed approach.

Optimal Extraction and Separation of Europium and Samarium from Nitrate Medium Using Binary Mixture of Cyanex 572 and Tertiary Amine Extractants

ABSTRACT Extraction and separation of rare-earth elements (Eu(III) and Sm(III)) from nitrate solutions were studied using Cyanex 572 and Alamine 336 type extractants, as well as their binary mixtures in kerosene. Separate studies were carried out on the parameters that influence the extraction process. According to the slope analysis method, the composition of extracted species in the organic phase is [MNO3A2(HA)2][R3NH.NO3]2(Org). The mixture loading capacity towards Eu(III) and Sm(III), as well as the stripping of their loads from the organic phases, were also tested. After being treated with a NaOH solution, the stripped binary mixture was regenerated. The FT-IR spectra of the binary mixture organic phase, the organic phase loaded with metals, the stripped organic phase, and the regenerated organic phase were identified and compared. The separation method is based on a combined reduction-precipitation process in which europium is reduced to its bivalent state by commercial zinc metal, followed by the precipitation of its sparingly soluble europous sulphate. The developed method was used to separate a synthetic mixture of Eu(III) and Sm(III) from an analogous solution in nitrate medium to that expected from spent nuclear fuel leach liquor. Extraction and separation processes for Eu(III) and Sm(III) were detailed in a flowchart.

Neodymium sorption on the Na-form of Transcarpathian clinoptilolite

The sorption properties of Na-modified Ukrainian Transcarpathian clinoptilolite towards neodymium aqueous solutions under dynamic conditions have been investigated. The sorption capacity of the Na-from of Transcarpathian clinoptilolite towards Nd(III) significantly depends on the concentration of neodymium salt, the pH of the solution, and the heat treatment temperature of the sorbent. Nd(III) is most efficiently sorbed from slightly alkaline solutions (pH 8.5), mainly by adsorption of neutral hydrolyzed forms of Nd(OH)3 on the surface of Na-clinoptilolite samples preheated at 75 °C. During the passage of an Nd(III) solution with a concentration of 1 μg mL−1 through the sorbent at a rate of 3 mL min−1 under optimal conditions, the sorption capacity of Na-clinoptilolite is 7.2 mg g−1, which is in 4 and 2.3 times higher than that of natural and acid-modified forms of this zeolite. It is shown that under the experimental conditions with an increase in the flow rate, the thickness of the stationary surface layer decreases, which leads to a decrease in the sorption capacity of Na-clinoptilolite. The best Nd(III) desorbents are solutions of mineral acids and acidified solutions of alkali metal salts (except NaCl), which provide 93–98 % extraction of lanthanide from the zeolite matrix. The method for neodymium trace amounts preconcentration from aqueous solutions in a solid-phase extraction mode with a further determination of this rare earth element by a spectrophotometric method was developed. The detection limit of this method is 0.75 ng mL−1 and the linearity was evaluated in the range of 2.5–500 ng mL−1.

The influence of low-permeability geological inclusions on the seepage behavior of ionic rare earth leaching mining: A study using visual microfluidic technology

Ionic rare earth deposits often contain semi-weathered or slightly weathered low-permeability geological inclusions (LPGI), which significantly impact the permeation process and leaching efficiency of in-situ liquid leaching mining. To investigate the influence of LPGI with varying developmental degrees on the seepage process of ionic rare earth leaching mining, we developed six microfluidic chip models using Polydimethylsiloxane (PDMS). A visual experiment was conducted, employing water to drive gas at a rate of 0.5 μl/min, enabling observation of the seepage and displacement process. Using MATLAB image processing technology in conjunction with time-history diagrams, we analyzed the evolution patterns of the infiltration front position and saturation over time. Our findings revealed distinct capillary fingering and side wall flow phenomena during the process of liquid phase displacing gas phase infiltration, accompanied by horizontal and counter flows perpendicular to the solution's direction of advancement. Notably, when the solution traversed the LPGI, we observed significant flow-around phenomena and low saturation of the LPGI. These inclusions hindered solution infiltration, with wider LPGI resulting in greater inhibition. Additionally, the LPGI acted as a protective barrier, preventing solution intrusion into the underlying ore body. However, due to the air discharge is not timely, it was sealed by the outlet solution, forming a substantial leaching blind area near the outlet. This study unveils the seepage laws of ionic rare earth earth leaching mining involving LPGI of various developmental degrees, signifying its vital engineering significance in the efficient extraction of ionic rare earth.

Synergistic, extractive, and selective separation of light, medium, and heavy rare earth elements using Cyanex 572 and Alamine 336 from a chloride medium

In this study, the solvent extraction of rare earth elements (REEs) of different groups of light (LREE), medium (MREE), and heavy (HREE) from a chloride medium using the mixture of Cyanex 572 (cationic extractant, organophosphorus-based) and Alamine 336 (anionic extractant, amine-based) was studied. The results showed higher extraction efficiency for HREEs when sole Cyanex 572 was used. However, the addition of Alamine 336 to Cyanex 572 increased the extraction efficiency of LREEs and MREEs. The optimal volumetric ratio of Alamine 336 to Cyanex 572 for maximum extraction efficiency, under the studied conditions, was concluded to be 1:1 at a total extractant concentration of 30 % v/v. The synergistic enhancement factor when using this system for the extraction of LREEs and MREEs varied from 2 to 76 at different pH values and Alamine 336 ratios. To analyze the synergistic effect of the addition of Alamine 336 to Cyanex 572 on REE extraction, slope analysis and Fourier transform infrared spectroscopy measurement were performed. It was concluded that the role of Alamine 336 could be that of a proton ion extractor (released from the Cyanex 572 structure during REEs extraction) for REECl2+ complexes and that of a phase modifier for Cyanex 572 for REECl2+ complexes.

Parametric study of an acid baking process for rare earth element recovery from a bituminous-coal source

ABSTRACT Acid baking treatment is widely used to extract rare earth elements (REEs) from refractory rare earth bearing minerals such as monazite and xenotime. Since these REE minerals have been identified in coal-based sources, a parametric study was conducted to evaluate the impact and optimize the parametric values associated with the acid-baking process when treating a bituminous coal source. The parameters studied using a three-level statistical experimental program were acid baking time, acid solution concentration, baking temperature, and acid solution-to-solids ratio and each were found to significantly impact REE and contaminant element recovery. An increase in baking temperature up to around 250°C improved the light and heavy REE recovery values by more than 50 absolute percentage points relative to performances achieved when direct leaching. Acid baking was needed to dehydroxylate the clays and liberate the REE minerals, which allowed access for the acid to solubilize the REEs. Acid concentration of the solution used for acid baking was studied as a means of minimizing the amount of acid needed to achieve a target REE recovery. However, thermo-gravimetric and differential scanning calorimetry analysis (TGA-DSC) of sulfuric acid under oxidizing atmosphere revealed that the addition of water decreased the evaporation temperature, which explains the lower REE recovery values obtained when using lower acid concentrations. Using pure sulfuric acid at an acid-to-solid ratio of 0.8:1 resulted in recovery values of around 70% for both LREEs and HREEs. The decomposition reaction time was relatively quick with 65% of the TREEs recovered within the first 10 minutes. Water leaching experiments performed on the acid-baked products under a temperature of 25°C instead of 75°C revealed an increase in REE recovery by 10 absolute percentage points, which was likely due to the high solubility of REE-sulfates at room temperatures.

Effective extraction of rare earth elements from ion-adsorption type rare earth ore by three bioleaching methods

Rare earth elements (REEs) are essential elements in many technology industries. The commonly used ammonium salt method has caused a bad impact on environment. Bioleaching is widely recognized as a low energy, relatively simple and environmentally friendly method. The purpose of this work is to extract REEs from ion-adsorption type rare earth ore by using three different bioleaching methods (one-step, two-step, and spent medium method, respectively) and the strain used was Aspergillus niger strain. Major organic acids produced during microbial growth were detected and the REEs leaching efficiency of three methods was compared. In addition, the interaction between the strain and their metabolites and rare earth ore was investigated by FT-IR, XRD, SEM-EDS, and TEM-EDS during the leaching process. In the end, it was found that the spent medium method had the best leaching effect, and various characterization methods showed that the three bioleaching methods had obvious changes before and after leaching, among which the spent medium method had the most significant effect. Additionally, through the analysis, it can be concluded that the complexation and acidolysis may occur in the bioleaching process.

Hydrometallurgical processing of ash and slag waste

This work assesses the possibility of hydrometallurgical processing of ash and slag waste in order to extract rare and rare earth elements. The ash and slag waste from the Chita CHPP-2 combined heat and power plant was used as a research object. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to determine the elemental chemical composition of coal combustion products. To preconcentrate rare and rare earth elements, magnetic separators were used to isolate the -0.5+0.3 mm and -0.3+0.1 mm grain size fractions of ash and slag waste. The leaching of rare and rare earth elements from the studied samples was investigated using sulfuric, hydrochloric, and nitric acids, as well as an aqua regia solution, in combination with simultaneous ultrasonic exposure. It was determined that electromagnetic separation of the -0.5+0.3 mm and -0.3+0.1 mm grain size fractions of ash and slag waste significantly concentrates rare and rare earth elements in the magnetic fraction, including titanium (up to 25%), zircon (up to 33%), yttrium (up to 50%), lanthanum (up to 150%), and cerium (up to 5%). It was determined that an increase in the duration of ultrasonic treatment during the leaching of metals from ash and slag waste with sulfuric acid resulted in a uniform 7.25-fold increase in gallium content (from 0.008 to 0.058 g/dm3). Additionally, when decomposed with aqua regia, a 3-fold concentration of the same element was observed (from 0.008 to 0.024 g/cm3), while ultrasonic treatment offered only a slight increase in concentration. When leaching with sulfuric acid (the duration of ultrasonic exposure is 5 minutes), a 4-fold increase in the rubidium content was observed (from 0.108 to 0.457 mg/dm3). Therefore, the most effective method for extracting rare and rare earth elements from the ash and slag waste of Chita CHPP-2 involves acid leaching combined with electromagnetic separation and ultrasonic pulp leaching.

Extraction of Rare-Earth Elements from Chloride and Nitrate Solutions in Multicomponent Systems with Di(2-ethylhexyl)phosphoric Acid

Extraction of Rare-Earth Elements from Chloride and Nitrate Solutions in Multicomponent Systems with Di(2-ethylhexyl)phosphoric Acid

Innovative Environmentally Safe Processes for the Extraction of Rare and Rare-Earth Elements from Complex Ores of Perplexed Material Composition

Domestic and world tendencies of involvement in the processing of ores of rare metals (RMs) and rare-earth metals (REMs) are shown. It is shown that the main direction of innovative activity is the development and application of modern breakthrough technologies for complex processing of mineral raw materials with the production of high-quality products while minimizing environmental damage. The main deposits of rare and rare-earth metals are systematized from the standpoint of the content of the main components, concentrator minerals and the main enrichment methods. The main principal technological schemes of processing of some deposits of RMs and REMs in Russia (Lovozer, Tomtor, and Afrikand deposits) are given. Options for involving technogenic and off-balance raw materials in the processing in order to extract strategic metals are considered. It is substantiated that innovative environmentally friendly processes for the extraction of rare and rare-earth metals from complex ores of complex material composition are being actively developed in Russia at present.

Extraction of Actinides and Lanthanides from Nitric Acid Solutions with Diphosphine Dioxides in the Presence of an Ionic Liquid

Extraction of Actinides and Lanthanides from Nitric Acid Solutions with Diphosphine Dioxides in the Presence of an Ionic Liquid

Recycling of NdFeB magnets: Model supported iron minimization via in-situ hydrolysis during leaching and hematite precipitation in an autoclave

The NdFeB magnets are a significant component of technological applications, which contain a remarkable quantity of rare earth elements (REEs). For this reason, the recycling of NdFeB magnets is essential for the reuse of these elements. This research represents the recycling strategy of NdFeB magnets, which consists of iron minimization through in-situ hydrolysis during oxidative leaching and hematite precipitation in an autoclave. The influence of the experimental parameters in the hydrolysis of Fe3+ in a nitric acid medium on the formation of a mixture of iron oxide hydroxide was examined in detail. Afterward, the effect of the temperature, time and, water addition on the iron and REEs precipitation in the autoclave was investigated by the ANOVA analysis based on the Box-Behnken design. According to the particle swarm optimization algorithm, maximum REEs extraction and minimum iron extraction were achieved in a solution of 1.82 mol/L nitric acid, at a solid/liquid ratio of 11/100, a temperature of 60 °C, and a stirring speed of 415 rpm. The mean leaching efficiencies of REEs and iron are calculated to be 76% and 7%, respectively. The optimal parameters for hematite precipitation in the autoclave were determined to be a process temperature of approximately 137 °C, a processing time of approximately 3 h and 55 min, and a water addition of approximately 20%. The optimum parameters are in harmony with the validation experiments.

Controlling Extraction of Rare Earth Elements Using Functionalized Aryl-vinyl Phosphonic Acid Esters.

Ligands that can discriminate between individual rare earth elements are important for production of these critical elements. A set of aryl-vinyl phosphonic acid ligands for extracting rare earth elements were designed and synthesized under the hypothesis that the strength of the rare earth-ligand interactions could be tuned by changing the dipole moment of the ligand. The ligands were synthesized via a two-step reaction procedure using a Heck coupling reaction to functionalize vinyl phosphonic acid, followed by Steglich esterification to obtain high-purity styryl phosphonic acid monoesters with varying dipole moments along the P-C bond. The metal binding strength and composition of the rare earth complexes formed with these styryl phosphonic acid monoesters were experimentally studied by liquid-liquid extraction techniques, while DFT calculations were performed to determine the dipole moments of the free and complexed ligands and the electronic structure of the complexes formed. All three prepared ligands were much stronger extracting agents for europium(III) than the dialkylphosphonic acids usually used for this separation. However, the order of increasing extraction strength was found to match the order of the decreasing calculated dipole moment along the P-C bond of the three styryl-based ligands, rather than correlating with increasing ligand basicity, as reflected by the pKa of the ligands. These findings suggest that this approach can be used to systematically alter the extraction strength of aromatic phosphonic monoesters for rare earth element purification.

A near-zero waste process for the full-component utilization of deep-sea polymetallic nodules based on reductive leaching with SO2 followed by separation and recovery

Recovery of critical metals from marine minerals is a promising option to ensure the sustainable supply of critical metals, but existing recovery processes suffer from technical bottlenecks in terms of low resource utilization and large waste discharge. This paper presents a complete hydrometallurgical route for the full-component utilization of deep-sea polymetallic nodules (DPN). Leaching experiments were first carried out in the presence of SO2 because cheap SO2 can destroy the original mineral structure based on a reductive mechanism. The leaching efficiencies of Ni, Co, Mn, Cu, La, Ce, and Fe were reached 99.2%, 99.3%, 98.7%, 95.9%, 95.3%, 95.4%, and 91.4%, respectively, under the optimal conditions of 30 °C, L/S ratio of 6:1 mL/g, H2SO4 dosage of 37.5 wt%. The downstream process aimed at the sequential recycling of metal ions from the pregnant leach solution (PLS) consists of Fe recovery by the hematite process, selective solvent extraction of Cu and rare earth elements (REEs), co-extraction of Ni/Co/Mn, and Mn electrowinning. As a result, high-grade hematite (60 wt% of Fe), industrial-grade CuSO4, mixed rare earth oxides, battery-grade (Ni, Co, Mn)SO4 solution, and electrolytic manganese were obtained. During the whole process, the recovery efficiency of Ni, Co, Mn, Cu, La, Ce, and Fe reached 97.1%, 97.1%, 96.9%, 91.5%, 91.1%, 91.1%, and 91.3%, respectively. Since the hydrometallurgical process achieves the resource utilization of all the DPN constituents, it has the advantages of near-zero waste and low energy consumption.

Extraction of rare earth elements from monazite leach liquor using functionalized chitosan sorbents derived from shrimp waste

With the growing need for high-purity rare-earth elements (REEs), the separation of these REEs has received much attention recently. The objective of this research is to produce chitosan from shrimp waste, then modify it with different functionality, and investigate the adsorption properties of chitosan adsorbents towards La(III) ions. First, from shrimp waste, chitosan (ch) with a significant degree of deacetylation, purity, and solubility was produced. The purified chitosan was cross-linked with epichlorohydrin (ep), and then, it was modified with 3,6,9,12-tetraazatetradecane-1,14-diamine (HA) to produce polyaminated chitosan (HA@ep@Ch). The polycarboxylated/imine chitosan (CM@HA@ep@Ch) was obtained by treating polyaminated chitosan with chloroacetic acid in isopropyl alcohol. The chitosan adsorbents were characterized and applied for lanthanum recovery from synthetic and monazite leach liquor samples. The factors controlling the recovery process were studied and discussed. The performance of the adsorbents was achieved through equilibrium, dynamic, and isothermal studies. HA@ep@Ch and CM@HA@ep@Ch showed good performance for lanthanum recovery with a maximum capacity of 114.52 and 141.76 mg/g at 330 K, respectively. The isotherm parameters refer to the monolayer of lanthanum adsorbed into the adsorbents through chelation and ion exchange mechanisms. A 0.5-M HCl solution was found effective to elute 95.8% of the adsorbed lanthanum on HA@ep@Ch, and 93.4% of the adsorbed lanthanum on CM@HA@ep@Ch. The adsorbents showed greater selectivity in extracting La, Ce, Pr, Nd, and Sm (62–75%) from REE leach liquid compared to extracting other REEs (20–41%).