Mixed Rare Earth Research Articles

Preparation of rare earth oxides from Synchysite oxidized ore by acid leaching

Mixed rare earth oxides have been prepared from synchysite ore from the Lugiin gol rare earth deposit (Mongolia) which contains about 6% of cerium light rare earth elements. Ore powders were leached for up to 60 min using 80-120 g/l sulfuric acids at an acid to powder ratio of 20, agitation was performed by magnetic stirring followed by precipitation and calcination at 700°C for 1h. The highest leaching of REEs equal to 85% of the total REE was observed in the acid solution of 80 g/l. Obtained mixed rare earth oxides represent a layered type structure.

Effect of Mixed Rare Earths on the Wetting Behavior and Interfacial Reaction between Sn-0.70Cu-0.05Ni Solder and Amorphous Fe84.3Si0.3B5.4 Alloy

In order to explore the effect of addition of mixed rare earths (MRE) on the wetting behavior and interfacial reaction between Sn-0.70Cu-0.05Ni solder and amorphous Fe84.3Si10.3B5.4 alloy, 0.25 wt.% percentage of the MRE, which are mainly elements La and Ce, were added into the solder. Results show it can refine the microstructure of the solder alloy, and there is limited change of melting temperature with the addition of MRE in the solder. The wettability of the solder on amorphous substrate is improved by adding 0.25 wt.% percentage of the MRE into Sn-0.70Cu-0.05Ni solder. Moreover, research results indicate that, with the increase of wetting temperature, the final equilibrium wetting angles of Sn-0.70Cu-0.05Ni and Sn-0.70Cu-0.05Ni-0.25MRE on amorphous substrate decrease gradually, indicating the better wettability at the higher wetting temperature. In addition, with the increase of temperature, the distribution of intermetallic compound (IMC) FeSn2 formed at the interface between the two solders and amorphous substrate is changed from discontinuous state to continuous state. The thickness of the interfacial IMC layer between solder and amorphous substrates reduced with the addition of MRE, indicating that the presence of 0.25 wt.% percentage of the MRE is effective in suppressing the growth of IMC layer.

Selective Process Steps for the Recovery of Scandium from Jamaican Bauxite Residue (Red Mud)

We report the development of a process allowing the selective, sustainable recovery of scandium (Sc) with 75% efficiency from Jamaican bauxite residue (red mud), a waste product from aluminum production. The process design is inspired by green chemistry principles and focuses on establishing highly selective process steps (sulfation, leaching, and precipitation) in order to minimize costs and waste produced. In addition to scandium oxide, the chosen approach produces mixed rare earth oxides as a side product, thus isolating an average of 88% of all rare earth elements contained in red mud. Furthermore, in light of predicted supply shortages of the critical material Sc and the need to establish cost-effective bauxite residue remediation techniques, a systematic Monte Carlo-based economic performance assessment framework is developed in order to evaluate the economic prospects of the proposed process system in the presence of irreducible uncertainty.

Effect of oxidation behavior of cerium during the roasting process on the leaching of mixed rare earth concentrate

Herein, the phases of mixed rare earth concentrate, oxidative roasted ore, non-oxidative roasted ore, together with their leaching processes and mechanisms, were studied. XRD and SEM-EDS patterns indicate that the phases of the ore roasted in both air and argon atmospheres at 550°C for 2h are (Ce, La)OF and REPO4. Ce oxidized from trivalent to tetravalent during the roasting process, causing the lattice distance of the crystals to decrease, and the cracks on the surface of mineral to widen. Cerium extraction in the oxidative roasted ore is 3.2% at a low temperature and low acidity, which is less than 8.6% of the other rare earths. However, at 80°C, Ce extraction can reach 52% at 2min in a 3mol/L hydrochloric acid solution. Analysis of fluorine extraction and SEM-EDS analysis of the leaching residue reveal that Ce(IV) complexes with F− rapidly, and this complex can promote the leaching of total rare earths. With time, Ce(IV) is reduced to its trivalent form, while Cl− is oxidized to Cl2. F− in the solution and RE(III) generate REF3 and go into the slag, which decreases Ce extraction from 52% to 48.1% and those of other rare earths from 51% to 41%. Although the leaching rates of Ce and other rare earths in a non-oxidative roasted ore cannot reach the same level as the ore oxidative roasted at a high temperature, they are relatively high. F− extraction is slightly lower than that of the oxidative roasted ore. The kinetics of the leaching process and SEM analysis of the leaching residue also confirm this.

Observation of Intense X-ray Scintillation in a Family of Mixed Anion Silicates, Cs3RESi4O10F2 (RE = Y, Eu-Lu), Obtained via an Enhanced Flux Crystal Growth Technique.

A new family of mixed anion cesium rare earth silicates exhibiting intense scintillation in several ranges of the visible spectrum are reported. Cs3RESi4O10F2 (RE = Y, Eu-Lu) have been synthesized using an enhanced flux growth method for the targeted growth of mixed anion systems. This is the first example of this method being used for the growth of oxyhalides. The compounds crystallize in the triclinic space group P1̅ with the lattice parameters a = 7.0832(2) Å, b = 7.1346(2) Å, c = 16.2121(5) Å, α = 95.8090(10)°, β = 90.0580(10)°, γ = 119.7650(10)° for the Tb analogue. The structure consists of REO6 and REO2F4 polyhedra connected by Si4O10 sheets with a previously unobserved silicate sheet topology that contains the uncommon cyclic Si3O9 trimers. The synthesis, structure, magnetic and optical properties are reported including, notably, intense X-ray scintillation in Cs3TbSi4O10F2.

Solvent extraction and separation of cerium(III) and samarium(III) from mixed rare earth solutions using PC88A

The solvent extraction of cerium(III) and samarium(III) from mixed solutions of all rare earth elements (REEs) except promethium using PC88A (2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester), an acidic extractant, was investigated. The effects of aqueous equilibrium pH, various acids (sulfuric acid (H2 SO4), hydrochloric acid (HCl) and nitric acid (HNO3)), initial metal ion concentration and extractant concentration on the solvent extraction of Ce(III) and Sm(III) were systematically studied. From the experimental results, HNO3 and HCl were found to be the preflerred aqueous media for the solvent extraction of both Sm(III) and Ce(III). The most promising experimental conditions of pH, PC88A concentration and metal ion concentration were identified for the extraction of Ce(III) and Sm(III). Separation results showed that H2 SO4 at pH 2 provided the best separation between Sm(III) and Ce(III).

High pressure structural phase transitions in Ho: Eu2O3

Structural stability and phase transitions in mixed rare earth sesquioxides (Eu1−xHox)2O3 crystallizing in the cubic bixbyite structure were investigated under high pressure using angle dispersive X-ray diffraction technique. Studies on various compositions of the mixed oxide show that when the average cationic radius, RRE (where, RRE = xRHo+(1−x)REu) is equivalent to or below 0.9164 Å, the system undergoes a cubic to monoclinic transition as a function of pressure, whereas, when RRE equivalent to or above 0.9220 Å it is observed to prefer a transition from cubic to hexagonal structure. Based on our detailed investigations, a pressure-concentration (P−x) phase diagram for (Eu1−xHox)2O3 up to a pressure of 15 GPa is constructed. The bulk moduli for the parent and high pressure phases are calculated from the Birch-Murnaghan equation of state fit to the experimental pressure volume data and are reported. Structural analysis based on refinement has revealed that, an increasing structural rigidity of the cubic phase with decreasing RRE leads to an increase in the transition pressure and bulk moduli except for 0.4 ≤ x ≤ 0.6. The observed significant reduction in bulk moduli and transition pressure for 0.4 ≤ x ≤ 0.6 is due to the increased micro strain/internal pressure developed upon doping.

Leaching kinetics of rare earth elements and fluoride from mixed rare earth concentrate after roasting with calcium hydroxide and sodium hydroxide

The complex leaching kinetics of rare earth elements and fluoride with a HCl-AlCl3 solution was investigated for the mixed rare earth concentrate after roasting with calcium hydroxide and sodium hydroxide. The effects of HCl concentration, temperature, reaction time, liquid-solid ratio (L/S), AlCl3 concentration and stirring speed on leaching kinetics were explored. The results show that the extractions of REEs and fluoride were 86.05% and 90.23%, respectively, under the conditions: 3mol/L HCl, 0.5mol/L AlCl3, 70°C, 10mL/g liquid-solid ratio, 300rpm stirring speed and 40min. The XRD and SEM analysis of the samples before and after acid leaching show that the rare earth oxides and fluorite were completely leached. The apparent activation energies of leaching REEs and fluoride were calculated, which were 26.95kJ/mol for REEs and 20.70kJ/mol for fluoride. The kinetic data of extractions of REEs and fluoride all fitted a new variant of the shrinking core model, in which both the interfacial transfer and the diffusion through the product layer affected the reaction rate.

Mixed rare earth oxides derived from monazite sand as an inexpensive precursor material for room temperature magnetic refrigeration applications

An inexpensive perovskite type (REMIX)0.67Sr0.33MnO3 compound is synthesized via solid state method using mixed rare earth oxide precursor derived from monazite sand. Rietveld refinement of X-ray powder diffraction patterns confirms the compound is a mixture of rare earth manganites which is the major phase and CeO2 as the secondary phase. The compound shows a second order ferromagnetic to paramagnetic transition near room temperature and exhibits a magnetic entropy change (-ΔSM) of 3.28Jkg−1K−1 with a relative cooling power (RCP) of 120Jkg−1 and an adiabatic temperature change (ΔTad) of 2.11K at 310K under 50kOe magnetic field. The Debye temperature of the compound is found to be 543K and room temperature thermal conductivity is 4.26Wm−1K−1. The temperature variation of electrical resistivity shows a metal to insulator transition around 180K, which gets shifted towards higher temperature upon the application of magnetic field. The compound shows a large value of −ΔSM and this work makes an endeavor to develop low–cost materials for the magnetic refrigeration applications near the room temperature.

Development of solvent extraction methods for recovering rare earth metals

Published works conducted in Russia and other countries over the last 10–15 years regarding the application of solvent extraction in technological processes for recovering rare earth metals from various mineral and technogenic raw materials (bastnesite, monazite, loparite, xenotime, kularite, etc.) were analyzed in the present review. Raw materials containing rare earth are beneficiated by flotation, magnetic or gravity methods to produce rare earth concentrates, which are undergone hydrometallurgical processing. Rare earthcontaining concentrates or calcined residues are usually treated with inorganic acids. Then individual or mixed rare earths are extracted from pregnant leach solutions by solvent extraction. Various commercial extractants belonging to different classes are used for extraction. A large number of stages are usually required to separate rare earth metals.

Effects of La and Ce Mixed Rare Earth on Microstructure and Properties of Al-Mg-Si Aluminum Alloy

The effects of La and Ce mixed rare earth on the microstructure and properties of Al-0.75Mg-0.6Si alloy were studied by optical microscopy, digital eddy current conductive instrument and tensile testing machine. Results showed that the addition of La and Ce mixed rare earth had a positive effect on the grain refinement of Al-0.75Mg-0.6Si alloy, which is beneficial to improve the electrical conductivity and strength. With increasing the additive amount of La and Ce mixed rare earth, the electrical conductivity, tensile strength and elongation of Al-0.75Mg-0.6Si alloy gradually increased. When the additive amount of La and Ce mixed rare earth increased to 0.5%, the electrical conductivity of Al-0.75Mg-0.6Si alloy was 55.7% IACS, the tensile strength and elongation of Al-0.75Mg-0.6Si alloy were 236 MPa and 16.7%, respectively. The electrical conductivity increased by 5.7%, tensile strength and elongation increased by 11.3% and 15.2% compared with that of Al-0.75Mg-0.6Si alloy without adding the La and Ce mixed rare earth.

Comparative study of the application of chelating resins for rare earth recovery

The adsorption properties of chelating ion exchange resins containing mixed sulfonic/phosphonic (SP), aminophosphonic (AP) or iminodiacetic (IDA) acid functional groups were investigated towards the rare earth elements (REE). The aim of this work was to determine the potential for such resins to assist in the isolation of a mixed rare earth product under conditions relevant to the hydrometallurgical processing of rare earth containing minerals. The selectivity of the resins towards La, Sm and Ho, versus the common impurity metals; Al, Fe and Th, was determined in sulfuric acid media. The chelating resins all displayed a similar selectivity with Fe and Th adsorbed in preference to the REE and Al (i.e. Th≃Fe≫REE≃Al). The IDA resin displayed a far superior performance compared to both phosphonic resins (SP and AP) as well as a strong acid cation exchange resin for the adsorption of REE in the presence of very high Na or Ca concentrations. Equilibrium and kinetic adsorption isotherms for La were measured and successfully modelled with all resins, and the elution characteristics of selected resins investigated in both batch and column operation. A number of areas were identified where these resins could be exploited to provide an advantage in the hydrometallurgical processing of REE.

Rare earth chloride and nitrate salts as individual and mixed inhibitors for aluminium alloy 7075-T6 in chloride solution

ABSTRACTThe aim of the study was to investigate various rare earth salts as corrosion inhibitors of aluminium alloy 7075-T6. Rare earth salts, CeCl3, LaCl3, Ce(NO3)3 and La(NO3)3, were studied, first as individual inhibitors in the concentration range between 0.001 and 0.05 M. Second, the inhibitory effect of mixtures of chloride or nitrate salts was studied at an overall inhibitor concentration of 0.01 M. The corrosion properties of AA7075-T6 in the absence and presence of individual and mixed rare earth salts were investigated using electrochemical potentiodynamic technique in 0.1 M NaCl. The topography, morphology and composition of the inhibited surfaces were recorded. The highest inhibitory effectiveness was exhibited by CeCl3, followed by mixtures of CeCl3 and LaCl3. During immersion for 12 h the corrosion protection remained high. Nitrate rare earth salts showed less protection, both as individual or as mixed inhibitors. Deposits containing both cerium and lanthanum were formed primarily on Cu-based intermetallics.

稀土化合物对铝合金精炼熔剂净化效率的影响

本文配置了含不同混合稀土成分的精练熔剂，以及熔剂和铝粉的混合物。研究精炼熔剂对铝熔体的精炼效果的影响，通过金相分析、熔体当中气杂含量的测定、熔剂的差示热扫描(DSC)以及动力学曲线拟合。研究结果表明含混合稀土4 g的混合精炼剂具有较低的熔点621℃，并且具有较好的精炼效果，当混合稀土添加量增加时，精炼效果降低。精炼剂中的硫酸盐对精炼效果有促进作用。 A refined flux containing different mixed rare earth elements and a mixture of flux and aluminum powder were arranged in this paper. The effect of refining agent on the refining of aluminum melt was studied by metallographic analysis, determination of gas miscellaneous content in melt, dif-ferential thermal scanning (DSC) and kinetic curve fitting of flux. The results show that the mixed refining agent with 4 g of mixed rare earth has a lower melting point of 621℃, which has a good refining effect. When the amount of mixed rare earth is increased, the refining effect is reduced. The sulphate in the refining agent has a catalytic effect on the refining effect.

Influence of Na+, K+, Mn2+, Fe2+ and Zn2+ ions on the electrodeposition of Ni-Co alloys: Implications for the recycling of Ni-MH batteries

A hydrometallurgical recycling procedure for the recovery of a mixed rare earths sulfate and an electrodeposited Ni-Co alloy has been described. The latter step was found to be complex, due to the presence of several ions in the battery electrode materials. Electrochemical evaluation of the influence of the ions on the Ni-Co alloy deposition was carried out by cyclic voltammetry test. It was found that ions such as K+, Fe2+ and Mn2+ improved the current efficiency for the Ni-Co deposition process on a copper surface. On the other hand, Na+ and Zn2+ ions exhibited a deleterious behaviour, minimizing the values of the reduction current. The results were used to suggest the inclusion of additional steps in the process flow diagram of the recycling operation, in order to eliminate deleterious ions from the electroplating solution.

Extraction kinetics of mixed rare earth elements with bifunctional ionic liquid using a constant interfacial area cell

Extraction kinetics of mixed REEs including La–Lu plus Y except Pm using constant interfacial area cell as equipment and bifunctional ionic liquid as extractant were reported.

Solvent-free mechanochemical synthesis and magnetic properties of rare-earth based metal-organic frameworks

Mechanical milling of benzene 1,3,5-tricarboxylic acid [C6H3(COOH)3], both with the single and mixed rare earth carbonates [R2(CO3)3·xH2O; R = Gd, Tb and Dy], leads to the formation of metal-organic frameworks [R{C6H3(COO)3}] that adopt MIL-78 type structure. M(T) data of the investigated MOFs do not show any apparent onset of long range magnetic ordering down to 2 K. The M(H) data for Gd{C6H3(COO)3}collected at 2 K show deviations from the magnetization behavior expected for non-interacting Gd3+ ions. For the Gd based MOF the temperature dependence of the isothermal magnetic entropy change (i.e. magnetocaloric effect, ΔSM) exhibits a monotonous increase with decreasing temperature and at T = 3.5 K it reaches 34.1 J kg−1K−1 for a field change (ΔH) of 50 kOe. For the same ΔH the maximum values of ΔSM for R = Tb and Dy are 5.5 J kg−1K−1 and 8.5 J kg−1K−1 at 9.5 K and 4.5 K, respectively.

Role of nano and micron-sized inclusions on the oxygen controlled preform optimized infiltration growth processed YBCO superconductors

In the present work, with the aim of improving the local flux pinning at the unit cell level in the YBa2Cu3O7-δ (YBCO) bulk superconductors, 20wt% of nanoscale Sm2O3 and micron sized (Nd, Sm, Gd)2BaCuO5 secondary phase particles were added to YBCO and processed in oxygen controlled preform optimized infiltration growth process. Nano Dispersive Sol Casting method is employed to homogeneously distribute the nano Sm2O3 particles of 30–50nm without any agglomeration in the precursor powder. Microstructural investigations on doped samples show the chemical fluctuations as annuli cores in the 211 phase particles. The introduction of mixed rare earth elements at Y-site resulted in compositional fluctuations in the superconducting matrix. The associated lattice mismatch defects have provided flux pinning up to large magnetic fields. Magnetic field dependence of current density (Jc(H)) at different temperatures revealed that the dominant pinning mechanism is caused by spatial variations of critical temperatures, due to the spatial fluctuations in the matrix composition. As the number of rare earth elements increased in the YBCO, the peak field position in the scaling of the normalized pinning force density (Fp/Fp max) significantly gets shifted towards the higher fields. The curves of Jc(H) and Fp/Fp max at different temperatures clearly indicate the LRE substitution for LRE' or Ba-sites for δTc pinning.

Recovering Y and Eu from Waste Phosphors Using Chlorination Roasting—Water Leaching Process

Recovering Y and Eu from waste phosphors using chlorination roasting followed by a water leaching process was investigated in this study. Firstly, by chlorination roasting and water leaching, Y and Eu elements present in waste phosphors were efficiently extracted into a leach solution. Secondly, the majority of the impurities in the solution can be removed by adjusting the pH to 4.5 using a Na2S and NH3·H2O solution. Thirdly, the rare earths can be precipitated afterwards by adding a H2C2O4 solution and adjusting the pH to 2.0. Then rare earth oxides (REOs) can be obtained after calcining at 800 °C for 1 h. The characterization study of the waste phosphors and the rare earth oxide products was performed by XRD, XRF, and SEM-EDS analysis to determine the phase and morphological features. Influences of the factors, such as roasting temperatures and time, the addition of ammonium chloride on the roasting of waste phosphors, as well as the pH and the amount of oxalates on the precipitation of Y and Eu, were investigated. The maximum grade (99.84%) of mixed rare earth oxides and recovery rate (87.35%) of Y and Eu were obtained at the optimized conditions.

Limited infiltration due to reactive sintering of nano-Sm2O3 with preforms—its effect on (Y, Sm)Ba2Cu3O7−δ superconductors

Preform optimized infiltration growth process (POIGP) is employed to fabricate mixed rare earth (Y, Sm)Ba2Cu3O7−δ superconductors of high performance. POIGP creates wide range of pinning centres and also enables nano-particle additions to stable Y2BaCuO5 (Y-211) preforms. Nano-Sm2O3 particles (30–50 nm) were introduced in 0, 10, 20 and 30 wt.%, homogenously and without agglomeration, into the Y-211 preforms and the corresponding composites YBCO-Ar, YSm-10, YSm-20 and YSm-30 are fabricated. Though all the samples were processed in argon atmosphere to suppress the formation of solid solutions with Sm at Ba site, the effort was successful only in the YSm-20 sample, as seen from sharp diamagnetic transition and XRD studies. Magnetic property measurements were carried out on samples which showed strong (00l) texture, but were not necessarily single crystalline since no seed was used in the experiments. The calculated critical current densities (Jc) are thus reflective of the values in the basal plane, in the most favourable direction. The final composites revealed YSm-20 to exhibit better Jc with substantial flux pinning up to 9 T, at 77 K. Detailed examination of microstructures and field dependence of Jc reveal that the addition of nano-particles is not always rewarding and can lead to reactive sintering of Y-211 and limit the extent of liquid phase inflow into preforms. This not only can lead to incomplete reaction leaving larger 211 particles in the matrix, but can also shift the composition of liquid phase such that it promotes the formation of undesired solid solutions in IG processed REBCO as seen in YSm-30. The effect of various factors like open porosity in the preform, the ease of liquid phase infiltration and the liquid phase composition on the residual 211 size in the composites, suppression of RE/Ba solid solutions, and the resultant Jc versus H curves is discussed.