Valuable Rare Earth Research Articles

D2EHPA is a potential extractant for extraction of europium and samarium from chloride medium

Europium and samarium, the most valuable rare earth metals are broadly used in different areas such as fluorescent, medical materials and samarium-cobalt permanent magnet in the industrial community. Solvent extraction is an extensively applied separation process for collection of high purity rare earth metal ions. Due to the congruent physical and chemical properties of rare earth metal ions, the separation of specific elements from the mixture is ambiguous. In such places solvent extraction process is most efficient because of their ease in terms of the equipment and conditions associated with them. Solvent extraction, using di-2-ethylhexylphosphoric acid (D2EHPA) is the most frequently used industrial extractant for the extraction and separation of rare earth metal ions compared with other extractants. Present report deal with the studies on solvent extraction of europium (III) and samarium (III) from chloride medium using D2EHPA diluted in kerosene. Utmost extraction such as 96.65% Eu(III) and 86% Sm(III) happened at 0.001 mol/L hydrogen ion concentration in the aqueous medium. 100% extraction of Eu (III) and Sm(III) has been noticed with 0.07 mol/L and 0.08 mol/L D2EHPA, respectively. The separation factors of Eu/Co and Sm/Co are 1844.44 and 1556, respectively.

Selective Removal of Iron from Acid Leachate of Red Mud by Aliquat 336

Extraction of valuable rare-earth elements (REEs) from red mud is important for both resource recovery and waste treatment of red mud. However, the Fe present in red mud makes the extraction of REEs unsatisfactory, because Fe(III) is co-extracted and is difficult to remove. In this study, the feasibility and mechanism of selective removal of Fe from the acid leachate of red mud using Aliquat 336 were investigated. According to the theoretical calculation, Fe(III) mainly existed as FeCl3 species in a wide range of chloride concentrations, and the concentration of FeCl4− species significantly increased with chloride concentration. The extraction studies show that the chloride concentration strongly affects the extraction of Fe. The Fe removal efficiency is > 98% when the chloride concentration is 2.65 mol L−1, while the loss of REEs is 90% under the optimal conditions.

Analyzing the Rare Earth Elements (REEs) and Trace Metals in Tailings

In the process of producing bitumen from oil sand, a by-product called tailings is produced. Tailings are a mixture of clay, fine particles, water, solvent and residual bitumen. The industry’s current approach is to leave them in tailings ponds; however, that may cause environmental impacts to the ecosystems around them due in part to the toxic trace metals found in them. Research has shown that there are also valuable rare Earth elements (REEs) present in tailings. REEs found in tailings include Cerium, Neodymium, Lanthanum etc. Iron, Titanium, and Zirconium are not considered REEs but are still valuable enough to be extracted. The objective of this research was to determine the concentration of REEs and trace metals in bitumen froth treatment tailings (FTT). Our research team used acid digestion and inductively coupled plasma mass spectroscopy (ICP-MS) to measure the concentration of REEs and trace metals in several samples of FTT ash. We learned that Cerium was the most prevalent REE in tailings samples (>1000ppm), followed by Neodymium and Lanthanum. Zirconium was the most prevalent trace metal found in this tailings sample (>1000ppm), followed closely by Vanadium. Knowing the exact concentration of harmful trace metals in tailings will allow us to determine the extent of tailings ponds environmental effect and toxicity. Collecting and selling expensive metals found in tailings could be the start of a new precious metals economy in Alberta, which would provide new investment opportunities and jobs. This would also encourage corporations to invest in finding new ways to extract these precious metals, resulting in more purified tailings and less tailings overall going into tailings ponds.

Recovery of rare earths from waste cathode ray tube (CRT) phosphor powder by selective sulfation roasting and water leaching

Until recently, most displays, such as television and computer screens, were based on cathode ray tubes (CRTs). With the introduction of new types of displays including liquid crystal displays, CRTs have been widely replaced, leading to a gradual build-up of hazardous CRT powder waste. In this paper, a new approach is introduced where the valuable rare-earth elements (REEs) (i.e. yttrium and europium) in the powder are selectively recovered, leaving behind a zinc-rich residue and glass for further recycling. The main rare-earth compound in the waste powder is Y2O2S:Eu3+ (YOS). The fine-grained CRT powder was mixed with zinc sulfate monohydrate (ZnSO4·H2O) and roasted at 600–900 °C for short periods of time. In this way, Y2O2S:Eu3+ was transformed into water-soluble rare-earth sulfates. Meanwhile, ZnS underwent a two-stage reaction with ZnSO4·H2O, where first a partially water-soluble intermediate (ZnO·2ZnSO4) and then the water-insoluble ZnO was formed. Addition of a sufficient amount of ZnSO4·H2O ensured the recovery of ≥95% of the rare earths in a subsequent water leaching step, but there was also co-dissolution of about 5% of the total amount of zinc present. Several purification methods were tested and compared to separate the REEs from the zinc impurity in the solutions. In addition to the conventional precipitation methods with sulfides and oxalic acid, a novel liquid-liquid exchange reaction between REE-containing leachate and zinc-loaded Versatic Acid 10 was tested. Finally, a complete flow sheet is proposed for the (almost complete) valorization of REEs as well as the total zinc present.

Recovery of sulphuric acid and added value metals (Zn, Cu and rare earths) from acidic mine waters using nanofiltration membranes

Acidic mine waters (AMWs) contain, in addition to moderate concentrations of sulphuric acid, relatively high concentrations of transition elements (e.g. Fe, Al, Cu, Zn) and, in some cases, minor amounts of valuable rare earth elements (REEs). The established management routes for AMWs, based on the neutralisation and metal stabilisation as hydroxides, are limited by the associated costs, such as reagent consumption. Nanofiltration (NF)-based treatment processes could improve these management routes by recovering the sulphuric acid and simultaneously increasing the concentration of valuable elements (e.g. Zn, Cu and REEs) for further valorisation after the proper removal of Fe. Three different types of NF membranes with (a) a poly(piperazinamide) active layer (NF270), (b) a double active layer (poly(piperazinamide)/proprietary polyamide) (Desal DL) and (c) a sulphonated poly(ethersulphone) active layer (HydraCoRe 70pHT) were evaluated. The influence of Fe(III) concentration on the sulphuric acid recovery from solutions at pH 1 was characterised. NF270 showed the higher permeate fluxes and the higher heavy and REE metal rejections (i.e. the higher concentration factors). As the Fe(III) concentration increased, higher acid permeation was obtained, which helped to decrease the neutralisation costs during its post-treatment. The membrane chemistry of the active layer (nature and acid-base membrane properties) and structure (single/double layer) were found to be strong parameters in the membrane separation performance. Ion transport data were modelled according to a Solution-Electro-Diffusion model coupled with Ion Reactive Transport and the membrane permeances to ions were determined.

Abrasive-free surface finishing of glass using a Ce film

A novel form of abrasive-free polishing is described, using Ce film deposited on a polishing pad by vacuum evaporation. Polishing using metallic films other than Ce, such as Al and Cu, generates defects on the glass surface with almost negligible material removal rates (MRRs), whereas Ce film with deionized (DI) water achieves smooth, scratch-free surfaces with noticeable MRR. If DI water is not supplied to the pad, there is significant deterioration in polishing performance. MRR increases with greater thickness of Ce film, and extremely smooth surface with sub-nanometer roughness is achieved using Ce film of thickness 2.5 μm. Polishing performance is dependent on conditions such as pad rotation rate and polishing pressure. By adding potassium hydroxide (KOH) to the polishing solution, the MRR almost matches that obtained with conventional abrasive polishing, but achieves ultra-smooth surface finish (Ra: 0.388 nm). The polishing method presented here uses approximately 94% less Ce compared with conventional abrasive polishing, thereby dramatically reducing consumption of this valuable rare earth element.

PRELIMINARY STUDY ON SEPARATION OF RARE EARTH METALS FROM LEACH SOLUTION OF DISCARDED FLUORESCENT POWDER BY SOLVENT EXTRACTION

Discarded fluorescent lamps were considered as hazardous waste in Vietnam (code is 160106). However, its composition contained valuable rare earth metals, which can be recycled and recovered by leaching and solvent extraction processes. The present study sought to define the conditions of separation for rare earth elementals (REEs) from acid leach solution by solvent extraction using PC88A. The acid leach solution was obtained from leaching of fluorescent powder. Efficiencies on REEs extractions as functions of pH levels, extractant concentration, O/A ratio, metal concentration were investigated. For pH values greater than 0.0 and less than 1.0, the orders of the yields extraction were determined: yttrium > terbium > europium > aluminum and calcium. The best separation circuit included four-stage counter current extraction for yttrium separation with 20 %v/v PC88A in kerosene (O/A = 1/1, room temperature, 20 min of contact, pH of 0.38) and stripping step with 3 M HCl acid (O/A = 1/1, room temperature, 30 min of contact). After yttrium separation, the leach solution was extracted at pH of 0.98 in the same other conditions with two-stage counter current extraction to recover terbium and europium group. The final recovery from leach liquor was higher than 98 % and the grade of the final product was 94.2 % (for yttrium) and 93.8 % (for terbium and europium group).

Rare-earth recovery

Cover story The U.S. coal industry is facing tough times. Demand for coal is dwindling, and the industry is under fire for polluting streams and rivers with coal ash and acid mine drainage. But in that waste, and in some cases in the coal itself, are valuable rare-earth elements that may be readily recovered. If researchers can figure out how to extract them economically, sales of rare earths could help pay for some of the cleanup costs now borne by the coal industry and several coal-mining states. Demand for rare-earth elements, which include the lanthanides plus scandium and yttrium, has ticked upward over the past few decades. The long list of high-tech products that rely on rare earths include cell phones, flat-screen TVs, electric cars, wind turbines, satellites, defense aircraft, and high-performance magnets. In 2015, global demand for rare-earth elements was 149,000 metric tons per year, according to Mary Anne

Mesoporous SiO2 Nanoparticles: A Unique Platform Enabling Sensitive Detection of Rare Earth Ions with Smartphone Camera

Fast and sensitive detection of dilute rare earth species still represents a challenge for an on-site survey of new resources and evaluation of the economic value. In this work, a robust and low-cost protocol has been developed to analyze the concentration of rare earth ions using a smartphone camera. The success of this protocol relies on mesoporous silica nanoparticles (MSNs) with large-area negatively charged surfaces, on which the rare earth cations (e.g., Eu3+) are efficiently adsorbed through electrostatic attraction to enable a “concentrating effect”. The initial adsorption rate is as fast as 4025 mg (g min)−1, and the adsorption capacity of Eu3+ ions in the MSNs is as high as 4730 mg g−1 (equivalent to ~ 41.2 M) at 70 °C. The concentrated Eu3+ ions in the MSNs can form a complex with a light sensitizer of 1,10-phenanthroline to significantly enhance the characteristic red emission of Eu3+ ions due to an “antenna effect” that relies on the efficient energy transfer from the light sensitizer to the Eu3+ ions. The positive synergy of “concentrating effect” and “antenna effect” in the MSNs enables the analysis of rare earth ions in a wide dynamic range and with a detection limit down to ~ 80 nM even using a smartphone camera. Our results highlight the promise of the protocol in fieldwork for exploring valuable rare earth resources.

Treatment of monazite by organic acids II: Rare earth dissolution and recovery

In the present study, the second stage of a sequential extraction method of rare earths from monazite is discussed. The high cost and environmental impact of the conventional extraction processes of rare earth elements (REEs) have driven the investigation of alternate treatment techniques. The first paper of this series detailed the solution conversion of rare earth phosphate in monazite to an oxalate salt. This was achieved via an oxalic acid leach that removed the phosphate ion from the matrix.To determine the ability of leaching to release REEs from this residue, various other organic acids (citric, tartaric, acetic, lactic, crotonic, formic, maleic, gluconic, levulinic, mandelic and EDTA) were tested as lixiviants. An alkaline EDTA solution, which reported the strongest ability to extract REEs, was tested further to maximise recovery. A maximum single-pass extraction of >60% of the Nd (the most valuable REE in this material) was achieved in just 5 min at pH 10 and ambient temperature. >40% extraction of Ce and La was also obtained, with minimal proportions of phosphorus and iron released into solution. Where multiple passes of both leach stages were performed, greater extraction of all REEs was achieved. It is apparent that REE dissolution in this system is limited by the degree of conversion achieved in the first stage.In an industrial context, the results achieved at a laboratory scale show the potential of this system to be developed into an alternative to conventional processing. The PLS generated contains far lower impurity levels than conventional processes and there is the potential for a degree of selectivity between REEs prior to separation. This system thus represents a possible reduction in technical complexity and energy requirement as well as both environmental and safety issues in comparison to conventional technologies. The ability to produce a REE hydroxide also allows it to replace conventional extraction while still employing the same separation technology.

Electro-Membrane Technology for Extraction of Valuable Compounds and Rare Earth Elements from the Red Mud

The paper is devoted to the developed technology of treatment of red mud, a dangerous waste formed in the process of production of aluminum from bauxite ores by the Bayer process. The technology was examined on the samples of red mud from Russia and Iran aluminum plants. Detailed description of the process is presented. The chemical analysis data before and after the treatment are presented. It is shown that the new technology based on the use of electro-membrane apparatuses makes possible to neutralize the hazardous red mud with separate production of valuable compounds including rare earth metals. Several schemes of the process are presented.

From fly ash waste slurry to functional adsorbent for valuable rare earth ion separation: An ingenious combination process involving modification, dewatering and grafting

Acid extracting aluminum from fly ash would produce pestilent secondary fly ash slurry with strong acidity, high content of Cl− and residual Al3+ that is difficult to be further used. In order to achieve the zero emission, a potential integrated treatment process for reutilization was proposed in this paper. By intelligent use of residual Al3+ in sludge as catalyst, hydrophobic modification of solid particle was taken with fatty acid via a heterogeneous esterification at normal temperature. Due to the solvophobic force, moisture content of its filter cake was 36.46%, which reduced 11.14% compared with the unmodified one, hydrophobicity scale can achieve 100% with modifier accounting for only 0.8% of solid content and the Cl− concentrations decreased from 20 to 0.102 g/L in wash liquor, thus greatly saving water for washing and energy for drying. Subsequently, based on the appearance of hydrocarbon chains on particle surface, a high-efficiency ultraviolet-induced grafting polymerization was implemented to fabricate density polyacrylic acid decorated fly ash particles from the surface “CH” sites, the resultant composite was proved to efficiently separate valuable rare-earth Gd3+ from wastewater with outstanding adsorption and regeneration performance, hence bringing high added-value utilization for these hazardous waste.

Efficient and Selective Recovery of Trace Scandium by Inorganic Titanium Phosphate Ion-Exchangers from Leachates of Waste Bauxite Residue

Bauxite residue (BR) is an inevitable industrial waste generated through the classic Bayer extraction of alumina from bauxite minerals. It contains relatively significant amount of valuable rare earth elements, including scandium, and therefore, we explored the suitability of trace scandium recovery from BR acid leachate by titanium phosphate (TiP) ion exchangers. Three kinds of TiP materials (amorphous TiP, α-TiP, and γ-TiP) were synthesized through fluorine-free precursors and characterized by chemical analysis, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR), ultraviolet/visible (UV/vis) diffuse reflectance spectrometry, 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and potentiometric titration. The Sc3+ exchange capacities were determined as 1.74, 0.55, and 0.22 mequiv g–1 for amorphous, α-, and γ-TiP, respectively. Competition of major elements (Fe, Al, Ca) in BR leachate with Sc upta...

Synthesis of carboxylic acid functionalized diatomite with a micro-villous surface via UV-induced graft polymerization and its adsorption properties for Lanthanum(III) ions

Abstract To develop a high efficiency absorbent for separating and recovering valuable rare earth ions from wastewater, a new carboxylic acid functionalized diatomite (denoted as DGA) was prepared by grafting the polyacrylic acid (PAA) chains on the surface of diatomite via surface-initiated polymerization under UV irradiation. On a micro level, it can be observed a uniform micro-villous layer obviously on DGA surface due to that a mild grafting was achieved, so the composite can maintain the morphology and strength of the substrate to the greatest extent. The introduction of abundant carboxylic acid on the surface of diatomite can contribute to an enhanced adsorption performance for rare earth ions. In order to investigate the adsorption performance of DGA, La 3+ was chosen as the model adsorbate, factors influencing La 3+ adsorption efficiency of DGA were systemically investigated, such as pH, ionic strength, contact time, and the initial concentration of La 3+ . Under optimized condition, the saturated adsorption amount could reach to 139.5 mg/g. Moreover, La 3+ adsorption shows a rapid process, especially, at an initial La 3+ concentration of 20 mg/L, the time to reach equilibrium was as short as 20 min. Adsorption kinetic as well as equilibrium isotherm was also evaluated. Results of regeneration experiments show that DGA can keep above 90% adsorption capacity and desorption rate in the eight consecutive cycles. The study suggests that the DGA is a promising adsorbent for removal of REE ions from aqueous solution.

Beneficiation of the Nechalacho rare earth deposit. Part 2: Characterisation of products from gravity and magnetic separation

The application of mineral beneficiation techniques to valuable rare earth element (REE) bearing minerals requires a significant amount of research. A previous paper (Jordens et al., 2016) described a series of physical separation processes employed to pre-concentrate rare earth minerals (REM) and reject iron oxide minerals from the Nechalacho Deposit. In addition to grade and recovery information it is important to understand the performance of these separations from a mineralogical perspective. Information on liberation, mineral associations, magnetic properties and size-by-size recoveries can be used to further improve process designs for this deposit.This work employs automated mineralogy (QEMSCAN), scanning electron microscopy and a vibrating sample magnetometer to characterise the products from laboratory gravity separation (Knelson and Falcon centrifugal concentrators) and magnetic separation (varying intensity wet drum magnetic separators). The information gathered is then used to identify the optimum fraction for downstream flotation separation. The selected flowsheet included a Knelson centrifugal concentrator and low intensity drum magnetic separation resulting in a total rare earth oxide (TREO) recovery of 11.75% and a TREO grade of 7.50%.

Lanthanide-Dependent Regulation of Methanol Oxidation Systems in Methylobacterium extorquens AM1 and Their Contribution to Methanol Growth.

Methylobacterium extorquens AM1 has two distinct types of methanol dehydrogenase (MeDH) enzymes that catalyze the oxidation of methanol to formaldehyde. MxaFI-MeDH requires pyrroloquinoline quinone (PQQ) and Ca in its active site, while XoxF-MeDH requires PQQ and lanthanides, such as Ce and La. Using MeDH mutant strains to conduct growth analysis and MeDH activity assays, we demonstrate that M. extorquens AM1 has at least one additional lanthanide-dependent methanol oxidation system contributing to methanol growth. Additionally, the abilities of different lanthanides to support growth were tested and strongly suggest that both XoxF and the unknown methanol oxidation system are able to use La, Ce, Pr, Nd, and, to some extent, Sm. Further, growth analysis using increasing La concentrations showed that maximum growth rate and yield were achieved at and above 1 μM La, while concentrations as low as 2.5 nM allowed growth at a reduced rate. Contrary to published data, we show that addition of exogenous lanthanides results in differential expression from the xox1 and mxa promoters, upregulating genes in the xox1 operon and repressing genes in the mxa operon. Using transcriptional reporter fusions, intermediate expression from both the mxa and xox1 promoters was detected when 50 to 100 nM La was added to the growth medium, suggesting that a condition may exist under which M. extorquens AM1 is able to utilize both enzymes simultaneously. Together, these results suggest that M. extorquens AM1 actively senses and responds to lanthanide availability, preferentially utilizing the lanthanide-dependent MeDHs when possible. The biological role of lanthanides is a nascent field of study with tremendous potential to impact many areas in biology. Our studies demonstrate that there is at least one additional lanthanide-dependent methanol oxidation system, distinct from the MxaFI and XoxF MeDHs, that may aid in classifying additional environmental organisms as methylotrophs. Further, our data suggest that M. extorquens AM1 has a mechanism to regulate which MeDH is transcribed, depending on the presence or absence of lanthanides. While the mechanism controlling differential regulation is not yet understood, further research into how methylotrophs obtain and use lanthanides will facilitate their cultivation in the laboratory and their use as a biomining and biorecycling strategy for recovery of these commercially valuable rare-earth elements.

Особенности обоснования параметров кондиций рентабельного извлечения ценных редкоземельных составляющих многокомпонентного минерального сырья

Особенности обоснования параметров кондиций рентабельного извлечения ценных редкоземельных составляющих многокомпонентного минерального сырья

Process optimization and kinetics for leaching of rare earth metals from the spent Ni–metal hydride batteries

Nickel–metal hydride batteries (Ni–MH) contain not only the base metals, but valuable rare earth metals (REMs) viz. La, Sm, Nd, Pr and Ce as well. In view of the importance of resource recycling and assured supply of the contained metals in such wastes, the present study has focussed on the leaching of the rare earth metals from the spent Ni–MH batteries. The conditions for the leaching of REMs from the spent batteries were optimized as: 2M H2SO4, 348K temperature and 120min of time at a pulp density (PD) of 100g/L. Under this condition, the leaching of 98.1% Nd, 98.4% Sm, 95.5% Pr and 89.4% Ce was achieved. Besides the rare earth metals, more than 90% of base metals (Ni, Co, Mn and Zn) were also leached out in this condition. Kinetic data for the dissolution of all the rare earth metals showed the best fit to the chemical control shrinking core model. The leaching of metals followed the mechanism involving the chemical reaction proceeding on the surface of particles by the lixiviant, which was corroborated by the XRD phase analysis and SEM–EDS studies. The activation energy of 7.6, 6.3, 11.3 and 13.5kJ/mol was acquired for the leaching of neodymium, samarium, praseodymium and cerium, respectively in the temperature range 305–348K. From the leach liquor, the mixed rare earth metals were precipitated at pH∼1.8 and the precipitated REMs was analyzed by XRD and SEM studies to determine the phases and the morphological features.

Recovery of rare earth elements from permanent magnet scraps by pyrometallurgical process

In order to recover valuable rare earth elements from Nd–Fe–B permanent magnet scraps, a high-temperature pyrometallurgical process was developed in this work. The magnet scraps were first pulverized and oxidized at 1000 °C in normal atmosphere. The oxidized mixtures were then selectively reduced by carbon in the temperature range of 1400–1550 °C. In this way, the rare earth elements were extracted to the form of oxides, whereas Fe and B were separated to metal phase. For improving the purity of rare earth oxides, the effects of temperature and reaction time on the reduction of B2O3 in oxide phase were investigated. It is found that increasing reaction temperature and extending reaction time will help the reduction of B2O3 contents in rare earth oxide phase. Almost all rare earth elements can be enriched in the oxide phase with the highest purity of 95 %.

Fungus Sequesters Industrially Valuable Rare-Earth Elements

A newly identified fungal species, isolated from an abandoned mine, can concentrate dysprosium and other industrially valuable rare-earth elements—making this fungus potentially useful for recovering such materials, according to Takumi Horiike and Mitsuo Yamashita at Shibaura Institute of Technology in Saitama, Japan. This fungus, which they are calling Penidiella sp. T9, appears to be the first microorganism known to recover rare-earth elements during cell growth, they report. Details appeared 1 May 2015 in Applied Environmental Microbiology (doi:10.1128/AEM.00300–15).