Extraction Of Lanthanides Research Articles

Metabolic flux modeling of Gluconobacter oxydans enables improved production of bioleaching organic acids

Bioleaching with organic acids is an option for recovery of rare earth elements (REE) and or other valuable metals from consumer or industrial wastes. Biohydrometallurgy can play an economically and environmentally sustainable role in REE recycling, particularly if agriculture or food wastes are used as the carbon substrates for production of the bioleaching agents. A challenge for organic acid based REE bioleaching is the incomplete conversion of the carbon substrate to an optimal organic acid mixture with high REE extraction capability. To help meet this challenge a metabolic flux model was developed for Gluconobacter oxydans to identify options for improving sugar conversion to chelating organic acids. Model predictions were consistent with laboratory data for the microbial consumption of glucose and production of gluconic acid and suggested that providing growth conditions with relatively high carbon to nitrogen molar ratios could result in production of lower pH biolixiviant and thus improve REE bioleaching yields.

Molten salt electrolysis and room temperature ionic liquid electrochemical processes for refining rare earth metals: Environmental and economic performance comparison

Circularizing end of life products such as electronic waste can open a new source for rare earth elements (REEs) that will decrease the demand pressure on conventional virgin production. The last step to produce REEs consists of a refining process to convert rare earth oxide (REO) to REE metal. One promising technology is processing REO via a room temperature ionic liquid, which is characterized by low energy requirements in contrast to existing REEs extraction processes. In this work, life cycle and techno-economic assessments are performed and compared against molten salt electrolysis. The results show that both processes have advantages and disadvantages in terms of environmental performance, and that they are similarly competitive in terms of economic performance. A breakeven analysis suggests that future research should focus on coupling the production of REOs with the refining processes to attempt to lower REO cost and make them economically feasible in the U.S.

Extraction of rare earth elements from a South American ionic clay

Ionic clays, formed by the natural weathering of REE-bearing minerals and the adsorption of the resulting liberated REE ions onto the clay surface, are an important resource for critical rare earth elements (REEs). Here, a two-step desorption process using ammonium sulfate with active pH adjustment using sulfuric acid was developed to extract REEs from a South American clay. The desorption process was optimized using response surface methodology approach and the optimum operating conditions were determined to be 0.15 mol/L ammonium sulfate, pH 3, liquid to solid ratio of 3/1, and 25 °C with 20 min residence time. It is shown that this ionic clay is significantly different from previously reported clays, e.g., from southern China, as it consists of three modes of REEs, including ion-exchanged REEs physically adsorbed on the clay surface, hydrolyzed REEs chemically adsorbed on the clay surface, and mineralized (non-desorbable) REEs within the clay. Mechanistic investigations through progressive acidification during desorption and adsorption isotherms show that REE desorption/adsorption occurs due to the combined action of physical ion exchange adsorption and surface complexation chemical adsorption, with their relative importance depending on the pH of the system and the amount of sulfate anions present within the solution. This work supports overall efforts to utilize ionic clays as a relatively new resource for REEs to empower the development and adoption of modern green technologies such as wind turbines and electric vehicles.

Competitive extraction and stripping behaviors of rare earth elements from industrial wet-process phosphoric acid using di-(2-ethyl-hexyl) phosphoric acid solvent: Optimization and thermodynamic studies

Rare earth elements (REEs) have gained a great amount of attention in the last decades, as they become indispensable and ubiquitous owing to their versatile applications in modern world and high technologies. The main aim of this work is to study the extraction behavior of REEs from the wet process phosphoric acid (WPPA) using Di-(2-ethylhexyl) phosphoric acid (D2EHPA) with a focus on yttrium (Y) and scandium (Sc) as the major REEs. The extraction and stripping operating conditions of REEs from WPPA were optimized, including the extractant concentration, the O:A ratio (organic phase / aqueous phase), the contact time, the residence time and stirring speed. Single-stage extraction results revealed an extraction efficiency of 58 and 56 % for ΣREEs and Sc, respectively.Besides, it was demonstrated that D2EHPA shows a high affinity towards yttrium (Y) with high extraction of 91 % under the optimized conditions of 2 M of D2EHPA, O:A = 1, 600 rpm during 20 min. The McCabe–Thiele diagrams were established to specify the required theoretical number of extraction stages of ΣREEs. It was revealed that four stages are required for ΣREEs extraction, two stages for Sc and a single extraction stage for Y at an O:A ratio of 1. The best extraction efficiencies were obtained for a total percentage of 97, 87 and 90 % for ΣREEs, Sc and Y, respectively. The stripping was successfully achieved using H2SO4 solution with efficiencies of 73 and 90 % for ΣREEs and Y, respectively. Finally, an integrated process for the recovery of REEs from WPPA was proposed.

From Ashes to Riches: Microscale Phenomena Controlling Rare Earths Recovery from Coal Fly Ash.

Coal fly ash is an alternative source of rare earth elements (REEs), which are critical in modern energy and electronic technologies. Current hydrometallurgical processes, however, yield variable recovery rates because of the limited understanding of the microscale phenomena controlling the extraction of REEs from fly ash. This work investigates the microscale processes that dictate the recovery of REEs from ash particulates via a spatiochemical analysis. We find that REE-bearing minerals are hosted in three modes with distinct recovery mechanisms: (i) REEs encapsulated in dense particles are recovered via the cation exchange between matrix metals (Al, Ca, Mg, etc.) and solution cations, (ii) REEs within permeable particles are recovered via intraparticle pore-scale fluid flow, and (iii) discrete and surface-bound REE-bearing minerals are recovered via direct exposure to reagents. The role of metal content and the limiting transport mechanisms are further probed for dense particles, the predominant mode of occurrence. This study highlights, for the first time, how the morphology and the elemental makeup of the ash matrix play a critical role in the accessibility of REEs, furthering the knowledge base required for the design of cost-effective and environmentally benign REEs recovery techniques.

Insights into the Third Phase Formation Behaviour of N,N‐Didodecyl‐N’,N’‐Dioctyl Diglycolamide in n‐Dodecane Investigated by Dynamic Light Scattering and FTIR Spectroscopy

AbstractN,N‐didodecyl‐N’,N’‐dioctyl diglycolamide (D3DODGA) was regarded as a promising ligand for the extraction of trivalent lanthanides and actinides from nuclear waste, owing to the absence of undesirable third phase formation during liquid‐liquid extraction. However, the reason for the absence of third phase formation in D3DODGA as compared to other diglycolamides was not known. To unravel the absence of third phase formation, the extraction behaviour of nitric acid and Nd(III) in 0.2 M D3DODGA in n‐dodecane (n‐DD) was studied and the reverse micellar aggregation behaviour of the organic phase was probed by dynamic light scattering (DLS) and FTIR spectroscopy. The results were compared with those obtained in popular ligands abbreviated as TODGA, TEHDGA and TDdDGA in n‐dodecane under similar conditions. The limiting reverse micellar aggregate size for third phase formation was determined to be 11.6 nm at the limiting nitric acid concentration of 0.54 M in organic phase. The investigations revealed that the absence of third phase in D3DODGA and TDdDGA was due to the presence of long chain dodecyl group attached to the molecule, as compared to the octyl moiety present in TODGA and TEHDGA. As a result, it was possible to load higher concentration of nitric acid or Nd(III) in D3DODGA without the problem of third phase formation. In view of this, the D3DODGA in n‐DD can be employed efficiently for the separation of trivalent actinides and lanthanides from nuclear waste.

Selective extraction of rare earth elements from red mud using oxalic and sulfuric acids

Red mud is an alkaline industrial solid waste discharged from alumina production via the Bayer process and can be considered a kind of potential resource of rare earth elements (REEs). Many valuable metals such as iron, aluminum, and titanium also exist in red mud. A multi-stage extraction method was proposed in this study by taking full account of the REEs’ occurrence in red mud. Firstly, the pretreatments of oxalic acid leaching, roasting, and dilute hydrochloric acid leaching were employed to recover iron and enrich REEs in the residue. Subsequently, sulfuric acid leaching was used to selectively dissolve REEs into the leaching solution. Finally, the effects of sulfuric acid concentration, liquid-solid ratio, reaction temperature, and reaction time on the leaching efficiency of REEs were then investigated. The results show that the maximum extraction of the REEs reached 80 % and less than 4 % of Fe, Na, Ca, Ti and Al were extracted under the experimental conditions of 1 mol/L H2SO4, 3 h, 95 °C, and the liquid-solid ratio of 5:1 mL/g. The practicable approach by multi-stage extraction of acid leaching and roasting can split iron and REEs from red mud.

Ammonium sulfate leaching of NaOH-treated monazite

Rare earth elements (REEs) can be extracted from monazite under aggressive decomposition and leaching conditions. Much of the waste rocks are removed prior to the extraction process to minimize the costs and waste generation, which is difficult with coal byproducts. The possibility of extracting REEs from low-grade monazite concentrates under relatively mild conditions has been explored to simulate the extraction of REEs from coal byproducts.It has been found that monazite can be decomposed in 10 to 50 % NaOH solutions at 80 °C, with the resulting hydrous oxide being subjected to the ammonium sulfate leaching at pH 4. The ς-potential measurements conducted in the presence of the lixiviant suggest that the NH4+ ions displace the hydrated Ln3+ ions from the surface of Ln(OH)3(s) by an ion-exchange mechanism, which may be driven by the large differences in the hydration enthalpies between the charged species involved. This approach may be advantageous over acid leaching, including the regeneration of spent lixiviant, lower chemical consumption, and leaching at higher pH.

Theoretical Insights into Phenanthroline-Based Ligands toward the Separation of Am(III)/Eu(III).

The bistriazinyl-phenanthroline representative ligand, BTPhen, shows excellent extraction and separation ability for trivalent actinides and lanthanides. Herein, we first designed three phenanthroline-based nitrogen-donor ligands (L1, L2, and L3), and then studied the structural and bonding properties as well as thermodynamic properties of the probable complexes, ML(NO3)3 (M = Am or Eu and L = L1, L2, or L3), using scalar relativistic density functional theory. Our charge decomposition analysis revealed an obviously higher charge transfer from the ligand to Am(III) compared with the Eu(III) case for the studied complexes. Spin density analysis further showed a more significant degree of Am-to-ligand spin delocalization and the corresponding spin polarization on the ligands. According to the thermodynamic analysis, ligand L3 has the strongest complexation capacity for both Am(III) and Eu(III) ions, while ligand L1 has the highest Am(III)/Eu(III) selectivity in binary octanol/water solutions. We expected that this work can provide valuable theoretical support for the design of effective ligands for actinide(III)/lanthanide(III) separation in high level liquid waste.

Can bioleaching of NIB magnets be an answer to the criticality of rare earths? An ex-ante Life Cycle Assessment and Material Flow Cost Accounting

The instability of rare earth elements (REEs) supply chains due to, among others, geopolitical factors brought alternative sources of REEs under the spotlight. Waste from electrical and electronic equipment (WEEE) is considered one of such sources. WEEE recycling is seen as a way not only to mitigate the aforementioned REEs supply risk but also to benefit the environment and society caught currently in a precarious position. Within this context, bioleaching for REEs recovery is gaining attraction, considering that, so far, this process has mainly been used to recover other elements (e.g., Cu, Ni, Zn, Al, Au, Ag). Hitherto, a few lab-scale studies on Nd, Dy, and Pr bioleaching from NIB magnets were identified in the open literature, whereas only one study attempted to perform a simplified LCA analysis of the process. Ergo, this study aims at filling this knowledge gap. For this purpose, the Life Cycle Assessment (LCA) and Material Flow Cost Accounting (MFCA) were performed to assess the process' environmental and economic feasibility after scaling it up from a lab to a pilot scale. Moreover, a break-even analysis was performed to assess the competitiveness of the technology. As the bioleaching of NIB magnets is an emerging concept, this study aimed to identify future process optimisation and development directions. The process was divided into six stages (i.e., demagnetising, shredding, bacteria cultivation, bioleaching, REEs extraction, and oxidation), analysed individually and collectively. Electricity and oxalic acid consumption, together with investment costs, were identified as the main hotspots for future improvement. • Permanent NIB magnets can be recycled to recover rare earth elements. • Nd, Dy and Pr bioleaching from these magnets is a promising emerging technology. • Environmental and economic hotpots of this technology were identified. • Electric energy and oxalic acid consumption resulted environmentally impactful. • High investment costs might compromise the profitability of the process.

Using Nuclear Spectroscopy to Analyze and Adjust an Experiment on the Liquid–Liquid Extraction of Transplutonium and Rare-Earth Elements

Using Nuclear Spectroscopy to Analyze and Adjust an Experiment on the Liquid–Liquid Extraction of Transplutonium and Rare-Earth Elements

Phase equilibrium of the CaO–SiO2–Al2O3–Ce2O3 system: A basis for recovering REEs from RE-Containing slag

With the massive consumption of rare earth resources, the recovery of rare earth elements (REEs) from secondary resources has become a focus of attention. It is economically necessary to recover REEs from Bayan Obo RE-containing blast furnace slag (RE-BFS), which contains considerable REEs. However, due to the lack of relevant thermodynamic data, it is difficult to effectively recover REEs from RE-BFS. Therefore, the isothermal phase diagram of CaO–SiO2–Al2O3–Ce2O3 at 1100 °C was constructed in this work, according to the principle of phase diagram construction combined with the method of equilibrium experiments. The optimal rare earth equilibrium phase in this system was defined as Ce4.667-xCax(SiO4)3O1-0.5x. According to the actual composition of the RE-BFS, a dominant separation region of L + Ce4.667-xCax(SiO4)3O1-0.5x was obtained in the phase diagram. Subsequently, the extraction of REEs in the RE-BFS could be completed by solid–liquid separation, which allowed economic benefits without affecting the environment. The data reported in this work provide a theoretical basis for solving the problem of recovery from RE-containing secondary resources and developing high value-added materials.

Comparison of processing routes for recovery of rare earth elements from discarded fluorescent lamp phosphors

This study investigates two phosphor samples with three processing routes to extract rare earth elements (REE). Acid leaching in 2 M HCl, 80 °C, 1 h yielded higher REE extraction in the compact fluorescent lamp (CFL) feed (82% Eu), with varying rare earth (RE) purity (77–97%) compared to fluorescent tubelight (TL) feed (69% Eu, 98–95% purity). Mechanical activation (MA) of 30 and 60 min caused partial dissociation of the LAP (LaPO4:Ce3+Tb3+) phase and yielded 34% Ce, 36% Tb, and 40% La. Transmission electron microscopy results revealed the formation of polycrystalline sites, which improved RE recovery. Alkali baking showed better REE extraction for both phosphors. 86.5% Y, 69% Eu was selectively extracted in feed acid leaching, and 100% La, 60% Tb, 20.6% Eu after alkali baking with 97% purity and CeO2 in the leach residue. The acid baking route was preferred for CFL phosphor with 91% REE (43 % Tb) extraction and 98% purity. TL phosphor was better for Tb extraction. The alkali baking of TL feed and acid baking of CFL feed yields 37.7% and ∼30% rare earth oxides, respectively.

A review of thermodynamic data for lanthanum, iron, and thorium applied to rare earth extraction

A consolidated and revised database for thermodynamic simulation of lanthanum (representing the rare earth elements), iron, and thorium in water, sulfate, and phosphate systems was built. Thermodynamic parameters (∆Gf°, ∆Hf°, and Sf°) collected from the original sources were compared with those reported in thermochemical software databases. The inconsistencies found in the latter were mainly ascribed to typographical errors, incorrect unit conversions, and errors generated by combining data from different sources. The Eh-pH diagrams illustrate the significant effects of data discrepancies on the stability regions of aqueous and solid species. The results obtained with the revised database helped the identification of operating windows for the selective precipitation of common impurities (e.g., Fe and Th) in rare earth extraction. In the presence of sulfate, the complex LaSO4+(aq) is the only stable species up to pH = 8 and then La(OH)3(s) is formed. In phosphate solutions, lanthanum salts precipitate at lower pH. The precipitation pH varies with the nature and crystal features of the different lanthanum phosphate phases. Under oxidizing conditions, wide operational windows favor the selective precipitation of Fe2O3(s) or FePO4.2H2O(s) at pH 1–5. Thorium hydroxide is formed at pH 4. The inclusion of phosphate complexes in the simulation expands the thorium solubility region from pH 4 to 6.5 (approximately), depending on phosphate concentration.

Extraction of Actinides and Lanthanides from Nitric Acid Solutions with Polyphosphinylbenzenes

Extraction of Actinides and Lanthanides from Nitric Acid Solutions with Polyphosphinylbenzenes

Recovery and Separation of Dysprosium from Waste Neodymium Magnets through Cyphos IL 104 Extraction

In the present study, the extraction of rare earth elements (REEs) from waste neodymium magnets using phosphorus ionic liquid Cyphos IL 104 was investigated. The objective was to recover and separate the heavy REE (Dy) from light REEs (Nd and Pr). Therefore, the experimental parameters of ionic liquid extraction, including contacting time, the initial pH value, extractant concentration, and O/A ratio, have been optimized. The highest separation factor αDy/Nd of 45.18 and αDy/Pr of 47.93 has been achieved. Following the ionic liquid extraction, the comparison of different stripping agents and the stripping parameters (the concentration of stripping agent and A/O ratio) were also explored. In short terms, this research demonstrates the optimal parameters of Cyphos IL 104 for selectively extracting high REE (Dy) and reveals its potential for recovering and separating REEs in real waste.

Extraction of rare earth and cobalt from leach residue of Nd-Fe-B waste by reductive leaching with iron powder

After recovering rare earth from neodymium–iron–boron (Nd–Fe–B) magnet waste via oxidation roasting–hydrochloric acid leaching, extracting rare earths and cobalt from remaining leach residue, containing about 0.67% (w/w) RE and 0.36% Co, is environmentally and economically important. However, extracting valuable elements from low–grade minerals remains challenging. The purpose of this study is to accelerate the dissolution of rare earths and cobalt from leach residue of Nd–Fe–B waste (MWLR) under low acidity by adding iron as a reductant, which is conducive to destroying the main phase iron oxide. To optimize the leaching process of MWLR in a sulfuric acid system, the effects of reaction temperature, reaction time, sulfuric acid dosage, solid/liquid (S/L) ratio, reductant addition time and reductant dosage were investigated. Circa 87.9% Fe, 99.7% Co, 99.4% Nd, 73.2% Pr and 87.9% Ce were leached. Furthermore, kinetic results indicated that the leaching process, controlled by a combination of internal diffusion and surface chemical reaction, changed to a surface chemical reaction control in the presence of Fe added as the reductant. This research proposed and verified a way to extract low–grade rare earths and cobalt from MWLR, and investigated the mechanism of reductive leaching process.

Potential uses of phosphogypsum: A review

Phosphogypsum (PG) is a by-product of the phosphate fertilizer industry that is produced during the phosphoric acid production process. Annual global PG production ranges between 100 to 300 Mt, with only 15% of that utilized while the rest is usually placed on large dumps with potential serious human and environmental impacts. The aim of this study is to give an overview and to evaluate the existing and potential uses of PG that extend from soil stabilization to cement and chemical industry and for agricultural to geotechnical, human impacts, and environmental applications. More specifically, PG can be used as a substitute in the cement industry, in building materials and in road construction, as a fertilizer for soil improvement, as a raw material for the production of some chemicals, and as a backfilling material for the rehabilitation of abandoned mines and quarries, while the recovery of gypsum and the extraction of rare earth elements signifies the potential importance of PG to cyclic economy. The paper offers an extensive overview of existing and potential uses of PG, discusses their adequacy, and reveals that PG can be widely used under certain conditions, rather than disposed as waste in stockpiles.

Effective extraction of rare earth elements from coal slurry

ABSTRACT Rare earth elements (REEs) have been found in coal and coal by-products but occur in their lower contents and inside crystal structures of silica-alumina, leading their extraction challengeable. This study is regarding the pre-treatment of coal by-products, herein coal slurry, prior to the extraction of REEs. The alkali additives (specially sodium carbonate) were applied to pre-treat coal slurry under elevated temperatures for the destruction of crystal structures of silica-alumina in the coal slurry and the exposure of REEs for their further acid-extraction. Studies addressed effects of the alkali additive, mole ratio, calcination temperature, leaching pH, on the leaching efficiency of REEs and the acid consumption. Results indicated that the alkali calcination necessarily and significantly improved the efficiency of the following-up acid extraction of REEs from coal slurry, and the use of supercritical contributed for the pH adjustment and acid saving. The optimal procedure on REEs leaching from coal slurry was found to be sodium carbonate as alkali calcination additive, a molar ratio of coal-slurry/alkali at 1:1, a calcination temperature at 850°C, the supercritical CO2 and acid leaching at pH = 2, under which Under the optimal conditions, REEs extraction efficiency of all involved coal slurry achieved to be over 90%.

The Utmost Extraction of some individual rare earth elements from Monazite Mineral Acidic Leach Liquor by solvent and ion exchange techniques

The Utmost Extraction of some individual rare earth elements from Monazite Mineral Acidic Leach Liquor by solvent and ion exchange techniques