Extraction Of Lanthanides Research Articles

Analysis of enrichment, correlation, and leaching patterns of rare earth elements in coal fly ash assisted by statistical measures

Coal fly ash (CFA) is a typical industrial solid waste, which has recently been reported to contain rare earth elements (REEs). REEs are important materials in many industrial fields. Therefore, extracting REEs from CFA becomes a win-win strategy to both make full use of CFA and reclaim REEs. However, the stable crystalline structure of CFA is hard to break, which limits the extraction of REEs. The inter-correlation and the leaching patterns of the REEs in CFA also remain unclear. In this work, REEs were enriched by desilication, and the correlation and the influences of multiple acids of the leached REEs were investigated. It was found that desilication could increase the leachable amount of REEs from 137.37 ppm to 346.12 ppm. The light rare earth elements (LREEs) were less inter-correlated than heavy rare earth elements (HREEs) and desilication enhanced the leaching of LREEs more than that of HREEs. The ratio and type of the leaching acids both influenced the extraction of REEs from CFA: HCl and HF played important roles in the extraction from the untreated CFA while HNO3 and HF were more decisive for the desilicated CFA. In addition, we used statistical analysis to quantificationally confirm that desilication and acids both significantly influenced the extraction of REEs. This work provides evidence for the enrichment of REEs in CFA and acid choosing when leaching REEs from CFA.

Process development for the extraction of rare earth elements from an acid mine drainage treatment sludge

The study focused on developing a separation approach to recover REEs from AMD treatment sludge. Parametric leaching tests were first conducted, and optimum leaching conditions were determined as a pH value of 0.5 and a leaching time of 8 min. Stage-wise precipitation tests were then applied to illustrate the precipitation behaviors of various groups of elements at different pH regions. Test results indicate that selectively recovering individual REEs by targeting one particular pH region was not feasible. However, impurities, specifically iron and silicon, could be selectively removed from REEs at pH 3.5. Afterward, three different solvent extraction methodologies, including regular solvent extraction with DEHPA, solvent extraction with a phase modifier of TBP, and post-oxidation solvent extraction, were evaluated for enhanced rare earth oxide purity. As a result of the developed process, a mixed rare earth product with a purity of 80% by weight was produced from the AMD treatment sludge.

Extraction of rare earths from coal and coal by-products as a non-traditional source

Rare earth elements (REEs) are one of the critical metals used for modern technological applications and green technologies. Due to growing demand and limited availability, there is a huge supply risk associated with REEs. The primary resources of rare earths in India are limited and associated with many processing challenges. In this scenario, it is important and timely to explore the non-traditional sources of rare earths to meet the domestic demand of country in the future. India is rich in coal deposits. The studies are very limited and there is scarcity of the research work carried out on the extraction of rare earths from Indian coal and coal by-products. Therefore, the objective of the present research article is to highlight the presence of REEs in Indian coal along with coal by-products. The objective is to identify the sweet pots of rare earths in coal and coal by-products. The concentration of total REEs is in the range of 150–200 ppm in coal samples. Furthermore, coal ash contains the concentration of total REEs which is more than 600 ppm in the samples of study area. It is aimed to review the several methods to recover rare earths that can be economically applied for the extraction of rare earths from coal and its by-products. Column leaching experiments achieve a 50% recovery rate of REEs from coal, while thermal treatment of coal enhances the recovery rate by one and a half times compared to untreated samples. Process optimization experiments demonstrate the superiority of the flocculator jar test apparatus, resulting in a significant increase in REE recovery (52% from coal samples). It was found that there is a huge work is still needed to be done for the development of an energy efficient and economical recovery of rare earths from coal and its by-products.

Extraction of Rare Earth Elements from the Phosphate Concentrate of Apatite Processing

Extraction of Rare Earth Elements from the Phosphate Concentrate of Apatite Processing

Biomonitoring of rare earth elements in Southern Norway: Distribution, fractionation, and accumulation patterns in the marine bivalves Mytilus spp. and Tapes spp.

Growing extraction and usage of rare earth elements and yttrium (REY) for medical and industrial applications has resulted in increased discharges into the marine environment. Using Mytilus spp. Mussels and Tapes spp. clams as bioindicator organisms, we analyzed 15 REY in soft tissues of specimens collected at two potentially polluted sites in Southern Norway: in the vicinity of an industry producing gadolinium-based MRI contrast agents (GBCAs) (Lindesnes) and in an industrially-affected fjord (Porsgrunn). The spatial distribution of REY and shale-normalized fractionation patterns were determined to assess the potential anthropogenic contribution of REY at the sites. At both sites, the REY fractionation pattern in soft tissue was characterized by enrichment of light rare earth elements (LREE) over heavy rare earth elements (HREE), while also displaying negative cerium and small positive gadolinium (Gd) anomalies. LREEs contributed to over 80% of the total REY concentrations, with increasing relative enrichment following higher total REY. Gd anomalies remained conserved in most sites despite significant differences in total REY; however, a high Gd anomaly (Gd/Gd* = 4.4) was found downstream of the GBCA industry spillwater outlet, indicating biotic uptake of excess anthropogenic Gd at this site. Total REY concentrations in clams in Porsgrunn were one order of magnitude higher than in mussels in Lindesnes. This may be attributable to freshwater influences in Porsgrunn, where clams collected closer to the river mouth had significantly higher total REY concentrations. This study constitutes the first assessment of REY concentrations in marine bivalves in Norway and can provide useful information for future biomonitoring studies on REY contamination.

Features of Extraction of Rare-Earth Elements from Medicinal Plant Raw Materials Into Infusions and Decoctions

Features of Extraction of Rare-Earth Elements from Medicinal Plant Raw Materials Into Infusions and Decoctions

Advances in Analytical Techniques and Applications in Exploration, Mining, Extraction, and Metallurgical Studies of Rare Earth Elements

The use of analytical techniques is important and critical in all areas related to REE, such as basic fundamental research, exploration, mining, extraction, and metallurgical activities at different stages by different industries. At every stage of these activities, rock, ore, minerals, and other related materials have to be analyzed for their REE contents in terms of elemental, isotopic, and mineralogical concentrations using different analytical techniques. Spectacular developments have taken place in the area of analytical instrumentation during the last four decades, with some of them having shrunk in size and become handheld. Among laboratory-based techniques, F-AAS, GF-AAS, ICP-OES, and MP-AES have become very popular. Because of high sensitivity, fewer interference effects, and ease of use, ICP-MS techniques, such as quadrupole ICP-MS, ICP-MS/MS, ICP-TOF-MS, MH-ICP-MS, HR-ICP-MS, and MC-ICP-MS, with both solution nebulization as well as direct solid analysis using laser ablation sample introduction methods, have become more popular for REE analysis. For direct analysis of solids, INAA, XRF, and LIBS techniques, as well as LA-based ICP-MS techniques, are being extensively utilized. The LIBS technique in particular requires little to no sample preparation. TIMS, SIMS, and SHRIMP techniques are being used for isotopic as well as dating REE depots. Portable analytical techniques, such as pXRF, pLIBS, and Raman spectrometers are able to perform in situ analysis even in the field, helping to make fast decisions during exploration studies. At present, hyperspectral remote sensing techniques including handheld, drone, and satellite-based techniques have become very popular in REE exploration studies because of their ability to cover larger areas in a limited time and, thus, became very cost-effective. Deployment of microanalytical devices/sensors mounted in remotely operated vehicles (ROV) is being successfully utilized in detecting REE-rich deposits in the deep oceans. Providing updated in-depth information on all these important aspects with suitable examples, especially from the point of view of REE research studies is the focal point of this review article.

Rare Earth Elements (REE) Extraction from The Stones Hill at Padang Area by Precipitation

Rare Earth Elements (REE) are a very important element in modern life such as electronics, materials engineering, and even medicine. Gadolinium (Gd) is one of the REEs that is used as a basic material for implants as well as being used for other basic materials such as a corrosion inhibitor, control rods for nuclear reactors, and others. In this case, the elements are found along hills in the Padang area which have the potential to be produced in large quantities from six rock minerals such as granite, basalt, clay, silica, tuff, and limestone.). Based on the results of identification using the XRF spectrometer test tool, it was found that the six mineral rocks had an abundance of rare earth elements. The results of testing the extraction of Gadolinium Oxide (Gd2O3) using XRF were successfully carried out, Gd2O3 can be extracted by 0.06% - 1.84% in basalt rock, 0.47% - 0.95% in clay rock, and 0% - 0.88% in silica rock. This proves that the main rock minerals from stones have the Rare Earth Elements (REE) and can be extracted with using the Precipitation Extraction method.

The precipitation process for a rare earth leach solution with calcium oxide in the presence of ascorbate and calcination to oxide of high purity

Sulfate ions coprecipitate with rare earth metal ions to form alkaline rare earth sulfate (RE2(OH)4SO4) in the CaO precipitation process, leading to excessive content of sulfate in the mixed rare earth oxide. Due to the difference of coordination ability between ascorbate, sulfate, hydroxyl and rare earth metal ions, ascorbate is introduced into the pregnant leach solution (PLS) during the CaO precipitation process. It realizes the coprecipitation between ascorbate (C6H7O6−) and rare earth metal ions, reducing the formation of RE2(OH)4SO4 and improving the purity of mixed rare earth oxide. In this paper, the standard reaction Gibbs free energy changes of the possible reactions in the precipitation process were calculated using the group contribution method, to draw the species distribution equilibrium diagram with Newton's iteration method. When ascorbate exists, rare earth metal ions in the PLS tend to form the alkaline rare earth ascorbate (RE2(OH)4(C6H7O6)2) instead of RE2(OH)4SO4. Furthermore, the effect of the reaction conditions on the precipitation process were studied. When the molar ratio of rare earth metal ions to ascorbate was 1.17, the purity of the mixed rare earth oxide was 96.2 wt% and the sulfate content was 2.2 wt%. Finally, based on the results of the material balance calculation, FTIR, XRD and TG-DSC tests, it was further confirmed that ascorbate participated in the form of RE2(OH)4(C6H7O6)2, and effectively suppressed the generation of RE2(OH)4SO4. Consequently, the results facilitate the green and efficient extraction of rare earths from the ion-adsorption type ore.

Synergistic extraction of rare earth elements, actinium, americium, and barium with TTA and Pb resin from acetate buffer solutions

Synergistic extraction of rare earth elements, actinium, americium, and barium with TTA and Pb resin from acetate buffer solutions

Preliminary Flowsheet Development for Mixed Rare Earth Elements Production from Apatite Leaching Aqueous Solution Using Biosorption and Precipitation

A flowsheet was developed to extract mixed Rare Earth Elements (REEs) from an aqueous solution generated by nitric acid leaching of apatite concentrate. In this study, Platanus orientalis (P. orientalis) leaf powder was employed in the biosorption process to purify the pregnant leach solution. The sorption and desorption processes were investigated and optimized. The results demonstrated the successful extraction of REEs from the pregnant leach solution using the biosorbent. Hydrochloric acid effectively desorbed REEs from the loaded P. orientalis leaf powder. Thermodynamic studies indicated that REEs’ sorption on P. orientalis leaf powder was an endothermic and spontaneous process. Precipitation and calcination steps yielded mixed rare earth oxides (REOs) with an assay of approximately 87%. The final product, mixed REOs, can be further refined through releaching and a secondary impurity removal stage prior to entering the individual REE separation process. Alternatively, it can be fed directly into the solvent extraction process or alternative technologies to obtain individual heavy and light REEs.

Comparison of extraction abilities of deep eutectic solvents and aqueous acid solutions for extraction of rare earths and transition metals

In recent years, deep eutectic solvents have attracted increasing interest as effective extractants for the separation of both organic substances and metals from various objects. Acid-based deep eutectic solvents are most often used as extractants for the extraction of metals. In this work, for the first time, the extraction efficiency of transition metals and rare earth elements (Y, Zr, Nb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf and Ta) from mining tailings and Na, K, Ca, Mg, Cu, Fe, Mn, Pb, Ba, Ni and Sr from biodiesel samples using acidic deep eutectic solvents and saturated aqueous solutions of the same acids (malonic, malic, tartaric and citric) is compared. For this, deep eutectic solvents based on acids and their aqueous saturated solutions were prepared and studied. The prepared mixtures were analyzed by IR spectroscopy to confirm the formation of eutectic solvents. Properties such as the density and viscosity of the resulting mixtures were also investigated, as this can be of key importance for the efficiency of metal extraction. The extraction of rare earth metals from mining tailings took a long time (up to several days), while the extraction of metals from fuel took no more than 30 min. Atomic emission spectral methods were used as an analysis method. It is shown that the extraction efficiency with aqueous solutions is better than that with eutectic solvents, which casts doubt on the need for deep eutectic solvents use in this area.

Characterization and pre-concentration of rare earth elements in density fractionated samples from the Waterberg Coalfield, South Africa

The increased global demand for rare earth elements (REEs) from unconventional sources has led to increased interest and research in coal deposits. South Africa has extensive coal resources, but understanding of the concentration, mode of occurrence, and distribution of REEs in the coals and associated sediments is limited. This study aims to assess selected coal samples obtained from an exploration project underway in the Waterberg Coalfield (South Africa) to determine the concentration and mode of occurrence of REEs, and to gain insight into the behaviour of REEs during density fractionation. Density fractionation of coal is considered a pre-concentration method prior to REE extraction. Samples were selected from zones 8, 7, 4, and 3, spanning the Grootegeluk and Vryheid Formations of the Waterberg Coalfield. Density fractionation was conducted at relative densities (RD) of 1.3 to 1.8, providing float (F) and sink (S) products. Five parent and thirty density-fractionated coal samples were characterized using proximate analysis, petrography, X-ray diffraction (XRD), and the concentration of REEs determined using Inductively Coupled Plasma- Mass Spectrometry (ICP-MS) (after microwave digestion).The samples are classified as medium-rank C bituminous coals with variable maceral composition. The dominant minerals are kaolinite and quartz, occurring as both syngenetic and epigenetic phases. The total REY (REEs + yttrium) concentrations range from 45.1 to 389.2 ppm, higher than for world coals (except sample 8H F1.30, REY = 45.1 ppm), and generally higher than the average for Chinese coals. Float products obtained at 1.40 to 1.80 RD show greater variation of light REY (LREY) compared to medium REY (MREY) and heavy REY (HREY), whereas float fractions at 1.30 and sink fractions at 1.80 RD show no distinct enrichment patterns. Although the results suggest a relationship between the concentration of LREY with float fractions obtained between 1.40 and 1.80 RD, pre-concentration using density fractionation generally shows limited benefits for these coals. Ashing of the coals may be more effective in concentrating the REEs and further investigations are therefore required.

Reserves and extraction of rare earth metals and elements as a key factor in the renewable energy sector development at the the world economy transformation current stage

The use of renewable energy sources, which are experiencing a period of rapid development, is one of the stages of the current energy transition, as the world community tries to ensure a future with zero CO2 emissions and to achieve energy independence and security. At the same time, for output of the wide range of products for the renewable energy sector, as well as for the development of energy depot systems, it is necessary to use rare earth elements and metals in production. The results of the analysis of data on reserves, production and calculated values of the resource availability coefficient of rare earth elements and metals shows that at the existing level of production, the proven reserves of cobalt will last for ≈ 50 years, lithium– for ≈ 200 years and rare earth elements – for ≈ 450 years, respectively, which leads to a limitation of the global transition speed to renewable energy sources and makes it necessary to look for new technical solutions.

Investigation of Hydrated Dy(III) and MgSO4 Leaching Agent Ion Adsorption on (001) Surface of Montmorillonite: A Study Using Density Functional Theory

Kaolinite is one of the principal rare earth element (REE) ion-adsorption clays that hosts a wide range of elements, including Dy(III) as a representative example. Ammonium sulfate is a typical salt used to leach REEs. Due to the carbon dioxide emissions which occur during ammonia production, it is urgently necessary to develop low environmental pollution leaching agents that can replace (NH4)2SO4. MgSO4 is regarded as the most promising eco-friendly leaching agent. Herein, the first-principles plane-wave pseudopotential method based on the density functional theory (DFT) was used to investigate the stable adsorption structures of Dy(III) and its hydrated ions, MgSO4 leaching agent ions and the corresponding hydrated ions on the surface of kaolinite, which revealed the adsorption mechanism of Dy(III), Mg(II), and SO42− on the silico–oxygen plane and the aluminum–hydroxyl plane of kaolinite. Based on the research results of the steric hindrance effect of Dy(III) on the silico–oxygen plane and the aluminum–hydroxyl plane of kaolinite, the adsorption of Dy(H2O)103+ was more stable on the silico–oxygen plane. It was easier to leach out Dy(III) with MgSO4, while SO42− tended to interact with the rare earth ions in an aqueous solution. The results provide theoretical guidance for efficient rare earth extraction and obtaining novel efficient leaching agents.

Investigation on the Value-Added Production of Silicon Dioxide and Synthesizing Zeolites as well as Extraction of Rare Earth Elements from Fly Ash

Coal fly ash is one of the most promising secondary sources for extracting high value-added rare earth elements. Nevertheless, the majority of rare earth elements in coal fly ash are associated with the aluminosilicate glassy phase, hindering their solubility during the acid leaching process and resulting in the traditional rare earth elements extraction method, which is unavoidably complex in operation and poor in the economy. In this study, prior to the conventional acid leaching, the realization of the coal fly ash activation was considered. This consisted of two steps involving the coal fly ash calcination at the elevated temperatures using recyclable Na2CO3 and the water and alkali washing. It helped in developing the pore structures in coal fly ash, facilitating the leaching solution to rare earth elements, and reducing the acid consumption of rare earth elements leaching. Simultaneously, the generated aqueous solutions could precipitate two new valuable products, the purified silica oxide powder (257.58 g·kg−1, 338.1 m2·g−1 BET, 40 nm grain size, 93.43% purity) and porous zeolites (410.3 g·kg−1). The residual rare earth elements in the pretreated solid residue can be easily extracted, with an extraction efficiency of 91.24% and an acid saving rate of 74.5%. Therefore, a multiple of value-added products can be obtained by this new extraction method with great economic significance.

Developing N,N,N’,N’-tetra (2-ethylhexyl) diglycolamide encapsulated polymeric beads as promising rare earth extracting agents

ABSTRACT The multi-faceted applications of rare earth elements (REE) in science and technology are not unknown. Scarcity in the primary sources of RE makes it necessary to explore different secondary sources available. Availability of REE in significant amount in spent NdFeB magnetic scrap makes the recycling of REE from this scrap, a lucrative option. In this work, synthetic solutions of 10 g/L (containing the rare earths Nd, Pr and Dy along with Fe) were equilibrated with the organic extractant N,N,N,’N’-tetra (2-ethylhexyl) diglycolamide (TEHDGA) encapsulated in polyethersulfone beads to study the extraction behavior of the REEs from nitric acid medium. Iron (Fe), the major component present in NdFeB scrap, poses the biggest challenge for rare earth extraction from the scraps. The TEHDGA impregnated polymeric beads were found to selectively extract the REEs, leaving Fe(III) in the feed solution. TEHDGA displayed higher selectivity towards the heavier rare earth Dy followed by Nd and Pr. The loading capacity of the beads was measured to be > 1700 ppm. The effect of different experimental parameters, such as contact time, solid-liquid ratio, TEHDGA concentration, feed acidity, were investigated. Contact time of 24 h, TEHDGA concentration of 0.75 M, solid-liquid ratio either 1:5 or 1:10 and feed acidity between 2 and 5 M have been found to suitable for quantitative extraction of REE particularly Dy(III). The recovery of the REEs from the loaded TEHDGA beads was > 90%. Furthermore, the experiment was carried out with higher quantity of beads and feed solution to study applicability of the same in bulk scale. A novel, easy and single-step separation of REE from Fe has been presented in this work.

Adsorptive capacity and kinetic studies of PK216 resin for the extraction of Pr, Gd, and Dy rare earth elements

AbstractBACKGROUNDThe removal of rare earth elements (REE) ions from aqueous solutions is a challenging task, and it requires a cost‐effective and readily available adsorbent material with excellent performance. In this study, PK216 resin was utilized for the adsorption kinetics and mechanism studies of REE ions owing to its outstanding performance, low cost, and easy availability.RESULTSThe findings revealed that higher loading resulted in increased adsorption capacity, while pH and temperature adjustments had minimal effects on the adsorption process, which remained constant within the pH range of 1–6 and a temperature range of 25–85 °C. Moreover, the thermodynamic parameters showed that the adsorption reaction for praseodymium (Pr) and gadolinium (Gd) was spontaneous and exothermic, whereas for dysprosium (Dy) it was endothermic due to its high hydration enthalpy. This characteristic nature of Dy requires additional energy from the surroundings to dissociate from the aqueous phase and proceed to the PK216 resin surface compared to Pr and Gd. The Langmuir model and pseudo‐second‐order reaction were found to be the fitting models for the adsorption process on PK216 resin. Additionally, the chemisorption of Pr, Gd, and Dy resulted in monolayer coverage. The diffusion process was found to be intraparticle and film diffusion, as it fitted the Boyd kinetic model as opposed to the Weber–Morris intraparticle model.CONCLUSIONThe results indicate that higher loading enhances the adsorption capacity, and the Langmuir model and pseudo‐second‐order reaction are the most suitable models for the adsorption process on PK216 resin. © 2023 Society of Chemical Industry

Rare earth elements in tea garden soils and their bioavailability to tea buds in Taiwan

Tea (Camellia sinensis) is a widespread beverage plant that prefers aluminum-enriched acidic soils. However, rare earth elements (REEs) might be highly phyto-available in these soils. With the increasing demands for REEs in high-technology industries, understanding the dynamics of REEs in the environment is essential. Thus, this study identified the total concentration of REEs in the root-zone soils and corresponding tea buds (n = 35) collected from tea gardens in Taiwan. Additionally, the labile REEs in the soils were extracted with 1 M KCl, 0.1 M HCl, and 0.05 M ethylenediaminetetraacetic acid (EDTA) to elucidate the fractionation tendency of REEs in the soil-plant system and the relationships between REEs and Al in the tea buds. The concentration of light REEs (LREEs) was higher than those of medium REEs (MREEs) and heavy REEs (HREEs) in all soil and tea bud samples. According to the upper continental crust (UCC) normalization, MREEs and HREEs were more abundant than LREEs in the tea buds. Furthermore, REEs remarkably increased with increasing Al in the tea buds, whereas the linear correlations between Al and MREEs and HREEs were stronger than between LREEs. Compared with LREEs, the extractabilities of MREEs and HREEs by all single extractants in the soils were higher, coinciding with their higher UCC-normalization-based enrichments in the tea buds. Moreover, the 0.1 M HCl- and 0.05 M EDTA-extractable REEs were affected by soil properties and significantly correlated with the total REEs in the tea buds. The concentration of REEs in the tea buds was successfully predicted by empirical equations of extractable REEs with 0.1 M HCl and 0.05 M EDTA, as well as general soil properties including pH, organic carbon, dithionite-citrate-bicarbonate-extractable iron, aluminum, and phosphorus. However, this prediction should be further verified using many soil and tea types in the future.

Intensified extraction of rare earth elements from coal fly ash

AbstractBACKGROUNDThe high demand for coal‐based energy leads to the production of a massive amount of coal fly ash (CFA). Owing to the content of rare earth elements (REEs), CFA is regarded as one of the promising secondary sources of REEs. The corrent study utilized two intensified extraction methods, subcritical water extraction (SWE) and microwave assisted extraction (MAE), in the recovery of REEs, including yttrium (Y) and samarium (Sm), from CFA sample.RESULTSThe effects of acid concentration, temperature, and solid to liquid ratio (S/L), and reaction time on leaching efficiency were investigated. Total of 80.32% of Y and 68% of Sm were leached out using SWE at 1.0 N HCl, S/L of 5 g/L, 150 °C for 5 min. Meanwhile, MAE yielded leaching efficiency of 71.99% of Y and 54.48% of Sm at 2.0 N HCl, S/L of 2.5 g/L, 150 °C for 5 min. Both methods performed better than conventional method.CONCLUSIONSFrom comparisons, SWE showed advantages of higher leaching efficiency at lower acid concentration, while MAE was more rapid and more energy efficient for REEs recovery from CFA. © 2023 Society of Chemical Industry (SCI).