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In this study, the concentration of thirteen non-volatile elements in coal fly ash samples obtained from the Kangal coal-fired thermal power plant located in Sivas province of Turkey was determined using an energy dispersive X-ray fluorescence (EDXRF) spectrometer. Non-volatile elements in coal fly ash samples were analysed in three groups: major (Al, Si, and Ca), rare earth (Y, La, Ce, Pr, and Nd), and other trace elements (Ga, Rb, Mo, Ba, and Hf). The average concentrations of Ca, Si and Al were found as 22.8, 10.9 and 5.4%, respectively. The average concentrations of Pr, Y and, Nd were found as 23.9, 19.1 and 78.2, respectively. La and Ce were observed below the detection limit of 2 mg/kg, except for two samples. The average concentrations of Ga, Rb, Mo, Ba and Hf were found as 18.6, 51.1, 177.3, 993.5 and 3.9 mg/kg, respectively. According to the average values of enrichment factor estimated for elements analysed in fly ash samples, Mo is found extremely enriched while Ca and Hf are significantly enriched. [ABSTRACT FROM AUTHOR]

Increasing demand for low carbon technologies and renewable energy sources requires our resources and economies to be circular. Many countries agree that the responsible consumption, production, and recycling of rare-earth-containing products is essential as a way to achieve the sustainable development goals also set out in the European Green Deal. Sustainable sourcing is targeted with carefully designed roadmap for cost efficient REE production from end-of-life products (EoLs) in addition to mining activities as providing primary sources. Hydrometallurgical methods, such as roasting, leaching, precipitation, crystallization, solvent extraction, and ion exchange includes fast developing, selective, eco-friendly, and cost-effective technologies especially for the extraction of REEs. This article provides an overview of primary and secondary resources and summarizes presents case scenario of studies carried out on the use of some promising methods, which could serve as an economical means for recovering REEs. [ABSTRACT FROM AUTHOR]

Despite the growing interest, the information available on rare earth elements (REEs) in the last two decades is relatively premature and sparse. The importance of these elements as indicators of soil and physiological processes and responses have contributed to the increased interest in these previously less considered elements in the environmental sciences. This study provides an overview of the content and distribution of rare earth elements in the soil in the vicinity of the hydrothermal volcanogenic As-Sb-Tl deposit of Allchar, North Macedonia. Elemental contents were determined by inductively coupled plasma mass spectrometry (ICP-MS). The light rare earth elements (LREEs) content in the study area ranges from 8.92 to 188 mg/kg, while the heavy rare earth elements (HREEs) content ranges from 1.95 to 42.7 mg/kg. It can be concluded that there is some enrichment of light REEs in the volcanic intrusive rocks of the Allchar mine area, including latite, quartz–latite, trachyte and occasionally andesite and dacite. The spatial distribution of HREEs is closely related to the lithology of the region, especially the sandstone and claystone, followed by layered and massive carbonate rocks (limestone, dolomite, marble) that occurred in the Middle and Upper Triassic. [ABSTRACT FROM AUTHOR]

Significant amounts of petroleum are found in the deeply buried Cambrian Xiaoerbulake Formation in the Tarim Basin. However, limited understanding of origin of diagenetic fluids hampers petroleum exploration. In this study, petrological and high-resolution geochemical methods have been performed to understand the origin and evolution of diagenetic fluids, and their effects on the formation of dolostone reservoir. The Xiaoerbulake Formation is characterised by microbialites. The matrix is characterised by modern seawater-like rare earth element and yttrium (REY) patterns and δ18O values of −6.02 ± 2.11‰ Vienna Pee Dee Belemnite (VPDB). Fine-crystalline dolomite cements have similar δ13C values and heavy rare earth element enrichment patterns to that of matrix dolomite, yet with lower δ18O values of −7.47 ± 1.2‰ VPDB. In the deep-burial regimes, medium- to coarse-crystalline dolomite cements and saddle dolomites were precipitated at temperatures of 90–120 and 130–190 °C, respectively, lower δ18O values, distinct middle rare earth element enrichment, and high Fe and Mn contents compared with matrix and fine-crystalline dolomite cements. These imply thermochemical reduction of Fe- or Mn-rich oxides and/or hydrothermal fluids. Compared with other types of dolomite cements, calcite cements are characterised by low δ13C values (as low as −6‰ VPDB), light rare earth elements enrichment and significantly elevated Y/Ho ratios (86 ± 59.3), likely related to the oxidation of organic matter during thermochemical sulfate reduction (TSR). Consequently, diagenetic fluid may have evolved from: Cambrian seawater, meteoric water, shallow-buried seawater-dominated pore water, medium-deep-buried ferrous-rich pore water, lately high-salinity hydrothermal fluid-dominated pore water and finally to acidic fluids related to TSR dissolution. Reservoir quality is enhanced by hydrothermal pulses and TSR in deep-burial settings. This study is significant for those concerned with the formation of deep-buried carbonate reservoirs. [ABSTRACT FROM AUTHOR]

This study's objective was to evaluate the depth profiles of rare earth elements (REEs) in two Pb-210 dated sediments cores retrieved from the Oualidia lagoon, reconstruct their anthropogenic history, and assess their potential ecological risk. The sediment cores analysis was carried out using instrumental neutron activation analysis. Other physical-chemical parameters (bulk, organic matter, grain size) were also measured. The results indicated that the highest values were recorded in the topmost layers of the sediment cores and depleted with depth. The historical records of REEs revealed an exponential increase in their concentrations from the 50s. The enrichment factor, geo-accumulation index, and contamination factor calculated for each sediment core layer have exhibited important concentrations of Gd, Sm, and Eu, suggesting an anthropogenic origin of detected elements. Based on ecological risk >40 and the risk index >220, Gd, Eu, and Sm pose a high risk on the study area, while the other elements present moderate and mild risk. The obtained results revealed an increasing tendency of REEs accumulation into the Oualidia lagoon and suggested that a new source is feeding the lagoon sediments by these elements. These findings provided a clear picture of REEs evolution between 1903 and 2014 and baseline information on the historical deposition of these elements in the Oualidia lagoon. [ABSTRACT FROM AUTHOR]

This study was carried out to evaluate the extent of carbonate crash in some Niger Delta oil wells and the levels of heavy metals (HMs) and rare earth elements (REEs) as useful fingerprinting tools in the characterization of the oil wells. Thirty-nine (39) rock samples were collected from three (3) oil wells in the Niger Delta, Nigeria. The carbonate contents were determined using Chittick apparatus while the elemental concentrations were determined using Atomic Absorption Spectrophotometry. Results of the study indicated that the carbonate contents of the rock samples decreased with increasing depth, due to a possible higher-than-average dissolution of CaCO3 and/or excess bio-SiO2 production. Among the investigated HMs, manganese had the highest mean concentration while nickel had the lowest mean concentration. Cerium had the highest mean concentration while lanthanum had the lowest mean concentration among the REEs. Mean V/Ni ratios of Oil Well 1 (3.21) indicated marine organic matter input while Oil Well 2 (2.47), and Oil Well 3 (2.16) indicated organic matter input of both marine and terrestrial sources. V/(V + Ni) ratios (>0.5) of the oil wells indicated that the organic matter was deposited under anoxic conditions. Variations in the distribution patterns of HMs, REEs, and carbonate content of the rock samples of Niger Delta oil wells indicated that the organic matter source and depositional environment were quite similar. [ABSTRACT FROM AUTHOR]

Inorganic elements have been associated with brain tumours for long. The blood concentration of 47 elements was assessed by ICP-MS in 26 brain tumour patients and 21 healthy subjects from Bucharest (Romania). All 47 elements were detected in the brain tumour tissue, and 22 were detected in > 80% of samples; this implies that these elements can cross the blood-brain barrier. Median blood levels of cadmium, lead, and nickel were higher than the reference values (1.14, 53.3, and 2.53 ng/mL). Gadolinium and tantalum showed significantly higher concentrations among cases. We observed considerable differences and different profiles of the presence of inorganic elements between the tumour and non-tumour brain tissue and between tissue from the primary tumour and tissue from brain metastasis. Our data suggest that similar to heavy metals, other elements – commonly used in high tech devices and rare earth elements – can also influence brain tumour. [ABSTRACT FROM AUTHOR]

In Brazil, the main producers of phosphate fertilisers are responsible for the production of approximately 12 million tons of phosphogypsum (PG) per year. This phosphogypsum has been used for many years in agriculture as a soil amendment. For its safe long-term application, it is necessary to characterise the impurities present in phosphogypsum and to study the leaching or dissemination of such impurities to waters or other ecosystem compartments. This paper aims to evaluate the availability of Rare Earth Elements (REEs): La, Ce, Nd, Sm, Eu, Tb and Lu. The technique used for the determination of the elements of interest in the soil, soil mixed with PG, PG and leachate was the instrumental neutron activation analysis. For this purpose, an experiment was carried out, in which columns filled with sandy and clay Brazilian typical soils mixed with phosphogypsum were percolated with water, to achieve a mild extraction of these elements. The results showed that the ƩREE in PG was in the order of 7,600 mg kg−1 while in the leachate, the sum was in the order of 100 µg L−1 results obtained for the available fraction obtained was below 1%, giving evidence that although the REEs are present in the PG in higher concentrations, they are not available to the water. It can be concluded that the addition of PG to the soils does not contribute to a significant enhancement of the REEs in water. [ABSTRACT FROM AUTHOR]

Zn-Co ferrites doped with Er3+ and Pr3+ with different concentrations were synthesised by co-precipitation method at constant calcination temperature. XRD results show an increase in the lattice parameter. Particle sizes determined from TEM are close to those determined from XRD, confirming PVP acts as controlling of the nanoparticles growth. Electron paramagnetic resonance (EPR) spectra analysis indicates that the spin-spin relaxation time T2 increases and the g-factor decreases with increasing Er3+ and Pr3+ content. The saturation magnetisation and the coercivity decrease with increasing RE3+ content. The dielectric constants ε' and ε" and the dielectric loss tangent (tanδ) decrease, and the a.c. conductivity increases with the increase of Er3+ concentration between 0.00 wt% and 0.20 wt%; the same trend is observed for samples doped with Pr3+ of concentrations 0.04, 0.12 and 0.20 wt%, while that doped with 0.08 wt% of Pr3+ shows a peak at low frequency. [ABSTRACT FROM AUTHOR]

Ag and rare earth elements (Ce-La) co-modified TiO2 photocatalysts were synthesized via sol-gel method. The structure of co-modified TiO2 was investigated by using TEM, XRD, XPS and UV-visible absorption spectra. Based on the ammonia nitrogen degradation experiment, the effects of the co-modifier content (1, 3, 5wt% Ag/Ce/ La) on the photocatalytic activity of TiO2 were evaluated systematically. The results showed the crystal phase of modified TiO2 transformed from anatase/rutile mixture to pure anatase, and the anatase crystallites size decreased after co-modifying. Ag was deposited onto the surface of TiO2 photocatalyst, and the synergistic effect of Ce-La and Ag caused the decrease of band gap energy from 3.2 eV to 2.0 eV. In the degradation of ammonia nitrogen wastewater, 3% Ag/Ce/La- TiO2 photocatalyst represented the best activity, whose degradation efficiency of ammonia nitrogen reached 93.9% after 6 h degradation reaction, whereas was 27.8% in case of pure TiO2. [ABSTRACT FROM AUTHOR]

The Wadi Bidah Mineral District of Saudi Arabia contains more than 16 small outcropping stratabound volcanogenic Cu–Zn–(Pb) ± Au-bearing massive sulphide deposits and associated zones of hydrothermal alteration. Here, we use major and trace element analyses of massive sulphides, gossans, and hydrothermally altered and least altered metamorphosed host rock (schist) from two of the deposits (Shaib al Tair and Rabathan) to interpret the geochemical and petrological evolution of the host rocks and gossanization of the mineralization. Tectonic interpretations utilize high-field-strength elements, including the rare earth elements (REE), because they are relatively immobile during hydrothermal alteration, low-grade metamorphism, and supergene weathering and therefore are useful in constraining the source, composition, and physicochemical parameters of the primary igneous rocks, the mineralizing hydrothermal fluid and subsequent supergene weathering processes. Positive Eu anomalies in some of the massive sulphide samples are consistent with a high temperature (>250°C) hydrothermal origin, consistent with the Cu contents (up to 2 wt.%) of the massive sulphides. The REE profiles of the gossans are topologically similar to nearby hydrothermally altered felsic schists (light REE (LREE)-enriched to concave-up REE profiles, with or without positive Eu anomalies) suggesting that the REE experienced little fractionation during metamorphism or supergene weathering. Hydrothermally altered rocks (now schists) close to the massive sulphide deposits have high base metals and Ba contents and have concave-up REE patterns, in contrast to the least altered host rocks, consistent with greater mobility of the middle REE compared to the light and heavy REE during hydrothermal alteration. The gossans are interpreted to represent relict massive sulphides that have undergone supergene weathering; ‘chert’ beds within these massive sulphide deposits may be leached wall-rock gossans that experienced silicification and Pb–Ba–Fe enrichment from acidic groundwaters generated during gossan formation. [ABSTRACT FROM AUTHOR]

Luminescence nanocomposites based on barium titanate nanoparticles (BaTiO3), polystyrene (PSt), and terbium ion (Tb3+) were synthesized by using a combination of reversible addition fragmentation chain transfer polymerization, Friedel-Crafts alkylation reaction and coordination chemistry. The modification of the surface of BaTiO3was conducted by an exchange process with S-benzyl S’-trimethoxysilylpropyltrithiocarbonate to anchor macro-initiators for the polymerization of styrene. Subsequently, PSt grafted barium titanate was functionalized by the substitution reaction between 4-(chloromethyl) benzoic acid and PSt to produce hybrids, BaTiO3-g-PSt -COOH. The coordination of the hybrids with Tb3+ions in the presence of 1,10-phenanthroline (Phen) afforded fluorescent Tb3+tagged carboxylic acid functionalized polystyrene/barium titanate (BaTiO3-g-PSt-Tb3+-Phen). FT-IR, XRD, TGA, and SEM analyses revealed the formation of BaTiO3-g-PSt-Tb3+-Phen hybrids. The optical properties of BaTiO­3-g-PSt-Tb3+-Phen were investigated by using fluorescence spectroscopy. [ABSTRACT FROM AUTHOR]

The Chingiz–Tarbagatai megazone is a well-known early Palaeozoic unit in eastern Kazakhstan that extends into northern West Junggar along the Tarbagatai–Xiemisitai–Sharbuti Mountains. Here, we report new geochronological and geochemical data for the Chagantaolegai ophiolite, discovered in the south Xiemisitai Mountains, north of the Heshituoluogai Valley in West Junggar. The laser ablation inductively coupled plasma mass spectrometry zircon U–Pb ages of a gabbro in the Chagantaolegai ophiolite are 517 ± 3 and 519 ± 3 Ma, corresponding to the early to middle Cambrian. Serpentinized peridotites in the ophiolite show low rare earth element (REE) abundances (0.61–0.94 μg/g) and slight loss of middle REEs. Chagantaolegai metagabbro samples have flat to very slightly depleted patterns in light REEs, with a narrow range of REE abundances. The Chagantaolegai spilites and metagabbros display similar flat patterns, which show a geochemical signature similar to mid-ocean ridge basalt (MORB) between Yb and Zr, and diverge from MORB towards the most incompatible elements in MORB-normalized multi-element diagrams. The Th/Yb vs. Nb/Yb diagram for the spilite samples also suggests a mid-ocean ridge (MOR) setting. To summarize, all the geochemical characteristics of the Chagantaolegai ophiolite point to MOR ophiolite. The positive εNd(t) values (0.78 to +9.85) suggest that the gabbros and spilites were derived from a depleted mantle source with chemical inhomogeneity. The Chagantaolegai ophiolite spatiotemporal characteristics correlate well with the Kujibai and Hongguleleng ophiolites in the northern part of West Junggar, and the Zhaur and Balkybek ophiolites in eastern Kazakhstan. These data show that early Palaeozoic oceanic crust started to develop in the early to middle Cambrian in northern West Junggar. Stratigraphic correlations also suggest that the South Saur Fault and an inferred fault buried in the Heshituoluogai depression are the northern and southern boundary of the Chingiz–Tarbagatai megazone, respectively. [ABSTRACT FROM AUTHOR]

A resin for extraction chromatography was synthesized by suspension copolymerization, and its performance in separating four rare earth (RE) elements, gadolinium (Gd), terbium (Tb), dysprosium (Dy), and holmium (Ho) was investigated. The resin was synthesized by changing the reaction rate using a reaction initiator (benzoyl peroxide, BPO). The effects of the concentration of the eluent, HCl, were examined. The separations were best ( = 1.000, = 1.091, and = 1.495) when BPO was added in 3 aliquots, and 0.3 mol/L HCl was used as the eluent. The synthesized extraction resin gave similar separation resolutions to the commercial resin at lower HCl concentrations than the 0.6 mol/L used with the commercial resin. The scanning electron microscopy (SEM) analyses showed that the best-prepared synthesized extraction resin had uniform, spherical particles. The Fourier transform infrared (FT-IR) spectra of the synthesized extraction resins showed the characteristic signals of styrene-divinyl benzene copolymer. [ABSTRACT FROM PUBLISHER]

Four new polyoxometalate compounds consisting of Anderson-type anions and trivalent rare earth (RE) cations, [RE2(H2O)14M(OH)6Mo6O18][M(OH)6Mo6O18] · 14H2O, RE = Y, M = Cr(1), Al(2); RE = Yb, M = Al(3), Cr(4), have been synthesized in aqueous solution and characterized by elemental analyses, infrared (IR) spectra, thermal gravimetric (TG) analyses, and single crystal X-ray diffraction. [M(OH)6Mo6O18]3- as a bidentate ligand coordinates to two RE3+, forming a double-supported cation [RE2(H2O)14M(OH)6Mo6O18]3+. The cations and other [M(OH)6Mo6O18]3- anions in the crystals are linked via hydrogen bonding interactions tightly, forming four supramolecular compounds. The magnetic properties of 1, 3, and 4 have been examined by measuring their magnetic susceptibilities from 2 to 300 K. [ABSTRACT FROM AUTHOR]

This paper investigated dielectric properties of rare earth (Y, Gd, Yb)-doped barium titanate sintered in pure nitrogen. The difference in doping behaviors of intermediate rare-earth ions (Gd, Y, Yb) and their effects on the dielectric properties of barium titanate were investigated. The intermediate rare earth elements (Gd, Y, Yb) were substituted in the A-site of the perovskite lattice. The different rare earth element had a crucial effect on dielectric properties of rare-earth-doped BaTiO3. Gd-doped barium titanate had the largest dielectric constant (about 20000) and the largest dielectric loss (about 0.6), the smallest leakage current and no tunability. Y-doped specimen had the largest leakage current. [ABSTRACT FROM AUTHOR]

In order to enhance the anti-fouling ability and separation efficiency of polysulfone (PSF) membrane during separating of Chinese yam polysaccharides, a novel composite membrane was prepared through a sol-gel process after adding Ce-doped nonstoichiometric nano-silica with higher activity and hydrophilic property to the porous matrix of PSF. Ce-doped nonstoichiometric nano-silica was synthesized by doping the rare earth Ce element. Novel composite membranes and ordinary membranes without doping Ce-doped nonstoichiometric nanosilica were used to separate Chinese yam polysaccharides while the content of polysaccharide was tested. The results designate that the content of polysaccharide separated by composite membrane which reached 78.3% was higher than that of polysaccharide separated by ordinary membrane which reached 46.7%. The flux of the composite membrane increased with increasing of operation pressure. With the temperature rising, the polysaccharide solution flux of composite membrane ascended from 289 L/(m2h) to 312 L/(m2h). The flux of the composite membrane was kept at a high value for 25 h before reaching a steady state (243 L/(m2h)), which was higher than the stable flux of ordinary membrane (160 L/(m2h)). After the composite membrane was washed for six times, its flux still reached 90% of initial value. The experiment data indicate that the anti-fouling ability and hydrophilic property of composite membrane were significantly enhanced. Therefore, Chinese yam polysaccharides can be efficiently separated by the novel composite membrane. [ABSTRACT FROM AUTHOR]

Systematic investigations were carried out into the sorption of rare earth elements (REEs) on carbon nonofibers (CNFs) by inductively coupled plasma mass spectrometry (ICP-MS). The experimental parameters for preconcentration of REEs, such as pH, sample flow rate and volume, eluent concentration, and interfering ions on preconcentration of REEs have been examined in detail. The studied metal ions can be adsorbed quantitatively on CNFs in a pH range from 2.0 to 5.0, and then eluted completely with 0.5 mol l-1 HNO3. Based on the above facts, a novel method using a microcolumn packed with carbon nanofibers as an adsorption material was developed for the separation and preconcentration of REEs prior to their determination by ICP-MS. The proposed method has been successfully applied to the determination of light (La), medium (Eu and Gd) and heavy (Yb) rare earth elements in real sample with the recovery more than 90%. In order to validate this method, two certified reference materials of tea leaves (GBW 07605) and mussel (GBW 08571) were analyzed, and the determined values are in good agreement with the certified values. [ABSTRACT FROM AUTHOR]

Lanathum (La)‐doped Fe 3 O 4 magnetic nanoparticles were prepared in aqueous solution at room temperature, then La‐doped Fe 3 O 4 ‐polyaniline (PANI) nanocomposites containing a dispersion of La‐doped Fe 3 O 4 nanoparticles were synthesized via in‐situ polymerization of aniline monomer. The structure and properties of the synthesized samples were characterized with X‐ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA), inductively coupled plasma atomic emission spectrometry (ICPAES), and a vibrating sample magnetometer (VSM). The resulting particles of La‐doped Fe 3 O 4 and La‐doped Fe 3 O 4 ‐PANI were almost spherical with diameters ranging from 15 to 25 nm and 25 to 85 nm, respectively. The La‐doped Fe 3 O 4 ‐PANI composite presented core‐shell structures; polyaniline covered the La‐doped Fe 3 O 4 completely. The specific saturation magnetization of La‐doped Fe 3 O 4 ‐PANI depended on the starting material of La‐doped Fe 3 O 4. It increased with increasing amounts of La and Fe 3 O 4 content. [ABSTRACT FROM AUTHOR]

In this study, data of La3+, Gd3+ and Y3+ were carefully selected from the published thermodynamic data base, and were then added to the thermodynamic database of the MINTEQA2 procedure. The species of rare earth elements (REEs, La, Gd, Y) ina nutrient solution were calculated out by MINTEQA2 procedure. The results showed that the precipitation of REEs would take place when the pH was greater than 7.5. Meanwhile, the species of light (La3+) medium (Gd3+) and heavy (Y3+) REEs withSO42- were calculated using MINTEQA2. The effects of sulfate on the bioavailabilities of three REEs in wheat (Triticum) were investigated by experiments on culture. The results showed that bioaccumulation of La3+ and Gd3+ in roots was inhibited after adding SO42-to the nutrientsolution containing 2.0 mg L-1 REE, but Y3+ was promoted. Only Gd3+ became increasingly bioaccumulated in tops (stem and leaves) after adding SO42- to three REE solutions. Kinetic experimental results indicated that bioaccumulation values of REEs in roots fit the linear growth equation (correlation coefficients were higher than 0.94) in nutrient solution containing 2.Omg L-1 REE + 0.01 mol L-1 SO42-, and the high bioaccumulation values of REEs in the tops (stem and leaves) during the initial culture time were higherthan those in the following few days. The species of REEs with sulfate and the bioavailabilities of REEs had no obvious correlation. [ABSTRACT FROM AUTHOR]