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Ion-adsorption clays (IAC) are alumino-silicate ores, considered an essential source of heavy rare-earth elements (REE). With the increasing discovery and exploitation of IAC deposits, the present work sought to evaluate different methods of solubilization of REE through the use of different concentrations of inorganic acids (H2SO4, HCl, and HNO3), as well as different concentrations of ammonium sulfate and lactic acid. According to the results, the sulfuric acid solution favored the solubilization of both La3+ and Sm3+ elements. The solubilization of REE in the presence of ammonium sulfate showed no significant differences as a function of the leaching time but favored the solubilization of Y3+ and Tb3+. More efficient solubilization of Sm3+ was observed with the addition of lactic acid at a concentration of 30 g L-1, leading to 90% (4.5 ppm) of Sm3+ extraction. The solubilization of La3+ was favored by the contact time, with higher Sm3+ extraction yields in 14 days of leaching. [ABSTRACT FROM AUTHOR]

Deep‐sea sediments around Minamitorishima Island in the western North Pacific Ocean record the depositional environment in the central to western North Pacific since the late Cretaceous. Previous studies on the bulk chemical composition of deep‐sea sediments in this area have revealed that the sediment column can be divided into five chemostratigraphic units with at least three intercalated layers enriched in rare‐earth elements. However, the end‐member components and their changes in abundance, which indicate compositional variation, as well as the environmental factors affecting them, remain unclear. Here, we report the bulk chemistry, including newly analyzed 87Sr/86Sr ratios of the sediments, seafloor Mn nodules, and fish teeth collected from the deep‐sea basin around Minamitorishima Island, to identify the end‐member components of the sediments. Our results suggest that the pelagic sediments in the study area are mainly composed of terrigenous components, hydrogenous Mn oxides, biogenic calcium phosphate, and volcanic materials. The combination of Sr isotope modeling and bulk chemistry revealed that the input of volcanic materials has increased twice, which might be Izu‐Bonin‐Mariana tephras of the latest Eocene to Oligocene explosive volcanism at the later event but is unclear at the earlier event. The provenance of terrigenous materials has changed from North America to East Asia. The bulk sediment chemostratigraphy around Minamitorishima Island could have resulted not only from the local environmental changes in the pelagic realm, but also from volcanism around the Pacific Ocean and the northwestward movement of the area due to the Pacific plate motion. Plain Language Summary: Deep‐sea sediments around Minamitorishima (Marcus) Island in the western North Pacific Ocean record the depositional environment in the Pacific pelagic area for the past 75 million years. They comprise eight types of sediments with different chemical features, including three layers enriched in rare‐earth elements. However, the origin of the different types of sediments in this region remains unclear. We measured the chemical compositions and Sr isotope ratios of the bulk sediments, Mn nodules, and fish teeth collected from the sediments to reveal the source materials of the sediments from the top layer to ∼12 m below the seafloor. The results demonstrate that the source materials are composed of four components: dust from the continents, Mn oxides from seawater, fish teeth and bones, and volcanic components. Additionally, the sediment records indicate that long‐term changes have occurred in the origins of volcanic materials and dust. We suggest that the input of volcanic materials, the changes in the dust source from America to Asia, and the Pacific plate motion may have significantly affected the deep‐sea sediments in the study area. Key Points: 87Sr/86Sr of bulk sediment, Mn nodules, and fish teeth in the western North Pacific was analyzed to identify sedimentary end‐membersBulk sediments consisted of dust, fish debris, and Mn oxides with volcanic componentsThe introduction of volcanic components from the Izu‐Bonin‐Mariana arc increased in the latest Eocene [ABSTRACT FROM AUTHOR]

Objectives. This study aimed to predict the limits of substitution and stability of luminescent materials based on low-temperature modifications of solid solutions (spatial group P21/c) with lutetium oxyorthosilicates (Lu1−xLnx)[(SiO4)0.5O0.5], where Ln represents the rare-earth elements (REEs) of the La–Yb series.Methods. The V.S. Urusov’s crystal energy theory of isomorphous substitutions and a crystallochemical approach in the regular solid solution approximation were used to calculate the energies of the mixing (interaction parameters) of the solid solutions.Results. Using the V.S. Urusov’s theory, we calculated the energies of mixing (interaction parameters) in the systems under study. The dependences of the decomposition temperatures of solid solutions on the REE number and composition (x) were obtained and used to create a diagram of the thermodynamic stability of the solid solutions, allowing us to predict the substitution limits depending on the temperature or determine the decomposition temperature using the given substitution limits.Conclusions. The results of the study can be useful when choosing the ratio of components in matrices (host materials) and the amount of the activator (dopant) in the new luminescent, laser, and other materials based on low-temperature modifications of solid solutions of “mixed” REE oxyorthosilicates (Lu1−xLnx)[(SiO4)0.5O0.5].

Relevance of the research is caused by the necessity of obtaining up-to-date data on concentrations of chemical elements in the «water–soil–plant» system on the near-entry spot of tunnel 504 of «Degelen» site at the former Semipalatinsk Test Site. During flooding in spring, elements may be carried out beyond tunnel 504. The main aim of the research is to study spatial distribution of chemical elements in the «water–soil–plant» system in the streamflow of tunnel 504. To achieve this goal, the following tasks were set: 1) determine concentration levels of chemical elements in water; 2) study concentration levels of chemical elements in soil; 3) identify features of chemical elements accumulation in plants of tunnel 504. Methods. The ultimate composition of water was determined by inductively-coupled plasma mass-spectrometry (Elan 9000 «Perkin Elmer SCIEX»), inductively-coupled plasma atomic emission spectrometry («iCAP 6300 Duo» Thermo Scientific). The analysis of such indicators as total mineralization, the content of sulfates, hydrocarbonates, chlorides, calcium, magnesium and sodium was carried out using titrimetric, colorimetric, potentiometric techniques in accordance with GOST. Results. The analysis of the data obtained for water showed a high content of such elements as Li, Be, Al, Mn, Zn, Rb, Sr, Cd, Cs, La, Се, U the average content of which exceeds the clarke several times for groundwater of the arid climate (sulfate water). The excess of maximum permissible levels of such elements as Be (2800 MPC), Mn (260 MPC), Al (76 MPC), U (70 MPC) and Cd (50 MPC) has been registered for water. According to the latest data, the content of such elements as Li, Be, Al in water was found to increase by 2 times whereas that of Co, Ni and Cu – by dozens of times. Spatial distribution of elements of interest in soil of tunnel 504 is non-uniform. Most of elements are concentrated in soil to the north of the streamflow bed. An elevated content of such elements as Be, Mn, Cu, Zn, Мо, Cd, Cs, Pb and U was detected in this area exceeding the clarke of lithosphere. The high index of lithosphere clarke value excess was found for uranium concentration (1000 times). Comparison of findings for contaminated areas with values of maximum permissible concentrations of chemical elements in soil showed the excess for Pb (26 MPC), Mn and Cu (9 MPC). Chemical composition of water and soil of tunnel 504 is unique by the content of rare-earth elements. The average content of REE in water exceeds the clarke by thousand times in ground water of the arid climate and STS ground water. The excess of the maximum permissible concentration level of samarium was observed in water. Predominance of light REE is characteristic, with a pronounced cerium-lanthanum feature. This fact shows that metals in water originate from natural sources. For most plant species of tunnel 504 an elevated content of Be, Сd, Cs, Pb, U and a number of REE was detected in the contaminated area. Concentrations of elements of interest in such plant species as reed and bluejoint in areas being compared, varied insignificantly which is apparently attributed to some physiological and biochemical mechanisms that impede the intake. Based on the above, one can conclude that spatial distribution of elements at tunnel 504 is first of all related to chemical elements carried out by tunnel water. About ten elements exceeding clarke values and maximum permissible levels were detected in water of tunnel 504.

Objectives. The extraction and separation of rare-earth metals is a complicated process that requires a multidisciplinary and detailed investigation. Liquid-liquid extraction with the use of surfactant, along with the thermodynamic analysis of the parameters is considered a promising approach. The extraction and separation of rare-earth metals from low-concentration solutions represents an attractive research opportunity. The extraction of europium(III) from nitric acid solutions in the form of dodecyl sulfates has been experimentally studied. This work focuses on the study of fundamental and alternative sources of rare-earth metals and their extraction and separation.Methods. The extraction was performed on a top drive ES-8300 D equipment for 30 min at about 700 rpm. Infrared spectroscopy (Nicolet 6700 spectrometer) was used to determine the type of salts extracted into the organic phase. Extraction was studied in solutions with single cations and with a combination of the target element and interfering cations. For the latter, the concentrations of extracted elements in the aqueous phase were determined by optical emission spectroscopy with inductively coupled plasma on an ICPE-9000 (Shimadzu) spectrometer. The spectrometer was calibrated using standard samples for ICP CertiPUR (Merck).Results. The dependence of the distribution and separation coefficients of rare-earth metals during extraction on the pH value of the aqueous phase at equilibrium was investigated. Moreover, the form in which the elements are extracted was analyzed based on thermodynamic parameters. The minimum concentration of the target component in the aqueous phase was observed at pH 4.0. In general, the dependence of the distribution coefficient on the pH value of the medium is poorly expressed over the entire range of the pH range of the water phase. Based on the spectra of spent and pure isooctyl alcohol, it was concluded that europium dodecyl sulfates are extracted into the organic phase as Eu(C12H25OSO3)3 solvates.Conclusions. The extraction of europium(III) from nitric acid solutions in the form of dodecyl sulfates was demonstrated. The advantages of the proposed method are the possibility of selective extraction of the target component from dilute solutions and the use of an easily available surfactant (sodium dodecyl sulfate). The efficiency of extraction of europium dodecyl sulfates was maximal in the pH range from 2.0 to 7.5, which reflects a weak dependence on the acidity of the aqueous phase. In addition, in the highly alkaline pH region, the extraction efficiency is reduced.

The article provides new data on geochemistry and mineralogy of rare-earth elements (REE) in rocks of structural-material complexes of the Bashkir megaanticlinorium, which underwent metamorphic transformations of various nature: contact metamorphism (Suran section); syn- and postgenetic contact-dislocation metamorphism (Shatak complex) and hydrothermal metamorphism (Uluelga-Kudashmanovo zone). It has been established that when a magmatic melt is exposed to sediments, the latter are enriched with REEs with the formation of rare earth minerals (monazite, allanite, xenotime et al.). The study of the chemical composition of monazites and allanites showed that all variations of oxides in the composition of the former are due to isomorphous Ce-Ca-Th substitutions in the structure of minerals, but redistribution of these elements was an independent process characteristic of each structural-material complex. The study of allanites made it possible to establish the presence of isomorphism according to the Ca↔Ce, La, Nd principle, as well as the sharp difference between the characterized minerals in the amount of MgO, Fe* and MnO from analogues from other regions, which indicates the presence of a regional component in the chemical compositions of minerals altogether, geotectonic settings of mineralization formation. The temperature regimes of mineral-forming processes with metamorphic transformations of rocks calculated from chlorite and muscovite compositions (344-450°C – Suran section, 402-470°C – Shatak complex, 390-490°C – Uluelga-Kudashmanovo zone) indicate the possibility of stable coexistence of the association monazite-allanite. It was established that when a magmatic melt on the sedimentary substrate of the frame, the lanthanides enrich the exocontact rocks with the formation of newly formed REE-mineral associations. At the same time, the processes of formation of rare-earth mineralization are largely determined by the physicochemical parameters and thermobaric conditions of the accompanying and subsequent metamorphism.

Relevance of the research. Information on composition, ice content and geochemical characteristics of frozen rocks is necessary for exploration of oil and gas condensate fields of Yamal, Gydan and Taimyr. Among the factors determining the tundra landscapes ecology of the cryolithozone, underground ice and their melting have great importance. The hydrochemical composition and rare-earth elements content in syngenetic ice wedge retain the information on the moisture sources and conditions of their formation. The main ions correlation and rare-earth elements distribution in the ice composition can be used to estimate the influence of such natural factors as precipitation, sea and volcanic aerosols and anthropogenic pollution. The main aim of the research is to identify chemical elements sources and to assess the impact of the ice type on hydrochemical composition and rare-earth elements distribution in different genetic types of ice – wedge, seasonal and firn ice. Objects: ice wedge, sediments rocks, seasonal ice, surface water, taken in expeditions Earth Cryosphere Institute, Tyumen scientific centre SB RAS in 2009–2014. Methods of chemical research: inductively coupled plasma mass spectrometry, atomic absorption spectrometry, emission photometry, chromatography. Results. It is established that marine and continental aerosols influenced the chemical composition of ice wedge studied in the coastal zone of the key areas of Belyj island, Sibiryakova island, Western Yamal and Western Taimyr. Fresh and ultrafresh syngenetic ice wedge is formed by freezing melt water, which contains snow-sorbed sea aerosols – suspended in the atmosphere solid and liquid particles. Ice wedge in the lake Sokhonto area long-distanced from the sea has no signs of marine influence according to the main ions content. Ice wedge with mineral inclusions was formed not only due to snow melt water with aerosols of continental origin, but also due to the suprapermafrost water. It was found out that lanthanide content in water-soluble form has increased in comparison with both сlark values and the content in the modern surface ice. In the most of examined syngenetic ice wedge the participation of marine aerosols is confirmed taking into account the cerium anomaly. Moreover according to the distribution of rare-earth elements the correlation between light and heavy rare-earth elements typical for ice wedge, equal to 0,9, and correlation between lanthanum and the other lanthanides, equal to 0,2, are observed. Sea ice inherits the mineralization and composition of sea water. Lake ice varies in depth and reflects seasonal changes in hydrochemical composition of ice and increases in concentration of marine aerosols in the snow covering the lake ice. Firn ice of the polar Urals has a very low mineralization, there are no impurities of sea aerosol. The natural mechanism of rare earth elements accumulation in water-soluble form in combination with iron, thorium and yttrium is implemented in ice wedge of the Holocene and Neopleistocene. Melting out ice wedge may lead to the flow of rare-earth elements in the surface water.

Research subject. 14 samples of limestone and one sample of carbonate-siliciclastic rock from siliciclastic-carbonate deposits of the Upper Riphean Uk Formation (the Southern Urals) were studied.Methods. Mineral and chemical composition of the samples were determined; the main tool for detecting the concentrations of trace elements was the ICPMS method. X-ray diffraction analysis was carried out using a Shimadzu XRD-7000 diffractometer, the content of major (rock-forming) oxides in bulk samples was established by X-ray fluorescence spectrometry on the SRM-35 and Shimadzu XRF 1800 spectrometers. Microelement composition of bulk samples and acidic leachates obtained with using acetic (10%), nitric (36%) and hydrochloric (17%) acids was determined on a Perkin Elmer ELAN 9000 spectrometer.Results. The distribution of lithophile, rare-earth and a number of other elements (Sr, Ni, U) both in bulk samples and in acidic leachates was analyzed. The main carrier phases of these elements were revealed.Conclusions. 1. The use of any listed acids leads to the non-carbonate component entering the solution, including contamination of the “carbonate” leachates by lithophile elements. In particular, a transition Rb, Zr, Li, Th, Ti, Sc to leachates was noted. This process is most active in nitric and hydrochloric acids, less intensive in acetic acid. 2. Among the carriers of rare earth elements (REE) in the studied rocks are clays (1), accessory minerals (2), including phosphate-bearing grains, secondary carbonate phases represented by dolomite and, possibly (3), finely disseminated iron and manganese (oxy)hydroxides (4). It is assumed that the REE pattern in limestones is determined by the content of the epigenetic dolomite. The contribution of lanthanides bound in the sedimentary calcite crystal lattice in the total REE pattern is rather large only in relatively “pure” limestones. However, the use of acids with such concentrations did not allow to obtain a leachate, which the REE pattern with high probability corresponds to the distribution of REE in the Uk time seawater. But acetic acid is more effective for achieving this goal than the others. 3. In addition to Sr, sedimentary calcite also contains Ni and U.

Abstract Deep‐sea sediments around Minamitorishima Island in the western North Pacific Ocean record the depositional environment in the central to western North Pacific since the late Cretaceous. Previous studies on the bulk chemical composition of deep‐sea sediments in this area have revealed that the sediment column can be divided into five chemostratigraphic units with at least three intercalated layers enriched in rare‐earth elements. However, the end‐member components and their changes in abundance, which indicate compositional variation, as well as the environmental factors affecting them, remain unclear. Here, we report the bulk chemistry, including newly analyzed 87Sr/86Sr ratios of the sediments, seafloor Mn nodules, and fish teeth collected from the deep‐sea basin around Minamitorishima Island, to identify the end‐member components of the sediments. Our results suggest that the pelagic sediments in the study area are mainly composed of terrigenous components, hydrogenous Mn oxides, biogenic calcium phosphate, and volcanic materials. The combination of Sr isotope modeling and bulk chemistry revealed that the input of volcanic materials has increased twice, which might be Izu‐Bonin‐Mariana tephras of the latest Eocene to Oligocene explosive volcanism at the later event but is unclear at the earlier event. The provenance of terrigenous materials has changed from North America to East Asia. The bulk sediment chemostratigraphy around Minamitorishima Island could have resulted not only from the local environmental changes in the pelagic realm, but also from volcanism around the Pacific Ocean and the northwestward movement of the area due to the Pacific plate motion.

The growing demand for rare-earth elements and yttrium (REY) in modern technologies has resulted in the systematic depletion of primary ores. For this reason, research is being conducted around the world on alternative sources of rare-earth elements, e.g., on the possibilities of recovering REY from coal waste or coal combustion. The article presents the results of comprehensive tests of the fuel—hard coal, and high-temperature HTA ash, fly ash, and bottom ash. Examined samples were taken from a Polish power plant. In the tests, fuel quality parameters were determined in accordance with the standards; microscopic observations in reflected and transmitted light, as well as a scanning electron microscope (SEM/EDS), were used, and chemical and phase composition were determined using ICP-MS and XRD methods, respectively. The distribution of REY between these ashes was analyzed. Their suitability as alternative sources of REY was assessed. The obtained results showed that the process of hard coal combustion in pulverized coal boilers influenced the geochemical differentiation of REY elements in energy waste. This differentiation is manifested by higher concentrations of REY and critical elements in the fly ash than in the bottom ash. The obtained values of the Coutl prospective coefficient made it possible to classify the analyzed fly and bottom ashes as prospective REY raw materials.

The concentrations of rare-earth elements (REEs) in technogenic (mine and sludge) and river waters of the Kavalerovsk and Dal'negorsk Districts of the Far East were estimated. It was shown that the mine waters of the Dubrovskoe deposit, Kavalerovsk District (mineralization 770 μg/L) are mostly enriched in REEs. Their highest concentrations were found in the sludge waters of the old tailing dump of the Krasnorechensk concentration plant (KCP), Dal'negorsk District (mineralization 1139 μg/L). In the immediate vicinity of the KCP old and new tailings, the Rudnaya River was found to be polluted with REEs. Since REEs are related to sulfide minerals, they can be extracted by the repeated processing of the wastes of the old and new KCP tailing dumps. [ABSTRACT FROM AUTHOR]

Samples of ore and gravity concentrate from the Algama zirconium occurrence were studied. Concentrations of rare-earth elements (REE), and rare and noble metals were determined. The REE content is 200–300 g/t in the ore and reaches 400 g/t in the gravity concentrate. REE distribution patterns show a clear negative Ce anomaly and MREE and Y predominance. The ore and the concentrate have elevated Hf, W, U, Ta, Au, and Pt contents. Their source is the ancient weathering crust developed after ultra-alkaline rocks of the Ingili massif. The presence of a buried weathering crust enriched in valuable components is inferred in the studied area. [ABSTRACT FROM AUTHOR]

The kinetics of sorption and regeneration from industrial nitric acid–phosphoric acid solutions with the use of ion-exchange resins like KU-2 has been studied for both individual rare-earth elements (REEs) and their mixtures with the measurement of sorption and regeneration isotherms. The high rate of the mentioned processes enables the use of these resins in pulsed columns with a fluidized resin bed. It has been shown that the efficiency of sorption columns can be improved by decreasing the volume of equipment and a one-time sorbent load. It has been established that the specific solution flow rate (10–12 m3/(m2 h)) in a pulsed column is 4–5 times higher than in standard columns with a continuous sorbent bed. The use of pulsed columns provides a six- to sevenfold decrease in the one-time sorbent load. The measured data of on the sorption of REEs on sulfocationites may be used for the design of industrial pulsed columns. [ABSTRACT FROM AUTHOR]

In this work, for the first time, the Plasma-enhanced chemical vapor deposition (PECVD) method was used for the direct one-stage synthesis of the IR-transparent amorphous chalcogenide films of the binary As–S system doped with ions of the rare-earth element—ytterbium. RF (40 MHz) inductively coupled low-temperature non-equilibrium plasma discharge was utilized for the initiation of chemical interactions between precursors. High-pure arsenic monosulfide, sulfur, and elemental ytterbium were the initial substances. The reactive species formed in the gas phase were studied in-situ by the Optical emission spectroscopy technique. It was proved that the PECVD method allows fabrication of the film in the wide range of Yb concentrations: the ytterbium content in the films was varied in the range of 1–7 at%. Dependence of structural, optical properties, and intensity of the photoluminescence on the composition of the films was also studied. [ABSTRACT FROM AUTHOR]

Cerium(IV) hydrogen phosphate Ce(PO4)(HPO4)0.5(H2O)0.5 has been prepared by hydrothermal treatment of gels obtained by hydrolysis of cerium-containing phosphoric acid solutions. The obtained compound and the products of its heating in a wide temperature range have been analyzed by X-ray powder diffraction analysis, IR spectroscopy, mass spectrometry of gaseous thermolysis products, and scanning electron microscopy. Thermal decomposition of the compound at temperature up to 1200°С has been refined. In particular, it has been shown that crystalline cerium(III) phosphate (CePO4) forms upon heating of Ce(PO4)(HPO4)0.5(H2O)0.5 in air even at 600°C. [ABSTRACT FROM AUTHOR]

In this study, AA6061/AA6061 and AA6061/alumina were directly brazed with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys at 530 °C for 10 min without the use of flux. The addition of titanium and rare-earth elements into Al10.8Si10Cu alloy effectively improved the bonding shear strengths of AA6061/AA6061 and AA6061/alumina joints. The highest joint shear strengths were 61.1 and 19.2 MPa, respectively. The Al10.8Si10Cu filler alloy without titanium and rare-earth elements could not wet on the alumina and caused failure of the AA6061/alumina joint. The shear strengths of the AA6061/AA6061 and AA6061/alumina joints both strongly depended on the active element addition. Due to the high chemical activity of the rare-earth elements, they formed AlLa between the Al10Si10Cu4Ti0.1RE filler alloy and alumina. The addition of rare-earth elements into Al10Si10Cu4Ti filler alloy resulted in significant enhancement of the average bond strength of AA6061/alumina joints, from 8.0 to 14.8 MPa. [ABSTRACT FROM AUTHOR]

Due to the wide application of rare-earth elements (REEs) in the last decades, lanthanum has increasingly entered the environment and has gradually accumulated in the human body through the food chain. Lanthanum is worth paying attention in terms of food safety. Although the genotoxicity of lanthanum has been studied in vitro, data on its DNA damage in vivo rodent are limited, moreover, which have also presented some controversy. This study aimed to conduct an in vivo rodent alkaline comet assay, and as a companion test to the lanthanum nitrate carcinogenicity test. We conducted an oral gavage experiment for 180 days (26 weeks) to test for the persistence of DNA damage of long-term low-dose accumulation of lanthanum nitrate (12.5, 25, and 50 mg/kg body weight), in F1 hybrid C57-ras transgenic mice (CB6F1) by using alkaline comet assay in the blood and liver. The comet assay revealed that all the tested concentrations of lanthanum nitrate did not induce DNA damage in any of the tissues investigated, whereas DNA damage was induced in the positive control group. These results could indicate that lanthanum nitrate can accumulate in tissues and organs of the mice after exposure, and does not possess DNA damage in C57-ras transgenic mice after repeated treatments at oral doses up to 50 mg/kg·BW for 26 weeks; also, it did not cause pathological changes in the liver of the mice. [ABSTRACT FROM AUTHOR]

The article presents the results of chemical analysis, microstructural studies, hardness measurements of the deposited layers obtained by manual arc welding through the use of the welding-depositing materials containing rare-earth and rare elements from the Tomtor field and electrodes covered with UONI 13/55. The positive effect of the modifying additive with REM on the formation of a crushed structure in the zone of the metal deposit and at the fusion boundary is indicated. A slight increase in hardness in the metal deposit alloyed with rare earth metals is detected. [ABSTRACT FROM AUTHOR]

Toxicokinetic models are useful tools to better understand the fate of contaminants in the human body and to establish biological guidance values to interpret biomonitoring data in human populations. This research aimed to develop a biologically-based toxicokinetic model for four rare earth elements (REEs), cerium (Ce), praseodymium (Pr), neodymium (Nd) and yttrium (Y), and to establish biomonitoring equivalents (BE) serving as biological guidance values. The model was constructed using physiological data taken from the literature as well as new experimental kinetic data. These new data indicated that REEs readily disappeared from blood and accumulated mostly in the liver; excretion occurred mainly through feces although a small fraction was eliminated in urine. To properly reproduce the observed kinetics, the model was represented as 19 compartments, which include main tissues and their components (such as retention by macrophages) supplied by blood, as well as routes of excretion. The transfer coefficients between compartments were determined numerically by adjustments to experimental data. Simulations gave good fits to available experimental kinetic data and confirmed that the same model structure is applicable to the four elements. BEs of 0.3 µg/L of Pr and Nd were derived from the provisional RfD of 0.5 mg/kg bw/day established by the U.S. EPA. These BEs can be updated according to new reference dose values (RfD). Overall, the model can contribute to a better understanding of the significance of biological measurements and to the inference of exposure levels; it can also be used for the modeling of other REEs. The BEs will further allow rapid screening of different populations using biological measurements in order to guide risk assessments.

Supplementary lighting of specific wavelengths can be used for inducing morphological and physiological responses in different crops, ultimately improving yield and quality. Based on this approach, new greenhouse covering materials are being developed in order to improve the use of sunlight in horticulture. These new-generation greenhouse coverings may incorporate light spectrum modulation agents or fluorescent additives which convert solar UV radiation into visible light. In this work, we tested the agronomical and physiological response of lettuce grown under a greenhouse covered with poly-methyl-methacrylate (PPMA) panels doped with a blend of the rare-earth inorganic material with a photo-luminescent effect. The doped greenhouse elicited a 36% increase in lettuce yield compared to the undoped greenhouse. Chlorophyll and carotenoid content, as well as antioxidant activity and ascorbic acid content, were not affected by greenhouse cover, but the doped panels induced a 22% reduction in total phenolics and a 14% increase in nitrate content in leaves. The greenhouse covering materials also affected the photochemistry of photosynthesis, as the daily fluctuations in both the effective quantum yield (ΦPSII) and the electron transport rate (ETR) were attenuated under the doped greenhouse. Non-photochemical quenching (NPQ) was closely related to the light environment in all experimental conditions, with the highest values at 14:00 h. Our results showed that the red-supplemented light spectrum under the doped greenhouse cover contributed to increased plant growth and yield, with a corresponding effect on the physiology of photosynthesis.

Rare-earth elements (REEs) are in all respect a class of new contaminants that may have toxic effects on organisms and microorganisms and information on their interactions with natural ligands should be of value to predict and control their diffusion in natural environments. In the current study, we investigate interactions of tripositive cations of praseodymium, europium, holmium, and thulium with harzianic acid (H2L), a secondary metabolite produced by selected strains of fungi belonging to the Trichoderma genus. We applied the same techniques and workflow previously employed in an analogous study concerning lanthanum, neodymium, samarium, and gadolinium tripositive cations. Therefore, in the current study, HPLC-ESI-HRMS experiments, circular dichroism (CD), and UV-Vis spectrophotometric absorption data, as well as accurate pH measurements, were applied to characterize bonding interactions between harzianic acid and Pr3+, Eu3+, Ho3+, and Tm3+ cations. Problems connected to the low solubility of harzianic acid in water were overcome by employing a 0.1 M NaClO4/(CH3OH + H2O 50/50 w/w) mixed solvent. For Pr3+, Ho3+, and Tm3+, only the mono complexes PrL+, HoL+, and TmL+ were detected and their formation constant determined. Eu3+ forms almost exclusively the bis complex EuL2− for which the corresponding formation constant is reported; under our experimental conditions, the mono complex EuL+ is irrelevant. Combining the results of the present and previous studies, a picture of interactions of harzianic acid with rare-earth cations extending over 8 of the 17 REEs can be composed. In order to complement chemical information with toxicological information, a battery of bioassays was applied to evaluate the effects of praseodymium, europium, holmium, and thulium tripositive cations on a suite of bioindicators including Aliivibrio fischeri (Gram-negative bacterium), Raphidocelis subcapitata (green alga), and Daphnia magna (microcrustacean), and median effective concentration (EC50) values of Pr3+, Eu3+, Ho3+, and Tm3+ for the tested species were assessed.

The modification of functional materials with rare-earth elements (REEs) for different purposes by the low-temperature extraction–pyrolysis method has been carried out. Luminophors and magnetic and biomedical materials have been synthesized, and their compositions and properties have been studied. It has been established that the introduction of modifying additives (REE ions) could significantly improve the useful properties of the fabricated functional materials. [ABSTRACT FROM AUTHOR]

The process of sorption separation of uranium and REE after acid leaching of uranium-phosphorus-rare-earth chemical concentrate onto a modified granular sorbent based on cellulose phosphate (MGCP) was studied. It was found that MGCP efficiently absorbs U(VI) from solution, while REEs remain together with phosphorus and fluorine in the raffinate. The dependences of the exchange capacity of MGCP for U(VI) and REE on the volume of the passed filtrate were determined. The dynamic capacity of the sorbent for U(VI) reaches 100 mg/g, and the degree of extraction of U(VI) from the solution exceeds 94%. It has been shown that it is expedient to desorb uranium with a (NH4)2CO3 solution at a temperature of 50 ± 2°C, providing preliminary oxidation of U(IV) to U(VI) directly on the sorbent with a 0.5% HNO3 solution containing 2% NaNO2. With sorption of U(VI) on MGCP, the stage of extraction purification from REE in the production of triuranium octoxide may be excluded. The possibility of sorption separation of REE from radioactive isotopes on MGCP was determined. The sorbent capacity for REE is 70 mg/g. [ABSTRACT FROM AUTHOR]

Removal of volatiles at 243 K from solutions of completely dissolved LnF3 (Ln=La–Dy and Y) and XeF2 (molar ratio 1 : 3) in anhydrous HF acidified with an excess of BF3 resulted in [Ln(XeF2)3](BF4)3 salts. Isolated solids are stable at 298 K and give similar Raman spectra. [La(XeF2)3](BF4)3 crystallizes in the monoclinic space group C2/m at 150 K. Each La atom is coordinated with three XeF2 ligands. Six F atoms provided by six bridging BF4 units, that connect the neighboring La3+ atoms into columns, complete the nine‐fold coordination of each La atom. Chemical reactions carried out in the same way but with molar ratio LnF3 : XeF2=1 : 1 yielded [Ln(XeF2)](BF4)3 salts (La ‐ Nd). Crystal structures of La and Nd salts are isotypic and crystallize in the monoclinic space group P21/m at 150 K (La) and 200 K (Nd). Each Ln center is coordinated by nine fluorine atoms provided by eight BF4 units and one XeF2 ligand. The BF4 groups interconnect the Ln atoms into two‐dimensional layers. With molar ratio LnF3 : XeF2=1 : 2 and the same synthetic approach, only La yielded [La(XeF2)2](BF4)3 salt. Prolonged pumping of [Ln(XeF2)n](BF4)3 (n=3, 2, 1) at 298 K or attempts of the isolation at 298 K resulted in products with lower content of XeF2 or in mixtures of various products. In addition to [Ln(XeF2)](BF4)3 and LnF3/BF3 products, the [Ln(XeF2)]F(BF4)2 salts (Ln=La, Nd, Sm, Eu, Tb, Dy and Y) also formed. The crystal structures of LaF(HF)(BF4)2 and LaF(BF4)2 side products were determined. [ABSTRACT FROM AUTHOR]

[Display omitted] • COOH-functionalized carbon derived from ZIF-8 was applied for Nd3+ adsorption. • A high maximum adsorption capacity of 175 mg/g was achieved after 4 h. • 77% of Nd3+ selectivity among other metal ions was achieved. • Adsorption was due to coordination bonding between the Nd3+ ions and COOH. • The adsorbent was highly recyclable after a simple acid solution washing. A porous graphitic carbon was obtained via the pyrolysis of a zeolite imidazolate framework (ZIF-8) under Ar atmosphere. Then, the carbon was functionalized with carboxylic groups and applied for separation of neodymium ions (Nd3+) from water. The adsorbent (denoted as C-ZDC) was characterized by X-ray diffraction, N 2 adsorption–desorption isotherms, infrared spectroscopy, X-ray photoelectron spectroscopy, scanning and transition electron microscopies, thermogravimetric analysis, and Boehm titration. A practical adsorption equilibrium was attained within 4 h, and the adsorption isotherm at 25 °C revealed a maximum adsorption capacity of 175 mg/g, which is one of the highest values reported for different kinds of adsorbents. The adsorption kinetics and equilibrium isotherms were modeled, and the selectivity for Nd3+ over other metal ions was examined. From the effect of solution pH on the adsorption and material characterization results before and after adsorption, the high adsorption capacity of C-ZDC was ascribed to the formation of coordination bonds between Nd3+ ions and the –COOH groups. Further, the material was reusable for at least four adsorption–desorption cycles after a simple step of acid washing. [ABSTRACT FROM AUTHOR]

The features of distribution are studied and a complex technology for the separation of samarium, europium, and gadolinium is proposed. This technology involves the initial isolation of 70–80% of the europium concentrate by extraction with organophosphorus acids, which makes it relatively easy to obtain pure compounds of samarium and gadolinium in subsequent operations. At the last stage, europium is isolated by chemical reduction and the captured samarium and gadolinium are returned to the beginning of the process. The content of the main substance in the resulting oxides is 99.9–99.99 wt %. [ABSTRACT FROM AUTHOR]

This article is devoted to the issues of aromatic hydrogenation reactions on supported palladium catalysts: adsorption on palladium catalysts, models of the Pd surface and the location of adsorption centers, features of hydrogenation of aromatic nitro compounds over palladium catalysts with additives of rare-earth elements. Palladium catalysts for hydrogenation of nitro groups in nitro compounds with different functional groups are described. The article discussed theoretical and experimental aspects of data from literature and patent sources. The experimental results of the authors of this article concerning selective hydrogenation of 4,4’-dinitrostilbene-2,2’- disulfonic acid to 4,4’-diaminostilbene-2,2’-disulfonic acid are also shown. Pd-Cu/sibunite was used for selective obtaining 4,4’-diaminostilbene-2,2’-disulfonic acid in water. The formation on the surface of mixed active centers of the type of solid solutions of the Cu3Pd composition with a particle size of 5 nm and massive Pd clusters of 100 nm is established, which cause sufficient uniformity of both the surface and the adsorbed hydrogen. This is probably the reason for the high selectivity of the Pd-Cu/sibunite catalyst in the hydrogenation of 4,4’-dinitrostilbene-2,2’- disulfonic acid. A highly selective Pd-Cu / sibunite catalyst has been developed, the optimal conditions for the process (temperature and pressure of hydrogen, solvent) have been determined, which make it possible to obtain the target amine, 4,4’-diaminostilbene-2,2’-disulfonic acid, up to 91-92%. The optimal composition of the catalyst is stable when hydrogenating 7-8-fold portions of 4,4’-dinitrostilbene-2,2’-disulfonic acid. [ABSTRACT FROM AUTHOR]

The crystallographic structure of rare-earth-contained (Mo 2/3 R 1/3) 2 AlC (R = Gd, Tb, Dy, Ho, Er and Y) i- MAX phases have been verified to be C 2/ c monoclinic. The magnetic behaviors are varied from antiferromagnetism to non-linear ferromagnetism from R = Gd to Ho in (Mo 2/3 R 1/3) 2 AlC i- MAX phases due to variant R - R interactions. The capacitance of Mo 1.33 C@ R MXene derived from different (Mo 2/3 R 1/3) 2 AlC precursors varies from 170 F/g to 228 F/g but can be double by hydrazine monohydrate treatment. The highest one of 431 F/g up to now has been achieved in Mo 1.33 C@Y-HM MXene, which is caused by the increased fraction of critical -O group evidenced by XPS spectra. Our results illustrate the promising applications in supercapacitor of Mo 1.33 C MXene derived from R-contained (Mo, R) 2 AlC i- MAX phases. [Display omitted] [ABSTRACT FROM AUTHOR]

Unit cell parameters acal(x) and X-ray densities ρX(x) are calculated in terms of a model that accounts for ionic bonding, additivity of properties, and dimensional factor upon aliovalent substitutions for 45 new nonstoichiometric phases Sm1 −xRxF2 +x, Eu1 −xRxF2 +x and Yb1 −xRxF2 +x (R = La−Lu, Y) based on SmF2, EuF2, and YbF2 fluorite matrices (the fluorite CaF2 type). A comparison of the calculated unit cell parameters acal(x) and the experimental a(x) values available in the literature for these phases shows satisfactory match. Concentration-dependent relationships acal(x) and ρX(x) can be used for monitoring the composition of melt-grown Sm1 −xRxF2 +x, Eu1 −xRxF2 +x, and Yb1 −xRxF2 +x crystals in studies of their defect structures and fundamental properties. [ABSTRACT FROM AUTHOR]

• Evaluation of 2D and 3D surface roughness parameters was conducted utilizing optical profilometry. • The proximity coefficient (Ci) is a metric that allows for the consolidation of several responses into a single number. • TOPSIS – ANOVA hybrid approach used to attain optimal process parameters. • Responses are greatly influenced by cut depth and sample preparation process. The purpose of this study is to examine the impact of various milling parameters and sample preparation methods on the end-milling of EV31A Mg alloy under as-cast, T4, and T6 heat-treated conditions. The test specimens were prepared through stir-casting and heat-treated according to T4 and T6 conditions. The CNC vertical milling machine with the HSS tool was used for the end-milling process based on Taguchi's L9 orthogonal array. Three levels of variation are applied to the process parameters, including spindle speed (S), feed rate (f), depth of cut (d), and test specimen (as-cast, T4, and T6 EV31A). The parameters of surface roughness (R a , R z , S a , S z), the rate of material removal (MRR), and the cutting force (F r) were similarly measured. For surface roughness, optical profilometry was used, while the weight loss method and dynamometer were employed, respectively, to assess MRR and F r. In order to improve the process parameters, TOPSIS (techniques order preferences by similarity to ideal solution) is employed. This method reduces several responses to a single measurable response (the closeness coefficient). S = 1500 rpm, f = 150 mm/min, and a P = 1.5 mm are the ideal process parameters to achieve the maximum closeness coefficient (C i) of 0. 917129 under as-cast circumstances. Furthermore, analysis of variance (ANOVA) verifies that sample preparation methods of 24.59 % and depth of cut of 38.19 % significantly impact response characteristics. [ABSTRACT FROM AUTHOR]

Phanerozoic sinter deposits have been reported globally, with their identification mainly based on sedimentological, petrological, and mineralogical studies. In this study, a detailed geochemical investigation, combined with sedimentological characterization, was conducted on the Wugonglilu siliceous deposit, a Cretaceous (106 Ma) sinter in NE China, to examine its genesis. The deposit is inferred as a siliceous hot spring deposit (sinter) owing to its geological setting in an epithermal gold-mining district, its morphologically variable microbial textures typical of subaerial sinters, and nearly pure silica composition. Three lithofacies were recognized in this study, including laminated to thinly bedded sinter, silica-cemented breccia, and epithermal vein, which represent deposits from three contrasting hydrothermal environments. The 87Sr/86Sr ratios of the sinter are similar to the bedrock through which the geothermal fluids passed, namely the Upper Triassic Dajiahe Formation (T 3 dj), a marine siliceous rock unit, and the Lower Cretaceous Datashanlinchang Formation (K 1 d), a rhyolite unit. Results indicate that both underlying units are possible Sr sources of the silica in the Wugonglilu sinter. The REE + Y (rare-earth elements and yttrium) patterns of the sinter exhibit significant variability, primarily due to terrestrial detrital contamination. Differential REE + Y contamination by terrestrial detritus was striking in the white and dark laminae/beds of the laminated to thinly bedded sinter. The white laminae/beds, generally less contaminated, were probably formed during the dry season, whereas the dark laminae/beds exhibiting greater detrital contamination were likely formed during the wet season. When excluding the samples strongly contaminated by detritus, the sinter exhibits Y anomalies comparable to Post-Archean Australian Shale (PAAS), and to the adjacent underlying K 1 d rhyolite and T 3 dj siliceous rock samples, indicating that these anomalies were not inherited from rocks dominating the reservoirs. Furthermore, the sinter shows a (Ce/Ce*) N range close to that of the underlying marine siliceous rock and rhyolite samples, reflecting that the (Ce/Ce*) N of the sinter is largely inherited from the reservoir rock(s). The overall REE + Y patterns of the sinter range from nearly flat to LREE-depleted, similar to some samples of the K 1 d rhyolite and T 3 dj siliceous rock units. However, most samples of the K 1 d rhyolite and T 3 dj siliceous rock display (Pr/Tb) N and (Pr/Yb) N higher than many studied sinter samples. This is likely because of the formation of strong HREE–carbonate complexes during groundwater migration. Based on these results, a generalized formation model of the studied sinter system was constructed. This study suggests that integrated sedimentological and geochemical investigations can aid in interpreting the genesis of sinter deposits, in particular the link between sinter deposits and corresponding reservoir rocks. [ABSTRACT FROM AUTHOR]

The dynamic viscosity coefficients of fluoride ionic melts in the SrF2–RF3 (R = lanthanide (La, Gd, Tb, Yb, or Lu)) binary systems were calculated from diffusion data. A strong dependence of the melt viscosity is observed at low lanthanide concentrations. The Sr1 −xRxF2 +x melts have their viscosity decreasing as the RF3 concentration increases, while increasing in response to decreasing R3+ ionic radius. [ABSTRACT FROM AUTHOR]

Abstract Previous studies showed that Bacillus subtilis possessed high physiological activity in industrial waste treatment as a biosorbent for recovery metals, and in this study, the sorption capacity for both La3+ and Sm3+ was demonstrated. The effects of lanthanide concentration and contact time were tested to acid and alkali pre-treated cells. Very high levels of removal, reaching up to 99% were obtained for both lanthanide ions. Langmuir isotherm model was applied to describe the adsorption isotherm and indicated a better correlation with experimental data R 2 = 0.84 for La3+ using sodium hydroxide pre-treated free cells and R 2 = 0.73 for Sm3+ to acid pre-treated B. subtilis cells as biosorbents. Results of this study indicated that chemically modified B. subtilis cells are a very good candidate for the removal of light rare-earth elements from aquatic environments. The process is feasible, reliable, and eco-friendly.

The relevance of the work is in the fact that the presented data on the sources of ore-bearing fluids of different types of Mesozoic deposits of Eastern Transbaikalia, based on the analysis of distribution of rare-earth elements and indicator ratios of rare and rare-earth elements in ores, will provide new knowledge about the nature of ore formation. The aim of the work is to determine the features of distribution of ore and rare-earth elements in ores of various types of deposits, formed due to different depth ore fluids. Methods. To determine the elemental composition of rocks, the X-ray fluorescence method was used (GIN SB RAS, Ulan-Ude). The concentrations of rare-earth elements were determined by the method of sorption-atomic emission analysis with inductively coupled plasma (GIN SB RAS, Ulan-Ude). Result. It was established that the sources of gold ores of Aleksandrovsky, Itakinsky, and Kariysky, Bugdainsky and Zhirekensky molybdenum, Bukuinsky tungsten deposits were not of uniform depths and differentiated to various extent ore-bearing magmatic sources. The presence of multiple sources of mineralization is confirmed by the indicator ratios Eu/Sm, U/Th, Hf/Sm and Nb/La. It was revealed that in gold deposits in ores formed from magmatic sources of the upper continental crust, relative to the ores, the sources of which were ore-bearing fluids of the lower continental crust, there are elevated concentrations of chalcophile elements (Cu, Ag, Bi, Sb, Pb) and lower concentrations of lanthanides. In molybdenum deposits in ores from magmatic sources of the lower continental crust, in comparison with the ores formed in the upper continental crust, there are elevated concentrations of both chalcophilic elements and lanthanides. In molybdenum deposits in ores from magmatic sources of the lower continental crust, in comparison with the ores formed in the upper continental crust, there are elevated levels of both chalcophile elements and lanthanides. In polymetallic deposits and parts of molybdenum and tungsten deposits, there was only one ore-bearing magmatic source operating in the upper or lower continental crust.

Microstructural evolutions during the high-temperature annealing of Mg alloys containing Al and Gd and after the extrusion process were evaluated and compared to those of the AZ61 alloy. It was revealed that during exposure at the elevated temperatures, the presence of (Mg,Al)3Gd phase, in the form of fine and dispersed particles in the matrix after the extrusion process, could be favorable for the inhibition of grain growth. It was also found that the Al2Gd particles could not effectively retard the coarsening of grains. On the other hand, the grain growth of AZ61 alloy was found to be problematic, which was related to the dissolution of the Mg17Al12 intermetallic phase at temperatures higher than 300°C. In the Mg alloys containing both Al and Gd elements, the increased thermal stability was observed, which was ascribed to the rise of the melting temperature. Finally, some abnormal grain growth was observed in the presence of Al2Gd phase, which was attributed to the nonuniform pinning of grain boundaries by this intermetallic compound.

Up-to-date technologies providing scientific and technological progress are based on the unique properties of rare-earth metals and their compounds. In recent years, attempts have been made to revive rare-earth metals production in Russia, mainly using the sources from which rare-earth elements can be extracted simultaneously (apatites, phosphorites and products of their processing). Another source of rare-earth elements, which is a ready concentrate, is monazite concentrate stored in the warehouse of the state government institution of the Sverdlovsk region «UralMonatsit» in Krasnoufimsk. The known industrial technologies of its processing (alkaline and sulfuric acid) have a number of drawbacks, in particular, the incompleteness of rare-earth elements extraction and the complexity of separating thorium from rare-earth elements. Therefore, there is the relevance of the work on improving the processing technologies of monazite raw materials with extraction of rare-earth elements concentrate and its refinement from impurities, including purification from thorium. To decompose the difficult-to-open crystalline lattice of monazite effectively, its fluorination with ammonium hydrofluoride as a relatively environmentally friendly and regenerable reagent is proposed. The maim aim of the research is to study the process and determine the features of interaction of monazite concentrate with ammonium bifluoride to produce a product suitable for further sulfuric acid processing. The object of the research is a sample of monazite concentrate in the storage of the SGI SR UralMonatsit. Research methods. Atomic emission spectroscopy with inductively coupled plasma, X-ray fluorescence analysis, neutron activation analysis, X-ray phase analysis, scanning electron microscopy with microanalysis, method of combined thermogravimetric/differential-thermogravimetric/differential scanning calorimetric analysis. Results. The paper considers the first stage of the proposed fluorammonium-sulfuric acid processing of monazite concentrates, i.e. the hydrofluorination stage. In the interaction of monazite concentrate with ammonium bifluoride, the impurities contained in the concentrate are the first to enter into a reaction with the formation of fluorides and fluoromammonium compounds; after that the rare-earth metals phosphates enter into reaction. The resulting phosphoric acid reacts with ammonium bifluoride to form ammonium hydrophosphates and a slight phosphorus emission into the gaseous phase. This is confirmed by the results of studies carried out in the temperature range of 170–250 °С: 49,2–83,3 % of phosphorus remains in the solid phase during fluorination, 12,0–32,8 % of phosphorus changes into the liquid phase, 11,2–28,1 % of phosphorus changes into gaseous phase. With a further increase in temperature up to 500 °C, there are no signs of reaction proceeding on the obtained TGA and DSC curves. This allows us to say that complete distillation of phosphorus from the fluorination products in the studied temperature range is impossible. According to the material balance, 10,4-38,4 % of silicon from its content in the initial concentrate transforms into the gas phase in the form of SiF4, 55,3–75,9 % – into the leaching solution in the form of soluble (NH4)2SiF6, which can be decomposed to gaseous SiF4 with further acid processing. On the basis of the results obtained, optimal conditions for fluorination of the monazite concentrate with ammonium hydrofluoride are chosen: temperature is 210 °C; ammonium bifluoride content is 80 % of stoichiometry; the duration of the process is 1,5 hours.

The ability of bivalve mollusks to accumulate chemical elements from the environment makes them an important object for environmental monitoring and assessments of anthropogenic impact on marine ecosystems. The paper presents the data on the content of 65 chemical elements in soft tissues and shells of five species of bivalve mollusks (Astarte crenata, Ciliatocardium ciliatum, Portlandia arctica, Chlamys islandica, Hiatella arctica), as well as in the upper layer (0-5 cm) of bottom sediments of the Kara Sea, the Arctic Ocean. The content of major-, trace and rare-earth elements was determined by atomic emission and inductively coupled plasma mass spectrometry (ICP-AES; ICP-MS). The age, size, and weight of mollusks were measured. There were differences in the content of chemical elements accumulated in soft tissues and shells of mollusks, as well as the significant interspecific difference in the chemical composition of the studied mollusks. The soft tissues of mollusks were accumulated with toxic metals (Hg, Ag, and Cd) in comparison with the content of these elements in bottom sediments. In Chlamys islandica and Hiatella arctica, the shell was accumulated in Cd in contrast to other species. The data obtained may be used for a comprehensive assessment of the state of ecosystems in the seas of the Siberian sector of the Arctic Ocean under changing environment and for studying the fundamental base of the accumulation of chemical elements by marine organisms.

The main purpose of this work is to thoroughly describe the implementation protocol of laser-induced breakdown spectroscopy (LIBS) method in the plant analysis. Numerous feasibility studies and recent progress in instrumentation and trends in chemical analysis make LIBS an established method in plant bioimaging. In this work, we present an easy and straightforward phytotoxicity case study with a focus on LIBS method. We intend to demonstrate in detail how to manipulate with plants after exposures and how to prepare them for analyses. Moreover, we aim to achieve 2D maps of spatial element distribution with a good resolution without any loss of sensitivity. The benefits of rapid, low-cost bioimaging are highlighted.In this study, cabbage (Brassica oleracea L.) was treated with an aqueous dispersion of photon-upconversion nanoparticles (NaYF4 doped with Yb3+ and Tm3+ coated with carboxylated silica shell) in a hydroponic short-term toxicity test. After a 72-hour plant exposure, several macroscopic toxicity end-points were monitored. The translocation of Y, Yb, and Tm across the whole plant was set by employing LIBS with a lateral resolution 100 µm. The LIBS maps of rare-earth elements in B.oleracea plant grown with 50 μg/mL nanoparticle-treated and ion-treated exposures showed the root as the main storage, while the transfer via stem into leaves was minimal. On the contrary, the LIBS maps of plants exposed to the 500 μg/mL nanoparticle-treated and ion-treated uncover slightly different trends, nanoparticles as well as ions were transferred through the stem into leaves. However, the main storage organ was a root as well.

The chemical stability of uranyl arsenates of rare-earth elements with the general formula MIII(AsUO6)3⋅16H2O (MIII–La–Lu) in aqueous solutions has been studied in a wide range of acidity. The acid–base ranges of the existence of these compounds in aqueous solutions were established, the transformation products formed outside these ranges were identified, and the solubility of MIII(AsUO6)3⋅16H2O was determined. Based on the experimental data obtained, the solubility products, Gibbs free energies of the formation of the rare-earth elements uranyl arsenates were calculated, the solubility curves of the studied compounds were computed, and the speciation diagrams of uranium(VI), arsenic(V), and rare-earth elements in saturated aqueous solutions and equilibrium solid phases were constructed. [ABSTRACT FROM AUTHOR]

Redox potential is a crucial electrochemical parameter in the electrorefining process of spent fuel reprocessing. Unfortunately, the harsh measurement environment of spent fuel makes it difficult to obtain. With the continuous updating of computing technology, people have developed the method for calculating the redox potentials using first-principles molecular dynamics (FPMD), but limited by the calculation cost, the simulation scale and time of FPMD are restricted. To make the calculation results more convincing, this work used deep potential (DP) to realize redox potential calculation on a larger time scale. We extracted datasets from FPMD calculations and used these to train and validate the DP, and compared energies, forces, and radial distribution functions that are evaluated using DFT and DP, to demonstrate that DP can achieve DFT accuracy. Using La3+/La as the reference electrode, the redox potentials of Ce3+/Ce, Pr3+/Pr, and Y3+/Y in the LiCl-KCl mixed molten salt system at 723 K were calculated. The results matched well with the FPMD results and experimental data. This work fully demonstrates the feasibility of the DP in calculating the redox potentials. Simultaneously, it provides new idea for obtaining accurate data in the process of spent fuel reprocessing. [ABSTRACT FROM AUTHOR]

A nanostructured defect-fluorite-type Sm 3 NbO 7 has been produced at ambient temperature by the process of mechanical alloying (MA). The powdered mixture of samarium precursor and pure metallic Niobium (Nb) is milled for 17h to obtain the desired sample with mean crystallite size of 160 Å. The phase transformations induced by the high energy milling have been investigated by ex situ X-Ray Diffraction (XRD) measurements and Rietveld method. The results suggest a symmetrization of Sm(OH) 3 crystals induced by Nb solubilization. The Sm 3 NbO 7 microstructures have been examined by Differential Scanning Calorimetry (DSC), heat treatment, Raman spectroscopy and Density Functional Theory (DFT) calculation. The crystallite sizes and defects have been analyzed by Line Profile Analysis utilizing Williamson Hall plot method and Stephens's microstrain model. The anisotropic structural defects caused by MA synthesis disappear under heat treatment with the microstrain reducing from 1.4% to 0.05%. • Mechanical alloying is found to be an efficient method for the synthesis of Sm 3 NbO 7. • Thermal analysis with DSC and heat-treatment reveal that Sm 3 NbO 7 is stable up to 1100 oC. • Theoretical Sm 3 NbO 7 Raman active modes obtained by DFT have been compared with Experimental Raman spectra. [ABSTRACT FROM AUTHOR]

Based on 4,4′-[1,3/4-phenilenebis(oxy)]phthalodinitriles, the mixture of phthalocyaninates of various structures with rare-earth metals were obtained by template fusion method minimizing the side polymerization processes. Target monophthalocyaninates were isolated from the reaction mixture and purified using column and then gel permeation chromatography. The compounds were characterized by NMR, IR spectroscopy, mass spectrometry, and elemental analysis. The spectral properties were studied and the aggregation behavior of the synthesized Er, Yb, and Lu phthalocyaninates in chloroform, acetone, and tetrahydrofuran was determined. It has been shown that lutetium complexes with 3,4-dicyanophenoxyphenoxy ligands are the least stable and least resistant to aggregation in solution, while erbium and ytterbium phthalocyaninates proved to be stable in all studied media. The quantum yields and fluorescence lifetimes of the complexes in chloroform and tetrahydrofuran were calculated.

BaY2F8 nanoparticles (NPs), doped with Yb3+ and Er3+ ions, were successfully produced by high-energy ball-milling. High-quality monoclinic single crystals (sp. gr. C2/m, a = 0.6969(3), b = 1.0502(1), c = 0.4254(1) nm, β = 99.676°) grown from the melt by the Bridgman technique were used as raw materials. The prepared nanocrystals were comprehensively studied by X-ray diffraction analysis, transmission electron microscopy, and optical spectroscopy. The fabrication possibility of single-phase irregular shaped Ba(Y0.964Yb0.030Er0.006)2F8 NPs in the size range of 20–100 nm with a milling duration of 10 h at 600 rpm is demonstrated. Ba(Y0.964Yb0.030Er0.006)2F8 NPs show intense luminescence by both up- (λ = 540 and 650 nm) and down-conversion (λ = 1540 nm) mechanisms upon IR excitation (λ = 980 nm). A qualitative comparison of the spectroscopic characteristics of the produced Ba(Y0.964Yb0.030Er0.006)2F8 NPs with the initial bulk crystal and the widely used up-conversion β-Na1.5(Y1.17Yb0.3Er0.03)F6 NPs is presented. Experimental data offer great opportunities of the Ba(Y0.964Yb0.030Er0.006)2F8 NPs applications in nanophotonics and biotechnology. High-energy ball-milling has potential as a versatile method for the scalable production of fluoride nanoparticles.

In this study, low-temperature solid-state synthesis of pure nanocrystalline ytterbium hexaboride (YbB6) employing iodine-based reduction method has been discussed. For the reduction reaction, the mechanically activated powder mixture of ytterbium oxide, boron oxide, magnesium, and iodine was heated up under Ar in a quartz tube to 85 °C. All reaction byproducts, viz. MgO, Mg3(BO3)2, and YbI2, were removed by hot acid leaching with 3 M HCl solution to form pure YbB6. The morphological and phase structure of the synthesized YbB6 powder were analyzed by X-ray diffractometry (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The crystalline phases obtained were refined by multi-phase Rietveld refinement. XRD and Raman spectroscopy showed a contrast between the nano-YbB6 formed by the present low-temperature iodine-based reduction method versus mechanochemical method. The YbB6 produced by the low-temperature iodine reduction method is highly crystalline in nature, whereas YbB6 produced by mechanochemical method is less crystalline or conversely more amorphous in nature. The iodine-based reduction method indeed played a definitive role to allow the reaction to take place at a lower temperature enabling the formation of nanocrystalline YbB6. [ABSTRACT FROM AUTHOR]