Search Results (6)

This study focused on the nature of rare earth metal complex compounds that can form during the carbonate–alkaline processing of industrial waste materials, such as phosphogypsum and red mud, at 70–100 °C and 1–10 atm. Experimental findings revealed that the dissolution of synthetic carbonates of rare earth elements (REEs) in a concentrated carbonate-ion medium (3 mol/L) leads to the formation of ion-associates of varying strengths. Light (lanthanum, praseodymium, and neodymium) and medium (samarium) REE groups exhibited a tendency to form loose ion-associates, whereas heavy REEs (terbium, dysprosium, holmium, erbium, thulium, lutetium, and yttrium) formed close ion-associates. To confirm the existence of these ion-associates, the specific conductivity of solutions was measured after dissolving thulium (III) and samarium (III) carbonates at phase ratios ranging from 1:2000 g/mL to 1:40 g/mL in a potassium carbonate medium. The decay of ion-associates, leading to the precipitation of rare earth metal (III) carbonates, was tested in an ammonium carbonate medium. Thermal decomposition of ammonium carbonate at 70–75 °C during 1–4 h was accompanied by full rare earth carbonates’ sedimentation and its in-the-way separation into groups because of the varied strength of ion-associates. The results of this study provide a basis for developing processes to separate rare earth metals into groups during their carbonate–alkaline extraction into solution. Full article

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 ${\mathrm{EuL}}_2^{-}$ 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. Full article

Spinel cobalt ferrite/hexagonal strontium hexaferrite (2CoFe₂O₄/SrFe_12−2xSm_xLa_xO₁₉; x = 0.2, 0.5, 1.0, 1.5) nanocomposites were fabricated using the tartaric acid precursor pathway, and the effects of La³⁺–Sm³⁺ double substitution on the formation, structure, and magnetic properties of CoFe₂O₄/SrFe_12−2xSm_xLa_xO₁₉ nanocomposite at different annealing temperatures were assayed through X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. A pure 2CoFe₂O₄/SrFe₁₂O₁₉ nanocomposite was obtained from the tartrate precursor complex annealed at 1100 °C for 2 h. The substitution of Fe³⁺ ion by Sm³–⁺La³⁺ions promoted the formation of pure 2CoFe₂O₄/SrFe₁₂O₁₉ nanocomposite at 1100 °C. The positions and intensities of the strongest peaks of hexagonal ferrite changed after Sm³⁺–La³⁺ substitution at ≤1100 °C. In addition, samples with an Sm³⁺–La³⁺ ratio of ≥1.0 annealed at 1200 °C for 2 h showed diffraction peaks for lanthanum cobalt oxide (La₃Co₃O₈; dominant phase) and samarium ferrite (SmFeO₃). The crystallite size range at all constituent phases was in the nanocrystalline range, from 39.4 nm to 122.4 nm. The average crystallite size of SrFe₁₂O₁₉ phase increased with the number of Sm³⁺–La³⁺ substitutions, whereas that of CoFe₂O₄ phase decreased with an x of up to 0.5. La–Sm co-doped ion substitution increased the saturation magnetization (Ms) value and the subrogated ratio to 0.2, and the Ms value decreased with the increasing number of double substitutions. A high saturation magnetization value (Ms = 69.6 emu/g) was obtained using a La³⁺–Sm³⁺ co-doped ratio of 0.2 at 1200 for 2 h, and a high coercive force value (Hc = 1192.0 Oe) was acquired using the same ratio at 1000 °C. Full article

Two novel mixed ligand complexes with general formula [M₂(4,4′-bpy)_1.5(CBr₂HCOO)₆(H₂O)₂]_n (where 4,4′-bpy = 4,4′-bipyridine) were synthesized. Thermal analysis was used to describe a solid intermediate and final products of thermolysis. A coupled TG-MS system was used to monitor principal volatile fragments evolved during pyrolysis. Crystal structures of the complexes were determined. Cationic dinuclear M₂ (M(III) = La, Sm) coordination cores were obtained. Both crystal structures are isostructural. Single crystal X-ray diffraction analysis revealed that investigated structures of 1D coordination polymers assembled in ladder-like systems. The central atom replacement resulted in unit cell identity parameter П = 0.0091. Additionally, the isostructurality of the reported La(III) and Sm(III) complexes was revealed using Hirshfeld Surface analysis supported by Enrichment Ratio calculations. Full article

Laser-induced breakdown spectroscopy (LIBS) was undertaken using an instrument which used a high-powered microscope to deliver the light and tightly focused the low energy laser beam onto the surface of a solid sample. A micro-plasma was generated on the surface of the sample under test even though the amount of energy/pulse from a beam of 532 nm was <1 mJ. Rare earth elements such as europium, gadolinium, lanthanum, neodymium, praseodymium, samarium, and a transition metal, yttrium, were tested. These elements are important in nuclear fission reactions especially for estimation of actinide masses for non-proliferation “safeguards”. Each element was mixed in the graphite matrix in different percentages from 1% to 50% by weight and the LIBS spectra were obtained for each composition as well as after mixing each element in the same amount using oxides of the elements. The data for the 5% mixture of the rare earth elements with graphite powder along with the transition metal has been presented in this article. A micro-LIBS approach was used to demonstrate that these rare earth elements can be identified individually and in a complex mixture in glove boxes in which the microscope LIBS instrument is housed in a nuclear research environment. Full article

This article analyzes the lanthanum, cerium, samarium, europium, terbium, ytterbium, lutetium, uranium, and thorium content in humic acids within soil and paleosol surface horizons from the southern steppe in the Southern Urals. Research demonstrates similar accumulation levels of these elements in paleosols isolated from both the active medium between 3.6 and 3.3 thousand years ago and in recent background soils. Despite the lack of significant differences, research has shown a growing content among the rarest metals in the series “the buried paleosols–man-modified paleosols of settlement–recent background soils”. Research has detected the lowest content of La, Ce, Sm, Eu, Yb, Lu, and Th in preparations of humic acids of recent background soils. This reveals a close content to most elements in humic acids of paleosols buried under barrows and ancient settlement paleosols. Additionally, it indicates the virtual absence of anthropogenic impact on binding lanthanides and actinides by humic acids in ancient times. The contribution of humic acids into the common pool for each element was evaluated using a special approach. Research showed that there was less than half the share of elements associated by humic acids of paleosols than in the recent background chernozems in the total pool of lanthanides and actinides. This article considers the prospects of using humic acids of recent and ancient soils in identifying behavioral patterns of metal complexes through time. Full article