Extraction of Rare-Earth Elements with Solutions of <Emphasis Type="Italic">tri</Emphasis>-<Emphasis Type="Italic">n</Emphasis>-Butyl Phosphate under Local Vibrational Impact in Static and Flow-through Systems

Results are presented of a study of the influence exerted by a local vibrational impact in the dynamic interfacial layer on the extraction of rare-earth elements with tri-n-butyl phosphate solutions in a diluent in static and flow-through systems. It is shown that, in the case of local vibrations in the dynamic interfacial layer, the extraction acceleration factor is determined by the nature of a diluent, vibration frequency of the vibrating element, and fluid motion rate and is nearly independent of the nature of an element being extracted.     

Effect of external factors on the increase in the extraction rate in a vibration treatment on the dynamic interfacial layer

Vibration treatment of a dynamic interfacial layer in the extraction system constituted by an aqueous solution of a salt of a rare-earth element and a solution of di-(2-ethylhexyl)phosphoric acid in heptane (toluene) results in an increase in the process rate. This increase is characterized by an acceleration coefficient defined as the ratio between the lanthanide concentrations in the organic phase after equal intervals of time in systems with and without vibrations. It is shown that the acceleration coefficient depends on the concentration of the extractive agent, initial concentration of an element being extracted, solution pH, and phase contact duration. The observed behavior is explained in terms of the process model suggested by the authors. According to this model, the effect depends on the relative contributions made by a number of interfacial phenomena accompanying the extraction of a lanthanide with solutions of di-(2-ethylhexyl)phosphoric acid in diluents and, in particular, by the spontaneous surface convection and structuring in the interfacial layer.     

Properties of the material of interphase formations based on lanthanide Di-(2-ethylhexyl)phosphate

The structural, optical, and electrical properties of the material of interphase formations arising spontaneously in the interface region of an extraction system consisting of an aqueous solution of a rare-earth element (REE) salt (a solution of di-(2-ethylhexyl)phosphoric acid (D2EHPA) in an organic solvent) are investigated. The structure of lanthanide di-(2-ethylhexyl)phosphate is determined and its lattice constants are estimated. It is shown that the electric conductivity and optical density of the material of interphase formations transferred onto a glass plate correlate with the accumulation of REEs in the interfacial layer of the extraction system. The difference between the properties of the material of interphase formations based on REEs of the yttrium and cerium subgroups is established.     

Self-assembling structures in the extraction of some rare earth elements in systems with D2EHPA

Effect of different factors on the formation of self-assembling structures in a dynamic interfacial layer in LnA₃-H₂O-D2EHPA-solvent extraction systems was studied. Increase in temperature was shown to inhibit the formation of the self-assembling structures. An exposure of dynamic interfacial layer to mechanical vibrations using a microvibrator was found to prevent structurization and provide higher aggregative stability of disperse system. The structure deteriorates when exposed to vibration and decomposes to aggregates at rather high power. On the extraction of rare earth elements (REE) of yttrium subgroup, the system partially recovers its properties after termination of exposure to vibration, i.e., it is coagulation and thixotropic and becomes condensation in time.     

Extraction of impurities of rare-earth elements from uranium dioxide using bromine trifluoride for their preconcentration and analytical determination

The behavior of impurities of rare-earth elements in the fluorination of UO₂ with bromine trifluoride is studied by the radioactive tracer method using¹⁵²Eu radionuclide. It is demonstrated that uranium is completely removed as hexafluoride, whereas impurities of rare-earth elements quantitatively remain in the crucible because of the nonvolatility of their fluorides. Based on this fact, the concentrations of rare-earth elements in UO₂ is determined. Results of analysis are in agreement with the data that were obtained using the conventional technique for the extraction of rare-earth elements from UO₂     

Separation of transplutonium and rare-earth elements by extraction with HDEHP from DTPA solutions

The extraction behaviour of Am, Cm, Bk, Cf, Es, La, Ce, Pr, Pm, Sm, Eu, Gd, Ho, Yb and Lu in the system HDEHP—DTPA in lactic acid has been studied from the point of view of group separation of the transplutonium and rare-earth elements. Optimum separation conditions have been found on the basis of the results obtained. Some test separations of transplutonium elements from rare-earth fission products have been carried out in real solutions by extraction chromatography. It has been shown that this method can be used successfully for the analytical determination of transplutonium elements as well as for recovery of the latter from irradiated samples.     

Simplified model for extraction of rare-earth ions using emulsion liquid membrane

By considering the resistances of rare-earth ions in both the external and membrane phases, the interfacial reaction and the membrane breakage, a mathematical model for the extraction of rare-earth ions by batch emulsion liquid membrane process is established. Further, two simplified mass transfer equations are also derived from the proposed model in each of the specified cases. The validity of both the model and the resulting equations are tested by batch extraction of Sm³⁺ with emulsion liquid membrane containing di-2-ethylhexyl phosphoric acid as a carrier in kerosene. The experimental results show that both the proposed model and the resulting equations can simulate mass transfer process satisfactorily.     

Extraction of Nitric Acid from Chloride-Nitrate Solutions

The extraction of nitric acid from chloride-nitrate solutions simulating solutions that result from eudialyte breakdown with hydrochloric acid after extractive recovery of rare-earth elements was studied. A general flowsheet was suggested for the extraction of rare-earth elements from chloride solutions and utilization of nitrate ions as concentrated solutions of nitrates used in recycling.     

Probing inhomogeneous vibrational reorganization energy barriers of interfacial electron transfer

An atomic force microscopy (AFM) and confocal Raman microscopy study of the interfacial electron transfer of a dye-sensitization system, i.e., alizarin adsorbed upon TiO(2) nanoparticles, has revealed the distribution of the mode-specific vibrational reorganization energies encompassing different local sites ( approximately 250-nm spatial resolution). Our experimental results suggest inhomogeneous vibrational reorganization energy barriers and different Franck-Condon coupling factors of the interfacial electron transfer. The total vibrational reorganization energy was inhomogeneous from site to site; specifically, mode-specific analyses indicated that energy distributions were inhomogeneous for bridging normal modes and less inhomogeneous or homogeneous for nonbridging normal modes, especially for modes far away from the alizarin-TiO(2) coupling hydroxyl modes. The results demonstrate a significant step forward in characterizing site-specific inhomogeneous interfacial charge-transfer dynamics.     

Extraction of Rare-Earth Elements in Hydrofluoride Decomposition of Loparite Concentrate

Distribution and existence forms of rare-earth elements in decomposition of the loparite concentrate with ammonium hydrofluoride were studied. It was found that, in the course of the aqueous leaching of the fluorinated concentrate, rare-earth elements fully remain in the insoluble residue as complex salts of general formula NaLnF₄. The process of pyrohydrolysis of the insoluble residue was examined. It was shown that varying the process conditions always results in that a NaLnF4-containing product is obtained. It was found that rare-earth elements can be extracted from the insoluble residue and separated from calcium and thorium, and the conditions for this extraction were determined.     

Reduced coupling of water molecules near the surface of reverse micelles

We report on vibrational dynamics of water near the surface of AOT reverse micelles studied by narrow-band excitation, mid-IR pump-probe spectroscopy. Evidence of OH-stretch frequency splitting into the symmetric and asymmetric modes is clearly observed for the interfacial H(2)O molecules. The polarization memory of interfacial waters is preserved over an exceptionally extended >10 ps timescale which is a factor of 100 longer than in bulk water. These observations point towards negligibly small intermolecular vibrational coupling between the water molecules as well as strongly reduced water rotational mobility within the interfacial water layer.     

镧系收缩效应对稀土-煤相互作用的影响及煤中有机态稀土的赋存形式研究

通过酸洗脱灰及腐殖酸提取等方法对伊敏褐煤进行处理,并应用ICP-MS对处理前后的样品进行了稀土元素测定。在对脱灰前后稀土元素与灰分和C、H、O等有机组成元素的相关性以及稀土元素在腐殖酸中的赋存特征分析的基础上,认为煤中稀土元素-有机质相互作用受煤化作用过程中的脱氧、脱氢和增碳作用控制。稀土与煤中各类官能团相互作用形成四类有机态稀土元素复合物,第一类是与被烷基侧链高度取代的芳香结构单元形成的复合物;第二类是与氢化芳香结构单元形成的复合物;第三类是与低取代度的芳香结构单元形成的复合物;第四类是与含氧官能团作用形成的复合物,后两类的稳定性差。这些有机态稀土元素复合物的稳定性在总体受镧系收缩效应控制的基础上,还受稀土元素化学价态的影响;重稀土与有机质形成的有机态稀土元素复合物的稳定性大于轻稀土。轻稀土在原煤中和腐殖酸的结合不稳定,且具有与镧系收缩相反的效应;轻稀土在脱灰煤中和腐殖酸的结合,与中稀土、重稀土在原煤和脱灰煤中腐殖酸结合规律相同,都体现了良好的镧系收缩效应。     

Ultrafast energy transfer in water-AOT reverse micelles

A spectroscopic investigation of the vibrational dynamics of water in a geometrically confined environment is presented. Reverse micelles of the ternary microemulsion H2O/AOT/n-octane (AOT = bis-2-ethylhexyl sulfosuccinate or aerosol-OT) with diameters ranging from 1 to 10 nm are used as a model system for nanoscopic water droplets surrounded by a soft-matter boundary. Femtosecond nonlinear infrared spectroscopy in the OH-stretching region of H2O fully confirms the core/shell model, in which the entrapped water molecules partition onto two molecular subensembles: a bulk-like water core and a hydration layer near the ionic surfactant headgroups. These two distinct water species display different relaxation kinetics, as they do not exchange vibrational energy. The observed spectrotemporal ultrafast response exhibits a local character, indicating that the spatial confinement influences approximately one molecular layer located near the water-amphiphile boundary. The core of the encapsulated water droplet is similar in its spectroscopic properties to the bulk phase of liquid water, i.e., it does not display any true confinement effects such as droplet-size-dependent vibrational lifetimes or rotational correlation times. Unlike in bulk water, no intermolecular transfer of OH-stretching quanta occurs among the interfacial water molecules or from the hydration shell to the bulk-like core, indicating that the hydrogen bond network near the H2O/AOT interface is strongly disrupted.     

Effect of rare-earth component of the RE/Ni catalyst on the formation and nanostructure of single-walled carbon nanotubes

A systematic experimental study has been carried out on the efficiency of bimetallic catalysts based on Ni and the rare-earth elements Y, La, Ce, Nd, Gd, Tb, Dy, Ho, Er, and Lu (group A) and Eu, Sm, Yb, and Tm (group B) in the synthesis of single-walled carbon nanotubes (SWNTs). The two groups give quite different results when analyzed by a combination of SEM/TEM and Raman and UV-NIR spectroscopies. The elements in group A have an obvious catalytic effect and increase the yield of SWNTs dramatically, whereas those in group B are not efficient catalysts. The diameter distribution of the synthesized SWNTs was also affected by the rare-earth element used. For group A metals, there is a tendency that the fraction of small-diameter tubes decreases with decreasing ionic radius of the rare-earth element used. EDX and X-ray analyses indicate that group A metals deposit on the cathode deposits and form rare-earth carbides, whereas no group B metals are found in cathode deposits, except for a small amount of Tm present in the form of thulium carbide. Further analysis indicates that there is a very strong correlation between the ability to form rare-earth carbides and the catalytic efficiency for the formation of SWNTs.     

ICP－AES半智能直接测定稀土氧化物

本文报道了一种用ＩＣＰ－ＡＥＳ直接测定稀土氧化物的半智能方法，稀土基体对某一稀土分析谱线的光谱干扰被预先扫描并存于谱图集中。在实际测定中，相应的干扰谱图被调用，参加扣除干扰谱线影响的校正计算。结果表明该法令人满意。     

Recovery of rare-earth elements from nitrate solutions using polyethylene glycol 1500

Russian Chemical Bulletin - A new extraction system based on polyethylene glycol 1500 and NaNO3 was proposed for the recovery of light rare-earth elements (Ce, La, Nd, Pr, and Sm) from aqueous...     

Advanced system for separation of rare-earth fission products

A microprocessor-controlled radiochemical separation system, which has been developed at the INEL, has been further advanced to separate individual rare-earth elements from mixed fission products in times of a few minutes. The system was composed of an automated chemistry system fed by two ∼300μg²⁵²Cf sources coupled directly by a He-jet to transport the fission products. Chemical separations were performed using two high performance liquid chromatography columns coupled in series. The first column separated the rare-earth group by extraction chromatography using dihexyldiethylcarbamoylmethylphosphonate (DHDECMP) adsorbed on Vydac C₈ resin. The second column isolated the individual rare-earth elements by cation exchange chromatography using Aminex A-9 resin with α-hydroxyisobutyric acid (α-HIBA) as the eluent. Significant results, which have been obtained to date with this advanced system, are the identification of several new neutron-rich rare-earth isotopes including¹⁵⁵Pm (T=48±4 s) and¹⁶³Gd (T=68±3 s). In addition a half-life of 41±4 s is reported for¹⁶⁰Eu. Work supported by the U.S. Department of Energy under DOE Contract No. De-ACO7-76IDO-1570.     

Surface Charges at the CaF2/Water Interface Allow Very Fast Intermolecular Vibrational‐Energy Transfer

We investigate the dynamics of water in contact with solid calcium fluoride, where at low pH, localized charges can develop upon fluorite dissolution. We use 2D surface‐specific vibrational spectroscopy to quantify the heterogeneity of the interfacial water (D₂O) molecules and provide information about the sub‐picosecond vibrational‐energy‐relaxation dynamics at the buried solid/liquid interface. We find that strongly H‐bonded OD groups, with a vibrational frequency below 2500 cm^?1, display very rapid spectral diffusion and vibrational relaxation; for weakly H‐bonded OD groups, above 2500 cm^?1, the dynamics slows down substantially. Atomistic simulations based on electronic‐structure theory reveal the molecular origin of energy transport through the local H‐bond network. We conclude that strongly oriented H‐bonded water molecules in the adsorbed layer, whose orientation is pinned by the localized charge defects, can exchange vibrational energy very rapidly due to the strong collective dipole, compensating for a partially missing solvation shell.     

Rare-earth element abundance in tissues and plasma of healthy subjects and patients by neutron activation analysis

In recent years much attention has been paid to the presence and role played by trace metals in human tissues and body fluids. Rare-earth element ions are known to have high affinity for calcium binding sites and to antagonize calcium-mediate biological response. The present paper describes an investigation on rare-earth elements abundance in tissue and endogenous plasma of apparently healthy subjects and patients affected by epicondylitis, at the elbow or by laryngeal carcinoma. Some rare-earth elements, namely La, Ce, Nd, Eu, Gd, Yb and Lu were determined by radiochemical neutron activation analysis. Results are presented and discussed as far as precision, accuracy and sensitivity are concerned. The obtained data indicate that rare-earth elements levels in plasma and tissues are significantly affected by the occurence of pathological conditions.     

Processing of phosphodihydrate to separate rare-earth elements and obtain gypsum free from phosphates and fluorides

Geotechnological complex processing of phosphodihydrate, including sulfuric acid leaching, sorption extraction of rare-earth elements, recovery of leaching solutions to obtain rare-earth products and gypsum material, which in the radioactivity and concentration of impurity fluorides and phosphates is suitable for use in building and cement industries, is outlined.