The Influence of the Hofmeister Bias and the Stability and Speciation of Chloridolanthanates on Their Extraction from Chloride Media

The possibility of recovering rare earth elements from solutions containing their chloridometalate anions [LnCl_x]^(x?3)? via the process: LnCl_x^(x?3)? + (x ? 3)L_org + (x–3)H⁺ ? [(LH)_x?3LnCl_x]_org has been tested using 2-(1,3-bis(hexylamino)-1,3-dioxopropan-2-yl)-4,6-di-tert-butylpyridine (PMA), tri-n-butylphosphate (TBP), and tri-n-octylamine (TOA), which are known to be strong extractants for transition metal chloridometalates. While DFT calculations indicate that the formation of the neutral assembly [(PMAH)₃LaCl₆] in the gas phase is favorable, no uptake of La(III) from 6 M HCl by toluene solutions of PMA (or of TBP or TOA) was observed in solvent extraction experiments. Successful uptake of the [PtCl₆]^2? dianion by PMA and the failure to extract the [IrCl₆]^3? trianion under the same conditions indicate that the higher hydration energy of the latter makes transfer to the toluene solution less favorable and that this militates against extraction of La(III) chlorido complexes carrying charges of ?3 or larger in which all the inner-sphere water molecules have been replaced. Computational results confirm literature observations that, in contrast to transition metal trications, formation of REE metalate anions such as [LnCl_x]^(x?3)? is not very favorable, particularly so for chloride, compared with nitrato or sulfato systems. Also, they indicate that the formation of outer-sphere assemblies such as {[La(H₂O)₉]·xCl} in which water ligands are retained in the inner sphere, H-bonded to anions, is more stable than inner-sphere complexes containing an equivalent number of anions. The high level of hydration of such species disfavors their transfer into nonpolar water-immiscible solvents. It is unlikely that recovery of [LnCl_x]^(x?3)? from acidic solutions can be achieved efficiently using currently available anion exchange extractants operating in a “pH-swing” process. Receptors giving very high binding energies to chloridolanthanates will be needed to offset the high dehydration energies required.     

Ultrastructural study of the intracellular behavior of four mineral elements in the lactating mammary gland cells: study using conventional transmission electron microscopy

The effects of parenteral injection of aluminum, indium, gadolinium, or terbium in rats have been previously studied in several organs such as the liver, the kidneys, etc., but never in mammary glands. In this work, we have attempted to study the subcellular localization of these elements after their intraperitoneal administration. Their subsequent effects in the lactating mammary gland cells have also been studied. Our results using conventional transmission electron microscopy have shown that the lysosomes of the mammary glandular epithelial cells are the intracellular site of accumulation of the studied elements. Our results have also show intracellular deteriorations such as an expanded ergastoplasm and altered mitochondria after intraperitoneal injection of aluminum and indium.     

Magnetic Anisotropy Switch: Easy Axis to Easy Plane Conversion and Vice Versa

The rational design of the magnetic anisotropy of molecular materials constitutes a goal of primary importance in molecular magnetism. Indeed, the applications of molecular nanomagnets, such as single‐molecule magnets and molecular magnetic refrigerants, depend on the full control over this property. Axially anisotropic magnetic systems are frequently classified as easy axis or easy plane, depending on whether the lowest energy is obtained by application of a magnetic field parallelly or perpendicularly to the unique axis. Here, the magnetic anisotropy of three lanthanide complexes is studied as a function of magnetic field and temperature. It is found that for two of these the type of magnetic anisotropy switches as a function of these parameters. Thus, this paper experimentally demonstrates that the magnetic anisotropy is not uniquely defined by the intrinsic electronic structure of the systems in question but can also be reversibly switched using external stimuli: temperature and magnetic field.     

Visible‐Light Excited Luminescent Thermometer Based on Single Lanthanide Organic Frameworks

Isostructural lanthanide organic frameworks (Me₂NH₂)₃[Ln₃(FDC)₄(NO₃)₄]·4H₂O (Ln = Eu ( 1 ), Gd ( 2 ), Tb ( 3 ), H₂FDC = 9‐fluorenone‐2,7‐dicarboxylic acid), synthesized under solvothermal conditions, feature a Ln‐O‐C rod‐packing 3D framework. Time‐resolved luminescence studies show that in 1 the energy difference between the H₂FDC triplet excited state (17794 cm^?1) and the ⁵D₀ Eu³⁺ level (17241 cm^?1) is small enough to allow a strong thermally activated ion‐to‐ligand back energy transfer. Whereas the emission of the ligand is essentially constant the ⁵D₀→⁷F₂ intensity is quenched when the temperature increases from 12 to 320 K, rendering 1 the first single‐lanthanide organic framework ratiometric luminescent thermometer based on ion‐to‐ligand back energy transfer. More importantly, this material is also the first example of a metal organic framework thermometer operative over a wide temperature range including the physiological (12‐320 K), upon excitation with visible light (450 nm).     

Supercritical Fluid Dissolution and Extraction of Trivalent Metal Cations from Different Matrices

Studies on the recovery of trivalent metal ions such as Nd³⁺Eu³⁺ (taken as homologs of Am(III)) from solid oxide (Nd₂O₃), Thorium concentrate (obtained from Monazite ore processing), tissue paper/surgical gloves (rubber), and plant samples have been carried out by supercritical fluid extraction (SFE) using supercritical CO₂ and ethanol/nitric acid. N,N,N’,N’-tetraoctyl diglycolamide (TODGA) was used as the extractant in these studies. The results showed that the recovery of Nd increased with TODGA concentration from 50% (no TODGA) to 70% (10% TODGA) at 3 M HNO₃ in ethanol. However, the extraction of Nd at 1 M HNO₃ was invariant with 1-3% (v/v) TODGA concentration (73 ± 4%). Interestingly, REEs recovery from Th concentrate was ? 60% even without TODGA using ethanol/3 M HNO₃ mixture. On the other hand, quantitative recovery of ^152,154Eu from tissue paper and surgical gloves sample could be achieved using 3 M HNO₃/ethanol mixture. This suggested that it would be possible to decontaminate the contaminated laboratory waste papers using SFE technique.     

Sensitization of Er3+ Infrared Photoluminescence Embedded in a Hybrid Organic‐Inorganic Copolymer containing Octahedral Molybdenum Clusters

Luminescent hybrid copolymers are obtained by copolymerizing in bulk methylmethacrylate with a methacrylic acid (MAC) solution containing [n‐Bu₄N]₂[Mo₆Br₈(MAC)₆], and aliquots of an Er(TMHD)₃ complex (TMHD for 2,2,6,6‐tetramethyl‐3,5‐heptanedione) solution. This leads to novel homogeneous and transparent hybrid materials in which the Er³⁺ infrared luminescence at 1.55 μm, a standard wavelength for telecommunication applications, is up to six time more intense in the presence of Mo₆ clusters when samples are irradiated at 476.5 nm. This work demonstrates the outstanding potential of Mo₆ clusters, compounds obtained by high‐temperature solid‐state synthesis, in the design of functional hybrid materials via soft chemistry routes.     

SOLVENT EXTRACTION OF COBALT AND NICKEL IN BIS (2,4,4-TRI-METHYLPENTYL) PHOSPHINIC ACID, “CYANEX -272”

ABSTRACT A study has been made of the extraction of cobalt and nickel from sulfate solutions into bis(2,4,4 tri-methylpentyl) Phosphinic acid - “Cyanex 272”, diluent Esso solvent DX 3641, for both high and low metal loading in the organic phase. In dilute solution, 0.01 M, extraction constants and enthalpies were determined for both metals. The extraction of cobalt was always favored over that of nickel, increasing with increase in temperature. No structure change with temperature was found for the cobalt-Cyanex complex. Phase modifiers were found to effect the selectivity of “Cyanex 272” for cobalt.

At high metal loading, equilibrium curves for cobalt were fitted using semi-empirical curve fitting, while for nickel a straight line variation was observed. Organic phase polymerization was observed for both metals the degree of aggregation increasing with increase in loading. A step change increase in the viscosity of the organic phase was observed at high cobalt loading. Phase modifiers proved to be ineffective In reducing the increase in organic phase viscosity.     

C 3‐Symmetric Tripodal Thio/Diglycolamide‐Based Ligands for Trivalent f‐Element Separations

Abstract

Three new C ₃‐symmetric ligands bearing diglycolamide and thiodiglycolamide units on a triphenoxymethane platform have been synthesized and evaluated as trivalent f‐element extractants from nitric acid media. Liquid‐liquid extraction studies of eleven different lanthanides from 1 M nitric acid into dichloromethane revealed a strong influence of the amidic substituents on the extraction efficiency. A comparison of the ¹H NMR spectrum of the Lu(III) complex formed with the tris‐DGA ligand and the organic solution after the extraction experiment confirms that all three arms bind the metal during the extraction experiment and form a C ₃‐symmetric complex. The newly synthesized lipophilic di‐n‐butyl tris‐diglycolamide was found to be a significantly weaker extractant in comparison to the di‐isopropyl analogs. The distance separating the metal binding groups from the triphenoxymethane platform had little influence on the selectivity or binding efficiency of the ligands. Experiments with the tris‐thiodiglycolamide derivative highlighted the importance of the etheric oxygens for metal binding.