The Partitioning of Americium and the Lanthanides Using Tetrabutyldiglycolamide (TBDGA) in Octanol and in Ionic Liquid Solution

Separations among the lanthanides and the separation of Am from the lanthanides remain challenging, and research in this area continues to expand. The separation of adjacent lanthanides is of interest to high-tech industries because individual lanthanides have specialized uses and are in short supply. In nuclear fuel cycle applications Am would be incorporated into fast-reactor fuels, yet the lanthanides are not desired. In this work, the diglycolamide N,N,N′,N′-tetrabutyldiglycolamide (TBDGA) was investigated as a ligand for lanthanide and Am solvent extraction in both molecular and room-temperature-ionic-liquid (RTIL) diluents.The RTIL [C₄MIM][Tf₂N] showed very high extraction efficiency for these trivalent metals from low nitric acid concentrations, while the molecular diluent 1-octanol showed high extraction efficiency at high acid concentrations. This was attributed to the extraction of ionic nitrate complexes by the RTIL, whereas 1-octanol extracted neutral nitrate complexes. TBDGA in RTIL did not provide adequate separation factors for Am/lanthanide partitioning, but 1-octanol did show reasonable separation possibilities. Lanthanide intergroup separations appeared to be feasible in both diluents, but with higher separation factors from 1-octanol.     

Extraction behavior of selected rare earth metals from acidic chloride media using tetrabutyl diglycolamide

Rare earth elements (REEs) are vital to modern, high-tech devices. Recycling REEs from post-consumer electronics can potentially diminish supply chain risks. Toward that end, liquid–liquid solvent extraction of various REEs was investigated with tetrabutyl diglycolamide (TBDGA) in 1-octanol from hydrochloric acid media. Metal partitioning to the organic phase was shown to increase as [Cl^?] increased. In contrast, increasing [H⁺] did not improve extraction. The use of the polar diluent 1-octanol provided high extraction efficiency, especially for the partition of heavy lanthanides from solutions of high chloride concentration. Although the polar diluent also extracted molar amounts of water and acid, it was concluded that a neutral metal/TBDGA complex as mainly the di-solvate was extracted, and that complexation was observed to be exothermic. These results indicate that REE extraction from aqueous chloride solutions can be efficient without the use of high acid concentrations.     

Luminescence properties of calcium tungstate activated by lanthanide(Ⅲ) ions

Calcium tungstate phosphors activated by the Ln3+ ions(Ln=Pr, Nd, Tb, Yb) were synthesized by a traditional high-temperature solid-state method. The crystal structures and morphologies of the products were characterized by scanning electron microscopy(SEM), X-ray powders diffraction(XRD) and infrared spectra(FT-IR). The samples were found to show luminescence properties(down-conversion, DC, at excitation wavelength 254 nm and up-conversion, UC, at excitation wavelength 980 nm). CaWO4 doped with Tb3+/Yb3+ showed green DC and UC luminescence characteristic of Tb(III) ion in the range of 470–660 nm, corresponding to the 5D4→7F6,5,4,3,2 electronic transition. CaWO4 doped with Pr3+/Yb3+ showed week blue, green and red(DC and UC) luminescence of Pr(III) ion, in the wavelength region of 450–700 nm. Emission peaks were ascribed to the 3P1→3H4,5,6, 3P0→3H4,5,6, 3P1→3F2 and 3P0→3F2 transitions, respectively. CaWO4 doped with Nd3+/Yb3+ phosphor emitted orange UC luminescence at 450–690 nm(2P3/2→4I15/2, 4G7/2→4I9/2,11/2,13/2) and strong near-infrared UC luminescence at 720–900 nm(4F7/2+4S3/2→4I9/2, 4F5/2+2H3/2→4I9/2, 4F3/2→4I9/2) which is the characteristic of Nd(III) ion.     

Cerium dioxide as a new reactive sorbent for fast degradation of parathion methyl and some other organophosphates

Cerium dioxide was used for the first time as reactive sorbent for the degradation of the organophosphate pesticides parathion methyl,chlorpyrifos,dichlofenthion,fenchlorphos,and prothiofos,as well as of some chemical warfare agents—nerve gases soman and O-ethyl S-[2-(diisopropylamino) ethyl] methylphosphonothioate(VX).CeO2 specimens were prepared by calcination of basic cerous carbonate obtained by precipitation from an aqueous solution.The CeO2 samples containing certain amounts(1 wt.%–5 wt.%) of the neighboring lanthanides(La,Pr,Nd) were prepared in a similar way from pure lanthanide salts.It was shown that ceria accelerated markedly the decomposition of parathion methyl causing the cleavage of the P-O-aryl bond in the pesticide molecule.A similar reaction mechanism was proposed for the degradation of other organophosphate pesticides and nerve agents.The degradation times(reaction half-times) were in an order of minutes in the presence of CeO2,compared to hours or days under common environmental conditions.The reaction in suitable organic solvents allowed conversions of about 90% for parathion methyl loading of 20 mg pesticide/g CeO2 within 2 h with a reactant half-life in the order of 0.1 min.The key parameter governing the degradation efficiency of CeO2 was the temperature during calcination.At optimum calcination temperature(about 773.15 K),the produced ceria retained a sufficiently high surface area,and attained an optimum degree of crystallinity(related to a number of crystal defects,and thus potential reactive sites).The presence of other lanthanides somewhat decreased the reaction rate,but this effect was not detrimental and permitted the possible use of chemically impure ceria as a reactive sorbent.A fast organophosphate degradation was demonstrated not only in non-polar solvents(such as heptane),but also in polar aprotic solvents(acetonitrile,acetone) that are miscible with water.This opens new possibilities for designing more versatile decontamination strategies.The cleavage of phosphate ester bonds is of a great importance not only for the degradation of dangerous chemicals(chemical weapons,pesticides),but also for interactions of ceria(especially the nano-sized one) in biologically relevant systems.     

Dependence of Extraction Properties of 2,6-Dicarboxypyridine Diamides on Extractant Structure

Abstract

New diamides of dipicolinic acid have been prepared and their affinity for lanthanides, americium, and uranium has been explored using the liquid-liquid extraction method. These extractants feature mixed alkyl/aryl substituents. The highest extraction is seen for phenyl/ethyl derivatives. The structure-reactivity relationship for extraction and solubility is discussed.     

Rare earth elements and select actinoids in the Canadian House Dust Study

Nationally representative baseline data are presented for rare earth elements (REE), thorium (Th) and uranium (U) in house dust sampled from 1025 urban homes, in units of concentrations (μg g^?1), loadings (μg m^?2), and loading rates (ng m^?2 d^?1). Spearman rank correlations indicate that, in addition to outdoor sources, consumer products and building materials can influence indoor dust concentrations of REE, Th, and U. Correlations (P<.01) with numbers of occupants, dogs, and cats suggest soil track‐in. Correlations (P<.01) with hardwood floors suggest release of REE additives used in pigments and coatings during daily wear and tear. Concentrations of light REE are elevated in smokers’ homes compared to non‐smokers’ homes (P<.001), suggesting that a key source is “mischmetal,” the REE alloy used in cigarette‐lighter flints. Indoor sources include geological impurities in raw materials used in consumer products, such as U and Th impurities in bentonite clay used in cat litter, and REE impurities in phosphates used for a variety of applications including dog food and building materials. Median gastric bioaccessibility (pH 1.5) of most REE in dust ranges from about 20% to 29%. Household vacuum samples correlate with fresh dust samples from the same homes (P<.001 for all investigated elements).     

The recovery of uranium and the lanthanides from phosphate rock

A process is proposed for the treatment of phosphate rock for the recovery of uranium and lanthanides. The process assures the production of phosphatic fertilisers without polluting the environment with radioactive material.     

The recovery of the lanthanides from phosphate rock

Phosphate rock contains up to 1% lanthanide (rare earths) oxides present in isomorphous substitution for Ca²⁺. Lanthanum, cerium and neodymium form about 80% of the total. When the rock is leached with H₂SO₄ the lanthanides are mostly (about 70%) lost in the gypsum residue. When the rock is leached with HNO₃ or HC1, more than 80% can be recovered without interference with fertiliser production. At an annual production of 130 million tons, phosphate rock represents an important source of lanthanides. The different methods of recovery are reviewed.