Alkyl-substituted 2,6-dioxadiazolylpyridines as selective extractants for trivalent actinides

2,6-di(3-alkyl-1,2,4-oxadiazol-5-yl)pyridines, 2,6-di(5-alkyl-1,3,4-oxadiazol-2-yl)pyridines, and 2,6-di(5-alkyl-1,2,4-oxadiazol-3-yl)pyridines were synthesized and tested for their americium(III)-europium(III) selectivity by liquid-liquid extraction. 0.02M solutions of the compounds extract americium(III) 2-bromohexanoates as monosolvates, AmA₃B, from solutions of pH 2, with an americium(III)-europium(III) separation factor of up to 23. Decreasing the alkyl chain length (butyl < ethyl < methyl) or the polarity of the diluent (chlorobenzene < toluene < tert.-butyl benzene) increased both americium(III) distribution ratio and americium(III)-europium(III) separation factor.     

Acetyl-containing phosphine oxides as extractants for actinides and lanthanides

Extraction capability and selectivity of acetyl-containing phosphine oxides R₂P(O)CMe₂CH₂C(O)Me (R = Pr, Bu, n-C₅H₁₁, n-C₆H₁₃, n-C₈H₁₇, Ph) toward actinides (U^VI, Th^IV) and trivalent lanthanides (La^III, Nd^III, Ho^III, Yb^III) were studied. The new ligands were shown to be more efficient and selective in the extraction of uranium, thorium, and heavy lanthanides from nitric acid solutions into chloroform as compared to the known extractants such as carbamoylphosphine oxide Ph₂P(O)CH₂C(O)NBu₂, trioctylphosphine oxide (n-C₈H₁₇)₃P(O), and tributyl phosphate (n-BuO)₃P(O).     

Carboxylic acids as metal extractants

One of the problems in the extraction of trace elements is that matrix elements must usually be masked, involving the addition of large amounts of extra reagent and thus increasing the risk of contamination. If the maxtrix element is to be removed, an extraction system of high capacity is needed to avoid dilution effects. In this respect, long-chain or substituted carboxylic acids show great promise. A literature review on their use as metal extractants is presented.     

Synthesis of novel phosphonated tripodal ligands for actinides chelation therapy

Efficient synthetic routes for preparation of a new family of aldehyde-bisphosphonate conjugates were presented. These compounds appeared as promising intermediates for incorporation of bisphosphonate moiety in various substrates under mild conditions. We report here a first application to the synthesis of a series of three phosphonated tripods designed for actinides chelation therapy.     

Use of organophosphorus extractants impregnated on silica gel for the extraction chromatographic separation of minor actinides from high level waste solutions

Silica-gel has been used as an inert support for the extraction chromatographic separation of actinides and lanthanides from HNO₃ and synthetic high level waste (HLW) solutions. Silica-gel was impregnated with tri-butyl phosphate (TBP), to yield STBP; 2-ethylhexyl phosphonic acid, mono 2-ethylhexyl ester (KSM-17, equivalent to PC-88A), SKSM; octyl(phenyl)-N,N-diisobutyl carbamoylmethylphosphine oxide (CMPO), SCMPO; and trialkylphosphine oxide (Cyanex-923), SCYN and sorption of Pu(IV), Am(III) and Eu(III) from HNO₃ solutions was studied batchwise. Several parameters, like time of equilibration, HNO₃ and Pu(IV) concentrations were varied. The uptake of Pu(IV) from 3.0M HNO₃ followed the order SCMPO>SCYN>SKSM>STBP. With increasing HNO₃ concentration, D _Pu increased up to 3.0M of HNO₃ for STBP, SKSM and SCMPO and then decreased. In the case of Am and Eu with SCMPO, the D values initially increased between 0.5 to 1.0M of HNO₃, remained constant up to 5.0M and then slightly decreased at 7.5M. Also, the effects of NaNO₃, Nd(III) and U(VI) concentrations on the uptake of Am(III) from HNO₃ solutions were evaluated. With increasing NaNO₃ concentration up to 3.0M, D _Am remained almost constant while it was observed that it decreases drastically by adding Nd(III) or U(VI). The uptake of Pu and Am from synthetic pressurized heavy water reactor high level waste (PHWR-HLW) in presence of high concentrations of uranium and after depleting the uranium content, and finally extraction chromatographic column separation of Pu and Am from U-depleted synthetic PHWR-HLW have been carried out. Using SCMPO, high sorption of Pu, Am and U was obtained from the U-depleted HLW solution. These metal ions were subsequently eluted using various reagents. The sorption results of the metal ions on silica-gel impregnated with several phosphorus based extractants have been compared. The uptake of Am, Pu and rare earths by SCMPO has been compared with those where CMPO was sorbed on Chromosorb-102, Amberchrom CG-71 and styrene divinylbenzene copolymer immobilized in porous silica particles.     

Bisacylated diethylenetriamines as extractants for nonferrous metals from hydrochloric acid solutions

A series of bisacylated polyethylenepolyamines with linear and α-and α,α′-branched substituents were synthesized. The effects of the number of the nitrogen atoms in the polyethylenepolyamine fragment of the reagent and of the length and branching of its alkyl radicals on the extractant distribution between the organic and aqueous phases was studied. The performance characteristics of the extractants, such as the loss with the aqueous phase, hydrolytic stability, back extraction conditions for nonferrous metals, and Zn(II)/Fe(III) and Zn(II)/Cu(II) partition coefficients, were examined.     

Unloaded polyether type polyurethane foams as solid extractants for trace elements

Polyether type polyurethane foams (PU) are regular stacks of solid quasi-spherical membranes produced by the reaction of polyisocyanates with polyols of polyether nature in the presence of a catalyst and a blowing agent. Contrary to conventional membrane separations, where a solid membrane is merely a differentially separating agent, or a transport medium, PU foams, apart from separation and preconcentration, also retain, i.e., sorb the species on, or in the membranes. Therefore, PU foam membranes can be considered to act as true sorbents. The membrane properties of PU foam sorbents offer unique advantages over conventional bulk type granular sorbents in rapid, versatile and effective separations and preconcentrations of different compounds from fluid samples. Unloaded PU foam sorbents have received considerable attention in the separation of different trace inorganic species.     

Application of a novel 1,3-diol with a benzyl backbone as chiral ligand for asymmetric oxidation of sulfides to sulfoxides

A chiral 1,3-diol with a benzyl backbone has been used for the asymmetric oxidation of sulfides to sulfoxides. Moderate to good yields and enantioselectivity (upto 87% ee) have been observed.     

Compartmental Schiff-base ligands as selective double-loaded extractants for copper(II)

The Robson compartmental macrocyclic ligand derived from the condensation of derivatives of 2,6-diformylphenol and diamines has been prepared for the first time in its free ligand form; competitive three-phase transport and two-phase extraction studies confirm high double-loaded selectivity for the binding and delivery of Cu(II).     

Polysulfobetaines as extractants for Sr(II) ions from its aqueous solutions

In the present paper, we communicate sorption of Sr(II) ions on novel polysulfobetaines. N‐vinyl imidazole was modified by crosslinking it with four different crosslinkers: N,N‐methylene bisacrylamide, ethylene glycol dimethacrylate, divinyl benzene, and tripropylene glycol diacrylate. All the crosslinked networks were treated with sodium 2‐bromoethane sulfonate to obtain novel polysulfobetaines. The polymers were characterized by FTIR, elemental analysis and SEM to find evidence of network formation and quaternization. These polymers were used as Sr(II) sorbents. Sr(II) uptake was determined by using a colorimetric method using Rose Bengal anionic dye and 0.1 N HCl as the eluent. SEM‐EDS analysis of Sr(II)‐loaded polymers as well as after elution on treatment with 0.1 N HCl was recorded to ascertain the uptake of Sr(II) ions. The experimental isotherm data were analyzed using the Freundlich and Temkin equations. The experimental data also were analyzed using pseudo‐second order sorption kinetic model. Results show that the equilibrium data fit well in the Freundlich isotherm. Copyright © 2010 John Wiley & Sons, Ltd.     

Electrodeposition of actinides for alpha-spectrometry

The electrodeposition of the actinides U, Th, Pu, Am, and Cm on stainless steel disks was studied. A sodium hydrogen sulphate — sodium sulphate buffer 0.63M in total sulphate and a ratio sodium hydrogen sulphate to total sulphate ranging from 0.16 (pH 1.8) to 0.48 (pH 1.3) allows the quantitative electrodeposition of the given actinides. No actual pH measurement is needed. Moreover, sodium hydrogen sulphate is an excellent substrate for the wet ashing of organic matter prior to electrodeposition. The method is very robust.     

Polydentate neutral organophosphorus compounds as extractants of transplutonium elements

Solvent extraction of ²⁴¹Am, ²⁴⁴Cm, ²⁴⁹Bk, ²⁵²Cf, ²⁵³Es, ^152–154Eu and ²³³U from 1 to 15 M HNO₃ solutions by a number of polydentate neutral organophosphorus compounds has been studied. The effect of the reagents structure on their extraction capacity, and selectivity has been investigated. Extraction by tetraphenylmethylenephosphine dioxide, which proved to be the best reagent studied, has been studied in detail. It is shown that this compound may be used for quantitative group extraction and concentrating of transplutonium elements from 1 to 15 M HNO₃ and from nitrate solutions of arbitrary concentration and acidity.     

Dialkyltin salts as extractants in methods for the determination of arsenic and phosphorus

Dialkyltin salts are suitable as extractants for various oxygen-containing anions. They are particulary powerful for the extraction of arsenate and phosphate ions, but are also useful for liquid-liquid extraction of anions of dibasic acids. It is shown that the high extraction power of these dialkyltin complexes can be explained by formation of innersphere complexes with the extracted anions. A method is proposed for the separation of arsenic, phosphorus and silicon using dialkyltin salts. Applications to the extraction-spectrophotometric determination of phosphorus and arsenic in vanadium and steel, and to extraction/atomic absorption determinations of arsenic and phosphorus in metals and alloys are surveyed. The use of the dialkyltin salts for the neutron activation determination of arsenic and as active components in membranes of ion-selective electrodes for phosphorus(V) and arsenic(V) is demonstrated.     

N,N-Dialkyl amides as extractants for spent fuel reprocessing: an overview

Reprocessing of spent nuclear fuel is vital for the long-term global nuclear power growth and is the major motivation for developing novel separation schemes. Conventionally, PUREX and THOREX processes have been proposed for the reprocessing of U and Th based spent fuels employing tri-n-butyl phosphate (TBP) as extractant. However, based on the experiences gained over last five–six decades on the reprocessing of spent fuels, some major drawbacks of TBP have been identified. Evaluation of alternative extractants is, therefore, desirable which can overcome at least some of these problems. Extensive studies have been carried out on the evaluation of N,N-dialkyl amides as extractants in the back-end of the nuclear fuel cycle for addressing the issues related to the reprocessing of U and Th based spent fuels. Under advanced fuel cycle scenario, efforts are also being made by countries with a developed nuclear technological base to provide safe nuclear power to other countries and to minimize proliferation concerns worldwide. This paper presents an overview of studies carried out in our laboratory on different aspects of reprocessing of U and Th based spent fuels employing N,N-dialkyl amides as extractants.     

Development of novel composite sorbents for the removal of actinides from environmental and analytical solutions

A novel approach to preparing granular sorbents for the separation of actinides has been developed, where the extractant is directly immobilized in an inert matrix. This allows substantially higher extractant loadings in the sorbent than for conventional extraction chromatography resins. This approach utilizes polyacrylonitrile (PAN) as the inert matrix material. The well-known actinide extractant octyl (phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) has been loaded into sorbent granules at extractant loadings from 20 to 33 wt.% CMPO. The porosity of the PAN matrix allows the active material to have rapid and complete access to the solution containing the impurities, resulting in improved kinetics and higher sorption capacities. Sorbents containing CMPO were prepared using PAN as a binding matrix, and tested against commercially available actinide extraction chromatography resins. Direct comparative batch contact tests performed with TRU-Resin^Ò and CMPO-PAN using an INEEL tank waste simulant, resulting in distribution coefficient (K _d) values for Am approximately 2-90 times higher for CMPO-PAN than for TRU-Resin. Batch distribution coefficient (K _d) values for Pu were approximately 60-150 times higher for CMPO-PAN than for the TRU-Resin. Acid dependency curves were generated for Am and Pu with CMPO-PAN over a concentration range of 1 mM to 5M HNO₃.     

用于三价锕镧分离的萃取剂的合成与表征

以6,6'-二氰-2,2'-联吡啶为原料,经两步反应,合成了6,6'二(5,6二乙基-1,2,4-三嗪-3-基)-2,2'-联吡啶.第一步改变条件使反应时间由17d缩短到3d,得到的中间体和目标产物经元素分析、IR,1 HNMR和MS等表征确认.此外,对反应机理进行了初步探讨.     

Lipophilic aminimides possessing an additional ligating group as extractants for heavy metal cations

The title compounds were prepared in good yields by Slagel's method. All compounds obtained were used as agents for liquid-liquid extraction. They showed high affinity for certain heavy metal cations and their extractability depended to a great extent on the ligand structure. This dependence is believed to be due to the chelation of the metal cations between the imino nitrogens and the additional ligating site.