Facilitated transport of palladium(II) across polymer inclusion membrane with ammonium ionic liquid as effective carrier

This work focuses on the application of polymer inclusion membrane (PIM) with tricaprylmethylammonium thiosalicylate, [A336][TS] (TOMATS), a thiol-containing task-specific ionic liquid for the transport of Pd(II) ions from aqueous solutions. 0.3 M thiourea in 0.1 M hydrochloric acid was found the most effective stripping phase in the transport of Pd(II) from membrane phase containing TOMATS. Separation of Pd(II) ions was also carried out from hydrochloric acid solution containing Pt(IV), Fe(III), Ni(II), and Mn(II). Pd(II) ions were preferably transported in the presence of these metal ions. The separation coefficients followed the order: S _Pd/Pt < S _Pd/Fe < S _Pd/Ni < S _Pd/Mn. [A336][TS] proved to be an excellent ion carrier for Pd(II) from hydrochloric acid solution. The results also showed that transport efficiency of the PIM was reproducible and it can be useful for the development of the simple and highly effective method of Pd(II) recovery from leach liquor of spent catalysts.     

The Staudinger reaction of platinum(II)- and palladium(II)-coordinated 2-(azidomethyl)phenyl isocyanide. X-ray structure of trans-[PtCl{(H)}(PPh3)2][BF4] · CDCl3 · H2O

2-(Azidomethyl)phenyl isocyanide, 2-(CH₂N₃)C₆H₄NC (AziNC), coordinates to some cationic Pt(II) and Pd(II) species to afford isocyanide complexes of the type trans-[MCl(AziNC)(PPh₃)₂][BF₄] (M=Pt, l; Pd, 2). AziNC is coordinated also in some neutral Pt(II) and Pd(II) species such as [MCl₂(AziNC)₂] (M=Pt, 3; Pd, 4) derived from the reactions of 2 equiv. of AziNC with [PtCl₂(COD)] and [PdCl₂(MeCN)₂], respectively. Complexes 1 and 2 react with 1 equiv. of PPh₃ affording the heterocyclic carbene complexes trans-[MCl{(H)}(PPh₃)₂][BF₄] (M=Pt, 5; Pd, 6). Complexes 3 and 4 react with 1 equiv. of PPh₃ displacing the isocyanide with the formation of the complexes cis-[MCl₂(AziNC)(PPh₃)] (M=Pt, 7; Pd, 8). These latter ones react with 2 equiv. of PPh₃ affording as the final products the cationic carbene species trans-[MCl{(H)}(PPh₃)₂][Cl] (M=Pt, 9; Pd, 10). Complex 5 was also characterized by single crystal X-ray diffraction. The carbene complex is square-planar and the angle formed between the platinum square plane and the heterocyclic carbene ligand is 87.9(2)°. The C(1)-N(1) and C(1)-N(2) bond distances in the latter of 1.32(2) and 1.30(2) Å, respectively, are short for a single bond and indicate extensive π-bonding between the nitrogen atoms and the carbene carbon.     

Extraction of U(VI), Th(IV) and some fission products from nitric acid medium by sulfoxides and effect of γ-irradiation on the extraction

The extracting abilities for thorium, uranium and some fission products by five sulfoxides are given. The results show that di(2-ethylhexyl) sulfoxide (DEHSO) is not only completely miscible with kerosene, but also superior to tri-n-butyl phosphate in some properties. The extraction behavior of uranium, thorium and some fission products such as zirconium, niobium and ruthenium from aqueous nitric acid with DEHSO in kerosene has been studied over a wide range of conditions. DEHSO extracted uranium and fission products better than TBP under all conditions and is similar to TBP in extraction of thorium. A study of extraction mechanism indicates that U and Th are extracted as disolvates, whereas HNO₃ is extracted as monosolvate. Extraction of the two actinides decreases with increasing temperature, indicating the extraction to be exothermic. Preliminary studies show that -ray irradiated DEHSO extracts Zr and Nb to a smaller extent than irradiated TBP in the range of 10⁴–10⁷ rad.     

Potentiometric study of the kinetics and equilibria of formation of chloroglycinate palladium(II) complexes from bis-glycinato palladium(II) complexes

The equilibria and kinetics of the reaction of Pd(gly)₂ complexes with hydrogen ions and chloride ions has been studied by a potentiometric method. The underlying idea of the method is the measurement of solution pH as a function of reaction time t using a glass electrode. The solutions used had the following initial compositions: xM Pd(gly)₂, xM Hgly, and 1 M NaCl with x = 1 × 10^?4, 5 × 10^?4, and 1 × 10^?3; initial pH₀ was from ～3.5 to ～4.4. The experimentally determined pH versus t dependences and the rate equation for a pseudo-second-order reaction were used to determine the equilibrium constant of formation of Pd(gly)(Hgly)Cl complexes from Pd(gly)₂ complexes and the observed rate constant for this reaction, k _obs. The dependence of k _obs on the pH of the acid solutions studied was assigned to a change in the sequence of the reactions of addition of a hydrogen ion and a chloride ion to the complex Pd(gly)₂.     

Final purification and concentration of americium/curium separated from high-level reprocessing waste

A cation-exchange cycle has been developed for the recovery and concentration of the Am/Cm product from a DTPA/lactic acid solution used in an extraction process for the isolation and separation of the actinides from lanthanide fission products. The optimum pH region for the sorption of Am³⁺ from 0.05M DTPA/1M lactic acid solutions by strongly acidic cation-exchange resins is pH 0.9–1.0. Maximum usable capacities, heights of the exchange zone, and concentration factors for different resins, cross-linkages and temperatures have been determined. Decontamination factors are given for some fission products, as well as U, Np and Pu.     

Cyclic Voltammetry of 1,1′-bis(Diarylphosphino)metallocenes and Their Complexes with Palladium(II)

Cyclic voltammetry is used to study 1,1-bis(diarylphosphino)metallocenes (PP) [M(⁵-C₅R₄PAr₂)₂] (M = Fe; R = H; Ar = Ph, o-MeOC₆H₄, o-PrOC₆H₄, C₆F₅; M = Fe, R = Me, Ar = Ph; M = Ru, Os; R = H, Ar = Ph) and such Pd(II) complexes with these as neutral dichlorides [(PP)PdCl₂], dication solvates [(PP)Pd(L) _n ]²⁺ (L = H₂O, MeCN), and dication triphenylphosphines containing metal–Pd bond (PP)Pd(PPh₃)]²⁺. The nature of the metallocene metal atom and aryl substituents at phosphor atoms and the formation of a metal–Pd bond affect redox potentials of these compounds. 1,1-bis(Diphenylphosphino)metallocenes [M(⁵-C₅H₄PPh₂)₂] (M = Fe, Ru, Os) feature similar electron-donating properties. Oxidation potentials of Pd(II) complexes can serve as a criterion indicating the formation of a metal–Pd bond.     

Anodic Dissolution of Palladium in Sulfuric Acid: An Electrochemical Quartz Crystal Microbalance Study

Regularities of formation of a palladium oxide layer and its cathodic reduction in 0.5 M H₂SO₄ at 0.5–1.3 V (SHE) are studied by cyclic voltammetry, x-ray photoelectron spectroscopy, and electrochemical quartz crystal microbalance. A pure Pd plate and a 0.5-m-thick Pd coating on gold-sputtered quartz crystal is used for electrochemical and microgravimetric studies. It is shown that a Pd electrode dissolves electrochemically in 0.5 M H₂SO₄ when its potential is cycled between 0.5 and 1.3 V. In the case of 0.5-m-thick Pd coating on the gold substrate, the decrease in the electrode weight during one anodic–cathodic cycle is 1.0–1.5 g/cm². It is suggested that anodic process at 0.5–1.3 V (SHE) represents electrochemical oxidation of palladium, yielding a surface layer of poorly soluble Pd(OH)₂ and/or PdO phases, as expressed by the equation Pd + 2H₂O (Pd(OH)₂/PdO)_s + 2H⁺ + 2e. This surface layer, (Pd(OH)₂/PdO)_s, undergoes reduction during the cathodic process. About 5% of the total amount of ionized palladium dissolve in electrolyte.     

Solvent extraction separation of cesium with dibenzo-24-crown-8 from picrate solution

Cesium (25 g) was extracted with 0.03M DB-24-crown-8 at pH 3.0 from 0.01M picric acid in the presence of 2 ml methanol. It was stripped with 3 M perchloric acid and was determined by atomic absorption spectrophotometry. The nature of the extracted species was 111. Dichloromethane was a suitable diluent. Nitric and perchloric acid were the best stripping agents. Cesium was not only separated from alkali and alkaline earth elements but also from zirconium, hafnium, thorium, usually present in fission products. The method is applicable for determination of cesium from real samples.     

X-ray study of volatile Ni(II), Cu(II), and Pd(II) complexes of β-ketoimine pivalyltrifluoroacetone

Synthesis of volatile complexes based on -ketoimine pivalyltrifluoroacetone, C(CH₃)₃C(NH)CH₂COCF₃, is described. The general formula of the complexes is M(L)₂, where M = Cu, Ni, Pd. Complexes of this kind with Ni and Pd were obtained for the first time. The Cu and Pd complexes were found to be isostructural. A comprehensive crystal-chemical study showed that all structures are molecular and built of trans-complexes. The central atom has a square plane environment. The average M-O and M-N distances are nearly equal in all compounds: 1.84 , 1.92 , and 1.98 for Ni, Cu, and Pd complexes, respectively; the mean values of the O-M-N chelate angles are 93.4°, 91.9°, and 92.7°, respectively.Original Russian Text Copyright © 2004 by I. A. Baidina, G. I. Zharkova, N. V. Pervukhina, S. A. Gromilov, and I. K. IgumenovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 713–722, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

A new synthesis for thermolabile low-valent palladium complexes by electron transfer reactions from nickel(0) to palladium(II) compounds

The nickel(0) complex [Ni(bpy)(cod)] (bpy: 2,2′-bipyridine, cod: cycloocta-1,5-diene) was used as a mild reducing reagent for the synthesis of the extremely reactive low-valent palladium complexes [Pd₂X₂(cod)₂] (1: X = Cl, 2: X = Br), Pd(cod)₂ (3) and Pd(norbornene)₃ (4). The X-ray analysis of 1 showed that the two [Pd(cod)(Cl)] moieties are only connected by a short Pd(I)-Pd(I) bond (bond length: 2.5379(4) Å) with the chloride ions as monodentate ligands. The X-ray structure of 3 which is also known to be an extremely reactive compound could be determined by X-ray diffraction. As expected, the Pd(0) centre is surrounded by the two cod ligands to form a PdC₄ tetrahedron with typical Pd-C bond lengths. The crystal structure of 3 shows it to be very similar to the closely related complexes M(cod)₂ (M: Ni, Pt). The X-ray structure of 4 displays that the Pd(0) centre is in a trigonal planar environment of the three olefin groups. According to ¹H NMR measurements the complexes have the same structure in solution as found in the solid state.     

Determination of the fission-product distribution in SiC coating layer of fuel particles

Summary The stepwise removal of SiC coating layer of the coated fuel particles has been studied with several fused alkalis. Treatment by a mixture of KOH and Na₂CO₃ in the ratio 41 at 800° is most suitable for the removal to determine the distribution of fission products. The distribution of fission products, including gases, can be determined by this method.

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Zusammenfassung Die schrittweise Entfernung der SiC-Schutzschicht von Brennstoffteilchen mit Hilfe geschmolzener Alkalien wurde untersucht. Die Behandlung mit einem Gemisch aus KOH und Na₂CO₃ im Verhältnis 41 bei 800° C eignet sich am besten für die Bestimmung der Verteilung von Spaltungsprodukten einschließlich Gasen in diesen Schutzschichten.

     

Extraction of U(VI), Th(IV) and some fission products from nitric acid by n,n-disubstituted amides and effect of γ-ray irradiation on the extraction

In this work, ten disubstituted amides have been synthesized and the extracting ability for U and Th fission products (mainly Zr, Nb and Ru) and the tendency of third phase formation have been studied. From the preliminary studies, two disubstituted amides, N-octylcaprolactam (OCLA) and N-(2-ethyl) hexylcaprolactam (EHCLA) were chosen for further studies. All studies were compared with those obtained by using TBP under exactly the same conditions. The dependence of aqueous nitric acid concentration, extractant concentration, temperature, -ray irradiation on extraction of Th, U and some fission products were studied. Back extraction of Th and U from organic phases and third phase formation were also studied. The studies of the reaction mechanism indicate that Th and U are extracted as disolvates, whereas HNO₃ is extracted as monosolvate. Extraction distribution of Th and U decrease with increase of temperature, indicating the extraction reaction to be exothermic. Preliminary studies show that OCLA and EHCLA have better -irradiation stabilities compared with TBP.     

Determination of traces of uranium in tungsten and molybdenum by radiochemical neutron activation analysis via the fission product140Ba

A radiochemical separation procedure has been developed to determine traces of uranium in tungsten and molybdenum. In this procedure the fission product¹⁴⁰Ba, as indicator nuclide for uranium, is selectively separated from the matrix activities and from all other long-lived activation and fission products and obtained at high purity. The radionuclide in the final fraction is sufficiently pure so that it can be measured with high counting efficiency by -counting. The separation procedure consists of two steps: a cation-exchange separation to separate barium from the anionic matrix tungste or molybdate, and many other elements. In the second step the Ba-fraction is further purified by precipitation of barium as barium chloride in 8M hydrochloric acid. The precipitate is then dissolved in water for -counting via the Cerenkov effect. The chemical yield for barium is 94.6±2.6%. When samples of 0.1 g, a thermal neutron flux of 2·10¹³ n·cm^–2·s^–1, an irradiation time of 10 hours and a measuring time of 2 hours were applied, then the detection limit of uranium was 4 ng/g.Presented at the 3rd Intern. Conf. on Nuclear and Radiochemistry, Vienna, September 7–11, 1992.     

Studies on the separation of cesium-137 from the acidic fission product waste solutions on a new complex inorganic exchanger (Zr−P-APW)

A new inorganic exchanger zirconiumphosphate-ammonium phosphotungstate (Zr–P-APW) has been synthesized in granular form suitable for column work. TheK _d values for different metal ions were determined and the affinity order was found to be CsRb>Zr>Ce> rare earths. Sodium exchange capacity, pH-titration curve, breakthrough capacities for cesium (both in pure HNO₃ and in different types of simulated nuclear wastes) and elution of cesium from the Zr–P-APW column have been studied. A selective method for the removal of cesium from other radioactive fission products has been developed. The exchanger was found to be stable to a -radiation dose of 10⁸ rads in presence and absence of 2M nitric acid.     

Extractive spectrophotometric determination of palladium from acidic high activity nuclear waste

A simple and rapid method for spectrophotometric determination of palladium from highly acidic and highly radioactive nuclear waste using -benzoin oxime (ABO) as extractant and isobutyl methyl ketone (hexone) as diluent has been developed. The method can be employed over a wide range of nitric acid concentrations and for palladium concentrations in the range of 1·10^–5M to 4·10^–4M in the organic phase. The molar absorptivity was found to be 4·10³l·mol^–1·cm^–1. Influence of various heavy metal ions, fission products and corrosion products was studied. The method was found to give a precision and accuracy better than 4% at 100 g of palladium.     

Shell correction study of fission of doubly charged silver clusters

Fission of doubly charged silver clusters is investigated by the method of shell corrections. The following fission events are considered: Ag ₂₂ ²⁺ → Ag _n ⁺ + Ag _{22 ?n} ⁺ , (n=11, 10, 9, 8); Ag ₂₁ ²⁺ → Ag _n ⁺ + Ag _{21 ?n} ⁺ , (n=10, 9, 8, 7); Ag ₁₈ ²⁺ → Ag _n ⁺ + Ag _{18 ?n} ⁺ , (n=9, 8, 7, 6). It is found that the shell correction energy is comparable to or larger than the deformation energy of the liquid drop. Threshold energies for the fission events are calculated and compared with the experimental abundance spectra obtained by Katakuse et al. (1990). Correspondence between the calculated threshold energies with the shell corrections and the experimental abundance is very good, showing products from lower threshold fission channels yield more abundance. The threshold energies without the shell corrections are almost constant irrespective of the fission channels and cannot explain the experimental abundance. Abundance of some products are too small to be accounted for only by the threshold energies. The low abundance of those products may be explained by the presence of competing fission channels that have similar minimal energy paths. It is found in fission of Ag ₁₈ ²⁺ that the shell correction overwhelms the Coulomb energy and the fission channel to Ag₈ + Ag ₁₀ ²⁺ is preferred over the fission channel to Ag ₈ ⁺ + Ag ₁₀ ⁺ .     

Dosimetric measurement of the disintegration rate of fission products

Investigations on the disintegration rate of fission products of²³⁸U and²³⁹Pu are presented. The intensity of the - and -radiation of fission products were measured continuously in an interval of 1–1300 hours following the fission, offering the possibility for determining the general and specific characteristics of the individual fission products. A universal measuring procedure was elaborated for the rapid in situ determination of the dosimetric features of fission products, which is suitable for the accurate evaluation and prediction of external absorbed dose even in case of fission products of various origin and unknown composition.     

The chemical behaviour of di(2-pyridyl)sulphide,dps. Crystal and molecular structure of μ-di(2-pyridyl)sulphidebis(trans-dichlorotriethylphosphine platinum(II)), [{Pt(PEt3)Cl2}2μ-dps] and its reactivity towards stannylated species

The coordinating ability of the ligand di(2-pyridyl)sulphide, dps, was studied in several situations. Dps behaved as a bidentate chelating agent with SnX4 (X=Cl or Br) and also with Pd and Pt (PdCl2 and K2PtCl4), whereas with [Pt2(PR3)2Cl4], (R = Et or Ph), it formed bridging complexes: [{Pt(PR3)Cl2}2-dps]. The crystal and molecular structure of [{Pt(PEt3)Cl2}2-dps] was determined. This complex, as well as [M(dps)Cl2], (M = Pd or Pt), underwent reactions with SnCl2, which inserts into the M–Cl bonds producing heterobimetallic products, which are important in catalysis.     

Reactivities governed by a single metal atom M in mixed-metal highnuclearity clusters having [Ru5M(C)] core (M = Co, Rh, Pd): Site-nonselective, site-selective, and chemo-selective variations in the SO2-trapping reactions

The SO₂ substitution for a CO ligand of the hexa-nuclear carbonyl complexes having Ru₅M(C) type carbido-metal core, [PPN][Ru₅Co(C)(CO)₁₆] (2), [PPN][Ru₅Rh(C)(CO)₁₆] (3), and Ru₅Pd(C)(CO)₁₆ (4), is dramatically affected by the kind of metal atom M: 2 (M = Co) is reactive but not site-selective, 3 (M = Rh) is reactive and site-selective, whereas 4 (M = Pd) is not reactive at all even though 4 can easily react with PPh₃ to give the substitution products.     

Palladium-Catalyzed Allylation of α-Nitroacetates with Propynes

A novel way to synthesize allylated α-nitroacetates under Pd catalysis has been described. Reactions of propynes with diverse α-nitroacetates in the presence of a catalytic amount of Pd(PPh₃)₄ and HOAc in 1,4-dioxane afforded the corresponding allylated products in good yields. Compared with other known methods, this method of synthesizing allylated α-nitroacetates generated no waste and needed neither a stoichiometric amount of base nor a leaving group.