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Abstract  

Selenium nuclides are available from thermal neutron induced nuclear fission of 235U at the gas-jet facility at the Swiss spallation neutron source (SINQ) at Paul Scherrer Institute, Switzerland. The formation of stable selenium compounds, their transport yields using the gas-jet system and their relative thermal decomposition temperature were investigated under oxidizing and reducing conditions in the target chamber. Using O2, H2, CO, and propene as additional gases, the selenium isotopes are suggested to form H2SeO3, H2Se, COSe, and C3H6Se, respectively, with overall 84Se yields of 1.5%, 4.7%, 6.3%, and 21.9%, respectively. Adsorption enthalpy, vapour pressure, solubility and acidity data for these species were collected from the literature or estimated from other known thermochemical properties. Carrier free bromine isotopes (84Br, 86Br) in the form of HOBr were obtained by thermally decomposing H2SeO3 and retaining elemental Se under oxygen rich conditions on quartz at 400 K.

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Abstract  

Extraction of Mo(VI) by 4-(5-nonyl)pyridine (NPy) in benzene from mineral acid solutions containing thiocyanate ions has been investigated at room temperature (23±2°C). From mineral acid (HCl, HNO3, and H2SO4) solutions alone Mo(VI) is not extracted quantitatively while the presence of small amounts of KSCN in the system augments the extraction by a large factor. Stoichiometric studies indicate that ion-pair type complexes (NPyH)2·[MoO2(SCN)4] are responsible for the extraction. Separation factors determined at fixed extraction conditions (0.1M Npy/C6H6–0.1M acid +0.2M KSCN) reveal that Ag(I), Cu(II), Co(II), Zn(II), Hg(II) and U(VI) are co-extracted while a clean separation from alkali metals, alkaline earths and some transition metals like Ln(III), Zr(IV), Hf(IV), Cr(III), Cr(VI) and Ir(III) is possible. Some of the complexing anions like oxalate, citrate, acetate, thiosulfate or ascorbate do not affect the degree of extraction of Mo(VI) allowing it to be recovered from diverse matrices.

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Abstract  

We studied the extraction of phosphomolybdic acid labelled with99Mo and32P and of other species extracted. From the influence of the acidity and of the concentration of excess molybdenum on the distribution coefficient of phosphorus, we propose the following equilibrium for the formation of phosphomolybdate in our experimental conditions

\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$12/7H_6 Mo_7 O_{24} + H_3 PO_4 \rightleftharpoons PMo_{12} O_{40}^{3 - } + 3H^ + + 36/7H_2 O.$$ \end{document}
We show that the best yield of extraction is obtained with isobutyl acetate. From the relation between the quantities of molybdenum and phosphorus extracted, extraction of free molybdenum has been shown. It can be eliminated by washing the organic phase with a 5M HNO3 solution. Subsequently we test a method using radioactive molybdenum, proposed by J. E. KENNEY and M. P. MENON1 for the titration of phosphorus in steels. Because of the presence of interfering elements (Nb, Zr, Ti, V, Si, etc.) specific conditions for the extraction of phosphomolybdic acid have to be found for the application of this method to steels.

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Abstract  

Human, animal (cow, buffalo and goat) and commercial milk powders (for infants and adults) have been analyzed for 5 minor (Na, K, Mg, Cl and P) and 13 trace elements (Cr, Mn, Fe, Co, Cu, Zn, Cd, Hg, As, Se, Sb, Cs and Br) by instrumental and radiochemical neutron activation. Milk standards NIST SRM 1549 and IAEA A-11 along with diet standards RM 8431 a and IAEA H-9 were also analyzed for quality assurance. The method involves thermal neutron irradiation for 10 m, 1 h, 6 h and 1 week in a reactor followed by high resolution -spectrometry. Concentrations of Fe, Co, Zn, Sb, and Se were also determined by radiochemical solvent extraction. Mean concentrations of Na, K, Mg, P, Cl, Fe, Mn and Cu in human milk (colostrum) are comparable with that of a WHO/IAEA study. It has, however, lower contents of toxic trace elements (Cr, Cd, Hg, Br, Se, Sb and As) compared to breast tissue from the same area. Cow milk is richer in Na, K, Cl, Mn and Se but it has comparable amounts of Mg, Zn, Br, Fe and Sb with respect to breast milk. Significant differences have been observed for elemental concentrations of Na, K, P and Fe in commercial formula milk powders for infants and adults. Infant's milk powders contain all the nutrient elements in balanced amounts required for the higher growth rate of a child.

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Abstract  

The order of extraction of Mo(VI) from 1M acid solutions by 5% (v/v) LIX 622 (HL) in benzene is HCl>HNO3>HClO4>H2SO4, and extraction decreases with increasing concentration of HCl and H2SO4, and increases slightly with increasing concentration of HNO3 and HClO4. The extracted species is shown to be MoO2L2 as established by IR data of organic extracts and the extracted species in the solid form. Extraction is almost quantitative at and above 10% LIX 622, and is found to be independent of [Mo(VI)] in the range of 10–4 to 10–3 M. The diluents CCl4, CHCl3 and C6H6 are found to be superior to solvents of high dielectric constant for extraction of Mo(VI). Extraction of uranium(VI) by 10% (v/v) LIX 622 in benzene was found to increase with increasing equilibrium pH (3.0 to 6.0), and becomes quantitative at pH 5.9. Tributyl phosphate acts as a modifier up to 2% (v/v). Thorium(IV) is almost not extracted by LIX 622 or its mixture. Separation of Mo(VI) and U(VI) is feasible.

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Abstract  

The extraction order of Th(IV), U(VI) and Mo(VI) based on pH0.5 values is Mo(VI)>U(VI)>Th(IV). Quantitative extraction has been observed for U(VI) by mixture of 10% (v/v) LIX 84 and 0.1M dibenzoylmethane at pH 4.2 and by mixture of 10% LIX 84 and 0.05M HTTA in the pH range 5.5–7.3 and for Mo(VI) by 10% LIX 84 from chloride media at pH 1.5. The order of extraction of Mo(VI) from 1N acid solutions is HCl>H2SO4>HNO3>HClO4 and extraction decreases very rapidly with increase in the concentration of HCl as compared to that from H2SO4, HNO3 and HClO4 acid solutions. The diluents C6H6, CCl4 and CHCl2 are found to be superior ton-butyl alcohol and isoamyl alcohol for extraction of Mo(VI). Influence of concentration of different anions on the extraction of U(VI) and Mo(VI) has been studied. Very little extraction has been observed in case of Th(IV) by LIX 84 or its mixtures with other chelating extractants or neutral donors.

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Abstract  

We have investigated the behaviour of109Cd, in two-phase systems: (HDEHP–C6 H6/ H3 PO4–HClO4–LiOH, =0.2), as a function of the independent equilibrium parameters which define the system: pH, equilibrium concentration of H3 PO4 and total concentration of HDEHP in the organic phase. The data have been interpreted in terms of the existence of phosphoric complexes characterized by their order 1 with regard to H3 PO4 and their charge z. The l and z. values are: 0<1<2, z=–2, 0, 1, 2 for the following ranges: 0.7<pH<2.7 and CH3 PO4<4M. Stability constants of the predominant complexes have been obtained. Finally, a formulation of these complexes has been proposed on the basis of partial charge of the atoms. Some complexes, could be formulated as hydroxy-phosphoric species, resulting from competition between hydroxy and dihydrogenophosphate anions. In concentrated phosphoric acid (CH3 PO4=4M), complexation of cadmium is not more than 25%.

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Abstract  

The complexes Mn(II), Co(II), Ni(II) and Zn(II) with 4-oxo-4H-1-benzopyran-3-carboxaldehyde were synthesized and characterized by elemental analysis, infrared and UV spectroscopy, X-ray diffraction patterns, magnetic susceptibility, thermal gravimetric analysis, conductivity and also solubility measurements in water, methanol and DMF solution at 298 K. They are polycrystalline compounds with various formula and different ratio of metal ion:ligand. Their formula are following: [MnL2(H2O)](NO3)2·2H2O, [CoL2](NO3)2·3H2O, [NiL2](NO3)2·3H2O, [CuL2](NO3)2·H2O and [ZnL3](NO3)2, where L = C10H6O3. The coordination of metal ions is through oxygen atoms present in 4-position of γ-pyrone ring and of aldehyde group of ligand. Chelates of Mn(II), Co(II), Ni(II) and Cu(II) obey Curie–Weiss law and they are high-spin complexes with the weak ligand fields. The thermal stability of analyzed complexes was studied in air at 293–1,173 K. On the basis of the thermoanalytical curves, it appears that thermal stability of anhydrous analysed chelates changed following: Cu (423 K) < Zn (438 K) ~ Co (440 K) < Ni (468 K). The gaseous products of thermal decomposition of those compounds in air atmosphere are following: CO2, CO, NO2, N2O, hydrocarbons and in case of hydrates also water. The molar conductance data confirm that the all studied complexes are 1:2 electrolytes in DMF solution.

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substitute for the traditional Chlorhydrin and Halcon processes [ 1 , 2 ]. Extensive efforts have been made to develop an alternative process for the direct epoxidation of C 3 H 6 using molecular oxygen as an oxidant. Especially, the approach combining

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Journal of Thermal Analysis and Calorimetry
Authors:
Viorel Cîrcu
,
Ana S. Mocanu
,
Constantin Roşu
,
Doina Manaila-Maximean
, and
Florea Dumitraşcu

, 6.3. 1 H NMR (300 MHz, CDCl 3 ): 8.12 (s, 1H), 7.74–7.51 (m, 12H), 7.42–7.34 (m, 5H), 7.22 (m, 2H), 7.03–6.98 (m, 4H), 6.90 (d, 1H, 4 J = 2.4 Hz), 6.60 (dd, 3 J = 8.4 Hz, 4 J = 2.4 Hz, 1H), 4.04 (m, 4H), 3.89 (s, 3H), 1

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