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971.
Sorption of uranium by non-living water hyacinth roots 总被引:1,自引:0,他引:1
S. Shawky M. Abdel Geleel Ashraf Aly 《Journal of Radioanalytical and Nuclear Chemistry》2005,265(1):81-84
Summary Many studies have shown that water hyacinth (Eichhornia crassipes) roots can be used to accumulate high concentrations of organic as well as inorganic pollutants. They are currently used to remediate aquatic environments and aqueous solutions. In the present study, sorption of uranium from aqueous solutions by using dried roots of water hyacinth has been investigated. The sorption of uranium was examined as a function of initial concentration, pH, weight of roots and contact time. Five different concentrations 20, 40, 60, 80, and 100 μg . ml-1 were used. Sorption proves to be very rapid and depend on pH, weight of roots and concentration of uranium. Maximum sorption capacity of water hyacinth roots was 64,000 U6+ μg/g. The sorption of uranium by water hyacinth roots follows a Langmuir isotherm. 相似文献
972.
Levon A. Tavadyan Gegham Z. Sedrakyan Seyran H. Minasyan Frederick T. Greenaway John R.J. Sorenson 《Transition Metal Chemistry》2004,29(6):684-696
Bioactive copper(II), iron(III), and manganese(II) 3,5-di-i-propylsalicylate (3,5-DIPS) chelates were investigated in order to determine their ability to inhibit the free radical initiated chain reactions leading to the peroxidation of isopropylbenzene (i-PrPh) and ethylbenzene (EtPh). Quantitative kinetic studies of these chelates established the following order of anti-oxidant reactivities: manganese(II)-(3,5-DIPS)2>iron(III)(3,5-DIPS)3>copper(II)2(3,5-DIPS)4> > 3,5-DIPS acid. The mechanism of anti-oxidant reactivity of these three chelates is established as being due, in part, to their chain-breaking capacity resulting from the chemical reduction of the generated peroxyl radical to yield alkybenzenelhydroperoxides via reaction of the 3,5-DIPS ligand with the peroxyl radical. In the case of manganese(II)3,5-di-i-propylsalicylate, the central metalloelement also interacts with the peroxyl radical. The manganese(II)-(3,5-DIPS)2 and copper(II)2(3,5-DIPS)4 chelates were also found to exhibit alkylhydroperoxide pro-oxidative reactivity leading to the formation of the alkylbenzeneperoxyl radical. In addition, the manganese(II) atom underwent oxidation to manganese(III) with the formation of the alkylbenzenehydroperoxide or superoxide with air oxygen oxidation. Amyl acetate and dipropylamine (n-Pr2NH) were added to the reaction mixture to model the biochemical presence of ester or amine cellular components. Addition of amyl acetate to the reaction mixture increased the anti-oxidant reactivity of manganese(II)-(3,5-DIPS)2 while decreasing its pro-oxidant reactivity. The weaker anti-oxidant reactivites of iron(III)(3,5-DIPS)3 and copper(II)2(3,5-DIPS)4 were less affected by the addition of amyl acetate and the pro-oxidant reactivity of copper(II)2(3,5-DIPS)4 was not changed by the addition of amyl acetate, while the pro-oxidant property of iron(III)(3,5-DIPS)3 was eliminated. In contrast to 2,6-di-t-butyl-4-methylphenol, butylated hydroxy toluene (BHT), anti-oxidant reactivities of copper(II), iron(III), and manganese(II) 3,5-DIPS chelates were dramatically enhanced by the addition of n-Pr2NH to the reaction mixture. It is concluded that all three metalloelement chelates react with and remove alkylbenzeneperoxyl radicals and the hydroperoxyl radical. The manganese(II)-(3,5-DIPS)2 and copper(II)2(3,5-DIPS)4 chelates may also be useful in removing hydroperoxides in vivo. These reactivities, in addition to their established superoxide dismutase (SOD)-mimetic and catalase-mimetic reactivities, are suggested to possibly permit anti-oxidant and pro-oxidant reactivities in aqueous and organic cellular compartments. 相似文献
973.
Sigman MB Ghezelbash A Hanrath T Saunders AE Lee F Korgel BA 《Journal of the American Chemical Society》2003,125(51):16050-16057
Cu(2)S nanocrystals with disklike morphologies were synthesized by the solventless thermolysis of a copper alkylthiolate molecular precursor. The nanodisks ranged from circular to hexagonal prisms from 3 to 150 nm in diameter and 3 to 12 nm in thickness depending on the growth conditions. High resolution transmission electron microscopy (HRTEM) revealed the high chalcocite (hexagonal) crystal structure oriented with the c-axis ([001] direction) orthogonal to the favored growth direction. This disk morphology is thermodynamically favored as it allows the extension of the higher energy [100] and [110] surfaces with respect to the [001] planes. The hexagonal prism morphology also appears to relate to increased C-S bond cleavage of adsorbed dodecanethiol along the more energetic [100] facets relative to [001] facets. Monodisperse Cu(2)S nanodisks self-assemble into ribbons of stacked platelets. This solventless approach provides a new technique to synthesize anisotropic metal chalcogenide nanostructures with shapes that depend on both the face-sensitive thermodynamic surface energy and the surface reactivity. 相似文献
974.
M. B. Alamin A. A. Mhapes A. M. Bejey A. Sadek R. H. Atweer K. Dubali Daw M. Saad 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):247-250
Since there is no database in Libya defining the intake of the individuals from different essential (minor and trace) and
toxic elements provided through food, drinking water and aerosol, a project has been proposed with the cooperation of IAEA
to determine the concentration of a number of elements such as Cs, Fe, Cr, Rb, Sc, Se, Co, Zn in the three mentioned sources.
Emphasis was placed on the use of nuclear and nuclear-related techniques. In this paper, the primary results are presented
for the concentration of minor and trace elements in some vegetables, spices and other foods which are widely used in the
Libyan meals. Instrumental neutron activation analysis utilizing a 10 MW water pool reactor and a γ-ray spectroscopy facility
was employed. For quality control, certified reference materials were analyzed simultaneosly with the samples which show good
agreements compared with the certified data. Emphasis was given to both elements iron and zinc for their importance. 相似文献
975.
Ali M. Emran Th E. Boothe R. D. Finn M. M. Vora P. J. Kothari 《Journal of Radioanalytical and Nuclear Chemistry》1985,91(2):277-284
An analytical technique using reversed-phase liquid chromatography has been developed for the determination of urea at quantities as low as 1 ng to quantitate the amount of non-labelled urea produced during the synthesis of no-carrier-added {11C}urea starting from11CN–. As a result, the specific activity of the {11C} urea thus prepared was calculated to be as high as 3.5±0.8 Ci/mol.Research supported in part by PHS Grant NINCDS 1 PO1 NS 15639. 相似文献
976.
A systematic quantum mechanical study of the possible conformations, their relative stabilities, vibrational and electronic
spectra and thermodynamic parameters of methyl-3-methoxy-2-propenoate has been reported for the electronic ground (S0) and first excited (S1) states using time-dependent and time-independent Density Functional Theory (DFT) and RHF methods in extended basis sets.
Detailed studies have been restricted to the E-isomer, which is found to be substantially more stable than the Z-isomer. Four
possible conformers c′Cc, c′Tc, t′Cc, t′Tc, of which the first two are most stable, have been identified in the S0 and S1 states. Electronic excitation to S1 state is accompanied with a reversal in the relative stability of the c′Cc and c′Tc conformers and a substantial reduction
in the rotational barrier between them, as compared with the S0 state. Optimized geometries of these conformers in the S0 and S1 states are being reported. Based on suitably scaled RHF/6-31G** and DFT/6-311G** calculations, assignments have been provided to the fundamental vibrational bands of both these conformers in terms of frequency,
form and intensity of vibrations and potential energy distribution across the symmetry coordinates in the S0 state. A complete interpretation of the electronic spectra of the conformers has been provided. 相似文献
977.
Synthesis and characterization of PVP/AAc copolymer hydrogel and its applications in the removal of heavy metals from aqueous solution 总被引:1,自引:0,他引:1
Chelating poly(vinylpyrrolidone/acrylic acid) (PVP/AAc) copolymer hydrogels were prepared by radiation-induced copolymerization. The effects of preparation parameters such as PVP content in the hydrogel and irradiation dose on the swelling behavior of the hydrogel were studied. The pH dependent swelling was investigated. The thermal stability of the prepared hydrogel and the metal chelated ones was characterized by TGA. The removal of Fe(III), Cu(II), and Mn(II) from aqueous solution by the prepared PVP/AAc chelating hydrogel was examined by batch equilibration technique. The influence of treatment time, pH, and the initial feed concentration on the amount of the metal ions removed was studied. The results show that the removal of the metal ion followed the following order: Fe(III) > Cu(II) > Mn(II). The amounts of the removed metal ions increased with treatment time and pH of the medium. To re-use the hydrogel, the metal ions were stripped by using 2 N HCl. 相似文献
978.
A new phase of ‘organic-inorganic’ composite system, polypyrrole polyantimonic acid, prepared by mixing the inorganic precipitate of hydrated antimony oxide with organic conducting polymer i.e., polypyrrole, providing a novel granular form hybrid cation-exchanger suitable for column operation with better chemical and thermal stability, good ion-exchange capacity, reproducibility and selectivity for heavy metals. The physicochemical properties of this material were studied using elemental analyses, AAS, SEM, XRD, FTIR and simultaneous TGA-DTA studies. Ion-exchange capacity, pH-titrations, elution and distribution behavior were also carried out to characterize the material. Distribution studies revealed the cation-exchange material to be highly selective for Hg(II) and its selectivity was performed by achieving some important binary separations like Hg2+-Zn2+, Hg2+-Ni2+, Hg2+-Cu2+, Hg2+-Fe3+, Hg2+-Cd2+, Hg2+-Mg2+ etc. on its column. Using this electroactive composite material, a new heterogeneous precipitate based selective ion-sensitive membrane electrode was fabricated for the determination of Hg(II) ions in solutions. The membrane electrode is mechanically stable, with a quick response time, and can be operated within a wide pH range. The selectivity coefficients for different cations determined by mixed solution method were found to be less than unity The electrode was also found to be satisfactory in electrometric titrations. 相似文献
979.
Xiaolin Hou K. G. Andersson J. Roed A. Byskov T. Roed 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):133-143
Hairless rats, clothes, human hair, filter paper and water were exposed to gaseous elemental iodine in a glass chamber for
60–120 minutes. The deposition of gaseous elemental iodine on skin and lung of rats, human hair, water, clothes and paper
were investigated by measuring iodine content in the exposed material by epithermal neutron activation analysis (ENAA). For
measurement of the iodine concentration in the chamber air, elemental iodine in the air was collected by continuously sucking
air through an active charcoal column. The trapped iodine in the active charcoal was then determined by ENAA. The measured
deposition velocity in the test chamber of gaseous elemental iodine on skin, clothing, hair and water ranges from 0.006 on
filter paper and water to about 0.05 cm/s on skin and clothes. The variation of elemental iodine concentration in air of the
glass chamber was investigated by collecting and analyzing air samples at various time intervals. The results show that the
variation with time in the concentration of the iodine can be described by an exponential function. 相似文献
980.
Summary Resolution of enantiomeric mixtures of DL-amino acids (Nine) using silica gel layers impregnated with (-)-bruncine is reported.
The solvent system used was Butanol: Acetic acid: Chloroform (3∶1∶4). The diastereomers were formed and hydrolysed, by dilute
HCl spray, on the chromatogram only and the amino acids thus resolved were located by ninhydrin spray. The cross resolution
possibilities of enantiomers were also calculated. 相似文献