共查询到20条相似文献,搜索用时 15 毫秒
1.
Wet iron-sulfur minerals have been shown to be ideal environments to allow for simple chemical reactions to occur in nature, for instance, in the framework of prebiotic chemistry. Yet, not much is known about such water/mineral interfaces beyond those involving pyrite, FeS(2), which is, however, chemically rather inert. In contrast, mackinawite is chemically reactive and consists of a layered crystal structure comprising FeS sheets that can be easily cleaved. Here, the properties of water confined between such sheets in lamella-like setups is investigated in the spirit of surface science model systems. The properties of this intercalated water are found to depend significantly on the interlayer distance and change from "arrested water" (in the limit of small interlayer distances) to liquid-like behavior. 相似文献
2.
In this study,natural mackinawite (Fe S),a chalcophilic mineral,was utilized to prepare iron/copper bimetallic oxides (Cu O@FexOy) by displacement plating and calcination process.Various characterization methods prove that Cu0is successfully coated on the surface of Fe S,which were further oxidized to Cu O,Fe3O4and/or Fe2O3during calcination process,respectively.Cu O@FexOyperformed highly efficient... 相似文献
3.
We here report the enhancement of a sonochemical effect (chemical reaction induced by ultrasound irradiation) by a Pt black catalyst; the sonochemical reduction of the highly stable U(VI) was demonstrated using this catalytic reaction. 相似文献
4.
The U(III) mixed-sandwich compound [U(eta-Cp)(eta-C(8)H(4)[Si(i)Pr(3)-1,4](2))] 1 may be prepared by sequential reaction of UI(3) with KCp followed by K(2)[C(8)H(4)[Si(i)Pr(3)-1,4](2)], and has been crystallographically characterized. 1 reacts reversibly with dinitrogen to afford dimeric [[U(eta-Cp)(eta-C(8)H(4)[Si(i)Pr(3)-1,4](2))](2)(mu-eta(2):eta(2)-N(2))] 2, whose X-ray crystal structure reveals a sideways-bound, bridging diazenido (N(2)(2-)) ligand. 相似文献
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Hu Yue Zhi Meiting Zeng Ziqing Lu Wenguan Lai Yinlong Wang Xiaobing 《Research on Chemical Intermediates》2022,48(3):935-948
Research on Chemical Intermediates - In this study, the removal of Cr(VI) using commercial FeS with the partially oxidized surface was investigated under visible light. The results demonstrated... 相似文献
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Kazemi Faramarz Arianpour Farzin Rezaie Hamid Reza 《Journal of Thermal Analysis and Calorimetry》2020,139(1):67-73
Journal of Thermal Analysis and Calorimetry - In this research, formation mechanism and kinetics of vacuum carbothermal synthesis of zirconium carbide using zirconium acetate and sucrose are... 相似文献
9.
Odoh SO Pan QJ Shamov GA Wang F Fayek M Schreckenbach G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(23):7117-7127
To provide insights into the adsorption and photoreduction of uranium(VI) on TiO(2), we have studied the structural and electronic properties of uranium(VI) aquo complexes adsorbed on stoichiometric and defected TiO(2) surfaces and nanoparticles. Plane wave calculations with the pure PBE density functional and the PBE+U approach were used to study U(VI) complexes on a periodic rutile (110) slab. In addition, a nanoparticulate Ti(38)O(76) cluster was used to simulate anatase nanoparticles. The electronic structures of the adsorbed U(VI) complexes indicate that the photoreduction process is a consequence of the photocatalytic properties of TiO(2). The reduction of the adsorbed complexes can only occur if the energy of the incident photon exceeds the semiconductor band gap. The gap states induced by single or neighboring hydrogen atoms and oxygen vacancies at the rutile (110) surface cannot reduce adsorbed U(VI) complexes as the unoccupied 5f orbitals are found deeper in the conduction band. In the absence of a solid substrate, photoreduction proceeds by abstraction of a hydrogen atom from water or organic molecules present in solution. Photoreduction by chlorophenol results in lower product yield than reduction by aliphatic alcohols. This is because the triplet uranyl-chlorophenol complex is much more stable than similar complexes formed with methanol and ethanol. In the case of water, the hydroxyl photoproduct easily re-oxidizes the pentavalent species formed. In addition, it is easier for the triplet uranyl-water complex to decompose to the photoreactants. 相似文献
10.
In developing a method for possible low level isotopic enrichment, which uses to advantage the equilibrium isotope effect
observed during U(1V)-U(VI) electron exchange reaction in sulphate solutions, details of a solvent extraction process involving
high concentration of a mixture of U(IV) and U(VI) and at low acid concentrations, are described. The extraction behaviour
of uranium under these conditions is discussed. During the extraction with amines, U(IV) tended to get oxidised in sulphate
solutions. 相似文献
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H. M. Abdunnabi A. V. Ananyev N. N. Krot 《Journal of Radioanalytical and Nuclear Chemistry》1994,186(1):89-97
The process of platinum-catalyzed uranium(VI) reduction with hydrazine in sulfuric acid media has been studied. The influence of sulfuric acid and hydrazine concentrations, and temperature on the reaction rate were investigated. A new reaction mechanism is proposed. The process allows to obtain pure U(IV) sulfate solutions with concentrations of up to 0.3 mol·l–1. Further increase of initial U(VI) concentrations is limited by the reductant solubility in sulfuric acid media. 相似文献
13.
The extraction of uranium(VI) with bis(hexylsulfinyl)methane (BHxSM) from nitric acid aqueous solution has been investigated. It was found that the extraction increased with increasing nitric acid concentration up 8.5 mol/l and then decreased. Extraction distribution ratio also increased with the bis(hexylsulfinyl)methane concentration. The extraction species appear to be UO2(NO3)2
.2BHxSM. The influences of temperature, salting-out concentration and oxalate concentration on the extraction equilibrium were also investigated, and the enthalpy of the extraction reaction was obtained. The result shows that the reaction of uranium(VI) extraction with BHxSM is an exothermic one. 相似文献
14.
Mary Xavier P. R. Nair K. V. Lohithakshan S. G. Marathe H. C. Jain 《Journal of Radioanalytical and Nuclear Chemistry》1991,148(2):251-256
A method is described for the determination of uranium in the presence of iron and plutonium. Ti(III) is used as the reductant in a mixture of H2SO4 and HNO3. Fe(II) and Pu(III) are selectively oxidized by the nitrous acid generated in the reaction between Ti(III) and HNO3. The U(IV) is determined by titration with K2Cr2O7 using biamperometry to detect the end point. The method is applicable to a variety of nuclear materials encountered at different stages of the nuclear fuel cycle and has no bias. The precision of the method is evaluated at different levels from 100 microgram to 100 milligram. The method is simple, rapid and convenient. 相似文献
15.
Y.-Z. Wei B. Fang T. Arai M. Kumagai 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(2):409-415
Electrochemical reduction of U(VI) in nitric acid-hydrazine solution is greatly influenced by the concentration of nitric
acid. In low acidity nitric acid solution such as 0.1M (M=mol/dm3) HNO3, U(VI) was firstly reduced to U(V) and then partially reduced to U(IV). In high acidity nitric acid solution, e.g., 3-6M
HNO3, an electrode process of two-electron transfer was involved in the reduction of U(VI). A higher U(IV) yield could be achieved
in nitric acid solution with higher concentration. Hydrazine was very effective in suppressing the reduction of concentrated
nitric acid, and the optimal concentration of hydrazine added was 0.075 to 0.15M in 6M HNO3
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Yang Yan-Zhao Liu Wen-Tao Han Jian Zeng Shan Sun Si-Xiu 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(3):647-651
The kinetics and mechanism of uranium(VI) extraction from nitric acid solution by bis(octylsulfinyl)methane (BOSM) are studied
with the method of stationary interface cell. The effects of temperature, extractant and nitric acid concentrations are discussed.
The results showed that the extraction process is controlled by the following reaction: UO2(NO3)2 + BOSM(i)⇄k1
k-1UO2(NO3)2BOSM(i). The variation of enthalpy associated with the extraction is -22.1±2.1 kJ/mol.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1979,35(3):213-216
The compositions of the equilibrium vapors above U(BH4)4 and U(BD4)4 at 23° were analyzed by mass spectrometry and only monomeric molecular ions, U(BH4-x)y+, were detected. Infrared spectra for the molecules were recorded in the frequency range 4000-200 cm−1 for vapors contained in a variable path (1–20m) cell at 23°, from inert gas, low temperature matrices and low temperature thin-films. The data collected in this study are correlated with previously recorded data from vapors of U(BH4)4 generated at 40–50°. Several spectral features pertinent to the eventual complete vibrational spectroscopic definition of U(BH4)4 and U(BD4)4 are discussed. 相似文献
18.
The capacity for anaerobic decolorization of a sulfonated azo dye, Congo Red, by a strain of a sulfate-reducing bacterium
was evaluated. After optimizing the growth rate of the bacteria on a simple carbon source and terminal electron acceptor pair,
lactate and sulfate, respectively, the effect of the dye concentration on their growth rate was analyzed. The decolorization
rate was affected by the dye concentration in the growth medium. The azo-bond cleavage mechanism of reductive decolorization
with the formation of benzidine was consistent with the results, as this metabolite was identified by high-performance liquid
chromatography. Several fractions of the culture medium, including lysed cell extracts, were examined for the capacity to
reduce the azo dye. This reduction capacity was found in the culture medium in which the cells had previously grown. The results
showed that the mechanism of reductive decolorization of this sulfonated azo dye was extracellular and nonenzymatic, consistent
with the production of sulfide anion by the microorganisms while growing on lactate and sulfate. The sulfide anions were the
cause of the reduction leading to the disappearance of color in the medium. To increase the rate of decolorization, the presence
of ferrous ion was also necessary together with the lactate and sulfate substrates. 相似文献
19.
The highly reactive, six-coordinate tris-aryloxide U(III) species, [((t-BuArO)3tacn)U] (1) reacts with CO2 in a 2e- reduction to produce CO and a dinuclear U(IV/IV) mu-oxygen bridged complex [{((t-BuArO)3tacn)U}2(mu-O)] (2). This reaction proceeds via a dinuclear CO2-bridged intermediate 3. Also, mononuclear 1 was treated with 1 atm of CO to yield dinuclear [{((t-BuArO)3tacn)U}2(mu-CO)] (4) with a CO ligand bridging two uranium ions in an unprecedented mu:eta1,eta1 fashion. The mixed-valent azido-bridged U(III/IV) complex 5 was synthesized from trivalent 1 and tetravalent [((t-BuArO)3tacn)U(N3)] and serves as an isostructural analogue of triatomic-bridged intermediate 3 as well as an electronic model for mixed-valent 4. 相似文献