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Results 41 - 50 of 118
41.

A Gas-Chromatography Study of Adsorption Properties of Silica Modified by Stable Nickel Nanoparticles Obtained in Reverse Micelles under frame0-Radiation

L. D. Belyakovaa, S. V. Gornostaevab, N. A. Pavlovac, O. G. Larionova, A. A. Revinaa, and A. V. Bulanovac

 

a Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia

b Mendeleev University of Chemical Technology, Miusskaya pl. 9, Moscow, 125190 Russia

c Samara State University, Samara, Russia

Received June 12, 2007

 

Abstract — Stable nano-sized nickel particles are prepared using the radiation-chemical synthesis in reverse micelles. Adsorption properties of raw silica (silochrome, S-120), the silochrome modified by a micelle-forming compound (AOT), and the silochrome modified by the nano-sized nickel particles are studied using gas chromatography method. The retention times for different test-compounds at different temperatures are determined for these adsorbents. Specific retention volumes of the test-compounds, as well as the thermodynamic adsorption characteristics, are determined. After the modification, the initial adsorption heat for n-hydrocarbons increases, which points out to the higher surface roughness of the modified samples. For the nickel-nanoparticle-modified silica, the contribution of specific interactions of polar compounds is less than that for the unmod-ified silica; this can be explained by screening the active centers (OH-groups) of the silica gel by the metal nano-particles. The silica polarity decreases after the modification. The gas chromatography method allows detecting the difference in the properties of nanocomposites containing Ni- and NiO-nanoparticles.

PACS numbers: 68.43.-h

DOI: 10.1134/S0033173208020094
03/09/2008 | 1156 Hits | Print

42.

A Changed State of Silver Nanoparticles upon the Adsorption of Acrylic Acid and Low-Temperature Treatment

E. A. Kononova, Nghia Nguyen, and I. I. Mikhalenko

 

Peoples Friendship University, ul. Miklukho-Maklaya 6, Moscow, 117923 Russia

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Received June 21, 2007

 

Abstract — Plasma-resonance absorption spectra of silver hydrosol were recorded and analyzed to estimate the influences of acrylic acid (AA) as an additive and subsequent low-temperature treatment (LTT) of the sol at 77K on the state of silver nanoparticles. It was found that AA adsorbs in two forms with different orientations of its molecules. Low-temperature treatment resulted in aggregation of particles because of their more defective surfaces, which is characterized by the damping factor of plasmon vibrations. In the adsorption of AA, the damping factor also increases, but the cryoaggregation of particles decreases.

 

PACS numbers: 68.43.–h

DOI: 10.1134/S0033173208020100
03/09/2008 | 1296 Hits | Print

43.

Adsorption of Oxygen-Containing Compounds at Fluorinated Graphite and Fluorinated Carbon Fiber

 T. M. Roshchina, S. V. Glazkova, N. A. Zubareva, E. A. Tveritinova, and A. D. Khrycheva

 

Department of Chemistry, Moscow State University, Vorob’evy gory 1, Moscow, 119992 Russia

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Received May 17, 2007

 

Abstract — The surface properties of fully fluorinated samples of natural graphite (FG) and carbon fiber (FCF) were studied by gas chromatography, IR spectroscopy, and static adsorption. It was found that for fluorocar-bons, the contributions from the O atom (for ethers) and the OH group (for alcohols) are comparable with the contribution from the methylene unit to the retention parameters, which is typical only of highly homogeneous, hydrophobic, and nonpolar surfaces. Unusual properties of fluorocarbons compared to known hydrophobic adsorbents include weaker adsorption of secondary alcohols than ketones, their dehydrogenation products. An analysis of the retention parameters of isomeric propanols and butanols revealed that the FCF surface is acces-sible to the adsorption of these molecules, and is mainly formed by planar homogeneous fragments. In contrast, the FG structure is porous; the pore width is comparable with the molecule size, which makes the adsorption equilibrium more difficult to reach.

 

PACS numbers: 68.43.–h

DOI: 10.1134/S0033173208020112
03/09/2008 | 1296 Hits | Print

44.

On the Formation of Supramolecular Systems in the Adsorption of Aromatic Compounds at Porous Adsorbents

N. A. Eltekova and Yu. A. Eltekov

 

Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia

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Received June 10, 2007

 

Abstract — Competitive adsorption of anisole, benzaldehyde, benzoic acid, benzene, toluene, and phenol from dilute solutions in n-heptane at three chemically different porous adsorbents was studied by high-performance liquid chromatography (HPLC). The retention times of these compounds were used to calculate the equilibrium constants of the adsorption isotherms, the partition coefficients, and the Gibbs energy changes. The results obtained made it possible to estimate the Gibbs energy changes in the competitive adsorption of arenes leading to the formation of supramolecular surface compounds at cellulose and silica and the formation of arene clusters at the pyrocarbon surface from dilute solutions in n-heptane.

 

PACS numbers: 68.43.-h

DOI: 10.1134/S0033173208020124
03/09/2008 | 1012 Hits | Print

45.

Gas Adsorption at the Components of the GaAs-CdS System

I. A. Kirovskaya

 

Omsk State Technical University, Omsk, Russia

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Received June 13, 2007

Abstract — Adsorption properties of the GaAs–CdS-system solid solutions and binary compounds are studied with respect to CO and NH3 by the piezoelectric quartz microweighing, programmed thermal desorption, and IR-spectroscopy. Based on the experimental dependences (p = f(T), T = f(P), T = f(t)), thermodynamic and kinetic characteristics of adsorption, analysis of the surface chemical composition, the adsorbents’ acid-base and other physicochemical characteristics. With due allowance for electron structure of the adsorbate’s molecules, the mechanism and specifity of adsorption processes are determined as functions of the operation conditions and system composition. By comparing the adsorption properties of the binary compounds (GaAs and CdS) with those of the solid solutions (GaAs)x(CdS)1 frame1 x, their similarities, as well as the specificity of the solid solutions as multicomponent systems, were revealed. Optimal adsorbent compositions to be used in primary transducers in the medicine- and environment-orientated sensors are found.

PACS numbers: 68.43.-h

DOI: 10.1134/S0033173208020136
03/09/2008 | 1035 Hits | Print

46.

Sorption Properties of Fullerene-Modified Activated Carbon  with Respect to Metal Ions

V. V. Samonin1, V. Yu. Nikonova1, and M. L. Podvyaznikov1,2

 

1 St. Petersburg State Technological University, Moskovskii pr. 26, St. Petersburg, 190013 Russia

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2 OAO Zavod Radiotekhnicheskogo Oborudovaniya

 

Received May 28, 2007

Abstract — The prospects of modying of the activated carbon with microamounts of fullerenes, which can enhance its adsorption capacity with respect to metal cations by a factor of 2.5–5, are illustrated. The analysis of experimental data makes it possible to assume that silver ions are reduced on the carbon sorbent surface to metal silver, lead cations are sorbed due to the donor-acceptor interaction, and the copper ion sorption may lead to both the cation reduction to metal copper and the formation of complexes with different ligands preferentially with those containing an amino group.

PACS numbers: 68.43.frame0h

 

DOI: 10.1134/S0033173208020148
03/09/2008 | 928 Hits | Print

47.

Sorption of Hg2+, Nd3+, Dy3+, and Uframe0 Ions at Polysiloxane Xerogels Functionalized with Phosphonic Acid Derivatives

O. A. Dudarko1, V. P. Goncharik1, V. Ya. Semenii2, and Yu. L. Zub1

 

1 Chuiko Institute of Surface Chemistry, National Academy of Sciences of Ukraine,

ul. Generala Naumova 17, Kiev, 03164 Ukraine

2 Institute of Organic Chemistry, National Academy of Sciences of Ukraine, ul. Murmanskaya 5, Kiev, 02094 Ukraine

 

Received June 14, 2007

Abstract — The sorption properties of silicas with mono- and bifunctional surface layers containing the complexing fragment Si(CH2)3NHP(S)(OC2H5)2 were studied. It was found that xerogels synthesized by the solgel method (like mesoporous silicas obtained by the template method) can extract mercury(II) ions from acid-ified solutions (SSC up to 450 mg/g). In a nonporous xerogel with a bifunctional surface layer (P=S/frame1SH), thiol groups proved to be primary sorption sites for Hg2+ ions; part of the ligand groups were inaccessible to metal ions. Xerogels containing the phosphonic acid residues Si(CH2)2P(O)(OH)2 sorbed uranyl and lanthanide ions from their nitrate solutions. The resulting surface complexes contained two (for the Uframe2 ion) or three innersphere ligand groups (for the Nd3+ and Dy3+ ions). The maximum SSCs were 340 mg/g for the uranyl ion and 120 mg/g for the lanthanide ions.

 

PACS numbers: 68.43.-h

DOI: 10.1134/S003317320802015X
03/09/2008 | 872 Hits | Print

48.

Interaction of Freon-22 with Aluminum and Magnesium Oxides

T. S. Minakova1, E. B. Daibova1, L. A. Savel’eva1, and V. S. Zakharenko2

 

1 Tomsk State University, pr. Lenina 36, Tomsk, 634050 Russia

2 Boreskov Institute of Catalysis, pr. Akad. Lavrent’eva 5, Novosibirsk 90, Russia

Received June 14, 2007

 

Abstract — It is known that Freons can be destructively adsorbed by magnesium and calcium oxides under the effect of mild ultraviolet radiation. Insofar as these oxides along with the silicon, aluminum, and iron oxides are typical components of solid tropospheric aerosols, photo- and dark adsorption processes may represent an efficient channel of the Freon removal from the atmosphere. In this work, dark adsorption of Freon-22 on alu-minum and magnesium oxides, which were treated in a vacuum at room temperature, is studied. Experiments with the specimens that have been exposed to air for a long time are especially important in estimating the probable adsorption of a Freon on aluminum or magnesium oxide under conditions close to the tropospheric ones.

PACS numbers: 68.43.-h

DOI: 10.1134/S0033173208020161
03/09/2008 | 947 Hits | Print

49.

Structure and Properties of the Crystalline-Silicon-Dioxide-based Macroporous Ceramics

A. I. Rat’ko, A. I. Ivanets, T. A. Azarova, and S. M. Azarov

 

Institute of General and Inorganic Chemistry, National Academy of Sciences of Belarus,
ul. Surganova 9/1, Minsk, 220072 Belarus

 

Received June 15, 2007

Abstract — Samples of macroporous ceramics based on crystalline silicon dioxide-(the pore diameter >50 m) with superficial membrane layers (the pore diameter 10–20 m) are obtained. They meet the demands to porous materials for filtering. The samples based on the polydisperse powder of crystalline silicon dioxide with granulometric composition 100–315 m, containing 11 wt % of silica-alumina binder, were formed under a pressure of 30 MPa; they demonstrated an optimal combination of porosity and mechanical strength. After thermal treatment the samples’ porosity came to 30%; the ultimate stress (compression) limit, to 35 MPa. It is shown that multilayer elements for filtering, with membrane layers formed of the silicon dioxide powder suspension, provide the water purification from iron impurity (from 1–2 mg/l and down to 0.3 mg/l, a sanitary standard). The elements for filtering with doubly deposited crystalline silica-based membrane layer (the particle size 10–50 m) showed optimal combination of operation characteristics and the purity of water from iron.

PACS numbers: 81.05.Je, Mh

DOI: 10.1134/S0033173208020173
03/09/2008 | 915 Hits | Print

50.

Immobilization of Functionalized Molecules and Nanoparticles in Organic 2D Networks as a Method for the Preparation of Stable Supramolecular Devices

V. V. Arslanov, L. S. Sheinina, and M. A. Kalinina

 

Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia

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Received May 20, 2007

 

Abstract — A novel trend in planar supramolecular chemistry is discussed. The trend relates to development of new methods for the formation of organic 2D networks on the surface of a liquid or a solid, immobilization of functionalized molecules and nanoparticles in them, and creation of highly stable supramolecular devices basedon such systems.

PACS numbers: 81.16.Fg

DOI: 10.1134/S0033173208010013
03/09/2008 | 1110 Hits | Print

  

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