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2014, №1

pp. 4-11

Articles

Morphology of acrylonitrile copolymers with methylacrylate and itaconic acid, as well as with its derivatives, obtained in supercritical carbon dioxide media

A.V. Shlyakhtin, I.E. Nifant'ev, D.A. Lemenovskii, D.P. Krut'ko, V.V. Bagrov, P.S. Timashev, V.K. Popov, V.N. Bagratashvili.

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Key words: carbon dioxide, polyacrylonitrile, itaconic acid, polymerization, particles

Ternary copolymers of acrylonitrile with methylacrylate and itaconic acids and with derivatives of the latter — monomethyl ester (MME), monoethyl ester (MEE), monoamide, mono-n-octylamide, are synthesized in supercritical carbon dioxide medium. The morphology of the obtained copolymers is investigated using scanning electron microscopy. Copolymers with itaconic acid, its MME and MEE form regular particles of about 1 μm size with no addition of any stabilizer.

2014, №1

pp. 12-28

Articles

Key words: liptobiolith coal, supercritical water, liquefaction, desulfurization, kinetics and mechanisms of reactions

Liquefaction of liptobiolith coal in steam and supercritical water (SCW) flow at constant increase of temperature from 300 up to 470 °C is studied. Temperature dependencies of the yield of liquid and volatile products and apparent kinetic parameters of the process are obtained. The yields of oil, resin, asphaltene and volatile products are estimated as 23.2, 16.1, 5.1 and 14.1% of the coal organic matter (COM), respectively. Participation of water molecules in thermochemical transformations of COM resulted in the 13.2% wt. increase of oxygen amount in the conversion products and residue.

2014, №1

pp. 29-39

Articles

Structure and properties of ultrahigh molecular weight polyethylene containing silver nanoparticles

P.S. Timashev, N.V. Minaev, D.V. Terehin, E.V. Kuznetsov, V.V. Malinovskaya, V.V. Parfenov, V.N. Bagratashvili, O.P. Parenago.

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Key words: supercritical carbon dioxide, ultrahigh molecular weight polyethylene, organometallic precursor, modification, nanoindentation, tribology characteristics, friction coefficient

Microstructure and mechanical properties of ultrahigh molecular weight polyethylene (UHMWPE) containing metallic silver nanoparticles introduced via impregnation with Ag-containing precursor in supercritical carbon dioxide are studied. The nanoindentation experiments showed that the elastic modulus of silver-containing composites increases by 40—50% compared to the initial UHMWPE samples, while the hardness of modified samples remains largely unchanged. Measured values of friction coefficients for the initial and modified polymers are comparable at loads ranging from 50 to 400 N.

2014, №1

pp. 40-47

Articles

Oxidative treatment of waste water formed during cellulose production from rape straw in supercritical conditions

E.Sh. Gayazova, R.A. Usmanov, I.G. Shayhiev, F.M. Gumerov, R.Z. Musin, S.V. Fridland.

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Key words: oxidation in supercritical water, waste water treatment, cellulose production, coagulation, flocculation

The method of oxidative waste water (WW) treatment in the supercritical conditions (SC) is considered. It is demonstrated that the values of water parameters required for the downstream biological purification are accessible if coagulation-flocculation treatment of WW on the first stage is combined with oxidation in the SC on the second stage. The necessity of such combination is caused by low degree of lignin degradation in the conditions of oxidative treatment (400 °C, 24 MPa, Н2О2 as oxidant).

2014, №1

pp. 48-54

Articles

Key words: photochromism, spirocompounds, SCF impregnation, luminescence, electron-donor compounds

Aromatic electron-donor compounds (EDC) (such as toluene and dibutyl phthalate) are found to affect the content of photochromic spiroantrooxazine (SAO) and to control the ratio of its colored forms (B and Bx) introduced into thermoplastic polymeric matrixes (e.g. polyvinylchloride and F-42 fluoroplast) using the supercritical fluid impregnation (SCFI). The presence of EDC in impregnated polymers induces the reciprocal transformations of the SAO colored form B and Bx and increases the rate their «dark» bleaching.

2014, №1

pp. 55-61

Articles

Key words: supercritical fluid extraction, liquid and/or supercritical carbon dioxide, spent nuclear fuel reprocessing, uranium, fission products, complexation, tributyl phosphate, aqueous ferric nitrate solution

The behavior of uranium and simulators of fission products during the reprocessing of a model spent nuclear fuel in subacidic ferric nitrate solution using supercritical carbon dioxide containing tributyl phosphate (TBP) is studied. A quantitative isolation of uranium from the ferric nitrate solution simultaneously with its separation from the present fission products can be reached in these conditions. Isolation of uranium from the TBP phase was performed by its back extraction by water hydrogen peroxide solution simultaneously with preci pitation in the form of uranium peroxide. A high efficiency of uranium purification from all fission products is achieved, which allows one to reuse uranium in a nuclear fuel cycle.

2014, №1

pp. 62-79

Articles

Key words: asphaltite, supercritical water, aluminum, hydrogenation, desulfurization

The conversion of asphaltite (gross-formula CH1.23N0.017S0.037O0.01) in supercritical water (SCW) flow at 400 °C and 30 MPa with and without addition of aluminum shavings is investigated. Composition and amount of products and insoluble conversion residue are determined by means of liquid-adsorption chromatography, elemental analysis, IR and NMR 1H spectroscopy, mass spectrometry and gas chromatography/mass spectrometry. It is found out that SCW not only dissolves asphaltite components, but it participates in redox reactions. Hydrogen and heat evolution during the aluminum oxidation by SCW provide for in situ hydrogenation of asphaltite, increase the fraction of aromatic and polyaromatic compounds in liquid products and decrease the yield of insoluble conversion residue from 44.5 to 11.3 %. If aluminum is added, the degree of asphaltite desulfurization, as a result of sulfur removal in the form of H2S, increases by more than 3.5 times.

2014, №1

pp. 80-85

Articles

Key words: inactivation, Escherichia coli, CO2, tetrafluoroethane, ethanol

The kinetics of E. coli bacteria inactivation is studied in compressed carbon dioxide and tetrafluoroethane with and without ethanol addition. The possibility of decreasing the number of survived cells by 7 orders of magnitude when up to 5% vol. of ethanol is added to the main fluid is demonstrated.

2014, №1

pp. 86-94

Articles

Cleaning of cantilevers for atomic force microscopy in supercritical carbon dioxide

P.S. Timashev, S.L. Kotova, N.N. Glagolev, N.A. Aksenova, A.B. Solovieva, V.N. Bagratashvili.

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Key words: atomic force microscopy, cantilevers, surface cleaning, supercritical carbon dioxide

A new method for gentle cleaning of cantilevers used in the atomic force microscopy (AFM) in supercritical carbon dioxide (SC-CO2) is suggested. Artificial organic pollutant (polyethylmetacrilate) can be removed by treatment in SC-CO2 without any damage of the sample structure and operational characteristics. Using Raman spectroscopy and scanning electron microscopy a complete removal of the pollutant from the sample surface is proven. After treatment in SC-CO2 no bands attributed to the organic pollutant are present in Raman spectra. The images of calibration grids obtained using the SC-CO2 treated cantilevers are more sharp and clear compared to those obtained using the same cantilevers in «as obtained» state without any treatment; the number of artifact features on the images obtained using the SC-CO2 treated cantilevers is also lower.