M. S. Mel’gunov

Processing of organochlorine waste components on bulk metal catalysts

A method for destroying chloroorganic waste components on catalysts, particularly bulk metal nickel (99.99%), nichrome (80% Ni and 20% Cr), and chromel (90% Ni and 10% Cr) is proposed. The process is accompanied by the formation of carbon nanofibers (CNFs) with feathery morphology. Catalytic destruction of 1,2-dichloroethane on bulk nickel catalysts is characterized by a long induction period (∼3 h) with spontaneous activation of the alloy’s surface. Preactivation of the catalyst with acids or by alternative treatment in oxidizing and reducing environments shortens the induction period by one order of magnitude. The state of the surface before and after activation is studied by SEM, TEM, and EDX. The activity of catalysts is determined for the decomposition of 1,2-dichloroethane at temperatures of 500 to 700°C. Nichrome exhibited the greatest activity (yield of CNFs, 400 g/g of catalyst); the yield of CNFs on catalysts prepared by coprecipitation and mechanical activation was considerably lower. The proposed approach combines organochlorine waste disposal with the production of a useful product (CNFs). The use of bulk metal catalysts is promising since it simplifies the technology for their preparation, and the absence of carriers makes it easy to cleanse CNFs of impurities of catalyst fragments.

A capillary gas chromatographic column with a porous layer based on a mesoporous material

A procedure for synthesizing an MSM-41-type mesoporous mesophase material (MMM) layer, that is, a layer of a solid porous material with a regular arrangement of nanoscale calibrated pores and a unified geometry, on the inner wall of a capillary column was developed. Because of the high specific surface area of silica, capillary columns with a porous MMM layer on the basis of silica allow the amount of samples introduced to be increased by an order of magnitude compared with the known capillary porous-layer columns. An example of the separation of light hydrocarbons is described. The properties of columns with MMM porous layers are discussed.

Synthesis of titanium oxide structures on mesoporous silicon dioxide surface by molecular layering

The formation of titanium oxide structures through the repeated successive treatment of SBA-15 mesoporous silicon dioxide with vapors of TiCl4 and H2O at 200°C is investigated. The influence of the number of synthesis cycles on the character of the buildup of the surface titanium oxide structures and changes in the adsorption and structural characteristics of modified silica is shown.

“Hot” particles of the Yenisei River: Radioisotope composition, structure, and behavior in natural conditions

The radioisotope compositions, structure, and behavior of “hot” particles under the natural conditions of the Yenisei River in the nearby influence zone of Krasnoyarsk mining and chemical combine were examined in this study. By the composition of gamma-radiating isotopes, all particles are divided into three groups: mono-isotopic, bi-isotopic and poly-isotopic. Mono-isotopic “hot” particles, containing only 60Co were discovered for the first time. Transuranium elements (241Am and 243Cm) were revealed in poly-isotopic particles. Investigation of poly-isotopic particles by means of a scan electron microscope showed that the presence of UO2 together with the lack of activation of 152Eu testifies to the reactor origin of this particle. Experiments showed that in natural conditions “hot” particles under the influence of filtrating water and moisture of pore solutions are gradually dissolved and radionuclides are repeatedly drawn into migration.

Effect of the concentration of aluminum on the adsorption, texture, and structure characteristics of a mesoporous mineral mesophase of the SBA-15 type

The effect of Al ion implantation on the properties of mesoporous aluminosilicate mineral phases of the SBA-15 type was studied. The implantation of Al was performed immediately under conditions of the synthesis of SBA-15 in a weakly acidic medium (pH ∼ 2.9). It was found that, under these conditions, the amount of Al that can be implanted into the SBA-15 framework is limited (a maximum of 7.2 mol %). According to XPS data, aluminum ions were implanted into the matrix of silica rather than occurring on the surface as an individual phase. The study of nitrogen adsorption at 77 K and the results obtained by X-ray diffractometry and high-resolution electron microscopy suggest that Al-SBA-15 materials exhibited a hexagonal structure of channel pores of the same diameter of 8.3 nm, and the unit cell parameter was 12.3 nm. The degree of crystallinity of the material increased with the concentration of Al.

High-shrinkage-potential porous glass-ceramic supports for high-temperature oxide ceramic membranes

We have optimized the composition of porous glass-ceramic supports compatible with conducting ceramics and have developed a procedure for the fabrication of such supports. High-shrinkage-potential porous supports in the form of dead-end tubes have been shown to be best suited for designing multilayered selective ceramic membranes. We have assessed the effects of various modifiers on the shrinkage curve of such supports. The factors that play a central role in determining the properties of supports have been identified: the amount of burnout additives determines the macroporosity, the addition of low-melting clay influences the shrinkage potential, leaching influences the microporosity, impregnation with a lanthanum salt determines the shape of the shrinkage curve and reactivity, and modification with Al2O3 sol determines the heat resistance of the supports.

Artificial radioactivity of the White Sea

Vertical profiles of 137Cs in bottom sediments collected from various sites of the White Sea are reported. From these profiles, the 137Cs inventory in the bulk of sediment was estimated to be 270–3300 Bq m−2, and the surface contamination of sediment, 7.1–46.5 Bq kg−1. In the most of the sediment cores, 137Cs was detected to a depth of >20 cm. The highest activity of 137Cs was usually observed in the 1–2-cm layer. The mean specific radioactivity of 137Cs in the seawater was 4.1 Bq m−3.

Size effects in photoexcitation of triplet states of ammonium tetraphenylborate

This paper reports on the results of complex investigations of photoexcited states of ammonium tetraphenylborate, which are characterized by self-sensitized luminescence. It has been established that the excitation by UV light at 77 K leads to the formation of stable triplet states due to the capture of electrons on electron traps. The EPR and luminescence excitation spectra exhibit the formation of a set of triplet states with different distances between electrons and holes. The performed investigations give grounds to affirm that, in bulk samples, cations in the structure of ammonium tetraphenylborate are electron traps. When the size of the ammonium tetraphenylborate sample is changed to 6 and 3 nm, the capture of excited electrons on sorbed oxygen molecules becomes dominant. In this case, the appearance of the spectrum of O2− anion radicals has been detected by the EPR method. The proposed interpretation of the observed effects has been confirmed by the thermoluminescence data on the recombination of electron-hole pairs, which correlate with a change in the intensity of the EPR spectra during annealing.

Behavior of 137Cs in the soil-rhizosphere-plant system (by the example of the Yenisei River floodplain)

Abstract137Cs speciation and distribution in the components of the biogeocenosis of the Yenisei River floodplain such as soils, rhizosphere, and plants were studied. The study was carried out near zones of influence by the Krasnoyarsk Mining and Chemical Combine (MCC). Variation in the specific activity of radionuclides with increasing distance from the pollution source and its ratio in the soil and rhizosphere and distribution in the plant body were studied. A variety of occurrence forms of 137Cs, including mobile ones, was revealed. The amount of 137Cs leached from plants during flooding was calculated from the results of laboratory experiments.

Study of chromium ion sorption on modified silica ordered materials

The sensitivity of chemical sensors depends on the number of receptors on the surface; hence, an important role is played by the accessible support surface. Films based on silica mesoporous mesophase materials feature the highest specific surface area for silica materials, and their walls can be modified by various functional groups. In this paper, we propose to use mesoporous mesophase films as supports of sensitive elements for Cr3+ ions.