Home – Home – Jornals – Chemistry for Sustainable Development 2003 number 4

The structures of hundred halogenated metabolites of phenolic nature generated by lichens and fungi are considered. The groups of depsides, depsidones, fungoid metabolites are marked out. The problems related to biological activity are discussed.

Mononuclear halogenated simple phenol compounds and their derivatives formed from mono- and polyhydroxybenzenes are represented in nature by metabolites of insects, fungi, plants and microorganisms living on land and in water. The structures of a hundred compounds of phenol, quinones and cyclitol types, their metabolism and data on their biological activity are considered in the review.

The problem concerning the extraction of the characteristics of methane formation and transport processes from the experimental data is discussed.

Investigation of endemic features of urolithiasis taking into account local factors, both natural and technology-related ones, allows one to obtain additional information about one of the reasons of this disease. Mineral composition and distribution of urinary calculi in patients from Novosibirsk and Omsk Regions are investigated. A common feature of urolithiasis in the regions under comparison is noticeable predominance of oxalate urinary calculi. However, at the conservation of the general trend of distribution with respect to the prevailing component, patients from Novosibirsk Region exhibit an increase in phosphate and decrease in urate urolithiasis. Noticeable differences in paragenesis of minerals comprising multicomponent urinary calculi and in the composition of single-component concretions are observed. In the Novosibirsk samples, single-mineral concretions are more frequently composed of whwellite, while in the Omsk samples it is anhydrous uric acid. Comparative analysis of the mineral composition and distribution of urinary calculi in other regions according to literature data was carried out.

The effect of mechanical activation of amorphous zirconium hydroxide in centrifugal planetary mill on the formation of crystalline zirconia in the presence of Fe³⁺ and Y³⁺ cation additives is investigated. It is established that the pulsed mechanical impact stimulates dehydration and crystallization of the nanosized metastable form of tetragonal zirconia in a mechanochemical apparatus at the room temperature. The solid-phase mechanochemical synthesis proceeds with a high rate through sequential and parallel routes with the intermediate formation of stable monoclinic modification of ZrO₂. Introduction of additives favours the formation of the tetragonal form; in the presence of small amount of Y³⁺ cations, the process is completed within 2_5 min. The formation of metastable phase in the mechanochemical apparatus can occur due to the pulsed mode of powerful mechanical impact, resulting in the creation of thermodynamically and kinetically favourable conditions, and also due to small crystallite size (12_16 nm) as a result of efficient grinding.

Analysis of the distribution of elements in biogeocenoses based on organomineral composts is performed. Introduction of composts of the wastes from plant and cardboard industry, heat-and-power engineering, cattle breeding did not cause accumulation of microelements in soils in concentrations exceeding the phytotoxicity level and maximum permissible values. Differences in microelemental composition of the experimental and reference plants were insignificant. Compost made of the wastes from industry can be used for reclamation of land disturbed by man's impact.

For the efficient use of gases formed in a number of thermochemical procedures of carbon processing, it is necessary to purify them from hazardous impurities, such as H₂S, HCN, NH₃, resinous substances. To purify the gases, it is proposed to use the liquid catalytic procedure with the soluble derivatives of cobalt phthalocyanine as a catalyst. This method allows achieving the required purification extent with low expenses. The purified gases can be used to obtain electricity and heat, and also as chemical raw material for obtaining ammonia, methanol, liquid fuel, etc. Elemental sulphur is obtained as a result of purification.

The effect of particle size of carbonate minerals (dolomite and calcite) on the kinetics of their interaction with water and ferrous sulphate solution is investigated. It is established that the efficiency of solution neutralization is to a noticeable extent determined by the particle size of the reagent. The application of calcite as a material for the construction of artificial geochemical barriers is preferential over dolomite. In the case when reagent consumption is much higher than the stoichiometric amount, or under lengthy interaction (for example, in filtering dams of artificial geochemical barriers) the particle size of the material has no substantial effect.

The aging of freshly precipitated and immediately saturated with a sorbate (Cu(II), Ni(II), Cr(III), Pb(II) and Cd(II) cations) oxyhydroxides of Fe(III), Cr(III), Al(III), Zr(III) and Ti(IV) in 0.25 M solution of NaCl at room temperature is studied. It is established that the aging is accompanied by spontaneous acidification of the oxyhydroxide suspension and by partial desorption of the sorbate, which is to the highest extent exhibited with aluminium oxyhydroxide with Cd sorbed, and by the lowest extent with

The mechanism of decomposition of artificial scheelite in nitric acid is investigated by recording the curves of anodic charging. This method involves fixation of temporal changes in the potential of platinum electrode in reaction medium. It is established that the reaction between artificial scheelite and nitric acid is not a solid-phase process but a usual exchange reaction in aqueous medium with the dissolution of scheelite and formation of precipitate which is tungsten trioxide monohydrate.

Known hypotheses concerning the mechanism of formation of aromatic aldehydes (vanillin and syringaldehyde) in the processes of oxidative cleavage of lignins are discussed. A new mechanism of lignin oxidation is described, which starts from the formation of phenoxyl radical and is completed by the formation of vanillin through the retro-aldol cleavage of substituted coniferyl aldehyde. Oxidation of the model compounds is studied and experimental confirmations of the proposed mechanism are obtained. Coniferyl alcohol, the postulated intermediate of eugenol oxidation, was detected by GC-MS. Comparison of the kinetics and oxidation products of vanillidenacetone and lignosulphonates, eugenol and isoeugenol, guaiacyl ethanol and quaiacyl propanol confirms the proposed mechanism. On its basis, possibilities are found to elevate the selectivity of lignin oxidation by oxygen into aromatic aldehydes by accelerating the process due to tightening conditions.

In relation to the problem of recovery of fission palladium from highly active liquid wastes from spent nuclear fuel reprocessing, the efficiency of a flow sheet based on solvent extraction and electrochemical processes for palladium purification from a number of accompanying elements (Ag, Te, Se, Sb) was tested using model (in the absence of radiation) nitrate-nitrite solutions. The flow sheet is composed of two extraction cycles which involve solvent extraction of palladium with petroleum sulphides, washing of the extracts with acid solutions, and palladium stripping with aqueous ammonia. In the first cycle imitating recovery from HLW, ~99 % Pd and ~25 % Ag is recovered and separation from other accompanying elements is achieved. High efficiency of palladium separation from silver (10⁵) is achieved during the second cycle due to solvent extraction affining from hydrochloric solution. For passing from the ammonia strip liquor of palladium and silver, which is the final product of the first cycle, to the starting hydrochloric solution for the second cycle, electrochemical operations are applied, involving co-deposition of these metals on the cathode followed by their anodic dissolution in HCl solution. The efficiency of these operations was also not less than 99 %. At the final stage, purified palladium is recovered from the strip liquor of the second cycle as a difficultly soluble trans-dichlorodiammine ("palladozammine", PZA). End-to-end palladium fraction extracted with the help of this flow sheet is 97_98 %. No Te, Se or Sb admixtures were detected in the resulting PZA; Ag content is close to the level observed in the reference experiment (mass concentration 10^_5 %).

Intensification of lipid extraction from the seeds of Siberian pine with ethanol by using the electromagnetic field of super high frequency in extraction process is investigated. Physicochemical characteristics of the resulting cedar oil are determined, such as refractive index, numbers: acidic, peroxide, iodine, saponification, colour, and mass fraction of non-lipid admixtures. Fractional and fatty acid composition of the oil is investigated.

Using a multi-stage scheme including different sequences of the stages of magnetic separation, hydrodynamic and granulometric classification, magnetic microspheres of fixed composition containing the magnetic constituent at the level of 95_99 % were separated from the fly ash of coal from the Ekibastuz and Kuznetsk basins. The yield, texture characteristics, macrocomponent and mineral phase composition were determined and globules of three morphological types were described for close-cut fractions of magnetic microspheres. A general dependence of the properties of close-cut fractions of microspheres on ferric oxide content was revealed. It was demonstrated that for the mass concentration of total Fe₂O₃ >60 %, mainly massive microspheres with various crystal microstructure are formed. With a decrease in iron content, the formation of porous microspheres becomes predominant. It is established that the governing factor in the formation of microspheres of morphological type is the viscosity of ferriferous silicate melt.

The composition of Coumarin compounds from roots of Peucedanum morisonii is investigated, 13 individual components are isolated and characterized.