Home – Home – Jornals – Chemistry for Sustainable Development 2002 number 3

The review is dedicated to a small group of natural compounds of a new type - halogenated diterpenoids. These metabolites are synthesized mainly by marine organisms, and only a small part of them have been found in plants, including fungi. Structures of more than 100 compounds have been considered. Data on their biological activity are presented.

Urine concrements were studied in patients from the Donetsk region and piedmonts of the Carpathians Region. The mineral composition of concrements was studied with the help of X-ray and IR spectroscopy methods. A semiquantitative estimation of chemical trace element content of uroliths was carried out by X-ray spectral microprobe technique on a raster electron analysing microscope DS-130 C (Akashi, Japan) and a microanalyser Camebax (France). The results obtained witness to the fact that the main carriers of heavy metals in the concrements are oxalates, phosphates and amorphous organic substance. The distribution of trace elements between concrement components has a complicated pattern. The main carriers of copper, zinc, and manganese are oxalates, however, under certain conditions they may be components of phosphates. Characteristic of lead and iron is isomorphic inclusion into phosphates (apatite). To a smaller degree, they are associated with oxalates. Mercury, and partly lead, zinc, iron and manganese seem to be able to form micrograins in the form of independent phases - calomel, cerussite, hopeite, humboldtine and manganese carbonate. Partially, all heavy metals may be contained in amorphous organic substance.

The liquid - vapour equilibrium is investigated and phase diagrams liquid - vapour are composed for the systems: HCl - SiCl₄ and HCl - SiHCl₃ within temperature range 203-293 K at total pressure P_total = 1.3 atm. The data obtained can be used to choose conditions of HCl desorption from the solutions HCl with chlorosilanes in order to recover HCl from these mixtures.

The data on a and b chlorophyll content of unicellular algae incorporated into the symbiotic association of the Baikal sponges Lubomirskia baicalensis and Baikalospongia bacillifera are obtained by means of microcolumn reverse-phase high-performance liquid chromatography with UV detection. A connection between the number of chlorophylls and the depth of sponge habitat is demonstrated. A stronger decrease of chlorophyll content with depth increase is observed in Lubomirskia baicalensis.

Results of the indirect electrochemical oxidation of thiocyanates in an alkaline medium at different current densities, with Pt anode and gas diffusion cathode generating hydrogen peroxide from oxygen in electrolyzers with cation exchange membranes and without a membrane, are reported.

Weakly basic nitrogen-containing compounds of petroleum from Meso-jurassic deposits of West Siberia are investigated. It is demonstrated that they are represented by the compounds with weakly basic functional groups and by strong bases with the developed aliphatic substitution. Weakly basic compounds of petroleum under investigation contain cyclic amides like pyridones, their hydrogenated analogs, quinoline-carboxylic acids and their esters. Cyclic amides are prevailing in petroleum. Among strong bases that accompany the compounds with weakly basic functional groups, we identified the derivatives of pyridine, quinoline, benzo- and dibenzoquinoline, more condensed polycycloaromatic compounds, thiazol and thiophenoquinoline. Nitrogen-containing strong bases are predominant. With increasing age of Meso-jurassic deposits, the fraction of lactams and strong bases with the total formula C_nH_2nzN increase in the low-molecular nitrogen-containing organic compounds of petroleum.

The conditions of indirect destructive oxidation of phenol by hydrogen peroxide generated electrochemically from oxygen in gas diffusion electrode in alkaline medium in an electrolyzer without cation-exchange membrane are considered. The dependence of phenol oxidation rate and efficiency on current density, concentration and composition of electrolyte is investigated. The major routes of the activation of phenol oxidation and conditions for utilization of organic components from aqueous solutions are determined.

New efficient systems are considered for dissolving of sulphur, including its deposits in industrial communications. New ways for recovery of industrial wastes of sulphur are suggested to yield multinomenclature sulphur-organic compounds with the totality of useful properties following the unified technology.

The effect of the concentration of hydrochloric acid and exposure time on the yield of anthocyanidin dyes obtained from larch and fir bark is investigated by means of photometry. Total mass fraction of anthocyanidin compounds and the fraction of these compounds present in bark in the bound state are determined. Kinetic parameters of the process of obtaining anthocyanidin chlorides from larch and fir bark are determined.

Physico-chemical parameters of the synthesis of carbonized sorbents based on plant raw material are investigated along with the properties of these sorbents. The data of IR Fourier, ESR spectroscopy and electron microscopy are reported. It is stated that carbonized sorbents possess high specific surface and porosity. Carboxylic, carbonyl, hydroxyl groups are detected on the surface of the synthesized sorbents. It is assumed that high sorption ability with respect to Co, Ni, Pb, Cd, Cu ions is connected with the formation of chelate complexes.

The accumulation of chemisorption moisture is found on long storage of technical fluorocarbon materials (FCM) and in the course of slow hydrolysis of CF bonds to form fluoric hydrogen. The features of processes of thermal decomposition of FCMs in vacuum and inert media are studied at 250-700

The application of self-propagating high-temperature synthesis (SHS) and mechanically stimulated self-propagating reactions (MSR) in the processes involved in the processing of geological materials is described. The outlooks of MSR are connected with the possibility to perform several processes simultaneously in a mechanochemical reactor: grinding and activation of the initial and final products, and the combustion of the thermite mixture of solids. Another rapidly developing direction is that connected with the use of geological materials (minerals, ores, concentrates and technogenic waste products) as one of the components of a thermite mixture, both for the treatment of mineral raw by means of SHS or MSR resulting in semi-products (metals and alloys, ceramics and glasses) and for express analysis of natural samples for ecological purposes. Some results of the investigations are considered.

Layer-pillar pore structured samples of Fe-montmorillonite (Fe-MM) have been obtained through modifying of bentonite by mono- and binuclear iron (III) hydroxocomplexes. The influence of conditions of synthesis and thermal treatment on samples properties has been studied. Texture characteristics obtained through N₂ adsorption measurement at 77 K and X-ray phase analysis results bear witness to formation of great number of mesopores and large interparticle lacunas generated both at the expense of random arrangement of short layer-pillar pore structured regions, and through sintering of clay particles on calcining. Adsorption properties of Fe-MM are determined from extinction of phenols and dyes aqueous solutions. Form of isotherms (S-type for phenol, L-type for resorcin and hydroquinone) allows to argue that phenols adsorption takes place mainly at the surface of Fe-MM and is due to dispersion forces action. Methylene blue cationic dye is adsorbed both on the Fe-MM surface and in the interlayer space by use of ion-exchange centers remaining active, as well as micropores produced from pillarization. Since the sorbent surface is appreciably dehydroxilated and contains small quantity of active groups capable of holding large associates of anionic dyes, the adsorption of last mentioned occurs largely in secondary mesopores produced on calcining of Fe-MM samples.