Home – Home – Jornals – Chemistry for Sustainable Development 2006 number 4

Methods of synthesis of fluorine-containing dialkyl and fatty-aromatic ethers involving the reactions of aliphatic alcohols and phenols, including aromatic ones, with perfluoroolefins are considered. To obtain various fluorine-containing polyethers, polyhydric alcohols were used in reactions with perfluorinated tri-, tetrafluoroethylene and hexafluoropropylene. Some properties of fluorine-containing ethers are discussed; examples are their application are presented.

Results of the galvanochemical oxidation (GCO) of 2-chlorophenol (2-CP) in aqueous solutions at pHin 3 are discussed. A more substantial decrease in the concentration of 2-CP (C2-CP = 1.55 10

Ultradispersed oxyhydroxides of aluminium have been obtained upon the interaction of electroexplosive nanodispersed aluminium with water at 55 oC. Initial samples were subjected to ageing under the alkaline condition (pH 10) at 20 and 50 oC. It has been demonstrated that the content of structural water in resultants of the reaction increases during the course of ageing; the specific surface and the limiting adsorption volume decrease. An increase in the intensity of reflexes of bayerite and a decrease in the intensity of pseudoboehmite lines with time have been noted. The sorption of saturated benzene vapour at 20 oC drops during the ageing of samples. The observed processes occur more intensively at 50 oC. An inference about the transformation pseudoboehmite

Processes that occur during mechanochemical activation of the mixtures of diopside with calcite and amorphous silicon dioxide with calcite in a centrifugal planetary mill are investigated. According to the data of IR spectroscopy and XPA, with calcite content up to ~10 mass %, mechanochemical interaction of the mixture components results in the formation of a substance which is similar to carbonate-containing silicate glass. During mechanochemical activation of a mixture of amorphous silicon dioxide with calcite (at a molar ratio of 1 : 1) the degree of interaction between the components decreases substantially, the major part of input mechanical energy is consumed for the achievement of mechanochemical equilibrium between calcite and aragonite. Investigated processes were compared with the previously discovered mechanically induced absorption of carbon dioxide by calcium- and magnesium-containing silicates. The data on phase formation under heating of mechanochemically activated mixtures of silica with calcite are reported.

Reasons for phase change in zirconia upon its intensive mechanical treatment in mills have been discussed. It has been demonstrated that when used steel balls and barrels, oxidation of wear products and their mechanochemical interaction with ZrO2 occurs along with a decrease in the size of particles and crystallites. It has been found that implantation of cations of an extrinsic metal in the crystal lattice is favourable to the stabilization of a more symmetric modification and to an increase in the critical size of crystallites, above which the monoclinic modification becomes stable. A conclusion has been made that an increase in the contribution of superficial energy to the Gibbs energy plays dominating part in the phase change on initial stages of mechanical treatment, while the thermodynamic stability in the further process is controlled preferentially by a stabilising impact of impurity cations. Under conditions that prevent from pollution of ZrO2 by metal, a dynamic equilibrium is established between the forward change to tetragonal modification and the reverse, to monoclinic.

The concentration dependence of the first moments M1 of fluorescence spectra of the fractions of humic acids (HA) differing in molecular masses in aqueous solutions within the concentration range 0.5

The mechanism of processes involved in the interaction of humic acids with heavy metal ions, as well as the features of structure and properties of metal humic complexes (MHC) are investigated with the help of EPR spectroscopy and TGA. The topography of distribution of functional groups on the surface of the powders of humic acids and MHC is investigated by means of adsorption of acid-base indicators. The stability of MHC in aqueous medium and the mobility of heavy metals are studied with the help of HCl leaching method.

The reactions of FeCl2, CoCl2, NiCl2 with MBH4 (M = Li, K, Na) proceeding during mechanical activation of the mixtures of crystal substances in a vacuum vibratory mill were investigated. It was established that the reactions are accompanied by the formation of diborane(6), or B2H6, the yield of which depends on the nature of initial reagents, molar ratio of reagents, time of mechanical activation and the mass of ball load. Under the optimal conditions, the yield of B2H6 is 30 to 50 %.

Natural experiment with underground draining of high-sulphide waste products from Karabash Copper-Smelting Combine (Chelyabinsk Region) by natural neutral water has been performed. An oxyntic potential and a quantity of Cu, Zn, and Fe that passed into solution has been determined; a change in fractional distribution of chemical forms of these elements in the solution and in saturation indexes of mineral phases with an increase in the water/rock ratio (W/R) during the course of the experiment has been calculated. It has been demonstrated that interaction of natural neutral water with the material of waste products yields acids and results in that more than 50 % Cu and Zn, and about 30 % Fe passes into solution to yield the ratio W/R = 400 : 1. It has been observed that at low W/R ratios in acidic medium, copper and zinc exist in the form of sulphate neutral complexes and activated ions, and zinc additionally forms an anionic sulphate complex. As washing of acid proceeds, the fraction of sulphate complexes decreases; the metals remain preferentially in the form of aqua ions. Iron that exists in the solution predominantly in a sulphate complex during the beginning of the experiment then changes to a hydroxide form. Processes of dissolution and deposition of mineral phases actively proceed during the experiment. Ferrihydrite Fe(OH)3 and goethite FeOOH that are produced by the end of the experiment facilitate sorption and coprecipitation of copper and zinc. Formation of a secondary sulphate, jarosite KFe3(SO4)2(OH)6, during the experiment is confirmed by data of X-ray crystal analysis.

Chemical and particle-size composition of slimes from accumulator factory has been investigated. It has been demonstrated that basic part of lead therein is presented by carbonate and oxidic compounds, and in view of fine dispersity of the products, conventional methods of producing lead from slimes are unsuitable. Laboratory tests of two variations of a cementation procedure to reclaim lead from sewage slimes of accumulator factory have been performed. They included the one with intermediate obtaining pure lead sulphate and with direct cementation of lead from a sulphate product. It has been demonstrated that both of variations provide practically complete regeneration of lead to yield marketable products. Advantages and limitations of both variations have been discussed.

The capability of YBa2Cu3Od for an intensive exchange with oxygen of a gas phase even at ambient temperature (ta) that has been detected previously has been studied with diversified physical methods. An X-ray photoelectron spectroscopy method has been applied to demonstrate that a degree of ionicity of cation-oxygen bonds increases during oxidation under the ta conditions. Along with this phenomenon, oxygen appears in a state that is close to chemically unbonded. This correlates with evidence on spontaneous electric polarization that emerges in yttrium-baric cuprate under the test conditions. The obtained result has been explained in the context of YBa2Cu3Od model as of a virtual ferroelectric, the critical temperature of which in certain conditions can grow up to high positive values. In so doing, modification of chemical state of [BaO2] structural group occurs from formal peroxide to formal oxide with strengthening of a certain Ba

An effect of conditions of hyperfine grinding on the size of crystallites and on the aggregation degree of received a-Al2O3 nanopowders has been examined. It has been demonstrated that the average size of crystallites of a mechanically grinded powder is a function of relative humidity in the barrels of a planetary mill with a pronounced minimum (200