Mössbauer Study of the Effect of Cation Substitutions on the Magnetic Phase Transitions in BiFe1 – xCrxO3 and (1 – x)BiFeO3–xPbFe0.5Sb0.5O3 Solid Solutions

Crystallography Reports - The concentration dependences of the magnetic phase transition temperature TN, determined based on the changes in Mössbauer spectra, were investigated for a BiFeO3...     

Automatic systems for control of water purification with online monitoring of pollutants at key points of the flow diagram

A system for automatic control of a three-step process of water purification is developed. The system includes the online monitoring of the concentrations of pollutants in water at points of the flow diagram corresponding to the primary, fine, and final treatment steps, and consists of a UV-fluorimeter for determining the concentrations of pollutants, solenoid valves for controlling the flow of water in the treatment installation and a computerized central control unit operating according to a preset algorithm of water treatment control.     

Physicochemical foundations and specificity of the practical application of supercritical water oxidation to the destruction of persistent organic pollutants

The theoretical and practical aspects of application of one of the most promising methods for the destruction of persistent organic pollutants, supercritical water oxidation, are discussed. The current state of research in the field of analysis and prediction of the critical parameters of systems with an arbitrary number of components, the behavior of the components in supercritical water-organic pollutant binary systems, and the specificity of supercritical fluids are considered. Various types of phase diagrams of binary systems are examined, and theoretical foundations for calculating the critical physicochemical parameters of multicomponent systems are presented. By the example of hexachlorocyclohexane (Lindane), one of the most toxic pesticides, calculations of the material and heat balance of the oxidation of pesticides with oxygen and hydrogen peroxide are performed. The calculations can be used in designing technological installations for the destruction of pollutants by the supercritical water oxidation.     

Influence of crystallite-boundary potential barriers on the thermopower and peltier effect in polycrystalline ferroelectric semiconductors

The influence of local charged states at crystallite boundaries on the thermoelectric effects in polycrystalline ferroelectrics is considered. It is shown that the differential thermopower and the Peltier coefficient depend on the height of the crystallite-boundary potential barriers. The possible manifestation of an anomalous behavior of the thermopower in the vicinity of the Curie ferroelectric point is demonstrated.     

Effect of the nature of the metal oxide on selective transformation of methane under unsteady conditions in the absence of oxidant in the gaseous phase

The catalytic transformation of methane into higher hydrocarbons was studied under unsteady conditions on oxides of various metals (Pb, Fe, Nb, Ti, Cd, Mo, Mg, Zn, Zr, Bi, Mn), and also on Sr-, La-, Y-, and Mn-containing oxides of perovskite structure. It is shown that the effectiveness of the catalysts not only depends on their chemical composition, but also is determined to a considerable degree by the specific surface of the oxides. L. V. Pisarzhevskii Institute of Physical Chemistry, Academy of Sciences of Ukraine, 252039 Kiev, Prosp. Nauki, 31, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 91–95, March–April, 1997.     

Influence of the composition of perovskites based on SrMnO<Subscript>3</Subscript> on their catalytic properties in the oxidative coupling of methane

The oxidative coupling of methane (OCM) in a periodic regime over the SrMnO₃ and its derivatives has been investigated. It has been established that partial replacement of the strontium ion by alkali metal ions leads to an increase in both catalytic activity and in selectivity with respect to higher hydrocarbons. Comparison of the results obtained in the present work with those obtained earlier for catalysts based on SrCoO₃ led to the conclusion that the Co-containing catalysts were preferable to the Mn-containing catalysts for carrying out oxidative coupling of methane in a periodic regime.__________Translated from Teoreticheskaya i Éksperimentalnaya Khimiya, Vol. 41, No. 1, pp. 30–34, January–February, 2005.     

Preparative isolation of (+)-beta-eudesmol fromAmyris balsamifera

Summary Optically pure (+)-beta-eudesmol is a possible starting material for the synthesis of several termite defense compounds. A two step procedure for the isolation of gram quantities of (+)-beta-eudesmol from commercially availableAmyris balsamifera oil (syn. West Indian sandalwood oil), containing 8% beta-eudesmol, was developed. Step one consisted of an efficient vacuum distillation of the total oil. Step two was a medium pressure LC separation with an AgNO₃ impregnated silica gel stationary phase. Several other separation procedures failed due to the presence of many closely related sesquiterpene alcohols (75% of the oil).