Solubility of uranoarsenates MAsUO6·nH2O in water and aqueous HClO4 (M = H+, Li+, Na+, K+, Rb+, Cs+, NH 4 + )

The solubility of poorly soluble uranoarsenates MAsUO₆·H₂O in water and aqueous HClO₄ was determined. The solubility products and Gibbs energies of formation of these compounds were evaluated from the experimental data using the principles of equilibrium thermodynamics. The state of uranoarsenates in aqueous solutions in the range not studied experimentally was estimated.     

Liquid–phase extraction treatment of wastewater of paint and varnish production facilities in the extractor with mixer

Liquid–phase extraction technology providing the maximum wastewater purification from such electrolyte composition components as butylglycol, phenylisopropanol, ascetic acid, and acetylacetone has been developed. A mathematical model of the process is proposed that takes into account the hydrodynamics of liquid flow and mass transfer in phases for each component. The differential cell model was used to determine the process parameters and calculate the basic dimensions of extractor. In addition, a three-stage process flowsheet with minimum extractant consumption was also presented.     

Thermodynamics of Rubidium Uranoniobate

The standard enthalpies of formartion of crystalline -RbNbUO₆, -RbNbUO₆, and RbNbUO₆·H₂O at 298.15 K were determined. The temperature dependence of the heat capacity of -RbNbUO₆, RbNbUO₆·H₂O, and -RbNbUO₆ was studied in the range 60-300 K. The thermodynamic functions and equilibrium constants of the reactions involved in synthesis of rubidium uranoniobates at various temperatures were calculated.     

On the role of heterogeneous and homogeneous processes in oxidative dehydrogenation of C3-C4 alkanes

The effects of reactor arrangement, catalyst particle size and void volume on the oxidative dehydrogenation (ODH) of propane and iso-butane are studied. In an empty quartz reactor, a high conversion of alkane (up to 36% with a 40% ODH selectivity) can be achieved. Packing of the reactor with different solids (quartz, γ-Al₂O₃, complex V-containing oxide catalysts) leads to a drastic change in reaction parameters, which is strongly dependent on the chemical nature of solids and their particle size. The analysis of observed phenomena indicates that: (a) the termination of gas-phase chain reaction takes place on the surface of any solid material; (b) certain solids behave as active generators of free radicals, thus initiating the new reaction pathway which develops both in the gas-phase and on the solid surface.     

Risk management in the byproduct shops at coke plants

Risk factors in the byproduct-trapping shop are identified. The need for quantitative and quantitative risk assessment is established. A method of estimating the probability of an accident in trapping-shop systems with different types of backup is developed. Calculations by the proposed method are presented. Recommendations for more stable shop operation are elaborated.     

Physical Chemistry of the Compounds AI I(BVUO6)2·nH2O (AI I = Mn, Ni, Co, Zn, Cd; BV = P, As)

The ion exchange between an aqueous solution of a bivalent metal chloride (A^{I I} = Mn, Ni, Co, Zn, Cd) and crystalline phases HB^VUO₆·4H₂O (B^V = P, As) was studied. The exchange constants and standard Gibbs energies of formation of the crystalline compounds A^{I I}(B^VUO₆)₂·nH₂O were calculated.     

Modification of aluminum alloys in a solar furnace

The processes of the modification of the D16 aluminum alloy at the focus of a solar furnace are studied experimentally. The surface heat treatment at the solar furnace focus was performed without melting the surface. The experiment showed that the grain size decreases from 10 to 3 microns with the exposure of the specimens at the focal spot for 35 seconds, and small regions with the grain size 0.3 micron appear. Grains of dimension 0.3 micron are observed with the exposure of the specimen at the solar furnace focus for 40 seconds, and the microhardness is H _v = 74.8 kg/mm². The repeat measurement of the microhardness after 40 days corresponds to H _v = 104.8 kg/mm², i.e., the microhardness after modification in the solar furnace and natural aging increases by 16%.     

Heat of solution of asphaltene-resin-wax deposits in straight-run petroleum fractions

The process of dissolution of asphaltene-resin-wax deposits was investigated from the standpoint of the heat of mixing. It was shown that, of the main constituent groups of asphaltene-resin-wax deposits, not only paraffin waxes and resins but also asphaltenes can form true solutions. The components isolated from the paraffin base showed the best solubility in kerosene and diesel fractions of crude oil.