Synthesis and Study of Alkaline-Earth Metal Uranoborates,AI I(BUO5)2·nH2O

Previously unknown compounds A^{I I}(BUO₅)₂·nH₂O (A^{I I} = Mg, Ca, Sr, Ba; n = 0-7) were synthesized. Their structure and thermal decomposition were studied by X-ray diffraction, IR spectroscopy, and thermal analysis.     

Synthesis,Structure, and Physicochemical Properties of AI 4[UO2(CO3)3]·nH2O (AI = Li,Na, K,NH4)

Procedures for the synthesis of Li₄[UO₂(CO₃)₃]·1.5H₂O, Na₄[UO₂(CO₃)₃], K₄[UO₂(CO₃)₃], (NH₄)₄[UO₂(CO₃)₃], and K₃Na[UO₂(CO₃)₃] were optimized. The structures of these compounds and their thermolysis were studied by X-ray diffraction, precision IR spectroscopy, and thermal analysis. The standard enthalpies of formation of these compounds at 298.15 K were determined by reaction calorimetry.     

Synthesis and Study of Magnesium and Calcium Uranogermanates

Previously unknown alkaline-earth metal uranogermanates of the general formula MII[HGeUO₆]₂·nH₂O (MII = Mg, Ca) were prepared in the form of higher and intermediate hydrates and anhydrous compounds. The compounds were studied by X-ray diffraction, IR spectroscopy, and thermal analysis.     

Synthesis, Structure, and Physicochemical Characteristics of Rutherfordite and Tetrasodium Uranyl Tricarbonate

The optimum procedures for synthesis of UO₂CO₃ and Na₄[UO₂(CO₃)₃] were developed. The structures of these compounds and their thermal decomposition were studied by X-ray diffraction, precision IR spectroscopy, and thermography. The standard enthalpy of formation of crystalline Na₄[UO₂(CO₃)₃] at 298.16 K was determined to be -4010.0±8.0 kJ mol^{- 1}.     

Thermodynamics of Ba2Sm2/3UO6

The standard enthalpy of formation of crystalline Ba₂Sm_2/3UO₆ at 298.15 K, ?3040.0±7.5 kJ mol^?1, was determined by reaction calorimetry. The heat capacity of the compound in the range 80–300 K was measured by adiabatic vacuum calorimetry, and its thermodynamic functions were calculated. Its standard entropy of formation at 298.15 K is ?592.5±1.0 J mol^?1 K^?1, and the Gibbs energy of formation at 298.15 K, ?2863.5±8.0 kJ mol^?1. The standard thermodynamic functions of the reactions of the Ba₂Sm_2/3UO₆ synthesis were calculated and discussed.     

Thermodynamics of lutetium uranosilicate

The standard enthalpy of formation of crystalline Lu(HSiUO₆)₃ · 10H₂O at 298.15 K, ?10668.0±16.0 kJ mol^?1, and the standard enthalpy of its dehydration were determined by reaction calorimetry. The heat capacity of this compound in the range 80–300 K was measured by adiabatic vacuum calorimetry, and its thermodynamic functions were calculated. The standard entropy of formation at 298.15 K is ?3812.9±1.2 J mol^?1 K^?1, and the standard Gibbs energy of formation at 298.15 K, ?9531.0±16.5 kJ mol^?1. The standard thermodynamic functions of the reactions of the synthesis of lutetium uranosilicate were calculated and discussed.     

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.     

Synthesis and Physicochemical Study of Compounds in UO3-AkOk/(Ak = B, Si, Ge)-HO Systems

A synthetic analog of soddyite mineral, (UO₂)₂SiO₄·2H₂O, was prepared by hydrolyzing ammonium uranosilicate under hydrothermal conditions. The germanium-containing structural analog of soddyite, (UO₂)₂GeO₄·2H₂O, was synthesized by precipitation from solution. The compound UO₂(BO₂)₂ was prepared by reaction with molten boron oxide. The structures and properties of the compounds prepared were studied by X-ray diffraction analysis, IR spectroscopy, and thermography. The enthalpies of formation of the compounds were determined by adiabatic reaction calorimetry.     

State of uranyl phosphates and arsenates in aqueous solutions

The state of uranyl phosphates and arsenates (UO₂)₃(PO₄)₂·nH₂O and (UO₂)₃(AsO₄)₂·nH₂O in aqueous solutions in the interval of pH 1–14 was studied by X-ray diffraction, IR spectroscopy, thermography, and chemical analysis. The composition and structure of the initial solid phases vary depending on the solution acidity. The equilibrium constants of the reactions occurring in the heterogeneous systems (UO₂)₃(B^VO₄)₂·nH₂O (B^V = P, As)-aqueous solution were calculated. The speciation diagrams of the solid phases and equilibrium solutions were plotted.