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.     

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.     

State of difficultly soluble uranosilicates MIHSiUO6 ? nH2O (M + = Li+, Na+, K+, Rb+, Cs+, NH4+) in saturated aqueous solutions

The solubility of uranosilicates M^IHSiUO₆ nH₂O (M^I = Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, NH ₄ ⁺ ) in aqueous solutions at 25°C was studied experimentally. The equilibrium constants of reactions that occur at dissolution of uranosilicates in acidic and neutral solutions were calculated. The composition of the equilibrium solutions was studied. The standard Gibbs energies of formation of the compounds were calculated from the solubility data. The behavior of the uranosilicates under various conditions was predicted on the basis of the previously suggested quantitative physicochemical model of the state of the heterogeneous system crystalline uranosilicate-aqueous solution.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 418–422.Original Russian Text Copyright © 2004 by Chernorukov, Nipruk, Knyazev, Pegeeva.     

Solubility of Uranovanadates AII(VUO6)2·nH2O (AII = Mg,Ca, Sr,Ba, Co,Ni, Cu,Pb) in Water and Aqueous Solutions

Solubility of uranovanadates A^II(VUO₆)₂·nH₂O (A^II = Mg, Ca, Sr, Ba, Co, Ni, Cu, Pb) in water and acid aqueous solutions under various conditions was studied. Based on these data, the standard Gibbs energies of formation of the uranovanadates were calculated, which would allow analysis of their state under conditions that were not studied experimentally.     

Synthesis and characterization of the M<Superscript>II</Superscript>U<Subscript>3</Subscript>O<Subscript>10</Subscript> · 6H<Subscript>2</Subscript>O (M<Superscript>II</Superscript> = Ni,Zn) triuranates

We have developed a process for the synthesis of Ni(II) and Zn(II) triuranates with the general formula M^IIU₃O₁₀ · 6H₂O through reaction of schoepite, UO₃ · 2.25H₂O, with aqueous solutions of nickel and zinc nitrates under hydrothermal conditions. Using chemical analysis, X-ray diffraction, IR spectroscopy, and thermal analysis, we have determined the composition and structure of the triuranates and investigated their dehydration and thermal decomposition.     

Synthesis and study of uranyl phosphates (UO<Subscript>2</Subscript>)<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>·<Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O

Uranyl phosphate (UO₂)₃(PO₄)₂·8H₂O was synthezied. Its dehydration was studied by X-ray diffraction, IR spectroscopy, and thermal and chemical analysis. The dehydration products were isolated and characterized by X-ray diffraction and IR spectroscopy. Their structural features were determined.     

Heterogeneous Equilibria in Saturated Aqueous Solutions of Uranophane-Kasolite Group Uranosilicates

The composition of mineral-like uranosilicates of uranophane-kasolite group in saturated aqueous solutions at 25°C was studied, and a quantitative physicochemical model of the heterogeneous system crystalline uranosilicate-aqueous solution was developed. The equilibrium constants of dissolution and standard Gibbs energies of formation of compounds studied were calculated. The model developed was used to predict uranosilicate dissolution in a wide range of acidities of the aqueous phase under standard conditions.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 328–333.Original Russian Text Copyright © 2005 by Chernorukov, Nipruk, Knyazev, Strakhova.     

Solubility and Thermodynamic Properties of Alkali Metal Unanoborates

The solubility of uranoborates M^IBUO₅·nH₂O (M^I = Li, Na, K, Rb, Cs) in aqueous HCl solutions was measured at 25°C, and the standard thermodynamic functions of the compounds were calculated.