Physico-chemical study of heterogeneous equilibria in salt-aqueous systems of inorganic compounds of uranium(VI)

Abstract

The report presents results obtained in systematic investigation of the physico-chemical state of heterogeneous equilibrium systems of "aqueous solution -precipitate" in the case of the crystalline mineral-like uranium (VI) compounds with the general formula M k (AnUO 2 ) k ⋅nH 2 O, where positions denoted as "An" are occupied by VO 4 3-, PO 4 3-, AsO 4 3-, HSiO 4 3-, or BO 3 3-anions, and M k are alkaline, alkaline earth, and the 3d-transition elements. Chemical stabilities and solubilities of uraniumvanadates, uraniumphosphates, uraniumarsenates, uraniumsilicates, and uraniumborates have been experimentally determined. Detailed quantitative description of the physico-chemical processes and reactions involved in heterogeneous equilibrium in aqueous solutions of the salts by means of equilibrium thermodynamics is presented. The description gives us the possibility to predict the behaviour of the uranium compounds under different conditions and to calculate Gibbs functions of the formation of the compounds studied.