Study of the state of uranoarsenates MII(AsUO6)2·nH2O(MII = Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+) in aqueous solutions

State of uranoarsenates MII(AsUO6)2·nH2O (MII = Mn, Co, Ni, Cu, Zn, Cd, Pb) in aqueous solutions in a wide range of acidity (pH 0–14) was studied. Acid-base boundaries of existence of the compounds were estimated, products of conversion were identified, and solubility of MII(AsUO6)2·nH2O was determined. On the basis of the obtained data the solubility products and Gibbs functions of formation of uranoarsenates, and the solubility curves were calculated, phase diagrams of uranium(VI) and arsenic(V) in solutions and in equilibrium solid phases were constructed with the use of the equilibrium thermodynamics technique.