Studies on metal carbonate equilibria. Part 10. A solubility study of the complex formation in the uranium(VI)–water–carbon dioxide (g) system at 25 °C

摘要: The complex formation in the system UVI–H2O–CO2(g) was studied by measuring solubility of UO2(CO3)(s) as a function CO2 pressure and hydrogen-ion concentration. measurements were made at 25 °C, using two different ionic media, 0.5 3 mol dm–3 NaClO4, respectively. equilibrium constants for following reactions determined. Interaction UO2(CO3)(s)⇌ UO22++ CO32– Ks,o UO22++tCO32–⇌ UO2(CO3)t, t= 1–3 βt,1 3UO22++ 6CO32–⇄[(UO2)3(CO3)6]6–β6,3 coefficients Iµ(i,j) various uranium species with ClO4–(or Na+) determined Bronsted, Guggenheim, Scatchard specific ion-interaction theory. By these data from literature, we propose set ‘best’ estimates constants, referred to pure water reference state: log Ks,o=–14.4 ± 0.1, β1,1= 9.5 0.2, β2,1= 16.6 β3,1= 21.3 β6,3= 53.4 0.8.