RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

Interactions between U(VI) and calcite appear to be limited to adsorption reactions at the surface. U(VI) is concentrated at the calcite solution-interface at slightly alkaline pH.

However, its mobility is dependent on solution pH. The interactions at the mineral-solution interface may be modeled thermodynamically in terms of the concentration of U(VI) adsorbed at the carbonate surface and the activity of the calcite component:

UO₂²⁺ + CaCO₃(s) = >UO₂CO₃ + Ca²⁺

where the > symbol denotes a surface species.

The equilibrium constant, K_{U(VI),calcite} = 10^5.12 and is independent of solution pH.