The Al+Na and Al+K substituted tobermorites have been hydrothermally synthesized at 175°C under saturated steam pressure and their ion-exchange characteristics for K+ and Cs+ ions have been investigated from kinetics, equilibria and thermodynamics points of view. The initial exchange of Na+ in Al+Na substituted tobermorite with K+ and Cs+ ions was found to progress by diffusion of K+ and Cs+ ions. The activation energy for the Na → K exchange was evaluated to be smaller than that for Na → Cs exchange. The standard free energy changes for the cation exchange reactions were estimated at two total molarities of 1.0 × 10-3 and 3.0 × 10-3 mol/l which were found to be negative and the affinity of univalent cations for both Al+Na and Al+K substituted tobermorites at 25°C was found to follow the order: Na+ < K+ < Cs+. These basic studies suggest that the substituted tobermorites are selective for certain ions such as Cs+ and therefore they can be used in cation exchange separations.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering