The cation exchange properties of alkali and alkaline earth metal cations at room temperature were investigated on an ultrafine, highly charged Na-4-mica (with the ideal mica composition Na 4Mg 6Al 4Si 4O 20F 4·xH 2O). Ultrafine mica crystallites of 200 nm in size led to faster Sr 2+ uptake kinetics in comparison to larger mica crystallites. The alkali metal ion (K +, Cs +, and Li +) exchange uptake was rapid, and complete exchange occurred within 30 min. For the alkaline earth metal ions Ba 2+, Ca 2+, and Mg 2+, however, the exchange uptake required lengthy periods from 3 days to 4 weeks to be completed, similar to its Sr uptake, as previously reported. Kinetic models of the modified Freundlich and parabolic diffusion were examined for the experimental data on the Ba 2+, Ca 2+, and Mg 2+ uptakes. The modified Freundlich model described well the Ba 2+ ion uptake kinetics as well as that for the Sr 2+ ion, while for the Ca 2+ and Mg 2+ ions the parabolic diffusion model showed better fitting. The alkali and alkaline earth ion exchange isotherms were also determined in comparison to the Sr 2+ exchange isotherm. The thermodynamic equilibria for these cations were compared by using Kielland plots evaluated from the isotherms.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Surfaces and Interfaces