Effect of aqueous aluminium and silica concentrations on smectite dissolution kinetics at hyperalkaline conditions

Chino, Daisuke*; Sato, Tsutomu*; Otani, Yusuke*; Nakabayashi, Ryo*; Oda, Chie  ; Yoneda, Tetsuro*

Steady-state dissolution rates of smectite were determined as function of aqueous Al and Si concentrations using a stirred-flow-through reactor at 70 degrees in 0.3M-NaOH solution to obtain the reliable dissolution rates of smectite at hyperalkaline condition and to formulate the effect of deviation from equilibrium on smectite dissolution rate. The dissolution rates were calculated based from the dissolved Si or Al concentrations of the output solutions or from ex situ AFM observations. Results of the flow-through dissolution experiments and ex situ AFM observations suggest that the dissolved Si and Al concentrations in the solutions appear to be retarding the dissolution rate of smectite. If we assume the decrease is attributed by the effect of deviation from equilibrium on dissolution rate, the dissolution rate of smectite can be expressed in a non-linear function of the Gibbs free energy. This non-liner relationship is nearly same as that obtained by Cama, et al. (2000).