Stellerite dissolution kinetics under hyperalkaline conditions

Dissolution kinetics of stellerite (Ca (Al2Si7O18).7H2O) were investigated in pH-buffered hyperalkaline at pH range of 8 - 12 in batch reactors at temperatures of 4, 25, 40 and 6 0C. Dissolution rates were determined using silicon concentration of the reacting fluid and the rates of dissolution increased with increasing temperature and pH. The dissolution rates ranged from 1.76 x 10-15 mol cm-2 s-1 at pH 8 to 25 0C to 1.72x 10-9 mol cm-2s-1 at pH 12 and 60 0C. The rate of dissolution (R) was pH dependent and the rate law could be described by the relationship, R k(AOH-)n , where A is activity of hydroxyl ion activity, k is rate constant and n is reaction order. The values of n were 0.24 at 25 0C, 0.34 at 40 0C and 0.43 at 60 0C. The activation energy of dissolution rate determined by Arrhenius plot was 58.55 kJ/mol at pH 9 and 66.60 kJ/mol at pH 12. (au)