Stellerite Dissolution Kinetics Under Hyperalkaline Conditions

Abstract

Dissolution kinetics of stellerite (Ca (Al2Si7O18).7H2O) were investigated in pH-buffered hyperalkaline solutions at pH range of 8 - 12 in batch reactors at temperatures of 4, 25, 40 and 60 oC. Dissolution rates were determined using silicon concentration of the reacting fluid and the rates of dissolution increased with increasing temperatu-re and pH. The dissolution rates ranged from 1.76 x 10^-15 mol cm^-2 s^-1 at pH 8 to 25 oC to 1.72x 10^-9 mol cm^-2 s^-1 at pH 12 and 60 oC. The rate of dissolution (R) was pH dependent and the rate law could be described by the relationship, R=k(A_OH-)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 oC, 0.34 at 40 oC and 0.43 at 60 oC. The activation energy of the dissolution rate determined by Arrhenius plot was 58.55 kJ/mol at pH 9 and 66.60 kJ/mol at pH 12.

Journal of Applied Science and Technology Vol. 12 (1&2) 2007: pp. 25-30