Rate-controlling step in the hydrothermal synthesis of zeolites from sardinian perlite

The poor discriminative power of a variety of integrated rate equations is shown to be in contrast with the highly selective attribution which is possible on the basis of adimensional reaction rate curves. Accordingly, the rate of the hydrothermal conversion of Sardinian perlite to zeolites in alkaline medium has been found to obey apparent second-order kinetics implying a reaction between the liquid phase and the solid component, and satisfying the expression ? (1 - ?) = Kt. Particle sizes influence reaction rates through variation in the apparent kinetic rate constant K; experimental data can be interpreted according to a rate composed of an initial term ruled by mass transport sequentially followed by diffusion within the layers. © 1985.