Experimental and theoretical investigation of the kinetics of the sorption of water vapour by silica gel

Abstract

The kinetics and mechanism of the sorption reaction between water vapour and silica gel have been investigated in the pressure range 1–50 Torr using thermogravimetry under controlled temperature and water-vapour pressure. Measurements at equilibrium were carried out in order to determine the pertinent equilibrium parameters and the extent of hysteresis. The influence of particle radius and temperature on the kinetics in the whole of the pressure range investigated are well described by theoretical curves fitted to experimental data by taking into account simultaneous mass- and heat-transfer. Calculations yield a diffusivity of 8 × 10^–10 m² s^–1. The sorption kinetics in the pressure range 15–40 Torr are shown to be controlled by heat transfer.