Thermodynamic analysis of dehydration of K2CO3·1.5H2O

Abstract

This work studied the reversible dehydration of potassium carbonate sesquihydrate (K2CO3·1.5H2O). The study is based on isobaric and isothermal thermogravimetric measurements conducted at a broad range of vapour pressures and temperatures. By controlling both parameters, we examined the influence of both constraints on the reaction kinetics at a wide extent of supersaturations. We have evaluated our experimental findings by employing two thermodynamic theories, classical nucleation theory and transition state theory. By combining both approaches, we were able to establish that: (1) At low supersaturations in a region close to equilibrium, dehydration is limited by nucleation and growth of the anhydrous phase (2) At high supersaturations, dehydration reaches maximum rate and is controlled by the reaction speed. Furthermore, we show that the dehydration of K2CO3·1.5H2O is very sensitive to pressure-temperature conditions and that it does not possess universal activation energy.