Metastability in drowning-out crystallisation: precipitation of highly soluble sulphates

Abstract

In this paper we derive equations for evaluating the supersaturation, b, and the supersaturation rate, Rb, for the drowning-out crystallisation under isothermal conditions and assuming a constant rate of the addition of the co-solvent. Such equations are applied to the drowning-out crystallisation of single and double sulphates in theM2SO4±LiSO4±H2O (M=Na, Rb) ternary systems. A linear relationship between lnRb and ln bmax, similar to that reported for the crystallisation by cooling, evaporation and chemical reaction, has been found.