Crystallization thermodynamic properties and nucleation kinetics of Sr(OH)2·8H2O in an Sr(OH)2·8H2O-H2O system

Abstract

There have been few reports in literature on the crystallization thermodynamic properties and nucleation kinetics of strontium hydroxide octahydrate despite their great importance to the reactor design and the regulation of crystal properties. In this work, the crystallization thermodynamic properties of Sr(OH)2·8H2O in pure water were investigated using a dynamic temperature-controlled process and an equilibrium process. The metastable zone width (MSZW) was examined under different crystallization process conditions including stirrer speed, solution concentration, cooling rate, and different strategies in adding seed crystals. In addition, models for the nucleation kinetics and MSZW were successfully constructed based on the classical nucleation model. Based on the data provided, it can be concluded that the dissolution of Sr(OH)2·8H2O in pure water is an entropy-driven endothermic process and its MSZW was gradually narrowed with an increase in stirring speed and concentration and with a decrease in cooling rate. Additionally, adding seeds was an effective strategy to narrow the metastable zone. Therefore, this endeavor provided a rational principle for subsequential investigations of Sr(OH)2·8H2O and other compounds.