A turbidity titration procedure for the nucleation mechanism determination of sodium sulfate decahydrate (Glauber salt) in unseeded aqueous solution

Abstract

As a noteworthy salt hydrate, sodium sulfate decahydrate or Glauber salt can be used as a phase change thermal energy storage material. Kinetic parameters of sodium sulfate decahydrate salt solution are evaluated experimentally. Instead of the traditional polythermal and isothermal methods, a novel constant temperature experimental method (based on the turbidity titration) was adopted to experimentally illustrate the induction time and metastable zone width, in unseeded batch crystallization for sodium sulfate decahydrate salt solution at different temperatures (7, 9, 10, 13, 16, 19, 22 °C) and supersaturation ratio (1.01–1.43). We determined crystallization thermodynamics parameters, solubility, and supersolubility, of sodium sulfate decahydrate salt solution under atmospheric pressure and at different temperatures. The solubility data could be well fitted by the solubility carve of sodium sulfate decahydrate in the phase diagram of sodium sulfate. Statistical analysis shows that there was consistency in the result data of solubility. Two models, classical nucleation theory (primary homogeneous) and secondary nucleation, were employed to analyze the experimental data. The secondary nucleation model helped determine the order of nucleation and nucleation kinetic constants.