Kinetic study of LI₂SO₄·H₂O dehydration using microscopy and modeling

A phenomena-based method is presented to study the kinetics of the dehydration reaction of Li₂SO₄·H₂O single crystals. The reaction proceeds by nucleation and growth processes, which are recorded photographically using a camera system. Based on a series of pictures of surface observations under isothermal conditions, an areic nucleation rate and growth rate were estimated. Since only surface information was obtained so far, an experimental study about the speed of growth into the crystal was carried out to quantify the growth rate in-depth. Together with the surface information, a nucleation and growth model was developed and employed to predict the reaction kinetics. The fractional conversion of the dehydration reaction was calculated and compared with experimental results from TGA (thermogravimetric analysis) measurements. A satisfactory prediction was achieved as a function of sample medium and experimental environment.