INFLUENCE OF WATER-VAPOR ON THE THERMAL DEHYDRATION OF LI2SO4.H2O

Kinetics of thermal dehydration of lithium sulfate monohydrate have been studied by using TG and DSC for Li2SO4.H2O samples with different characteristics, i.e., powdered sample, pressed pellet, plate crystal and cubic crystal. The TG measurements in N2 saturated with water and dry N2 showed that the dehydration of Li2SO4.H2O was affected by the presence of water, particularly for the powdered sample at the early stage of dehydration. This phenomenon is explained by consideration of H2O diffusion. The apparent activation energies were calculated based on the Ozawa method from TG data obtained at different heating rates. No significant difference was found in the apparent activation energy due to the presence of external water vapor. DSC measurements on the dehydration of all four samples were also performed, and the apparent activation energies, obtained from analyzing partial areas by the Ozawa method, are comparable to those obtained from TG.