HYDRATED K2SO4-CENTER-DOT-2MGSO(4) STRUCTURE REVEALED BY TGA DTA AND MAGIC-ANGLE-SPINNING H-1-NMR SPECTROSCOPY/

The hydration of K2SO4 . 2MgSO(4) as a function of water addition was examined by pore-size distribution, thermo-gravimetric analysis/differ ential thermal analysis and nuclear magnetic resonance (NMR) spectrosc opy. Thermal studies indicated that the dehydration reactions occur wi thin three distinct temperature regimes which correspond to different degree of hydrogen bonded water or water in different pore-size enviro nments. Solid NMR studies resolved three different proton peaks at eac h water loading, that represent different chemical environments around water, and also the different range of hydrogen bonding strengths. Th erefore, the different chemical environments associated with pore size around water are key factors influencing the NMR spectra. Both therma l and NMR studies suggested that pore size affects the molecular inter actions between water and water, and water and the substrate. Also X-r ay diffraction studies identified the presence of three phases existin g in the hydrated products after the hydration reaction.