Multinuclear Solid-state NMR Study on the Calcium Ions Extracting Process of Layered Sodium Disilicate SKS-6

The reactions of layered sodium disilicate SKS-6 and calcium chloride solution with invariant concentration reacted for different reaction times were studied using solid-state 1H, 29Si, and 23Na nuclear magnetic resonance (NMR) spectroscopy as well as X-ray powder diffraction technique. On the basis of the experimental results the calcium ions extracting process of SKS-6 was shown to be rapid ions substitution of sodium ions by calcium ions. After substitution, calcium ions combined with the SiO4 tetrahedrons in SKS-6, and the ordering of the silicate layer was decreased to a certain extent, with the survival of original layered structure. Ion substitution rapidly proceeded and almost was completed within 1 min because prolonging the reaction time introduced no obvious variation in it. Prolonging the reaction time just prompted the hydrolysis of bridging as well as nonbridging oxygen atoms in SKS-6, and simultaneously changed the chemical circumstance of sodium ions in the newly formed kanemite phase.