Hydrothermal synthesis and characterization of alkali metal titanium silicates

Preparation of granulated alkali metal titanium silicates is described in w hich the desired silicon to titanium ratio is controlled via a sol-gel rout e, using hexamethylenetetramine as an inner gelation reagent. The amorphous precursors are treated hydrothermally in the presence of NaOH or KOH solut ion under mild conditions (150-250 degrees C). By varying the Si:Ti molar r atio in the precursor, concentration of alkali, temperature and duration of treatment, six granular sodium titanium Silicates (Na2Ti2O3SiO4. 2H(2)O, N a2TiSi2O7. 2H(2)O, Na2TiOSiO4 and three novel phases characterized by the f irst reflection in the XRD at 10.8, 7.2 and 5.4 Angstrom, respectively) and two potassium titanium silicates [K3H(TiO)(4)(SiO4)(3). 8H(2)O, K2TiSi3O9. H2O] were synthesized. All compounds were characterized by elemental analy sis, TGA, powder XRD, SEM and Si-29 MAS NMR spectroscopy. Some of the titan ium silicates are thermally stable, possessing unique ion exchange properti es for alkali, alkaline earth, and some toxic heavy metal cations.