Hydrothermal synthesis and characterization of alkali metal titanium silicates
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Preparation of granulated alkali metal titanium silicates is described in which the desired silicon to titanium ratio is controlled via a sol-gel route, using hexamethylenetetramine as an inner gelation reagent. The amorphous precursors are treated hydrothermally in the presence of NaOH or KOH solution under mild conditions (150-250 °C). By varying the Si:Ti molar ratio in the precursor, concentration of alkali, temperature and duration of treatment, six granular sodium titanium silicates (Na2Ti2O3SiO4·2H2O, Na2TiSi2O7·2H2O, Na2TiOSiO4 and three novel phases characterized by the first reflection in the XRD at 10.8, 7.2 and 5.4 Å, respectively) and two potassium titanium silicates [K3H(TiO)4(SiO4)3·8H2O, K2TiSi3O9·H2O] were synthesized. All compounds were characterized by elemental analysis, TGA, powder XRD, SEM and 29Si MAS NMR spectroscopy. Some of the titanium silicates are thermally stable, possessing unique ion exchange properties for alkali, alkaline earth, and some toxic heavy metal cations.
author list (cited authors)
Khainakov, S. A., Bortun, A. I., Bortun, L. N., Clearfield, A., Trobajo, C., & García, J. R.