Characterization of synthetic aluminum silicate-coated titanium dioxide photocatalysts as a functional filler

Synthetic amorphous aluminum silicates-coated titanium dioxides (AS–T nanocomposites) were synthesized by a hydrothermal reaction of aluminum silicate precursors with various chemical compositions and titanium dioxide suspensions. AS–T nanocomposites showed narrow particle size distributions centered between 1.0 and 2.0 μm and their specific surface areas were ranging from 138 to 209 m²/g. Water vapor adsorption isotherms revealed that AS–T nanocomposites with higher Si/Al ratios exhibited high hydrophilicity, as the maximum water adsorption rate reached almost 40 wt%. In methylene blue photocatalytic degradation tests, AS–T nanocomposites with higher Si/Al ratios showed much higher photodegradability than a commercial titanium dioxide, degrading up to 92.7% of methylene blue after 30 min of UV irradiation. A possible mechanism is that a distribution state of Si(Al)–OH and/or Si–OH–Al exposed on the aluminum silicate surface influenced the methylene blue adsorption to the surface, which significantly improved the photodegradation performance. The results of this study indicate that AS–T nanocomposites have the potential to be used as fillers in paints.