The Preparation of Photoactive TiO2/NaX Zeolite Composites under Hydrothermal Conditions with the Use of Solutions with a High Concentration of Titanium Polyhydroxo Complexes

Abstract

Composites of titanium dioxide and NaX zeolite containing 50, 70, and 80% TiO₂ by weight relative to the zeolite in their composition are obtained using solutions with a high concentration of polyhydroxo complexes of titanium in a pressurized reactor. The materials are characterized by X-ray diffraction, IR spectroscopy, scanning electron microscopy, energy-dispersive microanalysis, and low-temperature adsorption–desorption of nitrogen. The adsorption and photocatalytic properties of the composites are studied by way of example of a model dye, Rhodamine B. The phase composition of the photoactive coating (the ratio of anatase and rutile); morphology of its surface; and textural, adsorption, and photocatalytic properties of the obtained composites to a significant extent depend on the degree of coverage of the surface of the zeolite. The properties of the microporous zeolite carrier after coating with titanium dioxide are transformed into the properties of a mesoporous material in the composite. The highest photocatalytic activity is found for the 80% TiO₂/NaX composite (with a size of TiO₂ crystallites of about 13 nm and an anatase/rutile ratio of phases of about 0.97). Complete discoloration of the dye (concentration of 10 mg/L, amount of the photocatalyst composite of 1 g/L) under UV irradiation (lamp power of 250 W) is observed over 90 min.