Catalytic photodegradation of dyes by in situ zeolite-supported titania

Abstract

The degradation of dyes (methylene blue, direct blue 71, direct yellow 8) by a series of titania-supported catalysts generated in situ via the impregnation of TiCl4 onto a series of zeolite, which was synthesized using rice husks as the silicon source, was individually evaluated. After calcination, the resulting supported catalysts were characterized by X-ray diffraction spectrometry, ultraviolet–visible diffuse reflectance spectroscopy, diffuse reflectance and transmittance infrared Fourier transform spectroscopy, energy dispersive X-ray scanning electron microscopy, small angle X-ray scattering and differential pulse voltammetry. The titania generated is present in the anatase phase, without affecting the zeolite framework. Catalyst activity was shown to be comparable to that of the commercial P-25 catalyst after 1 h of UV light exposition. Monitoring the catalyst performance of several batches of material showed that P-25 provided the highest photodecomposition until the third cycle. On the other hand, the activity of the in situ-supported titania catalyst, in spite of showing lower catalytic activity, remained roughly constant up to the fifth cycle. This suggests that the catalyst generated in situ is more suitable for both filtering and reuse.