Zeolite–TiO2 hybrid composites for pollutant degradation in gas phase

Abstract

This work presents a thorough assessment of the photocatalytic properties of a series of zeolite/TiO2 composites for the degradation of pollutants in gas phase. The composites have been prepared by the incipient wet impregnation method using an acidic TiO2 sol precursor and five different zeolites. The influence of the content of TiO2, the zeolite structure (Zeolite Y and ZSM-5) and the Si/Al ratio in the textural properties, adsorption capacity and the photodegradation activity of the zeolite/TiO2 composites has been studied. Formaldehyde (HCHO) and a chlorinated hydrocarbon, trichloroethylene (C2HCl3), have been used as model volatile organic compounds (VOCs). The composites obtained have been characterised by N2 adsorption–desorption, XRD, TGA-DTA, SEM and TEM microscopy. Electrophoretic migration measurements and adsorption ability in dynamic conditions for both model molecules was determined. The incipient wet impregnation method using a TiO2 acidic sol is a suitable procedure to preparing well-dispersed TiO2 nanoparticles around 5nm onto microporous zeolites. The results shown in this work reveal that the nature of the pollutant and the physicochemical characteristic of the zeolites have a strong influence on the adsorption ability and in the photocatalytic performance of the composites, reducing the formation of non-desirable reaction by-products. An adequate balance between the surface area and adsorption ability is required in order to optimise the photocatalytic efficiency.