Zeolite–TiO2 hybrid composites for pollutant degradation in gas phase.

This work presents a thorough assessment of the photocatalytic properties of a series of zeolite/TiO 2 composites for the degradation of pollutants in gas phase. The composites have been prepared by the incipient wet impregnation method using an acidic TiO 2 sol precursor and five different zeolites. The influence of the content of TiO 2 , 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/TiO 2 composites has been studied. Formaldehyde (HCHO) and a chlorinated hydrocarbon, trichloroethylene (C 2 HCl 3 ), have been used as model volatile organic compounds (VOCs). The composites obtained have been characterised by N 2 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 TiO 2 acidic sol is a suitable procedure to preparing well-dispersed TiO 2 nanoparticles around 5 nm 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. [ABSTRACT FROM AUTHOR]