Synthesis of Titania Nanoparticles Loaded on Clinoptilolite as Photocatalyst by Sonochemistry

In past decades, titanium dioxide semiconductor (TiO2) has attracted great interest due to its photocatalytic properties. It is inexpensive, non-toxic, stable, and potentially reusable in water [1-3]. However, the practical applications of TiO2 as an adsorbent or a photocatalyst in aqueous solutions are limited because of the recovery problems of fine TiO2 particles. Recently, attempts have been made to immobilize the TiO2 particles on different supports to improve their separation from bulk water. Zeolites are three dimensional alumino silicate minerals with a porous structure that have valuable physicochemical properties, such as cation exchange, molecular sieving, catalysis and adsorption. Natural zeolites are cheap, abundant and easily available [2, 3]. It is a promising support for TiO2 because they have regular pores and channels that can confine substrate molecules, thereby enhancing adsorption and photocatalysis. One of the effective methods in this field is sonochemistry or the use of ultrasound to perform chemical reactions [4]. The sonochemical method results in improved dispersion of the active and uniform phases and decreases the particle size and thus increases the surface area. In addition, the use of ultrasonic waves during synthesis can substantially shorten the catalyst preparation time (about 22 min in this study). This study investigated the photocatalytic behavior of Titania based on Clinoptilolite (TiO2/CP) in the decolorization of Methylene Blue which synthesized by sonochemistry method. Semnan natural zeolite (Clinoptilolite) was the adsorbent of choice due to its good adsorption property and availability at an affordable cost. The results of XRD analysis was indicated that the intensity of zeolite peaks in the composite sample is lower than that of the single zeolite, indicating a contrast between the titania precursor with the zeolite and the reduced crystallinity of it. The characteristic diffraction peaks of TiO2 can be observed at 2θ=25.4o corresponding to the (101) plane of anatase, indicating that TiO2 has been impregnated within the sample. The average crystallite size of the TiO2/CP was calculated using the Scherrer equation to be about 55 nm. The results of the SEM images are in agreement with the XRD analysis and show that the structure of the zeolite in the composite sample has not changed and the titanium spherical nanoparticles are visible as clusters attached to the zeolite. Complete decolorization of MB (20 ppm) by synthezied photocatalyst (0.15 g) was occurred after 2 hr irradiation by UV lamps (Two lamp – 6W). This excellent catalytic ability was mainly attributed to the hybrid effect of the photocatalyst and adsorbent. The results provided new insight into the performance of active photocatalysts on the treatment of wastewater. In addition, the immobilization of TiO2 onto natural zeolite permitted easier separation of the adsorbent from the treated water.

Keywords:

Titania , Clinoptilolite , Photocatalyst , Sonochemistry