Immobilization of highly active titanium dioxide and zinc oxide hollow spheres on ceramic paper and their applicability for photocatalytic water treatment

Titanium dioxide and zinc oxide hollow spheres were synthesized using carbon spheres as templates. To investigate their practical applicability, they were immobilized on ceramic paper support using titanium(IV) isopropoxide as an adhesive. The immobilization process was successful, reinforced by X-ray diffraction, scanning electron microscopy and infrared spectroscopy measurements. The photocatalytic activity of the samples was investigated by applying them in both suspended and immobilized forms. These measurements were performed under UV-A irradiation using phenol as a pollutant. To investigate reusability and stability, the photocatalytic experiments were carried out consecutively three times. After immobilization, the photocatalytic activity order observed for hollow TiO2 and hollow ZnO was reversed. The formation of a heterojunction was deduced to be responsible for the observed photocatalytic activity. The immobilized catalysts were demonstrated to be highly reusable as they largely retained their photocatalytic activity during the repeated measurements, and no catalyst leaching was observed.