Photocatalytic Activity of Immobilized Geometries of TiO₂

Abstract

Photocatalysts that are used for waste water treatment are often suspended in the waste water during processing and then must be removed from the water after treatment. To reduce the post-degradation expenses and time, separation is facilitated by an immobilization process. The effect of immobilized TiO₂ geometries on the photocatalytic behavior of the photocatalyst is investigated in this work. Powder, fiber, film, and network-shaped TiO₂ nanocatalysts were produced by using different templates. The cellulose fiber and ceramic templates were used as substrates for fiber and film/network geometry production. The products were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area measurement. The photocatalytic performance was determined by methyl orange degradation and cyanide photo-oxidation under ultraviolet irradiation. From the SEM images, the size range of the TiO₂ particles in the film and in the network geometries were 20-60 nm. The nanoparticles had covered the surface of the substrate, uniformly. Removal of the cellulose substrate by heat treatment yielded hollow TiO₂ fibers with diameters of 0.5-1 µm and lengths of 30 µm. The efficiencies of both photocatalytic reactions were obtained in the following order: powder > network > film > fiber geometry. The rate constant of the dye degradation reaction using powder catalyst was 0.0118 min⁻¹. For network catalyst, it was 0.0083 min⁻¹. Corresponding results for cyanide disinfection were 0.0055 and 0.0046 min⁻¹. Although powder samples had higher rate constants, network geometry was preferred due to its higher immobility.