A comprehensive assessment of supported titania photocatalysts in a fluidized bed photoreactor: Photocatalytic activity and adherence stability

Titania (TiO₂) was immobilized onto hydroxylated glass beads (HGB) via the thermal bonding and sol–gel coating methods. The photocatalytic activity and adherence stability of the prepared supported photocatalysts were studied in a fluidized bed photoreactor. P25 thermally bonded HGB was found to be more active than sol–gel coated HGB prepared with the same immobilization conditions, while both of them exhibited poor adherence stability, i.e., large amounts of immobilized TiO₂ detached from HGB during the degradation. The adherence stability was improved with limited extents by increasing the calcination temperature or reducing the coverage of TiO₂ on HGB, but either of these approaches resulted in lower activity. The poor adherence stability was ascribed to the fluid shear force and particle friction in fluidized bed, as well as the insufficient bonding between TiO₂ and HGB in terms of the bonding mechanism.

Hydroxylated quartz sands (HQS) and silica gel beads (SGB) were further studied and used as supports. Results have shown that the adherence stability was significantly improved with SGB but only slightly improved with HQS. Characterizations results showed that a coarser surface and more surface Si–OH groups could improve the adherence stability of supported TiO₂ photocatalysts.