Efficient photocatalysis and sustainable degradation of methylene blue by titanium dioxide and zinc oxide supported on spent FCC catalyst

Zinc oxide (ZnO) and titanium dioxide (TiO2) are loaded on the spent fluid catalytic cracking catalyst (FCC) via an impregnation method to form the composite material, which is named as Zn-Ti/FCC in this article. The photo-catalytic performance of the Zn-Ti/FCC composite is evaluated by degradation efficiency of methylene blue (MB). After the photocatalytic degradation, the MB was almost completely degraded with the Zn-Ti/FCC composite. The lattice mismatch of the ZnO and TiO2 lead to an electric field at the interface between the ZnO and TiO2. The Fermi levels of ZnO and TiO2 reach a new equalization state, the separates the charges leading to higher photocatalytic activity. Because of the formation of a heterojunction between ZnO and TiO2, the conduction band (CB) of ZnO is more active than TiO2, the electrons in the CB of ZnO would transfer to the CB of TiO2. The heterojunction between ZnO and TiO2 promote the separation of the electron hole pairs, which can improve the photocatalytic degradation of MB. The degradation rate of methylene blue with the Zn-Ti/FCC, Zn/FCC and Ti/FCC have reached to nearly similar to 98%, similar to 52% and similar to 59%, respectively. The excellent photocatalytic degradation performance of the Zn-Ti/FCC towards MB is expected to further develop the dye processing industry. Moreover, these composites fabricated process can also provide an effective method to dispose the spent FCC catalyst in industry.