Preparation and characterization of Fe3+-doped TiO2 on fly ash cenospheres for photocatalytic application

Fe3+-doped TiO2 film deposited on fly ash cenosphere (Fe-TiO2/FAC) was successfully synthesized by the sol-gel method. These fresh photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analyses (TGA). The XRD results showed that Fe element can maintain metastable anatase phase of TiO2, and effect of temperature showed rutile phase appears in 650 °C for 0.01% Fe-TiO2/FAC. The SEM analysis revealed the Fe-TiO2 films on the surface of a fly ash cenosphere with a thickness of 2 μm. The absorption threshold of Fe-TiO2/FACs shifted to a longer wavelength compared to the photocatalyst without Fe3+-doping in the UV-vis absorption spectra. The photocatalytic activity and kinetics of Fe-TiO2/FAC with varying the iron content and the calcination temperatures were investigated by measuring the photodegradation of methyl blue (MB) during visible light irradiation. Compared with TiO2/FAC and Fe3+-doped TiO2 powder (Fe-TiO2), the degradation ratio using Fe-TiO2/FAC increased by 33% and 30%, respectively, and the best calcined temperature was 450 °C and the optimum doping of Fe/Ti molar ratio was 0.01%. The Fe-TiO2/FAC particles can float in water due to the low density of FAC in favor of phase separation to recover these photocatalyst after the reaction, and the recovery test shows that calcination contributes to regaining photocatalytic activity of Fe-TiO2/FAC photocatalyst.

Research highlights▶ Compared with TiO2/FAC and Fe-TiO2, the degradation ratio using Fe-TiO2/FAC increased by 33% and 30%, respectively. ▶ These synthesized Fe-TiO2/FAC composites can take advantage of visible light irradiation and can be easily separated from water after the reaction due to their buoyant property. ▶ It's easy and convenient to recycle these catalysts without leaving any decrescence in photocatalytic ability through calcination.