Highly dispersed titania-supported iron oxide catalysts for efficient heterogeneous photo-Fenton oxidation: Influencing factors, synergistic effects and mechanism insight.

Titania (TiO) supported iron oxides (Fe-TiO) are ideal catalysts to be applied in heterogeneous photo-Fenton oxidation (HPFO) for wastewater treatment because of the capabilities of TiO in photocatalysis and iron oxides in interfacial HO activation. It is important to understand the influences of the structural parameters of Fe-TiO catalysts and the complicated interplay between TiO and iron oxides on the performance of HPFO. In this paper, a series of Fe-TiO catalysts are obtained through a facile solid-phase synthesis method. The iron loading content and the calcination temperature are systematically adjusted to tune the crystal phase, size, anatase/rutile ratio and density of oxygen vacancy (O) site of TiO, the dispersing state of iron species, and the interfacial structure of the Fe-TiO catalysts. Then, the performance of these catalysts in HPFO for degrading methylene blue (MB) are comparatively studied. Correlations between the performance and various structural properties of the catalysts are clarified. The interplay between TiO and iron oxides in the HPFO process is elucidated. The insight reaction mechanism is also discussed. Under optimized conditions (an iron loading of 1 wt% and a temperature of 600 °C), Fe-TiO catalysts with iron lattice doping, well-dispersed ultrasmall α-FeO nanoparticles, appropriate anatase/rutile ratios and abundant O sites can be obtained. The anatase-rutile-FeO heterojunction, ultrasmall α-FeO nanoparticles and O sites in the optimized catalysts work synergistically to improve the charge migration and interfacial activation of HO, leading to superior HPFO performance for MB degradation and mineralization.