Improved charge transfer on heterophase colloidal TiO2 with interaction between inserted atom and peroxysulfate for refractive antibiotics removal under visible light

Photocatalysis is a sustainable technique having unparalleled advantages in wastewater treatment. Its catalytic efficiency can be greatly enhanced by combining with Fenton-like reactions, e.g., persulfate activation-based oxidation. However, the performance of this coupled technique is mainly limited by the development of catalysts that connect two catalytic reaction systems. Herein, heterophase colloidal TiO2 with insertion of heteroatoms C and N was synthesized as a physicochemical stable visible light responsive photocatalyst enabling persulfate activation to selectively generate strong radicals of •OH and SO4•− for removal of refractory pollutants (i.e., florfenicol) via an enhanced electron-transfer route. The optoelectronic characterizations and DFT calculation reveal the changes of band structure, charge transfer and migration pathway after C, N elements inserted into heterophase crystal lattice. The N site favors both separation of photogenerated charge carriers and activation of persulfate, and the coupling mechanism is disclosed in detail. Meanwhile, the participation of the strong radicals in the florfenicol decomposition and the toxicity of intermediates are discussed. This work highlights the importance of non-transition metal oxide-based catalysts for synergistic photocatalysis and persulfate activation and provides a deep insight into the synergistic mechanisms in generating strong radicals at the molecular level.