Comparative study of visible-light-driven photocatalytic mechanisms of dye decolorization and bacterial disinfection by B–Ni-codoped TiO2 microspheres: The role of different reactive species.

The controversy of mechanism still exists over whether photocatalytic decontamination proceeds via photon-generated h+, e−, ꔷOH, ꔷO2− or H2O2. This study aims to investigate the roles of these reactive charges and oxidative species in the photocatalytic dye decolorization and bacterial disinfection processes in the presence of a visible-light-driven (VLD) photocatalyst, B–Ni-codoped TiO2 microsphere, by employing various scavengers in the photocatalytic system and utilizing a novel partition system. Significant differences between VLD photocatalytic dye decolorization and bacterial disinfection are found. For photocatalytic dye decolorization, the reaction mainly occurs on the photocatalyst surface with the aid of surface-bounded reactive species (h+, ꔷOHs and ꔷO2−), while bacterial cell can be inactivated by diffusing reactive oxidative species such as ꔷOHb and H2O2 without the direct contact with the photocatalyst. The diffusing H2O2 plays the most important role in the photocatalytic disinfection, which can be produced both by the coupling of ꔷOHb in bulk solution and ꔷOHs on the surface of photocatalyst at the valence band. Furthermore, the ꔷO2−, which is detected by using the electron spin resonance technique, is found to have direct function for the photocatalytic disinfection process. This study establishes a facile and versatile research methodology to investigate the VLD photocatalytic mechanism in different photocatalytic system. [ABSTRACT FROM AUTHOR]