Visible Light-Driven Selective Organic Degradation by FeTiO3/Persulfate System: the Formation and Effect of High Valent Fe(IV)

The role of high-valent Fe has rarely been explored in persulfate-based heterogeneous reaction. Herein, the existence of Fe(IV) is verified in a visible light-assisted FeTiO 3 /persulfate system using methyl phenyl sulfoxide as the probe. The FeTiO 3 /persulfate/light system is capable of selectively degrading aromatic compounds with lower ionization potentials including tetracycline and bisphenol A by photo-generated high-valent Fe(IV). The contributions from SO 4 ·- , · OH and 1 O 2 are excluded. The comparable efficiency in the dark requires higher dosages and suffers from a rapid deactivation. Based on XPS, Raman and EPR analyses, the poor dark activity is caused by the formation of a complex between in situ formed Fe(III) and SO 4 2- on the FeTiO 3 surface; this complex is, however, the key intermediate for Fe(IV) production under the light irradiation. This study reveals the long-ignored role of SO 4 2- as an abundant species in iron-based persulfate systems. We also call for re-evaluating the real oxidation mechanism in other persulfate-based reactions considering the different oxidation mechanisms of radicals and high-valent iron.