Visible Light-Driven Selective Organic 1 Degradation by FeTiO3/Persulfate System: the 2 Formation and Effect of High Valent Fe(IV)

Abstract

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 FeTiO3/persulfate system using methyl phenyl sulfoxide as the probe. The FeTiO3/persulfate/light system is capable of selectively degrading aromatic compounds with a higher ionization potential including tetracycline and bisphenol A by photo-generated high-valent Fe(IV). The contributions from SO· 4, ·OH and 1O2 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 SO2 4on the FeTiO3 surface; this complex is, however, the key intermediate for Fe(IV) production under the light irradiation. This study reveals the long-ignored role of SO2 4 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.