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 FeTiO3/persulfate system using methyl phenyl sulfoxide as the probe. The FeTiO3/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 SO4 center dot-, (OH)-O-center dot and O-1(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 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 SO42- 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.

Automated summary

The study explores the role of high-valent Fe in persulfate-based heterogeneous reactions using a FeTiO3/persulfate system. It reveals the selective degradation of aromatic compounds by photo-generated Fe(IV) and the formation of a complex between Fe(III) and SO(4)(2-) under dark conditions. The study calls for a re-evaluation of the oxidation mechanism in persulfate-based reactions.