Synergistic effects of TiO2 photocatalysis in combination with Fenton-like reactions on oxidation of organic compounds at circumneutral pH

The integration of two different AOPs often offers synergistic reaction routes for the production of OH. In this study, synergistic production of OH was observed in the combined system of TiO2 photocatalysis and the Fenton-like reaction, causing a drastic enhancement in the oxidation of organic compounds at circumneutral pH values. The photolytic experiments using organic substrates (i.e., phenol, benzoic acid, and methanol) and valence band hole and OH scavengers (i.e., formate and tert-butyl alcohol) show that the synergistic effects result from dual roles of iron as an electron acceptor to facilitate charge separation in TiO2 photocatalyst and as a Fenton reagent to catalyze conversion of H2O2 into OH. A noteworthy observation is that the adsorption of iron onto the photoexcited TiO2 surface possibly modifies electron transfer properties of iron toward H2O2 at neutral pH to convert the resultant reactive oxidant from Fe(IV) into a stronger form, likely OH.

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► The combination of UV/TiO2 and Fe(III)/H2O2 leads to synergistic degradation of contaminants.
► The synergistic effects result from dual roles of iron. Iron facilitates charge separation in TiO2 photocatalyst.
► Iron on the photoexcited TiO2 surface does not produce Fe(IV) via the Fenton reaction.