Activation of Persulfate by Irradiated Magnetite: Implications for the Degradation of Phenol under Heterogeneous Photo-Fenton-Like Conditions

We show that phenol can be effectively degraded by magnetite in the presence of persulfate (S₂O₈^2–) under UVA irradiation. The process involves the radical SO₄^–•, formed from S₂O₈^2– in the presence of Fe^II. Although magnetite naturally contains Fe^II, the air-exposed oxide surface is fully oxidized to Fe^III and irradiation is required to produce Fe^II. The magnetite + S₂O₈^2– system was superior to the corresponding magnetite + H₂O₂ one in the presence of radical scavengers and in a natural water matrix, but it induced phenol mineralization in ultrapure water to a lesser extent. The leaching of Fe from the oxide surface was very limited, and much below the wastewater discharge limits. The reasonable performance of the magnetite/persulfate system in a natural water matrix and the low levels of dissolved Fe are potentially important for the removal of organic contaminants in wastewater