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 (S2O82-) under UVA irradiation. The process involves the radical SO4, formed from S2O82 in the presence of FeII. Although magnetite naturally contains FeII, the air-exposed oxide surface is fully oxidized to FeIII and irradiation is required to produce FeII. The magnetite + S2O82 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.