In-situ growth of Fe clusters on MXene for fluorinated fire-fighting foam wastewater purification in peroxone system

Fluorinated fire-fighting foam wastewater is typical perfluorooctanesulfonic acid (PFOS) containing wastewater. Sodium p-perfluorous nonenoxybenzene sulfonate (OBS) as the alternative to PFOS in fire-fighting foam wastewater pose a new environmental risk, yet the degradation mechanism of OBS in real water matrices is not clear. Herein, we constructed a heterogeneous H₂O₂/O₃ system and adopted a vacuum ball milling strategy to successfully grow iron oxide clusters (FeBMT) in situ on the MXene surface. The system achieved a high OBS removal of 71 % in actual firefighting wastewater in only 1 min, which was superior to homogeneous H₂O₂/O₃. This was attributed to the combination of H₂O₂ with iron atoms on the surface of MXene to form *OOH species. O₃ would further associate with *OOH to promote the production of ·OH and ¹O₂. Then the benzene ring and double bond portion of OBS would be attacked by ·OH and ¹O₂. The coexisting microplsatics in the watswater altered the conversion pathway of OBS in this system and inhibited the production of certain highly toxic intermediates during OBS degradation. This study provided a more comprehensive understanding of the removal of OBS and fluorinated fire-fighting foam wastewater in composite pollution scenarios.