Developing efficient methods to degrade perfluorochemicals (PFCs), an emerging class of highly recalcitrant contaminants, are urgently needed in recent years, due to their persistence, high toxicity, and resistance to most regular treatment procedures. Here, a UV-photolysis system is reported for efficient mineralization of perfluorooctanoic acid (PFOA) via irradiation of ferric nitrate aqueous solution, where in-situ generating *NO2 and the effective Fe(3+)/Fe(2+) redox cycle synergistically play great roles on rapidly mediating the mineralization of PFOA. A fast PFOA removal kinetics with fi...