Photocatalytic selective oxidation of ammonium to dinitrogen by FeOx-MgO activated persulfate under solar-light irradiation

The selective oxidation of ammonium nitrogen (NH 4 + -N) to dinitrogen (N 2 ) by advanced oxidation processes (AOPs) is of paramount significance, but it is still a great challenge. In this study, a novel composite (FeO x -MgO) was synthesized to activate persulfate (PS) for selective oxidation of ammonium (NH 4 + ) to N 2 under simulated solar-light irradiation ( hv ). The results demonstrated that the conversion of NH 4 + to ammonia (NH 3 ) on the basic sites of FeO x -MgO was a key step for the selective oxidation of NH 4 + . Fe(IV) species formed in FeO x -MgO/PS/ hv system could enhance both the efficiency and N 2 selectivity of the NH 4 + -N oxidation through the oxidation of ammonia hydride to N 2 . The 100 % NH 4 + -N removal and over 95.5 % N 2 selectivity could be achieved after 30 min when initial pH was in range of 2–10, and the initial NH 4 + -N concentration was 30 mg N/L. This study could provide a promising technology for the selective oxidation of NH 4 + -N to N 2 in water and wastewater.