Selective and effective oxidation of ammonium to dinitrogen in MgO/Na2SO3/K2S2O8 system

The oxidation of ammonium (NH 4 + ) to dinitrogen (N 2 ) with high selectivity and high efficiency is still a challenge. Herein, a novel sunlight induced persulfate (PS)-based AOPs process (MgO/Na 2 SO 3 /PS/ hv ) was proposed by introducing solid base (MgO) and hydrated electron (e aq − ), to selectively oxidize NH 4 + to N 2 , with high selectivity and high efficiency at a wide range of pH value. The deprotonation of NH 4 + into NH 3 by MgO and the generation of •OH and SO 4 −• by PS activation were responsible for the high efficiency of NH 4 + oxidation. The buffering capacity provided by MgO to proton released from PS activation made the NH 4 + oxidation possible at a wide pH range. The e aq − from the Na 2 SO 3 / hv process was the main active specie to reduce NO 2 − and NO 3 − (NO x − ) into N 2 , responsible for high N 2 selectivity of NH 4 + oxidation. 100% NH 4 + could be oxidized within 30 min, and N 2 selectivity exceeded 96% at the initial pH range of 3–11 and the initial concentration of NH 4 + of 30 mg N/L. This work could offer an efficient AOPs process for selective NH 4 + oxidation, which is promising for the chemical denitrification of wastewater ….