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

The oxidation of ammonium (NH4+) to dinitrogen (N2) with high selectivity and high efficiency is still a challenge. Herein, a novel sunlight induced persulfate (PS)-based AOPs process (MgO/Na2SO3/PS/hv) was proposed by introducing solid base (MgO) and hydrated electron (eaq−), to selectively oxidize NH4+ to N2, with high selectivity and high efficiency at a wide range of pH value. The deprotonation of NH4+ into NH3 by MgO and the generation of •OH and SO4−• by PS activation were responsible for the high efficiency of NH4+ oxidation. The buffering capacity provided by MgO to proton released from PS activation made the NH4+ oxidation possible at a wide pH range. The eaq− from the Na2SO3/hv process was the main active specie to reduce NO2−and NO3− (NOx−) into N2, responsible for high N2 selectivity of NH4+ oxidation. 100% NH4+ could be oxidized within 30 min, and N2 selectivity exceeded 96% at the initial pH range of 3–11 and the initial concentration of NH4+ of 30 mg N/L. This work could offer an efficient AOPs process for selective NH4+ oxidation, which is promising for the chemical denitrification of wastewater ….