Selective oxidation of ammonia to dinitrogen gas by facile Co2+/PMS/chloridion process through reactive chlorine radicals

The selective oxidation of ammonia to dinitrogen gas in some special wastewater is of paramount significance, but still a challenge. In this study, chlorine radical (Cl•)-mediated oxidation process was developed to realize the selective oxidation of NH 4 + -N to N 2 , in which Cl• was generated in Co 2+ /peroxymonosulfate (PMS)/chloridion (Cl − ) system. The effect of various operational parameters on the efficiency and selectivity of ammonia oxidation to N 2 was investigated, such as PMS concentration, Co 2+ concentration, Cl − concentration and pH value. The experiment results showed that Cl•-mediated NH 4 + -N oxidation reaction exhibited high NH 4 + -N removal efficiency and considerable selectivity to N 2 in the range of pH from 2.0 to 6.5. The removal efficiency of NH 4 + -N was 90.39%, and the selectivity of NH 4 + -N to N 2 achieved up to 97.16%. The possible mechanism for high efficient and selective oxidation of NH 4 + -N to N 2 was tentatively proposed. The process developed in this study could provide a novel technology for the treatment and selective oxidation of ammonium in some special types of ammonium-containing wastewater.