Enhanced electrochemical harmless removal of ammonia nitrogen and simultaneously recovery of phosphorus with peroxydisulfate activated by Fe inductive electrode

Herein, peroxydisulfate (PDS) was introduced to the electrochemical (EC) system, which consisted of a Ti/RuO2 anode, a Ti cathode, and an Fe inductive electrode (EC/PDS system). A significant enhancement for removal of ammonia nitrogen (NH4+) and orthophosphate (PO43−) was observed in this system, while simultaneously recovery of phosphorus (P). Specifically, the removal efficiency of NH4+ was increased from 53 % to 100 % and the removal efficiency of PO43− was increased from 66 % to 100 % with 5 mM PDS addition (initial NH4+-N concentration, 100 mg/L; initial PO43−-P concentration, 10 mg/L; initial Cl− concentration, 100 mM; cell voltage, 2.5 V; reaction time, 60 min; initial pH, 3.0). Under these conditions, NH4+ was harmlessly removed in the form of nitrogen (N2) by chloride radicals (Cl) generated via the reaction of sulfate radical (SO4−) with chloride ions (Cl−). PO43− was combined with Fe3+ generated by the Fe inductive electrode to form FePO4 precipitates, achieving P recovery. This system demonstrated superior stability in cycling experiments. The performance for treatment of actual wastewater via this system showed completely harmless removal of NH4+ and simultaneously recovery of PO43− as FePO4. This study can provide reference for the treatment of wastewater containing NH4+ and PO43−.