Electrochemical oxidation of ammonia in a granular activated carbon/peroxymonosulfate/chlorine three-dimensional electrode system

The electrochemical conversion of ammonia into harmless nitrogen gas (N2) remains a significant challenge in wastewater treatment. This study explores the utilization of granular activated carbon (GAC) as three-dimensional particle electrodes within a peroxymonosulfate (PMS)/Cl−-PbO2/Ti electrochemical system to enhance ammonia oxidation and N2 transfer efficiency. In the observed experimental parameters designated as optimal, the system demonstrated a complete amelioration of ammonia within 45 min. The porous surface of GAC electrodes facilitates increased contact area, promoting better interaction with target compounds. This interaction leads to improved mass transfer efficiency, reduced chlorine overpotential, and enhanced current response. Quenching experiments reveal the substantial involvement of hydroxyl radicals (•OH), sulfate radicals (SO4•−), and chloride radicals (Cl•) in the oxidation process of NH4+-N, with Cl• generation through the oxidative process involving Cl− and SO4•− under electrical stimulation. After 90 min, a significant portion of NH4+-N is transformed into N2, achieving a conversion efficiency of 71.5 %. Additionally, the system demonstrates efficient removal of ammonia from practical aqueous environments. Three-dimensional fluorescence spectroscopic analysis confirms the system's effectiveness not only in removing ammonia but also in reducing organic substances resembling fulvic acid. These findings underscore the three-dimensional electrochemical GAC/PMS/Cl− system as a promising and efficient approach for ammonia removal in wastewater treatment applications.