Electrolytic removal of ammonia from aqueous phase by Pt/Ti anode

This study investigated the mechanism and kinetic modeling of electrolytic degradation of ammonia with Pt/Ti anode. The results show that ammonia oxidation from direct oxidation or indirect oxidation with hydroxyl radicals was slow but can be observed under pH 9 and high initial ammonia concentration of 1,050 mg N L⁻¹. Indirect oxidation with HOCl was the mechanism for the chloride-mediated electrolytic removal of ammonia. In this process, pH between 3 and 9 had little effect on the ammonia removal rate, but current density (j) and chloride concentration ([Cl⁻]) showed a linear relationship with ammonia removal rate within the range of 3.8–15.4 mA cm⁻² and 30–300 mg L⁻¹, respectively. The ammonia removal could be described by a pseudo-zero order kinetics with a mathematic equation of k = 0.0003 × [Cl⁻] × j − 0.076. Treatment of the actual wastewater effluent from a secondary clarifier in a local wastewater treatment plant showed an ammonia removal rate of 0.8 mg N L⁻¹ h⁻¹ and energy cost of 14 kJ per mg N ammonia.