Abstract: Indirect electro-oxidation of the simulated wastewater containing ammonia-N in a filter press-type electrochemical cell was studied. The process obeys a second order reaction kinetics with a certain concentration of chlorine ion, when the concentration of NH₃-N is equivalent of/to the one of electro-generated active chlorine. The cell performance is influenced significantly by the operating conditions including current density, flow rate and initial concentration of NH₃-N. The results show that the best optimum operating condition is electrolyte flow rate of 60 L/h and current density of 60 mA/cm² in slightly alkaline(pH=8.0) solution with 0.1 mol/L NaCl and 1 mol/L Na₂SO₄ as a supporting electrolyte at 25 ℃, and kinetic rate constant k₂=3.23×10^-5 m³/(mol·s). The information about the spatial distribution of the reactions may be obtained from the Hatta number. The value of the Hatta number(<0.3), estimated under different operation conditions, implies that most of the reaction of the ammonia with active chlorine occurred in the bulk solution, which provided the effective information to design the electrochemical cell.

Key words: Indirect electro-oxidation of NH₃-N, Active chlorine, Second order reaction kinetics, Filter-press type electrochemical cell, Hatta number