Enhancing nitrogen removal from wastewater via photoelectrocatalytic oxidation over a Ru/TiO2 system

Water pollution is a significant global environmental concern that threatens the sustainable progress of humanity. In this study, the concepts of photocatalytic oxidation in the cathodic zone (NH₄⁺-N adsorption-NH₃-N conversion) and electrochemical oxidation in the anodic zone (NH₄⁺-N direct oxidation + chlorination) were proposed to remove ammoniacal nitrogen, and experimental studies were conducted. The stirring of the test solution during the reaction process enhanced the ammoniacal nitrogen removal efficiency by ∼9% after 90 min of reaction. The removal efficiency of ammoniacal nitrogen was comparatively high at low concentrations. After 60 min of reaction in the presence of 15 mg·L⁻¹ ammonium chloride, the removal efficiency exceeded 95%; the removal efficiency of ionized ammonia increased with increasing current density. After 60 min, the removal efficiency of ammoniacal nitrogen exceeded 80%. Under the same ammoniacal nitrogen concentration conditions, the ammoniacal nitrogen removal efficiency in the test solution increased with the increase in the chlorine ion concentration, and in the absence of chlorine ions, ammoniacal nitrogen removal in the electrochemical reaction environment was insignificant. Under the same power and light conditions, the photoelectrochemical reaction exhibited a ∼15% higher ammoniacal nitrogen removal efficiency than electrochemical oxidation.