Unveiling the Removal Mechanism and Electrode Fate During Electrocatalytic Treatment of Mature Landfill Leachate with Ti/RuO2–IrO2 Anodes

The compliant discharge of landfill leachate constitutes a pivotal factor for the effective implementation of integrated water resource management. Aged landfill leachate exhibits complex composition and an imbalanced carbon-to-nitrogen ratio. Electrocatalytic oxidation technology, as an efficient advanced oxidation process, demonstrates promising application potential. This study employed Ti/RuO2–IrO2 Anodes for the electrocatalytic oxidation treatment of aged landfill leachate. The removal efficiencies and variation patterns of chemical oxygen demand (COD), ammonia nitrogen, and total nitrogen at different current densities and reaction times were systematically investigated, along with an analysis of energy consumption and current efficiency. The degradation and transformation processes of organic matter were elucidated using Three-dimensional Excitation–Emission Matrix (EEM) Spectra. Fresh anodes and those used for 1000 h were characterized by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) to elucidate their failure mechanisms. The results demonstrate that electrocatalytic oxidation achieves efficient pollutant removal. At a current density of 1000 A/m2 and a reaction time of 30 min, the effluent concentrations of ammonia nitrogen and total nitrogen satisfied the discharge standards, while COD complied with emission requirements after 60 min. The pollutant removal efficiencies were positively correlated with current density and reaction time. EEM analysis revealed that the electrocatalytic process effectively disrupts the structure of macromolecular organic matter, degrading it into smaller molecules and eventually achieving complete mineralization. Electrode characterization identified titanium substrate corrosion due to coating cracks and coating detachment as the primary causes of electrode failure. This study confirms the effectiveness of electrocatalytic oxidation technology for treating aged landfill leachate, and provides a theoretical foundation and technical support for its practical engineering application. The technology exhibits considerable theoretical significance and promising application potential in the treatment of landfill leachate.