Exploring Disposal Efficiency of COD, NH₃-N, and Turbidity in Diluted Real Leachate Using Ti/PdO-CoO Electrodes in an Electrooxidation Cell: An Investigation into Oxidation Mechanism and Reaction Kinetics Studies

Abstract

In this study, Pd and Co metal oxides, electrochemically deposited on a titanium (Ti) substrate, were utilized to remove chemical oxygen demand (COD), NH3-N, and turbidity from diluted Bingöl leachate. The plating bath was prepared with 7 mM palladium chloride (PdCl2) and 1 mM cobalt chloride (CoCl2), along with 1.68 M NH4Cl, and 0.16 M H3BO3. In the electrooxidation (EO) cell, the anode consisted of a Ti/PdO-CoO electrode, while the cathode was a stainless-steel electrode. The Ti/PdO-CoO electrode demonstrated an actual functional life of 96 hours, as determined through accelerated life testing. X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy examinations revealed that the surface of the Ti substrate was coated with PdO and CoO. Turbidity, NH3-N, and COD were electrooxidized indirectly due to the high chloride content (718 mg/L). In the presence of 10 mM NaCl, the highest removal efficiency for NH3-N, COD, and turbidity was 60.5%, 64.9%, and 96.5%, respectively. The removal of COD, NH3-N, and turbidity fit pseudo-second-order (PFO) kinetics (R² 0.97-0.99). For a COD efficiency of 60.5% at 25 mA/cm2, the corresponding energy consumption, unit energy consumption, and electrode cost were 56.25 kWh/m3, 200.89 kWh/kg-COD, and 2.37 ($/kg-COD), respectively.