Ti/RuO2-IrO2 anodic electrochemical oxidation composting leachate biochemical effluent: Response surface optimization and failure mechanism

Abstract

In this work, the electrolytic process conditions for the electrochemical oxidation (EO) of composting leachate biochemical effluent (CLBE) were optimized via the response surface methodology (RSM). Meanwhile, a comparative study had been done on the failure characteristics of Ti/RuO₂-IrO₂ anodes in a single electrolyte solution system (H₂SO₄ and NaCl) and real wastewater (CLBE) by accelerated life tests, respectively. The RSM optimization results showed that the COD, NH₃-N and TN removal rates were 50.53%, 100% and 95.61% at 30 min, respectively, with a desirability value of 0.993. In parallel, the electrochemical and material characterizations were carried out on the electrodes before and after failure, by which the failure mechanism of Ti/RuO₂-IrO₂ anodes was clarified. On the whole, the true failure in the H₂SO₄ solution was attributed to coating dissolution and Ti substrate oxidation. In contrast, the electrode exhibited "apparent failure" due to the "bubble effect" in both NaCl and CLBE solutions, and the "effective roughness" formed compensated for the loss of activity caused by the absence of the coating. Besides, additional dissolution of the Ti substrate occurred in the CLBE solution due to the current edge effect and the presence of organic matter. This paper takes the actual wastewater as the research object and reveals its electrode failure mechanism, which provides a theoretical basis and reference for the subsequent optimization of the actual electrode service life.

Keywords: Accelerated life test; Electrochemical oxidation; Electrode failure; Response surface methodology; Ti/RuO(2)–IrO(2) anodic.