Corrosion behavior of pure titanium anodes in saline medium and their performance for humic acid removal by electrocoagulation

Abstract

The corrosion behavior of Ti electrodes and the dependence of their anodic dissolution with the experimental conditions, namely pH, current density (j) and supporting electrolyte nature, have been investigated. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests have been performed. It has been found that pH has a relevant effect on the electrochemical dissolution of Ti. In chloride medium, metal dissolution was partially caused by pitting corrosion and the corrosion potential was shifted to more cathodic values. Conversely, in phosphate medium, corrosion was inhibited by the formation of a compact passive layer of titanium hydroxide/phosphate. Further, the mechanisms of sacrificial Ti anode dissolution during the electrocoagulation process are discussed. The influence of the supporting electrolyte, pH and j on the effectiveness of the electrocoagulation process for humic acid (HA) removal was assessed. Under optimized conditions, total decolorization was achieved in 60 min, eventually attaining 94% total organic carbon (TOC) removal.