A study of photoelectrocatalytic oxidation for wastewater treatment

Abstract

An innovative titanium/titanium dioxide (Ti/TiO2) mesh electrode was prepared in this study, in which 0.5M sulphuric acid was used as electrolyte and titanium (Ti) metal mesh was anodized in a combined mode of galvanstatic and potentialstatic anodization process. The innovated mesh electrode was first examined using Raman spectroscopy to determine the formation of TiO2 layer when different potentials of 120V, 140V, 160V and 180V were applied in the anodization. Up to 140V, the Raman spectra showed that the main anatase peaks were increasing while the applied anodization voltage increased. Above 160V, the additional peaks corresponding to the rutile phase of TiO2 were further developed. The spectra also indicated that the anatase phase of TiO2 was dominant in all the cases. Microporous surface of the electrode was also examined using scanning electron microscopy (SEM). The diameter of the pore size increased from 17nm to 60nm with a potential raising from 120V to 180V The photocatalytic (PC) oxidation and photoelectrocatalytic (PEC) oxidation were studied for treating synthetic wastewater solutions of wool dye and 2,4,6-trichlorophenol (TCP) respectively. About 75% and 81% of color removal efficiencies were achieved in PC and PEC (+0.6V) oxidation, respectively, using the 160V-mesh electrode for treating the wool dye solution after 80 minutes reaction time. It was also found that the PEC (+0.9V) oxidation enhanced the PC oxidation in treating the 2,4,6-TCP solution from 61% to 85%. In the condition without oxygen supply, the PEC oxidation performed a better efficiency than the PC oxidation for treating both dye and 2,4,6-TCP solutions. A constant photo-oxidation rate was maintained when the same mesh electrode was reused for at least three times. It implies that the Ti/TiO2 mesh electrode is an effective photoelectrode and has a potential for further development.