Photooxidation of wool dye and TCP in aqueous solution using an innovative TiO2 mesh electrode

Abstract

An innovative titanium dioxide (TiO2) mesh electrode was prepared by anodisation, in which 0.5 M sulphuric acid was used as electrolyte and titanium (Ti) metal mesh was anodised in a two stage anodic process. The innovated mesh electrode was examined using Raman spectroscopy to determine the formation of TiO2 layer when different potentials of 120 V, 140 V, 160 V, and 180 V were applied in anodisation. Microporous surface of the electrode was also examined using scanning electron microscopy. The photocatalytic (PC) oxidation and photoelectrocatalytic (PEC) oxidation were studied using the new electrode for treating synthetic wastewater solutions of dye and trichlorophenol (TCP) respectively. The colour removal efficiency of 68% was achieved using the 160V-mesh electrode for treating wool dye solution after 80 minutes reaction time. However, it was found that a significant substrate adsorption on the surface of the mesh electrode could not be avoided when pH was below pHIEP of TiO2=6.3. In this condition, electrostatic adsorption occurred between the anionic substrate molecules and positively charged TiO2 surface. The adsorbed substrate anion occupied most active sites of TiO2 on the mesh electrode surface and significantly reduced the performance efficiency of photo-oxidation, when the TiO2 mesh electrode was reused. The experiment demonstrated that TCP adsorption on the mesh electrode could be significantly eliminated, when pH of TCP solution was adjusted to above 7. When raising pH in TCP photodegradation eliminated substrate adsorption, it was confirmed that PC oxidation with application of a potential bias could enhance the photo-oxidation rate and a repeatable photo-oxidation rate could be maintained when the same mesh electrode was reused in its following tests.