Adsorption and photodegradation of methylene blue using a bulk Ti material with porous titania layer prepared by chemical oxidation

• Porous titania network was produced on the Ti bulk disk via H2O2 oxidation method.
• After 90 min oxidation, a thicker titania layer (≈4 μm) with mixed amorphous–anatase phase was formed.
• The point of zero charge (PZC) of the prepared titania layer was estimated at pH 2.2.
• The prepared titania layer exhibited better methylene blue adsorption than P25 TiO2 nanoparticles.
• Rougher surface could achieve higher dye photodegradation efficiency.

In this study, a chemical oxidation method was adopted to prepare a porous titania network on Ti bulk for dye adsorption and photodegradation. The prepared titania layer was characterized by SEM, AFM, ATR-FTIR, XRD, and zeta potential. Using a longer oxidation time (90 min), a thicker titania layer (≈4 μm) with pHpzc (pH of the point of zero charge) of ca. 2.2 and larger fraction of anatase phase could be formed. The prepared titania layer exhibited a better adsorption capability for MB (methylene blue) at various pH values than the commercial P25 TiO2 nanoparticles (pHpzc = 6.0–6.8). Moreover, the effect of surface roughness on dye photodegradation was investigated. With UV irradiation, it took 6 h to completely decompose MB using the titania layer prepared from the polished surface, whereas only half time was required by that abraded via #240 sandpaper. An improved dye photodegradation efficiency was achieved by a rougher surface for providing a larger surface area.