Formation of self-organized ZrO2–TiO2 and ZrTiO4–TiO2 nanotube arrays by anodization of Ti–40Zr foil for Cr(VI) removal

Abstract

In this work, anodic oxidation of Ti-40 wt.% Zr alloy in EG/NH4F/H2O electrolyte was done to produce anodic self-aligned oxide nanotube arrays. The nanotubes were amorphous but upon annealing at 400° C they were crystallized into ZrO2–TiO2 nanotubes and ZrTiO4–TiO2 nanotubes at 600 °C. The nanotubes were used to reduce 60 ppm Cr(VI) ions under sunlight or UV irradiation. 100% removal of Cr(VI) was achieved on ZrTiO4–TiO2 nanotubes after 5 h of exposure to UV light but only 53% removal was obtained on ZrO2–TiO2 nanotubes. The higher photocatalytic activity of the ZrTiO4–TiO2 nanotubes can be related to the presence of the ZrTiO4 phase which has good acid–base properties as well as the junction formation between ZrTiO4 and TiO2 that can further enhance the reduction process.

Keywords

• Anodization
• Nanotubes
• Zirconium titanate
• Alloy
• Mixed oxide