https://doi.org/10.1051/epjap/2014130453
Post-annealing treatment for Cu-TiO2 nanotubes and their use in photocatalytic methyl orange degradation and Pb(II) heavy metal ions removal
1
School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia Engineering Campus, 14300
Nibong Tebal, Seberang Perai Selatan, Pulau Pinang, Malaysia
2
Nanotechnology & Catalysis Research Centre (NANOCAT), 3rd Floor, Block A, Institute of Postgraduate Studies (IPS), University of Malaya, 50603
Kuala Lumpur, Malaysia
3
Department of Civil and Environmental Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata
940-2118, Japan
a e-mail: srimala@eng.usm.my
Received:
6
October
2013
Revised:
2
March
2014
Accepted:
4
March
2014
Published online:
11
July
2014
TiO2 nanotubes were synthesized via electrochemical anodization of Ti foil at 60 V for 1 h in a bath with electrolytes composed of ethylene glycol containing 5 wt.% of NH4F and 1 vol.% of H2O2. The incorporation of optimum Cu2+ ions (1.30 at.%) into TiO2 nanotubes were prepared by using wet impregnation method to improve their photocatalytic methyl orange degradation and Pb(II) heavy metal removal. The small Cu2+ ions were successfully diffused into lattice of TiO2 nanotubes by conducting post-annealing treatment at 400 °C for 4 h in argon atmosphere after wet impregnation. In this manner, optimum Cu2+ ions played a crucial role in suppressing the recombination of charge carriers by forming inter-band states (mismatch of the band energies) within the lattice of Cu-TiO2. The experimental results showed that a maximum of 80% methyl orange removal and 97.3% Pb(II) heavy metal removal at pH 11 under UV irradiation for 5 h. Besides, it was noticed that photocatalytic Pb(II) heavy metal removal was strong dependence on pH of the solution because of the amphoteric character of Cu-TiO2 in an aqueous medium.
© EDP Sciences, 2014
