WITHDRAWN: A three-step electrochemical method designed for the production of nickel- and platinum-doped TiO(2) multi-nanoporous thin-film electrodes: An application in the degradation of acid red G.
This study reports on the production of the platinum- and nickel-doped anatase multi-nanoporous thin-film electrodes. These doped electrodes were fabricated from titanium plates by a three-step electrochemical method, which comprises (i) anodization of titanium plates in oxalic acid electrolyte, (ii) electrodeposition of transition metals on the oxide produced, and finally, (iii) re-anodization of the whole assembly in sulfuric acid electrolyte, which leads to the production of stable transition metal-doped TiO(2) thin-film electrodes. Some investigations concerning the degradation of a non-biodegradable azo dye (acid red G) in the presence of these electrodes irradiated by artificial UV-light were performed. The degradation of about 92% was obtained at pH 2.1 after 5.0h illumination of acid red G 23ppm using TiO(2) electrode while only about 50% degradation was observed at pH 12.2. The photocatalytic degradation of the dye was strongly favored in acidic solutions. A simplified kinetic study of the degradation of the dye by UV/TiO(2) electrodes system was carried out and the adsorption equilibrium constant (K(ads)), the pseudo-first order rate constant (k), and the degradation rate (r) were evaluated for different electrodes. The ratios of the degradation rates of acid red G 23ppm in respect with the undoped TiO(2) were 2.63, 1.00, and 0.58 using Pt-TiO(2), TiO(2), and Ni-TiO(2), respectively. The photocatalytic efficiency was remarkably enhanced in samples doped with Pt(4+) while the incorporation of Ni(2+) was detrimental to this process. The efficiency of the metal-doped TiO(2) electrodes was explained on the basis of the electroaffinity and the electron work function. The COD removal of about 86.3% was obtained at pH 2.1 after 3.0h illumination of acid red G 7.5ppm using Pt-TiO(2) electrode. The experimental results showed that the reduction of COD removal decreased with increasing pH and the augmentation of the initial concentration of the azo dye.
Gracien
Ekoko Bakambo
EB
Institute of Materials, Shanghai University, 149 Yanchang Road, Shanghai 200072, People's Republic of China.
Shen
Jianian
J
Sun
Xianrong
X
Liu
Dong
D
Li
Moucheng
M