Photocatalytic degradation of microcystins-LR in source water using TiO2 nanotubes
DENG Yi-rong1,2,3,4, ZHAO Lu5, SU Ya-ling3, ZHONG Yin1, PENG Ping-an1, XIAO Rong-bo2
1. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;
2. Guangdong Key Laboratory of Contaminated Environmental Management and Remediation, Guangdong Provincial Academy of Environmental Science, Guangzhou 510045, China;
3. State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China;
4. University of Chinese Academy of Sciences, Beijing 100049, China;
5. Guangzhou Research Institute of Environmental Protection, Guangzhou 510620, China
In this work, TiO2 nanotubes was fabricated using anodization method with oxalic acid and NH4F solution. TiO2 nanotubes were used to photocatalytic degradation of microsytins-LR. The results showed that the morphology was the most highly ordered under the optimum anodic voltage of 20V, electrolyte composition of 1/12mol/L H2C2O4·2H2O+0.5wt%NH4F and anodization time of 1~2h. The pore size of nanotubes was around 50nm, and the length was 250~600nm. After annealing at the temperature of 500~600℃, TiO2 nanotubes showed a high photocatalytic ability for MC-LR under pH 3.5and 8. The photocatalytic reactions of MC-LR fit well with the pseudo-first order kinetics. We infer the possible degradation pathways of MC-LR involve not only the attack by hydroxyl radicals for the conjugated double bond and methoxy group in the Adda chain, as well as the conjugated system in the Mdha amino acid, but also the hydrolysis of peptide bonds.
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