Photocatalytic degradation of microcystin-LR using TiO2 nanotubes under irradiation with UV and natural sunlight

In order to investigate the catalytic performance of anodic TiO2 nanotubes and their practical application in the treatment of re- fractory microcystins （MCs） in natural-water samples, TiO2 nanotubes of diameter of 50-80 nm were fabricated by anodization in C2H204 2H20 containing NH4F. Under irradiation with natural sunlight, MC-LR was totally degraded after 1 d using the anodic TiO2 nanotubes. In contrast, the removal efficiency without TiO2 nanotubes was as low as 47.7% within 20 d. In addition, a mix- ture of anatase and rutile TiO2 gave higher photocatalytic activity than the single phase did. The pH also influenced the adsorption capacity of the TiO2 nanotubes. The order of MC-LR degradation efficiencies at different pH values was 3.5 〉 8.0 〉 10.0. After five repeated experiments on the degradation of MC-LR for 7 b, the degradation efficiency was still stable.