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 refractory microcystins (MCs) in natural-water samples, TiO2 nanotubes of diameter of 50-80 nm were fabricated by anodization in C2H2O4 center dot 2H(2)O 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 mixture 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 h, the degradation efficiency was still stable.