Impact of the morphological properties of thin TiO2 photocatalytic films on the detoxification of water contaminated with the cyanotoxin, microcystin-LR

This study investigated the use of thin transparent TiO2 photocatalytic films, prepared with novel sol-gel methods containing surfactants as templating materials, for the degradation of the cyanotoxin, microcystin-LR (MC-LR). MC-LR is an emerging contaminant from the Contaminant Candidate Lists (CCLs 1-3) of the USEPA. The effects of UV-A radiation, solution pH, initial toxin concentration, coated surface area of the TiO2 films and their structural properties (porosity, crystallinity and thickness) on the degradation rate of MC-LR were investigated. Photolysis did not occur with UV-A radiation. Acidic pH was more efficient for the degradation of MC-LR due to toxin interaction with the catalyst surface and increased adsorption into the porous films. The degradation profiles of the toxin at different initial concentrations were fitted with pseudo-first order kinetics. Films prepared with three coatings (0.3 mu m thickness) had the best performance at acidic and neutral pH, while the exclusion of surfactant from the preparation method resulted in non-porous films with decreased performance. The parameter that mostly affected the degradation rate was the solution pH. The toxicity of the treated samples, evaluated by an in-house protein phosphatase 1 assay, indicated that treatment with the TiO2 photocatalytic films indeed resulted in complete removal of MC-LR's toxicity. (C) 2009 Elsevier B.V. All rights reserved.