Detoxification of microcystins (cyanobacterial hepatotoxins) using TiO2 photocatalytic oxidation

TiO2 photocatalysis has been used to destroy microcystin-LR in aqueous solu tion. The destruction of this toxin was monitored by HPLC, and the disappea rance was accompanied by the appearance of seven UV detectable compounds. S pectral analysis revealed that some of these compounds retained spectra sim ilar to the parent compound suggesting that the Adda moiety, thought to be responsible for the characteristic spectrum, remained intact whereas the sp ectra of some of the other products was more radically altered. Six of the seven observed reaction products did not appear to undergo further degradat ion during prolonged photocatalysis (100 min). The degree to which microcys tin-LR was mineralized by photocatalytic oxidation was determined. Results indicated that less than 10% mineralization occurred. Mass spectral analysi s of the photocatalyzed microcystin-LR allowed tentative characterization o f the reaction process and products. Reduction in toxicity due to the photo catalytic oxidation was evaluated using an invertebrate bioassay, which dem onstrated that the disappearance of microcystin-LR was paralleled by a redu ction in toxicity. These findings suggest that photocatalytic destruction o f microcystins may be a suitable method for the removal of these potentiall y hazardous compounds from drinking water.