TiO2 photocatalytic degradation and detoxification of cylindrospermopsin

• Kinetics and products of TiO2 photocatalysis of cylindrospermopsin (CYN).
• Hydroxyl radical mediated oxidation of CYN.
• Hydroxylation and degradation of the uracil ring during TiO2 photocatalysis.
• Detoxification of CYN by TiO2 photocatalysis.

Cylindrospermopsin (CYN), a problematic potent cyanotoxin, is produced during harmful algal blooms and its presence in fresh water lakes and rivers is a threat to human health. UV TiO2 photocatalysis leads to the rapid degradation of CYN following pseudo-first-order kinetics. The pseudo-first-order rate constants (k) are strongly dependent on the reaction conditions, including the initial CYN and TiO2 concentrations, light intensity and solution pH. The observed faster degradation under acidic conditions may be due to the enhanced electrostatic attraction between the positive TiO2 surface and the anionic sulfate group in CYN. The degradation is proportional to the light intensity under our experimental conditions. The roles of reactive species, OH, 1O2, e−cb and h+vb were studied by adding the specific scavengers and the results indicate that OH plays a critical role in UV TiO2 photocatalysis of CYN. Detailed product studies using liquid chromatography mass spectrometry (LC/MS) indicate OH mediated degradation pathways predominantly occur via oxidation of the uracil ring in CYN, leading to hydroxylation and ring opened products. ELISA results demonstrate that TiO2 photocatalysis leads to a significant decrease in the biological activity of CYN as a function of treatment time. Our results indicate TiO2 photocatalysis may be applicable for the degradation of CYN and uracil based compounds.