Efficiency of UV Treatment with and without the photocatalyst titanium dioxide for the degradation of the cyanotoxin cylindrospermopsin

Abstract

Cylindrospermopsin is a potent hepatotoxin, produced by several cyanobacteria including Cylindrospermopsis raciborskii, a species commonly found in water supplies in Queensland, Australia. This study focussed on an assessment of the effectiveness of ultra violet (UV) irradiation as a water treatment procedure for the degradation of cylindrospermopsin. Enhancement of UV treatment with the addition of the photocatalyst titanium dioxide was also examined. Results indicate that UV irradiation (>4750 μW cm) degrades cylindrospermopsin over an initial toxin concentration range of 50-350 μg L. In addition, there was an influence on the degradation rate from solution pH (4, 7 and 9), but less so from solution temperature (19, 28 and 35°C). Degradation was a first order kinetic relationship and the calculated half-life of cylindrospermopsin under UV irradiation (unbuffered, pH 6.5, 22 ± 2°C) was 14 ± 2 minutes. The addition of titanium dioxide (0.1 g L) to samples greatly increased the degradation rate to produce a calculated half-life of 2.8 ± 1 minutes