Photocatalytic degradation of the cyanotoxin cylindrospermopsin, using titanium dioxide and UV irradiation

Cylindrospermopsis raciborskii produces the cyanotoxin cylindrospermopsin, which is commonly found in SouthEast Queensland water reservoirs, and has b een responsible for the closure of these reservoirs as a source of drinking water in recent times. Thus, alternative more effective treatment methods need to be investigated for the removal of toxins such as cylindrospermopsi n. This study examined the effectiveness of two brands of titanium dioxide under UV photolysis for the degradation of cylindrospermopsin. Results indi cate that titanium dioxide is an efficient photocatalyst for cylindrospermo psin degradation. The titanium dioxide (TiO2), brand Degussa P-25 was found to be more efficient than the alternate brand Hombikat UV-100. There was a n influence from solution pH (4, 7, and 9) with both brands of titanium dio xide, with high pH resulting in the best degradation rate. Importantly, the re was no adsorption of cylindrospermopsin to titanium dioxide particles as seen with other cyanotoxins, which would adversely influence the degradati on rate. Degradation rates were not influenced by temperature (19-34 degree sC) when P-25 was the source of TiO2, some temperature influence was observ ed with UV-100. Dissolved organic carbon concentration will reduce the effi ciency of titanium dioxide for cylindrospermopsin degradation, however the presence of other inorganic matter in natural waters greatly assists the ph otocatalytic process. With minimal potentially toxic by-product formation e xpected with this treatment, and the effective degradation of cylindrosperm opsin, titanium dioxide UV photolysis is a promising speculative alternativ e water treatment method. (C) 2001 Elsevier Science Ltd. All rights reserve d.