Destruction of cyanobacterial toxin cylindrospermopsin by hydroxyl radicals and sulfate radicals using UV-254nm activation of hydrogen peroxide, persulfate and peroxymonosulfate

Abstract

Abstract With increasing worldwide incidence of toxic cyanobacterial blooms in bodies of water, cylindrospermopsin (CYN) has become a significant concern to public health and water management officials. In this study, the removal of CYN by UV-254 nm-mediated advanced oxidation processes (AOPs) was evaluated. Cylindrospermopsin, at an initial concentration of 1 μM, was significantly degraded, 75% at a UV fluence of 80 mJ cm−2, 100% at 20 mJ cm−2, and 100% at 40 mJ cm−2, by UV/H2O2, UV/S2O82−, and UV/HSO5− processes, respectively, at an initial oxidant dose of 1 mM. The calculated second-order rate constants of CYN with hydroxyl radicals, k OH/CYN, was 5.1 × 109 M−1 s−1 and with sulfate radicals, k SO 4 − / CYN , was 4.5 × 109 M−1 s−1. The observed pseudo-first-order reaction rate constant increased linearly with increasing initial oxidant concentration. The destruction of CYN by both radicals was inhibited by radical scavengers, such as natural organic matter (NOM) and alkalinity. The presence of transition metals in tap water samples appeared to enhance the treatment efficiency of CYN by UV/HSO5−. The ICP-MS analysis of the metals in the water samples, revealed copper residual of 40.6 ± 3.3 μg L−1 in tap water, and 13.6 and 8.1 μg L−1 in two natural water samples. Results of this study suggest that the presence of transition metals in natural water sources could be an important factor in AOPs. This study is a new and feasible approach to remove CYN as well as other organic contaminants from water resources.