Oxidation of Microcystin-LR via Activation of Peroxymonosulfate Using Ascorbic Acid: Kinetic Modeling and Toxicity Assessment

Advanced oxidation processes (AOPs) have been widely used for the destruction of organic contaminants in the aqueous phase. In this study, we introduce an AOP on activated peroxymonosulfate (PMS) by using ascorbic acid (H(2)A) to generate sulfate radicals (SO4 center dot-). Sulfate radicals, hydroxyl radicals (HO center dot), and ascorbyl radicals (A(center dot-)) were found using electron spin resonance (ESR). But we found A(center dot-) is negligible in the degradation of microcystin-LR (MCLR) due to its low reactivity. We developed a first-principles kinetic model to simulate the MCLR degradation and predict the radical concentrations. The MCLR degradation rate decreased with increasing pH. The scavenging effect of natural organic matter (NOM) on SO4 center dot- was relatively small compared to that for HO center dot. Considering both energy consumption and MCLR removal, the optimal H(2)A and PMS doses for H(2)A/PMS process determined at 1.0 x 10(-6) M and 1.6 x 10(-5) M, respectively. In addition, we determined the toxicity using the protein phosphatase 2A (PP2A) test and the results showed that MCLR was readily detoxified and its oxidation byproducts were not hepatotoxic. Overall, our work provides a new type of AOP and a promising, efficient, and environmental-friendly method for removing microcystins in algae-laden water.