Abstract
Fipronil, a pesticide gaining wide usage, was oxidized with common drinking water treatment disinfectants and oxidants; with a degradate identified using liquid chromatography-mass spectrometry. Oxidants investigated were free chlorine (HOCl/OCl-), monochloramine (ClNH2), chlorine dioxide (ClO2), and permanganate (MnO4-) at pH 6.6 and 8.6. Free chlorine, chlorine dioxide, and permanganate were reactive with fipronil to various degrees, whereas monochloramine was only marginally reactive. No oxidation products were observed for free chlorine, monochloramine, or chlorine dioxide. Oxidation by permanganate produced an identifiable degradate, fipronil sulfone, which was recalcitrant to further oxidation by permanganate. Fipronil sulfone could, however, be further degraded by free chlorine. Under typical conditions of water treatment, free chlorine was an effective oxidant for fipronil and fipronil sulfone, achieving partial removal at typical conditions. pH effects were observed for free chlorine, chlorine dioxide, and permanganate with more rapid oxidation occurring at pH 8.6 than at pH 6.6.