Treatment of statin compounds by advanced oxidation processes: Kinetic considerations and destruction mechanisms

This study examined the use of advanced oxidation/reduction processes (AO/RPs) for the destruction of cholesterol lowering statin pharmaceuticals. AO/RPs which utilize the oxidizing hydroxyl radical ((OH)-O-center dot) and reducing aqueous electron (e(aq)(-)), to degrade chemical contaminants are alternatives to traditional water treatment methods, and are alternatives as water reuse becomes more generally implemented. Four major statin pharmaceuticals, fluvastatin, lovastatin, pravastatin and simvastatin, were studied, and the absolute bimolecular reaction rate constants with (OH)-O-center dot determined, (6.96 +/- 0.16) x 10(9), (2.92 +/- 0.06) x 10(9), (4.16 +/- 0.13) x 10(9), and (3.13 +/- 0.15) x 10(9) M-1 s(-1), and for e(aq)(-) (2.31 +/- 0.06) x 10(9), (0.45 +/- 0.01) x 10(9), (1.26 +/- 0.01) x 10(9), and (0.69 + 0.02) x 10(9) M-1 s(-1), respectively. To provide additional information on the radicals formed upon oxidation, transient spectra were measured and the overall reaction efficiency determined. Radical-based destruction mechanisms for destruction of the statins are proposed based on the LC-MS determination of the stable reaction by-products formed using Cs-137 gamma-irradiation of statin solutions. Knowing the reaction rates, reaction efficiencies and destruction mechanisms of these compounds is essential for the consideration of the use of advanced oxidation/reduction processes for the destruction of statins in aqueous systems. (C) 2010 Elsevier Ltd. All rights reserved.