Free radical destruction of β-blockers in aqueous solution

Many pharmaceutical compounds and metabolites are currently found in surface and ground waters which indicates their ineffective removal by conventional water treatment technologies. Advanced oxidation/reduction processes (AO/ RPs) are alternatives to traditional water treatment, which utilize free radical reactions to directly degrade chemical contaminants. This study reports the absolute rate constants for reaction of three beta-blockers (atenolol, metoprolol, and propranolol) with the two major, AO/RP radicals; the hydroxyl radical (center dot OH) and hydrated electron (e(-) aq). The bimolecular reaction rate constants for center dot OH are (7.05 +/- 0.27) x 10(9), (8.39 +/- 0.06) x 10(9), and (1.07 +/- 0.02) x 10(10), and for e(-) (aq) they are (5.91 +/- 0.21) x 10(8),(1.73 +/- 0.03) x 10(8), and (1.26 +/- 0.02) x 10(10), respectively. Transient spectra were observed for the intermediate radicals produced by hydroxyl radical reactions. In addition, preliminary degradation mechanisms and major products were elucidated using (CO)-C-60 gamma-irradiation and LC-MS. These data are required for both evaluating the potential use of AO/RPs for the destruction of these compounds and for studies of their fate and transport in surface waters where radical chemistry may be important in assessing their lifetime.