PD (II) Catalyzed Chlorination of Levofloxacin during Water Treatment: Kinetics and Mechanism: Investigation of Pd (II) ion catalyzed chlorination of levofloxacin during water treatment

Abstract

The kinetics and mechanism of the Pd (II) ion catalyzed reaction of levofloxacin (LFC) by free available chlorine (FAC) during water chlorination processes was investigated for the first time between the pH values 4.0 and 9.0. The pH dependent second order rate constants were found to decrease with increase in pH. (e.g. Apparent second order rate constant; k”app = 105.45 dm3 mol-1 s-1 at pH 4.0 and k”app = 16.93 dm3 mol-1 s-1 at pH 9.0 and at 25 oC). The reaction rates revealed that Pd (II) catalyzed reaction was faster than the uncatalyzed reaction. The products of the reaction were determined by Liquid chromatography and high resolution mass spectrometry. The reaction proceeds via formation of intermediate complex between Pd (II) ion and levofloxacin, then HOCl reacts with the complex to form chlorinated product. The effect of catalyst, effect of initially added product, effect of dielectric constant and effect of ionic strength on the rate of reaction was also studied. The effect of temperature on the rate of the reaction was studied at four different temperatures and rate constants were found to increase with increase in temperature and the thermodynamic activation parameters Ea, ΔH#, ΔS# and ΔG# were evaluated for the reaction and discussed.