Advanced oxidation of atrazine in water—I. Ozonation

Abstract

The ozonation of atrazine in water has been studied under different conditions of ozone partial pressure, pH, temperature and presence of hydroxyl radical scavengers. The process mainly develops through radical reactions, even at pH 2, probably due to the presence of traces of impurities in the starting material. The rate constant of the direct reaction between ozone and atrazine at pH 2 has been determined and expressed as a function of temperature. Thus, at 20°C the rate constant was found to be 4.5 M −1 s −1 the energy of activation being 18.8 kJ · mol −1. A model formed by mol balance equations of atrazine and ozone, the latter in the liquid and gas phases, with the ozone decomposition rate based on the Staehelin and Hoigné mechanism allowed the determination of the concentrations of these species at different experimental conditions. The aqueous solution of atrazine is characterized by a hydroxyl radical initiating rate factor which accounts for other radical reactions not included in the basic ozone decomposition mechanism. With this factor deviations between experimental and calculated concentrations of atrazine are less than ± 15% in most of the cases.