Determination des constantes cinetiques de reaction des radicaux hydroxyles sur quelques s‐triazines

Publisher Website
Google Scholar
Abstract
Rate constants for the reaction of hydroxyl radicals with atrazine (kA), simazine (kg) and propazine (kp) have been measured in water, using competitive kinetic methods. Hydroxyl radicals were generated in the decomposition of ozone by hydroxide ions or by hydrogen peroxide (O3/H2O2). Assuming that hydroxyl radical reactions are predominant in the degradation of s‐triazines by O3 and by O3/H2O2, the data showed that the relative rate constants for the reaction of hydroxyl radicals with s‐triazines obtained from O 3 and from O3/H2O2 experiments carried out in phosphate buffered water (pH = 7.5; [HCO3 ‐] range: 0 to 20 mmol l‐1) or in drinking water and in batch and semi‐batch reactors were identical: kS/kA = 1.28 and kp/kA = 0.75 (20 ± 2°C). By mixing a reference substrate (chlorobenzene kCB = 4.3 109 1 mol‐1 s‐1) to the solution of s‐triazines, the following values for the reaction of hydroxyl radicals with atrazine, simazine and propazine could be determined from competitive experiments: kA = 1.7 109; kg = 2.1 109 and kp = 1.2 109 1 mol‐1 s‐1.