Role of eaq-, ○OH and H○ in radiolytic degradation of atrazine: A kinetic and mechanistic approach

The degradation of atrazine was investigated in aqueous solution by gamma-ray irradiation. 8.11 mu M initial atrazine concentration could be completely removed in N-2 saturated solution by applying 3500 Gy radiation dose at a dose rate of 296 Gy h(-1). Significant removal of atrazine (i.e., 39.4%) was observed at an absorbed dose of 1184 Gy in air saturated solution and the removal efficiency was promoted to 50.5 and 65.4% in the presence of N2O and N-2 gases, respectively. The relative contributions of hydrated electron, hydroxyl radical and hydrogen radical toward atrazine degradation were determined as ratio of observed dose constant (k(obs)) and found to be 5: 3: 1 for k(eaq)(-) : k center dot(OH): k(H)center dot respectively. The degradation efficiency of atrazine was 69.5, 55.6 and 37.3% at pH 12.1, 1.7 and 5.7, respectively. A degradation mechanism was proposed based on the identified degradation by-products by gas chromatography-mass spectrometry. Taking the relative contributions of oxidative and reductive species to atrazine degradation into account, reductive pathway proved to be a better approach for the radiolytic treatment of atrazine contaminated water. (C) 2014 Elsevier B.V. All rights reserved.