Degradation kinetics and mechanism of desethyl-atrazine and desisopropyl-atrazine in water with •OH and SO4•- based-AOPs

Desethyl-atrazine (DEA) and desisopropyl-atrazine (DIA) are the two major degradation by-products of atrazine (a suspected human carcinogen and endocrine disrupting herbicide), and show an equal toxicity to their parent compound. This study investigated the degradation of DEA and DIA with (OH)-O-center dot and SO4 center dot- generated from the activation of peroxides, i.e., persulfate (S2O82-), peroxymonosulfate (HSO5-) and hydrogen peroxide (H2O2), by UV-254 nm radiation in the presence or absence of Fe2+. Quantum yields of DEA and DIA were independent of pH (3.0-11.0). The higher quantum yield of reactive radicals from UV/S2O82-, i.e., 1.8 compared to 1.04 for UV/HSO5- and 1.0 for UV/H2O2, resulted in greater efficiency of UV/S2O82- for both DEA and DIA degradation. The second-order rate constants of DEA and DIA with SO4 center dot- were calculated to be (6.42 +/- 0.12) x 10(8) and (1.70 +/- 0.30) x 10(9) M-1 s(-1), and that with OH were (1.14 +/- 0.09) x 10(9) and (2.22 +/- 0.44) x 109 M-1 s(-1), respectively, suggesting a strong impact of side chains toward radical reactions. Fe2+ promoted slightly the activation of the examined peroxides at pH 7.4. Presence of organic matter and alkalinity in field water samples negatively influenced the efficiency of UV/S2O82-. Based on the identified degradation by-products by GC-MS, potential degradation pathways were proposed for both compounds. The results obtained suggested that DEA and DIA can be efficiently removed from the contaminated water by (OH)-O-center dot and SO4 center dot- based-AOPs. (C) 2017 Elsevier B.V. All rights reserved.