Oxidative degradation of triazine- and sulfonylurea-based herbicides using Fe(VI): The case study of atrazine and iodosulfuron with kinetics and degradation products

The occurrence of common herbicides (Atrazine, ATZ and lodosulfuron, IDS), in waters presents potential risk to human and ecological health. The oxidative degradation of ATZ and IDS by ferrate(VI) (FeO42-)-O-VI, Fe(VI) is studied at different pH levels where kinetically observed second-order rate constants (kapp, M-1 s(-1)) decreased with increase in pH from 6.0 to 9.0. The determination of the rate constants for the Fe(VI) species, HFeO4- and FeO42-, with the herbicides using acid-base equilibria of Fe(VI) suggested that the HFeOZ species was largely responsible for the pH dependence behavior of kapp. The title herbicides degraded >90% within 10 min using excess weighted amounts of Fe(VI) over IDS (2:1) ATZ (20:1) and in the pH range of 6.0-9.0. Comparatively, degradations of ATZ and IDS by Mn(VII) were 70% and 40% under same conditions; - showing a superior efficiency of ferrate(VI) in degradation of toxic herbicides. The oxidized products of ATZ and IDS by Fe(VI) at a neutral pH were examined by liquid chromatography-tandem mass spectrometry (LC/MS/MS) analysis, which indicated that Fe(VI) attacked on the sulfonamide and alkyl chain moieties of ATZ and IDS, respectively. (C) 2015 Elsevier B.V. All rights reserved.