Heat-activated persulfate oxidation of atrazine: Implications for remediation of groundwater contaminated by herbicides

Contamination of herbicides such as atrazine (ATZ) poses a significant threat to human health and aquatic ecosystem. In this study, we demonstrated that heat-activated persulfate could effectively degrade ATZ in water. Complete disappearance of 50 mu M ATZ could be obtained after 2 h reaction in the presence of 1 mM persulfate under 60 degrees C. Increasing the initial persulfate concentration or temperature significantly enhanced the degradation efficiency. Natural organic matter (NOM) decreased the degradation rate, but complete removal of ATZ could still be obtained. The presence of chloride (Cl-) and bicarbonate (HCO3-) had little effects on ATZ degradation at lower concentration (e.g., 5 mM). However, inhibitory effects were observed when concentrations of Cl- and HCO3- increased (e.g., 100 mM). Radical scavenging test revealed that sulfate radical (SO4 center dot-) was the predominant radical species at acidic to neutral pH, while hydroxyl radical (HO center dot) was predominant at basic pH. Eight intermediates and products were identified by applying solid phase extraction and liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) techniques. Transformation pathways including dealkylation, alkyl chain oxidation, and dechlorination-hydroxylation were proposed, and the underlying mechanisms for each pathway were systematically analyzed. (C) 2014 Elsevier B.V. All rights reserved.