Simulation and comparative study on the oxidation kinetics of atrazine by UV/H2O2, and

• Published in: Water research (Oxford) 2015-09, Vol.80, p.99-108
• Main Authors: Luo, Congwei, Ma, Jun, Jiang, Jin, Liu, Yongze, Song, Yang, Yang, Yi, Guan, Yinghong, Wu, Daoji
• Format: Article
• Language: English
• Subjects: Atrazine; Bicarbonates; Degradation; Mathematical models; Oxidants; Oxidation; Reaction kinetics; Scavenging
• ISSN: 0043-1354
• DOI: 10.1016/j.watres.2015.05.019

This study comparatively investigated atrazine (ATZ) degradation by irradiation at the wavelength of 254 nm in the presence of peroxides including hydrogen peroxide (H2O2), peroxymonosulfate (), and persulfate () at various initial ATZ concentrations and oxidant dosages. The effects of water matrix, such as carbonate/bicarbonate (), chloride ions (Cl-), and natural organic matter (NOM), were evaluated on these three advanced oxidation processes. A simple steady-state kinetic model was developed based on the initial rates of ATZ destruction, which could well describe the apparent pseudo-first-order rate constants (k app, s-1) of ATZ degradation in these three processes. The specific roles of reactive species (i.e., HO[radicaldot], , , and ) under various experimental conditions were quantitatively evaluated based on their steady-state concentrations obtained from this model. Modeling results showed that the steady-state concentrations of HO[radicaldot] and decreased with the increase of concentration, and the relative contribution of HO[radicaldot] to ATZ degradation significantly decreased in UV/H2O2 and systems. On the other hand, the scavenging effect of on the relative contribution of to ATZ degradation was lower than that on HO[radicaldot]. The presence of Cl- (0.5-10 mM) significantly scavenged but had slightly scavenging effect on HO[radicaldot] at the present experimental pH, resulting in greater decrease of k app in the than UV/H2O2 and systems. Higher levels of were generated in the than those in the UV/H2O2 and systems at the same Cl- concentrations. NOM significantly decreased k app due to its effects of competitive UV absorption and radical scavenging with the latter one being dominant. These results improve the understanding of the effects of water constituents for ATZ degradation in the UV-based oxidation processes.