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The degradation of atrazine was investigated in aqueous solution by gamma-ray irradiation. 8.11 μM initial atrazine concentration could be completely removed in N₂ 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 N₂ gases, respectively. The relative contributions of hydrated electron, hydroxyl radical and hydrogen radical toward atrazine degradation were determined as ratio of observed dose constant (kobs) and found to be 5: 3: 1 for keaq(-): k·OH: kH·, 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., (Copyright © 2014 Elsevier B.V. All rights reserved.)

This study reports the radiation-induced degradation of an extensively used carcinogenic, endocrine disrupting and persistent herbicide, atrazine, in aqueous solution. The atrazine degradation rate was directly proportional whereas the dose constant was inversely proportional to the irradiation dose rate and initial atrazine concentration. The second-order rate constant of atrazine with e aq − and H were found to be 3.70 × 10 9 and 4.84 × 10 8 M −1 s −1 , respectively. Humic acid has synergistic whereas hydrogen peroxide and chloroform have an inhibitory impact on atrazine degradation. Atrazine degradation was reduced in the presence of 1 mM of each of NO 3 − , NO 2 − , Br − , SO 4 2− , HCO 3 − and CO 3 2− due to their competition for reactive radicals with atrazine. The attack of e aq − and OH on atrazine successfully mineralized the organic chlorine and nitrogen to chloride, nitrate and ammonium ions, in addition to the formation of acetate ions from carbon atoms of side chains. Potential detoxification of atrazine solution could be revealed from 83% loss of chloride ion at an absorbed dose of 4000 Gy. The findings of this study suggested that atrazine can efficiently be removed from water by gamma-ray irradiation even in the presence of organic and inorganic radical scavengers commonly found in natural water. [ABSTRACT FROM AUTHOR]

Conventional titanium dioxide (TiO2) materials can be activated only by ultraviolet (UV) light, which is only 4-5% of the whole solar spectrum. As a result, visible light (vis)-active TiO2-based photocatalysts have recently received significant attention in the field of TiO2 photocatalytic treatment and purification of water and air. This study reports the preparation of UV-visible light-active phosphorous (P)-doped, fluorine (F)-doped, and PF-co-doped anatase TiO2 nanoparticles via an innovative sol-gel method. Prepared nanoparticles were characterized by UV-vis diffuse reflectance spectroscopy, X-ray diffraction analysis, Raman spectroscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy (FTIR), and porosimetry analysis. Synthesized materials exhibited improved structural properties, including high surface area, small crystallite size, reduced band gap energy, mesoporous structure, and high porosity. Due to doping with P and F, light absorption of TiO2 in the visible light region was efficiently enhanced with effective band gap energy of 2.70 eV. Brunauer-Emmett-Teller (BET) surface area for PF-co-doped, P-doped, F-doped, and reference TiO2 nanoparticles was 212.0, 175.0, 88.8, and 79.7 m2/g, respectively. PF-co-doped TiO2 showed the highest photocatalytic degradation of atrazine, which could be attributed to the beneficial effects including small crystallite size, high BET surface area, and light absorption in UV-visible region, induced by co-doping of TiO2 with P and F. Finally, reaction intermediates were determined, which confirms the photocatalytic degradation of atrazine using the synthesized catalysts under UV-visible light illumination. [ABSTRACT FROM AUTHOR]

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 and SO 4 − generated from the activation of peroxides, i.e., persulfate (S 2 O 8 2− ), peroxymonosulfate (HSO 5 − ) and hydrogen peroxide (H 2 O 2 ), by UV-254 nm radiation in the presence or absence of Fe 2+ . Quantum yields of DEA and DIA were independent of pH (3.0–11.0). The higher quantum yield of reactive radicals from UV/S 2 O 8 2− , i.e., 1.8 compared to 1.04 for UV/HSO 5 − and 1.0 for UV/H 2 O 2 , resulted in greater efficiency of UV/S 2 O 8 2− for both DEA and DIA degradation. The second-order rate constants of DEA and DIA with SO 4 − were calculated to be (6.42 ± 0.12) × 10 8 and (1.70 ± 0.30) × 10 9 M −1 s −1 , and that with OH were (1.14 ± 0.09) × 10 9 and (2.22 ± 0.44) × 10 9 M −1 s −1 , respectively, suggesting a strong impact of side chains toward radical reactions. Fe 2+ 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/S 2 O 8 2− . 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 and SO 4 − based-AOPs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Degradation of atrazine was investigated in UV, UV/H2O2, UV/HSO5 − and UV/S2O8 2− AOPs. [•] UV/S2O8 2− process was found to be more efficient as well as more economical. [•] The pH affected UV/S2O8 2− but had no significant influence on UV, UV/H2O2 and UV/HSO5 −. [•] Second order rate constants of atrazine with SO4 − and OH were found to be comparable. [•] Degradation mechanism was investigated by GC–MS and LC–MS/MS analysis. [ABSTRACT FROM AUTHOR]

Abstract: The degradation of atrazine, a widely used endocrine disrupting, carcinogenic and persistent herbicide, was investigated by photo-Fenton and photo-Fenton-like advanced oxidation technologies (AOTs): UV/H2O2/Fe2+, UV//Fe2+ and UV//Fe2+. The study was carried out at two pH value conditions, i.e., pH 3.0 and pH 5.8. At pH 3.0, UV//Fe2+ was found to be the most efficient technology whereas UV//Fe2+ was observed to be the most effective at pH 5.8. The degradation of atrazine followed pseudo-first-order reaction with the highest observed rate constant of 2.00×10−2 cm2/mJ in UV//Fe2+ system at the initial concentrations of 4.64μM atrazine, 46.4μM (PMS) and 35.81μM Fe2+. The UV fluence required for the complete removal of 4.64μM atrazine at initially 92.80μM of oxidant and 8.95μM of Fe2+ concentrations at pH 3.0 was found to be 480, 720 and 960mJ/cm2 in UV//Fe2+, UV//Fe2+ and UV/H2O2/Fe2+ systems, respectively. Humic and fulvic acids were found to negatively impact the degradation of atrazine. The removal of TOC was not significant unless a high UV fluence was applied. At an initial concentration of 18.56μM atrazine, 1856.00μM oxidant and 17.91μM Fe2+, a 62.94%, 47.10% and 44.09% decrease in TOC was achieved at a UV fluence of 6000mJ/cm2 in UV/PS/Fe2+, UV/PMS/Fe2+ and UV/H2O2/Fe2+ systems, respectively. Nevertheless, it is suggested in this study that photo-Fenton and photo-Fenton-like technologies are capable of removing atrazine from water efficiently. [Copyright &y& Elsevier]