- Atrazine photolysis: Mechanistic investigations of direct and nitrate- mediated hydroxy radical processes and the influence of dissolved organic carbon from the Chesapeake Bay
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Direct and nitrate-mediated hydroxy radical photoprocesses were examined with respect to atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) transformation. Irradiation (λ > 290 nm) of aqueous solutions of atrazine in the presence of nitrate, which generates ·OH, yielded 20% of 6-amino-2- chloro-4-isopropylamino-s-triazine (CIAT), 10% of 6-amino-2-chloro-4- ethylamino-s-triazine (CEAT), 6% of 4-acetamide-2-chloro-6-isopropylamino-s- triazine (CDIT), 3% of 4-acetamide-2-chloro-6-ethylamino-s-triazine (CDET), 16% of chlorodiamino-s-triazine (CAAT), and 3% of hydroxy atrazine (OIET, 4- ethylamino-6-isopropylamino-2-hydroxy-s-triazine) at 87% atrazine conversion. Direct photolysis of atrazine was much slower and at 23% atrazine conversion gave rise to 14% OIET and ca. 9% of chloroalkyloxidized or chlorodealkylated compounds with the ratio of the reaction rate constants equal to 0.14 (κ(direct)/κ(indirect)). Results also suggest that DIET was not the product of a hydroxy radical process. The efficiency of the hydroxy radical process decreased more than 85%, with increasing DOC obtained from the surface layer of the Chesapeake Bay. However, only a slight decrease (15%) in efficiency was observed for direct photolysis, suggesting that in the presence of surface layer DOC direct photolysis may become more important relative to the ·OH processes.
- Torrents, Alba,Anderson, Brent G.,Bilboulian, Susanna,Johnson, W. Edward,Hapeman, Cathleen J.
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- Kinetic and mechanistic aspects of the direct photodegradation of atrazine, atraton, ametryn and 2-hydroxyatrazine by 254 nm light in aqueous solution
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Atrazine (1), Atraton (2) and Ametryn (3) are photodegraded upon 254 nm irradiation, yielding 2-OH-atrazine (4) as a photoproduct. Dealkylation products are also generated, and 4-ethylamino-6-isopropylamino-(1,3,5)-triazine was also found as a photoproduct of 3. The main photoreaction is proposed to be an addition-elimination, yielding 4, which subsequently photodegrades. The ease of photodegradation depends on the electron availability at position C-2, the observed order of photoreactivity being 1 > 3 > 4 > 2. Copyright
- Azenha,Burrows,Canle L,Coimbra,Fernandez,Garcia,Peiteado,Santaballa
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- The process of atrazine degradation, its mechanism, and the formation of metabolites using UV and UV/MW photolysis
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The photolytic degradationmechanism of atrazine using a UV reactor andUV/MW (electrodeless discharge lamp (Hg-EDL)) was investigated. After 120?s of UV photolysis partial degradation of atrazine had been observed and a subsequent formation of degradation products of atrazine-2-hydroxy, therefore, defining the path of atrazine degradation through UV photolysis. This system after 1200?s of exposure to UV radiation had not reached full degradation of atrazine, and its metabolite (atrazine-2-hydroxy), was the main by-product obtained for the process. When performing photolysis through the UV/Microwave combined methodcomplete atrazine degradation was obtained within a 5?s interval, besides the formation of five (5) degradation products, which are HAT, DEAT, DIAT, DEHAT and DIHAT. Therefore, defining the path of the photolytic degradation process through the UV/Microwave combined method. The total degradation of its metabolite (HAT) was observed for the period of 120?s of exposure to UV/MW radiation, and after that time there had been no signcorresponding to the respective compounds. The tests with the isolated microwave radiation were not efficient in the degradation of the atrazine and, therefore, the respective isolated energy is not applicable.The control of atrazine degradation and consequent formation of metabolites were accompanied by a high-performance liquid chromatography with a UV/Vis detector.
- Moreira, Ailton. J.,Borges, Aline C.,Gouvea, Luis F.C.,MacLeod, Tatiana C.O.,Freschi, Gian P.G.
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p. 160 - 167
(2017/08/09)
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- Efficient removal of atrazine in water with a Fe3O4/MWCNTs nanocomposite as a heterogeneous Fenton-like catalyst
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Fe3O4 and multi-walled carbon nanotube hybrid materials (Fe3O4/MWCNTs) were synthesized by a coprecipitation combined hydrothermal method. The nanocomposites were applied for adsorption and degradation of atrazine (ATZ) in the presence of H2O2. The obtained catalysts were characterized by TEM, XRD, BET, XPS and Raman spectroscopy. The effects of solution pH, catalysts dosage, H2O2 concentration and iron leaching on the degradation of ATZ were investigated. Fe3O4/MWCNTs showed a higher utilization efficiency of H2O2, higher ability of adsorption for ATZ and higher degradation efficiency of ATZ than Fe3O4 nanoparticles in the batch degradation experiment. The degradation efficiency increased with the solution pH decreasing from 8.0 to 3.0. The catalytic results showed that Fe3O4/MWCNTs presented good performance for the degradation of ATZ, achieving 81.4% decomposition of ATZ after 120 min at reaction conditions of H2O2 concentration 3.0 mmol L-1, catalysts dosage 0.1 g L-1, ATZ concentration 10.0 mg L-1, pH 5.0 and T 30 °C. Three degradation products (desethylatrazine, desisopropylatrazine, and 2-hydroxyatrazine) were detected during a heterogeneous Fenton reaction in solution. The stability, and reusability of Fe3O4/MWCNTs for ATZ degradation were also investigated.
- Yu, Lian,Yang, Xiaofang,Ye, Yushi,Wang, Dongsheng
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p. 46059 - 46066
(2015/06/08)
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- Wet peroxide degradation of atrazine
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The high temperature (150-200 °C), high pressure (3.0-6.0 MPa) degradation of atrazine in aqueous solution has been studied. Under these extreme conditions atrazine steadily hydrolyses in the absence of oxidising agents. Additionally, oxygen partial pressure has been shown not to affect atrazine degradation rates. In no case mineralisation of the parent compound was observed. The addition of the free radical generator hydrogen peroxide to the reaction media significantly enhanced the depletion rate of atrazine. Moreover, partial mineralisation of the organics was observed when hydrogen peroxide was used. Again, oxygen presence did not influence the efficiency of the promoted reaction. Consecutive injections of hydrogen peroxide throughout the reaction period brought the total carbon content conversion to a maximum of 65-70% after 40 min of treatment (suggesting the total conversion of atrazine to cyanuric acid). Toxicity of the effluent measured in a luminometer decreased from 93% up to 23% of inhibition percentage. The process has been simulated by means of a semi-empirical model.
- Rodriguez, Eva M.,Alvarez, Pedro M.,Rivas, F. Javier,Beltran, Fernando J.
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- Study of the mechanisms of the photodegradation of atrazine in the presence of two photocatalysts: TiO2 and Na4W10O32
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The mechanisms of the photodegradation of atrazine under direct photolysis and in the presence of two different photocatalysts, TiO2 and Na4W10O32, are investigated by the means of GC/MS, total radioactivity counting, HPLC and TLC analysis on 14C ring-labelled atrazine solutions. Integration of photo- and biodegradation processes is studied.
- Texier, Isabelle,Ouazzani, Jamal,Delaire, Jacques,Giannotti, Charles
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p. 3401 - 3412
(2007/10/03)
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