title: Theoretical study of the atrazine pesticide interaction with pyrophyllite and Ca(2+) -montmorillonite clay surfaces.
abstract: Atrazine, a pesticide belonging to the s-triazine family, is one of the most employed pesticides. Due to its negative impact on the environment, it has been forbidden within the European Union since 2004 but remains abundant in soils. For these reasons, its behavior in soils and water at the atomic scale is of great interest. In this article, we have investigated, using DFT, the adsorption of atrazine onto two different clay surfaces: a pyrophyllite clay and an Mg-substituted clay named montmorillonite, with Ca2+compensating cations on its surface. The calculations show that the atrazine molecule is physisorbed on the pyrophyllite surface, evidencing the necessity to use dispersion-corrected computational methods. The adsorption energies of atrazine on montmorillonite are two to three times larger than on pyrophyllite, depending on the adsorption pattern. The computed adsorption energy is of about -30 kcal mol-1for the two most stable montmorillonite-atrazine studied isomers. For these complexes, the large adsorption energy is related to the strong interaction between the chlorine atom of the atrazine molecule and one of the Ca2+compensating cations of the clay surface. The structural modifications induced by the adsorption are localized: for the surface, close to substitutions and particularly below the Ca2+cations; in the molecule, around the chlorine atom when Ca2+interacts strongly with this basic site in a monodentate mode. This study shows the important role of the alkaline earth cations on the adsorption of atrazine on clays, suggesting that the atrazine pesticide retention will be significant in Ca2+-montmorillonite clays. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, 118, route de Narbonne, Université de Toulouse, UPS, IRSAMC, Toulouse, F-31062, France.|CNRS (UMR 5626), F-31062, Toulouse, France.|Ecole d'Ingénieurs de Purpan, 75, Université de Toulouse, INPT, voie du TOEC, BP 57611, Toulouse Cedex 03, F-31076, France.
authors.forename: Bastien
authors.initials: B
authors.lastname: Belzunces
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, 118, route de Narbonne, Université de Toulouse, UPS, IRSAMC, Toulouse, F-31062, France.|CNRS (UMR 5626), F-31062, Toulouse, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Hoyau
authors.affiliation: CEMES - Centre d'Elaboration de Matériaux et d'Etudes Structurales - CNRS (UPR 8011), 29 rue Jeanne Marvig, Toulouse, F-31055, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Benoit
authors.affiliation: CEMES - Centre d'Elaboration de Matériaux et d'Etudes Structurales - CNRS (UPR 8011), 29 rue Jeanne Marvig, Toulouse, F-31055, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Tarrat
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, 118, route de Narbonne, Université de Toulouse, UPS, IRSAMC, Toulouse, F-31062, France.|CNRS (UMR 5626), F-31062, Toulouse, France.|Ecole d'Ingénieurs de Purpan, 75, Université de Toulouse, INPT, voie du TOEC, BP 57611, Toulouse Cedex 03, F-31076, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Bessac
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D001280:Atrazine / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D000077215:Clay; D010575:Pesticides / Q000737:chemistry*; D011789:Quantum Theory; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; D010575:Pesticides; D001546:Bentonite; C049037:aluminosilicate; D001280:Atrazine; D002118:Calcium; D000077215:Clay
keywords: adsorption energy; atrazine pesticide; clay minerals; interaction energy; theoretical calculations