title: Adsorption of diclofenac onto organoclays: Effects of surfactant and environmental (pH and temperature) conditions.
abstract: Among pharmaceutical products (PPs) recalcitrant to water treatments, diclofenac shows a high toxicity and remains at high concentration in natural aquatic environments. The aim of this study concerns the understanding of the adsorption mechanism of this anionic PP onto two organoclays prepared with two long-alkyl chains cationic surfactants showing different chemical nature for various experimental pH and temperature conditions. The experimental data obtained by a set of complementary techniques (X-ray diffraction, elemental analyses, gas chromatography coupled with mass spectrometry, and Fourier transform infrared spectroscopy) and the use of Langmuir, Freundlich and Dubinin-Radushkevish equation models, reveal that organoclays show a good affinity to diclofenac which is enhanced as the temperature is under 35°C and for pH above 4.5 (i.e. >pKa of diclofenac) while the chemical nature of surfactant appears to play a minor role. The thermodynamic parameters derived from the fitting procedure point out the strong electrostatic interaction with organic cations adsorbed within the interlayer space in the organoclays for the adsorption of diclofenac. This study stress out the application of organoclays for the adsorption of a recalcitrant PPs in numerous aquatic compartments that can be used as a complement with activated carbon for waste water treatment.
authors.affiliation: Institut des Sciences de la Terre d'Orléans, UMR 7327, CNRS-Université d'Orléans, 1A Rue de la Férollerie, 45071 Orléans Cedex 2, France. Electronic address: tiago.de-oliveira@cnrs-orleans.fr.
authors.forename: Tiago
authors.initials: T
authors.lastname: De Oliveira
authors.affiliation: Institut des Sciences de la Terre d'Orléans, UMR 7327, CNRS-Université d'Orléans, 1A Rue de la Férollerie, 45071 Orléans Cedex 2, France. Electronic address: regis.guegan@univ-orleans.fr.
authors.forename: Régis
authors.initials: R
authors.lastname: Guégan
authors.affiliation: Institut des Sciences de la Terre d'Orléans, UMR 7327, CNRS-Université d'Orléans, 1A Rue de la Férollerie, 45071 Orléans Cedex 2, France. Electronic address: thomas.thiebault@cnrs-orleans.fr.
authors.forename: Thomas
authors.initials: T
authors.lastname: Thiebault
authors.affiliation: Institut des Sciences de la Terre d'Orléans, UMR 7327, CNRS-Université d'Orléans, 1A Rue de la Férollerie, 45071 Orléans Cedex 2, France. Electronic address: claude.le-milbeau@univ-orleans.fr.
authors.forename: Claude Le
authors.initials: CL
authors.lastname: Milbeau
authors.affiliation: Institut des Sciences de la Terre d'Orléans, UMR 7327, CNRS-Université d'Orléans, 1A Rue de la Férollerie, 45071 Orléans Cedex 2, France. Electronic address: fabrice.muller@univ-orleans.fr.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Muller
authors.affiliation: Institut des Sciences de la Terre d'Orléans, UMR 7327, CNRS-Université d'Orléans, 1A Rue de la Férollerie, 45071 Orléans Cedex 2, France; Centro de Ciências Exatas e da Tecnologia, Universidade de Caxias do Sul, Rua Francisco Getúlio Vargas, 1130, Caxias do Sul, 95070-560, RS, Brazil. Electronic address: vsteixeira@ucs.br.
authors.forename: Vinicius
authors.initials: V
authors.lastname: Teixeira
authors.affiliation: Centro de Ciências Exatas e da Tecnologia, Universidade de Caxias do Sul, Rua Francisco Getúlio Vargas, 1130, Caxias do Sul, 95070-560, RS, Brazil. Electronic address: mgiovan1@ucs.br.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Giovanela
authors.affiliation: Institut des Sciences de la Terre d'Orléans, UMR 7327, CNRS-Université d'Orléans, 1A Rue de la Férollerie, 45071 Orléans Cedex 2, France. Electronic address: mohammed.boussafir@univ-orleans.fr.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Boussafir
mesh_terms: D000327:Adsorption; D000465:Algorithms; D000538:Aluminum Silicates / Q000737:chemistry*; D001546:Bentonite; D000077215:Clay; D004008:Diclofenac / Q000737:chemistry* / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D015233:Models, Statistical; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics; D014874:Water Pollutants, Chemical
chemical_list: D000538:Aluminum Silicates; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D001546:Bentonite; D004008:Diclofenac; D000077215:Clay
keywords: Adsorption; Cationic surfactant; Diclofenac; Organoclay; Pharmaceutical