title: Removal of the herbicide 2,4-dichlorophenoxyacetate from water to zinc-aluminium-chloride layered double hydroxides.
abstract: Batch sorption studies were conducted to investigate the potential of [Zn-Al-Cl] layered double hydroxides (LDHs) for the removal of the herbicide 2,4-dichlorophenoxyacetate (2,4-D) from contaminated aqueous solutions. Experiments were performed at different pH values, initial pesticide concentration, solid/pesticide ratio and anion exchange capacity of LDHs. The LDH samples evaluated had very high retention capacity for 2,4-D whose removal was a rapid process, as a quasi-equilibrium state was reached after 1-h reaction time. The adsorption can be described by Langmuir-type isotherms, with an average affinity constant of 12.5 L mmol(-1). At initial 2,4-D concentrations between 0.08 and 4 m molL(-1), the solids removed up to 98% of the pesticide. Physicochemical characterization of the LDH solids, both fresh and after removal of 2,4-D, by X-ray diffraction, infrared spectroscopy and thermogravimetry, indicates that the retention of 2,4-D is done by adsorption on the surface of the solid for low 2,4-D concentrations. However, a combination of surface adsorption and interlayer ion exchange takes place when the 2,4-D concentration is high.
authors.affiliation: School of Science and Engineering, Al Akhawayn University, P.O. Box 1871, Ifrane 53000, Morocco. legrouri@aui.ma
authors.forename: A
authors.initials: A
authors.lastname: Legrouri
authors.forename: M
authors.initials: M
authors.lastname: Lakraimi
authors.forename: A
authors.initials: A
authors.lastname: Barroug
authors.forename: A
authors.initials: A
authors.lastname: De Roy
authors.forename: J P
authors.initials: JP
authors.lastname: Besse
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry / Q000302:isolation & purification*; D000327:Adsorption; D000535:Aluminum / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D006540:Herbicides / Q000737:chemistry / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry*; D007259:Infrared Rays; D007474:Ion Exchange; D013057:Spectrum Analysis; D013818:Thermogravimetry; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry
chemical_list: D002712:Chlorides; D006540:Herbicides; D006878:Hydroxides; D014874:Water Pollutants, Chemical; D015084:2,4-Dichlorophenoxyacetic Acid; D000535:Aluminum; D015032:Zinc