Adsorption of picloram on clays nontronite,illite and kaolinite: equilibrium and herbicide-clays surface complexes |
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| Authors: | Jose L Marco-Brown Eric M Gaigneaux Rosa M Torres Sánchez María dos Santos Afonso |
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| Institution: | 1. Facultad de Ciencias Exactas y Naturales, Departamento de Química Inorgánica, Analítica y Química Física, and CONICET-Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Ciudad Universitaria Pabellón II 3er Piso, Int. Güiraldes 2160 (C1428EHA), Universidad de Buenos Aires, Buenos Aires, Argentina;2. Institute of Condensed Matter and Nanosciences (IMCN), Division Solids, Molecules and Reactivity (MOST), Université Catholique de Louvain, Louvain-la-Neuve, Belgium;3. CONICET-CCT La Plata-CIC, CETMIC (Centro de Tecnología en Recursos Minerales y Cerámica), M. B. Gonnet, Argentina |
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| Abstract: | The picloram (PCM) adsorption on nontronite, illite and kaolinite was studied at pH 3, 5 and 7. The adsorption isotherms had well-fitted to Langmuir and Freundlich models equations. The interactions of PCM with the clay mineral surfaces exhibited an anionic profile adsorption, with a decrease in adsorption when the pH increases. The PCM adsorption capacity increases in the following order: kaolinite?<?illite?<?nontronite. The X-ray diffraction (XRD) analysis of PCM-clay samples revealed that the picloram molecule does not enter into the clays basal space. The interaction of PCM with clays surface sites through nitrogen of the pyridine ring was confirmed by X-ray photoelectron spectroscopy (XPS). Due to the anionic form of PCM, the adsorption onto the external and edges surface sites of the clay minerals was proposed. |
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| Keywords: | Adsorption picloram herbicide clays XPS surface complexes |
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