title: Slow-release formulations of the herbicide picloram by using Fe-Al pillared montmorillonite.
abstract: Slow-release formulations of the herbicide picloram (PCM, 4-amino-3,5,6-trichloropyridine-2-carboxylic acid) were designed based on its adsorption on pillared clays (pillared clays (PILCs)) for reducing the water-polluting risk derived from its use in conventional formulations. Fe-Al PILCs were synthesized by the reaction of Na+-montmorillonite (SWy-2) with base-hydrolyzed solutions of Fe and Al. The Fe/(Fe + Al) ratios used were 0.15 and 0.50. The PCM adsorption isotherms on Fe-Al PILCs were well fitted to Langmuir and Freundlich models. The PCM adsorption capacity depended on the Fe content in the PILCs. Slow-release formulations were prepared by enhanced adsorption of the herbicide from PCM-cyclodextrin (CD) complexes in solution. CDs were able to enhance up to 2.5-fold the solubility of PCM by the formation of inclusion complexes where the ring moiety of the herbicide was partially trapped within the CD cavity. Competitive adsorption of anions such as sulfate, phosphate, and chloride as well as the FTIR analysis of PCM-PILC complexes provided evidence of formation of inner sphere complexes of PCM-CD on Fe-Al PILCs. Release of the herbicide in a sandy soil was lower from Fe-Al PILC formulations relative to a PCM commercial formulation.
authors.affiliation: Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, C1428EHA, Buenos Aires, Argentina. josemarcobrown@gmail.com.|Instituto de Química Física de los Materiales, Medio Ambiente y Energía de la Facultad de Ciencias Exactas y Naturales (INQUIMAE), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina. josemarcobrown@gmail.com.|Instituto de Investigación e Ingeniería Ambiental (3iA), CONICET, Escuela de Ciencia y Tecnología, UNSAM, 25 de Mayo y Francia (1650), San Martín, Argentina. josemarcobrown@gmail.com.
authors.forename: Jose L
authors.initials: JL
authors.lastname: Marco-Brown
authors.affiliation: Institute of Natural Resources and Agrobiology (IRNAS-CSIC), Reina Mercedes 10. Apdo. 1052, 41080, Sevilla, Spain.
authors.forename: Tomás
authors.initials: T
authors.lastname: Undabeytia
authors.affiliation: Centro de Tecnología en Recursos Minerales y Cerámica (CETMIC), CONICET-CCT La Plata-CIC, Camino Centenario y 506 CC (49), B1897ZCA, M. B. Gonnet, Argentina.
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Torres Sánchez
authors.affiliation: Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, C1428EHA, Buenos Aires, Argentina.|Instituto de Química Física de los Materiales, Medio Ambiente y Energía de la Facultad de Ciencias Exactas y Naturales (INQUIMAE), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: María
authors.initials: M
authors.lastname: Dos Santos Afonso
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates; D001546:Bentonite; D000077215:Clay; D006540:Herbicides; D010846:Picloram
chemical_list: D000538:Aluminum Silicates; D006540:Herbicides; D001546:Bentonite; D010846:Picloram; D000077215:Clay
keywords: Adsorption; Fe–Al pillared montmorillonite; Picloram; Slow-release formulations