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Use of clay/β-cyclodextrin formulations to obtain a slow release of a hydrophobic herbicide

AuthorsVillaverde Capellán, J. ; Sopeña Vázquez, F.
Issue Date2008
PublisherTechnische Universität München
CitationFresenius Environmental Bulletin 17(12b): 2250-2254 (2008)
AbstractThe study aimed to prepare slow release formulations of the hydrophobic herbicide norflurazon (4-chloro-5-methyl-amino-2-(α,α,α)- trifluoro-m-tolypyridazin-3-(2H)-one) based on a standard montmorillonite, a pillared montmorillonite and an organo-montmorillonite. For this purpose, a β-cyclodextrin-norflurazon solution was used, due to its ability to form an inclusion complex which yields an increase in norflurazon solubility in water (up to 5 times). The amount of herbicide adsorbed on the standard montmorillonite was directly proportional to the herbicide concentration in solution, obtaining an herbicide adsorption 5 times higher when β-cyclodextrin-norflurazon solutions were used. The organo-clay was prepared modifying the surface of montmorillonite from hydrophilic to hydrophobic preadsorbing an organic cation (phenyltrimethylamonium), at a loading yielded the highest affinity of adsorption for norflurazon. Pillared clay used was an alumina pillared montmorillonite which showed a similar affinity by norflurazon adsorption than the untreated montmorillonite. Water release experiments were also performed in order to test the slow release capacity of the different matrices selected in this study. Pillared montmorillonite formulations showed a similar norflurazon release profile compared with the untreated montmorillonite. Likewise, release profiles of the pillared clay with two different herbicide loadings were obtained revealing the influence of the herbicide loading on the release rate from the formulations. The release profile corresponding to the organo-clay sample showed the slowest release rate, reaching only a 24% of the herbicide loaded released after 3 days of experiment. The results of this study indicate that the use of selectively-modified clays could are useful for the preparation of herbicide slow release formulations, where the increase of the hydrophilic character of the montmorillonite using an organic cation is a critical property when slow release formulations of herbicide want to be prepared. The use of these formulations can be advantageous, because they can minimize the risk of groundwater contamination and permit herbicide use reduced rates, maintaining the desired concentrations of herbicide in the topsoil layer for longer periods of weed control.
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