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Adsorption/desorption of fungicides in natural clays from Southeastern Spain
AbstractNine natural clay samples, collected in the eastern Andalusian region (South of Spain), were evaluated for the retention of two widely used non-ionic fungicides, metalaxyl and fludioxonil. The clays showed different mineralogical composition and granulometry, had high Ca content, and presented medium–low cation exchange capacity and specific surface area and low organic carbon (OC) content (≤0.8%). Various equations were used for the fitting of kinetic and adsorption data. The pseudo-second-order kinetic model was successfully fitted to the experimental kinetic data. The Freundlich equation was better suited for the fitting of metalaxyl adsorption, while both Freundlich and Langmuir equations could be used to explain the retention of fludioxonil. Adsorption experiments, carried out using the batch approach, indicated that metalaxyl, a more polar fungicide, was always retained to a greater extent than fludioxonil, probably through electrostatic interactions. The retention of both fungicides was related with the OC content of the clays and their granulometry. The removal of clay OC led to a greater decrease in fludioxonil adsorption, probably due to its higher hydrophobicity. The retention extent of metalaxyl on selected clays, at 10 and 20°C, was maintained up to 6months, reflecting the high stability of pesticide adsorption on the selected adsorbents. A preliminary study at two pesticide concentrations showed that pilloring onion seeds with metalaxyl or fludioxonil may cause phytotoxicity to seedling growth when compared with control seeds.
Graphical abstract
HighlightsInclusion of pesticides using natural clays will add value to seed coating strategies.The fungicides fludioxonil and metalaxyl were adsorbed on natural Spanish clays.Metalaxyl, more polar, was always more strongly retained by the clays.Clay granulometry and organic carbon content were relevant in fungicide adsorption.Metalaxyl release from clays, at 10 and 20°C, was stable up to 6months.
Adsorption/desorption of fungicides in natural clays from Southeastern Spain
AbstractNine natural clay samples, collected in the eastern Andalusian region (South of Spain), were evaluated for the retention of two widely used non-ionic fungicides, metalaxyl and fludioxonil. The clays showed different mineralogical composition and granulometry, had high Ca content, and presented medium–low cation exchange capacity and specific surface area and low organic carbon (OC) content (≤0.8%). Various equations were used for the fitting of kinetic and adsorption data. The pseudo-second-order kinetic model was successfully fitted to the experimental kinetic data. The Freundlich equation was better suited for the fitting of metalaxyl adsorption, while both Freundlich and Langmuir equations could be used to explain the retention of fludioxonil. Adsorption experiments, carried out using the batch approach, indicated that metalaxyl, a more polar fungicide, was always retained to a greater extent than fludioxonil, probably through electrostatic interactions. The retention of both fungicides was related with the OC content of the clays and their granulometry. The removal of clay OC led to a greater decrease in fludioxonil adsorption, probably due to its higher hydrophobicity. The retention extent of metalaxyl on selected clays, at 10 and 20°C, was maintained up to 6months, reflecting the high stability of pesticide adsorption on the selected adsorbents. A preliminary study at two pesticide concentrations showed that pilloring onion seeds with metalaxyl or fludioxonil may cause phytotoxicity to seedling growth when compared with control seeds.
Graphical abstract
HighlightsInclusion of pesticides using natural clays will add value to seed coating strategies.The fungicides fludioxonil and metalaxyl were adsorbed on natural Spanish clays.Metalaxyl, more polar, was always more strongly retained by the clays.Clay granulometry and organic carbon content were relevant in fungicide adsorption.Metalaxyl release from clays, at 10 and 20°C, was stable up to 6months.
Adsorption/desorption of fungicides in natural clays from Southeastern Spain
Rodríguez-Liébana, José Antonio (author) / López-Galindo, Alberto (author) / Jiménez de Cisneros, Concepción (author) / Gálvez, Antonia (author) / Rozalén, Marisa (author) / Sánchez-Espejo, Rita (author) / Caballero, Emilia (author) / Peña, Aránzazu (author)
Applied Clay Science ; 132-133 ; 402-411
2016-07-11
10 pages
Article (Journal)
Electronic Resource
English
Adsorption/desorption of fungicides in natural clays from Southeastern Spain
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