INTERACTION OF FLUAZIFOP-BUTYL WITH HOMOIONIC CLAYS

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Abstract
We investigated the interaction of Fluazifop-butyl with Na-, Fe(III)-, Al- and Cu-montmorillonite by submitting self-supporting films or powders of clay, previously immersed in a CHCl3 solution of the herbicide, to infrared (IR) and x-ray analysis, respectively. The IR results demonstrate that Fluazifop-butyl is adsorbed onto all homoionic clays by at least two different mechanisms, both depending on the acidic properties of water molecules coordinated to the exchangeable cations. The first, acting for all clays except Na samples, is the protonation of the pyridinic nitrogen atom of the organic molecule followed by adsorption on the clay surfaces. Evidence for this is the apparance on NH stretching that persists after heating at 110°C. The second, regarding also Naclay, is the formation of hydrogen bonds between the ester carbonyl group of the herbicide and the hydration water of metal ions, as evidenced by the shift of C·O stretch toward lower frequencies; dehydration at 110°C causes it to revert to the characteristic value of the free molecule. The adsorption of pesticide is supported also by x-ray analyses: the light increase of d001 values of partially dehydrated organoclay complexes suggests that a single layer of Fluazifop-butyl is present in the interlamellar region of montmorillonite. The CEC of treated samples is lower than that before adsorption because of the hydrophobic nature of the herbicide, which prevents the total exchange of adsorbed cations by neutral salt solutions © Williams & Wilkins 1987. All Rights Reserved.

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