Adsorption of chloroacetanilide herbicides on soil and its components III. Influence of clay acidity, humic acid coating and herbicide structure on acetanilide herbicide adsorption on homoionic clays

摘要

Adsorption of chloroacetanilide herbicides on homoionic montmorillonite, soil humic acid, and their mixtures was studied by coupling batch equilibration and FT IR analysis. Adsorption isotherms of acetochlor, alachlor, metolachlor and propachlor on Ca 2+ |, Mg 2+ |, Al 3+ | and Fe 3+ | saturated clays were well described by the Freundlich equation. Regardless of the type of exchange cations, K f decreased in the order of metolachlor > acetolachlor > alachlor > propachlor on the same clay. FT IR spectra showed that the carbonyl group of the herbicide molecule was involved in binding, probably via H bond with water molecules in the clay interlayer. The type and position of substitutions around the carbonyl group may have affected the electronegativity of oxygen, thus influencing the relative adsorption of these herbicides. For the same herbicide, adsorption on clay increased in the order of Mg 2+