Adsorption of herbicides 2,4-D and acetochlor on inorganic–organic bentonites

Inorganic–organic bentonites were prepared by co-adsorption of cetyl trimethylammonium (CTMA) ions onto bentonites intercalated by poly(hydroxo aluminum) or poly(hydroxo iron) cations. The inorganic–organic bentonites adsorbed much more anionic herbicide 2,4-D than the inorganic and organic bentonites. For bentonites modified with poly(hydroxo iron) and CTMA ions, the enhancement may be attributed not only to the van der Waals interaction between 2,4-D and the organic cations, but also to the strong bonding of 2,4-D on the inorganic cations, which was confirmed by desorption studies, XRD measurements and FTIR analysis. The inorganic–organic bentonites did not show higher adsorption of acetochlor compared to the organo-bentonite. For such a nonionic herbicide, the van der Waals interaction dominated the adsorption, and the inorganic modification did not make an obvious contribution to the adsorption.