Adsorption and Desorption of Diquat, Paraquat, and Prometone by Montmorillonitic and Kaolinitic Clay Minerals

Abstract

Abstract The adsorption of diquat, paraquat, and prometone by montmorillonite and kaolinite clays and their desorption using several extracting solutions has been investigated. Diquat and paraquat were adsorbed by the clay minerals to approximately the cation‐exchange capacity of the clays. Approximately 80% of each of the herbicides was displaced from kaolinite clay with Ba 2+ ions. A total of 5% of each of the compounds was removed from montmorillonite using 1 M BaCl 2 solutions. The two herbicides were found to exchange for one another on both clay minerals in a one‐for‐one manner. Paraquat was preferentially adsorbed over diquat by both clays in competitive ion studies and was also found to be more difficult of the two herbicides to displace. Prometone which was adsorbed by the montmorillonite clay was more readily desorbed with deionized water than with 1 M BaCl 2 . Small amounts of prometone which were adsorbed by the kaolinite clay were also readily desorbed by deionized water.