Adsorption and Desorption of Diquat, Paraquat, Prometone, and 2,4‐D by Charcoal and Exchange Resins

Abstract

AbstractThe adsorption of diquat, paraquat, prometone, and 2,4‐D by charcoal and cation‐ and anion‐exchange resins and their desorption with water and 1M NaCl solutions has been investigated. Prometone and 2,4‐D were adsorbed by charcoal in much greater amounts than were diquat and paraquat, but all of the compounds were readily desorbed with deionized water following normal Freundlich isotherms. Diquat and paraquat were adsorbed by the cation exchange resins (H and Na forms) and both herbicides were readily desorbed by Na+ ions but not with deionized water. Diquat was preferentially adsorbed over paraquat by the cation‐exchange resins and diquat was also more effective in displacing paraquat from the resins. Prometone was adsorbed in small amounts by the cation resin in the Na form and the anion resin in the Cl form and was readily desorbed with deionized water. Prometone was adsorbed by the cation resin in the H form in amounts which were similar to those for diquat and paraquat. None of the prometone adsorbed by the H‐resin was desorbed by equilibrating with water. Prometone desorbed from the H‐resin with 1M NaCl solutions was identified as hydroxypropazine.