The Influence of Temperature and Time on the Adsorption of Paraquat, Diquat, 2,4‐D and Prometone by Clays, Charcoal, and an Anion‐Exchange Resin

Abstract

Abstract The effects of temperature and exposure time on the adsorption of four organic compounds by montmorillonite, kaolinite, charcoal, and an anion‐exchange resin in a phosphate buffer of pH 6.0 were investigated. Organic cations (diquat and paraquat) were preferentially adsorbed by the clays up to the cationexchange capacity. Adsorption appeared to be one of ion exchange. X‐ray analysis indicated the cations were held in the lattice of the montmorillonite with the plane of the ring parallel to the silicate sheets. An organic anion (2,4‐D) was negatively adsorbed by the clays; and a s ‐triazine compound (prometone) in molecular form, was adsorbed by montmorillonite but not kaolinite. X‐ray analysis indicated that prometone was located within the clay lattice but the orientation was uncertain. The adsorption mechanism was physical in nature being temperature dependent. The 2,4‐D was adsorbed by the anion‐exchange resin through ion exchange forces and the equilibrium was influenced by temperature and exposure time. Prometone was adsorbed by the anion‐exchange resin to a much lesser degree, was also temperature and time dependent, and appeared to be physically bound. All of the organic compounds were adsorbed by charcoal and each was influenced differently by temperature and exposure time.