SOME PHYSICO‐CHEMICAL INTERACTIONS OF PARAQUAT WITH SOIL ORGANIC MATERIALS AND MODEL COMPOUNDS I. EFFECTS OF TEMPERATURE, TIME AND ADSORBATE DEGRADATION ON ARAQUAT ADSORPTION

Abstract

Summary. Some investigations were carried out on the adsorption of paraquat by a range of organic materials which included an organic soil, various humic fractions from that soil, model polymers prepared by the oxidative coupling of benzoquinone, the ion exchange resins Zeo‐Karb 216 and 226, and Amberlite XAD‐2. The time required for the adsorption process to reach equilibrium ranged from about 3 h (for the soil and humic preparations) to about 48 h (for the more highly cross‐linked materials). Adsorption by Amberlite XAD‐2, a cross‐linked polystyrene resin, was very small, presumably because it lacked ion‐exchange sites.The results suggested that particle diffusion control was operating and the different equilibrium times reflected different degrees of molecular complexity within the adsorbents.Temperature, within the 20°–70°C range, did not affect the adsorption equilibrium, and this is indirect evidence for ion exchange as the primary adsorption mechanism. No evidence was found for decomposition of paraquat in the adsorption systems studied.Quelques interactions physico‐chimiques du paraquat avec des inatéaux de sol organique et des composes modéles I. Effets de la température, du temps et de la dégradation sur I'adsorption du paraquat