Organo-clays as adsorbents for azinphosmethyl and dichlorvos in aqueous medium

Using adsorption isotherms, a study was performed of the adsorption of two organophosphorus pesticides, azinphosmethyl (sparingly soluble in water) and dichlorvos (moderately soluble in water), by montmorillonites saturated with the cations hexadecyltrimethylammonium (HDTMA⁺), dodecyltrimethylammonium (DDTMA⁺) and tetramethylammonium (TMA⁺) in aqueous media. The results were compared with those obtained for the adsorption of these pesticides by natural montmorillonite, humic acid and by the soil organic matter and with the octanol-water partition coefficient (Kow) of the compounds. Results indicated that regarding the capacity to remove azinphosmethyl from water the organic matter derived from the organic cations HDTMA⁺ and DDTMA⁺ is 5–10 times more effective than humic acid; 10–20 times more effective than the organic matter from the soil and 20–50 times more efficient than octanol. However, both organic phases, that derived from the organic matter of the soil and that of the organic cations, have similar effectiveness for removing dichlorvos from water, in turn, their efficiency is 50 times higher than that of octanol. These findings may find application in the removal of azinphosmethyl or other sparingly water soluble organophosphorus pesticides from aquifers.