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 montmorilloni tes saturated with the cations hexadecyltrimethylammonium (HDTMA+), do decyltrimethylammonium (DDTMA+) and tetramethylammonium (TMA+) in aque ous media. The results were compared with those obtained for the adsor ption of these pesticides by natural montmorillonite, humic acid and b y the soil organic matter and with the octanol-water partition coeffic ient (Kow) of the compounds. Results indicated that regarding the capa city to remove azinphosmethyl from water the organic matter derived fr om the organic cations HDTMA+ and DDTMA+ is 5-10 times more effective than humic acid; 10-20 times more effective than the organic matter fr om 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 d ichlorvos from water, in turn, their efficiency is 50 times higher tha n that of octanol. These findings may find application in the removal of azinphosmethyl or other sparingly water soluble organophosphorus pe sticides from aquifers.