EVALUATION OF ADSORBABILITY OF PESTICIDES IN WATER ON POWDERED ACTIVATED CARBON USING OCTANOL-WATER PARTITION-COEFFICIENT

The 1-octanol-water partition coefficients (logPow) of seven pesticide s, i.e., Hymexazol, methomyl, imidacloprid, thiophanatemethyl, carbary l, linuron, thiobencarb, were determined by,y RPHPLC method. The relat ion between these estimated logPow and adsorption isotherm parameters on powdered activated carbon was studied by correlating their logPow v alues with the Freundlich adsorption parameters. The adsorption parame ter, logk, was found to increase with the increase of logPow for the p esticides examined. The activated carbon amount needed for lowering pe sticide concentration from 500 mu g/l to 50 mu g/l was calculated. The amount of activated carbon needed for hymexazol (logPow, 0.11) was 68 8.5 mg/l, while that for thiobencarb (logPow, 3.78) was 5.1 mg/l, whic h suggests that pesticides with a high polarity, i.e., a low Pow, are difficult to remove by powdered activated carbon. (C) 1997 IAWQ. Publi shed by Elsevier Science Ltd.