Adsorption of Picloram by Soil Colloids and Various Other Adsorbents

Abstract

The adsorption of picloram (4-amino-3,5,6-trichloropicolinic acid) was studied for several Canadian prairie soils and for various other adsorbents. The kd values for the soils ranged from 0.09 to 0.75 and were correlated only with soil organic matter. The kd values for other adsorbents varied from 0 to 232, the order of adsorption being activated charcoal > anion exchange resin > peat moss > cellulose triacetate. There was no adsorption of picloram on montmorillonite and kaolinite clays, cation exchange resin, wheat straw (Triticum aestivumL.), or cellulose powder. The differences in the adsorption of picloram were explained on the basis of the relative affinities of the various adsorptive surfaces for the molecular or the ionized forms of the acid.