EFFECTS OF METHOD OF CLAY PREPARATION ON SUBSEQUENT ADSORPTION OF THE INSECTICIDE FENSULFOTHION

Abstract

The manner in which montmorillonite and illite adsorbents were prepared for batch-type adsorption experiments determined the extent of fensulfothion (Dasanit ® ) adsorption. Curve-fitting techniques produced regression equations for the isotherms generated by four clay systems (Na– and Ca–montmorillonite and illite) and by the four preparation treatments per system (freeze-dried; freeze-dried, resuspended; freeze-dried, 100% RH; suspension). Only the regression equation isotherms of the Na–illite system and one treatment comparison of the Ca–illite system (freeze-dried, 100% RH vs. suspension) were not significantly different (5% level). In general, the freeze-drying process increased fensulfothion adsorption relative to that for the same clay in suspension. Conditioning freeze-dried clay with water vapor (100% RH) prior to adsorption decreased fensulfothion adsorption relative to the freeze-dried clay (dried over P 2 O 5 ).