Adsorption of imazethapyr, an imidazolinone herbicide, was measured from dilute suspensions onto montmorillonite clay
and complexes of montmorillonite with Cu and humic acid. Adsorption of imazethapyr was found to be greater for the
Cu-montmorillonite and Cu-humic acid-montmorillonite complexes than by montmorillonite alone. Isotherm shape was
similar for all supports studied. Adsorption of imazethapyr varied with pH for montmorillonite and for Cu-humic acidmontmorillonite
complex. The pH had no apparent effect on imazethapyr adsorption to the Cu-montmorillonite complex. This
might be due to imazethapyr retention at high pH by Cu ions linked to the clay. Imazethapyr adsorption kinetics was faster for
Cu-montmorillonite (15 min) and Cu-humic acid-montmorillonite (30 min) than for montmorillonite (240 min). The copperhumic
acid complexes with montmorillonite might be used to detoxify water contaminated with imazethapyr