Effect of ionic strength and pH on the adsorption of selected herbicides on Amberlite

Abstract

The effect of ionic strength on the adsorption of alachlor, trifluralin, and prometryn on Amberlite XAD-4 polymeric resin is studied. Static adsorption experiments are carried out at pH 3–6.5 and ionic strength 0.01–2 M at 20°C. By increasing the ionic strength, the adsorption of herbicides can be significantly increased. The electrolyte addition affects both the effectiveness and efficiency of adsorption, leading eventually to a saturation of the resin surface. An explanation of the alteration of adsorption mechanisms, caused by ionic strength, is given, based mainly on the reduction in repulsive forces at the resin–herbicide interface and between adsorbing herbicide molecules, since both resin and herbicides have a polar ring as part of their structure.