INTERACTION OF RIMSULFURON WITH SMECTITES

The adsorption of the sulfonylurea herbicide rimsulfuron, arbonyl)-3-( ethylsulfonyl)-2-pyridinesulfonamide], on clay minerals with different saturating cations was studied. Three smectites with different lattic e charge distribution (hectorite, montmorillonite and nontronite) were selected and made homoionic to Ca2+, Cu2+ and Al3+. Because of the in stability of rimsulfuron in water, the experiments were carried out in chloroform solution. The interaction mechanism depends on the nature of the saturating cation and the tetrahedral layer charge of the silic ate. Among the exchangeable ions studied, only Al3+ is able to produce degradation of the herbicide to idin-2-yl)-N-[(3-(ethylsulfonyl)-2-py ridinyl]urea. In this case, the lower the tetrahedral charge, the more active the degradation. The Ca2+-saturated clays are ineffective in t he degradation. In contrast, the formation of a stable chelate complex with the saturating ion permits rimsulfuron to be adsorbed to a rathe r high extent into Cu(II)-clays and to be stable against degradation.