Adsorption and degradation of triasulfuron on homoionic montmorillonites

The adsorption and degradation of the herbicide triasulfuron [2-(2-chloroet hoxy)-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulf onamide] (CMMT) on homoionic Fe3+-, Al3+-, Ca2+-, or Na+-exchanged montmori llonite in aqueous medium were studied. Ca- and Na-exchanged montmorillonit e were ineffective in the adsorption and degradation of triasulfuron. The a dsorption on Fe- and Al-exchanged montmorillonite was rapid, and equilibriu m was attained after 5 min. Degradation of the herbicide was slow and the t ype of the degradation products depended on the nature of the exchangeable cations. In the presence of Fe3+-rich montmorillonite, the metabolites 2-(2 -chloroethoxy)benzenesulfonamide (CBSA), 2-(2-chloroerhoxy)-N-[[(4-hydroxy- 6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide (CHMT), and 1 -[2-(2-chtoroethoxy)benzene-1-sulfonyl]-7-acetyl-triuret (CBAT) were the on ly identified products, whereas 2-amino-3-methoxy-6-methyltriazine (AMMT), CBSA, CHMT, and CBAT were the primary metabolites fur the Al3+-rich montmor illonite. A Fourier transform infrared (FT-TR) study of montmorillonite sam ples after the interaction with triasulfuron in organic solution suggests t hat the hydrolysis mechanism involves the adsorption of the herbicide on th e 2:1 layers.