Adsorption and Degradation of Triasulfuron on Homoionic Montmorillonites

Alba Pusino1, Ilaria Braschi2 and Carlo Gessa2
1 Dipartimento di Scienze Ambientali Agrarie e Biotecnologie Agro-Alimentari, Università di Sassari, Viale Italia 39, 07100 Sassari, Italy
2 Istituto di Chimica Agraria, Università di Bologna, Via Berti Pichat 11, 40127 Bologna, Italy
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Abstract: The adsorption and degradation of the herbicide triasulfuron [2-(2-chloroethoxy)-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide] (CMMT) on homoionic Fe3+-, Al3+-, Ca2+-, or Na+-exchanged montmorillonite in aqueous medium were studied. Ca- and Na-exchanged montmorillonite were ineffective in the adsorption and degradation of triasulfuron. The adsorption on Fe- and Al-exchanged montmorillonite was rapid, and equilibrium was attained after 5 min. Degradation of the herbicide was slow and the type 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-chloroethoxy)-N-[[(4-hydroxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide (CHMT), and 1-[2-(2-chloroethoxy)benzene-1-sulfonyl]-7-acetyltriuret (CBAT) were the only identified products, whereas 2-amino-4-methoxy-6-methyltriazine (AMMT), CBSA, CHMT, and CBAT were the primary metabolites for the Al3+-rich montmorillonite. A Fourier transform infrared (FT-IR) study of montmorillonite samples after the interaction with triasulfuron in organic solution suggests that the hydrolysis mechanism involves the adsorption of the herbicide on the 2:1 layers.

Key Words: Adsorption • Degradation • Herbicides • Infrared Spectroscopy • Montmorillonite • Triasulfuron

Clays and Clay Minerals; February 2000 v. 48; no. 1; p. 19-25; DOI: 10.1346/CCMN.2000.0480103
© 2000, The Clay Minerals Society
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