Dimepiperate Adsorption and Hydrolysis on Al3+-, Fe3+-, Ca2+-, and Na+-Montmorillonite

A. Pusino1, W. Liu2 and C. Gessa3
1 Istituto di Chimica Agraria e Forestale, Università di Reggio Calabria, Piazza San Francesco di Sales 4, 89061 Gallina (RC), Italy
2 Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China
3 Istituto di Chimica Agraria, Università di Bologna, Via Berti Pichat 11, 40127 Bologna, Italy

Abstract: The adsorption of the herbicide dimepiperate S-(α,α-dimethylbenzyl)-1-piperidinecarbothioate on homoionic Fe3+-, Al3+-, Ca2+-, and Na+-montmorillonite was studied in aqueous medium. The adsorption is described well by the Freundlich equation. The adsorption capacity decreases in the order Fe3+ > Al3+ > Ca2+ > Na+ clay. The dimepiperate adsorption from chloroform solution was also investigated by analytical, spectroscopic, and X-ray powder diffraction techniques. IR results suggest that the adsorption involves the interaction of the thioester carbonyl group of dimepiperate possibly with the surrounding water of metal ions. On Al3+ and Fe3+ clays, this interaction leads to hydrolysis of the thioester bond and formation of the thiol and carbamic acid derivatives that yield α-methylstyrene and piperidine, respectively.

Key Words: Adsorption • Dimepiperate • Hydrolysis • Infrared spectroscopy • Interlayer cations • Montmorillonite • Pesticides

Clays and Clay Minerals; June 1993 v. 41; no. 3; p. 335-340; DOI: 10.1346/CCMN.1993.0410308
© 1993, The Clay Minerals Society
Clay Minerals Society (www.clays.org)