Adsorption of acetanilide herbicides on soil and its components
II. Adsorption and catalytic hydrolysis of diethatyl-ethyl on saturated Na^+-,
K^+-, Ca²^+-, and Mg²^+-montmorillonite
Affiliations: Institute of Environmental Science, Zhejiang
University at Yuquan Campus, Hangzhou 310027, China; E-mail:
wpliu@mail.hz.zj.cn | Institute of Industry Environmental Design,Zhejiang
Province,Hangzhou 310005,China
Abstract: Adsorption and catalytic hydrolysis of the herbicide diethatyl-ethyl
[N-chloroacetyl-N-(2,6-diethylphenyl)glycine ethyl ester] on homoionic Na^+-,
K^+-, Ca²^+-, and Mg²^+-montmorillonite clays were investigated in
water solution. The Freundlich adsorption coefficient, K_f, got from isotherms
on clay followed the order of Na^+ ≈K^+ > Mg²^+
≈Ca²^+. Analysis of FT-IR spectra of diethatyl-ethyl adsorbed on
clay suggests probable bonding at the carboxyl and amide carbonyl groups of the
herbicide. The rate of herbicide hydrolysis in homoionic clay suspensions
followed the same order as that for adsorption, indicating that adsorption may
have preceded and thus caused hydrolysis. Preliminary product identification
showed that hydrolysis occurred via nucleophilic substitution at the carboxyl
carbon, causing the cleavage of the ester bond and formation of diethatyl and
its dechlorinated derivative, and at the amide carbon, yielding an ethyl ester
derivative and its acid.These pathways also suggest that hydrolysis of
diethatyl-ethyl was catalyzed by adsorption on the clay surface.
