Sorption and catalytic hydrolysis of diethatyl-ethyl on homoionic clays

Sorption and catalytic hydrolysis of the herbicide diethatyl-ethyl [N-chlor oacetyl-N-(2,6-diethylphenyl)glycine ethyl ester] on homoionic Na+-, K+-, C a2+, and Mg;(2+)-montmorillonite clays were studied in aqueous media. The F reundlich sorption coefficient, K-f, measured from isotherms on clay follow ed the order of Na+ approximate to K+ > Mg2+ approximate to Ca2+. Analysis of FT-IR spectra of diethatyl-ethyl sorbed on clay suggests probable bondin g at the carboxyl and amide carbonyl groups of the herbicide. The rate of h erbicide hydrolysis in homoionic clay suspensions followed the same order a s that for sorption, indicating that sorption may have preceded and thus ca used hydrolysis. Preliminary product identification showed that hydrolysis occurred via nucleophilic substitution at the carboxyl carbon, causing clea vage of the ester bond and formation of diethatyl and its dechlorinated der ivative, and at the amide carbon, yielding an ethyl ester derivative and it s acid. These pathways also suggest that hydrolysis of diethatyl-ethyl was catalyzed by sorption on the clay surface.