Behavior of quaternary ammonium ions in the desorption of [Coen 3] 3+ from H-Coen 3-Bentonite

Abstract

Desorption studies of [Coen 3] 3+ from its bentonite complex show that tetraethyl ammonium halides are much more effective than tetramethyl ammonium halides at lower concentrations (up to 6 × 10 −2 M); the extent of desorption with tetraethyl ammonium halides at higher concentrations is either equal to or less than that with tetramethyl ammonium salts. This irregular behavior of tetraethyl ammonium halides may be attributed to their lower activity at relatively higher concentrations. The behavior of cetyl trimethyl ammonium bromide (CTABr) and cetyl pyridinium chloride (CPC1) at lower concentrations is almost identical with that of tetraethyl ammonium halides, but at larger concentrations CTABr and CPC1 appear to show smaller desorption, which may, however, be explained by the covering-up effect of the larger ions; a fraction of the [Coen 3] 3+ is inaccessible for the exchange process. Again CP +, having a smaller cmc than CTA +, is more effective in desorbing the complex ion than the latter. The anions seem to have some specificity in the desorption process, for example, the iodides have been found to be more effective than other halides. The desorption of [Coen 3] 3+ with tetramethyl and tetraethyl ammonium iodides has been analyzed in the light of the theoretical approach of Barrer, and thermodynamic quantities of interest have been evaluated.