Adsorption of Zearalenone by Organophilic Montmorillonite Clay

Abstract

Acidic montmorillonite clay was chemically modified via exchange with various ammonium- and pyridinium-based organic cations. These organo clays were then shown to adsorb zearalenone (ZEN) with an efficacy related to the exchanged cation hydrophobicity, as gauged by estimated critical micelle concentration values (cmc) and length of the alkyl chain. ZEN adsorption was greatest for clay samples that had been modified by interlayer exchange with cations possessing 16-carbon alkyl chains: hexadecyltrimethylammonium (HDTMA) and cetylpyridinium (CP). Isothermal analysis of ZEN adsorption (at 37 °C, pH 6.5) indicated that the clay exchanged with CP at a level of less than or equivalent to the cation exchange capacity (CEC) binds ZEN primarily by a partition process. In contrast, clay exchanged at the 1.5 CEC level gave an S-shaped curve with at least two plateaus, suggesting additional mechanisms of adsorption. A capacity (Qmax) and distribution coefficient (Kd) for the first site were estimated. At acid pH, t...