Isothermal Adsorption of Aflatoxin B1 on HSCAS Clay

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Abstract
Previously, hydrated sodium calcium aluminosilicate (HSCAS), a phyllosilicate clay of the smectite class, was shown to tightly bind aflatoxins and prevent aflatoxicosis in animals. HSCAS is a commercial feed additive that is approved to be used as an anticaking agent. In this study, aflatoxin B1 (AfB1) was isothermally mixed with HSCAS at 15, 25, and 37 °C to study the adsorption process. An L adsorption isotherm was characterized from the data, which were fitted to multiple isotherm equations (i.e., Langmuir, multi-Langmuir, general Freundlich, Langmuir−Freundlich combination, Toth, and various transforms of these equations). Information derived from the isotherm equations included capacity, affinity, average capacity, enthalpy of binding, heterogeneity coefficient, multiple site distribution coefficients, and a multisite capacity. Physical characteristics of AfB1 and HSCAS were measured and modeled to further the understanding of the adsorption process. The data obtained support the hypothesis that AfB1 chemisorbs to different sites on HSCAS which could include the interlamellar region, edges, and basal surfaces of HSCAS particles. Keywords: Adsorption; aflatoxin; binding; clay; detoxification; HSCAS; isotherm; smectite