Calcium Bentonites: Characteristics and Distribution as Adsorbents of Aflatoxin.

The term bentonite commonly addresses Na bentonites but recent interest in Ca bentonites has increased as they have performed as better adsorbents of the aflatoxin B1 molecules, well known by its harmful effects on animals and humans. This has increased the importance for the control the mycotoxin in animal feeds and currently of increasing interest in human foods. A recent electron microcopy report of a structural basis for smectite selection based on lattice fringes and frayed ends of smectite particles indicate accessibility to aflatoxin in contrast to low adsorption of opaque tabular smectite particles that are poor adsorbents of the mycotoxin. More silt than clay in Ca bentonite adsorbents was attributed to porous smectite aggregates inherited from the bentonite rock. The best aflatoxin adsorbents were Ca bentonites that had frayed edges and ends with folds and translucent interior porosity. There is a current need to determine the conditions for formation and occurrence of Ca bentonites. The effectiveness of bentonite adsorbents is based on accessibility of aflatoxin to interlayer spaces of Ca bentonite. The persistence of aggregates of silt size as the dominant size in a native porous state can be attributed to the Ca in the bentonite rock. This report examines the hypothesis that Ca in bentonites contributes in two ways by reducing the dispersion and provides a favorable interlayer spacing for adsorption of the mycotoxin.