Bentonites: Adsorbents of toxic substances

Abstract

The use of bentonites as adsorbents results from the reactivity of montmorillonite which is the main mineral in this clay-like material. Montmorillonite, a 2:1 clay mineral, impresses by a diversity of reactions in the interlayer space and at the external surfaces, which are the cause of strong adsorption of heavy metal ions and organic compounds. Bentonite adsorbents are used as crude bentonite, in soda-activated form, after degradation to bleaching earths, after modification by organic cations, or in form of polyhydroxometal or polyoxometal derivatives (`pillared clays'). The ease with which the bentonites are modified allows an optimization of the properties so that the requirements of numerous practical applications are fulfilled.