Smectite, swelling bentonite

The most significant class of inorganic supports, which is used for the direct ion exchange of positively charged transition-metal complexes, are smectite clays. Pin-navaia has introduced the use of these swelling, layered silicate clays for catalysis. Other clays include montmorillonite, bentonite, and laponite. As shown by Pinna-vaia, cationic transition-metal complexes can be readily exchanged (intercalated) into the solvated interlayers of these silicates (Eq. (1)) [117] ... 

Bentonite and hectorite clays consist primarily of hydrated aluminum and magnesium silicates, respectively. Bentonite is recognized for its swelling capacity one gram can absorb up to 11 ml of water. A commonly used smectite clay is aluminum magnesium... 

Bentonite is a mixture of clayey minerals, in which smectite is the main mineral and proved to be the most important one for swelling. The structure of smectite like montmorillonite is composed of two structural units, the silica tetrahedron and... 

Bentonite is a smectite clay, which has a lamellar stmcture. By adding water, the clay structure swells due to the adsorption of water molecules. The clay then becomes workable and can be spread to coat the sand grains during mixing. 

Smectite - The smectites are water swellable cl s having a sheet or platelet structure. Smectite is the mineralogical term for this class of clays, which includes montmorillonite, hectorite, and saponite. Montmorillonite clays derive their name from the Montmorillon section of France where this material was first observed and later classified. Most smectites are more commonly known under the geological term bentonite. By convention, a bentonite is understood to be an ore or product with a substantial smectite content. The name bentonite derives from Fort Benton, Wyoming, the site of an important deposit. Lattice substitutions within the smectite clays creates a charge imbalance which is compensated by exchangeable alkali and alkaline earth cations. This contributes to the ability of these clay to swell and impart considerable plasticity in ceramic formulations. When the exchangeable cations are predominately sodium, the individual platelets can separate to produce a colloidal structure in water. 

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