Isomorphous substitution beidellite

In montmorillonite some of the Al3 + in the octahedral sublattice are replaced by Mg2+ ions, and in hectorite some of the Mg2 + in the octahedral sublattice are replaced by Li+ ions. With beidellite and saponite, however, the isomorphous substitution takes place in the tetrahedral sublattice with Al3 + replacing some of the Si4+ ions. The residual negative charges in the layers on montmorillonite, hectorite, beidellite, and saponite are counterbalanced in the natural state by coexisting interlamellar, hydrated cations, usually Na+,... 

As indicated in Table 1, the three 2 1 groups differ from one another in two principal ways. The layer charge decreases in the order illite > vermiculite > smectite, and the vermiculite group is further distinguished from the smectite group by the extent of isomorphic substitution in the tetrahedral sheets. Among the smectites, those in which substitution of Al for Si exceeds that of Fe2+ or Mg for Al are called beidellite, and those in which the reverse is true are called montmorillonite. The sample chemical formula in Table 1 for smectite thus represents montmorillonite. In any of these 2 1 clay... 

Figures 1 and 2 are snapshots of equilibrium interlayer configurations, based on MC simulations (27), in Li-beidellite (Lio75[Si7 25AlQ75]Al402o(OH)4), which has isomorphic substitutions only in its tetrahedral sheets, and in Li-hectorite...

Pyrophyllite, muscovite, margarite, beidellite, montmorillonite, illites MM lattice minimization (based on empirical potentials) Geometry, effect of isomorphic substitution 131... 

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