2. Clay

2.1 Common features

The most common clays are phyllosilicates or smectites. Their main characteristic is their nanometre-thick crystalline sheet structure (and consequent high form factor), which gives them a high specific surface area. Generally speaking, clays contain impurities such as quartz...

The classification of clays is defined not only by their crystalline structure, but also by the quantity and position of ions within the unit cell. The main classes range from kaolins, with a uniform chemical composition, to smectites, with highly variable compositions and cation exchange capacities. The spacing between individual sheets is governed by the presence of cations in the interfoliar space.

It should be noted that there are also...