Environmental Engineering Reference
In-Depth Information
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Limonite: amorphous iron hydroxide;
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Bauxite: amorphous aluminium hydroxide.
They are common in tropical residual soils and soils derived from volcanic ash.
7.2.2
Bonding of clay minerals
The properties of clays, particularly in a soil-water environment, are determined by the
nature of the atomic bonding between the atoms which make up the sheets of clay
mineral, and the bonding between the sheets of clay mineral. The bonding mechanisms
which are present includes primary bonds and secondary bonds.
OH
OH
OH
Si
Al
Si
Si
nH
2
O layers and
exchangeable cations
nH
2
O layers and exchangeable cations
0.96 nm
Al
Si
Si
Al
Si
Oxygens
OH
Hydroxyls
Aluminum, iron, magnesium
and
Silicon, occasionally aluminum
Atomic structure of motmorillonite
Schematic diagram of the structure of montmorillonite
OH
OH
OH
OH
OH
Al
Si
Al
0.72 nm
Si
Al
OH
Si
Oxygens
Hydroxyls
Aluminums
Silicons
OH
OH
OH
OH
OH
OH
Atomic structure of kaolinite
Figure 7.3.
Structure of montmorillonite and kaolinite (Holtz and Kovacs, 1981, reproduced with per-
mission of Pearson Education).
