PLSC204 Lecture Notes - Lecture 19: Vermiculite, Montmorillonite, Illite
28 Jan 2019
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Document Summary
The only negative charges are ph dependent and occur at the edges of sheets. Very low shrink-swell capacity due to strong hydrogen bonding between sheets. External surface area only - edge surface areas, area on top on layer and layer on bottom. Layers interior are not available for chemical reactions because they are held together by hydrogen bonding so can not. 2 octahedral layers per 1 tetrahedral layer. Isomorphous substitution in the octahedral layer gives rise to permanent net negative charge. Very high shrink-swell capacity due to weak bonding between sheets which allows water and large ions (e. g. , na + ) to enter. Layers not bound tightly, water and other ions can get in between of irons of the clay - more surface area than kaolinite since surface area in between layers also count. Isomorphous substitution in both the tetrahedral and octahedral layer gives rise to high permanent net negative charge.
