The name is absent

Chapter 4

adding silicate can yield even better separation and reduce the rag layer. The
separation result of sample 4 is better than sample 2, but worse than sample 1.
This indicates increasing pH and adding silicate can change the properties of clay
solids, which will reduce the stabilization effects of clay solids on the emulsion.

Most of the clay solids in Athabasca bitumen are kaolinite and illite ^[1].
Kaolinite in clay solids has heterogeneous surface charge ^pl and will present
heterogeneous wettability when contacting with crude oil. This is very important to
the emulsion stability. Kaolinite is finely divided crystalline aluminosilicate. The
principal building elements of the clay minerals are two-dimensional arrays of
silica layers and alumina layers. Sharing of oxygen atoms between silica and
alumina layers results in two-layer mineral ^[2]. Kaolinite has permanent negative
charge sites on the basal planes owing to the isomorphic substitution of the
central Si and Al ions in the crystal lattice by lower positive valence ions ^[2H5].
AI-OH and Si-OH groups are exposed on hydroxyl-terminated planes. The
amphoteric sites are conditionally charged, either positive or negative, depending
on the pH. Positive charges can develop on the alumina faces and at the edges
by direct H⁺∕OH" transfer from aqueous phase ^{[3L [4]}.

The point of zero charge (PZC) of amphoteric (mainly edge) sites, ranges
from pH 5 to 9 depending on the kaolinite used ^[2]. PZC is determined by titration.

88

<<   101   102   103   104   105   106   107   >>

More intriguing information