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Chapter 4

w.% NaCI brine at pH 6.8 (sample 2 in chapter 3). Sample 3 is the emulsion with
clay solids using diluted bitumen and synthetic brine (2.5×10^² M NaCI, 1.5×10^² M
NaHCO₃, 2×10^³ M Na₂SO₄, 2×10'⁴ M CaCI₂ and 2×10^⁴ M MgCI₂) at pH 8.3.
Sample 4 is the emulsion with clay solids using synthetic brine adding 1×10'⁴ M
Na₂SiO₃ at pH 8.5.

In the absence of clay solids, the separation of the emulsion is almost
complete after adding PR₅ at pH 6.8 (sample 1 ). If the emulsion contains clay
solids (sample 2), addition of PR₅ results in coalescence of water drops, but the
clay solids remain as rigid skins dispersed in water. The photomicrographs show
that the bottom of oil-continuous phase is water-in-oil emulsion and the top of
water-continuous phase contains clay solids skins. Instead of settling to the
bottom, the clays, which are partially oil-wet, entrap oil to form skins with
intermediate density, which stay in the middle between oil and water layers.
Increase of pH from 6.8 (sample 2) to 8.3 (sample 3) can obtain better separation,
but a rag layer still forms in the middle. Adding Na₂SiO₃ at pH 8.5 (sample 4) can
get almost complete separation except for a thin rag layer in the middle.

Comparing samples 1 and 2, clay solids can make emulsion more stable and
prevent the complete separation of oil and water. Comparing samples 2 and 3,
increasing pH can enhance emulsion separation. Comparing samples 3 and 4,

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