The name is absent

between the clean oil and free water layers. Partially oil-wet clay solids prevent
complete separation of the emulsion.

Experiments reveal that wettability of clay solids has significant effect on
emulsion stability. Kaolinite with 100 ppm sodium naphthenate in toluene-brine
mixture is chosen as model system for wettability test. Wettability of kaolinite can
be altered by pH control, silicate and surfactant. Adding 3×10^³ M Na2SiO3 at pH
10 can get 80% of kaolinite water-wet. Over 90% of kaolinite becomes water-wet
adding CsTAB, betaine 13 and amine oxide DO with optimal dosages. In diluted
bitumen emulsion, about 10^⁴ M sodium meta-silicate can change the wettability
of solids from partially oil-wet to more water-wet. Hereby the clay solids can
settle down to the aqueous phase and the separation is almost complete.

Wettability of kaolinite can be characterized via zeta potential measurement
and modeling. Simplified Gouy-Stern-Grahame model and oxide site-binding
model can be used to correlate zeta potential of kaolinite in brine with different
additives. Sodium silicates have the greatest effect per unit addition on changing
zeta potential of kaolinite and can be used to change the wettability of clay solids.

Almost complete separation be obtained by the three-step procedure: (a)
adding 10^⁴ M Na₂SiOa during initial emulsion formation to make the solids less
oil wet; (b) removing the clean oil formed following subsequent treatment with
demulsifier and adding NaOH or Na₂SiO₃ with shaking to destroy the rag layer
and form a relatively concentrated oil-in-water emulsion nearly free of solids; and
(c) adding hydrochloric acid to break the oil-in-water emulsion.

ii

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