The name is absent

Chapter 4

kaolinite decreases as amine oxide DO concentration increases. Water-wet
fraction of kaolinite at optimal dosage of amine oxide DO is the same as the
sample without naphthenate. The optimal dosage of amine oxide DO is about 4.4
times the 1:1 stoichiometry value compared to 15 time for betaine 13 and equal
amounts for C₈TAB.

Similar to betaine, amine oxide in chemistry is a neutral chemical compound
with a positively charged cationic ammonium ion and a negatively charged
functional carbonyl group. At pH 8.3, some of amine oxide becomes positively
charged and interacts with naphthenate to form ion pairs. Hereby the optimal
dosage is larger than the 1:1 stoichiometry value. If amine oxide is overdosed, the
excess cationic type of amine oxide will adsorb on negative surfaces of kaolinite
and make them more oil-wet. Hence as amine oxide concentration increases,
water-wet fraction of kaolinite increases to maximum and then decreases.

Figure 4.13 shows water-wet fraction of 1.0 w.% kaolinite in toluene-brine
mixture (1:1, v∕v) with 100 ppm naphthenate adding C₈TAB, amine oxide DO or
betaine 13 at pH 8.3 24 hours after preparation as comparison. The two black
dashed lines show water-wet fractions of kaolinite with or without naphthenate as
control. The blue, red or green dashed line shows 1:1 stoichiometry values C₈TAB,
amine oxide DO or betaine 13 with 100 ppm naphthenate.

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