Chapter 4
can accept a hydrogen ion and becomes positively charged. The ratio of this type
of cation depends on the association equilibrium constants and pH. At pH 8.3,
only a small amount of betaine becomes positively charged and interacts with
naphthenate to form ion pairs. Hence the optimal dosage is larger than the 1:1
stoichiometry value.
Caprylamidopropyl betaine (ppm)
Figure 4.9 Water-wet fraction of kaolinite with 100 ppm naphthenate adding
different amount of betaine 13 at pH 8.3
Figure 4.10 shows water-wet fraction of 1.0 w.% kaolinite in toluene-brine
mixture (1:1, v∕v) adding different amount of betaine 13 at pH 8.3 24 hours after
preparation, without naphthenate added. Similar to CsTAB, water-wet fraction of
103