Chapter 4
significant at higher pH and kaolinite is more water-wet. At the same pH, adding
silicate can make kaolinite more water-wet than adding NaOH. NaOH only has
caustic effect to increase pH. For silicate, besides caustic effect, adsorption of
silicate ion on kaolinite positively-charged sites can make the surface of kaolinite
more negatively-charged and make kaolinite become more water-wet.
100
Wettability test
80
60
40
20
Control 24 ppm NaOH 37 ppm silicate 200 ppm NaOH 366 ppm silicate
Figure 4.4 Water-wet fraction of kaolinite with different amount of naphthenate
adding NaOH/ Na2SiO3 at different pH
Figure 4.5 shows water-wet fraction of 1.0 w.% kaolinite in toluene-brine
mixture (1:1, v∕v) with 100 ppm naphthenate adding NaOH/ Na2SiO3 at different
pH 24 hours after preparation. Kaolinite becomes more water-wet as pH
95