The name is absent

Chapter 4

naphthenate adding 0.3 mM Na₂SiO₃ at pH 9.0. Compared with the second and
third bars, water-wet fraction in the sample adding silicate is larger than adding
NaOH. Silicate ion can adsorb on the positively-charged sites of kaolinite and
reduce the adsorption of naphthenate on kaolinite surface, which can make
kaolinite more water-wet. Compared with NaOH, silicate is more effective to
change the wettability of kaolinite.

4.2.3. Effect of naphthenate concentration, NaOH and Na₂SiO₃

Figure 4.4 shows water-wet fraction of 1.0 w.% kaolinite in toluene-brine
mixture (1:1, v∕v) with naphthenate adding NaOH or Na₂SiO₃ at different pH 24
hours after preparation. The red and blue bars are water-wet fractions of kaolinite
adding 100 ppm I 500 ppm naphthenate and hydroxide or silicate at different pH.
The dashed line shows water-wet fractions of kaolinite without naphthenate as
control, without NaOH or Na₂SiO₃ added.

At the same dosage of NaOH or silicate, kaolinite with 500 ppm naphthenate
is less water-wet than that with 100 ppm naphthenate. Increase of naphthenate
concentration makes naphthenate adsorption effect more significant and kaolinite
is more oil-wet. For all the samples, kaolinite becomes more water-wet as pH
increases. At higher pH, the surface of kaolinite is more negatively-charged.
Hereby the effect of naphthenate adsorption on kaolinite wettability is less

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