The name is absent

Chapter 6

kaolinite more oil-wet. Wettability of kaolinite doesn’t change much if betaine 13 is
overdosed (200 -1000 ppm).

Kaolinite in clay solids has heterogeneous surface charge, which affects its
wettability. Zeta potential measurement is used to characterize wettability change
of kaolinite. Calcium and magnesium ions in the aqueous solution can make the
zeta potential of kaolinite in brine less negative. Adding NaOH, meta-silicate,
ortho-silicate, citrate or carbonate can make the zeta potential of kaolinite in brine
more negative. Compared with other anions, silicate ions have the greatest effect
per unit addition on changing zeta potential of kaolinite.

Simplified Gouy-Stern-Grahame model and oxide site-binding model can be
used to correlate the zeta potential of kaolinite in brine with different additives.
Different additives have various surface reactions with kaolinite, which can
change the zeta potential of kaolinite in brine. Adding NaOH can increase the pH;
hydroxyl ion can react with the surface group of kaolinite, which will make zeta
potential more negative. Sulfate ion and bicarbonate ion can adsorb on the
surface of kaolinite and make zeta potential more negative. Calcium and
magnesium ions can adsorb on the surface of kaolinite and make zeta potential
less negative. Silicate can adsorb on the surface of kaolinite, in addition to raising
the pH. Citrate ion can both adsorb on the surface of kaolinite and chelate with

191

<<   204   205   206   207   208   209   210   >>

More intriguing information