The name is absent

Chapter 4

negative. Thus zeta potential change per unit addition in synthetic brine with Ca/

Mg (20 mV∕mM) is greater than that in the brine without Ca/ Mg (15 mV∕mM).

4.3.5.6. Effects of silicates

Silicate has two effects on the zeta potential of kaolinite. Adding silicate can

increase the pH of the brine, which can make zeta potential of kaolinite more

negative. Silicate can also adsorb on the positively charged sites -AOH₂⁺, which

can also make zeta potential of kaolinite more negative.

In synthetic brine, positively charged sites -AOH₂⁺ can adsorb HSiO₃' or

H₃Siθ4^- ion and become neutral sites. Eqs. [4.42] - [4.47] give the surface

reaction and equilibrium equation. Here only the adsorption of HSiO₃' or H₃Siθ4'

ion is considered, because the concentration of monovalent ion is much higher

than other silicate ions with higher valency.

-AOH₂ +HSiO₃ f÷ -AOH₂HSiO₃

[4-42]

[AOH₂HSiO₃]

[AOH₂HSiO₃]

^hsi°³ [AOH₂ X (HSiO₃) [AOH₂ ]<¾ (HSiO₃ )exp(-)

kT

[4.43]

σ₀=e([AOH÷]-[AO']-[B])

[4.44]

-AOH₂+H₃SiO₄ 4≡ -AOH₂H₃SiO₄

[4.45]

[AOH₂H₃SiO₄]

[AOH₂H₃SiO₄]

^H’^s-°< [AOH₂ ]tzʃ (H₃SiO₄) _tAOH⅛(H₃SιO₄)exp(⅛
Kl

[4.46]

σ₀ =e([AOH₂]-[AO']-[B])

[4.47]

138