The name is absent

Chapter 4

amphoteric groups -AOH (A can be Al or Si) and permanent negatively charged

sites -B'. Here silica sites and alumina sites are considered to have the same
electrostatic interactions with counter ions. Amphoteric groups -AOH (-AIOH and
-SiOH) are pH dependent, and can form either positively charged sites -A0H₂⁺,
or negatively charged sites -AO'. Positively charged sites -AOH₂⁺ can adsorb
anions. Negatively charged sites -AO' can adsorb cations.

Eqs. [4.10] and [4.11] show the dissociation equilibrium Ofamphoteric groups
-AOH and the equilibrium equation.

-AOH -AO'+ H⁺, A: AlorSi [4.10]

_ [AO ]α (H⁺) _ [AO ]⅝(H∙)exp(-≤)
A —-------------—------------------------ ⅜. I Il

[AOH] [AOH]

K : surface reaction or surface adsorption equilibrium constants.

a_s and Sb- activity at surface and in the bulk.

Eq. [4.12] shows the surface adsorption equilibrium of Ca²⁺ on negatively
charged groups -AO'. Eq. [4.13] shows the equilibrium equation.

-A0^+Ca²⁺ -AOCa⁺, A: Al or Si [4.12]

K_{α =} [≡1 ₌----lʌθɑn [₄.₁₃]

[A0]¾(Ca ) [AO¾(Ca²⁺)exp(⅛

Table 4.4 shows equilibrium of different surface reactions.

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