Chapter 4
decrease; the fraction of negatively charged sites -AO' will increase. At pH 8 - 9,
almost all silica sites are negatively charged; for alumina site, the fraction of
positively charged site is higher than negatively charged site.
Table 4.8 Kaolinite surface site densities and dissociation constants
|
Reaction |
K (mol∕m3) |
N ( W8 mol∕m2) |
|
-aioh; ≠-AlOH+H+ |
2.86×10^8 |
18.5 |
|
-AlOH -AlO+ H+ |
3.33×10'1° | |
|
-SiOH^ f≡-SiOH +H+ |
5.03×10^4 |
4.83 |
|
-SiOH f≡-SiO + H+ |
5.16×10^6 | |
|
Inert sites |
21.6 |
Figure 4.19 Silica sites fraction in kaolinite at different bulk pH in 0.05 M NaCI
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