pH-dependent, multisite, surface charge on kaolinite can be explained by proton donor–
acceptor reactions occurring simultaneously on Si and Al sites exposed on basal planes and
edges. Si site Brønsted acidity at the kaolinite–solution interface differs minimally from that of
pure SiO2, whereas Al site acidity increases appreciably over that of pure Al2O3. Increasing
temperature decreases the pKvalues of Al and Si proton-exchange sites. Calculated site
densities indicate either an elevated participation of edges or substantial contribution from …

pH-dependent multi-site kaolinite surface charge can be explained by proton donor-
acceptor reactions occurring simultaneously on Si and Al sites exposed on edge sites. Si
site acidity at the kaolinite-solution interface differs minimally from that of pure SiO {sub 2},
whereas Al sites became appreciably more acidic when a part of the kaolinite matrix.
Independent evidence from scanning force microscopy points to a higher percentage of
edge surface area due to thicker particles and basal surface steps than previously assumed …