Molecular controls on kaolinite surface charge and organic acid adsorption

Conference · Tue Oct 01 04:00:00 EDT 1996

OSTI ID:370496

Brady, P V; Cygan, R T; Nagy, K L; Ward, D B ^[1]

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1. Sandia National Labs., Albuquerque, NM (United States)

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. Molecular modeling of the proton-relaxed kaolinite structure has been used to establish the elevated acidity of edge Al sites, to independently confirm the crystallochemical controls on surface acidity, and to establish likely bonding geometries for adsorbed organic acids, such as oxalate.

• Research Organization: Sandia National Laboratory
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 370496
• Report Number(s): CONF-960376--
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
54 ENVIRONMENTAL SCIENCES
ADSORPTION
ALUMINIUM SILICATES
ENVIRONMENTAL TRANSPORT
KAOLINITE
ORGANIC ACIDS
PH VALUE
POLLUTANTS
SILICATE MINERALS
SOILS
SORPTIVE PROPERTIES
SURFACE AREA
SURFACE PROPERTIES