Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 2/1/1996
Publication Date: N/A
Citation: Interpretive Summary: Not required.
Technical Abstract: Knowledge of the surface chemical behavior of aluminum oxides and hydroxides is still advancing. More is known in terms of systematic laboratory studies about the synthetic material,gamma-Al2O3, than any other phase. The results of experimental studies of the gibbsite surface are consistent with what is expected in terms of the exposure of different crystal faces as predicted from the crystal structure. Little is known regarding the effects of surface alteration on the observed surface chemical behavior. More systematic and comprehensive studies of gibbsite are needed. Recent advances, such as the measurement of surface potential as a function of pH and studies of the specific adsorption of counterions such as Na+ and Br-, are affecting dramatically the evolution of models for the alumina-water interface. However, models for the adsorption of solutes from dilute solutions have not yet been combined in a consistent way with spectroscopic studies of the surface. Much more research also is needed on the kinetics of adsorption reactions, the determination of maximum adsorption densities, the stoichiometry of surface reactions, and the ionic strength dependence of adsorption reactions. Although model development and the experimental studies conducted to date represent a considerable increase in knowledge, quantitative application of this knowledge to the natural environment still appears problematic. Furthermore a greater understanding of the role of adsorption in the precipitation process and the rates at which the surfaces of metastable minerals are altered by reorganization is required to improve geochemical models.