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A first step in refining traditional holistic models is to In this paper, the acid-base properties of illite/water suspen-isolate and analyze the surface reaction mechanisms of difsions are examined using the constant capacitance surface com-ferent components in natural particles. Of particular interest plexation model. On the basis of results of potentiometric titrations are clays, since they are the dominant components in natural and solubility experiments, we conclude that the proton reactions minerals. As to what has already been done in this area, and montmorillonite (a 2:1 layer-type clay mineral). For the Evaluation of these two models indicates that both of them cangive good descriptions of the experimental data of systems with study of kaolinite (8), in addition to the amphoteric surface different illite concentrations and ionic strengths and that the one hydroxyl group, GSOH, they postulate a second surface site-one pK a model can be considered as a simplification of the functional group, GXH, which is weakly acidic and can two sites-two pK a s model. Since both models assume only depro-undergo ion exchange with cations from the background tonation reactions at the illite surfaces, they suggest that the sur-electrolyte. For the study of montmorillonite (9), besides face behavior of the illite is similar to that of amorphous SiO 2 .GSOH and GXH, another surface hydroxyl group GTOH, Model assumptions, experimental procedures, and evaluative cri-which undergoes one deprotonation reaction, is incorporated teria are detailed in the paper. ᭧ 1997 Academic Press to evaluate the surface acid-base behaviors. Wieland and

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Adsorption of diphenyl-, phenyl-and orthophosphate on γ-Al2O3 was studied with a combination of macroscopic and 31 P solid-state NMR measurements. Results for adsorption suggest that diphenyl phosphate was bound largely as an outer-sphere complex, while phenyl phosphate was held largely as inner-sphere surface complexes with an outer-sphere complex present only at higher pH values. Both the adsorption edge and the cross polarization magic angle spinning NMR spectra were consistent with the interaction between the surface and phenyl phosphate being driven by electrostatic forces. Adsorption of orthophosphate was more complex, with evidence of outer-and inner-sphere complexes and surface precipitation. Increasing the orthophosphate concentration and equilibration time tended to increase the fraction bound as a surface precipitate.