Abstract

Acidic properties of dialyzed alumina and representative clay minerals were studied by performing titrations with various bases. For the first group of experiments the titrations were made in a water system using KOH and NaOH. For this study in a water system the experimental data includes individual cationic activities as well as pH values. Adsorption of the cations was adequately described over a pH range of 5-11 by the equation 1-θ/θ ⋅ aNa+ ⋅ aOH- = 1/K'3 [aOH- + KW/K'2 + 1/K'1], in which θ represents the fraction of the total sites that have reacted. Thermodynamic constants K'3 and K0= KW/K'2 + 1/K'1 of this equation were calculated. In the second group of experiments a higher pH range was attained by making the titrations with NaCC2H3 in absolute ethanol. Interpretation of this data by use of a Langmuir-type equation revealed two fairly homogeneous types of acid sites for each mineral. It was also possible to calculate the apparent equilibrium constants of the various reaction sites involved. A discussion of possible mechanisms for two acid sites on these minerals is given.

Degree

College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry

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