Investigations have been carried out to compare the acidity of surface sites on chromium dioxide and γ-iron oxide magnetic particles. Measured heats of adsorption and adsorption densities of pyridine show that surface sites on CrO2, are more heterogeneous and more acidic than surface sites on γ-Fe2O3. Experimental results indicate that monolayer coverage of pyridine, approximately 5.0 μmol m-2, is attained on CrO2 at a solution concentration of approximately 35 mM. Application of the Freundlich isotherm to experimental results is discussed.
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