Abstract
The Na + capacity of cryptomelane type-hydrous manganese dioxide in aqueous, methanolic and propan-1-olic solutions was determined using two different methods. The Na + capacity decreases reprogressively with alcohol. This pointed to an imbibition of alcohols by the solid. Self-diffusion coefficients (D¯) of sodium ions in manganese dioxide have been determined in aqueous and alcoholic (methanolic and propan-1-olic) solutions by using Paterson's approximation equation. These coefficients (D¯) generally increase with alcohol concentration. The effect of alcohol addition on ion-solvent interactions is counteracted by the effect of ion-ion interactions in the exchanger, leading to an increase of (D¯). Also, adding NaCl to the external aqueous or alcoholic hydroxide solution enhances Na + diffusivity due to a weaker interaction with Cl − coions inside the oxide pores, or it may be that the addition of NaCl decreases the imbibition of alcohol by the oxide.
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