Kinetics of isotopic exchange of sodium ions in hydrous manganese dioxide from mixed solvent solutions

✍ Scribed by H.F. Ghoneimy

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 569 KB
• Volume: 96
• Category: Article
• ISSN: 0167-2738
• DOI: 10.1016/s0167-2738(96)00604-2

✦ Synopsis

The Na' capacity of cryptomelane type-hydrous manganese dioxide in aqueous, methanolic and propan-I-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 (B) of sodium ions in manganese dioxide have been determined in aqueous and alcoholic (methanolic and propan-I-olic) solutions by using Paterson's approximation equation. These coefficients (B) 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 (0). 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.