Phase transitions and ion exchange behavior of electrolytically prepared manganese dioxide
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Manganese dioxides were prepared electrolytically in the temperature range 10-95°C. The oxides prepared at 25°C or lower exhibited a high ion exchange capacity equivalent to one proton per two Mn atoms. Those prepared at higher temperatures exhibited correspondingly lower capacities and the 95°C preparation showed only surface exchange. The Li+ exchanged solid formed a spinel LiMn2O4 on heating and was converted to HMn2O4 on treatment with dilute acid. The protonated solid retained the spinel structure and showed a high specificity for Li+. A corresponding sodium ion exchanged phase yielded a birnessite-like phase on heating followed by treatment in boiling water. The sodium ion was exchanged with acid to yield a layered compound of composition H4Mn9O18 · 7H2O. It is suggested that λ-MnO2 and Mn7O13 are deprotonated versions of the hydrogen ion exchanged species. It is further suggested that similar exchange reactions with insertion type compounds should lead to new types of inorganic ion exchangers. © 1986.
author list (cited authors)
Shen, X., & Clearfield, A.