Über Oxidhydroxide des Mn(IV) mit Schichtengitter. 5. Mitteilung: Stöchiometrie, Austauschverhalten und die Rolle bei der Bildung von Tiefsee-Mangankonkretionen

Abstract

The synthesis, chemical analysis and reactions in hot diluted acid as well as ion exchange with Cu, Co, Ni, Zn, Ca and Mg of Na-10Å-Manganate (≙ synth. Buserite) and of Na-7Å-Manganate (≙ synth. Birnessite) confirm that both groups of compounds consist of 2-dimensional anionic manganate main layers with vacancies. For compensation there are cation positions in the intermediate layers which are exchangeable. The marked preference for transition metal ions like Cu, Co, Ni, Zn leads to stabler varieties within both groups compared with the Ca-, Mg-, and Na-varieties. Parallel experiments with synthetic psilomelane show a qualitative similarity between the two groups investigated and so-called “todorokite” of natural origin while synthetic psilomelane does not react with HNO₃. The proposed tunnel structure similar to the psilomelane lattice can therefore be discarded for the buserite group and we conclude that “todorokite” is the misnomer for a mineral association of the buserite group with other Mn minerals and admixtures. The results explain the existence and the formation of two types of deep-sea nodules and nodule forming material.