Nsutite

There are approximately 250 known manganese minerals. The primary ores which typically have a Mn content >35%, usually occur as oxides or hydrated oxides, or to a lesser extent as siUcates or carbonates. Table 5 Hsts the manganese-containing minerals of economic significance (10). Battery-grade manganese dioxide ores are composed predominately of nsutite, cryptomelane, and todorokite. 

Cell Chemistry. Work on the mechanism of the carbon—2inc cell has been summari2ed (4), but the dynamics of this system are not entirely understood. The electrochemical behavior of electrolytic (FMD), chemical (CMD), and natural (NMD) manganese dioxide is slightly different. Battery-grade NMD is most commonly in the form of the mineral nsutite [12032-72-3] xMn02, which is a stmctural intergrowth of the minerals... 

Cathode Reaction. There are many different types of manganese dioxide (18), having varying activity in batteries. The only type suitable for alkaline batteries is y-Mn02, the mineral form of which is nsutite. The chemical composition of has been described (19) by the general formula... 

Nsutite Vernadite 8-Mn02 Intergrowths of single and double chains of... 

Turner, S. Buseck, P. R. (1983) Defects in nsutite (y-Mn02) and dry-cell battery efficiency. Nature, 304,143-6. 

Parc, S., D. Nahon, Y. Tardy, and P, Vieillard. 1989. Estimated solubility products and fields of stability for cryptomelane, nsutite, bimessite, and Iithiophorite based on natural lateritic weathering sequences. Am. Miner. 74 466-475. 

Manganese(lV) oxide exists in many modifications. The only modification which approaches a stoichiometric composition is p-MnOy (e.g. the mineral pyrolusite) and it is the least reactive. All the other modifications contain additional cations, such as Na+, K", Ca- and Ba ", anions, such as OH, and water. The average valency stale of the manganese is also less than 4 (down to, 1.4). The almost amorphous y-MnO (the mineral nsutite) is particularly reactive. 

This paper describes the catalytic activity of various forms of manganese dioxides towards volatile organic compounds deep oxidation. Important differences in activity are evidenced for very closely related structures the most active sample is a high surface area nsutite. A parallel is drawn between the findings in the literature of battery applications and the catalytic activity results. The superior activity of nsutite is attributed to a different oxygen coordination and to the clustering of cationic vacancies in the bulk which improves electronic and protonic conductivity. 

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