Manganese oxide minerals: Crystal structures and economic and environmental significance

Abstract

Manganese oxide minerals have been used for thousands of years-by the ancients for pigments and to clarify glass, and today as ores of Mn metal, catalysts, and battery material. More than 30 Mn oxide minerals occur in a wide variety of geological settings. They are major components of Mn nodules that pave huge areas of the ocean f loor and bottoms of many fresh-water lakes. Mn oxide minerals are ubiquitous in soils and sediments and participate in a variety of chemical reactions that affect groundwater and bulk soil composition. Their typical occurrence as fine-grained mixtures makes it difficult to study their atomic structures and crystal chemistries. In recent years, however, investigations using transmission electron microscopy and powder x-ray and neutron diffraction methods have provided important new insights into the structures and properties of these materials. The crystal structures for todorokite and birnessite, two of the more common Mn oxide minerals in terrestrial deposits and ocean nodules, were determined by using powder x-ray diffraction data and the Rietveld refinement method. Because of the large tunnels in todorokite and related structures there is considerable interest in the use of these materials and synthetic analogues as catalysts and cation exchange agents. Birnessite-group minerals have layer structures and readily undergo oxidation reduction and cation-exchange reactions and play a major role in controlling groundwater chemistry.

Manganese transport in eukaryotes: The role of DMT1

“…Oxides, carbonates and silicates are the most important Mncontaining minerals (Post, 1999). Depending on its oxidation state, Mn is utilized in countless industrial processes, such as the production of dry cell batteries, steel (Post, 1999; Saric, 1986), fuel oil additives and antiknock agents (Pfeifer et al, 2004;Ressler et al, 1999;Rollin et al, 2005).…”

Structural characterization of terrestrial microbial Mn oxides from Pinal Creek, AZ

“…Natural marine and soil Mn oxides frequently have been reported to be poorly crystalline and to exhibit layer structures (Post, 1999;Manceau et al, 2005;Bodei et al, 2007). It is likely that such morphologies implicate biogenic origin.…”

“…It can thus be concluded that this nanoparticulate layered structural motif is characteristic of (but not necessarily unique to) laboratory biogenic Mn oxides. These conclusions lead one to question if environmental biogenic Mn oxides exhibit such characteristics (intriguingly, such features are frequently reported for poorly crystalline natural Mn oxides of possible biogenic origin (Post, 1999;Manceau et al, 2005;Bodei et al, 2007)). Establishing similarity between laboratory and environmental biogenic Mn oxides, were it to occur, would represent a significant step forward because it would provide the scientific basis to model the behavior of environmental Mn oxides based on data from laboratory studies.…”

Longitudinal and contemporaneous manganese exposure in apartheid-era South Africa: Implications for the past and future

“…Demographically these residents are more likely to be white residents of the urban core, or black South Africans working in domestic settings within the urban core or within the central business district. Most critically, manganese emitted from crustal (soil) sources such as ferromanganese smelting and mining tend to be found in more coarse particulate matter (PM 10 ) and found in the environment as inorganic manganese or manganese oxides (Post, 1999) and may not be as widely as manganese found in fine particulate matter (PM 2.5 ). Manganese from tail pipe emisssions and other combustion activities is generally found in fine PM and as manganese phosphate or sulfate which which may result in greater neurotoxicity in humans than inorganic manganese or manganese oxide exposure from ferromanganese smelting (Davis et al, 1988;Dorman et al, 2006;Normandin et al, 2004).…”