Ferrihydrite
Ferrihydrite is a ubiquitous iron oxyhydroxide mineral. Its chemical formula is generally presented as Fe5HO8•4H2O, also written as 5Fe2O3•9H2O or as Fe2O3•2FeOOH•2.6H2O [1]. It is found throughout soil and water systems [2] and is important to many industrial applications [3] [4]. It can even be found within many living organisms, including humans[5] In particular, it is found in the iron core of the ferritin protein, with serves as an intra-cellular iron storage.
Two types of material are commonly called ferrihydrite: 2-line ferrihydrite (sometimes termed protoferrihydrite) and 6-line ferrihydrite. The distinction refers to the number of X-ray diffraction lines in their respective X-ray patterns. While 6-line ferrihydrite has been classified as a mineral by the IMA since 1973 [6] [7], its structure is still a subject of debate. The less crystalline 2-line ferrihydrite, on the other hand, is not considered a mineral. Compared to most minerals, both 2-line and 6-line ferrihydrite show very broad diffraction lines.
Ferrihydrite only exists as a nanomaterial, showing crystals 2-4 nanometers wide for 2-line ferrihydrite and 5-6 nanometers wide for 6-line ferrihydrite[8] [9] [10].
With its high surface area per volume [11], ferrihydrite is a very reactive mineral. It can interact, either by surface adsorption or by co-precipitation, with a number of environmentally important chemical species, including arsenic, heavy metals like lead or mercury, phosphate, as well as many organic molecules.
Ferrihydrite is a metastable mineral. It is known to be a precursor of more crystalline minerals like hematite and goethite [12].
References
- ↑ J. L. Jambor and J. E. Dutrizac, Chemical Reviews 98, no. 7, 2549-2585 (1998)
- ↑ U. Schwertmann, L. Carlson, E. Murad, Clays Clay Miner. 35, 297 (1987)
- ↑ G. P. Huffman et al., Energy Fuels 7, 285 (1993).
- ↑ P. A. Riveros, J. E. Dutrizac, P. Spencer, Can. Metall. Q. 40, 395 (2001).
- ↑ A. Lewin, G. R. Moore, N. E. Le Brun, Dalton Trans. 2005, 3597 (2005).
- ↑ F. V. Chuckrov, B.B. Zvyagin, A.I. Gorshov, L.P. Yermilova and V.V. Balashova, International Geology Review 16, 1131-1143 (1973)
- ↑ M. Fleischer, G.Y. Chao and A. Kato, American Mineralogist 60 (1975)
- ↑ D.E. Janney, J.M. Cowley and P.R. Buseck, Clays and clay minerals 48, no. 1, 111-119 (2000)
- ↑ D.E. Janney, J.M. Cowley and P.R. Buseck, American mineralogist 85, 1180-1187 (2000)
- ↑ D.E. Janney, J.M. Cowley and P.R. Buseck, American mineralogist 86, 327-335 (2001)
- ↑ J. L. Jambor and J. E. Dutrizac, Chemical Reviews 98, no. 7, 2549-2585 (1998)
- ↑ H. Stanjek and P.G. Weidler, Clay minerals 27, 397-412 (1992)