Iron oxide

Last updated
Electrochemically oxidized iron (rust) Almindeligt rust - jernoxid.jpg
Electrochemically oxidized iron (rust)

Iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust. [1]

Contents

Iron oxides and oxyhydroxides are widespread in nature and play an important role in many geological and biological processes. They are used as iron ores, pigments, catalysts, and in thermite, and occur in hemoglobin. Iron oxides are inexpensive and durable pigments in paints, coatings and colored concretes. Colors commonly available are in the "earthy" end of the yellow/orange/red/brown/black range. When used as a food coloring, it has E number E172.

The earliest applications of paint served purely ornamental purposes. Consequently, pigment lacking any adhesive agent—composed mainly of iron oxide was employed in prehistoric cave art around the 15,000s BC in parts of Asia. [2]

Stoichiometries

Iron oxide pigment. The brown color indicates that iron is at the oxidation state +3. IronOxidePigmentUSGOV.jpg
Iron oxide pigment. The brown color indicates that iron is at the oxidation state +3.
Green and reddish brown stains on a limestone core sample, respectively corresponding to oxides/hydroxides of Fe and Fe . Red and green iron oxides.jpg
Green and reddish brown stains on a limestone core sample, respectively corresponding to oxides/hydroxides of Fe and Fe .

Iron oxides feature as ferrous (Fe(II)) or ferric (Fe(III)) or both. They adopt octahedral or tetrahedral coordination geometry. Only a few oxides are significant at the earth's surface, particularly wüstite, magnetite, and hematite.

Thermal expansion

Iron oxide CTE (× 10−6 °C−1)
Fe2O314.9 [7]
Fe3O4>9.2 [7]
FeO12.1 [7]

Oxide-hydroxides

Reactions

In blast furnaces and related factories, iron oxides are converted to the metal. Typical reducing agents are various forms of carbon. A representative reaction starts with ferric oxide: [10]

2 Fe2O3 + 3 C → 4 Fe + 3 CO2

In nature

Iron is stored in many organisms in the form of ferritin, which is a ferrous oxide encased in a solubilizing protein sheath. [11]

Species of bacteria, including Shewanella oneidensis , Geobacter sulfurreducens and Geobacter metallireducens , use iron oxides as terminal electron acceptors. [12]

Uses

Almost all iron ores are oxides, so in that sense these materials are important precursors to iron metal and its many alloys.

Iron oxides are important pigments, coming in a variety of colors (black, red, yellow). Among their many advantages, they are inexpensive, strongly colored, and nontoxic. [13]

Magnetite is a component of magnetic recording tapes.

See also

References

  1. ↑ Cornell., RM.; Schwertmann, U (2003). The iron oxides: structure, properties, reactions, occurrences and. Wiley VCH. ISBN   978-3-527-30274-1.
  2. ↑ Hunter, Erica C. D (1972). Funk & Wagnalls new encyclopedia p 73. New York, Funk & Wagnalls. ISBN   978-0-8343-0094-1.
  3. ↑ Lavina, B.; Dera, P.; Kim, E.; Meng, Y.; Downs, R. T.; Weck, P. F.; Sutton, S. R.; Zhao, Y. (Oct 2011). "Discovery of the recoverable high-pressure iron oxide Fe4O5". Proceedings of the National Academy of Sciences. 108 (42): 17281–17285. Bibcode:2011PNAS..10817281L. doi: 10.1073/pnas.1107573108 . PMC   3198347 . PMID   21969537.
  4. ↑ Lavina, Barbara; Meng, Yue (2015). "Synthesis of Fe5O6". Science Advances. 1 (5) e1400260. doi:10.1126/sciadv.1400260. PMC   4640612 . PMID   26601196.
  5. 1 2 Bykova, E.; Dubrovinsky, L.; Dubrovinskaia, N.; Bykov, M.; McCammon, C.; Ovsyannikov, S. V.; Liermann, H. -P.; Kupenko, I.; Chumakov, A. I.; Rüffer, R.; Hanfland, M.; Prakapenka, V. (2016). "Structural complexity of simple Fe2O3 at high pressures and temperatures". Nature Communications. 7 10661. Bibcode:2016NatCo...710661B. doi:10.1038/ncomms10661. PMC   4753252 . PMID   26864300.
  6. ↑ Merlini, Marco; Hanfland, Michael; Salamat, Ashkan; Petitgirard, Sylvain; Müller, Harald (2015). "The crystal structures of Mg2Fe2C4O13, with tetrahedrally coordinated carbon, and Fe13O19, synthesized at deep mantle conditions". American Mineralogist. 100 (8–9): 2001–2004. Bibcode:2015AmMin.100.2001M. doi: 10.2138/am-2015-5369 . S2CID   54496448.
  7. 1 2 3 Fakouri Hasanabadi, M.; Kokabi, A.H.; Nemati, A.; Zinatlou Ajabshir, S. (February 2017). "Interactions near the triple-phase boundaries metal/glass/air in planar solid oxide fuel cells". International Journal of Hydrogen Energy. 42 (8): 5306–5314. Bibcode:2017IJHE...42.5306F. doi:10.1016/j.ijhydene.2017.01.065. ISSN   0360-3199.
  8. ↑ Nishi, Masayuki; Kuwayama, Yasuhiro; Tsuchiya, Jun; Tsuchiya, Taku (2017). "The pyrite-type high-pressure form of FeOOH" . Nature. 547 (7662): 205–208. Bibcode:2017Natur.547..205N. doi:10.1038/nature22823. ISSN   1476-4687. PMID   28678774. S2CID   205257075.
  9. ↑ Hu, Qingyang; Kim, Duckyoung; Liu, Jin; Meng, Yue; Liuxiang, Yang; Zhang, Dongzhou; Mao, Wendy L.; Mao, Ho-kwang (2017). "Dehydrogenation of goethite in Earth's deep lower mantle". Proceedings of the National Academy of Sciences. 114 (7): 1498–1501. Bibcode:2017PNAS..114.1498H. doi: 10.1073/pnas.1620644114 . PMC   5320987 . PMID   28143928.
  10. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1072. doi:10.1016/C2009-0-30414-6. ISBN   978-0-08-037941-8.
  11. ↑ Honarmand Ebrahimi, Kourosh; Hagedoorn, Peter-Leon; Hagen, Wilfred R. (2015). "Unity in the Biochemistry of the Iron-Storage Proteins Ferritin and Bacterioferritin". Chemical Reviews. 115 (1): 295–326. doi: 10.1021/cr5004908 . PMID   25418839.
  12. ↑ Bretschger, O.; Obraztsova, A.; Sturm, C. A.; Chang, I. S.; Gorby, Y. A.; Reed, S. B.; Culley, D. E.; Reardon, C. L.; Barua, S.; Romine, M. F.; Zhou, J.; Beliaev, A. S.; Bouhenni, R.; Saffarini, D.; Mansfeld, F.; Kim, B.-H.; Fredrickson, J. K.; Nealson, K. H. (20 July 2007). "Current Production and Metal Oxide Reduction by Shewanella oneidensis MR-1 Wild Type and Mutants". Applied and Environmental Microbiology. 73 (21): 7003–7012. Bibcode:2007ApEnM..73.7003B. doi:10.1128/AEM.01087-07. PMC   2223255 . PMID   17644630.
  13. ↑ Buxbaum, Gunter; Printzen, Helmut; Mansmann, Manfred; Räde, Dieter; Trenczek, Gerhard; Wilhelm, Volker; Schwarz, Stefanie; Wienand, Henning; Adel, Jörg; Adrian, Gerhard; Brandt, Karl; Cork, William B.; Winkeler, Heinrich; Mayer, Wielfried; Schneider, Klaus (2009). "Pigments, Inorganic, 3. Colored Pigments". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.n20_n02. ISBN   978-3527306732.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.