Cobalt_carbonate

Cobalt(II) carbonate

Cobalt(II) carbonate

Chemical compound

Cobalt(II) carbonate is the inorganic compound with the formula CoCO3. This reddish paramagnetic solid is an intermediate in the hydrometallurgical purification of cobalt from its ores. It is an inorganic pigment, and a precursor to catalysts.[5] Cobalt(II) carbonate also occurs as the rare red/pink mineral spherocobaltite.[6]

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Preparation and structure

It is prepared by combining solutions cobaltous sulfate and sodium bicarbonate:

CoSO4 + 2 NaHCO3 → CoCO3 + Na2SO4 + H2O + CO2

This reaction is used in the precipitation of cobalt from an extract of its roasted ores.[5]

CoCO3 adopts a structure like calcite, consisting of cobalt in an octahedral coordination geometry.[7]

Reactions

Like most transition metal carbonates, cobalt carbonate is insoluble in water, but is readily attacked by mineral acids:

CoCO3 + 2 HCl + 5 H2O → [Co(H2O)6]Cl2 + CO2

It is used to prepare many coordination complexes. The reaction of cobalt(II) carbonate and acetylacetone in the presence of hydrogen peroxide gives tris(acetylacetonato)cobalt(III).[8]

Heating the carbonate proceeds in a typical way for calcining, except that the product becomes partially oxidized:

6 CoCO3 + O2 → 2 Co3O4 + 6 CO2

The resulting Co3O4 converts reversibly to CoO at high temperatures.[9]

Uses

Cobalt carbonate is a precursor to cobalt carbonyl and various cobalt salts. It is a component of dietary supplements since cobalt is an essential element. It is a precursor to blue pottery glazes, famously in the case of Delftware.

At least two cobalt(II) carbonate-hydroxides are known: Co2(CO3)(OH)2 and Co6(CO3)2(OH)8·H2O.[10]

The moderately rare spherocobaltite is a natural form of cobalt carbonate, with good specimens coming especially from the Republic of Congo. "Cobaltocalcite" is a cobaltiferous calcite variety that is quite similar in habit to spherocobaltite.[6]

Safety

Toxicity has rarely been observed. Animals, including humans, require trace amounts of cobalt, a component of vitamin B12.[5]

References

  1. [1]
    "Cobalt(II) carbonate".
  2. [2]
    Haynes, W.M., ed. (2017). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press, Taylor & Francis Group. pp. 4–58. ISBN 978-1-4987-5429-3.
  3. [3]
    "Solubility product constants". Archived from the original on 2012-06-15. Retrieved 2012-05-17.
  4. [4]
    Sigma-Aldrich Co., Cobalt(II) carbonate. Retrieved on 2014-05-06.
  5. [5]
    Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. ISBN 978-3527306732.
  6. [6]
    "Spherocobaltite: Spherocobaltite mineral information and data". www.mindat.org. Retrieved 7 August 2018.
  7. [7]
    Pertlik, F. (1986). "Structures of hydrothermally synthesized cobalt(II) carbonate and nickel(II) carbonate". Acta Crystallographica Section C. 42: 4–5. doi:10.1107/S0108270186097524.
  8. [8]
    Bryant, Burl E.; Fernelius, W. Conard (1957). "Cobalt(III) Acetylacetonate". Inorganic Syntheses. pp. 188–189. doi:10.1002/9780470132364.ch53. ISBN 9780470132364.
  9. [9]
    G.A. El-Shobaky, A.S. Ahmad, A.N. Al-Noaimi and H.G. El-Shobaky Journal of Thermal Analysis and Calorimetry 1996, Volume 46, Number 6 , pp.1801-1808. online abstract
  10. [10]
    Bhojane, Prateek; Le Bail, Armel; Shirage, Parasharam M. (2019). "A Quarter of a Century After its Synthesis and with >200 Papers Based on its Use, 'Co(CO3)0.5(OH)0.11H2O′ Proves to be Co6(CO3)2(OH)8·H2O from Synchrotron Powder Diffraction Data". Acta Crystallographica Section C: Structural Chemistry. 75 (Pt 1): 61–64. doi:10.1107/S2053229618017734. PMID 30601132. S2CID 58657483.
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