Potassium ferrate

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Potassium ferrate
Potassium ferrate.svg
K2FeO4-xtal-1982-CM-3D-balls.png
Names
IUPAC name
Potassium ferrate(VI)
Other names
Potassium ferrate
Dipotassium ferrate
Identifiers
Properties
K2FeO4
Molar mass 198.0392 g/mol
Appearance Dark purple solid
Density 2.829 g/cm3, solid
Melting point >198 °C (decomposition temp)
soluble in 1M KOH
Solubility in other solvents reacts with most solvents
Structure
K2SO4 motif
Tetrahedral
0 D
Hazards
Main hazards oxidizer
R-phrases (outdated) 8
S-phrases (outdated) 17-36
Flash point non-combustible
Related compounds
Other anions
K2MnO4
K2CrO4
K2RuO4
Other cations
BaFeO4
Na2FeO4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Potassium ferrate is the chemical compound with the formula K2FeO4. This purple salt is paramagnetic, and is a rare example of an iron(VI) compound. In most of its compounds, iron has the oxidation state +2 or +3 (Fe2+ or Fe3+). Reflecting its high oxidation state, FeO42− is a powerful oxidizing agent.

Synthesis and structure[edit]

An aqueous solution of potassium ferrate(VI).

Georg Ernst Stahl (1660 – 1734) first discovered that the residue formed by igniting a mixture of potassium nitrate (saltpetre) and iron powder dissolved in water to give a purple solution. Edmond Frémy (1814 – 1894) later discovered that fusion of potassium hydroxide and iron(III) oxide in air produced a compound that was soluble in water. The composition corresponded to that of potassium manganate. In the laboratory, K2FeO4 is prepared by oxidizing an alkaline solution of an iron(III) salt with concentrated chlorine bleach.[1]

The salt is isostructural with K2MnO4, K2SO4, and K2CrO4. The solid consists of K+ and the tetrahedral FeO42− anion, with Fe-O distances of 1.66 Å.[2] The poorly soluble barium salt, BaFeO4, is also known.

Properties and applications[edit]

The main difficulty with the use of K2FeO4 is that it is often too reactive, as indicated by the fact that it decomposes in contact with water, especially in acidic water:[3]

4 K2FeO4 + 4 H2O → 3 O2 + 2 Fe2O3 + 8 KOH

At high pH, aqueous solutions are stable. The deep purple solutions are similar in appearance to potassium permanganate (KMnO
4
). It is stronger oxidizing agent than the latter.As a dry solid, K2FeO4 is stable.

Because the side products of its redox reactions are rust-like iron oxides, K2FeO4 has been described as a "green oxidant." It has been employed in waste-water treatment as an oxidant for organic contaminants and as a biocide. Conveniently, the resulting reaction product is iron(III) oxyhydroxide, an excellent flocculant. In organic synthesis, K2FeO4 oxidizes primary alcohols.[4] In contrast, related oxidants such as chromate are considered environmentally hazardous

K2FeO4 has also attracted attention as a potential cathode material in a "super iron battery."

Stabilized forms of potassium ferrate have been proposed for the removal of transuranic species, both dissolved and suspended, from aqueous solutions. Tonnage quantitites were proposed to help remediate Chernoybl's effects in Belarus. This new technique were successfully applied for the removal of a broad range of heavy metals.[citation needed]

It has been proposed as a bleeding stopper for fresh wounds.[5][6]

References[edit]

  1. ^ Schreyer, J. M.; Thompson, G. W.; Ockerman, L. T. "Potassium Ferrate(VI)" Inorganic Syntheses, 1953 volume IV, pages 164-168.
  2. ^ Hoppe, M. L.; Schlemper, E. O.; Murmann, R. K. "Structure of Dipotassium Ferrate(VI)" Acta Crystallographica 1982, volume B38, pp. 2237-2239. doi:10.1107/S0567740882008395.
  3. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  4. ^ Green, J. R. “Potassium Ferrate” Encyclopedia of Reagents for Organic Synthesis 2001, John Wiley. doi:10.1002/047084289X.rp212.
  5. ^ "How WoundSeal Works". WoundSeal. 2016. 
  6. ^ WO application 2014153566, John Hen; Talmadge Kelly Keene & Mark Travi, "Hemostatic device and method", published 2014-09-25