Calcium peroxide

Calcium peroxide or calcium dioxide is the inorganic compound with the formula CaO2. It is the peroxide (O22−) salt of Ca2+. Commercial samples can be yellowish, but the pure compound is white. It is almost insoluble in water.[2]

Calcium peroxide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.013.764
EC Number
  • 215-139-4
E number E930 (glazing agents, ...)
674257
KEGG
RTECS number
  • EW3865000
UNII
UN number 1457
Properties
CaO2
Molar mass 72.0768 g/mol
Appearance white or yellowish powder
Odor odorless
Density 2.91 g/cm3
Melting point ~ 355 °C (671 °F; 628 K) (decomposes)
decomposes
Acidity (pKa) 12.5
-23.8·10−6 cm3/mol
1.895
Structure
Orthorhombic[1]
Pna21
8[1]
Hazards
GHS pictograms
GHS Signal word Warning
GHS hazard statements
 H272, H315, H319, H335
P210, P220, P221, P261, P264, P271, P280, P302+352, P304+340, P305+351+338, P312, P321, P332+313, P337+313, P362, P370+378, P403+233, P405, P501
Lethal dose or concentration (LD, LC):
>5000 mg/kg (oral, rat)
>10000 mg/kg (dermal, rat)
Related compounds
Other anions
 Calcium oxide
Other cations
 Strontium peroxide
Barium peroxide
Sodium peroxide
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

Structure and stability

As a solid, it is relatively stable against decomposition. In contact with water however it hydrolyzes with release of oxygen. Upon treatment with acid, it forms hydrogen peroxide.

Preparation

Calcium peroxide is produced by combining calcium salts and hydrogen peroxide:

Ca(OH)2 + H2O2 → CaO2 + 2 H2O

The octahydrate precipitates upon the reaction of calcium hydroxide with dilute hydrogen peroxide. Upon heating it dehydrates.

Applications

It is mainly used as an oxidant to enhance the extraction of precious metals from their ores. In its second main application, it is used as a food additive under the E number E930 it is used as flour bleaching agent and improving agent.[2]

In agriculture it is used in the presowing treatments of rice seed. Also, calcium peroxide has found use in the aquaculture to oxygenate and disinfect water. In the ecological restoration industry it is used in the treatment of soils. Calcium peroxide is used in a similar manner to magnesium peroxide for environmental restoration programs. It is used to restore soil and groundwater contaminated with petroleum by the process of enhanced in-situ bioremediation.

It is also used for curing polythioether polymers by oxidising terminal thiol groups to disulphide bridges.

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References
  1. Zhao, X.; Nguyen, M.C.; Wang, C.Z.; Ho, K.M. (2013). "Structures and stabilities of alkaline earth metal peroxides XO2 (X = Ca, Be, Mg) studied by a genetic algorithm" (PDF). RSC Advances. doi:10.1039/C3RA43617A.
  2. Harald Jakob, Stefan Leininger, Thomas Lehmann, Sylvia Jacobi, Sven Gutewort. "Peroxo Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_177.pub2.CS1 maint: multiple names: authors list (link)
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