Magnesium peroxide (MgO₂) is an odorless fine powder

peroxide In chemistry, peroxides are a group of compounds with the structure , where R = any element. The group in a peroxide is called the peroxide group or peroxo group. The nomenclature is somewhat variable. The most common peroxide is hydrogen p ...

with a white to off-white color. It is similar to

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. Structure an ...

because

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...

peroxide also releases

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

by breaking down at a controlled rate with water. Commercially, magnesium peroxide often exists as a compound of magnesium peroxide and magnesium hydroxide.

Structure

O₂, similarly to N₂, has the ability to bind either side-on or end-on. The structure of MgO₂ has been calculated as a triangular shape with the O₂ molecule binding side-on to the magnesium. This arrangement is a result of the Mg⁺ donating charge to the oxygen and creating a Mg²⁺O₂²⁻. The bond between to O₂ and the magnesium atom has an approximate dissociation energy of 90 kJ mol⁻¹. In the solid state, MgO₂ has a cubic pyrite-type crystal structure with 6-coordinate Mg²⁺ ions and O₂²⁻ peroxide-groups, according to experimental data and evolutionary crystal structure prediction, the latter predicting a phase transition at the pressure of 53 GPa to a tetragonal structure with 8-coordinate Mg²⁺ ions. While at normal conditions MgO₂ is a metastable compound (less stable than MgO +1/2O2), at pressures above 116 GPa it is predicted to become thermodynamically stable in the tetragonal phase. This theoretical prediction has been experimentally confirmed via synthesis in a laser-heated diamond anvil cell.

Synthesis

MgO₂ can be produced by mixing

MgO Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ion ...

with

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3 ...

to create magnesium peroxide and water. This being an

exothermic reaction In thermochemistry, an exothermic reaction is a "reaction for which the overall standard enthalpy change Δ''H''⚬ is negative." Exothermic reactions usually release heat. The term is often confused with exergonic reaction, which IUPAC defines ...

should be cooled and kept around 30–40 degrees Celsius. It is also important to remove as much iron from the reaction environment as possible due to iron's ability to catalyze the degradation of the peroxide. The addition of oxygen stabilizers such as

sodium silicate Sodium silicate is a generic name for chemical compounds with the formula or ·, such as sodium metasilicate , sodium orthosilicate , and sodium pyrosilicate . The anions are often polymeric. These compounds are generally colorless transparent ...

can also be used to help prevent the premature degradation of the peroxide. Regardless, a good yield from this reaction is only about 35%. : MgO + H2O2 -> MgO2 + H2O High yields are further complicated by the fact that MgO₂ reacts with water to degrade the peroxide into magnesium hydroxide, also known as milk of magnesia.

Applications

Magnesium peroxide is a stable

releasing compound, which is used in

agricultural Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled peopl ...

and

environmental A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scal ...

industries. It is used to reduce contaminant levels in

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit ...

. Magnesium peroxide is used in the

bioremediation Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi, and plants), living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluent ...

of contaminated

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...

and can improve the soil quality for

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae excl ...

growth and

metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run ...

. It is also used in the

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...

industry for bioremediation. For sanitation purposes magnesium peroxide is often used as a source of oxygen for aerobic organisms in the treatment and disposal of biological waste. Since the breakdown of

hydrocarbons In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

in soil is usually quicker in aerobic conditions, MgO₂ can also be added to

compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...

piles or in soil to speed up the microbe activities and to reduce the odors produced in the process. In certain circumstances MgO₂ has also been shown to inhibit growth of bacteria. In particular, the growth of sulfate-reducing bacteria can be inhibited in an environment containing magnesium peroxide. While the oxygen slowly dissociates, it is theorized that it may then act to displace the sulfate that normally acts as the terminal electron acceptor in their electron transport chain.

Toxicity

Magnesium peroxide is an irritant that can cause redness, itching, swelling, and may burn the skin and eyes on contact. Inhalation can also cause irritation to the lungs, nose, and throat, as well as causing coughing. Long term exposure may lead to lung damage, shortness of breath, and tightening of the chest. Ingestion of MgO₂ can cause numerous adverse effects including: bloating, belching, abdominal pain, irritation of the mouth and throat, nausea, vomiting, and diarrhea. Environmentally, magnesium peroxide is not a naturally occurring compound and is not known to persist in the environment for prolonged times, in its complete state, or to bio-accumulate. The natural degradation of MgO₂ leads to magnesium hydroxide, O₂, and H₂O. If spilled, MgO₂ should be contained and isolated from any waterways, sewer drains, and it should be isolated from combustible materials or chemicals including paper, cloth, and wood.

Common Environmental Reactions

Magnesium exists in the upper atmosphere in a variety of different molecular forms. Due to its ability to react with common oxygen and simple carbon-oxygen compounds the magnesium may exist in oxidized compounds including MgO₂, OMgO₂,

, and O₂MgO₂. : MgCO₃ + O → MgO₂ + CO₂ : : OMgO₂ + O → MgO₂ + O₂ : : MgO + O₃ → MgO₂ + O₂ : : MgO₂ + O₂ → O₂MgO₂ : : MgO₂ + O → MgO + O₂ In contact with water it decomposes by the reactions: : MgO₂ + 2 H₂O → Mg(OH)₂ + H₂O₂ : 2 H₂O₂ → 2 H₂O + O₂

References

{{oxygen compounds Peroxides Magnesium compounds Antacids