Magnesium Oxide: A Versatile Mineral with Wide-Ranging Applications
What is Magnesium Oxide?
Magnesium oxide, also known as magnesia, is a white hygroscopic solid mineral that is a source of magnesium. With a chemical formula of MgO, it has an empirical formula weight of 40.304 g/mol. Magnesium oxide has a crystalline structure and ionic bonding between magnesium and oxygen atoms gives it characteristics useful for a variety of industrial and commercial purposes.
Physical Properties
As mentioned, magnesium oxide has a crystalline structure that gives it unique physical properties. It has a melting point of 2,852°F (1,560°C) and a boiling point of 5,086°F (2,800°C). This gives it excellent heat resistance properties making it suitable for applications requiring high temperatures. Magnesium oxide has a specific gravity of 3.58 and hardness of 5.5–6 on the Mohs scale. It is a stable, non-toxic material that is often produced synthetically on an industrial scale.
Uses in Refractories
One of the most common uses of magnesium oxide is in refractory materials. Refractories are heat-resistant composite materials used to line furnaces, kilns, incinerators and other equipment handling high heat processes. Magnesium oxide is a prime ingredient in basic refractory bricks due to its high melting point, chemical stability and resistance to slag and other corrosive materials. It is often mixed with other oxides like alumina or silica to strengthen mechanical properties in various lining formulations.
Role in Agriculture
Magnesium oxide also sees widespread use in agriculture as a soil conditioner and fertilizer. Application of magnesium oxide to soil helps counteract acidification and supplies plants with a necessary macronutrient. It is effective at reducing levels of soluble aluminum and manganese ions that can be toxic to plant roots at high concentrations. Foliar application of magnesium oxide can also correct magnesium deficiencies in crop leaves. Livestock may consume magnesium oxide supplements to fulfill their dietary needs as well. Its antacid properties also have some medicinal uses for both humans and animals.
Purification Applications
The chemical properties of magnesium oxide make it useful for purification in some industrial processes. It has a strong affinity for water vapor and will readily absorb moisture from gas streams, acting as a desiccant. For this reason, it is sometimes used during production of anhydrous magnesium chloride. Magnesium oxide also has a high oxygen storage capacity and releases free oxygen when heated, allowing its use in steel degassing and refining processes. As an amphoteric substance, it can act as both an acid or base depending on conditions and participate in neutralization reactions.
Misc Uses & Outlook
Aside from the major applications above, magnesium oxide has other minor commercial and industrial uses. It appears as an opacifying agent in paints, varnishes and plastics due to its high refractive index. Magnesium oxide is a component in celadon glazes for pottery products and also has pharmaceutical applications as an antacid, laxative or mineral supplement. Some techniques now allow the production of nano-scale magnesium oxide with additional enhanced properties. Overall demand for magnesium oxide is projected to increase modestly over the coming years, largely driven by growing refractories and construction markets in developing economies.
