Magnesium (Mg) and water
Magnesium and water: reaction mechanisms, environmental impact and health effects
|Magnesium is present in seawater in amounts of about 1300 ppm. After sodium, it is the most commonly found cation in oceans. Rivers contains approximately 4 ppm of magnesium, marine algae 6000-20,000 ppm, and oysters 1200 ppm. |
Dutch drinking water contains between 1 and 5 mg of magnesium per liter.
Magnesium and other alkali earth metals are responsible for water hardness. Water containing large amounts of alkali earth ions is called hard water, and water containing low amounts of these ions is called soft water.
Magnesium metals are not affected by water at room temperature. Magnesium generally is a slow-reacting element, but reactivity increases with oxygen levels. Furthermore, magnesium reacts with water vapor to magnesium hydroxide and hydrogen gas:
Mg (s) + 2H2O(g) -> Mg(OH)2(aq) + H2(g)
Magnesium fires cannot be extinguished by water. Magnesium continues to burn after oxygen is depleted. It than reacts with nitrogen from air to form magnesium nitride (Mg3N2). When attempts are made to extinguish magnesium fires with water, magnesium aggressively reacts with hydrogen gas. To prevent any damage, a magnesium fire must be covered in sand.
Magnesium is mainly present as Mg2+ (aq) in watery solutions, but also as MgOH+ (aq) and Mg(OH)2 (aq). In seawater it can also be found as MgSO4.
A large number of minerals contains magnesium, for example dolomite (calcium magnesium carbonate; CaMg(CO3)2) and magnesite (magnesium carbonate; MgCO3). Magnesium is washed from rocks and subsequently ends up in water.
Magnesium is a dietary mineral for any organism but insects. It is a central atom of the chlorophyll molecule, and is therefore a requirement for plant photosynthesis. Magnesium cannot only be found in seawater, but also in rivers and rain water, causing it to naturally spread throughout the environment.
he human body contains about 25 g of magnesium, of which 60% is present in the bones and 40% is present in muscles and other tissue. It is a dietary mineral for humans, one of the micro elements that are responsible for membrane function, nerve stimulant transmission, muscle contraction, protein construction and DNA replication. Magnesium is an ingredient of many enzymes. Magnesium and calcium often perform the same functions within the human body and are generally antagonistic.
Which water purification technologies can be applied to remove magnesium from water?
Magnesium compounds are usually removed from water, because of the role magnesium plays in water hardness. This is achieved by means of water softening.