Refining Magnesium with Electrolysis

What is Electrolysis?

Electrolysis is a method of mining which incorporates the use of electricity to extract reactive metals from their ores. The molten sample or solution of the ore is provided with a voltage, whereby two electrodes are placed in the ore. However, once charged by the connecting battery, the electrodes receive either a positive or negative charge. The positive electrode (a.k.a anode) attracts the negative ions within the ore, and the negative electrode (a.k.a cathode) attracts the positive ions. When the process is complete, the cathode beholds the metal produced from the reaction, and the anode releases the gases exerted from the metal. 

An example of electrolysis in action is the process of refining sodium chloride. Due to the presence of an electric current, the molten sodium chloride has its ions separated in order to produce sodium and chlorine gas. Seeing as the sodium beholds a negative charge, the cathode is able to retrieve it, resulting in pure sodium being created. The anode, on the other hand, attracts and dispatches the chlorine gas that has been excreted from the sodium.

Magnesium - What is it and why does it need to be refined using electrolysis?

Magnesium is often found in combination with calcium, and often in the form of oxide, carbonate or silicate, and is known to inherit a silvery grey colour. Beholding a density of 1.74 g.cm-3 at 20 degrees Celsius, it is known as the lightest of the structural metals, inheriting a close-packed hexagonal crystal structure. 

According to the reactivity series of metal, magnesium is shown to be categorised as a more reactive metal. This is mostly due to its combination with calcium, and is the reason why magnesium is unable to be found as a pure metal. Magnesium is found in sea water where 0.13% of it is present, and production facilities use this magnesium to produce the magnesium metal we know today. For instance, an example of magnesium's reactivity is shown in the following equation:

Magnesium + Silver Nitrate -----> Magnesium nitrate + Silver


This reaction displays the high reactivity of magnesium, as the silver loses the nitrate that was initially attached to it, and becomes a pure metal. The magnesium attaches the nitrate to itself, altering its solid state to an aqueous solution.

Magnesium is known to inherit a silvery grey colour, and is also known to emit an immensely bright light light when it is burnt. This colour is also derived from the fact that it is found in sea water. The silvery grey colour can be as a result of the high reactive state of magnesium when combined with calcium, and therefore reacts with the salt, making it a neutral grey colour. However, when found in the form of nodules, the calcium attached to the magnesium is a reason for its identifiable grey colour. 



Properties of Pure Mg:

Magnesium is categorised as being the lightest of the structural metals, beholding a density of 1.738 g.cm-3 at 20 degrees Celsius. It's low weight plays a part in the association with structural metals, and also for its ability to create mechanically resistant alloys. However, despite this light weight, it is an extremely tough metal, allowing it to be of use to many manufacturers and labourers. However, seeing as it is highly reactive, it is capable of reacting with air, causing it to emit a bright light and ultimately wear down over time, which is a reason why it isn't a trusted metal for construction purposes. For instance, magnesium's sister metal, aluminium, is similar to magnesium in certain aspects, such as being light weight and quite strong. However, unlike magnesium, aluminium is durable, non combustible, and is infinitely recyclable, which makes it favourable over magnesium for construction material by a long margin.


As far as refining magnesium is concerned, electrolysis is more suitable than smelting due to the position of magnesium on the reactivity series of metals. This rank means that electrolysis is the adequate method, as the positive and negative particles of the magnesium ore need to be separated in order to prevent unwanted reactions with other elements such as water, air or oxygen, and to safely extract the pure magnesium metal from the ore. However, these electrolysis processes require certain feed materials in order to extract the magnesium. Pure anhydrous magnesium chloride is a preferred feed material, but producing it isn't easy, as attempting to use small amounts of magnesium oxides to produce the chemical is quite difficult, which is as a result of the hygroscopic (tendency to absorb moisture from the air) nature of magnesium chloride. So, in my opinion, the method of electrolysis is the most suitable method, as magnesium is a reactive metal, and seeing as it is usually combined with calcium, it is safe to say that this method will prevent the occurrence of unwanted reactions with elements such as air, water and oxygen that may occur through the process of smelting the metal.

What refining processes are applied after extraction?

Magnesium is known to be one of the most abundant metals in the world, and this statistic leads to the fact that it doesn't have a specific ore that contains magnesium, in fact there a numerous ores that contain the metal. However, the only ores that are of commercial importance include dolomite, magnesite, brucite, carnallite and olivine. As well as aluminium, magnesium doesn't undergo any large procedure after extraction. The only processes that may take place include the removal of physical impurities such as electrolyte and oxide. There are, however, smaller scale procedures that can be implemented. 

Magnesium alloys refers to the form in which magnesium components are found in. When added to magnesium, the alloys help to strengthen and harden the magnesium, as well as change its chemical reactivity. The most common alloys are shown below.

When is it estimated for the natural reserves of magnesium to run out? Are there any alternatives materials that can be used in the case of magnesium reserves becoming depleted?

Seeing as magnesium is one of the most abundant metals in the world, natural reserves are able to last for a long period of time, and being able to recycle the metal freely will prove to make the situation of magnesium reserves running out less of a shock, due to easy production of the metal in large quantities through recycling.

Magnesium is an abundant metal, and has many properties that make it useful. Its sister metal, aluminium, also has characteristics that are similar to magnesium, making it suitable to replace the metal in a worst case scenario. Aluminium has its advantages over magnesium as well, as it is able to be used for construction as it is quite strong, and doesn't react to natural elements such as air, water and salt. 

Magnesium is used as a protective layer on metals such as iron in order to stop it from rusting. Aluminium wouldn't be suitable for a job such as this, so another metal that could be an alternative is zinc. Zinc, like magnesium, is able to be recycled, and is also used to prevent steel/iron from rusting.

Bibliography

• What is Electrolysis? (15/08/14)
• Electrolytic Refining Process of Metal (15/08/14)
• Mg General (17/08/14)
• Lenntech (17/08/14)
• About-aluminium (19/08/14)
• Ore Minerals (19/08/14)
• Magnesium - Mineral Fact Sheet - Australian Mines Atlas (21/08/14)

Transcripts:

Video 1: 

Discovered by Sir Humphry Davy in 1808, magnesium is a highly reactive metal, and is mostly due to its combination with calcium. It is known as one of the most abundant metals in the world, seeing as 0.13% of magnesium is found in sea water.

Due to its rank on the reactivity series of metals, it requires the method of electrolysis to be extracted. What is electrolysis anyway? Well, it is the process of using electric currents to separate ions in a molecule in order to extract the pure metal within the ore. A positive electrode (anode) and negative electrode (cathode) are used to attract the ions carrying the opposite charge.

As you can see in this diagram, the sodium chloride is being separated, as the sodium is moving to the cathode, and the chlorine gas is moving to the anode, which then releases the gas, leaving the pure metal, which is sodium, to retrieve and process into useful material. 

Video 2:

Hi everybody, and thank you for watching this video. Today, I will be answering the following question.

Magnesium is mined in several places in Australia. Some of these areas include the Kunwarara deposit, which is 60km from Rockhampton in Queensland, veins and nodules of magnesite can be found in Thuddungra, which is northwest of Young in New South Wales, and it can also be found in Tasmania, where fine-grained, massive magnesite, occupy the area.

Magnesium is a metal that is commercially important, and is versatile in the way that it has an array of uses.

Due to the characteristic of versatility, magnesium is capable of being implemented in numerous ways. Magnesium can be used for a variety of things, some of these being frames for luggage bags, cameras and optical instruments, and portable power tools.

Video 3:

Magnesium is a non-renewable source, however, similarly to aluminium, it is reusable. This property demonstrates how magnesium will be able to last for years and years on end, and natural reserves running out isn’t a big worry, as magnesium can be infinitely recycled.

In terms of alternatives, I believe there are two appropriate options: Aluminium and Zinc

Aluminium has similar characteristics to magnesium, however it is stronger and more durable, making it ideal for construction purposes, and is also recyclable

Zinc, on the other hand, is similar to magnesium in the way that it prevents iron/steel from rusting. As well as aluminium, zinc can be recycled, making it an appropriate alternative for magnesium.

However, in terms of what magnesium is used for, zinc would be a more suitable option because, let’s be honest, would you rather zinc or aluminium to prevent your car from rusting?

  

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