Extraction of Metals: Types and Methods

Extraction of metals is the process of getting pure metals from their ores, which are naturally occurring metal complexes contaminated with contaminants. The extraction procedures used are determined by the metal's reactivity and the composition of the ore.

• On Earth, there are only a few metals that exist naturally without combining with other elements. 
• These metals are not very reactive, which means they don't easily form compounds with other substances. 
• Examples of these metals include gold, silver, and platinum, as well as elements like carbon, sulfur, nitrogen, and noble gases.
• On the other hand, certain elements are reactive and easily react with oxygen, moisture, carbon dioxide, or non- metal elements. 
• These reactive elements are found on Earth's crust in the form of compounds.
•  Metals usually exist in an oxidised form when they combine with oxygen, while non-metals are usually in a reduced form.

To use these elements for specific purposes, they need to be extracted from their compounds to obtain them in their pure form. This extraction process allows us to separate the metals and non-metals from their combined states so that one can use them effectively.

Keywords: Extraction,Metallurgy, Ores, Compounds, Element, Metals, Non- Metals, Roasting, Calcination, Crushing

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What is Ores? 

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Ore is the rock from which metal is mined conveniently and cost-effectively. Ore has a distinct chemical composition. Minerals are metals that exist naturally in the earth's crust. Ores are minerals that can be exploited profitably to extract metal.

Read More: Metallurgy

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Types of Ores

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Given below are the types of ores with their examples- 

• Oxide Ores: The metals are found in an oxidized state in this particular ore. Metal extraction from this ore is substantially simpler. Example-: Bauxite (aluminum) and haematite (iron) ore 
• Sulphide Ores: The metals in this particular ore are found as sulphides. Since this ore makes it harder to extract the metals, metallurgy is typically used to turn them into oxides. For example, Lead (Galena) and Zinc Blende (Zinc).
• Carbonate Ores: Carbonate ions are found in this mineral. These ores are also transformed into oxide ores first because it is challenging to extract metals from them. 
• Sulphate Ores: They are typically found underground and include ions of sulphur. Example-: Anglesite (Lead)

Read More: Properties of Non-metals

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Extraction of Metals

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Metals exist mostly in the form of salts that combine with other minerals to form ore. 

• These contaminants should be eliminated using various inorganic separation processes. 
• The main focus of the extraction of metals is to get pure metal at a very low cost. 
• The better the method of extraction the lower the cost of extraction. 

Below are the steps mentioned for the extraction of metals.

 

Grinding and Crushing

Grinding and crushing are processes used to extract metals from ores in a simpler way. Think of grinding as using a rough surface, like sandpaper, to break down the ore into smaller pieces. It's like when two rough surfaces are rubbed together to make them smoother.

• The bigger ore particles are broken into small ore particles this process is known as crushing. 
• These processes are important because they increase the surface area of the ore, making it easier for chemicals or other methods to extract valuable metals. 
• So, grinding and crushing is like preparing the ore for the next steps in the extraction process, making it easier to separate the valuable metals from the rest of the material.

Concentrating the Ore

This step focuses on separating the valuable parts of the ore from the unwanted substances. It is also known as ore dressing. This process is quite detailed and is named based on the equipment or method used. 

Hydrolytic Method

The pulverised ore particles are poured over a vibrating table with a slope or inclination in this procedure. 

• To move the particles on the ground, a water jet is used. 
• Impurities weigh less than metal-containing ore particles. 
• They wash down, while the heavier particles settle on the inclined table's grooves.
• This is commonly utilised when the metal ore is significantly heavier than the impurities.

Magnetic Separation

After pulverising, this process is used to separate the ferromagnetic metal ore from the impurities. 

• The ground ore particles are transported on a two-wheeled conveyor belt. 
• One of these wheels has a magnetic field. 
• The ferromagnetic ore particles will be attracted and easily separated from the contaminants.

Froth Floatation

Froth flotation is a process for separating minerals from gangue (waste material) by using differences in their surface properties. 

• The minerals that are to be separated are made hydrophobic (water-repelling) by adding a surfactant, while the gangue is made hydrophilic (water-attracting). 
• The mixture is then agitated with air, which creates bubbles.
• The hydrophobic minerals attach to the air bubbles and float to the surface, while the hydrophilic gangue sinks to the bottom. 
• The froth is then skimmed off and the minerals are recovered.

Chemical Separation

Chemical separation is one method of concentrating the ore. For instance, the extraction of aluminium (Al) from bauxite ore.

• Bayer's Process is another name for the process of extracting aluminium from bauxite ore. 
• When hot NaOH combines with bauxite ore, sodium aluminate is formed, which is water soluble. 
• The sodium aluminate solution is then diluted with water, yielding aluminium hydroxide when cooled. 
• This is then washed and filtered to obtain the pure aluminium oxide known as alumina. 

Calcination and Roasting

After the ores have been concentrated using the earlier indicated procedures, they are heated, either with or without air, depending on the specific element and its properties. 

• If the ore includes sulphide, for example, it is heated with oxygen in a process called roasting. 
• If the ore includes carbonates, it is heated in a vacuum to facilitate metal extraction, a process called as calcination. 
• These heating procedures aid in the refinement of concentrated ore in order to achieve purer metals.

In summary, this is an overview of how metals are extracted from ores and minerals while taking the physical and chemical features of the impure ores into account. This approach also explains how metals near the bottom of the activity chain can be used.

Read More: Refining Metals

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Major Metal Ores in India

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Major Metal Ores are as follows:

• Iron is a widely used metal everywhere. In India Goa, Karnataka, and Orissa are the three states where major iron ores are located.
• Bauxite ore is used to produce aluminium. Bauxite ore is the most widely accessible resource in India. 
• Gujarat, Tamil Nadu, and Maharashtra are the states where bauxite deposits are found. 
• Jharkhand is home to tin, which is mined from tinstone. 

Read More: Physical Properties of metals and non-metals

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Things To Remember

• Ore is a naturally occurring material that can be used to economically extract elements.
• The three methods for extracting metals are pyrometallurgy, hydrometallurgy, and electrolytic reduction.
• Haematite, magnetite, limonite, iron pyrite, and siderite are significant iron ores.
• Haematite is used mostly in the extraction of iron. It is the extensively used ore of iron. 
• Calcination is the thermal breakdown of any substance in a little amount of air or without any air.
• Metal is extracted during smelting by using reducing agents like C, H₂, etc.
• Sulphide ore is heated during roasting while air is present.

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