Extraction of Crude Metal From Concentrated Ore

What is Crude Metal?

Metal extraction from a concentrated solution The refining of metals from the compounds in which they are found to their original condition is known as ore. After converting the concentrated ore to oxide, the metal is extracted by reducing the oxide to metal with an appropriate reducing agent. The extraction of metals occurs over three major stages.

  1. Concentration of Ore
  2. Isolation of metal from concentrated Ore
  3. Purification of the metal
Isolation of metal from concentrated ore involves the refining of metals from the compounds. It is found within its original state. The concentrated ore is first converted to an oxide after which metal extraction is done by reducing it from oxide to metal using a suitable reducing agent.

Table of Contents

Conversion to Oxide

In this process, metal refining is done by heating the ore in a limited supply or absence of air. This is done with the aim of bringing about thermal decomposition and removing volatile compounds from the ore leaving behind a metal oxide.

This is completed in the two processes (i) Calcination Process or (ii) Roasting Process

(1) Calcination Process

Calcination may be defined as the process of heating the ore below its melting point in the absence of air. As a result of calcination, the following changes take place.

Some hydrated ores become anhydrous.

\(\begin{array}{l}Fe_{2}O_{3}.3H_{2}O \overset{\Delta }{\rightarrow}2Fe_{2}O_{3} + 3H_{2}O\end{array} \)

 

Some carbonate ores are converted into the oxide form.

\(\begin{array}{l}CaCO_{3}(s) \to CaO(s) + CO_{2}(g)\end{array} \)

(2) Roasting Process

Metal extraction here is done by heating the ore with a regular supply of hot air in the furnace. This is done to encourage solid-gas reaction between the ore and the air. Sulphide ores of elements such as Zinc, Lead and Copper are treated using this method.

The sulphur in the ore, at elevated temperature, reacts with the oxygen to create Sulphur Dioxide and escapes out of the ore into the air.

\(\begin{array}{l}2ZnS + 3O_{2} \overset{\Delta }{\rightarrow} 2ZnO + 2SO_{2}\end{array} \)
\(\begin{array}{l}2PbS + 3O_{2} \overset{\Delta }{\rightarrow} 2PbO + 2SO_{2}\end{array} \)
\(\begin{array}{l}2Cu_{2}S + 3O_{2} \overset{\Delta }{\rightarrow}2Cu_{2}O + 2SO_{2}\end{array} \)

Reduction of Oxide to Metal

The oxide of the metal obtained as a result of Calcination or roasting is converted into a free state by reduction.  Reduction of metal oxide means removal of oxygen to refine the metal to its free state. This is done with the help of reducing agents such as Carbon (C) , Carbon Monoxide (CO),  Hydrogen (H2), Aluminium (Al).

(1) Smelting Process

In this process, the roasted ore in the form of its oxide is mixed with carbon and heated to a temperature above its melting point in a furnace when the oxide of the metal is reduced to the molten metal.

The carbon under the right condition reacts with metal oxide and takes the oxygen with it thereby reducing the metal and leaving it as carbon monoxide gas. If CO is used as a reducing agent then the gas produced will be carbon dioxide.

\(\begin{array}{l}M_{x}O_{y} + yC \to xM + yCO\end{array} \)
\(\begin{array}{l}M_{x}O_{y} + yCO \to xM + yCO_{2}\end{array} \)

(2) Alumino Thermite Process:

Aluminium metal which is highly electropositive can be effectively used for the isolation of metal like chromium, manganese, iron etc. from their ore.

For example: 

Cr2O + 2Al  → Al2O3 + 2Cr

Fe2O3  + 2Al → Al2O3  + 2Fe 

  • A mixture of ferric oxide and aluminium powder is called thermite.
  • Aluminothermic reduction is exothermic in nature and liberates a large amount of energy.
  • Aluminothermic reduction of Fe2O3 also called Thermite Reduction.This is used in the welding of iron. 

We use so many kinds of metals in our daily life and the refining of metals and their eventual extraction and usage affects all of us directly. Metallurgy is a vast treasure-trove of essential knowledge. Come explore it with expert tutors at BYJU’S.

Frequently Asked Questions-FAQs

Q1

1. What is aluminothermic process? Write the equation involved in the process

Some metal oxides are reduced to metal by heating them with Al powder, which is called alumino thermic process. Examples: Fe2O3 + 2Al → Al2O3 + 2Fe . The mixture of Al and ore is called thermite.

Q2

2. What is the calcination process?

The process of heating the ore below its melting point in the absence of air is called the calcination process.

Q3

3. What are calcination and roasting?

Calcination is the process of heating the ore below its melting point in the absence of air to remove volatile impurities like arsenic etc. Roasting is the process in which the ore is heated below its melting point in the presence of air to oxidize the impurities.

Q4

4. What are the methods of extraction of metals?

The methods of extraction of metals are (i) Crushing and pulverization (ii) Concentration or dressing of the ore (iii) Calcination or roasting of the ore (iv) Reduction of metal oxides to free metal (v) Purification and refining of metal.

Quiz on Extraction Of Crude Metal From Concentrated Ore

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