EXTRACTION OF METALS

Contents

• Introduction
• Extraction of Metals
• Ore Processing and Concentration
• Methods of Extraction of metals
• Purification and refining of extracted metals
• Extraction of some common metals
• Summary
• Key Terms
• Recommended Videos
• Test Questions
• Discuss And Explain

Learning Objectives

By the end of this section, you should be able to:

• Differentiate ore and minerals.
• Explain processes of extraction.
• Explain types of extraction.
• Explain methods of refining and purification.

Introduction

Metals and their alloys are extensively used in our day-to-day life. They are used for making machines, railways, motor vehicles, bridges, buildings, agricultural tools, aircrafts, ships etc. 

Therefore, production of a variety of metals in large quantities is necessary for the economic growth of a country.

While some metals occur naturally in free state, many others are combined with the natural elements present in nature.

The main active substances present in nature, especially in the atmosphere are oxygen, carbon(IV) oxide and moisture. In the earth's crust, sulphur and silicon are found in large quantities.

Metals that have low reactivity hardly combine with air, water, carbon(IV) oxide or other non-metals that are present in nature.

Such metals may remain in elemental or native (free) state in nature. Examples of such metals are gold, silver, mercury and platinum. They are called noble metals.

On the other hand, most other metals are active and they combine with air, moisture and non-metals that are present in nature to form compounds, that is, they occur in combined states in nature.

A natural material in which a metal or its compound is found is called a mineral.

A mineral from which enough of a metal can be extracted for profit is called an ore. 

An ore is a mineral in which a metal is present in relatively appreciable quantities.

Ores are usually found together with rocky or earthy impurities. These rocky or earthy impurities accompanying the ores are called gangue or matrix.

Metals are non-viable and non-useful in their ore form, hence they need to be separated from the other constituents found in the ores; the process of separating a metal from other constituents in its ore is called extraction.

Extraction of Metals

Metals need to be extracted from ores before they can be turned into useful products. The extraction of metals and minerals is even the fifth-largest industry in the world. The South African mining industry alone employs close to a million people. 

Mining for ores is expensive and so it is only carried out where minerals are abundant enough for this to be profitable.

However, the value of ores changes over time due to society and technology.

The processes of extracting metals deal with chemistry and that is why we're studying it here today. Metals are separated from the other elements that they are combined with using chemical methods.

There are three methods that can be used to extract different metals from their ores

These three methods are:

• Electrolysis (called Electrometallurgy).
• Reduction by Burning, or Thermal Reduction (called Pyrometallurgy).
• Hydrometallurgy.

However, these chemical processes cannot be carried out on a 'just excavated' ore. The ore needs to first undergo some processing

Ore Processing and Concentration 

The first step to carry out when an ore is gotten is to crush and grind it.

Ores are big chunks of materials and they cannot be processed in bulky form, hence they are grinded and crushed using jaw crushers or grinders.

Jaw crusher grinding ore | photo credit: 911metallurgist

When the ore has been grinded, the crushed pieces of the ore are then pulverized (powdered) in a stamp mill.

Stamp mill powdering ore | photo credit: 911metallurgist

By now, the ore is in its powdered form, and will then be taken out of the stamp mill.

Pulverization can also be carried out in a ball mill. 

Here, the crushed ore is taken in a steel cylinder containing iron balls. The cylinder is then initiated to start rolling. This will make the striking balls inside the cylinder to pulverize the crushed ore into fine powder.

Inside a ball mill | photo credit: 911metallurgist

What comes next is the concentration of the ore. 

The process of removal of gangue (unwanted impurities) from processed ore is called ore concentration or ore dressing. 

There are several methods for concentrating ores; the method that is used depends on the nature of the ore. 

Some important methods are:

Hydraulic washing

In this method, the ore is washed and mixed thoroughly in water. The heavier ore settles down rapidly and the lighter sandy and earthy materials (gangue particles) are washed away. This method is used for heavy oxide ores.

Magnetic separation method

In this method, ores are concentrated by exploiting magnetic properties of either the ore itself or the impurities. Magnets are used to separate magnetic ores from impurities or the other way round.

Froth Floatation method

This method is used for removing gangue in sulphide ores. 

In this method, finely powdered ore is mixed with either pine oil or eucalyptus oil. It is then mixed with water. 

Air is blown through the mixture with a great force. 

Froth is produced in this process which carries the wetted ore upwards with it. 

Impurities (gangue particles) are left in water and they sink to the bottom.

Froth Floatation | photo credit: 911metallurgist

Chemical method or Solvent extraction

In this method, the powdered ore is dissolved in a solvent. The ore dissolves leaving behind the impurities which cannot dissolve and are therefore removed. The ore is then recovered using suitable chemical method.

In the end we have a pure form of the ore. We can now go ahead to use any of the three extraction methods mentioned above.

Methods of Extraction of metals

How do we know which method to use?

The reactivity of a metal determines how it is extracted.

Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
(Carbon)
Zinc
Iron
Tin
Lead
(Hydrogen)
Copper
Silver
Gold
Platinum

Metals above carbon in the reactivity series must be extracted using electrolysis.

Metals less reactive than carbon are extracted from their ores by Thermal Reduction.

Electrometallurgy

Electrometallurgy involves the use of electrolysis to separate a metal from its other constituent.

Electro - electricity

Lysis - disintegration, breakdown

Electrolysis involves using electricity to split the elements of a compound.

Any metal can be separated from its ore by electrolysis, but electrolysis is very expensive and so it is only used to extract reactive metals that cannot be extracted in other ways.

Metals above carbon in the reactivity series (shown above) are extracted from their ores by electrolysis.

Simple model of an electrolytic setup

During electrolysis there are two poles called electrodes, and an electrolyte which will be the molten/liquid form of the ore we want to extract a metal from.

When electricity is passed through the electrolytic cell, the metallic ions (which are the positive ions) move and collect at the cathode, while the negative ions (the other non-metallic constituent) is collected at the anode.

Read more on this in Electrolysis.

Pyrometallurgy

Pyrometallurgy 

Pyrometallurgy involves systematic processes of heating an ore at high temperatures until the metal (that is to be extracted) is separated from its other constituents.

Elements below carbon in the reactivity series undergo Pyrometallurgy.

Pyrometallurgy involves two major processes:

1. Conversion of ore to Oxide.
2. Reduction of Oxide to pure metal.

Conversion of ore to Oxide

Different ores can be converted to their oxide form by using any of these two methods:

Calcination: involves heating of the concentrated ore in absence or limited supply of air so that it loses moisture, water of hydration and gaseous volatile substances. 

The ore is heated to a temperature that is less than its melting point so that it does not melt.

Roasting: involves heating of the concentrated ore in open or free supply of air at a temperature that is below the melting point of the metal.

The major aim of calcination and roasting is to convert the ore into a simple form that can be reduced.

Calcination and roasting are usually carried out in a reverberatory furnace or in a multiple hearth furnace.

Differences between calcination and roasting | photo credit: pediaa

Reduction of Oxide to pure metal

Reduction of oxide to pure metal is carried out after calcination or roasting of ores. 

This process is usually referred to as smelting; the oxide ores are converted into pure metals by reduction.

Smelting: Smelting is a process in which the oxide ore (in molten state) is reduced by reducing agents (in the presence of flux) to give a pure metal.

Reducing Agents or Reductants

Reducing agents or Reductants are responsible for taking off oxygen from a metal oxide to give only the pure metal.

There are different reducing agents that can be used during smelting process:

Carbon / Carbon(II) oxide

This method is used for the extraction of iron, tin and zinc metals from their respective oxides. The metallic oxides are strongly heated with charcoal or coke. Reduction occurs by the action of carbon and/or carbon(II) oxide which is produced by the partial combustion of coke or charcoal.

$${\text{Fe}}_2{\text{O}}_3+3\text{C}\to 2\text{Fe}+3\text{CO}$$ $${\text{Co}}_3{\text{O}}_4+4\text{C}\to 3\text{Co}+4\text{CO}$$ $${\text{Co}}_3{\text{O}}_4+4\text{CO}\to 3\text{Co}+4{\text{CO}}_2$$ $$\text{PbO}+\text{C}\to \text{Pb}+\text{CO}$$

Aluminium, Sodium, Magnesium or Hydrogen

Oxide ores which cannot be reduced by carbon, or, metals which show affinity for carbon by forming metal carbides; are reduced by reducing agents like aluminium, sodium, magnesium or hydrogen. 

Oxides like chromium oxide (Cr₂O₃) or manganese oxides (Mn₃O₄) are reduced by aluminium powder in a very heated condition.

This process is known as Goldschmidt's Alumino-thermite reduction method.

$${\text{TiCl}}_4+2\text{Mg}\to \text{Ti}+2{\text{MgCl}}_2$$ $${\text{Cr}}_2{\text{O}}_3+2\text{Al}\to 2\text{Cr}+{\text{Al}}_2{\text{O}}_3+\text{heat}$$ $$3{\text{Mn}}_3{\text{O}}_4+8\text{Al}\to 9\text{Mn}+4{\text{Al}}_2{\text{O}}_3+\text{heat}$$

Water Gas (CO + H₂)

Water gas is the reducing agent that is used during reduction of Nickel oxide to give pure Nickel.

Nickel oxide, obtained from roasting of Nickel sulphide is heated carefully in a tower at 350°C in which there's a current of water gas.

Roasting of NiS: $$\text{NiS}+{\text{O}}_2\to \text{NiO}+{\text{SO}}_2$$ Reduction of NiO: $$2\text{NiO}+\text{CO}+{\text{H}}_2\to 2\text{Ni}+{\text{H}}_2\text{O}+{\text{CO}}_2$$

Self Reduction

Here there's no addition of any reducing agent. This is applied to the sulphide ores of copper, mercury and lead. 

When the ores are heated in air, a part of these sulphide ores change into the oxide or sulphate, which will then react with the remaining part of the sulphide ore (in the absence of air) to form the pure metal and Sulphur(IV) oxide.

Self Reduction in Lead ore

Roasting in air: $$2\text{PbS}+3{\text{O}}_2\to 2\text{PbO}+2{\text{SO}}_2$$ $$\text{PbS}+2{\text{O}}_2\to {\text{PbSO}}_4$$ When air is cut off: $$\text{PbS}+2\text{PbO}\to 3\text{Pb}+{\text{SO}}_2$$ $$\text{PbS}+{\text{PbSO}}_4\to 2\text{Pb}+2{\text{SO}}_2$$

Self Reduction in Copper ore

Roasting in air: $$2{\text{Cu}}_2\text{S}+3{\text{O}}_2\to 2{\text{Cu}}_2\text{O}+2{\text{SO}}_2$$ When air is cut off: $$2{\text{Cu}}_2\text{O}+{\text{Cu}}_2\text{S}\to 6\text{Cu}+{\text{SO}}_2$$

Flux

Flux is any substance that is used during smelting of an ore to ensure there's uniform fluidity and to remove impurities in the form of slag.

There are two types of flux:

• Acidic Flux
• Basic Flux

 Acidic flux: acidic flux is used to remove basic (or alkaline) gangue (basic gangue contain lime or other metallic oxides). Examples of acidic fluxes are silica, borax etc

Silica reacts with lime impurities to form a type of slag: $${\text{SiO}}_2+\text{CaO}\to {\text{CaSiO}}_3$$

Basic Flux: basic flux is used to remove acidic gangue (silica, silicates, aluminates, etc.). Examples of basic fluxes are CaCO₃, MgCO₃.

Limestone reacts with silica impurities to form slag and carbon(IV)oxide: $${\text{CaCO}}_3+{\text{SiO}}_2\to {\text{CaSiO}}_3+{\text{CO}}_2$$

How elements at the base of the reactivity series are extracted

Elements at the base of the reactivity series include elements like silver, mercury etc

They are extracted from their ores using any of these two simple processes

Heating the ore: silver and mercury compounds are unstable and will decompose to the metal on heating.

Silver sulphide is heated in presence of air to give Silver and Sulphur(IV)oxide: $$\text{AgS}+{\text{O}}_2\to \text{Ag}+{\text{SO}}_2$$

Chemical or Solvent method: here, silver ore (for example) is dissolved in a solvent. A metal that is higher in the reactivity series (like calcium) is then added to the solution. The added metal will displace silver from its constituent, hence yielding pure silver.

Hydrometallurgy

Hydrometallurgy is a form of extraction method that make use of aqueous solutions to separate metals from their ores.

Three processes are involved in hydrometallurgy:

1. Leaching
2. Solution concentration and purification
3. Metal or metal compound recovery

Leaching involves the process of treating ore with water or other agents such as H₂SO₄, HCl, NaOH, Na₂CO₃, FeCl₃ etc

After leaching, the leach liquor (or leachate) must undergo concentration of the metal ions that are to be recovered.

Afterwards, the metal component is recovered from the concentrated leach liquor.

The primary types of metal recovery processes are electrolysis, gaseous reduction, and precipitation.

Purification and refining of extracted metals

Except in the electrolytic reduction method, metals produced by any other method are generally impure. 

The impurities may be in the form of:

• Other metals
• Unreduced oxide of the metal
• Non-metals like carbon, silicon, phosphorus, Sulphur etc
• Flux or slag.

Crude metal may be refined by using one or more of the following methods:

Liquation

Metals with low melting points like tin, lead etc. are refined by this process. In this method, the impure metal is heated slowly to a temperature that is slightly above the melting point of the metal. The pure metal drains out leaving behind non-melted impurities.

Poling

Poling involves stirring the impure molten metal with green logs or bamboo. The hydrocarbons contained in the pole reduce any metal oxide present as impurity. 

Distillation

Volatile metals like zinc and mercury are purified by distillation. The pure metal distils over, leaving behind non-volatile impurities.

Electrolytic Refining

A large number of metals like copper, silver, zinc, tin etc are refined by electrolysis. 

A block of the impure or crude metal is made the anode and a thin sheet of the pure metal forms the cathode of the electrolytic cell containing suitable metal salt solution which acts as an electrolyte. 

On passing current, the (impure metal) anode dissolves and pure metal deposits at the cathode sheet while impurities are left in solution.

Extraction of some common metals

Extraction of Sodium

Sodium

Sodium is very reactive and does not occur naturally in a pure form. It occurs as;

• Sodium carbonate (soda ash), Na₂CO₃
• Sodium nitrate NaNO₃
• Sodium chloride (rock salt) NaCl

Sodium chloride is the main ore from which sodium is extracted.

Sodium metal is extracted by electrolysis of fused or molten sodium chloride (brine); using a modified electrolytic apparatus called Down's cell.

Down's cell | photo credit: libretext

Sodium chloride is placed in the Down's cell;

Calcium chloride is added to lower the melting point of sodium chloride (from 800°C to about 600°C). This saves electrical energy and therefore makes the process more economical. 

A steel cathode and a carbon (graphite) anode are used. 

A very high current is used to keep the sodium chloride in molten state, allowing the sodium ions and chloride ions to move.

At the cathode;

Sodium ions gain electrons and sodium metal is deposited and collected. A grey solid is formed/deposited on the cathode.

Equation for Reaction at the cathode:

$${\text{Na}}_{(aq)}^{+}+{\text{e}}^{-}\to {\text{Na}}_{(l)}$$

At the anode;

Each chloride ion loses an electron and combine with another chloride ion to form chlorine gas; Bubbles of yellowish-green gas form at the anode.

 Equation for Reaction at the anode:

$$2{\text{Cl}}_{(aq)}^{-}\to {\text{Cl}}_{2(g)}+2{\text{e}}^{-}$$

Note: At 600°C, sodium and chlorine would react violently together to reform sodium chloride. To prevent this reaction, Down's cell contains steel gauze around the graphite anode to keep the constituent present in the cathode apart. 

Chlorine gas produced as a by-product is collected in a cylinder. 

Molten sodium collects in the inverted trough, placed over the cathode, rises up the pipe, and is tapped off and collected under dry nitrogen. 

Nitrogen is inert under ordinary conditions and therefore hardly reacts with sodium. 

This process is called Down’s Process.

Uses of sodium metal

 • It is used in the manufacture of anti-knock compound, tetraethyl lead, added to petrol (regular) to make it super which does not make the engine knock. “Knocking” in a car engine is caused by petrol and air mixture burning too rapidly in the cylinders, giving sudden blow or knock to the piston, which is not good for the engine. Tetraethyl lead slows down the combustion process of a mixture of petrol and air.

 • It is used in manufacture of sodium cyanide which is used in extraction of gold.

 • It is used in nuclear reactions to absorb some of the heat produced during the reactions.

Extraction of Lithium

Lithium

Lithium is very reactive, a direct cousin to sodium and it does not occur naturally in nature. It occurs as;

• Petalite LiAl(Si₂O₅)₂
• Lepidolite K(LiAl)₃(Al, Si, Rb)₄ O₁₀(F,OH)₂
• Spodumene LiAl(SiO₃)₂
• And other subsurface brines.

Lithium is extracted from its brines by several complex processes, of which many involve electrolysis and/or hydrometallurgy.

Uses of Lithium

• Battery production
• Production of glass
• Production of some Aluminium products

Extraction of Magnesium

Magnesium

Magnesium is also a reactive metal and does not occur freely in nature. It occurs as;

• Dolomite MgCO₃·CaCO₃
• Magnesite MgCO₃
• Epsom salt MgSO₄·7H₂O
• Carnalite KCl·MgCl₂·6H₂O

Magnesium is extracted by electrolysis and can also be gotten from dolomite by method of thermal reduction.

Uses of Magnesium

• Magnesium ignites easily in air and it is used in flares, sparklers, fireworks.
• It is used in the manufacture of light weight objects such as laptops, cameras, etc 
• It is also added to molten iron and steel to remove sulphur.

Extraction of Aluminium 

Aluminium

Aluminium does not occur freely in nature. It occurs as;

• Bauxite Al₂O₃·2H₂O
• Cryolite Na₃AlF₆
• Kaolin (common clay) 3Al₂O₃·6SiO₂·2H₂O
• Alunite K₂SO₄·Al₂(SO₄)₃·4Al(OH)₃
• Feldspar KAlSi₃O₅

Aluminium is extracted by electrolysis

Aluminium occurs majorly as bauxite [Al₂O₃·2H₂O].

Impurities are removed by heating bauxite with sodium hydroxide solution.

Pure form of Al₂O₃ is gotten which will now undergo electrolysis.

Al₂O₃ is mixed with molten cryolite (Na₃AlF₆) (=lowers melting point of Al₂O₃ and acts as solvent).

During electrolysis, Aluminium gains electrons and move to the cathode, while oxygen loses electrons, combines with another oxygen atom to form oxygen gas which will collect at the anode.

Extraction of Potassium

Potassium

Potassium does not occur freely in nature. It occurs as;

• Nitre (salt peter) KNO₃
• Carnalite KCl·MgCl₂·6H₂O

Potassium is extracted by electrolysis.

Extraction of Iron

Iron | photo credit: tomihandorf

Iron does not occur freely in nature. It occurs as;

• Iron pyrite FeS₂
• Haematite Fe₂O₃
• Ignetite Fe₃O₄
• Rust Fe₂O₃·XH₂O
• and many others 

Iron is extracted by thermal (burning) reduction in a blast furnace, using carbon as a reductant and limestone as a flux.

Limestone helps in the removal of impurities from iron. At high temperature in the furnace, limestone (CaCO₃) decomposes into lime (CaO) and CO₂. CaO then reacts with impurities that are present in the iron ore.

CaSiO₃ and/or CaAl₂O₄  are formed when lime react with (silicate and aluminate) impurities; these in their molten form are referred to as ‘slag’ or waste product.

Carbon reduces iron oxide to iron and carbon (IV) oxide: $$\text{C}+{\text{O}}_2\to {\text{CO}}_2$$ $${\text{CO}}_2+\text{C}\to 2\text{CO}$$ $$3{\text{Fe}}_2{\text{O}}_3+\text{CO}\to 2{\text{Fe}}_3{\text{O}}_4+{\text{CO}}_2$$ $${\text{Fe}}_3{\text{O}}_4+\text{CO}\to 3\text{FeO}+{\text{CO}}_2$$ $$\text{FeO}+\text{CO}\to \text{Fe}+{\text{CO}}_2$$ CO reduces iron oxide in the upper part of the furnace

Limestone is decomposed into lime and carbon(IV) oxide: $${\text{CaCO}}_3\to \text{CaO}+{\text{CO}}_2$$ Lime acts as a basic flux and react with silicate and aluminate impurities: $$\text{CaO}+{\text{SiO}}_2\to {\text{CaSiO}}_3$$ $$\text{CaO}+{\text{Al}}_2{\text{O}}_3\to {\text{CaAl}}_2{\text{O}}_4$$

Slag flows to the bottom of the furnace where it floats on the molten iron and tapped off at a different level separately from the iron.

Slag is used for road making materials, cement and light weight building materials.

Blast furnace and reactions | photo credit: openstax

Iron that is obtained from thermal reduction is not pure and it is called Pig iron. 

It is hard but brittle and melts at 1227°C.

Cast iron is a more purified form of iron and it is formed when Pig iron is re-melted, mixed with scrap steel and cooled in moulds.

Wrought iron is the purest form of iron and it is obtained from cast iron by heating it with iron(III) oxide in a furnace lined with limestone. 

Iron(III) oxide supplies oxygen for the oxidation process.

Wrought iron is malleable. It is very tough and therefore can withstand some strain. It can be used to make iron nails, iron sheets and agricultural implements.

Steel is an alloy (=mixture of two or more metals) of pure iron with a small percentage of carbon and other elements. Other elements such as tungsten, chromium, nickel and manganese are added to produce different types of steel with different properties.

Extraction of tin

Tin

Tin occurs in nature as:

• Cassiterite (Tin stone) SnO₂
• Stannite Cu₂FeSnS₄
• Cylindrite PbSn₄FeSb₂S₁₄

Tin is usually extracted by reduction with carbon.

Uses of Tin

• Coating of other metals to prevent corrosion.
• Soldering of steel.
• Manufacturing of other alloys.

Extraction of Lead

Lead

Lead occurs in nature as:

• Galena PbS
• Pyromorphite Pb₅(PO₄)₃Cl

Lead is extracted from its ore by reduction with carbon.

Uses of lead

• Car batteries
• Ammunition
• Cable insulation
• Crystal glass formation
• Radiation protection
• Solder wire
• Lead pipes

Extraction of Zinc

Zinc

Zinc occurs in nature as:

• Zinc blende (sphalerite) ZnS
• Zincite ZnO
• Franklinite ZnO(Fe,Mn)₂O₃
• Calamine Zn₂(OH)₂SiO₃
• Smith stone ZnCO₃

Zinc blende is the most common ore of zinc. Converted to ZnO by roasting, which will then be reduced by smelting with carbon to yield Zinc.

Uses of Zinc

• Galvanization of iron
• Brass formation
• Pharmaceuticals
• Plastics
• Cosmetics
• Batteries and other chemicals

Extraction of copper

Copper

Copper occurs in nature as:

• Chalcopyrite CuFeS₂
• Malachite CuCO₃·Cu(OH)₂
• Cuprite Cu₂O
• Azurite 2(CuCO₃)·Ca(OH)₂
• Tennanite Cu₂As₄S₁₃
• Dioptase CuSiO₂ (OH)₂
• Digenite Cu₉S₅
• Covelite CuS
• Chalcocite Cu₂S

There are several methods that are used to derive copper from its ores and this depends on the nature of the ore. The principal process is by reduction. Copper gotten from reduction is then purified by electrolysis.

Uses of Copper

• Used extensively in wiring and motors.
• Used in construction and industrial machineries.

Extraction of Calcium

Calcium

Calcium occurs in nature as:

• Calcite (Limestone) CaCO₃
• Dolomite MgCO₃·CaCO₃
• Gypsum CaSO₄·2H₂O
• Anhydrite CaSO₄

Calcium must be extracted through electrolysis.

Uses of calcium

• Cement and mortar production
• Making some steel and glasses.

Extraction of Titanium

Titanium

Titanium occurs in nature as:

• Anatase TiO₂
• Brookite TiO₂
• Ilmenite FeTiO₃
• Leucoxene is mixture of iron and titanium oxides
• Perovskite CaTiO₃
• Rutile TiO₂
• Sphene CaTiSiO₅

Titanium is mostly extracted from rutile and the extraction is carried out using Kroll and Hunter processes.

Titanium is extracted by thermal reduction.

Carbon can’t be used as a reducing agent for the extraction of titanium from its ore because titanium reacts further with carbon, so a more reactive metal, (e.g. sodium or magnesium), is used to reduce the titanium ore instead.

Uses of titanium

• Jeweleries.
• Surgical tools.
• Mobile phones.
• Hip joint replacement.
• Tooth implant.
• Fighter jets.

Key Points

💎Extraction involves the separation of a metal from its mineral constituents and impurities.

💎Ores are big chunky materials that contain enough of metal that it can be extracted for profit.

💎There are 3 types of extraction:

• Electrometallurgy
• Pyrometallurgy
• Hydrometallurgy

💎Before a metal can be extracted from its ore, the ore need to be grinded, pulverized and concentrated.

💎Several factors contribute to what type of method to use for extracting a metal from its ore. The most principal factor is the position of the metal in the reactivity series.

💎Electrometallurgy involves the use of electricity to separate a metal from its other constituents in the ore.

💎Pyrometallurgy involves burning the ore in the presence of a reductant and flux to give rise to the pure metal.

💎Hydrometallurgy involves the use of aqueous solutions and chemicals to dissolve the ore and then concentrate the metal to be extracted, which will now be separated using suitable techniques.

💎Metal derived from extraction methods asides electrolysis is impure and it further undergoes purification and refining to give pure metal.

Key Terms

Mineral • Noble Metal • Ore • Gangue • Matrix • Electrometallurgy • Electrolysis • Pyrometallurgy • Calcination • Roasting • Smelting • Reductants • Flux • Acidic flux • Basic flux • Slag • Hydrometallurgy • Leaching

Watch these Videos

Extraction of metals 

Extraction of iron

Extraction of sodium

Extraction of Aluminium

Test your understanding of this lecture

Discuss And Explain

1. Name the metal oxides that are not reduced to metallic state by heating with carbon. Which reducing agent is used for these ores?

2. Name four reducing agents other than carbon, used during smelting.

3. What is the difference between calcination and roasting?

4. State the nature of materials used for constructing cathodes and anodes in the electrolytic cell for refining of copper. Write chemical equations for the reactions which take place.

5. Which method is used for the refining of metals that are easily fused?

6. Which is the cheapest and most abundant reducing agent employed in the extraction of metals?

7. Name few materials which are used as flux in metallurgical processes.

8. What is the difference between an ore and a mineral?

9. Write the names of eight important metals. Give an example of one important ore of each metal.

10. Describe the froth floatation method for the concentration of sulphide ore.

11. Describe a method for refining nickel.

12. Sodium metal is extracted by electrolysis of fused sodium chloride to which calcium chloride has been added.
a) Give a reason for the addition of calcium chloride.

b) Name a material that can be used as the cathode and another that can be used as the anode.

c) Write equations for the reaction that take place at each electrode.

d) Describe how the product at the cathode is collected.

e) Name one other element that can be extracted by similar method.

13. Iron is extracted by a reduction process in the blast furnace.

a) Name two raw materials used besides the iron ore.

b) Write the equation leading to the production of iron from its ore.

c) State one use of iron.