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Collectors like pine oil, fatty acids, xanthates enhance non wettability of mineral particles. 

Froth floatation process.

The ore of iron is hematite- Fe₂O₃ and the ore for copper is copper pyrites- CuFeS₂.

Extraction of chlorine from brine is based on oxidation.

Zinc blende is ZnS. For the extraction of zinc from zinc blende, the ore is first concentrated by the method of froth floatation. The concentrated ore is then roasted by heating the ore in the presence of oxygen to give ZnO releasing SO₂. The ZnS is further reduced using coke at temperature of 673 k giving zinc metal. 

2ZnS + 3O₂ → 2ZnO + 2SO₂ 

ZnO + C → Zn + CO 

Extraction of gold involves leaching the metal with CN- giving metal complex. 

4Au + 8CN^- (aq) + 2H₂O + O₂₍g) 4[Au(CN)₂] ^- (aq) + 4OH^- (aq)

The metal is later recovered by displacement method with zinc acting as reducing agent. 

2[ Au(CN)₂]^- (aq) + Zn(s) 2Au(s) + [Zn(CN)₄] ^- (aq)

2FeS + 3O₂ → 2FeO + 3O₂ 

FeO + SiO₂ → FeSiO₃ 

2Cu₂S + 3O₂ → 2Cu₂O + 2SO₂ 

2Cu₂O + Cu₂S → 6Cu + SO₂

According to Ellingham diagram the point of intersection of the curves of C, CO and Fe, FeO lies at temperature lower than that of the point of intersection of CO,CO₂ and Fe, FeO curves. This means the reduction of FeO will occur at much lower temperature with C than with CO. So C is preferred to CO for reduction. 

In magnetic separation ore is carried over a conveyer belt which passes over a magnetic roller. If either the ore or the gangue is capable of being attracted by the magnetic field then it will collect near the roller and the particles showing non magnetic behaviour will be collected away from the roller.

Minerals from which the element can be isolated economically. 

‘All ores are minerals, but all minerals are not ores’

The process used for the isolation of metal from its ore. 

Metallurgy involve the following major steps :

I. Concentration or Enrichment of ore 

II. Isolation of Metal from the concentrated ore 

III. Purification of the metal. 

Minerals are the naturally occurring chemical substances in the earth’s crust obtained by mining. Its different from ores, as ores are the minerals that are used for the extraction of metals profitably. 

The purest form of iron is wrought iron & is used in making anchors, wires, bolts etc.

Pig iron (4% C) is converted in cast iron by heating molten pig iron with scarp Fe and coke in Bessimer converted. A blast of hot air is below through the mixture. Cast iron contains 3% C, cast iron is very hard and brittle. 

The purest form of iron is wrought iron & is used in making anchors, wires, bolts etc.

Vapour phase refining is the method of metal refining by changing the metal into volatile compound that can be collected separately leaving behind the impurities and can be decomposed to give the pure metal.

The process used for the refining of gallium is zone refining and the principle underlying it is that the impurities are more soluble in the melt than in solid state of the metal.

Refining of metal is the process of purification of a metal extracted from its ore.

The process used for the refining of gallium is zone refining and the principle underlying it is that the impurities are more soluble in the melt than in solid state of the metal.

A low melting metal like tin can be made to flow on a sloping surface. In this way it is separated from higher melting impurities. 

Leaching is the process of extracting a substance from a solid by dissolving it in a liquid. In metallurgy leaching is used for the ores that are soluble in a suitable solvent.

Concentration of the Ore 

• Removal of Earthy impurities (sand, clay, soil…) 

• Earthy impurities are known as Gangue 

• Also known as Dressing Or Benefaction 

• The ores are graded and powdered to reasonable size. 

Purification of the Metal :

1. Distillation

2. Liquation

3. Electrolytic Refining

4. Zone Refining

5. Vapour Phase Refining

Leaching is the process of extracting a substance from a solid by dissolving it in a liquid. In metallurgy leaching is used for the ores that are soluble in a suitable solvent. 

Calcination:

(i) it involves heating of the ore in the absence of air 

(ii) it is generally used for carbonate ores 

Calcination: 

ZnCO₃ → ZnO(s) + CO₂

Roasting: 

(i) it involves the heating of the ore in the presence of air 

(ii) it is generally used for sulphide ores

Roasting: 

2ZnS + 3O₂→2ZnO + 2SO₂

Naturally occurring compounds of an element obtainable from the earth crust by mining is called Minerals.

Graphite rod acts as anode in the electrometallurgy of aluminium. Graphite anode facilitates reduction of Al₂O₃ to aluminium by electrolysis. Carbon reacts with oxygen liberated at anode producing CO and CO₂

At anode :

C (solid) + O^2- (melt) → CO(g) + 2e^-

C (solid) + 2O^2- (melt) → CO₂(g) + 4e^-

At cathode :

Al³⁺(melt + 3e^- → Al(I)

Used for removing Gangue from Sulphide ores. 

• Principle behind this process is the preferential wetting of ore particle with oil and gangue by water. 

• A suspension of powdered ore is made with water. 

• To this Collectors(oil, fatty acids etc) and froth stabilisers(cresols, aniline etc) are added 

• Minerals will be wet by oil while gangue by water 

• When the mixture is agitated froth will be formed which will carry the ore particles 

• It is possible to separate two Sulphide ores by using Depressants. 

Eg : In ore containing ZnS and PbS , NaCN acts as a Depressant & selectively prevents ZnS from coming to the froth but allows PbS to come with the froth. 

Methods of Concentration :

1. Hydraulic Washing 

2. Magnetic Separation

3. Froth Floatation Process 

4. Leaching-A chemical method 

The process of reducing a metal oxide with coke or with any other reducing agent at high temperature is called pyrometallurgy. 

The oxygen liberated at the anode during the reduction of alumina, reacts with the carbon of the anode to form CO and CO burns away the anode and hence the anodes need to be replaced.

Used when there is difference in gravities between ore and gangue. 

• Powdered ore is washed in an upward stream of running water. 
• The lighter gangue particles are washed away and heavier ores are left behind. 

The process of hydraulic washing is based on the differences in gravity of the ore and the gangue particles and so is known as gravity separation.

Van Arkel method is used for removal of impurities like oxygen and nitrogen from the metals like zirconium and titanium.

This is very useful for low boiling metals like zinc and mercury. The impure metal is evaporated to obtain the pure metal as distillate.

Distillation is used for the metals with boiling point lower then the impurities. So the metals can be evaporated and separately obtained as distillate.

Magnesium can reduce alumina at the temperature above the intersection point of the curves for Al₂O₃ and MgO in the Gibbs Energy vs T plot (Ellingham diagram). But the temperature at which this is feasible is too high to be achieved economically and is also technologically difficult. So this reduction is not done.

Magnesium can reduce alumina at the temperature above the intersection point of the curves for Al₂O₃ and MgO in the Gibbs Energy vs T plot (Ellingham diagram). But the temperature at which this is feasible is too high to be achieved economically and is also technologically difficult. So this reduction is not done.