There are about 80 metals present in periodic table. Noble metals silver and gold are used from ancient times. Other most widely used metals are iron, copper, zinc, lead. Ti is used in space technology. Our body contain iron, sodium, potassium, Magnesium metals. Aluminium is the most abundant metal present in the earth's crust. Gold, silver, platinum occur in native state due to their low reactivity. Whereas highly reactive metals like Cu, Zn, Fe, Al, Mg occur in nature in combined form as oxides, sulphides, carbonates, silicates etc.
          The metal which occur in combined state in nature is called "mineral". The mineral from which a metal is extracted profitably is called "ore". For example zinc blende is ore, but others are minerals (of zinc). The process of extracting a metal in pure state from its ore is metallurgy. Sand, clay, stones associated with ore is called gangue. The chemical substance used to fuse gangue to form slag is called flux. Metallurgy involves 3 steps. They are concentration of ore, extraction of metal and refining of metal.
I. Concentration of ore (ore dressing): The process of removal of unwanted gangue present in ore is called concentration of ore.
 

Some of the concentration methods are hand picking (sand, stones are picked by hand from the ore Haematite), Gravity concentration method (Alluvial sand present in gold, soil present in cassiterite are removed by water), liquation (used to separate easily fusible mineral particles from gangue eg. stibnite, antimony minerals), Electro-magnetic method (used to separate magnetic particles from non-magnetic particles. eg. gangue particles present in haematite, magnetite, wolframite impurity in tin stone are magnetic.)
       Another most popular method, froth- floatation method is used to concentrate sulphide minerals. In this process, finely powdered ore, water, pine oil, sodium ethylxanthate (frothing agent) are taken in a tank. The surface of ore particles is wetted by pine oil, sodium ethyl-xanthate forms as a layer on the surface of the ore particles. This suspension is agitated with air. The bubbles of the froth are stabilized by adding "Collectors". The gangue particles settle down at the bottom of the tank.
 

Conditioners like lime, Na₂CO₃ are also added to float the froth along with sulphide ore particles. Copper pyrites, iron pyrites are concentrated by this process.
Some times suplhide ore may contain unwanted metalic sulphide, which is to be separated. We use NaCN like depressants to separate unwanted sulphide. If the ore contains ZnS and PbS and is treated with NaCN, ZnS is not coming with the froth, as Na₂[Zn(CN)₄] complex is formed. So only PbS is coming with the froth.
 

II. Extraction of metals from the concentrated ores: C, CO, Ca, H₂, water gas, Al, electricity are used to reduce oxide, halide ores to get the metals.
ZnO + C     Zn + CO
Fe₂O₃ + 3CO    2 Fe + 3CO₂
UCl₄ + 2Ca  → U + 2CaCl₂
WCl₆ + 3H₂ → W+ 6HCl
2 NiO + [CO + H₂] → 2 Ni + CO₂ + H₂O
                             water gas
Cr₂O₃ + 2 Al → 2 Cr + Al₂O₃
Na, Ca, Al, F₂, Cl₂ are isolated by electrolysis. Oxides of Al, Cu, sulphides of Ag, Cu are extracted by leaching by using lechal agents like NaOH, H₂SO₄, NaCN etc.
Al₂O₃.2H₂O + 2NaOH → 2NaAlO₂ + 3H₂O

CuO + H₂SO₄  →  CuSO₄ + H₂O
2Ag₂ S + 8NaCN + 4O₂ → 2Na₂SO₄ + 4Na[Ag (CN)₂]
Smelting: The process of extraction of a metal in molten state directly from its roasted
ore by heating it with coke or CO and flux.
          PbO + C → Pb + CO
          Fe₂O₃ + 3CO → 2Fe + 3CO₂
Calcination: The process in which carbonate or bicarbonate ore is heated below its melting point in absence of air to get respective oxides.
During calcination, ore becomes porous, moisture, volatile impurities P, S, As are removed.

ZnCO₃  

 ZnO + CO₂
2NaHCO₃   Na₂CO₃ + CO₂ + H₂O

Roasting: The process in which ore is heated strongly below its melting point in presence of excess of air. Sulphide ores are converted into either oxides (oxidizing roasting), sulphates (sulphatizing roasting) or chlorides (chloridizing roasting).
           During roasting ore becomes porous, moisture, volatile impurities are removed.

2ZnS + 3O₂ → 2ZnO + 2SO₂
           ZnS + 2O₂   ZnSO₄
           Ag₂S + 2NaCl + 2O₂   2AgCl + Na₂SO₄
III. Refining of metals: Impure metals are obtained in metallurgy. Depending on the nature of impurities, suitable refining methods are used. Some of the methods are.
Poling: Impure molten metal is covered with carbon powder and is stirred with green
wood poles. Hydro carbons released from poles reduce metal oxides to metal.
            Cu & Sn metals are refined in this method.

Distillation: Zn, Cd, Hg containing non volatile impurities are taken in retorts. On distillation, these metals distill easily by leaving impurities.

Liquation: Sb, Sn are purified by liquation method.

Electrolytic refining: Cu, Ag, Au are refined by this method. In this method, impure metal is taken as anode and pure metal is taken as cathode. Acidified solution of the metal salt is taken as electrolyte. Pure metal is deposited on cathode, on passing electricity.

Zone refining: Silicon, Gallium, Germanium like elements are refined by this method. This method is based upon the difference in solubilities of impurities in molten metal (fractional crystallization). Impure metal rod is served by a heating coil.

By heating the rod electrically till the metal present in the heated zone, pure metal is collected at one end of the rod.
VAPOUR PHASE REFINING
In this method, the metal is first converted into volatile compound and then it is decomposed to get pure metal.
Mond Process: In this process Ni is converted to volatile Ni(CO)₄ and then decomposed to pure Ni.

Van Arkel Method: This method is used to refine Zr & Ti.

Zr + 2 I₂   ZrI₄


Furnaces: Furnace is the device in which high temperature is produced. It is made of iron and inner wall is lined with refractory material (which can withstand very high temperature without softening or melting. e.g.: Magnesia can withstand upto 2500°K.) There are acid, base, neutral refractory materials. Shaft furnace, muffle furnace, electric furnace, open hearth furnace, reverboratory furnace and blast furnace are used in industry.

Reverboratory furnace: Dome shaped furnace is constructed with firebricks. This furnace has 3 main parts, "fire box" (where fuel is burnt), a spacious, rectangular elevated space called "hearth"(where charge is heated by reverboration) and "chimney" (waste gases leave through this part). As heat from waste gases are regenerated, the efficiency of furnace is less. This furnace is used either for smelting or roasting or calcination. This furnace is used in the metallurgies of Cu, Pb and steel.
    

Blast furnace: It is 100 feet tall cylindrical furnace and has diameter about 25 feet. It is made of wrought iron and inside lined with firebricks. Charge is introduced into furnace through the double cup and cone arrangement present at the top. Hot air is blown through tuyers present at bottom. 400°C to 1500°C temperature is found at different regions of the furnace. An outlet is provided to expel waste gases, near the top of the furnace. Hearth is present at the bottom where products are obtained in molten state. Molten metal can be taken out through top hole and slag through slag notch. Cu, Pb, Fe ores are smelted in this furnace.
 

Thermodynamic Principles of Metallurgy:
Metallurgical reactions can be understood by basic concepts of thermodynamics like change in Gibbs energy (ΔG).
ΔG = ΔH - T ΔS
Where ΔH = change in enthalpy, ΔS = change in entropy.
Also ΔG = -RT lnK
Where K = equilibrium constant at a temperature T
If ΔG = -ve (reaction proceeds) ΔG will be negative when ΔH & ΔS are positive and T is increased (ΔH < T ΔS). If two are more reactions are occuring together in a system and the net sum of ΔG of all the reactions is -ve then the overall reaction will takes place.
Such combined reactions are easily understood by "Ellingham Diagram". It is the graphical representation of Gibbs Energy. Graph is obtained when it is plotted ΔG Vs T. This  diagram not only helps in predicting the feasibility of thermal reduction of ore but also helps in the selection of reducing (suitable) agent for the metallic oxide.
If ΔG = -ve, the reduction of ore is feasible.
M_xO (s)   xM (s or l) + 1/2 O₂ (g)
M_xO (s) + C (s)  xM (s or l) + CO (g)
M_xO (s) + CO (g)  xM (s or l) + CO₂ (g)
M_xO (s) + 1/2 C (s)  xM (s or l) + 1/2 CO₂ (g)

Extraction of Iron:
Important minerals of iron are Haematite (Fe₂O₃) and Magnetite (Fe₃O₄). Charge (ore + coke + lime) is introduced into blast furnace through cup & cone arrangement (present at the top). Hot air is blown from the bottom of furnace through tuyers. The temperature at the lower portion of the furnace is about 2,200 K. The reactions at upper portion of the furnace (500 - 800 K) are
3 Fe₂O₃ + CO  2 Fe₃O₄ + CO₂
Fe₃O₄ + 4 CO  3 Fe + 4 CO₂
Fe₂O₃ + CO  2 FeO + CO₂
At 900 - 1500 K:
C + CO₂  2 CO
FeO + CO  Fe + CO₂
Lime stone is used as flux, which remove SiO₂ gangue to form molten slag (separated from iron at the botton of the furance).
CaCO₃  CaO + CO₂
CaO + SiO₂  CaSiO₃ (slag)

Iron obtained from blast furnace is called pig iron, which contains 4% carbon and S, P, Si, Mn impurities in small quantities.
Cast Iron is obtained by melting pig iron with coke and scrap iron. Cast iron consists 3% carbon. This iron is extremely hard & brittle.
Wrought iron (Malleable iron) is the purest form of iron (0.3% C is present). It is prepared by heating cast iron with lime stone in reverberatory furnace. Impurities Si, P, S are oxidised and passed into the slag.
Uses of Iron
Cast Iron: It is used for casting stoves, toys, gutter pipes, railway sleepers, steel and wrought iron.
Wrought Iron: It is used for making anchors, wires, bolts, chains and agricultural implements.
Steel: Nickel steel is used for making cables, automobiles, aeroplane parts, pendulum, measuring tapes. Chrome steel is used for cutting tools, crushing machines. Stainless steel is used for cycles, automobiles, pens, utensils.

Extraction of Copper
It is very clear from Ellingham Diagram that Cu₂O could be reduced easily by heating it with coke.
Cu is mainly extracted from copper pyrites (CuFeS₂). As this ore is sulphide ore, it is concentrated by froth flotation process.
Concentrated ore is roasted on the hearth of the reverberatory furnace after mixing it with silica.
Cu₂S . Fe₂S₃ + O₂ 

 Cu₂S + 2 FeS + SO₂
2 Cu₂S + 3 O₂  2 Cu₂O + 2 SO₂
2 FeS + 3 O₂  2 FeO + 2 SO₂
The roasted ore is mixed with coke and silica and smelted in blast furnace.
2 FeS + 3 O₂  2 FeO + 2 SO₂
FeO + SiO₂  FeSiO₃ (slag)
Cu₂O + FeS  Cu₂S + FeO
"Copper matte" (has more Cu₂S & little FeS) is formed in blast furnace. Copper matte is heated in Bessemer Converter by blowing a blast of hot air and sand. The solidified copper has blistered appearance due to evolution of SO₂ is called "Blister Copper".
2 Cu₂O + Cu₂S  6 Cu + SO₂
Blister Copper is refined by electrolysis to get 100% pure copper.

Uses of copper: Cu is used in electrical industry, in making alloys like brass (60% Cu + 40% Zn), Bronze (75% - 90% Cu + 10% - 25% Sn) and coins (with Ni).
Extraction of Zinc
Zn is mainly extracted from Zinc blende (ZnS). Finely crushed ore is concentrated by gravity separation, electromagnetic separation and froth flotation.
The concentrated ore is roasted to get ZnO.
ZnS + 2 O₂  ZnSO₄
2 ZnSO₄  2 ZnO + 2 SO₂ + O₂
2 ZnS + 3 O₂ 

 2 ZnO + 2 SO₂
ZnO is reduced with coke in retorts by Belgian process at 1673 K.
             _{1673 K}
ZnO + C        Zn + CO
Zn spelter formed in the retorts consist Cd & Pb impurities. It is refined by electrolytic method to get pure Zn.
Uses of Zinc: Zinc is used in paints, ayurvedic medicines, batteries, for galvanising iron, for alloys like brass (60% Cu & 40% Zn), German Silver (25% - 40% Cu, 25% - 35% Zn, 40% - 50% Ni).

Extraction of Aluminimum
Al is mainly extracted from bauxite. Bauxite may contain SiO₂ or iron oxides as impurities. Powdered ore is concentrated by NaOH solution (lechal agent) at 35 - 36 bar pressure and
473 K - 523 K temperature to get sodium aluminate.
Al₂O₃ + 2 NaOH + 3 H₂O  2 Na [Al(OH)₄]
Sodium aluminate is alkaline in nature, neutralised by CO₂ gas.
2 NaAl(OH)₄ + CO₂  Al₂O₃ . x H₂O + 2 NaHCO₃
Hydrated alumina is filtered, dried and ignited to give pure Al₂O₃.

         

                  _{1470 K}
Al₂O₃ . x H₂O     Al₂O₃ + x H₂O
Purified Al₂O₃ is refined by Hall - Heroult (electrolysis) process. CaF₂ (fluorspar) is added to Al₂O₃ to lower the fusion temperature and cryolite (Na₃AlF₆) is added to increase conductivity. This mixutre is taken in steel vessel coated with carbon lining acts as cathode and graphite acts as anode and is electrolysed.
2 Al₂O₃ + 3 C  4 Al + 3 CO₂
Reaction at anode: Al⁺³ + 3 e^- 

 Al
At cathode: C + 2 O^-2  CO₂ + 4 e^-
Uses of Aluminium: Al foils are used as wrappers for chocolates. Al is used in silver paint. Al wires are used as electrical cables. Al is used in thermite welding.