Copper is extracted by hydrometallurgy from low grade, ores. It is leached out using acid or bacteria. The solution containing copper ions (Cu²⁺) is treated with scrap iron, zinc or H₂ as: 
\({Cu }^{ 2+ }(aq)+{ H }_{ 2 }(g)\longrightarrow Cu(s)+{ 2H }^{ + }(aq)\) 
\({Cu}^{ 2+ }+Fe(s)\longrightarrow Cu(s)+{ Fe }^{ 2+ }(aq)\)
In this way, copper is obtained.

The reaction is:
\({ Fe }_{ 2 }{ O }_{ 3 }+3C\longrightarrow 2Fe+3CO\)
Limestone is added as flux and the impurities of sulphur, silicon and phosphorus change to their oxides and pass into slag.

At temperatures above 1073 K,\(\Delta\)_fG⁰ (Fe,FeO) curve,i.e.,\(\Delta\)_fG⁰(C,CO)<\(\Delta\)_fG⁰(Fe,FeO),therefore,coke can reduce FeO to Fe

For the reaction
 \(2{ Cl }^{ - }(aq)+{ 2H }_{ 2 }O(l)\longrightarrow { 2OH }^{ - }(aq)+{ H }_{ 2 }(g)+{ Cl }_{ 2 }(g),\)
the value of \(\Delta G°\) is +422 kJ. Using the equation \(\Delta G°\) = \(-nE°F\), the value of \(E°\) comes out nearly to be -2.2 V. 
[+ 422 X 10³ J = -2 x 96500 x \(E°\)
\(E°\) = -2.2V]
Therefore, extraction of CI₂ from brine will require an external emf of greater than 2.2 volts.

van Arkel method is used for refining Zr and Ti. In this method, impure metal is heated with iodine which decomposes to give pure metal and iodine is recovered.     

\(Zr+2{ I }_{ 2 }\rightarrow Zr{ I }_{ 4 }\)     
(Impure) 

\(Zr{ I }_{ 4 }\overset { 1800\quad K }{ \rightarrow } Zr+2{ I }_{ 2 }\) 
                         (Pure)
\(\mathrm{T}_{1}+2 \mathrm{I}_{2} \longrightarrow \mathrm{T}_{1} \mathrm{I}_{4} \stackrel{1800 \mathrm{~K}}{\longrightarrow} \mathrm{T}_{1}+2 \mathrm{I}_{2}\) 
(Impure)                                 (Pure)