Extraction of Crude Metal From Concentrated Ore

Metal extraction involves refining of metals from the gangue it is found with. Extraction of metals occur over three major stages.

  • Concentration of Ore<Provide link of this article>
  • Isolation of metal from the concentrated Ore
  • Purification of the metal<Provide link>

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

  • 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 remove volatile compounds from the ore leaving behind a metal oxide.

Fe2O3.xH2O(s)  \(\require{AMScd} \begin{CD} @>▲>> \end{CD} \) Fe2O3 (s) + xH2O(g)

CaCO3.MgCO3(s)   \(\require{AMScd} \begin{CD} @>▲>> \end{CD}           \) CaO(s) + MgO(s) + 2CO2(g)

  • Roasting: 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.

\(~~~~~~~~~~~\)2ZnS      +    3O2         \(\require{AMScd} \begin{CD}  @>▲>> \end{CD} \)     2ZnO + 2SO2 \(~~~~~~~~~~~\)2PbS      +     3O2    \(\require{AMScd} \begin{CD}  @>▲>> \end{CD} \)     2PbO + 2SO2 \(~~~~~~~~~~~\)2Cu2S    +     3O2    \(\require{AMScd} \begin{CD}  @>▲>> \end{CD} \) 2Cu2O + 2SO2

  • Reduction of Oxide to Metal: Reduction of metal oxide means removal of oxygen to refine metal to its free state. This is done with the help of reducing agents such as Carbon (C) and Carbon Monoxide (CO). Carbon is added to the metal oxide obtained from the ore and heated. The carbon under the right condition reacts with metal oxide and takes the oxygen with it thereby reducing the metal and leaving as carbon monoxide gas. If CO is used as reducing agent then the gas produced will be Carbon dioxide.

\(~~~~~~~~~~~\)MxOy    +      yC        \(\require{AMScd} \begin{CD}  @>▲>> \end{CD} \) xM + y CO \(~~~~~~~~~~~\)MxOy    +      yCO     \(\require{AMScd} \begin{CD}  @>▲>> \end{CD} \) xM + y CO2