Tag: principles of metallurgy

 The three steps involved in extraction are:
1) Concentration of the ore to remove impurities.
2) Reduction of the ore to get the metal.
3) Purification of the ore.

Melting (Change of solid into liquid) - The change of solid into liquid due to increase in temperature is known as melting. Ice, which is a solid melts, i.e. changes into water. 
Similarly, when solid wax gets heated it converts into liquid and this is melting process.

Refining and magnetic separation are methods of extraction of metals .Enrichment of ore is also known as concentration of ore. It means purification of ore.

Impurities are removed prior to the extraction of metal. The process used for removal of gangue from the ore are based on the differences between physical and chemical properties of the gangue.

During roasting, the sulphide ores are converted into oxides by heating strongly in excess of air.
$ZnS + 3O _2 \rightarrow 2ZnO + 2SO _2$

Reduction is the process of removal of oxygen for extraction of metals from their oxide ores. The common reducing agents used for reduction of metal oxides are: Carbon monoxide,  Carbon, Hydrogen.

During electrolysis, electrons are being added directly to the metal ions at the cathode (the negative electrode). The downside (particularly in the aluminum case) is the cost of the electricity. An advantage is that it can produce very pure metals.

Leaching of low grade copper ores is carried out with acid or bacteria, when copper goes into solution as $Cu^{2+} _{(aq) }+ H _{2(g)}\rightarrow Cu _{(s)}+2H^+ _{(aq)}$ 

By using depressants or adjusting proportion of oil to water, selective prevention of one sulphide ore from coming to the froth is possible.