Metals and Non-metals-Metallurgy.
- Brief description of processes involved in the extraction of less reactive, moderately reactive and highly reactive metals from their ores.
· Metals occur in nature in free as well as in the combined states.
· Those metals which are least reactive and have little or no affinity for oxygen, moisture and other chemical reagents occur in free, metallic or native state, i.e. in uncombined state.
Example: silver, gold, platinum.
· Most of the metals are reactive and hence are found in combined state, i.e. as compounds.
Mineral and Ore
· The natural substances in which metals or their compounds occur in the earth are called minerals.
· The minerals have a definite composition.
· It may be single compound or complex mixture.
· The minerals from which the metals can be extracted easily and economically are known as ores.
· All ores are minerals, but all minerals are not ore
· Metals which occur in native state are –
Silver (Ag), Gold(Au),Platinum( Pt), Mercury( Hg).
· These are usually found associated with rock or alluvial materials like clay, sand etc.
Lumps of pure metals are called nuggets.
The various processes involved in the extraction of metals from their ores followed by refining of metal are known as metallurgy.
· The processes used for extraction varies for different metals.
· The three major steps involved in the extraction of metal from its ore are-
(1) Concentration of ore (or Enrichment of ore)
(2) Conversion of concentrated ore into metal
(3) Refining (purification) of impure metal
Concentration of Ore (or Enrichment of ore):
· Concentration of the ore is also known as 'dressing' or 'enrichment' of ore.
· Ore usually contains soil, sand, and rocky material as impurities. These impurities are called gangue or matrix.
· The substance added to the ore to remove insoluble impurities as fusible material is called flux.
· The fusible material formed during reaction is called slag.
· The processes used for removing gangue from the ore are based on the differences between the physical or chemical properties of the gangue and the ore.
At first the ore is crushed to powder.
The pulverized ore is separated by physical processes like-