Enrichment of ore

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Step 1. Enrichment of ore:

First step in the metellurgy is, thus, to remove these unwanted impurities from ore such that concentration of metal in the ore increases, that is ore enriched in the metal. 

Some methods are used for concentration of the ore:
1. Hydraulic Washing:   This method is used for the enrichment of oxide ores of heavy metals like lead, tin, iron etc. 
In this method, the ore is crushed & finally powdered. The powdered ore is washed with a stream of water. The gangue particles, being lighter, are washed away with water, while heavy ore particles are left behind.

2. Froth Floatation process:   This method is used for the enrichment of sulphide ores, especially those of copper, zinc & lead. The method is based on the principle of difference in different wetting properties of ore & gangue.


3. Chemical Seperation:   This method is also called the leaching. This method bases on the difference in the chemical reactivity of the ore & the gangue towards a particular reagent. In this method, the powdered ore is treated with certain chemical reagent in which the ore is used for concentration of bauxite ore & silver ore.

4. Electromagnetic Seperation: This method is used for enrichment of the ore when the ore is magnetic in nature & the impurities are non-magnetic or vice versa. It is done by means of magnetic seperator.


Step 2. Extraction of metals from the concentrated ore:

• Metals of low reactivity
• Metals of medium reactivity
• Metals of high reactivity

1. Extraction of metals  low in the  Activity series: since, copper, mercury etc. have low reactivity, their oxides can be reduced to metals by the action of heat alone. As their most common ores are sulphide ores, thus, in order to obtain the metal from these ores, the only step is needed is roasting, that is heating the ore is strongly in the presence of excess of air.

2. Extraction of metals medium in the Activity series:  
The metals in the middle of the activity series such as iron, zinc, lead, copper etc. are moderately reactive. These metals are found in the nature in the form of their oxides, sulphide or carbonate ores
• conversion of the carbonate or sulphide ore into metal oxides: It is done by two methods:
1. Roasting
2. Calcination

• Reduction of the metal oxides to metal:  since these metals are moderately reactive, their oxides cannot be reduced by heating alone. Thus, their oxides are reduced to metals by using a suitable reducing agent such as carbon or some highly reactive metals like sodium, aluminium, etc. 
1. Reduction by heating along with carbon: we know that carbon is in the form of coke or coal the cheapest reducing agent. 
2. Reduction by heating along with aluminium:
Oxides of some metals such as manganese oxide, chromium oxide etc. cannot br satisfactorily reduced by heating with aluminium powder.

The reduction of metal oxides to metal using aluminium as the reducing agent is called Aluminothermy.

3. Extraction of metals towards the top of the Activity series:
The highly reactive metals such as potassium, sodium, calcium, magnesium, aluminium,etc. Which lie at the top of the activity series of metals, cannot be obtained by reduction of their oxides by heating with carbon or aluminium, because these highly reactive metals have greater affinity for oxygen as compared to carbon or aluminium.

Step 3. Refining of impure metals:

Metals obtained by any of the reduction methods still contains a number of impurities. Hence, the metal obtained is not pure. It is known as crude metal.
The process of purifying the impure metals is known as refining of metal 
The method used for refining depends on the nature of the metal & the nature of the impurities present.
Steps involved in this process are as:
• The impure metal, taken in the form of a thick block, is made the anode in the electrolytic task by connecting it to the positive terminal of the battery.
• A thin plate of pure metal is made the cathode by connecting it to the negative terminal of battery.
• A suitable water- soluble salt of the metal to be refined is taken as electrolyte. It's solution in water is taken in the electrolytic tank.








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