The Removal of the Impurities from extracted metals is called Refining of metals or Purification of metals. Generally, any of the methods can be used in purifying of the Crude metals.
What are the various methods of refining of metals
(a) Electro-refining method
(b) Distillation method
(c) Liquation method
(d) poling method
Lets understand it in details
Electro-refining Method
It is employed for the refining of metals like metals like gold, silver, copper. Etc. In the Method the impure metal is made as node. While thin sheet of pure metal is made cathode. A Suitable salt of the metal is taken as electrolyte. When electric current is passed through the solution.
The pure metal slowly passes from the node to cathode through the electrolyte and gets deposited there. The impurities which are associated with metal either pass down near the anode and is known as anode mud or are left at the node as another Skelton.
Distillations method
Refining of the metal is done by distillation when the metal is volatile in nature and impurities are nonvolatile. Metal like zinc, mercury., Tin, Arsenic are purified by this method.
Liquation method
It is Applicable for the separation of easily fusible metal like tin, lead, Mercury etc. This method can also be employed hen the difference between the melting Points of the metals and impurities is quite wide.
The crude metal is Placed on the sloping hearth of the furnace and is furnace and is collected at the receiver at the base of the furnace. Metal can be drawn through the tap hole.
Poling Method
It is an old process of refining metal in which the molten metal is stirred with the help of green wood poles or sticks of wood. Wood oxidases the impurities which come out to the surface.
These impurities can be easily removed. Generally, copper, zinc, Ag are refined by this method.
What is refining of aluminium by hoope’s process
Refining of aluminums Is carried out by hoope’s process as explained below: –
Impure aluminums is purified in the hoop’s cell, which is made of steel and lined inside with a lining a of carbon. The carbon lining acts as anode. The electrolyte in cell consists of three different layers one over the other as shown in fig.
Layers at the button consists of moltan impure aluminum. Above this layer floats the electrolyte consisting of a mixture of fluorides of Aluminum, Sodium and barium. The uppermost layer consists of pure aluminum. Graphite electrodes, suspended in the bath are used as cathodes.
On passing the electric current aluminum from the middle layer is transferred into upper layer and an equivalent amount of aluminums from the bottom layers gets transferred in to the middle layers. In this way there is a continuous transference of a Aluminum from the bottom to top from where it is drawn off from time to time. aluminums obtained from this process is 99.99% pure.
What is the process of Extrction of cast iron or pig iron from its Hematite ores
Here are the Following steps That are involved in the extraction of cast iron. which we will describe in detail Below:-
(a) Concenttration of ore
(b) Calcination
(c) Smelting
Lets Under all of these3 Process of Extraction of cast iron or pig iron from its hematite ores
Concentration of ore
The ore is crushed and broken into small piceces. This ore is then cancentreted by gravity separation method in which it is placed in a big shallow tank and stream of water flows through it. Washing out all the impurities like clay and sand. This concentrated ore is then washed and dried.
Calcination
In this Process ore is heated in specially designed kiln equipped with shallow hearth. this ore is heated where carbonates decompose into CO2 and ocxided ore i.e ferric oxide insteaad of ferrous oxide is obtained which prevent it from being removaed away in the form of FeSio3. During this process volatile impurities like water, CO2, As, SO2 are removed.
Smelting
The calcined ore is then mixed with de-sulpherised coke an lime in the ratio of 8.4 : 1 and tfed into blast furanc through double cap and cone feeder.
The blast furnance is made of steel plates lined inside with silica or limeaccording to the impurities present in the ore (i.e. basic or acidic nature). The Furnance is also provided with an arrangement for blowing air near the base. slag hole, a tapping hole for removing the molten metal and an exit for water gases near the top.
The blast furnance is provided with the double cup and cone arrengement at top for feeding the charge. Hot air is blasted through tuyers near the bottom of the furnance. cowper’s regenaration hot blast stoves are used for removing the heat of the flue gases.
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