As we have learnt, a mixture to be a combination of two or more substance which can be separated by physical method.
Therefore, separation technique are method employed to separate a mixture into its different constituents. There are different method used which depend on the nature of the mixture:
These are :
1) Filtration method
2) Evaporation method
3) Decantation method
4) Sublimation method
5) Centrifugation method
6) Distillation method
7) Fractional distillation method
8) Magnetic method
9) Crystallization method
10) Fractional crystallization method
11) Separating funnel method
1) Filtration method:
A porous material such as filter paper can be used to separate an insoluble dilute from the solution.
For example, A suspension of chalk (CaCO3) powder in water can be separated by passing the mixture through filter paper. During the process, water molecules pass through the filter paper and it is collected as a filtrate in the beaker leaving behind the chalk powder on the filter paper as a residue.
This method can be used in water purification plant etc.
2) Evaporation Method
It is used to recover a dilute from its solution by vaporizing. A salt solution can be separated by using evaporation method to dryness. During the process, a solution of salt is placed on a water bath to attain constant temperature. After a couple of minutes, the solvent turns to vapour and it is lost to the atmosphere. Leaving behind the salt in evaporation dish.
Note: This method can only be used for salt that can not be easily decomposed on heating. It is generally used in salt industry and many other industries.
3) Sublimation Method
This is a process whereby solid substances turn directly into vapour without passing through an intermediate liquid state.
Examples of this substances are: Ammonium chloride (NH4CL), Iodine (I), camphor (C10H6O) etc.
It is used to separate a mixture of sublime substance and non-substance substances. For Instance, a mixture of ammonium chloride (NH4CL) and sodium chloride can be separated by using sublimation method.
4) Centrifugation method
A centrifuge is a machine used to spin test tubes containing suspension at high speed. The spinning causes heavy particles in the suspension to settle at the bottom of the test tube while the clear upper layer is decanted.
This is widely used in quality and testing labs, it can used in hospitals to separate blood samples for its suspension.
5) Distillation method
Distillation is a technique used to separate liquid or gas mixtures into different fractions of desired purity by the application of removal of heat. It is used to recover a solvent componenet from a solution. This process can simply be experimented by placing a round bottom flask containing solution where it is heated to vapourize the solvent, the vapour is then passed through a liebig condenser, where it cools and condenses into liquid and this is later collected in a receiver. The solute and other impurities are left in the flask.
This method is applied in gin distillaries, water distillaries etc.
6) Fractional Distillation method
This method is used to separate a mixture of two miscible liquids with different boiling point.
Note: for fractional distillation to be effective, the differences in boiling point must be greater than 10 degrees celsius. Example of the Mixtures that can be separated by this method are: a mixture of ethanol and water, crude oil fractions etc .
During this process, a liquid with lower boiling point distilled over first leaving behind other liquid which are still within the limit of their boiling point.
7) Magnetic separation method
This method is used to separate magnetic substance from non-magnetic substance.
Magnetic substances are the substances that can be attracted by a magnet. Examples are : iron, nickel, steel etc.
Magnetic separation can be used for instance, to separate mixture of iron filling and sulphur. It is employed industrially in the process of iron ore.
8) Crystallization method
This is used to separate a solution of salt which decomposes easily on heating.
The salt crystal obtain in this form is pure and usually contains water of Crystallization. Examples are: CuSo4.5H2O , MgSo4. 7H2O , Na2CO3. 10H2O (sodium trioxocarbonate (iv) decahydrate).
It is used in the production of sugar and drugs.
9) Fractional crystallization
This is used to separate a mixture of two or more solid solute that are present in the same solution at roughly equal amount. The differences in the solubility of different solutes at a particular temperature is put into an advantage.
During the process, the crystals of solute come out at a particular temperature leaving behind the solute which are still within the limit of their solubility in the solution.
10) Separating funnel
This method is used to separate a mixture of two immiscible liquids (i.e. a polar and non-polar solvent ). An example is a mixture of water and kerosene. Water and kerosene is naturally an insoluble mixture, therefore forming two distinct layers. The lower denser layer is tapped off leaving behind a less dense layer when placed in the funnel.
11) Chromatography method
This method is used to separate coloured and colourless substances example, amino acid. The common method is ascending ascending paper chromatography. It comprises an absorbent medium which is a strip of paper. A solution of solute to be separated is spotted on one side of the paper. The paper is then dipped into a solvent in the spot.
During this process, the solute to be separated mix up with the solvent at a different distance on the paper.
However, the paper is removed when the solvent has moved up to 3 1/4 of the paper. The mobile phase is the solution and stationary phase is the paper, movement is due to capillary action. It is then dried and stained with chemicals in other to know the position of each solute on the paper.
Those solvents have different boiling points and would seperate accordingly. You would get a clear distinct seperate peaks for each solvent.
Mixtures that can be separated by Gas chromatography.
a)liquid mixture including of Benzene, Toluene, Xylene and Trimethylbenzene.
b) mixture of xylenes (o-xylene, m-xylene, and p-xylene)
C)mixture of trimethylbenzenes (hemellitene, pseudocumene, and mesitylene
There other forms of separation such electrophoresis (separates organic molecules based on the interactions with a gel under different travel), extraction, demister ( This method is used to remove liquid from gas streams), drying (used to remove liquid from solid), sieving , stripping, adsorption (the removal of atoms, ions or molecules of gas, liquid, or dissolved solids to a porous surface) etc. Add yours in the comments box below.