Applications of Colloids

Colloids have very important application in our daily life starting from food products to the medicines to industries like rubber. Some of the applications of colloids are mentioned below. 

• Food and medicines:  Colloids have great application in food industries and food stuffs. Many of the food materials which we eat are of colloidal nature. Milk and also many milk products like chees, cream butter etc. are colloids.
  In more accurate way, milk is an emulsion (liquid in liquid colloidal system). In milk, butter and fat are dispersed in water. Bread is colloidal system in which air is dispersed in baked dough.
  Colloids also have applications in the form of medicines. Colloidal medicines are competitively more effective as they are easily absorbed by the body. That is way many medicines are emulsion.
  Some major antibiotics like penicillin and streptomycin are injected in the body in the form of colloidal sol so that they would be absorbed by the body easily. 

• Water Purification: We know that one of the very popular methods used for water purification is the addition of electrolytes like potash alum. Addition of these electrolytes is based on the fact because the impure water in usually a colloidal system. It usually contains dispersed colloidal particles which cannot be removed by filtration. Addition of these electrolytes results in coagulation of the impurity which can be separated by filtration then. 

• Sewage disposal: As discussed above the sewage water contains impurities like mud and dirt of colloidal size which are dispersed in the water. Just like any other colloidal system, the colloidal particles (impurities) of sewage are also charged particles.These charged particles of impurities present in sewage may be removed by electrophoresis.
  For this purpose the sewage water is passed through a tunnel which is fitted with metallic electrodes and is maintained at a high potential difference.
  The charged particles of impurity present in the sewage water migrate to the oppositely charged electrodes which results in their coagulation.          

• Smoke precipitation:  Smoke is also a colloidal system which mainly consists of charged particles of carbon depressed in air.
  Smoke is a big problem for environment as it the major source for air pollution.
  Removal of the dispersed colloidal particles from the air will solve the problem. For this again the process of electrophoresis is used.
  This is done in Cottrell precipitator. Smoke is passed through a chamber which contains a number of metal plates attached to a metal wire connected to high potential source.
  The electrically charged colloidal particles of carbon present in air  get discharged when come in contact with the oppositely charged plates and fall down to the bottom. The clean hot air leaves the precipitator from an exit near the top.
  

• Artificial rain: Clouds are also colloidal system. In clouds, water vapors are present in mixture with the dust particles. The water molecules present in cloud have electric charge on them and are of colloidal size. So, if the charged on the molecules is neutralized somehow, they will start raining. Sometimes it is done by spraying some electrolytes over the clouds and the rain resulted from this is called artificial rain. 

• Rubber industry:You must know that the rubber is synthesized from the latex obtained from the rubber trees. This latex is an emulsion in which negatively charged particles of rubber are dispersed in water.
  For obtaining rubber, this latex is boiled because of which the rubber particles get coagulated. This coagulated mass is then vulcanized to solidify as natural rubber.

• Leather tanning: Tanning is the process of treating the skins of animals to obtain the leather. Skin of animals is also a colloidal system in which the colloidal particles are positively charged. During the process, the charged particles of skin are coagulated using negatively charged material like tannin and some compounds of aluminum and chromium..

  

• Cleansing action of soaps:  As we have discussed earlier also, the soap solution is a colloidal system and it removes the oil and dirt by forming water soluble emulsions. 

• Smoke screen: Smoke screens are used to hide something by a layer of smoke. In generally it is used to hide the movement of troops. The smoke screens are also colloidal system in which the particles of titanium oxide are dispersed in air.

• Formation of delta:  Extensive deposits of sand and clay formed at the mouth of any river in sea at the site where the river falls into sea are called delta.
  The formation of delta is a very interesting natural phenomenon in which negatively charged colloidal particles of river are neutralized and thus coagulated by the positively ions of the salt present in sea.
  As it is very expected, the river water contains colloidal particles of sand and clay which are negatively charge.
  On the other hand the salty sea water contains a number of positive ions.
  When the water of river comes in contact with water of sea, the negative charge present on colloidal clay particles present in river water get neutralized by the positively charged ions present in sea because of which they get coagulated and deposit at the site. 

   

• Blue colour of the sky:  The blue colour of sly is due to scattering of the blue colour of sun light by the colloidal particles of dust dispersed in the air present in atmosphere. (Tyndall effect). 

• Preparation of Nano-materials:  Nano-materials which are used as catalyst are prepared by using reverse micelles. 

• Metallurgical operations: The froth floatation process used for metallurgy of sulphide ores involves the treatment of the ore in emulsion of pine oil.?

Question 1: Which of the following substances are used for removal of dispersed colloidal particles in water ?

a.  Alum

b.  Rock salt

c.  Copper sulphate

d. Ammonium carbonate

Question 2: Cottrell precipitator is used for 

a. water treatment

b. smoke screen

c. smoke precipitation

d. dispersion of light

Question 3: Smoke screens are the colloidal dispersions of very fine particles of.. 

a. titanium oxide in air

b. carbon  di oxide in air

c. water droplets in air

d. sulphur in air

Question 4: Which of the following alternatives is not a colloid?

a. penicillin

b. streptomycin

c. cod-liver oil

d. paracetamol

Related Resources

• You can also refer to past year papers of IIT JEE  

• Click here access the syllabus of chemistry for  IIT JEE

• Click here for classification of colloids