Coagulation of Colloidal Solutions

Introduction

Colloids are type particles that contain particles with a size more than atoms and molecules but are small enough to be visible by the naked eye. The studies regarding colloids began in the 19th century itself. In the 1820s Robert Brown discovered the random motion of colloidal particles present in a liquid with the help of a microscope. Which is then called Brownian motion. And it developed because of the bombardment of colloidal particles. Smoke, clouds, etc. are colloids. They are dispersions of solid particles with a size of 1 nm to 0.1micrometre range. And these particles have characteristic properties in which they do not sediment under normal conditions. But by the supply of additional forces, it may settle or sediment.

Define Coagulation in Chemistry?

The destabilization of non-settleable particles taking place is coagulation. It is a chemical process that involves the neutralisation of charged particles. The addition of coagulants results in the formation of aggregates of particles. Which then precipitates and settles out. Solid suspensions and colloidal particles can be settled in this way. This technique is often used in the water cleaning process in which wastewater that contains solid suspensions is converted into large agglomerates and then settled out as a precipitate. So, coagulation can be used for the removal of a solid suspension in water.

Coagulation Techniques

The process of coagulation is done with the help of some external conditions. Some of the techniques that can be adopted for coagulation are,

• By Boiling − The charger particles present in a colloid get bombarded faster when we boil, which will further result in the neutralization of these solid particles. So, then it is settled out as a precipitate.

• By Electrophoresis − The separation of particles based on charge is electrophoresis. The supply of electric current separates charged particles by moving them into opposite poles. Which then results in the precipitation or coagulation of colloidal particles. It is mainly done in biological fluids.

• Persistent dialysis − Coagulation takes place immediately through the process of persistent dialysis in which the electrolytes are removed completely and the solution will lose its stability.

• Mixing oppositely charged solution − The neutralization of charged particles present in a solution takes place when it mixes with an oppositely charged solution. Their charges cancel and form a precipitate.

• Addition of coagulant − The addition of coagulant results in the coagulation of particles. Some common coagulants are lime, alum, non-ionic polymers, etc.

Coagulation of Lyophilic Solutions

Lyophilic solutions are solvent-loving particles. There is a strong attraction between the dispersed phase and dispersion medium in the case of this colloid. Destabilization of lyophilic solution results in the coagulation of lyophilic solution. The stability of the lyophilic solution is due to the solvation and charge of colloidal particles. The solvation of lyophilic solution is the protective layer formed on the surface of colloidal particles. The removal of these factors will result in the destabilization of colloidal particles which are said to be coagulated. It can be removed by the addition of electrolytes or by the addition of some solvents such as acetone or alcohol.

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Coagulation process

Colloids are heterogeneous compounds in which solid particles are dispersed in a liquid medium. They are charged particles too. The process which involves coagulation can be explained by taking the example of drinking water treatment. The solid particles present in water can be removed by the process of sedimentation. But solid particles in the colloidal form cannot be separated by the sedimentation process. It is done by the coagulation process by the addition of a coagulant. Coagulants such as alum, lime, etc. will make the colloids into aggregates. This is because of the reason that coagulants will neutralize the negatively charged particles into neutral since coagulants are positively charged. Thus, the aggregate formed can be removed by the process of filtration. In this way, the process of coagulation is carried out.

Coagulation Tests

Coagulation tests are given to patients that have clotting disorders. It is also used for testing clotting in blood for patients taking medicines that may cause blood clots. These tests are also done before surgery. This test measures various proteins and how they function. Coagulation is present in patients who have liver disease, thrombophilia, haemophilia, etc. This test is conducted like a blood test. The side effects developed because of the coagulation test are very less.

Types of Coagulation Tests

There are different types of coagulation tests. Some of them are,

• Complete blood count (CBC) − In this test, the blood count is tested for detecting anaemia or to find whether a patient has a low platelet count.

• Factor V assay − The factor that is involved in clotting is factor V, it is measured during this test. And thereby testing the possibility of clotting.

• Fibrinogen level − By this test the level of fibrinogen is measured, it is a protein that helps in the blood clot. Fibrinogen is produced in the liver.

• Prothrombin time test − This test is used for measuring the time taken for blood to clot.

Conclusion

Colloids are solid suspensions that are very small in which it cannot be visible with the naked eyes. They are charged particles which cannot be separated by normal methods. Coagulation is a process which involves the settlement of solid particles to the corresponding precipitates. The precipitate is formed by the aggregation of solid particles by processes such as electrophoresis, the addition of coagulant, persistent dialysis, etc. The coagulation process is used in the purification of wastewater. There are different coagulation tests like a blood test which are done for the identification of chances of a blood clot in patients suffering from diseases that may affect the clotting process. This is also used for measuring platelet count and for identifying the clotting disorder.

FAQs

1. What is flocculation?

Flocculation is a process associated with coagulation. Coagulation helps to neutralise charges while flocculation helps to bind the particles together and thereby making them bigger. Then it can be easily separated.

2. What are lyophobic colloids?

Lyophobic colloids are opposite to lyophilic colloids which means that they are liquid hating. There is only a weak attractive force between colloids and solvent in this case.

3. What type of colloid is blood?

Blood is a type of colloid called sol. Sol is solid dispersed in a liquid or fluid. They are stable colloids, and the solid particles present in the blood will scatter the light too.

4. How do colloids acquire a charge?

Dissociation of surface molecules and adsorption in the colloidal particles is responsible for the charge of particles in the colloids.

5. Do colloids show the Tyndall effect?

Yes, colloidal particles show the Tyndall effect. Colloidal particles are small particles, so they cannot be seen with the help of naked eyes. But they show the property of the Tyndall effect, the scattering of light since they are big enough for this process.