Question

Describe each of the following terms that relate to the coagulation process (a) Electrostatic Repulsion (b) Van der Waals attraction (c) Energy Barrier (d) Charge Neutralization (e) Colloid Entrapment/Sweep Coagulation

Answer 1

Answer.

(a). Electrostatic repulsion - Electrostatic repulsion develops as a result of interaction among same charges. In colloids, later of charges overlap each other and come in relation to one another, due to which a repulsion is produced based on the nature of the charges which is the electrostatic repulsion between them.

(b). Van der waals attraction - Each molecule possesses a certain molecular structure in space. Vanderwaal forces are intermolecular attractions between molecules of the same substance developed due to momentarily produced charges or polarity among the molecules.

However there are two types of vanderwaal attractions which could exist between molecules. They are weak London dispersion forces and strong dipole dipole interactions.

(c). Energy barrier - Energy barrier is theoretically the difference between energies of products and reactants during a chemical conversion. All the reactant molecules must possess the energy equal to this energy barrier in order to get converted to product.

(d). Charge neutralisation - When opposite charges combine and neutralise one another, it is called charge neutralisation.

In coagulation, if a negatively charged Sol is added to a positively charged Sol or vice versa, the charges combine and neutralise one another and coagulates.

(e). Colloid entrapment/Sweep coagulation - It can be defined as trapping colloids by adding other coagulants to the sol. When the colloid substances need to be removed from a solution, large amounts of coagulants like aluminium and iron are added to the solution. As a result, they form precipitates with the colloid and the colloids are swept away. That's why this is known as Sweep coagulation.