What are the four different coagulation mechanisms? Explain the difference between EDL compression and charge reversal and how each affects coagulation.
Answers
Answer:
The four different coagulation mechanisms are as follows:-
Dual layer compression
Adsorption
Charge neutralisation
Sweep flocculation
Inter-particle bridging
Explanation:
Dual layer compression, adsorption and charge neutralisation, sweep flocculation, and inter-particle bridging are basically the four basic mechanisms of coagulation. The principal process for drinking water purification is sweep flocculation, which will be the subject of this session. Sweep flocculation occurs when iron or aluminium, usually in the form of ferric sulphate or aluminium sulphate, is introduced to the water and dissolves quickly. In the pH range of less than 7 or 8, iron and aluminium generate a variety of cationic species that assist destabilise natural particles by compressing and/or removing the negative surface charge. Many other salts and materials can add cations to water, but iron and aluminium are special in that they begin to precipitate in the form of iron hydroxide, FeOH(s), and aluminium hydroxide, AlOH, when added in high enough concentrations (s).