Question

Write principle, advantages and disadvantages of electro dialysis for demineralization of water.

Answer 1

Principle-

It is a process used for the separation of oppositely charged molecules of similar size. This is done by separating the membranes of molecules using potential difference as the driving force for the movement of these ions in the solution.

Advantages

• The separation is done without a change in phase, hence the power consumption is low.
• After this only chlorination is required for filtration in case of brackish water.
• Osmotic pressure does not affect this process hence pressure can be varied accordingly.
• It can be easily used for separating non-ionised particles from ionised particles.

Disadvantages-

• Organic materials, colloids and SiO2 cannot be removed using this process.
• ED stakes fouling hence pretreatment is required for the same.
• Proper monitoring and control is required which can be a complex thing to handle.
• Materials for making membranes and stacks must be chosen properly so as to ensure compatibility in the process.