Question

Filter aids are added to the slurry prior to filtration in order to form ________

• A. Compact cakes of low porosity
• B. Cakes of increased porosity
• C. Crystalline cakes
• D. Baked cake

Hint:

Filter aids help improve filtration by forming porous filter cakes, reducing resistance and speeding up the process.

Answer 1

The Correct Option is B

During filtration, solids are separated from liquids by forming a filter cake on the filter medium. However, this cake can become densely packed and cause high resistance to flow.
To avoid this issue, filter aids are added to the slurry. These are finely divided, porous materials like diatomaceous earth, perlite, or cellulose. Their role is to improve the filtration process by creating a filter cake with higher porosity and lower resistance to fluid flow.
By incorporating these filter aids, the resulting cake is more permeable and allows liquid to pass through more easily, thus increasing the filtration rate and efficiency.
Let’s examine the options:
- (1) Compact cakes of low porosity: This would hinder filtration, not enhance it.
- (3) Crystalline cakes: Crystallinity is not relevant to the function of filter aids.
- (4) Baked cake: Irrelevant and nonscientific in the context of filtration.
Hence, the correct answer is that filter aids form cakes of increased porosity.