Filter aids in cake filtration Which material is most commonly used as a filter aid to form porous, permeable precoat layers and prevent blinding?

Introduction / Context:
Filter aids are used to increase permeability, reduce cake resistance, and protect the septum in pressure and vacuum filtration. Selecting the right aid improves throughput and clarifies challenging slurries.

Given Data / Assumptions:

• Objective: build a porous precoat or body-feed network.
• Slurry tends to blind or forms compressible cakes.
• Compatibility with process fluid is assumed.

Concept / Approach:
Diatomaceous earth (kieselguhr) consists of fossilized diatom skeletons with high porosity and intricate microstructure. This produces a rigid, permeable lattice that captures fines without excessive pressure drop. It is therefore the industry standard for clarification and polishing steps.

Step-by-Step Solution:

Verification / Alternative check:
Beer, wine, sweetener, and pharmaceutical filtrations commonly specify diatomaceous earth for precoating or body feed, confirming broad acceptance.

Why Other Options Are Wrong:

• Fuller’s earth and clays are sorbents for decolorization, not optimized as filter aids for permeability.
• Vermiculite can be used in specialty cases but is not the predominant industrial choice.

Common Pitfalls:
Poor precoat application leads to channeling; always establish a uniform layer before introducing the slurry. Ensure safe handling as dust can be hazardous.

Final Answer:
Diatomaceous earth