Identify the most commonly used filter aid added to form permeable cakes and prevent blinding in filtration.

Introduction / Context:
Filter aids are precoat or body-feed materials that create a porous, permeable skeleton on the medium, capturing fine solids while maintaining transmissivity. Choosing the right aid avoids excessive pressure rise and short cycles.

Given Data / Assumptions:

• General-purpose clarification in process industries.
• Fine particulates liable to blind the medium.

Concept / Approach:
Diatomaceous earth (kieselguhr) consists of frustules of diatoms with intricate, high-void structures, providing excellent permeability at moderate strength—hence its widespread use. Perlite and cellulose are also used, and calcium silicate appears in specialty applications. Sodium carbonate is not a filter aid; silica gel is a desiccant, not typically used as a structural filter aid in pressure filters.

Step-by-Step Solution:
Match requirement (porous, permeable, inert) with candidate materials.Select diatomaceous earth as the standard choice.

Verification / Alternative check:
Precoat filtration in beverage, pharma, and chemical sectors commonly uses kieselguhr.

Why Other Options Are Wrong:
Calcium silicate: used but less common than DE.Sodium carbonate: reagent, not a filter aid.Silica gel: moisture adsorbent, not a structural cake aid.

Common Pitfalls:
Confusing desiccants or reagents with structural filter aids.

Final Answer:
Diatomaceous earth (kieselguhr)