Diatomaceous earth in solid–liquid separation: which role best describes its common industrial use?

Introduction:
Diatomaceous earth (DE), also called kieselguhr, consists of fossilized diatom skeletons rich in amorphous silica. Its micro-porous, lightweight structure makes it ideal in certain separation and purification operations.

Given Data / Assumptions:

• Focus is on solid–liquid filtration applications.
• Product purity and clarity are important.

Concept / Approach:
DE is dosed as a filter aid (precoat and/or body feed) to create a highly permeable cake that captures fine particles while maintaining reasonable flow rates. It is not a structural filter medium by itself (a septum is still required), nor is it typically used as a catalytic active phase (though it can be a support in special cases).

Step-by-Step Solution:
Recognize DE’s properties: high porosity, low density, irregular microstructure.Map properties to function: forming a porous filtration layer.Conclude that its common role is as a filter aid, not as an explosive, structural medium, or catalyst.

Verification / Alternative check:
Brewing, edible oil, pharmaceuticals, and pool filtration widely use DE-based precoat/body-feed processes to achieve clarity with minimal blinding.

Why Other Options Are Wrong:

• Explosive: DE is actually used as an absorbent to desensitize nitroglycerin (historically in dynamite), but by itself it is not the explosive.
• Permanent filter medium: DE requires a support such as a cloth or metal leaf.
• Catalyst: not active; at most a support.
• Abrasive only: while mildly abrasive, its core industrial role here is filtration aid.

Common Pitfalls:
Confusing DE’s role in dynamite as being the explosive; it merely acts as an absorbent/desensitizer.

Final Answer:
Filter aid to build a porous cake