Opposite of dispersion: in colloid and particle technology, which process is the reverse of dispersing particles?

Introduction / Context:
Dispersion creates a stable distribution of fine particles within a fluid by overcoming attractive forces. The reverse idea is important for water treatment and solid–liquid separation, where aggregation improves settling and filtration.

Given Data / Assumptions:

• Fine particles suspended in a liquid.
• Comparing unit operations and physicochemical processes.

Concept / Approach:
Flocculation is the process where destabilized particles aggregate into larger, loosely bound flocs under gentle mixing, often after coagulation (charge neutralization). These aggregates settle or filter more readily than the original dispersed particles. Sedimentation and filtration are separation steps that exploit the aggregates but are not the reverse of dispersion per se.

Step-by-Step Solution:
Define dispersion: creating/maintaining small, separate particles.Reverse action: aggregation → flocculation.Therefore, choose “flocculation.”

Verification / Alternative check:
Jar tests in water treatment demonstrate that after coagulant addition and flocculant polymer dosing, dispersed colloids aggregate and become separable by sedimentation/filtration.

Why Other Options Are Wrong:
Sedimentation/filtration: separation techniques, not the physicochemical reversal of dispersion.“None” is incorrect because flocculation is the established term.

Common Pitfalls:
Confusing coagulation (destabilization) with flocculation (growth by gentle mixing); both are typically used together.

Final Answer:
flocculation