Bi-modal hetero-aggregation rate response to particle dosage

Area of Science:

• Colloid and Surface Science
• Materials Science
• Physical Chemistry

Background:

• Flocculation is crucial in various industrial processes.
• Understanding particle interactions is key to controlling aggregation.
• Previous studies often reported unimodal flocculation rates.

Purpose of the Study:

• To investigate the flocculation rate of cationic polystyrene latex (PSL) by anionic PSL particles.
• To analyze aggregate growth as a function of particle size ratio and relative concentration.
• To explore the underlying mechanisms behind observed flocculation rate behaviors.

Main Methods:

• Low-angle static light scattering technique for measuring flocculation rates.
• Systematic variation of particle size ratios and relative concentrations.
• Analysis of aggregate growth kinetics.

Main Results:

• Observed two distinct peaks in flocculation rate versus particle dose, contrary to prior reports.
• Lower concentration peak linked to maximum collision efficiency in steady-state.
• Higher concentration peak associated with maximum collision rate constant in steady-state.

Conclusions:

• The bimodal flocculation rate arises from the interplay of collision efficiency and rate constants at different particle dosages.
• Complete adsorption of smaller particles onto larger ones is a prerequisite for steady-state.
• Aggregate growth rate is proportional to the product of collision rate constant and collision efficiency.