Surfactant Scavenging and Surface Deposition by Rising Bubbles.

Area of Science:

• Fluid dynamics
• Surface chemistry
• Colloid science

Background:

• Bubbles rising in liquids scavenge dissolved surfactants.
• Surfactant-coated bubbles exhibit altered surface mobility, affecting drag and rise speed.
• A cloud of rising bubbles significantly enriches the bulk surface with surfactants.

Purpose of the Study:

• To develop a model for surfactant uptake by bubbles and deposition on the bulk surface.
• To incorporate the effect of bubble-induced fluid mixing into the surfactant deposition model.
• To identify key factors influencing surfactant enrichment on the bulk surface.

Main Methods:

• Development of a mathematical model for surfactant-bubble interactions.
• Inclusion of bubble-induced fluid mixing as a critical parameter.
• Analysis of surfactant desorption and transport within the bulk fluid.

Main Results:

• Bubble surface immobilization due to surfactant adsorption affects bubble dynamics.
• Bubble clouds lead to substantial surfactant enrichment on the bulk surface.
• Fluid mixing induced by bubble motion is essential for accurate prediction of surface enrichment.

Conclusions:

• The model highlights the interplay between bubble scavenging, surface deposition, and fluid mixing.
• Mixing of desorbed surfactant into the bulk liquid is a critical factor in determining surface enrichment.
• Understanding these processes is vital for applications involving bubble-laden fluids.