Deposition of spherical particles onto cylindrical solid surfaces. II. Experimental studies

Area of Science:

• Colloid and Surface Science
• Physical Chemistry
• Materials Science

Background:

• Understanding particle deposition is crucial for industrial processes and environmental science.
• The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory is a cornerstone for explaining colloidal interactions.
• Investigating non-DLVO forces, like hydrophobic interactions, is essential for a complete understanding of deposition phenomena.

Purpose of the Study:

• To experimentally investigate silicone oil drop deposition onto different solid surfaces in aqueous solutions.
• To compare experimental deposition rates with predictions from the classical DLVO theory.
• To identify and understand deviations from DLVO theory, particularly on hydrophobic surfaces.

Main Methods:

• Experimental deposition tests measuring the dimensionless mass transfer rate (Sherwood number).
• Systematic variation of aqueous solution pH and ionic strength.
• Utilizing different solid surfaces: bare glass (hydrophilic) and FC725 precoated (hydrophobic).
• Comparison of experimental data with numerical predictions based on DLVO theory.

Main Results:

• Sherwood numbers decreased monotonically with increasing pH for both experimental and numerical data.
• Ionic surfactants showed similar effects, while electrolytes had opposing effects on deposition rates across surfaces.
• DLVO theory accurately described silicone oil drop deposition on the hydrophilic glass surface.
• Experimental deposition rates on the hydrophobic FC725 surface significantly exceeded DLVO predictions.

Conclusions:

• Classical DLVO theory adequately explains silicone oil drop deposition on hydrophilic surfaces.
• Hydrophobic interactions, a non-DLVO attractive force, significantly influence deposition on hydrophobic surfaces.
• There is a need to incorporate hydrophobic interactions into existing theories like DLVO for comprehensive modeling.