Atomic Force Microscopy Study of Non-DLVO Interactions between Drops and Bubbles

Abstract

The heterointeraction between liquid drops and air bubbles dispersed in another immiscible liquid is studied with the application of the atomic force microscopy (AFM) probe techniques. The tetradecane drops and air bubbles readily coalescence to form a lens-like structure in 100 mM sodium chloride aqueous solution, demonstrating strong hydrophobic (HB) attraction. The interaction range and strength of this hydrophobic attraction between oil drops and air bubbles is investigated by fine control of electrical double layer thicknesses related to specific electrolyte concentrations, and a midrange term in combination with a short-range term is found to present a proper characterization of this hydrophobic attraction. A further step is taken by introducing a triblock copolymer (Pluronic F68) into the aqueous solution, with results indicating that a relatively long-range steric hindrance (SH) furnished by a polymer “brush” surmounts the hydrophobic attraction. Finally, the interaction between a water drop and an air bubble in tetradecane is also measured as a comparison. The repelling action between a hydrophobic body (air bubble) and water drop indicates a strong repulsion. The present results show an interesting understanding of hydrophobic interactions between drops and bubbles, which is of potential application in controlling dispersion stability.

Microscale Reservoir Wettability Evaluation Based on Oil–Rock Nanomechanics

“…The origin of the hydrophobic interaction was mainly caused by migration and the uneven distribution of water molecules on the hydrophobic surface. The hydrophobic interaction was the dominant factor between alkane and hydrophobic surfaces. − …”

Anti-Oil-Adhesion Property of Superhydrophilic/Underwater Superoleophobic Phytic Acid-FeIII Complex Coatings

“…The VDW interaction between the oil droplets and the surface in the aqueous solution is ( A H = 6.09 × 10 –21 J), which is the critical factor in leading the oil droplets to adhere to solid surfaces . Because of the negative surface potential of oil droplets, silica, and phytic acid-Fe III complexes in aqueous solution, their EDL interactions are repulsive. ,− As shown in Figure B, the EDL repulsion dominates the DLVO interaction in the 1 mM NaCl solution, which allows the stability between the oil droplets and the surfaces in aqueous solutions. Under high salinity conditions, the EDL repulsion is significantly suppressed, while the VDW attraction can be considered to be unchanged .…”

“…In the process of a high-speed collision, the aqueous solution in the liquid film between the oil droplet and the surface was challenging to drain promptly. This will cause significant hydrodynamic repulsion and increase the thickness of the liquid film, causing an insufficient contact between the droplet and the surface. , …”

“…This will cause significant hydrodynamic repulsion and increase the thickness of the liquid film, causing an insufficient contact between the droplet and the surface. 70,78 Underwater Oil Injection and Wall Sticking Tests. For clarity of observation, an underwater oil injection test was conducted on PAFC-modified glass substrates using crude oil A to verify the antifouling property of PAFC coatings.…”

Effect of Oil-Soluble/Water-Soluble Surfactants on the Stability of Water-in-Oil Systems, an Atomic Force Microscopy Study

“…This steric hindrance is particularly prevalent in systems containing macromolecular surfactants, such as polymers . Our previous research , described the steric hindrance of a triblock copolymer, F68, and its influence on the stability of aqueous continuous emulsions and foams.…”