Detachment of Oil Drops from Solid Surfaces in Surfactant Solutions:  Molecular Mechanisms at a Moving Contact Line

Abstract

Here, we present experimental data and a theoretical model for the dynamics of detachment of hexadecane drops from a solid substrate (glass plate) in aqueous solutions of anionic surfactant and salt, at various temperatures. The influence of the experimental conditions on the motion of the three-phase contact line is investigated. We found indications that water molecules can propagate by lateral diffusion in a thin layer on the surface of the solid plate. The driving force of the detachment process, viz., the imbalance of the interfacial tensions at the contact line, is engendered by the water penetration, while the line friction force compensates this imbalance and determines the stationary speed. Excellent agreement between theory and experiment is achieved. The present study specifies the parameters that can be used to quantitatively characterize the rate of drop detachment, determines the values of these parameters at various experimental conditions, and indicates tools for control of the investigated spontaneous process. † This paper is dedicated to Professor Darsh T. Wasan on the occasion of his 65th birthday.

Continuum models for the contact line problem

“…Discrepancies between these theoretical predictions and the experimental data have been found, particularly for systems containing a wide spectrum of contact line speed. [20][21][22][23][24][25][26] This suggests that neither model is complete in the description of the energy dissipation.…”

Surfactant effects on contact line alteration of a liquid drop in a capillary tube

“…Kralchevsky [1] stated that there were many experimental indications that surfactant solution may dissolve or diffuse into glass substrate. It was been detected in surface-force measurements.…”

Acidic surfactant solutions for tributylphosphate removal in nuclear fuel reprocessing plants: A formulation study

“…Several studies have examined oil detachment from solid surfaces in the past. The solid substrates considered included silica [10], gold [11], or glass [12,13]. For a stainless steel surface, the results are different whether the surfactant used is ionic or nonionic.…”