Effect of Surfactants on the Deformation and Detachment of Oil Droplets in a Model Laminar Flow Cell

Abstract

IFP Energies nouvelles International Conference Rencontres Scientifiques d'IFP Energies nouvellesRe´sume´-É tude de l'effet de tensioactifs sur la de´formation et le de´tachement de gouttes d'huiles mode`les a`l'aide d'une cellule a`flux laminaire -Les tensioactifs « verts » a`teˆte polaire de´rive´e de sucre (glucose, pentose) sont de plus en plus pre´sents dans les formulations de´tergentes en raison des re´glementations en vigueur et des demandes des consommateurs. Dans le but d'e´tudier le pouvoir de´tergent de ces nouvelles mole´cules, le comportement de gouttes d'huiles mode`les soumises a`un flux de solution de´tergente de concentration variable, a e´te´e´tudie´a`l'aide d'une cellule a`flux laminaire et corre´le´aux proprie´te´s physicochimiques des syste`mes aux interfaces liquide/liquide et solide/liquide/liquide. Trois comportements principaux ont e´te´observe´s à partir d'une valeur critique du de´bit de de´tergent : un e´talement, un fractionnement de la goutte ou bien son de´tachement spontane´de la surface. L'analyse des re´sultats a montre´une corre´lation entre le comportement de la goutte et l'e´quilibre des forces s'exerc¸ant sur la goutte dans sa position initiale (avant l'application du flux), en particulier en conside´rant la force de gravite´, qui tend a`de´tacher la goutte de la surface, et la force capillaire, qui tend a`maintenir sa forme sphe´rique. Un diagramme d'e´tat a pu eˆtre e´tabli, permettant de pre´dire le comportement de la goutte, en fonction du nombre de Bond (rapport des forces de gravite´sur les forces capillaires) et du cosinus de l'angle de contact de la goutte dans sa position initiale. Les re´sultats obtenus ont permis de comparer les performances de diffe´rents tensioactifs en termes de de´graissage et d'illustrer le potentiel des AlkylPolyPentosides (APP) pour cette application.Abstract -Effect of Surfactants on the Deformation and Detachment of Oil Droplets in a Model Laminar Flow Cell -Sugar-based surfactants are increasingly present in the development of ecofriendly detergents due to current regulations and consumer demand. In order to assess the degreasing performance of these new surfactants, the behavior of model oil droplets subjected to the action of a flow of surfactant solutions of different concentrations was studied in a laminar flow cell and related to the physico-chemical properties measured at the liquid/liquid (interfacial tension) and solid/liquid/liquid interfaces (contact angle). With the surfactant solutions and the model oils employed in this study, three main behaviors were observed when a critical flow rate was reached: elongation, fragmentation or spontaneous detachment of the droplet. The analysis of the results leads to a correlation between the droplet behavior and the balance of the forces applied on the droplet in

Critical conditions for the buoyancy-driven detachment of a wall-bound pendant drop

“…13,15,17 Although experiments and simulations on the buoyancy-driven detachment of liquid emulsion droplets from solid substrates have been carried out in the past, none of those previous studies has addressed the critical Bond number as a function of the relevant nondimensional parameters systematically. In fact, in addition to the works cited above, a number of theoretical, numerical, and experimental investigations have been focused on the influence of a shear flow on the conditions for drop removal from solid surfaces, [22][23][24][25][26][27][28] neglecting the more fundamental case of a pendant drop acted upon by surface tension and wall-normal buoyancy forces alone. At least in part, one reason for this neglect can be ascribed to the fact that the classical fluid dynamic formulation of incompressible two-phase flow with a dynamic contact line encounters a stress singularity which can only be resolved by replacing the no-slip boundary condition for the Navier-Stokes equation with a slip condition based on a tunable length.…”

Solid–Liquid–Liquid Wettability of Surfactant–Oil–Water Systems and Its Prediction around the Phase Inversion Point

“…Surfactant–oil–water (SOW) systems are important in numerous applications such as transport of emulsions through porous media in enhanced oil recovery (EOR), detergency of fabrics, and cleaning of hard surfaces. − The wetting behavior of an oil drop on a surface immersed in an aqueous phase, or solid–liquid–liquid (SLL) wettability, is an important parameter in the performance of EOR and cleaning processes. There is a general agreement that low interfacial tension (IFT or γ o–aq ) and water wet conditionscontact angle through the oil phase (θ O ) above 90°are desired to promote drop detachment from the surface and reduce the capillary forces trapping the oil in porous media. − SLL wettability depends on multiple factors, such as the nature and topography of the surface, chemistries of the aqueous and organic phases, temperature, and pressure. − In addition, the oil drop detachment process also depends on inertial, shear, and buoyancy forces. ,− Three main drop detachment mechanisms have been identified: roll-up, where the contact angle (θ O ) increases up to 180°, completely removing the drop from the surface; emulsification, in which the low IFT promotes partial detachment by necking and drawing; and solubilization, where the oil is incorporated into surfactant micelles. − …”