Dynamic Behavior of Surfactants in Solution

Abstract

Adsorption of various surfactants at the gas liquid interface is studied with equilibrium and dynamic surface tension measurements. The Wilhelmey plate method and maximum bubble pressure method are used for this study. Dynamic surface tension of solutions of different surfactants, sodium lauryl sulfate (SLS), polyoxyethylene glycol 4-tert-octyl phenyl ether (Triton X 100), poly-oxyethylene(20) cetyl ether (Brij 58), and tetraethylene glycol mono-n-dodecyl ether (Brij 30), is measured at different concentrations. Adsorption of different surfactants is compared on the basis of equilibrium and dynamic behavior. Effectiveness and efficiency of different surfactants is found from equilibrium surface tension measurement. A new parameter is defined to quantify the dynamic behavior of adsorption, which gives the concentration of surfactant needed to reduce surface tension to half of its maximum reduction within a defined time available for adsorption. The dynamics of surfactant solution is quantified by using this parameter.Keywords Dynamic surface tension, interface, micelle, maximum bubble pressure method INTRODUCTIONThe dynamics of interfacial layers, especially the characterization of interfacial dynamics, has attracted large interest among interfacial researchers. Dynamics becomes increasingly important as modern technologies require more and more quantitative relationships between dynamic interfacial properties and technological parameters. In most technological applications where the interface is created rapidly, such as foam formation, quickness of interfacial adsorption (dynamics) becomes important. [1,2] The importance of dynamic surfactant adsorption in colloid systems is well recognized. Surfactant adsorption is a timedependent process, markedly varying with the mechanism of dynamic adsorption. The extent of this process is generally quantified by the variation of surface tension. However, the change in surface tension as a function of time is, in most cases, substantially slower than the one expected from diffusion-controlled adsorption. For example, a 3 mol . m 23 solution of SLS attains a reduction of 20 mN/m in surface tension of an air-liquid interface in a period of 20 s. However, a higher concentration of SLS solution achieves the same drop in less than 1 s. Some surfactants, such as polyoxyethylene(20) cetyl ether (Brij 58), adsorb more, reducing surface tension of the interface

Preparation and characterization of perfluorocarbon microbubbles using Shirasu Porous Glass (SPG) membranes

“…Microbubble diameter was found to decrease when surfactant concentration increased, to achieve a minimum diameter for a concentration above the critical micelle concentration (CMC). Surfactants were therefore used at concentration above CMC to achieve maximum effect [39].…”

Effect of Additives on the Dynamic Behavior of Surfactants in Solution

“…The set up was arranged for dynamic surface tension measurement in the lab. [2] It measures the pressure difference between the inner and outer sides of the bubble. The pressure transducer was used to measure pressure difference.…”

“…In earlier work, quantitative dynamic concentration ratio was developed for comparing dynamic behavior of surfactant adsorption. [2] Several studies on single surfactant systems are reported in literature. [2 -6] It is well known that a foam booster lowers the surface tension of aqueous surfactant solutions and enhances molecular packing of surfactant at interface.…”

Synergism and Interfacial Property Study of Sodium Lauryl Ether Sulfate and Polysorbate 80 at the Air–Water Interface

“…Measurements were carried out at various surface ages ranging from 1 ms to 30 s by changing the bubble frequency. True surface age is considered to be the time elapsed between the bubble formation and bubble detachment (Kalekar and Bhagwat, 2006).…”