Dynamic salinity‐induced phase‐inversion conductivity measurements used to characterize alcohol ethoxylate based surfactant/oil/water systems

Abstract

Dynamic conductivity measurements proved to be an effective and rapid method to determine the optimal experimental conditions for a salinity-induced phase-inversion from surfactant/oil/water (SOW) systems consisting of nonionic surfactants, more specifically alcohol ethoxylates. This emerging methodology can be used as a rapid screening tool to determine the impact of alcohol ethoxylate surfactants in a SOW solution and was demonstrated to be not only repeatable, but highly comparable to the traditional static method, in which the solutions are added to flat bottom tubes and allowed to equilibrate at a given temperature for extended time periods. Given a set of experimental conditions (oil-type, temperature, etc.), these dynamic salinity-induced phase-inversion (Dy-SPI) conductivity measurements can be used to determine the optimal salinity (S*) for a given surfactant at a set concentration, as well as its characteristic curvature via a series of experiments with varying oil types. Additionally, Dy-SPI was used to confirm the previously observed inverse relationship between the concentration of an alcohol ethoxylate and S* under a given set of conditions. What makes this method so unique is the amount of time (30 min to 1 h) and the simplicity of the equipment needed for these Dy-SPI conductivity measurements, allowing for a rapid screening tool for these SOW parameters. K E Y W O R D S analytical chemistry and techniques, interfacial science, non-ionic surfactants, surface activity NOMENCLATURE SOW HIGH surfactant/oil/water solution with high salinity in the aqueous phase SOW LOW surfactant/oil/water solution with low salinity in the aqueous phase V Aq,0 initial volume of the aqueous phase f w volume fraction of the aqueous phase Q flow rate of the SOW LOW (in ml/sec) S σ = 5%salinity at which the conductivity has reached 5% of its normalized value S σ = 95% salinity at which the conductivity has reached 95% of its normalized value T avg. σ = 5% to 95% average temperature when the conductivity of the solution is between 5% and 95% of its normalized value