Use of Simplified Surface Tension Measurements To Determine Surface Excess: An Undergraduate Experiment

Abstract

The effect of surfactant adsorption on surface tension, as well as associated thermodynamic concepts are introduced in a laboratory experiment designed for undergraduate students. Using a reliable and accessible method, students measure the surface tension of aqueous solutions at different concentrations of sodium dodecyl sulfate. Students collect data to estimate the critical micelle concentration and quantitatively determine the maximum surface excess using the Gibbs adsorption equation. Students subsequently determine the surface area per molecule of this surfactant at the liquid–air interface and learn how to generate adsorption isotherm curves.

Solar-Enabled Water Remediation via Recyclable Carbon Dot/Hydrogel Composites

“…Figure B presents surface tension analysis of water containing 0.05 M sodium dodecyl sulfate (SDS) before and after illumination of the C-dot/hydrogel swelled in the contaminated water. Notably, while surface tension prior to remediation via the C-dot/hydrogel treatment was around 37 mN/m (accounting for the SDS surfactant film at the water surface), surface tension increased after illumination to approximately 72 mN/m, close to surface tension for pure drinkable water . We also evaluated remediation of water containing organic pollutants (Figure C).…”

“…Notably, while surface tension prior to remediation via the C-dot/hydrogel treatment was around 37 mN/m (accounting for the SDS surfactant film at the water surface), surface tension increased after illumination to approximately 72 mN/m, close to surface tension for pure drinkable water. 66 We also evaluated remediation of water containing organic pollutants (Figure 6C). Figure 6C shows the UV−vis absorbance spectra of water containing rhodamine 6G (R6G) (0.5 μM), which is among the most common organic pollutants in industrial wastewater.…”

CO2-responsive surfactants for switchable Pickering emulsions with a recyclable aqueous phase

“…2.4. The molecular cross-sectional area of NCOONa/ N + COONa at the air/water interface 59 According to the measured surface tension values of different concentrations of surfactant aqueous solutions, the γ s − lg c s curve can be obtained, and @γ s @ lg c s can be determined by software fitting, and then the surface activity can be used to calculate the interface excess concentration of the agent, Γ s (mol cm −2 ). The formula is as follows:…”

Interfacial and Aggregation Behaviour of Sodium Dodecyl Sulphate Induced by Ionic Liquids

“…Specific conductance κ of solution was measured by a direct reading conductivity meter, Cyber Scan CON510 Eutech Instruments, Singapore with an accuracy of 0.1 μScm 1 . Conductance κ vs. S plots, at a particular break point indicates CMC 48 .…”