The Oscillatory Spinning Drop Technique. An Innovative Method to Measure Dilational Interfacial Rheological Properties of Brine-Crude Oil Systems in the Presence of Asphaltenes

Quantifying the interfacial tension of adsorbed droplets on electrified interfaces

HYPOTHESIS

This paper develops a new measurement method to answer the question: How does one measure the interfacial tension of adsorbed droplets?

EXPERIMENTS

This measurement is based on the placement of a bubble at a water|organic interface. To prove the concept, a bubble was formed by pipetting gas below the water|1,2-dichloroethane interface. Our values agree well with previous reports. We then extended the measurement modality to a more difficult system: quantifying interfacial tension of 1,2-dichloroethane droplets adsorbed onto conductors. Carbon dioxide was generated in the aqueous phase from the electro-oxidation of oxalate. Given carbon dioxide's solubility in 1,2-dichloroethane, it partitions, a bubble nucleates, and the bubble can be seen by microscopy when driving the simultaneous oxidation of tris(bipyridine)ruthenium (II), a molecule that will interact with CO2.-. and provide light through electrochemiluminescence. We can quantify the interfacial tension of adsorbed droplets, a measurement very difficult performed with more usual techniques, by tracking the growth of the bubble and quantifying the bubble size at the time the bubble breaks through the aqueous|1,2-dichloroethane interface.

FINDINGS

We found that the interfacial tension of nanoliter 1,2-dichloroethane droplets adsorbed to an electrified interface in water, which was previously immeasurable with current techniques, was one order of magnitude less than the bulk system.