Coalescence Behavior of Stable Pendent Drop Pairs Held at Different Electric Potentials

Abstract

In this work we studied electrocoalescence behavior of stable pendent drop pairs and compared the results to the clean drops, where the interface is void of surface-active compounds. The drop phase is brine and the drop-oil interface is stabilized by aging into asphaltene and demulsier solutions. The experiments involving asphalteneladen drops required the bulk phase to be clear for visualization of the drops, which is realized by a procedure to replace the asphaltene-containing dark bulk phase by a pure solvent mixture. The narrowly spaced pendent drops, maintained at dierent electric potentials, acquire net surface charge of opposite polarity which leads to the Coulombic attraction in the drop-pair. After the application of voltage, a drop pair observed to be remained at a standstill, attracted or coalesced depending on the inter-drop separation, drop size, and potential dierence. We systematically investi-

Experimental Evidence of Enhanced Adsorption Dynamics at Liquid–Liquid Interfaces under an Electric Field

“…The asphaltene adsorption in the absence of external forces is irreversible. , Similarly, the asphaltene molecules adsorbed while the electric field is on do not desorb if the field is turned off. As can be seen in Figure , for both asphaltene subfractions, the interfacial tension of the water–oil interface decays in the beginning while the electric field is on.…”

“…We are confident that the results presented here will shed light on the stability of fluid interfaces in electric-field-based applications such as electrocoalescence, electrocoagulation, microfluidics, electroemulsification, electrostatic atomization, etc. For instance, during coalescence of two droplets in the presence of an electric field and surface-active compounds, the evolved interfacial properties govern the kinetics of the coalescence. − In the electric-field-controlled microfluidic applications such as microreactor technology, bioparticle handling, assays, etc., future studies could investigate enhancement in the mass transport at/across the interfaces.…”

Molecular Dynamics Simulation of a Brine Droplet under an Electric Field: Distinct Behavior Shown by NaCl and CaCl2

“…Emulsions commonly exist in many industrial processes such as food processing, metal manufacturing, and petroleum production. − As a specific example, water-in-oil emulsion is routinely encountered in bitumen froth treatment of oil sands production, among other emulsions such as oil-in-water and more complex water-in-oil-in-water emulsions. , The existence of emulsions in bitumen froth treatment can lead to corrosion and fouling issues, resulting in additional costs and environmental concerns. , It is challenging to separate small dispersed water droplets from the oil phase, especially when the emulsions are stabilized by indigenous compounds in the crude oil, such as asphaltenes and resins. ,− Electrostatic demulsification by applying an external electric field is a promising and cost-effective method. ,, However, the omnipresence of salt ions in water , can influence the effectiveness of electrostatic demulsification. Salt ions can interact with emulsion stabilizers, and these two species can respond differently to the electric field. ,− As a result, they might function synergistically or competitively in facilitating or inhibiting the deformation and coalescence of water droplets. It is therefore of great interest and significance to investigate the response mechanism of water-in-oil emulsion when exposed to an electric field and under the collective influence of salt ions and interface-active emulsion stabilizers.…”