Droplet Demulsification Using Ultralow Voltage-Based Electrocoalescence

Abstract

Demulsification of droplets stabilized with surfactant is very challenging due to their low surface energy. We report ultralow voltage-based electrocoalescence phenomenon for the demulsification of aqueous droplets with an aqueous stream. In the absence of electric field, due to the disjoining pressure resulting from the tail-tail interaction between the surfactant molecules present on the aqueous droplets and interface, coalescence of aqueous droplets with the aqueous stream is prevented. However, above a critical electric field, the electrical stress overcomes the disjoining pressure, thus leading to the droplet coalescence. The influence of surfactant concentration, droplet diameter, and velocity on the electrocoalescence phenomena is studied. The macroscopic contact between the aqueous droplet with the aqueous stream enables droplet coalescence at much lower voltage (10 to 90 V), which is at least two orders of magnitude smaller than voltages used in prior works (1.0 to 3.0 kV). The electrocoalescence phenomena is used for the extraction of microparticles encapsulated in aqueous droplets into the aqueous stream and size-based selective demulsification. A new paradigm of droplet electrocoalescence and content extraction is presented that would find significant applications in chemistry and biology.

Charge-Transfer-Induced Noncoalescence and Chain Formation of Free Droplets under a Pulsed DC Electric Field

“…Droplet manipulation by electric field has been attracting enormous attention due to its broad application prospects in various fields, such as electrospraying, , electrospinning, , electrowetting, , ink-jet printing, and droplet generation in microfluidic devices . Especially in the petrochemical industry, a high-voltage electric field is extensively used for dehydrating crude oil emulsion in oil fields and refineries because of its high-efficiency and environmental friendliness. − The settling velocity of a droplet is linearly proportional to the radius of the droplet . After the electric field is applied, electric forces are induced on the surface of the droplet due to the differences in the permittivities and conductivities between the oil and water .…”

Elaboration of the Demulsification Process of W/O Emulsion with Three-Dimensional Electric Spiral Plate-Type Microchannel

“…Before demulsification and oil-water two phase separation, emulsion droplets are proposed to coalesce by breaking the interfacial film between two droplets. The fast-growing, high-efficiency demulsification process might be due to coalescence propagation [42,43]. Obviously, the induction period is the pre-demulsified process for droplets to aggregate and coalesce before the fast-growing, high-efficiency demulsification process.…”

New Amphiphilic Ionic Liquids for the Demulsification of Water-in-Heavy Crude Oil Emulsion

“…For that, the emulsified water should be separated before transportation and refining [ 4 , 5 ]. Chemical, physical, and biological techniques have been applied for the demulsification of crude oil emulsions [ 6 , 7 ]. The use of chemical demulsifiers is one of the most applied techniques due to their fast demulsification and low cost [ 8 ].…”