Numerical simulation on the effect of contact angle on the permeation of emulsions through a membrane in premix membrane emulsification

Abstract

The effect of membrane wettability on emulsion permeation behavior in premix membrane emulsification was investigated. The Volume of Fluid (VOF) method was employed to simulate the permeation of a single droplet through pore channel constrictions of a microporous membrane. The wettability was adjusted by varying the wall contact angle between 0 and 180 degrees.

For contact angles less than 90 degrees, lower angles resulted in complete wetting of the membrane, leading to lower capillary pressures but higher critical pressures for the dispersed phase to permeate through the membrane. Conversely, as the contact angles increase, the capillary pressures increase while the critical pressure required for permeation reduces due to decreased wettability of the channel walls. For contact angles greater than 90 degrees, the deformed droplets did not wet the channel walls and reformed into spherical droplets upon exiting the channel. In this regime, the critical pressure for droplet permeation showed an inverse relationship with the contact angle. The capillary pressure was associated with the continuous water phase that wetted the channel walls, rather than with the droplet itself. As the contact angle increased, the degree of wetting by the continuous phase also increased, resulting in the lowest critical pressure observed at a contact angle of 180 degrees. Optimizing the contact angle can minimize process energy requirements while ensuring efficient droplet passage through the pore constriction. This contributes to more sustainable and cost-effective processes in various industries such as emulsification, oil separation, and microfiltration.