The influence of interfacial tension on rejection and permeation of the oil droplets through a slit pore membrane

Abstract

The study investigates the influence of interfacial tension between oil and water on permeation and rejection of oil drops during produced water treatment using a slotted pore metallic membrane. It was found experimentally and analytically that rejection and permeation of oil drops through the membrane had a direct relation with the interfacial tension between oil and water. Oil/water emulsions with a wide range of interfacial tension (4, 9, 15, 30, 35 40 and 47 mN/m) were tested experimentally and analytically and a comprehensive set of data is presented. Higher the interfacial tension between oil and water phases provided a better rejection and lower permeation through the slits of the membrane. In a slit structured pore membrane, the oil drops were assumed to be passing through slots by the drag force generated by the flow of the fluid passing around the drops. The drag force push and distorte the spherical shape of the deforming oil drops. On the other hand, the force that is referred as the static force tries to restore the spherical shape of the drops and plays an important role in the rejection of drops. The static force and the interfacial tension are directly associated with each other. The drag force and the static force counter each other at every stage. Higher the drag force than the static force causes permeation of the drops, while, in case of higher static force than the drag force, rejection of drops was dominant. Experimentally higher rejection was achieved with the highest interfacial tension system.