Membrane emulsification — a literature review

Membrane emulsification is a simple method that has received increasing attention over the last 10 years, with potential applications in many fields. Experimental studies which have focused mainly on investigations of process parameters such as, membrane type, average pore size and porosity, crossflow velocity, transmembrane pressure and emulsifier, are reviewed. By careful choice of these parameters, emulsions with narrow emulsion droplet size distributions have been produced, with average droplet sizes ranging between 2 and 10 times the nominal membrane pore diameter. The effects of individual parameters are reasonably well understood, particularly at a qualitative level. Results can be explained by a direct influence of the membrane pore size, diameter and distribution. Interfacial tension and the action of wall shear stress are also important. In comparison with conventional turbulence based methods, such as homogenization and rotor-stator systems, less energy is needed to produce droplets of a given size using membrane emulsification. However, one of the main limiting factors with regard to industrial scale-up can be the often low level of dispersed phase flux through the membrane, especially for small submicron droplets.