ABSTRACT
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
II. SPG Membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
A. Pore Structure of SPG Membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
B. Permeability of SPG Membrane to Pure Liquids . . . . . . . . . . . . . . . . . . . . . . . 399
C. Hydrodynamic Resistance of SPG Membrane . . . . . . . . . . . . . . . . . . . . . . . . . 401
D. Pore Tortuosity and Number of Pores per Unit Cross-Sectional
Area of SPG Membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402
III. Membrane Emulsification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404
A. Principles and Methods of ME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404
B. Direct ME in Cross-Flow System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406
1. Influence of Operating Parameters on Emulsification Results . . . . . . . . . . 410
a. Influence of Transmembrane Pressure . . . . . . . . . . . . . . . . . . . . . . . . 410
b. Influence of Wall Shear Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411
c. Influence of Disperse Phase Content . . . . . . . . . . . . . . . . . . . . . . . . . 412
d. Influence of Mean Pore Size and Comparison of SPG Membranes
with Other Membranes and Emulsification Methods . . . . . . . . . . . . . 414
2. Stability of Prepared O/W Emulsions . . . . . . . . . . . . . . . . . . . . . . . . . . . 414 3. Direct Microscopic Observation of Droplet Formation
at the Surface of SPG Membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416
C. Premix ME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417
1. Influence of Operating Parameters on Emulsification Results . . . . . . . . . . 420
a. Influence of Transmembrane Pressure . . . . . . . . . . . . . . . . . . . . . . . . 420
b. Influence of Number of Emulsification Cycles and
Disperse Phase Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429
Membrane emulsification (ME) is a new technology for making monodisperse emulsions over a
wide spectrum of mean droplet sizes, ranging from ca. 0.5 mm to several tens of micrometer. ME involves production of droplets individually (drop-by-drop) by extrusion of pure disperse
phase through a porous membrane into a moving continuous phase (direct ME) or by the
passage of a previously prepared coarse emulsion (premix) through the membrane (premix ME).
The membrane must not be wetted with the continuous phase; For instance, oil-in-water (O/W) emulsions are prepared using a hydrophilic membrane and water-in-oil (W/O) emulsions are prepared using a hydrophobic membrane. If the membrane wall is wetted with the continuous phase,
droplet disruption in coarsely emulsified feeds can be followed by phase inversion, that is, a fine W/O emulsion can be produced from the O/W coarse emulsion and vice versa. To force a pure disperse phase or pre-emulsified feed through the membrane, a pressure gradient across the membrane is
applied, usually by pressurizing the disperse phase with a compressed gas in a pressure vessel.
