Preparation of Emulsions with a Narrow Particle Size Distribution Using Microporous α‐Alumina Membranes

Abstract

O/W emulsions with the smallest spans of particle size distribution (PSD) [span = (d ₉₀ − d ₁₀)/d ₅₀] reported until now for ceramic α‐alumina membranes (0.42–0.56) were prepared using a 1.4‐µm membrane cleaned thoroughly after use in an ultrasonic bath. The smallest span values of 0.42–0.48 were achieved at transmembrane pressures 2.6–3.5 times greater than the capillary pressure. A narrow particle size distribution with a span of 0.48–0.49 was obtained at a wall shear stress of 0.55 Pa, provided that the dispersed phase flux was not above 4.6 L m² h⁻¹. The span and mean droplet size were remarkably constant over the 1–10 vol.% range of dispersed phase content. Membrane cleaning by ultrasonication was one of the critical conditions for successful operation. If the membrane was cleaned only by the cleaning in place (CIP) method, emulsions with a span value in the range of 0.7–1.4 were obtained.

Keywords:

• Membrane emulsification
• α‐alumina membrane
• SPG membrane

Acknowledgment

The authors wish to thank the Alexander von Humboldt Foundation, Bonn, Germany for financial support of this work.