N 0 o 0 o oo

mrnrnmsmm

dispersed liquid

Figure 3. Principle of Membrane Emulsification

A schematic diagram of the continuous membrane emulsification apparatus is shown in Fugire 4(a). The continuous method consists, mainly, of SPG membrane module, a pump for pressure source, dispersion phase (Liquid 1), a storage vessel, an emulsion vessel and a circulation pump for continuous phase (Liquid 2). In the case of a batch method, the bottom of the SPG membrane was sealed by fusion and was immersed in Liquid 2 as shown in Figure 4(b). Liquid 1 was pressured into a Liquid 2 from the inside of the SPG membrane using the same procedure as for the continuous method. The change in water pressure during emulsification can be monitored by a pressure gauge. A commercially available SPG membrane emulsification apparatus is depicted in Figure 5.

3.2. Preparation of Monodispersed Emulsions by Membrane Emulsification Technique

3.2.1.0/W emulsion

Oil-in-water emulsion was successfully produced by Nakashima and Shimizu using a membrane emulsification technique (12). The photomicrographs of a O/W emulsion prepared by the SPG membrane emulsification technique and conventional homogenization technique are shown in Figures 6 and 7, respectively. These emulsions were made using the soybean oil containing lwt. % of Span 80 and water containing lwt. % Tween 20 and lwt. % of NaCl. The interfacial tension of this system was 1.5 dyne/cm. The mean pore diameter (Dp) of SPG membrane

Pressure gauge

Pressure gauge

Membrane Emulsification Technique

(a) Continuous method (b) Batch method

Figure 4. Schematics of an apparatus for the SPG membrane emulsification technique

(a) Continuous method (b) Batch method

Figure 4. Schematics of an apparatus for the SPG membrane emulsification technique

Spg Membrane Emulsification Technique
Figure 5. Photograph of commercially available SPG membrane emulsification apparatus (Courtesy of Fuji-Silysia Chemical Ltd.)

used was 0.70 nm. A monodispersed emulsion was obtained using the SPG membrane emulsification technique (Figure 6) while a polydispersed emulsion was obtained using a homogenizer (Figure 7). A comparison of the size distribution for droplets obtained using the SPG membranes to that obtained using the conventional method is shown in Figure 8. In this case, kerosine was used as an oil phase and 0.2% SDS as a water phase. Porous ceramic membrane yielded a very wide size distribution, while the SPG membrane yielded a very narrow size distribution of the oil droplets. The oil droplets were stabilized by the electrical double layer repulsion force and/or a steric repulsion force of adsorbed surfactant layer. In the case of membrane emulsification, the mean diameter of the oil droplet (D0) is related to the mean pore diameter of SPG membrane (Dp) used by Eqn. (3) (18).

0 0

Post a comment