Membrane applications dispersion technique

Premix membrane emulsification is a powerful technique, especially where the system does not induce internal fouling of the membrane used, and where high volume fractions of the dispersed phase are required. This probably limits the applications mostly to (fine) chemicals production, but one may expect a few applications in the food industry as well. 

Another type of application for synchrotron radiation is based upon the possibility to continuously vary the wave-length and perform diffraction experiments close to the absorption edge of a specific element. This approach, termed anomalous dispersion or resonant scattering is in principle well suited to obtain spatial information on certain groups of atoms within a membrane assembly, notably bound metal ions, but has so far not found broader use in this field. For a review on this technique, see the chapter by Stuhrmann in this volume. 

Another technique is to assemble the particles under the influence of a liquid flow field, as achieved by filtering the dispersion. A membrane with pore sizes smaller than the particle diameter is used while continuously drawing the dispersion through a funnel, and the colloidal particles are retained at the membrane surface and accumulate [30,52]. Simultaneous application of an oscillating shear field during the filtration process improves the quality of particle ordering [53]. 

In the emulsion technique, solutions are mixed and dispersed into a nonmiscible phase. For food applications, vegetable oils are used as the continuous phase. In some cases, emulsifiers are added to form a better emulsion, since such chemicals lower the surface tension, resulting in smaller droplets. After emulsion formation, gelating and/or membrane formation is initiated by cooling and/or addition of a gelling agent to the emulsion, or by introducing a cross-linker. In a last step, the gel particles formed are washed to remove oil (Chan et al., 2002). 

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