Investigation on the effects of a mechanical shear-stress modification method during cross-flow membrane emulsification

This study deals with an alternative method for increasing the shear-stress at the membrane surface while maintaining a low value along the circuit out of the membrane during emulsification process. With a simple mechanical method, by using turbulence static promoters, it was possible to obtain very good emulsion quality in terms of droplet size distribution and stability, even operating at high dispersed phase flux values. Soybean oil was emulsified in aqueous Tween 80 solution with a simple cross-flow apparatus equipped with SPG membrane having 3.1 μm pore size. Two kinds of cross-section reducer elements (a smooth cylindrical and a helix-shaped) were installed within the lumen side of the tube membrane. Results were compared with the conventional cross-flow membrane emulsification method. During the tests the rotation of the recirculation pump was kept at low level to minimize mechanical stress and energy consumption. After the investigation of the effect of the driving force and shear-stress on the quality of the o/w emulsion, a model was established. To verify the durability of the novel method, long term emulsification, was carried out as well. Emulsions up to 38% of oil concentration were obtained. Results demonstrated that, with this simple modification, it was possible to prepare o/w emulsion with narrow droplet size distribution using low aqueous-phase flow rate compared to other cross-flow membrane emulsification. Productivity could also be increased obtaining high emulsion quality.