Pulsed back-and-forward cross-flow batch membrane emulsification with high productivity to obtain highly uniform and concentrate emulsions

• O/W emulsions were prepared by pulsed back-and-forward cross-flow batch membrane emulsification.
• The continuous phase was tangentially agitated by inverting the flow direction back-and-forward within the membrane lumen.
• The effect of frequency and amplitude of pulsed flow and the dispersed phase flux was evaluated.
• Results were compared with the conventional cross-flow membrane emulsification and static membrane emulsification.
• Uniform emulsions whit high dispersed phase concentration were produced.

Membrane emulsification of soybean oil in an aqueous solution of 2 wt% Tween 80 was performed using pulsed back-and-forward flow. A tubular Shirasu porous glass (SPG) membrane with mean pore diameter of 3.1 μm was used. Soybean oil was pressed through the membrane and the force that determines droplets detachment was exerted by the continuous phase tangentially agitated by inverting the flow direction back-and-forward within the membrane lumen. Alternatively, droplets were spontaneously detached from the pore opening in the absence of shear flow at the membrane surface.The main advantage of the pulsed back-and-forward cross-flow membrane emulsification is that it eliminates the shear stress outside of the membrane related to the recirculation of emulsion droplets along the pump and fitting circuit as it happens in conventional cross-flow membrane emulsification. Results obtained indicated that it was possible obtaining uniform emulsion droplets also when high concentration of dispersed phase was reached with high productivity comparing with the traditional cross-flow membrane operation. The method is suitable for the production of monodispersed particles containing bioactive molecule (that are shear sensitive) or viscous dispersed materials or large droplets.