- Dynamic interfacial tension and surfactant stabilisation during membrane emulsification:
Dynamic interfacial tension and surfactant stabilisation during membrane emulsification:
how to avoid drop coalescence and membrane wetting
Determine the mechanisms of interaction of complex liquid systems with porous membranes used for the membrane emulsification.
Originality and innovative aspects: Static and dynamic wetting of solid surfaces by liquids in the presence of complex fluids, is a key aspect of the process of ‘membrane emulsification’. This process holds great potential for industrial use, but it is slow to be adopted due to a lack of understanding and, therefore, reliable and reproducible operation. This is mainly due to a poor understanding of the interaction of complex liquid systems with the porous membrane used for the emulsion, and the interfacial tension variation due to the growing emulsion droplet during formation at the membrane surface. The innovative aspect of this WP is the development of understanding of the interaction of complex liquids with the membrane.
Methodologies: Study of drop growth at different concentrations of various surfactants using the microscopy; characterization of the surfactant diffusion; experiments on wetting dynamics, especially spreading in “upside down” position, experimental investigation of the single drop emerging from a membrane pore under different surface shears and for different compositions of liquid. This research will be conducted in collaboration with LU.
List of publications
Title: Azimuthally oscillating membrane emulsification for controlled droplet production
Authors: Pedro S. Silva, Mike Stillwell, Bruce Williams, Marijana M. Dragosavac, Goran T. Vladisavljević, Hemaka C. H. Bandulasena and Richard G. Holdich
Abstract: A novel membrane emulsification (ME) system is reported consisting of a tubular metal membrane, periodically azimuthally (tangentially) oscillated with frequencies up to 50 Hz and 7 mm displacement in a gently cross flowing continuous phase. A computational fluid dynamics (CFD) analysis showed consistent axial shear at the membrane surface, which became negligible at distances from the membrane surface greater than 0.5 mm. For comparison, CFD analysis of a fully rotating ME system showed local vortices in the continuous phase leading to a variable shear along the axis of the membrane. Using an azimuthally oscillating membrane, oil-in-water emulsions were experimentally produced with a median diameter of 20–120 μm, and a coefficient of variation of droplet size of 8%. The drop size was correlated with shear stress at the membrane surface using a force balance. In a single pass of continuous phase, it was possible to achieve high dispersed phase concentrations of 40% v/v.
© 2015 American Institute of Chemical Engineers AIChE J, 2015