Influence of membrane morphology on pore activation in membrane emulsification

Why liquid displacement methods are sometimes wrong in estimating the pore‐size distribution

“…If this would have been a liquid displacement experiment, it would have been concluded that the membrane had a wide distribution, which is in contrast with the uniform pore sizes. We showed that the gradual increase in pore activation could be attributed to the presence of an extra resistance against flow below the parallel top layer pores (Gijsbertsen- Abrahamse et al, 2003). Furthermore, we found that if the pores within the membrane skin layer are interconnected, this leads to the same effect as described above: the lower side of the skin layer acts as an extra resistance below the pores that open up to the downstream side of the membrane.…”

“…This is especially true for the flux, which is approximately linearly dependent on the pressure gradient when ␦ m Ͼ 10. These linear dependencies substantially resemble the two-layer model, developed to describe pore activation in membrane emulsification (Gijsbertsen- Abrahamse et al, 2003). In the two-layer model, the membrane is assumed to be composed of two distinct structural layers: an unconnected pore layer having parallel pores and a sublayer, with each layer having a given resistance to fluid flow (Figure 2b).…”

“…Then the similarity between this model and a simpler two-layer model for uniform pores is shown (schematically in Figure 2b). The two-layer model was developed to describe pore activation in membrane emulsification (Gijsbertsen-Abrahamse et al, 2003). Finally, to include the effect of different pore sizes in the model, the two-layer model is extended.…”

“…Furthermore, we found that if the pores within the membrane skin layer are interconnected, this leads to the same effect as described above: the lower side of the skin layer acts as an extra resistance below the pores that open up to the downstream side of the membrane. In experiments with a ceramic membrane of 150 m thickness the activation of pores with increasing transmembrane pressure was very gradual (Gijsbertsen- Abrahamse et al, 2003). This could not be attributed to pore size differences only because if we consider the transmembrane pressures at which oil started to flow through the pores, then the pores that became active at higher pressures would have been several times smaller than the first active pore.…”

Interfacial aspects of water drop formation at micro-engineered orifices

“…The ratio found for the 7 µm silicon nitride array was 3.7. The authors claim that a higher ratio leads to a higher number of active pores [26]. Here, micro-orifice arrays were used with an open substructure, which results in a lower flow resistance in the substructure, and with smaller pore sizes resulting in higher flow resistances in the pores.…”