Microfiltration driving potential

Microfiltration (MF) is a process that is used to filter very fine particles (smaller than several microns) in a suspension by using a membrane with pores that are smaller than the particles. The driving potential here is the difference in hydraulic pressure. 

Although the driving potential in microfiltration is the hydraulic pressure gradient, the microfiltration flux is often also affected by the fluid velocity along the membrane surface. This is invariably due to the accumulation of filtered particles on the membrane surface in other words, the concentration polarization of particles. 

Membrane operation is a specific, but not exotic, operation. In fact it is a hybrid of classical heat and mass transfer processes (Figure 4.1). Direct contact mass transfer operations tend to reach equilibrium due to a difference of chemical potential between two phases that are put into contact. In the same way, temperature equilibrium is aimed at during heat transfer operations, for which driving force is a temperature gradient. In contrast, for membrane operations, by using the specific properties of separation of the thin layer material that constitutes the membrane, under the particular driving force that is applied, it is possible to deviate from the equilibrium that prevails at fluid-to-fluid interphase with classical direct contact mass exchange systems and to reorientate the mass transfer properties. In particular, this is the case with classical operations such as microfiltration (MF), ultrafiltration (UF), reverse osmosis (RO), gas separation (GS), pervaporation (PV), dialysis (DI) or electrodialysis (ED), for which a few characteristics are recalled in Table 4.1. 

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