Dispersive Contacting in a Membrane Contactor

Large-scale studies of OD have been conducted (Sirkar, 1995). Highly successful studies on DCMD for brine solutions have also been implemented by Li and Sirkar (2004). Pilot-plant studies have been recently completed successfiiUy by the same group. For a recent review of both OD and MD, see Curcio and Drioli (2005). 

The dispersion creation requites application of a pressure difference, AF, between the phase to be dispersed and the phase in which dispersion takes place through the pores. This AF has two contributions (1) capUlary pressure AFcr defined by Eq. (26.4) and (2) viscous flow pressure drop APflow through the capillary, which is the membrane pore (usually calculated from Hagen-PoiseuiUe law). The wetting characteristics of the pore material as well as the membrane channel are important for the emulsification process, especially, the nature of the emulsion produced. An earlier review of membrane-based emulsification is available in Joscelyne and Tragard (2000). A comparison of membrane emulsification with that through porous microchannel plate is provided in Lambrich and Schubert (2005). 

When two miscible phases have to be contacted by dispersing one in the other, traditionally conventional stirred mixers arc employed. One can also use porous membranes to mix two miscible phases. Zarkadas and Sirkar (2006) have employed porous hydrophobic hollow-fiber membranes to force either an isopropanol phase or an aqueous solution of an amino acid into the other phase. This was done to carry out antisolvent-based crystallization. Extraordinarily high rates of crystallization were achieved with much smaller crystal size. 

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