Microporous membranes in membrane distillation

Abstract - When a microporous hydrophobic membrane separates two aqueous solutions at different temperatures, selective mass transfer across the membrane is obtained. The process can be carried out at the atmospheric pressure and at temperatures which might be much lower than the boiling point of the solution. At the optimal membrane microporosity, polymer hydrophobicity and thermal conductivity, only water vapor is transported in the membrane phase and condenses as liquid on the low temperature side of the membrane. The driving force is the vapor pressure difference between the liquids at the two solution-membrane interfaces. Various hydrophobic polymeric membranes are available, prepared from polypropylene, PVDF and Teflon, in the flat sheet or capillary configuration. The membranes prepared by thermal phase—separation technique are particularly interesting.