CHARACTERIZATION OF HYDROPHOBIC POLYMERIC MEMBRANES FOR MEMBRANE DISTILLATION PROCESS

Hydrophobic microporous membranes are utilized in membrane distillation (MD) processes, e.g. seawater desalination at moderate temperatures. The vapour permeability of commercial hydrophobic membranes with different pore sizes (0.2-1 micron) was characterized through a simple apparatus designed-on-purpose. A cylindrical vessel had a face closed by the membrane and the other connected to a thin graduate tube. The water level variation in the tube is recorded and related to the vapour flux across the membrane. Measurements were taken in the temperature range 20-80°C. A fan tangential to membrane surface was employed to maintain a constant driving force for vapour transport. Vapour flux did not depend on pore dimension, but the membrane and support material resulted to influence the mass transfer. Moreover, the results showed that the main resistance for mass transfer is located in the permeate side, thus addressing future works on the set up of a MD pilot unit.