A new method for permeability measurement of hydrophobic membranes in Vacuum Membrane Distillation process

In this paper, a new method for permeability measurement of hydrophobic membranes used in Vacuum Membrane Distillation, instead of common measurement methods, was proposed. As VMD is a pressure and temperature driven process, the idea of this work is to propose a new water vapour permeability measurement method based on variation of feed temperature at a fixed vacuum pressure. This new method showed a greater stability and simplicity than the existing pressure variation method by not only allowing a wide range of feed temperature (25 °C ÷ 60 °C) to be scanned continuously, but also avoiding fluctuations of the system as observed in the pressure variation test. Permeabilities of two different kinds of hydrophobic membranes were measured by this new method and also by the existing pressure variation test. A comparison between these two methods was also presented to assess the feasibility and applicability of this new method.

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► Knudsen permeation of pure water through the membrane was performed.
► Driving force is created either by varying permeate pressure or inlet temperature.
► The new proposed method provides a greater stability and simplicity than the existing one.
►  Fluoropore and Durapore hydrophobic membranes were tested for cross-check.
► Permeability measurement by temperature variation method is suggested.