Characterization of Hydrophobic Polymeric Membranes for Membrane Distillation Process

Abstract

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.

Evaluation of vapor mass transfer in various membrane distillation configurations: an experimental study

“…9), although different in pore size, showed similar fluxes under the same conditions. This result can be related to the similar fibrous morphology of Gore membranes [39], thus affecting in the same way the heat and mass transfer [28]. Also in this configuration GVS membrane (Fig.…”

“…10) exhibited fluxes lower than Gore membranes under the same conditions. As previously mentioned, this difference can be related to the different nature of the membrane, which shows a different morphology [39], which presumably affect vapor mass transfer.…”

Hydrophobic polyethersulfone porous membranes for membrane distillation

“…Thus, MD technology is an emerging process for water desalination at moderate temperatures and very low pressures [1,2]. It has been investigated worldwide as a low cost, energy saving alternative to conventional separation processes such as distillation and reverse osmosis (RO).…”

“…The driving force for mass transfer is the difference in vapor pressure between the feed and permeate sides of the membrane [1,3]. Membrane distillation can be classified into different types based on the method used to create the pressure difference, such as direct contact membrane distillation (DCMD), air gap membrane distillation, vacuum membrane distillation (VMD) and sweeping gas membrane distillation [1][2][3][4][5][6][7][8][9][10][11][12][13].…”

The investigation of ethanol separation by the membrane distillation process

“…Non-volatile solutes contained in the feed are completely retained by the membrane 8 . The driving force for mass transfer is the difference in vapour pressure between the feed and the permeate side of the membrane 9 . During the MD of ethanol solution the vapour pressure of ethanol is higher than water, therefore, the ethanol vapour is transferred preferentially through the membrane pores than the water vapour due to the partial pressure gradient existing across the membrane 10,11 .…”