Enhancement of Flux Performance in PTFE Membranes for Direct Contact Membrane Distillation

Abstract

This work focused on enhancing the flux on hydrophobic polymeric membranes aimed for direct contact membrane distillation desalination (DCMD) process without compromising salt rejection efficiency. Successful coating of commercial porous poly-tetrafluoroethylene membranes with poly(vinyl alcohol) (PVA) was achieved by solution dipping followed by a cross-linking step. The modified membranes were evaluated for their performance in DCMD, in terms of water flux and salt rejection. A series of different PVA concentration dipping solutions were used, and the results indicated that there was an optimum concentration after which the membranes became hydrophilic and unsuitable for use in membrane distillation. Best performing membranes were achieved under the specific experimental conditions, water flux 12.2 L·m-2·h-1 [LMH] with a salt rejection of 99.9%. Compared to the pristine membrane, the flux was enhanced by a factor of 2.7. The results seemed to indicate that introducing hydrophilic characteristics in a certain amount to a hydrophobic membrane could significantly enhance the membrane distillation (MD) performance without compromising salt rejection.

Porous Hydrophobic–Hydrophilic Composite Hollow Fiber and Flat Membranes Prepared by Plasma Polymerization for Direct Contact Membrane Distillation

“…A thin layer of polyvinyl alcohol (PVA) was coated successfully on a porous PTFE membrane by solution dipping followed by a cross-linking step to reduce the gas-filled pore length by a hydrophilic coating of polyvinyl alcohol. The water flux achieved with a 30 g/L salt solution was 12.2 L/m 2 -h with a salt rejection of 99.9% for a feed temperature of 60 °C and distillate temperature of 17 °C [ 29 ]. A novel dual-layer flat membrane consisting of a thin hydrophobic top-layer of PVDF and a relatively thick hydrophilic PVDF-PVA sub-layer was fabricated using the non-solvent thermally induced phase separation (NTIPS) method [ 30 ]; the water vapor flux achieved was quite high.…”

Stability of Ar/O2 Plasma-Treated Polypropylene Membranes Applied for Membrane Distillation

“…For this reason, in order to separate the feed from the distillate obtained, it is necessary to maintain a vapor layer inside the membrane. Most often, it is obtained using porous membranes made of highly hydrophobic polymers such as polypropylene (PP) [ 8 ], polytetrafluoroethylene (PTFE) [ 9 ] and polyvinylidenefluoride (PVDF) [ 10 ].…”

Boron Removal by Membrane Distillation: A Comparison Study

“…LEP can be evaluated by [ 22 , 23 , 24 ]: where are the liquid surface tension, contact angle, and maximum pore size, respectively. It was proposed to use poly(vinyl alcohol) (PVA) as a coating material [ 25 ] or a cover for the membrane surface by surface micropillars [ 26 ] to resolve these issues.…”