Selective hydrophilization of the permeate surface to enhance flux in membrane distillation

Abstract

This paper reports the development of novel hydrophilized membrane for water desalination using direct contact membrane distillation (DCMD). The permeate side of a porous polytetrafluoroethylene (PTFE) membrane on polypropylene (PP) support was hydrophilized by chemical treatment with oxidizing agents to enhance the rapid condensation and removal of permeated vapors. Depending upon the process conditions, permeate flux was as high as 61 L/m 2 .hr, and as much 73% higher than an unmodified membrane. 58% increase in overall mass transfer coefficient was also observed with the hydrophilized membrane. In short, hydrophilization of membrane surface showed enhanced flux at lower temperature, making this a more energy efficient process.

Immobilization of Graphene Oxide on the Permeate Side of a Membrane Distillation Membrane to Enhance Flux

“…Although, the feed side layer remains unchanged in GOIM-P, the hydrophilic surface permitted fast water vapor removal, destabilization of vapor-gap, and mass transfer resistance reduction between the bulk permeate and membrane surface. These effects are equivalent to the contraction in permeate side boundary layer [ 16 , 60 , 61 ], which led to an enhancement in water vapor permeation through the membrane.…”

“…The process can be conducted at a relatively low temperature (50–90 °C), hence waste heat, solar energy, or geothermal energy can be utilized as heat sources for heating the brine [ 11 , 12 , 13 , 14 , 15 ]. Other advantages include high rejection of the dissolved non-volatile species, able to handle highly concentrated brine with less fouling, low operating pressure, and less space requirement when compared to MSF [ 8 , 16 , 17 , 18 ]. However, MD still is faced with some barriers, such as relatively low water vapor flux in comparison with other conventional systems, flux reduction due to temperature and concentration polarization, pore wetting and membrane fouling, and lack of high-efficiency membranes [ 19 , 20 ].…”

“…In MD, membrane itself plays the crucial role in enhancing the flux and selectivity. While most of the researches have focused on different membrane modifications [ 24 , 27 , 28 , 30 , 33 , 48 ], our previous studies have shown that permeate side hydrophilization of the membrane can significantly improve the water vapor permeation rate [ 16 ]. The rapid water vapor removal from the permeate side boundary layer is one of the most important consideration in increasing the concentration gradient for enhanced mass transfer.…”

PVDF membrane assisted by modified hydrophobic ZnO nanoparticle for membrane distillation

“…Regarding potable water shortage and producing it from endless saltwater resource, different processes have been developed for water distillation, in which membrane desalination (MD) has been known as a restively new technique to provide pure water from brackish water resource . MD is one of the thermal membrane separation processes, which vapor molecular transports through nonwetted porous hydrophobic membranes from feed to permeate side . The temperature difference between the two sides provides a partial pressure difference across the membrane as a driving force of MD .…”

Unsupported electrospun membrane for water desalination using direct contact membrane distillation

“…Compared to the reverse osmosis process, MD is less sensitive to fouling and can completely reject salt (99.9%). The energy consumption of the MD process can also be significantly reduced with the use of heat pipes and solar collectors 1–4 …”