Performance Comparison between Polyvinylidene Fluoride and Polytetrafluoroethylene Hollow Fiber Membranes for Direct Contact Membrane Distillation

Abstract

Increasing water demand coupled with projected climate change puts the Southwestern United States at the highest risk of water sustainability by 2050. Membrane distillation offers a unique opportunity to utilize the substantial, but largely untapped geothermal brackish groundwater for desalination to lessen the stress. Two types of hydrophobic, microporous hollow fiber membranes (HFMs), including polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), were evaluated for their effectiveness in direct contact membrane distillation (DCMD). Water flux and salt rejection were measured as a function of module packing density and length in lab-scale systems. The PVDF HFMs generally exhibited higher water flux than the PTFE HFMs possibly due to thinner membrane wall and higher porosity. As the packing density or module length increased, water flux declined. The water production rate per module, however, increased due to the larger membrane surface area. A pilot-scale DCMD system was deployed to the 2nd largest geothermally-heated greenhouse in the United States for field testing over a duration of about 22 days. The results demonstrated the robustness of the DCMD system in the face of environmental fluctuation at the facility.

Recent Developments in Nanomaterials-Modified Membranes for Improved Membrane Distillation Performance

“…On the other hand, contact angle, sliding angle, surface roughness, and LEPw measurements provide insight into the membrane’s hydrophobicity. The membrane should have low mass transfer resistance and thermal conductivity, while also maintaining high thermal and chemical stability for the performance required [ 46 ]. Table 1 provides an outline of the desired characteristics required in membranes that are currently used for the MD application.…”

Polyvinylidene Fluoride Membrane with a Polyvinylpyrrolidone Additive for Tofu Industrial Wastewater Treatment in Combination with the Coagulation–Flocculation Process

“…Of all polymeric materials, such as polysulfone (PSF), polypropylene (PP), polytetrafluoroethylene (PTFE), polyethylene (PE), and polyvinylidene fluoride (PVDF) [20,21], the PVDF membrane is the most extensively employed membrane used to fabricate UF and MF membranes since it has outstanding mechanical, physical, and chemical properties, as well as excellent thermal stability [22,23]. Although PTFE has a similar structure and advantages when compared to PVDF, PTFE has a high density whereas PVDF has a low density and higher porosity, which generally results in a higher water flux [24]. In addition, the PVDF membrane has the capacity to separate organic matter, including carbohydrates, proteins, and fats, and also possesses a high oxidant tolerance and great mechanical strength with excellent resistance to fouling [19].…”

Experimental and modeling investigation of ultrafine polyvinylidene fluoride hollow fiber membrane module for recovery of lactic acid from aqueous solutions

“…Huang and Arning in their study fabricated PVDF hollow fiber membrane for desalination application. [27] The tight pore structure of the sponge layer facilitated prevention of brackish water from intruding into the membrane. During the reactive extraction of lactic acid, organic solvent was in contact with the exterior surface (shell side) of the HFMs while aqueous lactic acid was in contact with the interior (lumen side) of the HFM.…”