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

Membranes ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 120 ◽  
Author(s):  
Ashok K. Sharma ◽  
Adam Juelfs ◽  
Connor Colling ◽  
Saket Sharma ◽  
Stephen P. Conover ◽  
...  
Keyword(s):  
Hollow Fiber ◽  
Direct Contact ◽  
Plasma Polymerization ◽  
Polyvinylidene Fluoride ◽  
Hydrophobic Surface ◽  
Diffusion Path ◽  
High Water ◽  
Membrane Distillation ◽  
Vapor Flux ◽  
Direct Contact Membrane Distillation

High water vapor flux at low brine temperatures without surface fouling is needed in membrane distillation-based desalination. Brine crossflow over surface-modified hydrophobic hollow fiber membranes (HFMs) yielded fouling-free operation with supersaturated solutions of scaling salts and their precipitates. Surface modification involved an ultrathin porous polyfluorosiloxane or polysiloxane coating deposited on the outside of porous polypropylene (PP) HFMs by plasma polymerization. The outside of hydrophilic MicroPES HFMs of polyethersulfone was also coated by an ultrathin coating of porous plasma-polymerized polyfluorosiloxane or polysiloxane rendering the surface hydrophobic. Direct contact membrane distillation-based desalination performances of these HFMs were determined and compared with porous PP-based HFMs. Salt concentrations of 1, 10, and 20 wt% were used. Leak rates were determined at low pressures. Surface and cross-sections of two kinds of coated HFMs were investigated by scanning electron microscopy. The HFMs based on water-wetted MicroPES substrate offered a very thin gas gap in the hydrophobic surface coating yielding a high flux of 26.4–27.6 kg/m2-h with 1 wt% feed brine at 70 °C. The fluxes of HFMs on porous PP substrates having a long vapor diffusion path were significantly lower. Coated HFM performances have been compared with flat hydrophilic membranes of polyvinylidene fluoride having a similar plasma-polymerized hydrophobic polyfluorosiloxane coating.

Effect of Hydrophobicity Degree on PVDF Hollow Fiber Membranes for Textile Wastewater Treatment Using Direct Contact Membrane Distillation

2013 ◽  
Vol 65 (4) ◽  
Author(s):  
N. M. Mokhtar ◽  
W. J. Lau ◽  
P. S. Goh
Keyword(s):  
Contact Angle ◽  
Hollow Fiber ◽  
Direct Contact ◽  
Polyvinylidene Fluoride ◽  
Textile Wastewater ◽  
Membrane Distillation ◽  
Hollow Fiber Membranes ◽  
Hydrophobic Membrane ◽  
Direct Contact Membrane Distillation ◽  
Fiber Membranes

The objectives of this study are to study the effect of hydrophobicity degree of  polyvinylidene fluoride (PVDF) hollow fiber membranes blended with different types of additives i.e. ethylene glycol (EG) and polyvinylpyrrolidone (PVP) on textile wastewater application. The degree of hydrophobicity of each membrane was analyzed using contact angle goniometer. The membrane morphology and gas permeability were characterized prior to filtration experiment. Both membranes were tested using direct contact membrane distillation (DCMD) system and their performances were evaluated with respect to water flux and dye removal. This study revealed that the membrane with higher contact angle has greater stability in terms of flux and dye rejection compared to the membrane with low hydrophobic property. This is mainly due to the low surface energy obtained by the highly hydrophobic membrane that prevented the liquids from both sides to penetrate through membrane pores.

Dye wastewater treatment by direct contact membrane distillation using polyvinylidene fluoride hollow fiber membranes

2015 ◽  
Vol 35 (5) ◽  
pp. 471-479 ◽  
Author(s):  
Nadzirah M. Mokhtar ◽  
Woei J. Lau ◽  
Ahmad F. Ismail
Keyword(s):  
Hollow Fiber ◽  
Membrane Fouling ◽  
Direct Contact ◽  
Polyvinylidene Fluoride ◽  
Gas Permeability ◽  
Hollow Fiber Membrane ◽  
Membrane Distillation ◽  
Reactive Black 5 ◽  
Pvdf Membrane ◽  
Direct Contact Membrane Distillation

Abstract The potential of 18 wt.% polyvinylidene fluoride (PVDF) hollow fiber membrane blended with ethylene glycol (EG) for the treatment of dye solution using direct contact membrane distillation (DCMD) system was investigated. The PVDF membrane was prepared using the dry-jet wet spinning method and was characterized in terms of membrane morphology, porosity, wetting pressure, gas permeability and degree of hydrophobicity. The membrane was tested using dye solution containing 0.5 g l-1 reactive black 5 (RB5). The experimental period was prolonged to 6 h in order to analyze the fouling tendency and membrane durability during the DCMD process. The results showed that the modified PVDF membrane was able to produce consistent flux (i.e., 9.82±0.52 kg m-2 h-1) throughout the DCMD experiment while maintaining excellent dye rejection (i.e., 99.86±0.04%). With respect to membrane fouling, it was found that the lumen side of the membrane was significantly stained with color (compared to outer membrane surface) due to the physical-chemical interaction between reactive dye and membrane structure. Although membrane fouling was experienced in this study, its impact on MD performance in terms of flux and rejection was negligible, mainly because MD is not a pressure-driven process.

scholarly journals Triple-Layer Nanofiber Membranes for Treating High Salinity Brines Using Direct Contact Membrane Distillation

Membranes ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 60 ◽  
Author(s):  
Mustafa Al-Furaiji ◽  
Jason T. Arena ◽  
Jian Ren ◽  
Nieck Benes ◽  
Arian Nijmeijer ◽  
...  
Keyword(s):  
Direct Contact ◽  
Polyvinylidene Fluoride ◽  
Water Flux ◽  
Feed Solution ◽  
High Water ◽  
Membrane Distillation ◽  
Pvdf Membrane ◽  
Direct Contact Membrane Distillation ◽  
Triple Layer ◽  
Layer Membrane

A composite, three-layered membrane for membrane distillation was prepared from electrospun polyvinylidene fluoride (PVDF) nanofibers supported by commercial polyethersulfone (PES) nanofiber based nonwoven from E.I. duPont de Nemours company (DuPont). The membranes were tested in direct contact membrane distillation (DCMD) using a 5.0 M sodium chloride brine as a feed solution. The triple layer membrane combines the hydrophobicity of PVDF and the robustness of the PES. The triple layer membrane demonstrated excellent performance in DCMD (i.e., relatively high water flux compared to the commercial PVDF membrane and a complete salt rejection of the brine) with mechanical properties imparted by the PES layer. This work is the first to demonstrate the use of a commercially produced nanofiber nonwoven for membrane distillation.

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

Membranes ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 52 ◽  
Author(s):  
Frank Y. C. Huang ◽  
Allie Arning
Keyword(s):  
United States ◽  
Hollow Fiber ◽  
Packing Density ◽  
Direct Contact ◽  
Polyvinylidene Fluoride ◽  
Water Flux ◽  
Membrane Distillation ◽  
Hollow Fiber Membranes ◽  
Direct Contact Membrane Distillation ◽  
Fiber Membranes

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.

Comparison of Sweeping Gas and Direct Contact Membrane Distillation: Module Length Effect

2020 ◽  
Author(s):  
Umar F. Alqsair ◽  
Ahmed M. Alshwairekh ◽  
Anas M. Alwatban ◽  
Robert Krysko ◽  
Alparslan Oztekin
Keyword(s):  
Direct Contact ◽  
Three Dimensional ◽  
Concentration Field ◽  
Local Variation ◽  
Membrane Distillation ◽  
Membrane Properties ◽  
Effect Of Temperature ◽  
Vapor Flux ◽  
Direct Contact Membrane Distillation ◽  
Sweeping Gas

Abstract Computational fluid dynamics simulations are conducted to compare the effect of module length in sweeping gas and direct contact membrane distillation systems for seawater desalination processes. In this work, the effect of temperature and concentration on the flux performance and temperature and concentration polarization characteristics are studied. CFD simulations are conducted in a three-dimensional module to characterize the steady-state velocity, temperature, and concentration field in the feed and permeate channel. The Reynolds number for the feed and the permeate stream is set to 500 and 1500, and thus the laminar flow model is adapted for each channel. The membrane properties are fixed in all cases considered. It is revealed that the local variation of the vapor flux, TPC, and CPC varies with module length in SGMD systems. However, the average values along the membrane in both module lengths do not vary much. Remedies for mitigating temperature polarization should be considered for future studies.

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