Effect of ionic liquid on the structure and desalination performance of PVDF‐PTFE electrospun membrane (original) (raw)
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Journal of Membrane Science, 2013
Polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) membranes were prepared via the electrospinning method. Three sets of mats, with different fiber diameters and physical properties, were obtained by varying polymer concentration from 10 to 15 wt%. Membranes were formed by hot pressing the prepared mats to fuse the fibers. As prepared mats were hot pressed in order to control the membranes dimensional stability and mechanical strength and to alter the pore size and pore size distribution. The effects of hot pressing and variation of fiber diameter on pore size distribution, porosity, contact angle, gas permeation, and liquid water entry pressure (LEP) of the fabricated membranes were all studied. Optimized membranes were obtained with mean pore size, porosity, contact angle and LEP of 0.26 μm, 58±5%, 125°±2.41 and 19.1 psi, respectively. Fabricated membranes were tested for desalination by direct contact membrane distillation and a water flux value of 20–22 L h−1 m−2 was obtained with a salt rejection (SR) ratio of 98%.► Electrospun PVDF-HFP membrane developed for MD applications. ► Heat pressing of electrospun membrane improved and controlled membrane properties. ► Membranes were tested in direct contact membrane distillation (DCMD) setup. ► The performance of the developed membranes was comparable to commercial membranes.
Functionalized PVDF Nanofiber Membranes for Desalination by Direct Contact Membrane Distillation
International Journal of Materials Science and Engineering
The recent combination of nano particles and polymer in fabricating polymeric membranes has shown immerse potentials in developing composite membrane materials for practical applications including pollutant sequestration, reverse osmosis and membrane distillation. Here, this study reports the functionalization of Polyvinylidene fluoride electrospun nanofibers by the addition of different nano fillers (CuO, TiO 2 , SiO 2 and MOF-F300). The composite membrane materials were tested to determine their capability in the production of portable water from seawater by direct contact membrane distillation. Though the MOF composited membranes had the highest porosity, the flux shown by the TiO 2 composited membrane was greatest amongst all the composites (up to 7.2 kg/m 2 • h) at a temperature difference of 27 o C. The salt rejection for a 35 g/L NaCl solution was >99.9% for all membranes tested with permeate conductivities surpassing the drinking water standard. The attachment of nanofiber and support was significantly improved which is a key functionality in predicting long-term membrane durability, filler compatibility and flux stability of substrate composited membranes. This class of functionalized membranes materials are promising candidates for desalination and other membrane base applications.
Journal of Membrane Science, 2013
The main challenges for membranes used in membrane distillation (MD) are well-designed porous structure and hydrophobic surface property. Hydrophobic nanofiber membranes possess high hydrophobicity, high surface porosity and adjustable pore sizes and membrane thickness, which make them an attractive candidate as MD membrane. The current study aims to fabricate and optimize polyvinylidene fluoride (PVDF) nanofiber membranes for MD application. Scanning electron microscopy (SEM), capillary flow porometer, geniometer, a homemade setup for liquid entry pressure (LEP) measurement and direct contact MD (DCMD) setup were used to characterize the resultant nanofiber PVDF membranes. Polymer dope compositions, spinning parameters such as sprayer moving speed and chamber moisture were optimized to examine their effects on pore size distribution of the membranes. Inorganic additives were also added into the dope to improve the electro-spinability of diluted polymer dopes in order to further decrease membrane pore size. Meanwhile, a heat-press post-treatment was considered as a necessary step to improve fresh nanofiber membrane integrity, enhance water permeation flux and help prevent membrane pores from wetting in DCMD operation. The experiment confirmed that all the electrospun membranes exhibit a rough surface with high hydrophobicity ( 4 1351 water contact angle). The post-treated PVDF nanofiber membranes were able to present a steady water permeation flux of about 21 kg m À 2 h À 1 throughout the entire testing period of 15 h, using a 3.5 wt% NaCl solution as the feed under the feed and permeate inlet temperatures of 323 K and 293 K, respectively. This result was better than these of commercial PVDF membranes and the nanofiber PVDF-clay membrane reported in literature, suggesting the competency of PVDF nanofiber membranes for DCMD applications.
Dual-layered electrospun nanofibrous membranes for membrane distillation
Desalination, 2018
Dual-layered electrospun nanofibrous membranes (DL-ENMs) were prepared using the hydrophobic polymer polyvinylidene fluoride (PVDF) and the hydrophilic one polysulfone (PSF). The thickness of each layer was varied by changing the electrospinning time of each polymer solution maintaining the total electrospinning time at 3 h. The characteristics of the DL-ENMs and those of each layer were studied by means of different techniques and the results were compared to the single layer PVDF and PSF ENMs (i.e. SL-ENMs). The prepared DL-ENMs were tested in desalination by direct contact membrane distillation (DCMD) using different sodium chloride feed aqueous solutions. The DCMD permeate flux of the DL-ENMs was found to be higher than that of the PVDF SL-ENM and it increased with the decrease of the PVDF layer due not only to the reduction of the total thickness and to the increase of both the inter-fiber space and the void volume fraction, but also to the reduction of the path between the liquid/vapour interfaces formed at both side of the DL-ENMs. Compared to the proposed SL-ENMs in DCMD, it is better to use DL-ENMs adequately designed with hydrophobic and hydrophilic polymers than SL-ENM with only a hydrophobic polymer.
Desalination by Membrane Distillation Using Electrospun Nanofibrous Membranes, an Overview
Social Science Research Network, 2022
Fibrous membranes of poly(trimethyl hexamethylene terephthalamide) (PA6(3)T) were fabricated by electrospinning and rendered hydrophobic by applying a conformal coating of poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) using initiated chemical vapor deposition (iCVD). A set of iCVD-treated electrospun PA6(3)T fiber membranes with fiber diameters ranging from 0.25 to 1.8 μm were tested for desalination using the air gap membrane distillation configuration. Permeate fluxes of 2−11 kg/m 2 /h were observed for temperature differentials of 20−45°C between the feed stream and condenser plate, with rejections in excess of 99.98%. The liquid entry pressure was observed to increase dramatically, from 15 to 373 kPa with reduction in fiber diameter. Contrary to expectation, for a given feed temperature the permeate flux was observed to increase for membranes of decreasing fiber diameter. The results for permeate flux and salt rejection show that it is possible to construct membranes for membrane distillation even from intrinsically hydrophilic materials after surface modification by iCVD and that the fiber diameter is shown to play an important role on the membrane distillation performance in terms of permeate flux, salt rejection, and liquid entry pressure.
The major challenge for membrane distillation (MD) is membrane wetting resistance induced by pollutants in the feed solution. The proposed solution for this issue was to fabricate membranes with hydrophobic properties. Hydrophobic electrospun Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers membranes were produced for brine treatment using the direct contact membrane distillation (DCMD) technique. These nanofibers membranes were prepared from three different polymeric solution compositions to study the effect of solvent composition in the electrospinning process. Further, the effect of the polymer concentration was investigated by preparing polymeric solutions with three different polymer percentages: 6, 8, and 10%. All nanofibers membranes obtained from electrospinning were post-treated at varying temperatures. The effects of thickness, porosity, pore size, and LEP were studied. The hydrophobicity was determined by contact angle measurements, which were inves...
2017
Development of highly porous flat sheet polyvinylidene fluoride (PVDF) membranes for membrane distillation Salim Amer Alsaery With the increase of population every year, fresh water scarcity has rapidly increased and it is reaching a risky level, particularly in Africa and the Middle East. Desalination of seawater is an essential process for fresh water generation. One of the methods for desalination is membrane distillation (MD). MD process separates an aqueous liquid feed across a porous hydrophobic membrane to produce pure water via evaporation. Polyvinlidene fluoride (PVDF) membranes reinforced with a polyester fabric were fabricated as potential candidates for MD. Non-solvent induced phase separation coupled with steam treatment was used to prepare the PVDF membranes. A portion of the prepared membrane was coated with Teflon (AF2400) to increase its hydrophobicity. In the first study, the fabricated membranes were characterized using scanning electron microscopy and other techn...
2018
Membrane distillation has emerged as a highly efficient process in desalination of saline water. However, this process is affected by wetting of membrane pores and the low porous nature of membranes, causing low rate of water recovery. This study sought to mitigate these challenges by synthesizing highly porous and super-hydrophobic polyvinylidene fluoride (PVDF) nanofibre membranes modified with organically functionalized silica (SiO2) nanoparticles (NPs). The highly porous nanofibre membranes were synthesized using an electrospinning technique. The membranes were found to be mechanically strong and porous. Addition of the organically modified SiO2 NPs to the electrospinning solution resulted in the formation of super-hydrophobic membranes. These membranes were tested for their salt rejection capacity and water fluxes. They were found to reject the salt ions from water at high efficiencies (> 99%) with water fluxes ≈ 64 litres per hour indicating their capacity to produce high purity water in large quantities.
Fabrication of electrospun nanofibrous membranes for membrane distillation application
2012
Nanofibrous membranes of matrimide were successfully fabricated using electrospinning technique under optimized conditions. Nanofibrous membranes were found to be highly hydrophobic with high water contact angle of 130°. FESEM and pore size distribution analysis revealed the big pore size structure of electrospun membranes even greater than 2µm and the pore size distribution is found to be narrow. Flat sheet matrimide membranes were fabricated via casting followed by phase separation.The morphology, Pore size distribution and water contact angle were compared with the electrospun membranes. Both membranes fabricated by electrospinning and phase separation techniques were subjected to membrane distillation (MD). Electrospun membranes showed high water vapour flux of 56 kg/m 2-h and it is very high compared to the casted membrane as well as most of the fabricated and commercially available highly hydrophobic membranes.
Polymers
Membrane distillation (MD) is an emerging technology for water recovery from hypersaline wastewater. Membrane scaling and wetting are the drawbacks that prevent the widespread implementation of the MD process. In this study, coaxially electrospun polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP) nanofibrous membranes were fabricated with re-entrant architecture and enhanced hydrophobicity/omniphobicity. The multiscale roughness was constructed by incorporating Al2O3 nanoparticles and 1H, 1H, 2H, 2H Perfluorodecyltriethoxysilane in the sheath solution. High resolution transmission electron microscopy (HR-TEM) could confirm the formation of the core-sheath nanofibrous membranes, which exhibited a water contact angle of ~142.5° and enhanced surface roughness. The membrane displayed a stable vapor flux of 12 L.m−2.h−1 (LMH) for a 7.0 wt.% NaCl feed solution and no loss in permeate quality or quantity. Long-term water recovery from 10.5 wt.% NaCl feed solution was determined t...