Fabrication of hydrophobic flat sheet and hollow fiber membranes from PVDF and PVDF-CTFE for membrane distillation

Wang, Jun; Zheng, Liping; Wu, Zhenjun; Zhang, Yong; Zhang, Xiaohui

doi:10.1016/j.memsci.2015.09.024

Cited by 73 publications

(38 citation statements)

References 35 publications

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“…Meanwhile, the particulate packed pore structure with high interconnectivity was shown. Similar morphology was reported in our previous work, in which a comparison between hydrophobic membranes by PVDF and PVDF-CTFE was conducted with/without additives [27]. In that work, it also demonstrated that the S-L demixing process showed more influence when additives was added as compared to the membrane without additives.…”

Section: Membrane Morphology Of M5supporting

confidence: 88%

“…1, which was same as the previous work [27] by adding a computer automatic recording unit. A super thermostat bath and a cryostat were used for temperature controlling.…”

Section: Direct Contact Membrane Distillation (Dcmd) Testmentioning

confidence: 99%

“…To our best knowledge, although numerous efforts have been dedicated to applying PVDF-CTFE copolymer to membrane preparation, its potential in hydrophobic membrane preparation was overlooked. Thus, PVDF-CTFE copolymer was carefully compared with PVDF from physicochemical property to phase diagram, as well as the hydrophobic membrane properties and DCMD performance in our previous work [27]. PVDF-CTFE showed excellent properties for hydrophobic membrane preparation and MD desalination application due to the ideal structure and DCMD performance.…”

Section: Introductionmentioning

confidence: 99%

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Preparation of PVDF-CTFE hydrophobic membranes for MD application: Effect of LiCl-based mixed additives

Zheng

Wei

et al. 2016

Journal of Membrane Science

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a b s t r a c tHydrophobic flat-sheet membranes were prepared by poly (vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) via the non-solvent induced phase separation (NIPS) process for membrane distillation (MD) application. Different types of LiCl-based mixed additives were applied to investigate their effects on membrane properties and MD performance. The membranes were evaluated in terms of membrane morphology, pore size and distribution, porosity, surface roughness, hydrophobicity, as well as the direct contact membrane distillation (DCMD) performance. Clear evidences were obtained that the mixed additives altered the phase inversion process, which resulted in the variation in membrane morphology, structure, properties and performance. The mass ratio of PEG/LiCl ranging from 5:0 to 0:5 was comprehensively investigated to study the synergistic effects of two additives on PVDF-CTFE membranes. The membrane M5 (PEG:LiCl ¼1:1, total content 8 wt% ) showed optimal properties and MD performance for combining the structure of higher hydrophobicity and pore interconnectivity, small pore size and narrow pore size distribution. The addition of LiCl to PEG-containing solutions benefited the solid-liquid demixing process, which increased the hydrophobicity, porosity, pore interconnectivity, and MD performance of the resultant membranes. While added PEG to LiCl-containing solutions showed slightly influences. Furthermore, it was also found that PVP/LiCl and glycerol/LiCl were not suitable for hydrophobic membrane preparation as they strikingly reduced membrane hydrophobicity. While H 3 PO 4 and H 2 O were confirmed suitable to mix with LiCl for hydrophobic PVDF-CTFE membrane preparation.

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Section: Membrane Morphology Of M5supporting

confidence: 88%

“…1, which was same as the previous work [27] by adding a computer automatic recording unit. A super thermostat bath and a cryostat were used for temperature controlling.…”

Section: Direct Contact Membrane Distillation (Dcmd) Testmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Preparation of PVDF-CTFE hydrophobic membranes for MD application: Effect of LiCl-based mixed additives

Zheng

Wei

et al. 2016

Journal of Membrane Science

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“…In the MD process, a hydrophobic microporous membrane is required, which acts as the separation medium. Currently, hydrophobic microporous membranes have been successfully prepared by the vacuum MD (VMD) process, and these include polyvinylidene fluoride (PVDF), polypropylene (PP) and polytetrafluoroethylene (PTFE), as well as PVDF copolymers such as polyvinylidene fluoride‐co‐hexafluoropropylene (PVDF‐HFP) and PVDF‐co‐trifluorochloroethylene (PVDF‐CTFE) . Of these, PVDF membranes are frequently used as hydrophobic separation membranes for MD because of their excellent hydrophobicity, chemical resistance and membrane‐forming processability.…”

Section: Introductionmentioning

confidence: 99%

Dye removal using hydrophobic polyvinylidene fluoride hollow fibre composite membrane by vacuum membrane distillation

Feng

Shi

et al. 2019

Coloration Technology

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Hydrophobic polyvinylidene fluoride (PVDF) hollow fibre composite membranes were prepared by the dilute solution coating process to build a special surface structure that was similar to the dual micro‐nano structure on the lotus leaf. Poly(vinylidene fluoride‐co‐hexafluoropropene) was chosen as the hydrophobic polymer candidate in dilute solution. Membrane morphology and surface hydrophobicity were evaluated by scanning electron microscopy and dynamic water contact angle measurement. The prepared PVDF hollow fibre membranes were employed to separate dyes (Congo Red and Methylene Blue) from water by vacuum membrane distillation. The effects of operational conditions (feed temperature, vacuum pressure and feed flow rate) on the vacuum membrane distillation performance of different PVDF membranes were investigated. The results indicated that the water contact angle values of PVDF composite membrane surfaces improved from 93.6° to 130.8°, which was mainly attributed to the formation of micro‐nano rods. This structure was similar to the dual micro‐nano structure on the lotus leaf. Under test feed temperature, vacuum pressure and feed flow rate conditions, the dye rejection rate of Congo Red and Methylene Blue by the hydrophobic PVDF hollow fibre membrane remained above 99.5% and 99%, which was higher than that of the pristine PVDF membrane (99% and 98%, respectively). In addition, the hydrophobic PVDF hollow fibre composite membrane showed higher permeation flux under different conditions compared with the pristine PVDF membrane, which was attributed to membrane surface hydrophobicity and the electrostatic interactions between dyes and the PVDF membrane surface.

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“…All membranes showed open porous structure with crystals in the surface, which presented a similar microstructure as the lotus leaf (for M1−M6) and the electrospun nanofiber membrane (for M7− M9), because PVDF-CTFE has a higher crystallization tendency as confirmed in our previous work. 44 The crystals and particles aggregate pore structure became more significant as the exposure duration increased especially as can be found in the inserted images in Figure 2. The membrane 3-D surface morphology and membrane surface depth distribution image recorded by AFM are presented in Figure 3 and Figure S2, respectively.…”

Section: ■ Results and Discussionmentioning

confidence: 84%

Preparation of Interconnected Biomimetic Poly(vinylidene fluoride-co-chlorotrifluoroethylene) Hydrophobic Membrane by Tuning the Two-Stage Phase Inversion Process

Zheng

Wang²,

et al. 2016

ACS Appl. Mater. Interfaces

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A facile strategy was applied for poly(vinylidene fluoride-cochlorotrifluoroethylene) (PVDF-CTFE) hydrophobic membrane preparation by tuning the two-stage phase inversion process. The exposure stage was found to benefit the solid−liquid demixing process (gelation/crystallization) induced by the solvent evaporation and the subsequent phase inversion induced by immersion benefit the liquid−liquid demixing. It was confirmed that the electrospun nanostructure-like biomimetic surface and interconnected pore structure can be expected by controlling the exposure duration, and 300 s was considered as the inflection point of exposure duration for PVDF-CTFE membrane through which a tremendous variation would show. The micro/ nanohierarchical structure in the membrane surface owing to the crystallization of PVDF-CTFE copolymer was responsible for the improvement of membrane roughness and hydrophobicity. Meanwhile, the interconnected pore structure in both the surface and the cross-section, which were formed because of the crystallization process, offers more mass transfer passages and enhances the permeate flux. The membrane then showed excellent MD performance with high permeate flux, high salt rejection, and relatively high stability during a 48 h continuous DCMD operation, according to the morphology, pore structure, and properties, which can be a substitute for hydrophobic membrane application.

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Fabrication of hydrophobic flat sheet and hollow fiber membranes from PVDF and PVDF-CTFE for membrane distillation

Cited by 73 publications

References 35 publications

Preparation of PVDF-CTFE hydrophobic membranes for MD application: Effect of LiCl-based mixed additives

Preparation of PVDF-CTFE hydrophobic membranes for MD application: Effect of LiCl-based mixed additives

Dye removal using hydrophobic polyvinylidene fluoride hollow fibre composite membrane by vacuum membrane distillation

Preparation of Interconnected Biomimetic Poly(vinylidene fluoride-co-chlorotrifluoroethylene) Hydrophobic Membrane by Tuning the Two-Stage Phase Inversion Process

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