Effect of polyethylene glycol (PEG) as an additive on the fabrication of polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) asymmetric microporous hollow fiber membranes

Wongchitphimon, Sunee; Wang, Rong; Jiraratananon, Ratana; Shi, Lei; Loh, Chun Heng

doi:10.1016/j.memsci.2010.12.008

Cited by 178 publications

(109 citation statements)

References 28 publications

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“…Meanwhile, mixed additives have been a recent trend for polymer membrane preparation due to the synergistic effect among different additives. Polyethylene glycol (PEG) is a commonly used pore-former for membrane preparation, and the PVDF membrane prepared with PEG normally possesses a macrovoid structure with high porosity owing to the instantaneous phase inversion process induced by PEG [29][30][31][32][33]. LiCl is another frequently-used additive, which tends to enhance the viscosity of the casting solution.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, macrovoids were suppressed and the membrane with excellent interconnectivity and porosity can be gained, however at the expense of decline in mechanical strength [19,33,34]. As such, attempts were made to use PEG/LiCl mixed additives for membrane preparation in order to synergize the advantages of both additives [32,35,36]. Nonetheless, as a crucial factor to membrane properties and performance, the PEG/LiCl mass ratio in casting solution has not been investigated systematically and its impacts on the resultant membranes have hardly been reported.…”

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: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…Furthermore, it was observed that the size of the macrovoids expanded along with the increasing PEG molecular weight, which was in good agreement with previous studies. 32,33 So it is safe to say that L-L demixing dominated the phase inversion process for all the casting solution. However, the role of S-L demixing was increasingly important as the molecular weight increased due to the lower phase inversion rate as discussed for membrane surface.…”

Section: Membrane Morphology By Semmentioning

confidence: 99%

“…On one hand, the addition of PEG was reported to decrease the hydrophobicity of membrane. 45,46 On the other hand, the crystallites formed on the membrane surface due to the high dosage or molecular weight increased the membrane surface roughness, and thus leading to a higher hydrophobicity. 47,48 These two contrary effect induced by PEGs with different molecular weight or dosage worked together to the hydrophobic of the resultant membranes.…”

Section: Membrane Hydrophobicitymentioning

confidence: 99%

Interconnected PVDF-CTFE hydrophobic membranes for MD desalination: effect of PEGs on phase inversion process

et al. 2016

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In this work, poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) was used for hydrophobic membrane preparation by the non-solvent induced phase inversion (NIPS) technique. The effects of poly(ethylene glycol) (PEG) molecular weight and dosage were investigated in terms of the membrane morphology, contact angle, surface free energy, and membrane pore structure for both surface pores and overall pores. All membranes possessed a typical liquid-liquid demixing asymmetric structure and the contact angles were higher than 85. Furthermore, increasing the PEG molecular weight and dosage significantly altered the membrane pore structure and surface roughness as a result of the variation of the phase inversion process. The solid-liquid demixing was responsible for the variation of membrane morphology, pore structure, hydrophobicity, and DCMD performance as PEGs with higher molecular weight or dosage were added. The PVDF-CTFE membranes were suitable for MD application owing to their high hydrophobicity, small pore size with narrow pore distribution, high DCMD performance, especially the interconnected pore structure. The membrane containing 5 wt% PEG-400 was evidenced to be the optimal one for the MD process, mainly according to the high interconnected pore structure which provide more passages for vapour transfer. The permeate flux was 17.98 kg (m À2 h À1) with a conductivity as low as 7 mS cm À1 at the temperature difference of 30 C. In addition, an excellent performance sustainability was observed including a relatively steady permeate flux and conductivity during the 360 h continuous DCMD operation.

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“…They found that the membrane prepared with mixed additives showed longer finger-like cavities, ultra-thin skins, a narrow pore size distribution and porous network sponge-like structure, high porosity and good hydrophobicity owing to the synergistic effects of LiCl and PEG-1500. Wongchitphimon et al (2011) also investigated the effect of LiCl/PEG-6000 mixed additives on PVDF-HFP membrane preparation. Application of mixed additives has been an effective method to obtain ideal membranes, and mixed additives using different types of common additives have been widely studied in the membrane preparation field.…”

Section: Introductionmentioning

confidence: 99%

Effect of non-solvent additives on the morphology, pore structure, and direct contact membrane distillation performance of PVDF-CTFE hydrophobic membranes

Zheng

Zhang

et al. 2016

Journal of Environmental Sciences

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Four common types of additives for polymer membrane preparation including organic macromolecule and micromolecule additives, inorganic salts and acids, and the strong non-solvent H 2 O were used to prepare poly (vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) hydrophobic flat-sheet membranes. Membrane properties including morphology, porosity, hydrophobicity, pore size and pore distribution were investigated, and the permeability was evaluated via direct contact membrane distillation (DCMD) of 3.5 g/L NaCl solution in a DCMD configuration. Both inorganic and organic micromolecule additives were found to slightly influence membrane hydrophobicity. Polyethylene glycol (PEG), organic acids, LiCl, MgCl 2 , and LiCl/H 2 O mixtures were proved to be effective additives to PVDF-CTFE membranes due to their pore-controlling effects and the capacity to improve the properties and performance of the resultant membranes. The occurrence of a pre-gelation process showed that when organic and inorganic micromolecules were added to PVDF-CTFE solution, the resultant membranes presented a high interconnectivity structure. The membrane prepared with dibutyl phthalate (DBP) showed a nonporous surface and symmetrical cross-section. When H 2 O and LiCl/H 2 O mixtures were also used as additives, they were beneficial for solid-liquid demixing, especially when LiCl/H 2 O mixed additives were used. The membrane prepared with 5% LiCl + 2% H 2 O achieved a flux of 24.53 kg/(m 2 ·hr) with 99.98% salt rejection. This study is expected to offer a reference not only for PVDF-CTFE membrane preparation but also for other polymer membranes.

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Effect of polyethylene glycol (PEG) as an additive on the fabrication of polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) asymmetric microporous hollow fiber membranes

Cited by 178 publications

References 28 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

Interconnected PVDF-CTFE hydrophobic membranes for MD desalination: effect of PEGs on phase inversion process

Effect of non-solvent additives on the morphology, pore structure, and direct contact membrane distillation performance of PVDF-CTFE hydrophobic membranes

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