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

Abstract

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.

Association of Polyethylene Glycol Solubility with Emerging Membrane Technologies, Wastewater Treatment, and Desalination

“…Combined effects of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and the concentrations of the additive PEG 10000 were studied by using a statistical approach, and the optimized membrane achieved salt rejection of 99.5% in the DCMD of 0.1 M NaCl solution at 65°C [36]. Two pore-forming additives PEG and LiCl both at 4 wt% were used in the fabrication of hydrophobic flat sheet and hollow fiber PVDF and PVDF-co-chlorotrifluoroethylene (PVDF-CTFE) membranes for membrane distillation [37,38]. The effect of mass ratio of PEG and LiCl was further investigated for making PVDF-CTFE membranes for MD [39].…”

Electrospun porous poly(tetrafluoroethylene-co-hexafluoropropylene-co-vinylidene fluoride) membranes for membrane distillation

“…3,9,10 To date, polypropylene (PP), PVDF, and poly(tetrauoroethylene) (PTFE) are widely employed because of their intrinsic hydrophobicity. 4 In addition, many novel polymers, including polystyrene, 11,12 polyazole, 13 as well as copolymer of PVDF and PTFE, 4, [14][15][16][17][18][19][20] have been used to prepare membranes for MD to achieve better performance. Among them, the most promising material is the partially uorinated copolymer of PVDF and PTFE.…”

Enhancing the Antifouling Properties of Poly(vinylidene fluoride) (PVDF) Membrane through a Novel Blending and Surface-Grafting Modification Approach

“…This may be attributed to the lower compatibility between P(VDF- co -CTFE) and PVDF as compared to that among PVDF itself. 31,32 During the process of membrane surface modifications, the membrane pores may be easily blocked or reduced. 33 Although no obvious pores can be found for G1–G4, with the addition of PVP, the membrane thickness and pore of G5–G8 were increased to almost twice that of the membrane without PVP.…”