Effects of mixed solvents and PVDF types on performances of PVDF microporous membranes

Abstract

Polyvinylidene fluoride (PVDF) microporous flat membranes were cast with different kinds of PVDFs and four mixed solvents [trimethyl phosphate (TMP)-N,N-dimethylacetamide (DMAc), triethyl phosphate (TEP)-DMAc, tricresyl phosphate (TCP)-DMAc, and tri-nbutyl phosphate (TBP)-DMAc]. The effects of different commercial PVDFs (Solef V R 1015, FR 904, Kynar 761, Kynar 741, Kynar 2801) on membrane morphologies and membrane performances of PVDF/TEP-DMAc/PEG200 system were investigated. The membrane morphologies were examined by scanning electron microscopy (SEM). The membrane performances in terms of pure water flux, rejection, porosity, and mean pore radius were measured. The membrane had the high flux of 143.0 AE 0.9 L m À2 h À1 when the content of TMP in the TMP-DMAc mixed solvent reached 60 wt %, which was 2.89 times that of the membrane cast with DMAc as single solvent and was 3.36 times that of the membrane cast with TMP as single solvent. Using mixed solvent with different solvent solubility parameters, different morphologies of PVDF microporous membranes were obtained. TMP-DMAc mixed solvent and TEP-DMAc mixed solvent indicated the stronger solvent power to PVDF due to the lower solubility parameter difference of 1.45 MPa 1/2 and the prepared membranes showed the faster precipitation rate and the higher flux. The less macrovoids of the membrane prepared with TEP (60 wt %)-DMAc (40 wt %) as mixed solvent contributed to the higher elongation ratio of 96.61% AE 0.41%. Therefore, using TEP(60 wt %)-DMAc (40 wt %) as mixed solvent, the casting solution had the better solvent power to PVDF, and the membrane possessed the excellent mechanical property. The microporous membranes prepared from casting solutions with different commercial PVDFs exhibited similar morphology, but the water flux increased with the increment of polymer solution viscosity.

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

“…Apart from the aforementioned investigations, improving PVDF membrane performance from material development aspect has become another research focal point [7]. The research efforts on this front have mainly focused on three approaches: (i) the potential use of a variety of additives or mixed-solvent in the dope solution [8][9][10], (ii) development of smart membrane architecture, for instance, composite and nano-composite membranes [11][12][13][14] Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/memsci and (iii) synthesizing novel PVDF-based copolymer with enhanced properties [2]. In terms of the 3rd strategies of PVDF-based copolymer synthesis, one example is the synthesis of PVDF-TFE, which showed better mechanical and hydrophobic properties over PVDF membrane and has better performance in DCMD configuration [15].…”

A poly(sulfobetaine) hollow fiber ultrafiltration membrane for the treatment of oily wastewater

“…(2015) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] www.deswater.com doi: 10.1080/19443994.2015.1042056 wastewater [3]. UF membrane can remove essentially all free and dispersed oil from wastewater, and the permeate is consistently able to meet Oil and Gas Standards for discharge [2][3][4][5][6].…”

“…UF membrane can remove essentially all free and dispersed oil from wastewater, and the permeate is consistently able to meet Oil and Gas Standards for discharge [2][3][4][5][6]. The polymers such as poly(vinylidene fluoride) (PVDF) and poly(ether sulfones) (PES)/polysulfone (PSF) have been recognized as the most attractive polymers in membrane industry due to their extraordinary mechanical property, high chemical resistance, and good thermal stability [7][8][9]. But these membranes have been limited in the treatment unit of oily wastewater by economic obstacles because of the severe membrane fouling [8].…”

Preparation and Characterization of Polymeric-Hybrid PES/TiO2 Hollow Fiber Membranes for Potential Applications in Water Treatment

“…In addition, it affects the solvent/non-solvent exchange during coagulation and, therefore, the hollow fiber final morphology [44]. In the first group of experiments, polymeric dopes were prepared while keeping constant PES and PEG 400 concentrations, in order to compare the effect of the three additives (PVP K-17, PVP K-30, and Plu F-127).…”