Characterizations of Electrospun PVDF-Based Mixed Matrix Membranes with Nanomaterial Additives

Abstract

Water scarcity poses a formidable challenge around the world, especially in arid regions where limited availability of freshwater resources threatens both human well-being and ecosystem sustainability. Membrane-based desalination technologies offer a viable solution to address this issue by providing access to clean water. This work ultimately aims to develop a novel permselective polymeric membrane material to be employed in an electrochemical desalination system. This part of the study addresses the optimization, preparation, and characterization of a polyvinylidene difluoride (PVDF) polymeric membrane using the electrospinning technique. The membranes produced in this work were fabricated under specific operational, environmental, and material parameters. Five different additives and nano-additives, i.e., graphene oxide (GO), carbon nanotubes (CNTs), zinc oxide (ZnO), activated carbon (AC), and a zeolitic imidazolate metal-organic framework (ZIF-8), were used to modify the functionality and selectivity of the prepared PVDF membranes. Each membrane was synthesized at two different levels of additive composition, i.e., 0.18 wt.% and 0.45 wt.% of the entire PVDF polymeric solution. The physiochemical properties of the prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), zeta potential, contact angle, conductivity, porosity, and pore size distribution. Based on findings of this study, PVDF/GO membrane exhibited superior results, with an electrical conductivity of 5.611 mS/cm, an average pore size of 2.086 µm, and a surface charge of -38.33 mV.

Keywords: PVDF; electrospinning; metal–organic frameworks; nano-additives.

Figure 1

SEM images of the PVDF membranes fabricated in this study: (a) 20 mL/h, 9:1 DMF/AC, (b) 10 mL/h, 9:1 DMF/AC, (c) 5 mL/h 7:3 DMF/AC, (d) 3 mL/h, 7:3 DMF/AC (e) 2 mL/h, 7:3 DMF/AC, and (f) 5 mL/h, 6:4 DMF/AC.

Figure 2

SEM images for PVDF membranes with different additives (base case conditions are those of case F in Table 2): (a) Pure PVDF, (b) PVDF/GO, (c) PVDF/AC, (d) PVDF/MOFs, (e) PVDF/CNTs, (f) PVDF/ZnO, and (g–j) EDX and color mapping images for PVDF/MOFs and PVDF/ZnO, respectively.

Figure 3

Pore size distribution for the prepared membranes: (a) PVDF membranes, (b) AC/PVDF, (c) CNTs/PVDF, (d) GO/PVDF, (e) ZnO/PVDF, and (f) MOFs/PVDF.

Figure 4

Porosity results for mixed matrix membrane with different additives.

Figure 5

FTIR spectra for the different prepared membranes.

Figure 6

Zeta potential measurements for the different synthesized membranes.

Figure 7

Contact angle for the different synthesized membranes.