Influence of the Zeolite ZSM-22 Precursor on a UF-PES Selective Substrate Layer for Salts Rejection

Abstract

Fabrication of the ZSM-22/Polyethersulfone (ZSM-22/PES) membranes as selective salt filters represent a growing membrane technological area in separation with the potential of high economic reward based on its low energy requirements. The incorporation of ZSM-22 zeolite material as additives into the PES polymer matrix has the prospective advantage of combining both the zeolite and polymer features while overcoming the limitations associated with both materials. This work investigated the influence of the nature of the silica precursor on ZSM-22 zeolite hydrothermally synthesised using colloidal (C60) and fumed (C60) silica to Si/Al of 60. The successful synthesis of the highly crystalline zeolitic materials was confirmed through XRD, FTIR, and SEM with EDX. The ZSM-22 additives were directly dispersed into a PES polymeric matrix to form a casting solution for the preparation of the ZSM-22/PES selective substrate layers via a phase inversion method for salts rejection. The polymeric PES was selected as an organic network in which the content of the ZSM-22 zeolite (ranging between 0 and 1.0 wt.%), was obtained and characterised by XRD, FTIR, and SEM analysis, as well as water contact angle (WCA) measurement and dead-end filtration cell. The phase inversion preparation method has induced the resulting ZSM-22/PES NF substrates anisotropy, as attributed to a high water flux to the above 700 L·m^-2·h^-1; high selectivity and rejection of salts to above 80% is revealed by the obtained results. The materials also exhibited improved antifouling behavior to above 70% flux recovery ratios. As such, the nature of the silica precursor influences ZSM-22 zeolite synthesis as a potential additive in the PES polymer matrix and led to the enhanced performance of the pure PES ultrafiltration membrane.

Keywords: membrane preparation; membrane separation; nanocomposite membranes; nanofiltration membrane; polymeric membranes; zeolite ZSM-22 materials.

Figure 1

X-ray diffraction patterns of nanofiltration membranes prepared through a phase inversion method to a nominal wt.% loadings of 0, 0.1, 0.3, 0.5, 0.75, and 1.0 using ZSM-22: (a) C60-ZSM-22/PES and (b) F60-ZSM-22/PES with zeolite as additives.

Figure 2

ATR-FTIR spectra of nanofiltration membranes prepared through a phase inversion method to nominal wt.% loadings of 0, 0.1, 0.3, 0.5, 0.75, and 1.0 using ZSM-22: (a) C60-ZSM-22/PES and (b) F60-ZSM-22/PES with zeolite as additives.

Figure 3

SEM surface micrographs of C60-ZSM-22/PES membrane materials prepared using C60-ZSM-22 as zeolite additives: (a) PES, (b) 0.1 wt.% C60-ZSM-22/PES, (c) 0.3 wt.% C60-ZSM-22/PES, (d) 0.5 wt.% C60-ZSM-22/PES, (e) 0.75 wt.% C60-ZSM-22/PES, and (f) 1.0 wt.% C60-ZSM-22/PES via phase inversion.

Figure 4

SEM surface micrographs of F60-ZSM-22/PES nanofiltration membrane materials prepared using F60-ZSM-22 as zeolite additives: (a) PES, (b) 0.1 wt.% F60-ZSM-22/PES, (c) 0.3 wt.% F60-ZSM-22/PES, (d) 0.5 wt.% F60-ZSM-22/PES, (e) 0.75 wt.% F60-ZSM-22/PES, and (f) 1.0 wt.% F60-ZSM-22/PES via phase inversion.

Figure 5

SEM cross-sectional of C60-ZSM-22/PES membrane materials prepared using C60-ZSM-22 as zeolite additives: (a) PES, (b) 0.1 wt.% C60-ZSM-22/PES, (c) 0.3 wt.% C60-ZSM-22/PES, (d) 0.5 wt.% C60-ZSM-22/PES, (e) 0.75 wt.% C60-ZSM-22/PES, and (f) 1.0 wt.% C60-ZSM-22/PES via phase inversion.

Figure 6

SEM cross-sectional of F60-ZSM-22/PES membrane materials prepared using F60-ZSM-22 as zeolite additives: (a) PES, (b) 0.1 wt.% F60-ZSM-22/PES, (c) 0.3 wt.% F60-ZSM-22/PES, (d) 0.5 wt.% F60-ZSM-22/PES, (e) 0.75 wt.% F60-ZSM-22/PES, and (f) 1.0 wt.% F60-ZSM-22/PES via phase inversion.

Figure 7

EDX spectra of (a) ZSM-22, (b) PES, (c) 0.3 wt.% C60-ZSM-22/PES, (d) 0.3 wt.% F60-ZSM-22/PES, (e) 1.0 wt.% C60-ZSM-22/PES, and (f) 1.0 wt.% F60-ZSM-22/PES membrane materials.

Figure 8

Contact angle measurements of nanofiltration membranes prepared via phase inversion to nominal wt.% loadings of 0, 0.1, 0.3, 0.5, 0.75, and 1.0 using ZSM-22: (a) C60-ZSM-22/PES and (b) F60-ZSM-22/PES as zeolite additives.

Figure 9

Pure water flux analysis of nanofiltration membranes prepared via phase inversion to nominal wt.% loadings of 0, 0.1, 0.3, 0.5, 0.75, and 1.0 using ZSM-22 zeolite as nanoadditives: (a) C60-ZSM-22/PES and (b) F60-ZSM-22/PES.

Figure 10

Antifouling analysis of nanofiltration membranes prepared via phase inversion to nominal wt.% loadings of 0, 0.1, 0.3, 0.5, 0.75, and 1.0 using ZSM-22 zeolite as nanoadditives: (a) C60-ZSM-22/PES and (b) F60-ZSM-22/PES.

Figure 11

Flux recovery ratios analysis of nanofiltration membranes prepared via phase inversion to nominal wt.% loadings of 0, 0.1, 0.3, 0.5, 0.75, and 1.0 using ZSM-22 zeolite as nanoadditives: (a) C60-ZSM-22/PES and (b) F60-ZSM-22/PES.

Figure 12

Total fouling analysis of nanofiltration membranes prepared via phase inversion to nominal wt.% loadings of 0, 0.1, 0.3, 0.5, 0.75, and 1.0 using ZSM-22 zeolite as nanoadditives: (a) C60-ZSM-22/PES and (b) F60-ZSM-22/PES.

Figure 13

Reversible fouling analysis of nanofiltration membranes prepared via phase inversion to nominal wt.% loadings of 0, 0.1, 0.3, 0.5, 0.75, and 1.0 using ZSM-22 zeolite as nanoadditives: (a) C60-ZSM-22/PES and (b) F60-ZSM-22/PES.

Figure 14

Irreversible fouling analysis of nanofiltration membranes prepared via phase inversion to nominal wt.% loadings of 0, 0.1, 0.3, 0.5, 0.75, and 1.0 using ZSM-22 zeolite as nanoadditives: (a) C60-ZSM-22/PES and (b) F60-ZSM-22/PES.

Figure 15

Salt rejection analysis of nanofiltration membranes prepared via phase inversion to nominal wt.% loadings of 0, 0.1, 0.3, 0.5, 0.75, and 1.0 using ZSM-22 zeolite as nanoadditives: (a) C60-ZSM-22/PES and (b) F60-ZSM-22/PES.