Optimization of PES-based Hollow fiber membranes incorporating MgO-modified activated carbon via response surface methodology for enhanced pure water permeability

Abstract

This research aims to optimize the fabrication of polyethersulfone (PES)-based composite hollow fiber membranes via phase inversion. For this purpose, MgO-modified activated carbon (AC) particles were synthesized and incorporated into the polymer matrix. High-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were utilized to examine the morphological and chemical properties of the AC-MgO particles. To optimize the fabrication process, the effects of four key parameters: AC-MgO particle concentration (0.09-0.36 wt%), bore fluid flow rate (3.5-9.5 ml/min), dope solution flow rate (1.5-3.5 ml/min), and air gap distance (2-42 cm), were analyzed using response surface methodology (RSM) with a central composite design. The performance of the membranes was assessed in terms of pure water permeability (PWP). The results of experimental tests conducted under the optimal conditions obtained using the RSM method for particle concentration and process parameters were in close agreement with the model predictions, confirming the model's accuracy. Moreover, it was found that particle concentration and air gap distance significantly influenced membrane performance. The AC-MgO particles significantly enhanced membrane properties by reducing the water contact angle, indicating improved hydrophilicity, and promoting the formation of a more porous membrane structure.

Keywords: AC-MgO particles; Hollow fiber membrane; Morphology; RSM; Spinning parameters.

Fig. 1

Schematic of the hollow fiber membrane preparation setup; (1) dope solution, (2) bore fluid, (3 and 4) syringe pumps, (5) spinneret, (6) air gap, (7) guide rollers, (8) collector, and (9) coagulation bath.

Fig. 2

Schematic of the PWP experimental setup (1) feed, (2) peristaltic pump, (3) pressure gauge, and (4) hollow fiber membrane.

Fig. 3

X-ray diffraction patterns of pure MgO, AC, and AC-MgO particles.

Fig. 4

SEM images of (a) AC powder, (b) AC-10 wt% MgO nanocomposites, (c) Fig. (b) at higher magnification, (d) EDS spectroscopy and EDS mapping elements of carbon, magnesium and oxygen of the AC–MgO-10% nanocomposite.

Fig. 5

(a) TEM image showing the morphology and dispersion of AC-10 wt% MgO nanocomposites; (b) SAED pattern confirming the crystalline structure of MgO nanoparticles within the composite; (c) HR-TEM image revealing the lattice fringes and detailed nanostructure of the AC-10 wt% MgO nanocomposites.

Fig. 6

Surface roughness analysis of PES membranes containing (a) 0 wt% and (b) 0.354 wt% AC-MgO particles.

Fig. 7

Water contact angle for PES based hollow fiber membranes.

Fig. 8

Comparison between predicted and measured pure water permeability values.

Fig. 9

(a) Normal probability plots of studentized residuals for pure water permeability (PWP), and (b) variation of residuals versus predicted PWP values.

Fig. 10

Variation of pure water permeability (PWP) with (a) air gap and particle concentration in solution (b) bore fluid rate and dope solution rate, (c) air gap and dope solution rate, (d) particle concentration and dope solution rate, (e) air gap and bore fluid rate, and (f) particle concentration and bore fluid rate (The plots generated using Design-Expert software, version 13.0.5.0 (Stat-Ease, Inc.). For more details, visit https://www.statease.com/software/design-expert/).

Fig. 11

Contour plot of pure water permeability variation with (a) particle concentration in solution and air gap, (b) bore fluid rate and dope solution rate, (c) air gap and dope solution rate, (d) particle concentration and dope solution rate, (e) air gap and bore fluid rate, and (f) particle concentration and bore fluid rate (The plots generated using Design-Expert software, version 13.0.5.0 (Stat-Ease, Inc.). For more details, visit https://www.statease.com/software/design-expert/).

Fig. 12

SEM micrographs of the hollow fiber cross-sections prepared with varying concentrations of AC-MgO particles in the dope solution: (a) 0%, (b) 0.18%, and (c) 0.36% wt.

Fig. 13

SEM micrograph of hollow fiber cross-sections for various air gap distance. (a) 2 cm, (b) 22 cm, (c) 42 cm, (d) 12 cm, and (e) 32 cm.

Fig. 14

Effect of the dope solution flow rate on hollow fiber pore morphology. (a) 2 ml/min, (b) 3 ml/min, (c) 1.5 ml/min, and (d) 2.5 ml/min.

Fig. 15

Effect of the bore fluid flow rate on morphology of hollow fiber cross section: (a) 5 ml/min, (b) 8 ml/min, (c) 6.5 ml/min, and (d) 9.5 ml/min.