Two‐stage phase separation of cellulose acetate membranes modified with plasma‐treated natural zeolite: Response surface modeling

Abstract

Cellulose acetate (CA) microfiltration membranes were prepared by two‐stage vapor‐induced phase separation (VIPS) and immersion precipitation. To improve the hydrophilicity and permeability of the membranes at low operating pressures, plasma‐treated natural zeolite was incorporated into the membranes. A response surface methodology based on the three‐level central composite design (CCD) was used to model and optimize the casting solution composition of the membranes with the aim of maximizing membranes permeability. Three independent variables for CCD optimization were concentration of CA, polyvinylpyrrolidone (PVP) pore former, and plasma‐treated zeolite additive. The results showed that a second‐order polynomial model could properly predict the response (pure water flux) at any input variable values with a satisfying determination coefficient (R2) of 0.954. Also, analysis of variance (ANOVA) confirmed the adequacy of the obtained model. The permeability of the prepared membranes increased by increasing zeolite loading from 0.10 to 0.50 wt%, which was related to the membranes morphology and porosity and confirmed by scanning electron microscopy (SEM) images. Pure water flux of the membranes decreased by increasing CA concentration while an optimum PVP amount was required to reach the maximum flux. The result of the bubble point analysis well matched with surface SEM images of the membranes and permeability trend predicted by CCD model. Also, the prepared CA membranes with different compositions showed no toxicity for mouse L929 fibroblast, which indicated their nontoxic and biocompatible nature.

Fabrication of the PES Membrane Embedded with Plasma-Modified Zeolite at Different O2 Pressures

“…The band at 445 cm enhanced the severity of these bands. 36,40,41 The effect of the gas pressure level was also reported by another study proposed by Pandiyaraj and Selvarajan, 42 where the hydrophilicity increment was observed by increasing the gas pressure level. They theorized that the increased penetration depth and plasma species velocity are derived from the pressure enhancement.…”

“…The new Si–OH–Al bonds’ formation during plasma treatment is demonstrated by the emergence of new bands in this region. It is also evident that raising the oxygen gas pressure during plasma treatment has enhanced the severity of these bands. ,, The effect of the gas pressure level was also reported by another study proposed by Pandiyaraj and Selvarajan, where the hydrophilicity increment was observed by increasing the gas pressure level. They theorized that the increased penetration depth and plasma species velocity are derived from the pressure enhancement.…”

“…Prior to discharge exertion, the tube was evacuated, and in this study, the plasma-forming gas used was O 2 (99.99% in purity). The injection of O 2 into the reactor was carried out three times at pressures of 1.0, 0.5, and 0.1 Torr (133.32, 66.66, and 13.33 Pa, respectively) in the duration of the 30 min plasma treatment …”

“…Thanks to the porosity and morphology changes, the enhancement of the permeability of these membranes was achieved by increasing the zeolite concentration from 0.10 to 0.50 wt %. 36 Meanwhile, the fabrication of polyamide RO membranes using the interfacial polymerization process and modification with plasma-treated natural clinoptilolite is another important study, in which the optimum fouling recovery ratio (88%) and water flux enhancement (39%) were obtained by the membrane possessing 0.01 wt % clinoptilolite treated with 1.0 Torr oxygen plasma gas. 37 Although the effect of plasma treatment as a modification method in different zeolite amounts was indicated in these studies, the main purpose of this work is related to investigating the impact of the pressure of plasma gas on the fouling resistance and separation performance.…”

“…The investigation regarding the application of plasma-treated natural zeolite in water treatment can be attributed to the modification of cellulose acetate membranes. Thanks to the porosity and morphology changes, the enhancement of the permeability of these membranes was achieved by increasing the zeolite concentration from 0.10 to 0.50 wt % . Meanwhile, the fabrication of polyamide RO membranes using the interfacial polymerization process and modification with plasma-treated natural clinoptilolite is another important study, in which the optimum fouling recovery ratio (88%) and water flux enhancement (39%) were obtained by the membrane possessing 0.01 wt % clinoptilolite treated with 1.0 Torr oxygen plasma gas .…”