Mixed Matrix Composite Membranes Research Articles

High-performance gas separation using mixed-matrix composite membranes containing graphene nanoplatelets

High-performance gas separation using mixed-matrix composite membranes containing graphene nanoplatelets

Synthesis of inorganic doped polyvinyl alcohol/hydroxypropyl methyl cellulose mixed matrix membrane for pervaporative separation of dimethyl carbonate/methanol mixtures

Inorganic loaded Polyvinyl Alcohol/Hydroxypropyl Methyl Cellulose (PVA/HPMC) mixed matrix composite membranes were synthesized by filling phosphomolybdic acid (PMA) into PVA/HPMC matrix. The obtained results indicate that the swelling degree of the PMA loaded PVA/HPMC blend membranes enhances with excess PMA amount or high feed methanol (MeOH) concentration. The effects of HPMC ratio in blend membranes, PMA content, feed methanol concentration and operation temperature on separation success of pervaporation (PV) were also examined. The consequences demonstrate that the separation factor decreased with PMA amount and led to the ultimate value at 4 wt% PMA amount. Then the increase of PMA content resulted in the decline of the separation factor. Under all conditions, PMA doped mixed matrix composite membrane had a higher separation factor and flux values according to the pristine PVA membrane. Of all the membranes studied, while the flux increased by the high temperature or feed methanol concentration, the separation factor of MeOH decreased. While the operation temperature was 50 °C, the feed methanol concentration was 10 wt%; 4 wt% PMA doped mixed matrix composite membrane has significant separation performance with a flux of 1.31 kg/m2h and separation factor of 121.04.

Influence of interfacial layer parameters on gas transport properties through modeling approach in MWCNTs based mixed matrix composite membranes

Precise prediction of the gas permeability behavior through the mixed matrix Composite membranes (MMMs) composed of the tubular fillers using existing theoretical approaches are infrequent. This is normally due to the neglecting the interfacial characteristics of the tubular filler particles i.e. multi-walled structured carbon nanotubes (MWCNTs) and a matrix composed of polymeric material in the existing theoretical models, especially, the Kang-Jones-Nair (KJN) model and Hamilton-Crosser model (HC) which were developed for the prediction of gas permeability behavior through the mixed matrix membranes (MMMs) composed of the tubular fillers. In this work, raw- and functionalized MWCNTs filler based MMMs in polysulfone (PSF) matrix were synthesized successfully, followed by morphological analysis on matrix interfacial layers parameters. KJN model was modified by introducing pseudo-dispersed phase fillers that influenced the interfacial layer and consequently overall gas permeabilities, which was ignored in existing models. The new proposed theoretical model is able to predict the gas permeability behavior with significantly reduced average absolute relative error (%AARE) of 1.26% compared to 52.43% and 42.71% for unmodified KJN and HC models, respectively. Furthermore, the mKJN model revealed that the interfacial layer thickness is a unique characteristic and is autonomous of the penetrant molecules of gas which may be influenced by the heterogeneity in the experimental conditions. The cross-sectional morphology and mKJN model revealed that the filler functionalization may lead to the improvement in filler-polymer interaction which thus reduced interfacial layer thickness.

Polyvinylamine/amorphous metakaolin mixed-matrix composite membranes with facilitated transport carriers for highly efficient CO2/N2 separation

In order to obtain high-performance facilitated transport membrane for CO2/N2 separation, we prepared mixed-matrix composite membranes (MMCMs) by polyvinylamine (PVAm) and the amorphous layered metakaolin (MK), with polysulfone (PSf) as a support. The attenuated total reflectance Fourier-transform infrared spectroscopy results revealed the strong interfacial interaction between the PVAm and the oxygen-rich MK. MK was homogenously dispersed in the PVAm matrix, as confirmed by scanning electron microscopy. The MMCMs showed the enhanced CO2 separation performance with a CO2 permeance of 152 GPU and a CO2/N2 selectivity of 78 at 1 bar under pure gas condition, when the MK loading was 1 wt%. These values were much higher than those of the PVAm membrane loaded with the crystalline multi-layer kaolin, with a CO2 permeance of 85 GPU and a CO2/N2 selectivity of 55. The enhanced separation performance is mainly ascribed to the increase of the intermolecular distance between the polymer chains after the addition of the MK sheets to the PVAm matrix, which was validated by X-ray diffraction. Moreover, the addition of the amorphous MK to PVAm can increase more tortuosity of gas transport than multi-layered and other shape fillers in the MMCMs as a result of the homogenous dispersion of the fully exfoliated MK in the membrane. Besides, the MMCMs exhibited excellent long-term stability performance even under mixed-gas conditions for over 300 h, with a CO2 permeance of 188 GPU and a CO2/N2 selectivity of 83.8, surpassing the Robeson's upper bound proposed in 2008.

Superior performance of surface-treated NaX@Pebax-1657 membranes for O2/N2 separation.

In this study, the performances of mixed matrix composite membranes (MMCMs) containing surface-treated NaX nanocrystals (ST-NaX-NCs) were experimentally and theoretically investigated for O2/N2 separation. For this purpose, the MMCMs were fabricated by the casting solution method and characterized by various analyses. The results reveal that there is a robust interaction between the polymer chains and the ST-NaX-NCs, and that the ST-NaX fillers are uniformly dispersed in the polymer matrix. The incorporation of ST-NaX-NCs alters the PEBAX polymer chain packing arrangement resulting in decreased membrane transport behavior for both O2 and N2 gases. The MMCM containing 16.7% wt ST-NaX-NCs has drastically enhanced air separation properties, with a selectivity that is increased to 204% of that of the neat membrane. Moreover, the Lewis–Nielsen model was modified by considering non-ideal effects in mixed matrix membranes, like the clogging of filler pores and polymer chain hardening around the nanocrystals, to predict the gas permeation behavior through the MMCMs. The comparison of the experimental and model results reveals that the modified model can accurately predict the gas permeability and selectivity through the MMCMs.

Effects of temperature on rice husk silica ash additive for fouling mitigation by polysulfone–RHS ash mixed-matrix composite membranes

It has been found that the preparation of green silica based on agricultural crops preserves environmental sustainability. In this study, rice husk silica (RHS) ash was prepared by burning rice husk (RH) at different temperatures (400 and 1200 °C). Both types of green RHS ash additives were blended with polysulfone dope, after which membranes were fabricated via phase inversion. The RHS ash that was synthesised at 400 °C (RHS400) had an amorphous structure with strong hydrophilic properties, while the composite membrane containing 3 wt% of RHS400 (A3 membrane) achieved the optimum properties of a dense top, an extended sub-layer of continuous smaller finger-like pores and a bottom layer of macrovoids. A satisfactory mean surface roughness, average pore size (1.90 ± 9.50 × 10−2 µm), porosity (40.66 ± 2.03%) and tensile strength (3.27 ± 0.16 MPa) were also obtained. The contact angle (52.5° ± 3.6°) further proved that this membrane was hydrophilic. The elemental and thermal analyses confirmed the presence of Si and O, which correlated with the 12% residual that was contributed by the silica inside the membrane. The optimum properties of the A3 membrane were an increased PWF (154.04 ± 7.70 L m−2 h−1) with the highest rejection of HA (96.00 ± 4.80%) and a fouling mitigation with the lowest internal resistance (6.79 ± 0.34 × 1012 m−1).

Polyvinylamine/graphene oxide/PANI@CNTs mixed matrix composite membranes with enhanced CO2/N2 separation performance

Lamellar PANI@CNTs-GO materials were prepared by intercalating polyaniline-coated carbon nanotubes (PANI@CNTs) in graphene oxide (GO) layers to regulate the interlayer spacing. Mixed matrix membranes (MMMs) with tuned structures were achieved by coating a mixed dispersion of PANI@CNTs-GO and polyvinylamine (PVAm) on an asymmetric polysulfone (PSf) membrane for enhancing its CO2 separation performance. The Fourier-transform infrared spectroscopy results showed that PANI was successfully coated on the surface of the CNTs. The X-ray diffraction results confirmed the intercalation of GO sheets with PANI@CNTs. PANI@CNTs-GO was uniformly dispersed in PVAm, as confirmed by scanning electron microscopy. The attenuated total reflectance Fourier transform infrared spectroscopy results revealed that strong interfacial interactions were present between PVAm and PANI@CNTs-GO. The MMM loaded with 1 wt% PANI@CNTs-GO showed the best CO2 separation performance with a CO2 permeance of 170 GPU and a CO2/N2 selectivity of 122.4 at 1 bar under the pure gas condition. These values were much higher than those of the pristine PVAm membrane (CO2 permeance = 73 GPU and CO2/N2 selectivity = 45.7). This enhanced separation performance can be mainly attributed to the effect of the facilitated transport carriers from amine groups in the interlayer spacing and the molecular sieving effect of the interlayer spacing. The MMMs exhibited excellent long-term stability even under the mixed-gas conditions for over 300 h with a CO2 permeance of 264 GPU and a CO2/N2 selectivity of 149.8.

Effect of Graphene Oxide Synthesis Method on Properties and Performance of Polysulfone-Graphene Oxide Mixed Matrix Membranes.

Graphene oxide (GO) has shown great promise as a nanofiller to enhance the performance of mixed matrix composite membranes (MMMs) for water treatment applications. However, GO can be prepared by various synthesis routes, leading to different concentrations of the attached oxygen functional groups. In this research, GO produced by the Hummers’, Tour, and Staudenmaier methods were characterized and embedded at various fractions into the matrix of polysulfone (PSf) and used to prepare microfiltration membranes via the phase inversion process. The effects of the GO preparation method and loading on the membrane characteristics, as well as performance for oil removal from an oil-water emulsion, are analyzed. Our results reveal that GO prepared by the Staudenmaier method has a higher concentration of the more polar carbonyl group, increasing the membrane hydrophilicity and porosity compared to GO prepared by the Hummers’ and Tour methods. On the other hand, the Hummers’ and Tour methods produce GO with larger sheet size, and are more effective in enhancing the mechanical properties of the PSf membrane. Finally, all MMMs exhibited improved water flux (up to 2.7 times) and oil rejection, than those for the control PSf sample, with the optimum GO loading ranged between 0.1–0.2 wt%.

Preparation of mixed matrix composite membrane for hydrogen purification by incorporating ZIF-8 nanoparticles modified with tannic acid

The incompatibility between nanofillers and polymer, caused by the agglomeration of nanoparticles and their weak interaction with each other, is still a challenge to develop mixed matrix composite membrane. Herein, we introduced the ZIF-8-TA nanoparticles synthesized by in situ hydrophilic modification into the hydrophilic poly(vinylamine) (PVAm) matrix to prepare composite membranes for H2 purification. The dispersion of ZIF-8 in water was improved by tannic acid modification, and the compatibility between ZIF-8 particles and PVAm matrix was enhanced by chemical crosslinking between the quinone groups in oxidized tannic acid (TA) and the amino groups in PVAm. Moreover, the compatibility between hydrophobic polydimethylsiloxane (PDMS) gutter layer and hydrophilic separation layer was achieved by the adhesion of TA-Fe3+ complex to the surface of PDMS layer during membrane preparation. The interlayer hydrophilic modification and the formation of separation layer were accomplished in one step, which simplified the preparation process. The experimental results indicated that when the TA addition used for modification was 0.5 g and the ZIF-8-TA0.5 content in membrane was 12 wt%, the prepared membrane showed the best separation performance with the CO2 permeance of 987 GPU and the CO2/H2 selectivity of 31, under the feed gas pressure of 0.12 MPa.

CO2/N2 selectivity enhancement of PEBAX MH 1657/Aminated partially reduced graphene oxide mixed matrix composite membrane

In this study, the capability of a mixed matrix composite membrane (MMCM) fabricated using polyether block amide polymer PEBAX MH1657 from Arkema and in lab synthesized aminated partially reduced graphene oxide (A-prGO) nanofiller as a selective layer has been studied for gas separation. Moreover, the effects of nanofiller addition on membrane structure properties and performance were examined. The PEBAX/A-prGO membrane was fabricated as a selective layer on top of a supporting substrate layer of polysulfone 1700. MMCM was prepared in five different loadings of A-prGO nanofiller (0, 0.05, 0.1, 0.2, 0.6 (w/w)%) of the used PEBAX amount. The synthesized nanofiller and fabricated MMCM were characterized using different characterization tests (XRD, FTIR, EDX, and SEM). The optimum separation of the membrane was found when the loading of A-prGO was 0.1%. The permeability of the membrane for CO2, N2 and CH4 gases were 47.5 Barrer for CO2, 0.45 Barrer for N2 & 2 Barrer for CH4 while the selectivity of CO2/N2 and CO2/CH4 are 105.6 and 23.75, respectively. Surprisingly, the fabricated membrane performance found to be above the Robeson 2008 upper bound of permeability- selectivity relation for CO2/N2 gases separation.

MOF-801 incorporated PEBA mixed-matrix composite membranes for CO2 capture

The combination of CO2-selective porous framework with polymeric material is promising for developing mixed-matrix membranes. In this work, a novel metal organic framework MOF-801 nanocrystal was introduced into polyether-block-amide (PEBA) polymer to fabricate a new mixed-matrix material for CO2 separation. A thin membrane layer consisting of MOF-801 filler and PEBA matrix was successfully formed on a porous substrate via spinning-coating approach. SEM, XRD, TGA, FTIR and adsorption test were applied to systematically characterize the as-prepared MOF-801 crystals and MOF-801/PEBA mixed-matrix composite membranes. It was found that uniform incorporation of microporous MOF-801 with preferential CO2 adsorption provided fast and selective transport channels for CO2 over N2, thereby achieving an increase both in CO2 permeance and CO2/N2 mixed-gas selectivity compared with pure PEBA membrane. The optimized MOF-801/PEBA mixed-matrix composite membrane (MOF loading of 7.5 wt%) exhibited high and stable separation performance with CO2 permeance of 22.4 GPU and CO2/N2 selectivity of 66 under mixed-gas permeation test, showing great potential for practical CO2 separation.

Mixed-Matrix Composite Membranes Based on UiO-66-Derived MOFs for CO2 Separation.

We demonstrated a novel mixed-matrix composite membrane (MMCM) based on acrylated polyurethane (APU) and UiO-66 nanoparticles to separate CO2/N2 mixture. UiO-66 and functionalized UiO-66 including NH2-UiO-66 and glycidyl methacrylate (GMA)-UiO-66 were loaded into APU/2-hydroxyethyl methacrylate (APUH) matrix at variable concentrations between 3 and 30 wt %. APUH/GMA-UiO-66 MMCMs exhibited strong adhesion with a support layer of polyester/polysulfone, which was not deteriorated after immersion in water for a long time (20 days). Incorporation of UiO-66 and its functionalized forms increased simultaneously permeability and CO2/N2 selectivity, which were indeed superior in comparison with those of MMCMs reported previously. GMA-UiO-66-filled MMCM displayed a CO2 permeance of 14.5 Barrer and a CO2/N2 selectivity of 53 at a critical concentration (25 wt %). This attractive separation performance of APUH/UiO-66 offered an exciting platform for the development of composite membranes for sustainable CO2 separations.

Liquid-like CNT/SiO2nanoparticle organic hybrid materials as fillers in mixed matrix composite membranes for enhanced CO2-selective separation

Liquid-like nanoparticle organic hybrid materials with core/canopy/corona were used as fillers in Pebax-1657 matrix to fabricate mixed-matrix membranes. The effect of composite core composition on CO2/N2separation performance was systematically investigated.

Supported PEBA-zeolite 13X nano-composite membranes for gas separation: Preparation, characterization and molecular dynamics simulation

Poly ether block amide (PEBA) incorporated with zeolite 13X nanoporous was deposited onto a PSf/PE layer. The fabricated Mixed Matrix Composite Membranes (MMCMs) were weighed up by XRD, SEM, FTIR and AFM analysis. The influence of PEBA concentration, number of coated layers, zeolite loading, PDMS cover layer and a set of conditions for operating a particular process on the gas separation performance of the fabricated membranes were specified through pure gases permeability examination. The best CO2 permeability and CO2/N2 and CO2/CH4 selectivity for the MMCM loaded with 1 wt% zeolite 13X showed an increase in 200%, 1030% and 3633% compared to the neat membrane. CO2/N2 and CO2/CH4 selectivity increased 153% and 18.24%, after coating a PDMS cover layer on the PEBA-zeolite (1%)/PSf/PE, respectively. Molecular dynamics (MD) and Grand Canonical Monte Carlo (GCMC) have been performed to reckon the influence of PEBA and zeolite 13X contents on gas separation and thermodynamic properties. Four different Neat and MMMs were constructed in simulation part regarding the incorporation of 0, 0.5, 1 and 2 wt% of zeolite nano-fillers. Fractional free volume (FFV), Density, X-ray diffraction (XRD) and radial distribution function (RDF) were performed to understand the nanostructure properties of the membranes. Having used three different gases (N2, CO2 and CH4), the permeability and selectivity of constructed membranes have been studied.

Robust Covalently Cross-linked Polybenzimidazole/Graphene Oxide Membranes for High-Flux Organic Solvent Nanofiltration.

Robust, readily scalable, high-flux graphene oxide (GO) mixed matrix composite membranes were developed for organic solvent nanofiltration. Hydroxylated polybenzimidazole was synthesized by N-benzylation of polybenzimidazole with 4-(chloromethyl)benzyl alcohol, which was confirmed by FTIR and NMR spectroscopy. Flat-sheet composite membranes comprising of polybenzimidazoles and 1 or 2 wt % GO were fabricated via conventional blade coating and phase inversion. Subsequently, GO was covalently anchored to the hydroxyl groups of the polymer using a diisocyanate cross-linking agent. The even distribution of GO in the membranes was mapped by visible-light microscopy. Hydroxylation and incorporation of GO in the polymer matrix increased the permeance up to 45.2 ± 1.6 L m-2 h-1 bar-1 in acetone, nearly 5 times higher than the unmodified benchmark membrane. The enhancement in permeance from the addition of GO did not compromise the solute rejection. The composite membranes were found to be tight in seven organic solvents, having molecular weight cut-offs (MWCO) as low as 140 g mol-1. Permeance increased with increasing solvent polarity, while rejection of a 420 g mol-1 pharmaceutical remained over 93%. The covalent anchoring resulted in robust composite membranes that maintained constant performance over 14 days in a continuous cross-flow configuration.

Mixed-matrix hollow fiber composite membranes comprising of PEBA and MOF for pervaporation separation of ethanol/water mixtures

Pervaporation membrane technology plays an important role in production of renewable bio-fuels. To improve the separation performance of polymeric membranes, an effective approach is development of mixed-matrix membranes containing high-performing fillers such as metal–organic frameworks. Towards practical application, hollow fiber could be an ideal substrate for mixed-matrix composite membrane, while current fabrications of this kind of composite membrane are relative complicated and challenging. In this work, a novel ceramic hollow fiber supported mixed-matrix composite membrane made of RHO-[Zn(eim)2] (MAF-6, Heim = 2-ethylimidazole) nanoparticles and poly (ether-block-amide) (PEBA) was fabricated via a facile dip-coating approach. SEM, XRD, TGA, contact angle and swelling measurements, nano-scratch technique were employed to study the morphology, crystal structure, thermal stability, surface property and interfacial adhesion of the resulting MAF-6/PEBA mixed-matrix hollow fiber composite membranes, respectively. These membranes were applied for recovering ethanol from aqueous solution via pervaporation. The effects of MAF-6 loading, as well as operating conditions (e.g., temperature, feed concentration and long-term stability) on the PV performance were systematically investigated. The PV performance of PEBA membrane, both flux and separation factor, were remarkably enhanced by uniformly incorporating MAF-6 nanoparticles. Total flux of 4446 g/m2 h and separation factor of 5.6 (feed: 5 wt% ethanol/water, 60 °C) was achieved for the optimized MAF-6/PEBA mixed-matrix hollow fiber composite membrane, which shows great advantages over the reported PEBA-based membranes for ethanol/water separation.

Recent advances on mixed matrix membranes for CO2 separation

Recent advances on mixed matrix membrane for CO2 separation are reviewed in this paper. To improve CO2 separation performance of polymer membranes, mixed matrix membranes (MMMs) are developed. The concept of MMM is illustrated distinctly. Suitable polymer and inorganic or organic fillers for MMMs are summarized. Possible interface morphologies between polymer and filler, and the effect of interface morphologies on gas transport properties of MMMs are summarized. The methods to improve compatibility between polymer and filler are introduced. There are eight methods including silane coupling, Grignard treatment, incorporation of additive, grafting, in situ polymerization, polydopamine coating, particle fusion approach and polymer functionalization. To achieve higher productivity for industrial application, mixed matrix composite membranes are developed. The recent development on hollow fiber and flat mixed matrix composite membrane is reviewed in detail. Last, the future trend of MMM is forecasted.

Preparation and characterization of (Pebax 1657 + silica nanoparticle)/PVC mixed matrix composite membrane for CO2/N2 separation

In this work, the films of poly(ether-block-amide) (Pebax 1657) and hydrophilic/hydrophobic silica nanoparticles (0–10 wt%) were coated on a poly(vinyl chloride) (PVC) ultrafiltration membrane to form new mixed matrix composite membranes (MMCMs) for CO2/N2 separation. The membranes were characterized by SEM, FTIR, DSC and XRD. Successful formation of a non-porous defect-free dense top layer with ~4 μm of thickness and also uniform dispersion of silica nanoparticles up to 8 wt% loading in Pebax matrix were confirmed by SEM images. The gas permeation results showed an increase in the permeance of all gases and an increase in ideal CO2/N2 selectivity with the increase in silica nanoparticle contents. Comparison between the incorporation of hydrophilic and hydrophobic silica nanoparticle into Pebax matrix revealed that the great enhancement of CO2 solubility is the key factor for the performance improvement of Pebax + silica nanoparticle membranes. The best separation performance of the hydrophilic silica nanoparticle-incorporated Pebax/PVC membrane for pure gases (at 1 bar and 25 °C) was obtained with a CO2 permeability of 124 barrer and an ideal CO2/N2 selectivity of 76, i.e., 63 and 35% higher than those of neat Pebax membrane, respectively. The corresponding values for hydrophobic silica nanoparticle-incorporated Pebax/PVC membrane were 107 barrer for CO2 permeability and 61 for ideal CO2/N2 selectivity. Also the performances of MMCMs improved upon pressure increase (1–10 bar) owing to the shift in plasticizing effect of CO2 towards the higher pressures. In addition, an increase in permeabilities with a decrease in ideal selectivity was observed upon temperature increase (25–50 °C) due to the intensification of chain mobility.

Magnetoresponsive Poly(ether sulfone)-Based Iron Oxide cum Hydrogel Mixed Matrix Composite Membranes for Switchable Molecular Sieving.

Stimuli-responsive membranes that can adjust mass transfer and interfacial properties "on demand" have drawn large interest over the last few decades. Here, we designed and prepared a novel magnetoresponsive separation membrane with remote switchable molecular sieving effect by simple one-step and scalable nonsolvent induced phase separation (NIPS) process. Specifically, poly(ether sulfone) (PES) as matrix for an anisotropic membrane, prefabricated poly(N-isopropylacrylamide) (PNIPAAm) nanogel (NG) particles as functional gates, and iron oxide magnetic nanoparticles (MNP) as localized heaters were combined in a synergistic way. Before membrane casting, the properties of the building blocks, including swelling property and size distribution for NG, and magnetic property and heating efficiency for MNP, were investigated. Further, to identify optimal film casting conditions for membrane preparation by NIPS, in-depth rheological study of the effects of composition and temperature on blend dope solutions was performed. At last, a composite membrane with 10% MNP and 10% NG blended in a porous PES matrix was obtained, which showed a large, reversible, and stable magneto-responsivity. It had 9 times higher water permeability at the "on" state of alternating magnetic field (AMF) than at the "off"-state. Moreover, the molecular weight cutoff of such membrane could be reversibly shifted from ∼70 to 1750 kDa by switching off or on the external AMF, as demonstrated in dextran ultrafiltration tests. Overall, it has been proved that the molecular sieving performance of the novel mixed matrix composite membrane can be controlled by the swollen/shrunken state of PNIPAAm NG embedded in the nanoporous barrier layer of a PES-based anisotropic porous matrix, via the heat generation of nearby MNP. And the structure of such membrane can be tailored by the NIPS process conditions. Such membrane has potential as enabling material for remote-controlled drug release systems or devices for tunable fractionations of biomacromolecule/-particle mixtures.

Relationship between polymer–filler interfaces in separation layers and gas transport properties of mixed matrix composite membranes

To systematically explore polymer–filler interface and its influence, a series of mixed matrix composite membranes were fabricated by coating the mixture comprised of polyvinylamine(PVAm) and different inorganic nanofillers on polysulfone(PS) flat ultrafiltration membranes. Multiwalled carbontube(MWCNT), SiO2 and ZSM-5 were chosen as pristine inorganic nanofillers, and MWCNT–NH2, SiO2–NH2 and ZSM-5–NH2 were used as modified inorganic nanofillers. Possible gas transport mechanisms are discussed. A method of assessing the size of interface voids is developed by analyzing a trend in gas permeance with increasing feed pressure. The effect of feed pressure on gas permeance of the mixed matrix composite membranes was investigated. For PVAm–pristine inorganic nanofiller/PS membranes, membrane compaction, void-filling effect, surface flow and interface void channels affect its N2, O2 or CH4 permeance change with increasing feed pressure. The size of interface voids varies in the order of PVAm–ZSM-5 interface voids>PVAm–MWCNT interface voids>PVAm–SiO2 interface voids. Furthermore, gas permeance of PVAm-modified inorganic nanofiller/PS membrane is lower than that of the corresponding PVAm–pristine nanofiller/PS membrane. The result suggests that surface modification of inorganic nanofillers with compound containing the same functional groups as polymer is an effective way to improve the interface compatibility between polymer chains and modified inorganic nanofillers.