Polyetherimide Membranes Research Articles

Crosslinked polyetherimide based electrospun membrane: Effect of fibre morphology on hot oil sorption

Handling hot oil spillage, particularly from oil refineries, petrochemical industry and automobiles is challenging and there have been limited solutions to address the issue. Polyetherimide (PEI) electrospun fibrous membranes were developed in this study by leveraging PEI's high-temperature stability to serve as promising materials for hot oil sorption. The morphology of the membrane forming fibers varied from circular to dumbbell shaped, by judicious choice of solvents of varying boiling points, to study the effect of fiber morphology on oil sorption capacity. Crosslinking of PEI membranes was carried out using ethylenediamine (EDA) to impart structural integrity and resiliency to the membranes. The PEI membrane composed of dumbbell-shaped fibers demonstrated an oil-sorption capacity of 25.4 ±1.5 g/g for engine oil at 150°C within one hour, outperforming a commercial polypropylene (PP) nonwoven absorbent, which failed and collapsed under the same high-temperature conditions. Enhanced oil sorption in the dumbbell-shaped fibrous membrane was achieved due to its lower tortuosity, aligned inter-fiber channels, and higher capillary pressure. Usefulness and sorption capacity of PEI based electrospun membranes may further be explored for controlling the oil spillage through introduction of specific surface features and functionalization.

Mid-Infrared Spectrometer Based on Tunable Photoresponses in Pdse2

Mid-infrared (mid-IR) photodetection is important for various applications, including biomedical diagnostics, security, chemical identification, and free-spacing optical communications. However, conventional “photon” mid-IR photodetectors require liquid nitrogen cooling (i.e., MCT). Furthermore, acquiring mid-IR spectra usually involves a complex and expensive Fourier Transform Infrared spectrometer, a tabletop instrument consisting of a meter-long interferometer and MCT detectors, which is not suitable for mobile and compact device applications. In this work, we present tunable photoresponsivity in the mid-IR wavelength in palladium diselenide (PdSe2) – molybdenum disulfide (MoS2) heterostructure field-effect transistors (FETs), operating at room temperature. Furthermore, we applied a tunable membrane cavity to modulate the Fabry–Pérot resonance to modulate the absorption spectrum of the device layer. We used a robust polyetherimide (PEI) membrane with CVD-grown graphene to electrically tune the membrane structure. For the next step, we will integrate the PdSe2-based photodetector and tunable membrane to increase detection sensitivity and spectrum tunability to realize the ‘learning’-based spectroscopy.

Polyethyleneimine NH2-UiO-66 nanofiller-based mixed matrix membranes for natural gas purification

Effective separation of CO2 from CH4 is crucial for the purification of natural gas, which requires membrane materials with high permeability, selectivity, and stability of under high pressures. In this work, a high CO2-affinity MOF-based nanofiller (Pin@NH2-UiO-66) was prepared and integrated in polyetherimide (PEI) to prepare mixed matrix membranes (MMMs) for enhanced CO2/CH4 separation capabilities. The Pin@NH2-UiO-66 nanofiller comprised an in situ-formed polyethyleneimine-NH2-UiO-66 composite prepared via a one-pot synthesis. The polyethyleneimine was covalently attached to the H2BDC-NH2 ligand allowing for a stronger integration within the PEI matrix. The polyethyleneimine affects the nucleation of MOF, leading to miniaturization of the MOF particles. The smaller-sized filler is beneficial for improved interaction at the filler-matrix interface. The numerous amino functionalities grafted onto the NH2-UiO-66 increased the CO2 adsorption sites, thereby enhancing the affinity for CO2. Owing to the improved interaction, the elevated CO2 attraction, and the inherent properties of the porous NH2-UiO-66, the fabricated MMMs preformed superior in separating CO2/CH4. The 30-Pin@NH2-UiO-66-PEI membrane (containing 30 wt% nanofiller) exhibited a CO2/CH4 selectivity of 27.7 and a CO2 permeability of 2498.9 Barrer. The CO2 permeability was 21 times greater than that of the pristine PEI membrane, and 4 times higher compared to P@NH2-UiO-66 MMM with polyethyleneimine modified MOF filler prepared by a traditional wet impregnation method. Additionally, the novel MMM demonstrates excellent separation stability under conditions that mimic industrial settings, demonstrating its potential application for natural gas purification.

Free radical graft polymerization of hydroxyethyl methacrylate and acrylic acid on polyetherimide membrane surface via redox system to improve anti-fouling and oil resistance performance

In this paper, a new scheme of graft polymerization of acrylic acid (AA) and hydroxyethyl methacrylate (HEMA) initiated by the generation of free radicals in a redox system was used to modify the surface of polyetherimide (PEI) membranes and to improve the antifouling and oil resistance properties. Various physicochemical characterization techniques (ATR-FTIR, XPS, TG, SEM, AFM, etc.) confirmed the successful grafting of hydrophilic monomers onto the PEI membrane surface. Further, the effects of different monomer concentrations on graft density, permeation separation, contamination resistance, and mechanical properties were investigated. Both PEI-g-PAA and PEI-g-PHEMA showed better hydrophilicity (WCA decreased from 60° in PEI to 33° and 45°, respectively), efficient separation (75–84%) in oil-containing wastewater filtration tests with methyl tert-butyl ether (MTBE) and petroleum ether with a slight decrease in mechanical strength. In addition, bovine serum albumin (BSA) and MTBE were selected as contaminants to examine the antifouling properties. Compared to the flux recovery rate (FRR) of 75% for the original PEI membranes, the grafted membranes almost wholly recovered the permeate flux with a simple backwash of ultrapure water. In summary, the results of the above study suggest the development of a novel and simple preparation strategy for surface grafting modification of PEI membranes, which will facilitate the subsequent research of PEI materials in membrane development, and the resulting grafted membranes will be of developmental and exploratory value in the field of oil and water treatment.

Polyhydroxy phenolic resin coated polyetherimide membrane with biomimetic super-hydrophily for high-efficient oil–water separation

In terms of treating the problem of oily wastewater, membrane separation technology has always been a simple and efficient method of oil–water emulsion separation. Inspired by the hydrophilic bumps of the desert beetle, the polyetherimide (PEI) fiber membrane with super-hydrophilic/underwater super-oleophobic properties was prepared by electrospinning and subsequent seeded aggregation strategy of resorcinol (R) and formaldehyde (F). The membrane (PEI@RF) demonstrates pearl necklace-like structures and good antifouling properties, oil–water separation performances, as well as good stabilities in a variety of environments (immersed in water at high/low temperature, and in acid/alkali/salt solutions). More importantly, the as-prepared membrane exhibits excellent performance for various kinds of oil–water mixtures separation, and the corresponding separation fluxes and efficiencies are above 2600 L/m2·h and 99 %, respectively.

Modelling relative humidity and temperature effects on CO2 gas transport in polyetherimide

The aim of this work is to study the effect of relative humidity (RH) on CO2 gas transport in polyetherimide (PEI) membranes. The Non-Random Hydrogen Bonding model, extended to the case of non-equilibrium glassy polymers (NETGP-NRHB model), is used to interpret the sorption thermodynamics in glassy polymer/penetrant mixtures. Furthermore, a new diffusion model (namely NETGP-NRHB-DM), in the spirit of the Free Volume Theory, is used in combination with the NETGP-NRHB model to interpret the gas permeation. The parameters of the two models have been obtained partly from the literature and partly from a dedicated experimental campaign. The full set of parameters is used in a predictive manner to calculate the permeability coefficient of CO2 in PEI at different temperatures and relative humidity conditions. The model results are validated against a complete set of experimental data specifically carried out for the present investigation. The CO2 permeability predictions are satisfactory, but a slight deviation between the calculated results and the experimental data is observed when the average amount of water in the membrane is high, probably due to the onset of water clustering. In fact, the phenomenological expression of the mobility coefficient of NETGP-NRHB-DM is not properly suited to describe the complex picture involving different kind of water mers starting from the water clustering concentration onset.

Efficient ion sieving and ion transport properties in sub-nanoporous polyetherimide membranes

Ion separation has great potential in a variety of applications, including water treatment, energy conversion, and resource recovery. The sub-nanoporous polymeric membranes prepared by track-UV method has good prospects for ion separation. However, the ion selectivity of reported sub-nanoporous membranes is still not ideal. In this study, we prepared sub-nanoporous polyetherimide membranes. The sub-nanometer gaps on the membrane exhibit a unique monovalent ion selective transport. The selectivity attributes to the dehydration energy barrier of ions and the interaction between ions and surface charge. The single salt electrodialysis experiments showed that the ideal selectivity of K+/Mg2+ was as high as 8900, and the potassium ion flux was 0.49 mol h−1 m−2. In addition, the membrane showed a K+/Li+ selectivity of up to 6 and a K+/Mg2+ selectivity of 67 under mixed salt conditions. This work provides a valuable insight into the future large-scale and expedited production of sub-nanoporous membranes featuring exceptional ion separation performance.

PEI@MOFs thin film nanocomposite (TFN) membrane for efficient CO2 separation

Polyetherimide (PEI) membrane exhibits high CO2 selectivity while suffer from low permeance thus limiting the further application in CO2 separation. Thin film nanocomposite (TFN) membrane which contains a thin selective functional layer with nanomaterials porous fillers is a new class of high-performance membranes. In this work, a series of novel PEI@MOFs TFN membranes were prepared for efficient CO2 separation. The sub-micro scale PEI layers (about 400 nm) with four kinds of MOFs fillers including 3-dimensional MOFs nanoparticles (UiO-66 and MIL-101 (Cr)) and MOFs nanosheets (2-D CuBDC and Zn2(bim)4) were prepared by a simple spin-coating strategy. The properties and CO2 separation performance of the TFN membranes were further studied. The MOFs in PEI increased the diffusion coefficient and selectivity for CO2, at the same time, the ultra-thin functional layer maximized reducing the CO2 transport resistance. As a result, the PEI@MOFs TFN membranes exhibited high CO2 permeance as well as enhanced CO2 separation performance which close to the Robeson upper bound. The PEI@CuBDC TFN membrane exhibited CO2 permeance of 15.6 GPU (3.3 times higher than the neat PEI membrane), and the selectivity of CO2/CH4 reached 39.8 (2.2 times higher than the neat PEI membrane). In addition, the PEI@MOFs TFN membranes showed good thermal and operation stability.

Dye sieving and dye/salt separation PEI-based loose nanofiltration membrane modified by NH2-MIL-101(Fe) and polyphenol coating

Effective dye sieving and dye/salt separation could recycle valuable resources during textile wastewater treatment. In this work, a loose nanofiltration (NF) membrane with outstanding performance was constructed with facile materials including the surface polyphenol coating and the polyetherimide (PEI) support. Firstly, the mixed matrix support membrane was prepared by incorporating Fe-based MOF NH2-MIL-101(Fe) into PEI membrane via non-solvent induced phase separation (NIPS) method, then the polyphenol coating based on vanillyl alcohol, which was the characteristic component derived from Gastrodia elata Blume, was co-deposited on the support PEI membrane, followed by the treatment of 1,3-propane sultone. In this way, the optimal loose NF membrane could have a high good pure water permeability (87.9 L·m−2·h−1·bar−1) while high dye/salt selectivity was reached (Selectivity: 58.9 for Congo Red/NaCl; 46.8 for Conge Red/Na2SO4). Moreover, a mixture of large molecule dye and small molecule dye could be sieved and the optimal loose NF membrane showed outstanding antifouling capacity with the flux recovery ratio of 85.7%, 98.1%, and 97.9% respectively for bovine serum albumin (BSA), sodium alginate (SA), and humic acid (HA), which was further analyzed and calculated by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. The long-term stability during EBT/Na2SO4 mixture filtration endowed the membrane with great potential in treating textile wastewater.

Preparation of a Solvent-Resistant Nanofiltration Membrane of Liquefied Walnut Shell Modified by Ethylenediamine.

N,N-dimethylformamide (DMF) has excellent chemical stability and is widely used as an aprotic polar solvent. In order to reduce production costs and reduce pollution to the surrounding environment, it is necessary to recycle and reuse DMF. Previous research has found that the thin film composite nanofiltration membrane prepared from liquefied walnut shells exhibited a high rejection rate in DMF, but relatively low permeance and mechanical strength. In order to increase permeance without compromising the separation performance, ethylenediamine (EDA) is used as a modifier to graft onto the structure of liquefied walnut shell through the Mannich reaction. Then, modified liquefied walnut shell as an aqueous monomer reacts with trimesoyl chloride (TMC) via the interfacial polymerization method on the EDA-crosslinked polyetherimide (PEI) membrane. The results show that the permeance of the prepared membrane is significantly improved by an order of magnitude, demonstrating a rejection rate of 98% for crystal violet (CV), and a permeance of 3.53 L m-2 h-1 bar-1 in DMF. In conclusion, this study reveals the potential of utilizing liquefied walnut shells as raw materials for preparing high-performance separation membranes and demonstrates that surface modification is a feasible approach to enhance permeance of membranes without sacrificing the rejection rate.

Zr‐Based Metal‐Organic Framework UiO‐66/Ultem® 1000 Membranes for Effective CO2/H2 Separation

AbstractMixed‐matrix membranes (MMMs) using UiO‐66 nanofillers as dispersing inorganic phase and polyetherimide (PEI) as continuous polymeric matrix were synthesized. Different UiO‐66 loadings of 10, 20, and 30 wt % were applied. The morphology and UiO‐66 dispersion over the prepared MMMs were examined. Gas separation measurements were performed for H2/CO2 gas mixture to evaluate the influence of UiO‐66 on the separation yield of resulting membranes. When compared with pristine PEI membranes, MMMs containing metal‐organic framework (MOF) nanoparticles revealed superior H2 permeability and H2/CO2 separation factor, e.g., maximum permeability values of 14.6 and 5.5 Barrer were observed for H2 and CO2 at a filler loading of 10 wt % and an applied pressure of 4.0 bar.

Ultrathin organic solvent nanofiltration membrane with polydopamine-HKUST-1 interlayer for organic solvent separation

Polydopamine (PDA) and metal-organic skeleton HKUST-1 were co-deposited on the base membrane of hexamethylenediamine (HDA)-crosslinked polyetherimide (PEI) ultrafiltration membrane as the interlayer, and high-throughput organic solvent nanofiltration membrane (OSN) was prepared by interfacial polymerization and solvent activation reaction. The polyamide (PA) layer surface roughness from 28.4 nm in PA/PEI to 78.3 nm in PA/PDA-HKUST-10.6/PEI membrane, reduced the thickness of the separation layer from 79 to 14 nm, and significantly improved the hydrophilic, thermal and mechanical properties. The flux of the PA/PDA-HKUST-10.6/PEI membrane in a 0.1 g/L Congo Red (CR) ethanol solution at 0.6 MPa test pressure reached 21.8 L/(m2·hr) and the rejection of CR was 92.8%. Solvent adsorption test, N, N-dimethylformamide (DMF) immersion experiment, and long-term operation test in ethanol showed that the membranes had high solvent tolerance. The solvent flux test demonstrated that, under the test pressure of 0.6 MPa, the flux of different solvents ranked as follows: methanol (56.9 L/(m2·hr)) > DMF (39.6 L/(m2·hr)) > ethanol (31.2 L/(m2·hr)) > IPA (4.5 L/(m2·hr)) > N-hexane (1.9 L/(m2·hr)). The ability of the membranes to retain dyes in IPA/water dyes solution was also evaluated. The flux of the membrane was 30.4 L/(m2·hr) and the rejection of CR was 91.6% when the IPA concentration reached 50%. This OSN membrane-making strategy is economical, environment-friendly and efficient, and has a great application prospect in organic solvent separation systems.

Low-pressure air plasma-assisted acrylic grafted polyetherimide ultrafiltration membranes with excellent oil-water separation and high anti-fouling performances

This paper reports the first surface modification of polyetherimide (PEI) ultrafiltration membranes using low-pressure air plasma-treated surfaces to induce acrylic acid (AA) graft polymerization, significantly improving their retention and fouling resistance properties. The successful formation of graft layers was verified by water contact angle (WCA) measurement of hydrophilic changes and Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis of the surface chemistry. Scanning electron microscopy (SEM) was used to analyze the morphological features, and atomic force microscopy (AFM) was tested for changes in surface roughness. The overall property changes after grafting were evaluated by mechanical tests and filtration tests. Methyl tert-butyl ether (MTBE) was chosen to measure the oil-water separability. The results showed that the membrane surface obtained PAA dense graft layer and improved hydrophilicity (CA from 57.62° to 29.26°) with no loss of tensile properties. In addition, the modified grafted membranes showed a high retention rate of BSA of 95.1 %, while the rejection rate of MTBE increased from 31.8 % to 75.9 %. Notably, PEI-g-AA fully recovered the permeability by simple water backwashing, exhibiting excellent antifouling performance. Therefore, this communication demonstrates that graft modification on the surface of PEI membranes is feasible and effective, and provides a new idea of PEI modification, which is valuable for exploring the development of high-efficiency ultrafiltration membranes.

Performance optimization of polyetherimide‐zeolite 4A mixed matrix membranes for carbon dioxide/methane separation process using response surface methodology

AbstractThe performance optimization studies of zeolite 4A embedded polyetherimide mixed matrix membranes to separate carbon dioxide/methane by simultaneously considering the effect of process parameters on process responses were the focus of this study. Mixed matrix membranes were characterized and analyzed. The thermophysical characteristics of the synthesized membranes were assessed by different analytical equipment. The permeability of pure gases was determined at varying feed pressures (4 bar to 10 bar) to evaluate gas separation performance. Process optimization studies were accomplished by response surface methodology to find the relation of pressure and zeolite loading on carbon dioxide and methane permeability, and carbon dioxide/methane selectivity. The characterization results revealed that all membranes were dense in structure and has improved thermal stability. The spectrometry results confirmed the molecular interaction between polyetherimide and zeolite 4A filler. Gas permeability results showed a more than 90 % increase in carbon dioxide permeability compared to the nascent polyetherimide membrane. Similarly, selectivity of mixed matrix membranes was 45 % higher than polyetherimide membrane. The optimal operating conditions were found to be 20 wt. % zeolite loading and 6 bar pressure with overall desirability of 0.700. These membranes can find potential in various gas separation applications.

Optimizing hydrogen purification performance by membrane from industrial waste of methanol production

There is an increasing interest to migrate from fossil fuel energy dependency to a greener hydrogen economy. In order to meet this challenge, hydrogen should be made cheap and readily available for both industrial and public consumption. In this research, polyetherimide membrane was used to achieve highly purified hydrogen from methanol purge gas (MPG) containing hydrogen, carbon dioxide, nitrogen, carbon monoxide and methane gas. The novelty of this research stems from the development of semi-empirical models for correlating the membrane's characteristics and operating condition with purity and recovery of hydrogen from penta-nary MPG components and optimizing the membrane's purification process to achieve maximum hydrogen purity and recovery. Results from the study suggest that membrane area was one of the important factors affecting the hydrogen purity in the permeate. Keeping stage cut and membrane thickness constant at 0.340 and 0.25 µm, respectively, hydrogen purity was increased from 86.00% to 99.00% by increasing membrane area from 55.4 to 80.0 cm2. Membrane thickness was found to affect the hydrogen recovery in permeate significantly. By reducing the thickness from 25.00 to 1.00 µm, the hydrogen recovery was increased from merely 3.00% to 43.00% at a constant stage cut of 0.3400 and membrane area of 55.4 cm2. When the membrane parameters were optimized at 80.0 cm membrane area, 0.25 um membrane thickness and 0.3395 stage cut, the maximum hydrogen purity and recovery from this model achieved 99.99% and 53.89%, respectively.

Blend membranes comprising polyetherimide and polyvinyl acetate with improved methane enrichment performance

A clean and sustainable energy source, biogas is widely accessible worldwide. The caloric value of biogas is related to its methane content, and therefore removal of other gases is essential for reaping the benefits of this cleaner resource. In contrast to other classical techniques, membrane technology is relatively new yet extremely promising for methane enrichment. The methane enrichment performance of polymeric membranes is constrained, hence newer material combinations have been investigated to enhance membrane performance. In this study, blend membranes comprised of polyetherimide (PEI) and polyvinyl acetate (PVAc) in varying proportions were prepared by adopting the wet-phase inversion technique. The generated pure, and blend membranes were characterized for the morphological, thermal, and structural study. The interactions of PEI and PVAc in blend samples were verified by FTIR analysis. On the other hand, SEM investigation indicated that the membranes have an anisotropic porous structure with a dense skin layer at the top. Subsequently, a single glass transition temperature (Tg), as validated by DSC analysis, indicates that the blended polymers are miscible. Furthermore, membranes’ performance for gas separation was assessed regarding selectivity and permeance at feed pressures ranging from 2 to 6 bar. The permeation results showed that the CO2 permeance has increased by 40.47% with the addition of 4 wt % PVAc at 2 bar pressure. Furthermore, ideal selectivity improves as the blend ratio increases; nonetheless, the highest value for CO2/CH4 ideal selectivity was attained with a 2 wt % PVAc addition and at 2 bar pressure, which is approximately 26% greater than the pure PEI membrane. At 4 bar pressure, optimum CO2/N2 selectivity value of 22.50 was achieved. The findings indicate that PVAc is an excellent option for expanding the separation performance of blended polymeric membranes for biogas enrichment.

High Ion Conductive and Selective Membrane Achieved through Dual Ion Conducting Mechanisms.

Conventional ion-selective membranes, that ision-exchange and porous membranes, are unable to perform high conductivity and selectivity simultaneously due to the contradictions between their ion selecting and conducting mechanisms. In this work, a bifunctional ion-selective layer is developed via the combination of nanoporous boron nitride (PBN) and ion exchange groups from Nafion to achieve high ion conductivity through dual ion conducting mechanisms as well as high ion selectivity. A template-free method is adopted to synthesize flake-like PBN, which is further enmeshed with Nafion resin to form the bifunctional layer coated onto a porous polyetherimide membrane. The double-layer membrane exhibits excellent ion selectivity (1.49 × 108 mS cm-3 min), which is 22 times greater than that of the pristine porous polyetherimide membrane, with outstanding ion conductivity (64 mS cm-1 ). In a vanadium flow battery, the double-layer membrane achieves a high Coulombic efficiency of 97% and outstanding energy efficiency of 91% at 40mA cm-2 with a stable cycling performance for over 700 cycles at 100mA cm-2 . PBN with ion exchange groups may therefore offer a potential solution to the limitation between ion selectivity and conductivity in ion-selective membranes.

Calcium-alginate/HKUST-1 interlayer-assisted interfacial polymerization reaction enhances performance of solvent-resistant nanofiltration membranes

This study aimed to further enhance the solvent stability and flux of organic solvent-resistant nanofiltration (OSN) membranes. Based on hexane diamine cross-linked polyetherimide (PEI) ultrafiltration membranes, in-situ calcium alginate (CaAlg) hydrogel doped with HKUST-1 was constructed as an interlayer, and then the OSN membrane with an integral covalent bond structure was constructed from interfacial polymerization reaction and NN dimethylformamide (DMF) activation. The membrane showed ultra-thinness (polyamide (PA) layer thickness reduced from 97 to 11 nm), large surface area (surface roughness increased from 75.6 to 113 nm), high hydrophilicity (water contact angle reduced from 60.1° to 54.45°), and negative charge. The CaAlg-HKUST-1 interlayer limited the piperazine diffusion rate by hydrogen bonding and covalent bonding, etc., reduced the thickness of the PA layer, and linked the base membrane and the PA layer by its internal integral covalent bonding, which effectively enhanced the structural stability of the OSN membrane. The PA/CaAlg-HKUST-16/PEI membrane achieved a flux of 29.4 L·m−2·h−1 in ethanol and a rejection of 94.7 % in 0.1 g·L-1 methyl blue. Different dye rejection tests, solvent flux tests, DMF and acetone immersion tests, fouling resistance tests, and continuous operation tests show PA/CaAlg-HKUST-16/PEI membrane has better solvent resistance, dye separation performance, and stable membrane flux. Hence, it has great application prospects in the fields of organic solvents and other types of wastewater treatment.

CO2 Capture Improvement in Polyetherimide Membranes: Effect of Ionic Liquid on the Molecular Mobility

The research described here was aimed at the development of polymeric membranes based on polyetherimide (PEI) containing the ionic liquid (IL) 1-butyl-2,3-dimethylimidazolium hexafluorophosphate ([BMMIM]PF6). The preparation of the PEI-based membranes was carried out via casting of solutions with the incorporation of the IL. The prepared membranes were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) for thermal and free volume properties. CO2 sorption and permeation properties were measured to evaluate the CO2 capture performance of the membranes. The fractional free volume (FFV) of the membranes was around 15%. The incorporation of IL increased the CO2 sorption capacity, promoting an increase of 330% in the solubility coefficient (KD) and resulted in a decrease of 96% in CO2 permeability when compared to the control membrane. The presence of IL in the PEI matrix significantly altered the structural and transport characteristics of the analyzed membranes, being efficient for CO2 capture, as they showed a high CO2 solubility and a decrease in CO2 permeation.

A comprehensive performance comparison on the impact of MOF-71, HNT, SiO2, and activated carbon nanomaterials in polyetherimide membranes for treating oil-in-water contaminants

The effective treatment of industrial oil/water emulsion before discharging into the receiving bodies is essential to prevent environmental pollution and its negative impacts on human health. The nanomaterial-incorporated nanocomposite membranes are touted as suitable candidates for removing oil contaminants from water. The selection of nanomaterial in nanocomposite membranes is crucial to fit the intended application. In this study, the performance of four different nanomaterials, i.e., metal-organic frameworks-71 (MOF-71), silicon dioxide (SiO2), activated carbon (AC), and halloysite nanotubes (HNTs), were used as the nanofiller of membranes. The resultant membranes were characterized by FESEM, AFM, water contact angle, and FTIR analysis. The membrane performance was examined in pure water flux (PWF) and oil/water emulsion rejection studies. The enhancement of PWF in SiO2, HNTs, MOF-71, and AC-based PEI/PVP composite membranes compared to neat PEI/PVP membranes was 33.33%, 59.25%, 70.37%, and 77.77%, respectively. The PEI/PVP/MOF-71 and PEI/PVP/AC membranes exhibited the best performance for PWF and oil/water rejection. Engine oil/water, hexane/water, and toluene/water % rejection of PEI/PVP/AC membrane was found to be 91.98%, 90.55%, and 93.74%, respectively, significantly higher than the neat PEI/PVP membrane. Furthermore, the nanomaterials-incorporated membrane showed better antifouling properties than the neat PEI/PVP membrane due to enhanced hydrophilicity. The MOF-71 and AC nanomaterials-based PEI membranes exhibited good oil/water emulsions separation due to their reliable adsorption capacity and improved fouling resistance than HNTs and SiO2 nanomaterials incorporated membranes, which could have a wide range of membrane-based water treatment applications.