Polyetherimide Membranes Research Articles

Controlled Covalent Functionalization of ZIF-90 for Selective CO2 Capture & Separation.

Mixed Matrix Membranes (MMM) with enhanced selectivity and permeability are preferred for gas separations. The porous metal-organic frameworks (MOFs) materials incorporated in them play a crucial part in improving the performance of MMM. In this study, Zeolitic imidazolate frameworks (ZIF-90) are selected to fabricate Polyetherimide (PEI) MMMs owing to their lucrative structural and chemical properties. This work reports new controlled post-synthetic modifications of ZIF-90 (50-PSM-ZIF-90) with ethanolamine to control the diffusion and uptake of CO2. Physical and chemical properties of ZIF-90, such as stability and presence of aldehyde functionality in the imidazolate linker, allow for easy modulation of the ZIF-90 pores and window size to tune the gas transport properties across ZIF-90-based membranes. Effects of these materials were investigated on the performance of MMMs and compared with pure PEI membranes. Performance of the MMMs was evaluated in terms of permeability of different gases and selective separation of CO2 and H2 gas. Results presented that the permeability of all membranes was in the following order, i.e., P(H2) > P(CO2) > P(O2) > P(CH4) > P(C2H6) > P(C3H8) > P(N2), demonstrating that kinetic gas diffusion is the predominant gas transport mode in these membranes. Among all the membranes, permeability of pure PEI membrane was highest for all gases due to the uniform porous morphology. The pure PEI membrane showed highest permeability of H2, which is 486.5 Barrer, followed by 49 Barrer for O2, 29 Barrer for N2, 142 Barrer for CO2, 41 Barrer for CH4, 40 Barrer for C2H6 and 39.6 Barrer for C3H8. Results also confirm the superiority of controlled PSM-ZIF-90-PEI membrane over the pure PEI and ZIF-90-PEI membranes in CO2 and H2 separation performance. The 50-PSM-ZIF-90 PEI membrane exhibited a 20% increase in CO2 separation from methane and a 26% increase over nitrogen compared to the ZIF-90-PEI membrane. The 50-PSM-ZIF-90 PEI membrane showed 15% more H2/O2 separation and 9% more H2/CH4 separation than ZIF-90 PEI membrane. Overall, this study represents the role of controlled PSM in enhancing the property of new materials like ZIF and its application in MMMs fabrication to develop a promising approach for the CO2 capture and separation.

Electrochemical quantification of atrazine-fulvic acid and removal through bismuth tungstate photocatalytic hybrid membranes

Herbicides such as atrazine and humus substances such as fulvic acid are widely used in agricultural sector. They can be traced in surface and groundwater around the agriculture field at concentrations beyond the approved limit due to their mobility and persistence. Bismuth-based photocatalysts activated by visible light are potential materials for removing various organic pollutants from water bodies. These photocatalysts can also be suitable candidates for developing a hybrid membrane with anti-fouling properties. In this study, Bi2WO6 nanoparticles were synthesized via the hydrothermal method and integrated into the cellulose acetate (CA), polyetherimide (PEI), polysulfone (PSF) and polyvinylidene fluoride (PVDF) polymers via physical blending approach. The hybrid membranes were then characterized by FTIR, XPS and FESEM to confirm the chemical bonding, chemical composition and surface morphology of Bi2WO6. Thus, the pure water flux of CA (35.6 L m−2 h−1), PEI (46.56 L m−2 h−1), PSF (6.84 L m−2 h−1), and PVDF (68.47 L m−2 h−1) hybrid membranes has significantly enhanced than the pristine CA, PEI, PSF and PVDF membranes. The significant rejection of atrazine-fulvic acid was observed with hybrid membranes in the order of CA (84.1%) > PVDF (72.7%) > PEI (47.8%) > PSF (37.2%), and these membranes have shown an excellent flux recovery ratio than pristine membranes. Further, electrochemical quantification studies were performed to analyze the removal efficiency of atrazine-fulvic acid from water. In this present work, GO-modified SPE was employed for electrochemical sensing studies. The resultant CA hybrid membrane achieved removal efficiency of 84.08% for atrazine. It was observed that the Bi2WO6 established strong bonding with CA, and PVDF membranes, thus showing a significant removal efficiency and FRR than other hybrid and pristine membranes.

Polyetherimide membrane with tunable porous morphology for safe lithium metal-based batteries

The separator is critical in ensuring the safety and improving the electrochemical performance of lithium metal batteries (LMBs). However, the weak thermal stability, common mechanical strength and the poor wettability towards electrolyte of the commercial polyolefin separator severely hamper its application in high-performance LMBs. Herein, a simple phase inversion technique could be used to design and scalably fabricate porous polyetherimide (PEI) membranes, which was used as LMB separators for the first time. The final morphology of PEI membranes can be finely tuned from finger-like voids to sponge-like pores by selecting an appropriate non-solvent. Combining experiments and density functional theory (DFT) simulations, it reveals that the optimal PEI membrane shows a sponge-like pore structure, which can induce the genuine deposition of the Li metal due to the homogeneously distributed pores in high density on the membrane and its good affinity towards the electrolytes. Consequently, the PEI based LMB show better performance than the commercial polypropylene (PP) based LMB. More importantly, the optimal PEI membrane shows a better mechanical strength and thermal stability than the PP membrane at the same thickness, which can ensure a higher safety for real applications. Since the non-solvent induced phase separation technique used to prepare PEI membrane is scalable in low cost, this work provides insightful route to overcome one of the main challenges, i.e. lack of high performance and high safety separator, for practical LMB application.

Ceramic Nanowire Coated Membrane As Thermally Stable Battery Separator

Separators play an important role in battery electrochemistry and safety. In general, a good separator is required to be both physically and chemically stable, avoiding unwanted reactions with strong oxidizing or reducing electrolytes near the cathode and anode surfaces, while maintaining mechanical strength avoiding failures despite the cyclic mechanical stresses during battery operation.[1] Separator is also needed to be wettable by the electrolyte and sufficiently porous to provide low resistance to ion transport and enable fast charging. Currently, most commercial separators based on polyolefin such as polyethylene (PE) and polypropylene (PP) are widely used in lithium-ion batteries (LIBs). However, polyolefin separators suffer from low heat resistance due to their low melting points (usually <160 ℃), which may cause safety concerns. In addition, they are not wetted well by all electrolytes and are often not designed for ultra-fast charging.Compared to PP or PE, polyetherimide (PEI) has a higher melting point (> 300 ℃). Porous PEI separator membranes can be fabricated via phase inversion method [2] to provide good ion conductivity and a higher heat resistance. Yet, the weak tensile/puncture strength could make it vulnerable towards mechanical damages during battery cycling. PEI also experiences severe shrinkage at high temperatures (>240 °C). To address these issues, we developed a facile and scalable strategy to incorporate a thin layer of ceramic nanowires on both surfaces of the PEI membrane. Heat resistance tests suggest our separators can survive high temperature up to 400 °C, as the coating minimized the shrinkage of the PEI. The inner polymer layer could melt at elevated temperatures, thus forming a shut-down layer between the ceramic layer to further enhance cell safety. These results indicate our nanowire coated separators can allow batteries to operate safely even at extremely high temperatures.

Fabrication and application of novel high strength sulfonated PVDF ultrafiltration membrane for production of reclamation water

Advanced treated water (ATW) produced in wastewater treatment facilities was assessed as an excellent alternative water resource that can be used as reclamation water, such as indirect and direct potable reuse. The development of cutting-edge technology for simple but best practices is essential for the reliable production of safe reclamation water from wastewater. This study prepared a novel high strength sulfonated polyvinylidene fluoride (HSPVDF) ultrafiltration membrane and investigated to produce ATW, and performances were compared to sulfonated PVDF (SPVDF) (which was prepared without thermal treatment) and bare PVDF. To compare the properties of HSPVDF to hydrocarbon polymer, the polyetherimide (PEI) and Sulfonated PEI (SPEI) membrane were prepared. HSPVDF showed excellent membrane morphology, porosity, MWCO, and hydrophilicity, resulting in higher pure water flux (712 ± 6 L m−2 h−1) antifouling properties (Rir 1.3% and FRR 98.6%) compared to PVDF. It is an interesting fact that the tensile strength of the HSPVDF (3.4 ± 0.2 MPa) tremendously increased (3 folders) when compere to PVDF (1.3 ± 0.1 MPa). The HSPVDF membrane showed good removal efficiency up to 96 ± 05% and 97 ± 09% rejection for bovine serum albumin (BSA) and humic acid (HA), respectively. The membrane application studies for wastewater treatment showed that the tertiary HSPVDF UF membrane filtration following the nutrient removal activated sludge (NRAS) process can produce reliable and economic performance (125 ± 2 L m−2 h−1, 0.25 ± 0.05 NTU, no pathogens), suggesting that it can be a best practice technique that can replace the complicated multi-staged tertiary processes to produce reclamation water.

Interfacially-confined polyetherimide tubular membranes for H2, CO2 and N2 separations

Capturing CO2 and H2 purification from gas mixtures such as CO2/N2 and H2/N2 are vital in addressing greenhouse gas emission abatement and global energy strategy. Here, we present a systematic investigation of tubular polyetherimide (PEI) membranes prepared by combining dip-coating and multilayer assembly techniques to target CO2 and H2 transports and CO2/N2 and H2/N2 selectivities. The effects of deposition cycle during dip-coating on H2, CO2 and N2 single gas permeations and binary gas separations were evaluated. The membranes prepared by three deposited layers produced gas permeances (10−12 mol m−2 s−1 Pa−1) of 310, 150 and 1 for H2, CO2 and N2 respectively, corresponding to CO2/N2 and H2/N2 permselectivities of 149 and 308. For binary gas mixture separation, an exclusive 100% CO2 and H2 permeate purity was observed irrespective of feed gas concentration. The PEI membrane exhibited a suppression of glass transition temperature and crystallinity compared to the bulk polymer indicating interfacial confinement phenomenon, which was further confirmed by X-ray diffraction and Raman spectroscopic analyses. Due to a subtle change of imide group conformation of the obtained membrane layer, it was inferred that an increase in the polymer amorphicity and interfacial confinement facilitated the exclusive H2 and CO2 transports without much affecting the N2 permeance.

Sorption and permeation study of polyetherimide/hydrophobic silica nanocomposite membrane for effective syngas (H2/CO/CO2) separation

This study aimed to fabricate and investigate the nanocomposite membrane made of polyetherimide (PEI) and hydrophobic fumed silica as filler. Commercial nanosilica (0–20 wt%) was embedded into PEI (Ultem1000) to prepare PEI/Silica dense nanocomposite membranes. Permeability and solubility of H2, CO, and CO2, as the main gases in syngas mixture, was investigated at 2–6 bar and 25 ± 1 °C. The effect of feed pressure (2–6 bar) on the gas permeability and solubility was studied for the pure and nanocomposite membranes. The membrane characterization was examined by FTIR, XRD, DSC, SEM, and EDX analysis. It revealed that in the low percentage of nanosilica, the permeability increased and the selectivity decreased, as the permeability of H2 increased from 1.08 to 1.63 barrer at 6 bar, while H2/CO and H2/CO2 decreased from 19.6 to 15 and from 3.8 to 3.6, respectively. The SEM and EDX images showed that by the increase in nanosilica loading, the silica particles dispersed more uniformly in the polymer matrix and formed membranes without any defect. For the nanocomposite membrane containing 20 wt% nanosilica, in comparison with pure PEI membrane, the H2/CO selectivity increased by almost 350% and reached 66.4, while H2 and CO permeability reduced by 21% and 77%, respectively. Solubility and diffusivity obtained through gas sorption measurement experiments, confirmed these outcomes, as the hydrogen diffusivity increased by an increase in nanosilica loading but CO and CO2 diffusivity decreased.

Performance Evaluation of PDMS or PEBAX-Coated Polyetherimide Membrane for Oxygen/Nitrogen Separation

Since the industrial revolution era, the Earth was suffering from serious air pollution. Millions of people are now suffering from indoor air pollution related diseases, especially in the industrialized countries such as China. One method to improve the indoor air quality is by oxygen enhancement. Membrane technology has been a key research over the past decades due to its low energy usage, minimum chemical consumption as well as small setting up layout. In this study, polyetherimide (PEI) membranes coated with polydimethylsiloxane (PDMS) or poly(ether block amide) (PEBAX) at different concentration (1, 3 or 5 wt%) were used to evaluate the oxygen/nitrogen gas separation. Prior to the gas permeation study, the membranes were characterized using scanning electron microscope (SEM) for morphology observation and surface elemental analysis by energy dispersive X-ray spectroscope (EDX). The morphology of the self-fabricated PEI membranes is composed of a thin and dense structure supported by the finger-like structure. The results obtained from oxygen/nitrogen separation studies shows membrane coated with 3 wt% PDMS yield a good separation results, exhibiting an improvement of oxygen and nitrogen permeance by 28.2% and 24.9%, selectivity by 10.4% (up to 5.08) relative to the base PEI membrane. Meanwhile, the 3 wt% PEBAX-coated PEI membrane only achieved selectivity of 3.56. The PDMS-coated PEI membrane yield a better separation performance attributed to the fact that PDMS coating on the hollow fiber membrane improve the surface morphology by reducing the defects.

Preparation of HKUST-1/PEI mixed-matrix membranes: Adsorption-diffusion coupling control of small gas molecules

HKUST-1 nanocrystals (50–80 nm) were homogeneously dispersed in a polyetherimide (PEI) polymer matrix. The use of a capping agent (sodium formate) prevented the agglomeration of HKUST-1 nanocrystals in the casting solution. The highly dispersed HKUST-1 nanocrystals were found to strengthen the interactions with the PEI and minimize the interfacial holes by providing more accessible Cu unsaturated metal sites for the CO bonds on the five-membered rings of the PEI matrix. The PEI membrane loaded with 30 wt % HKUST-1 nanocrystals (30-N-HKUST-1/PEI) showed a high H2 permeability (193.3 Barrer at 25 °C under 1.5 bar) and good ideal H2/CH4 and H2/CO2 selectivity factor of 101.7 and 20.6 in a single gas test, respectively. In the gas mixture test, it also showed a good separation performance, i.e., a H2/CH4 and H2/CO2 selectivity factor of 82.4 and 16.5 was measured, respectively. The 30-N-HKUST/PEI membrane was tested in a gas mixture at different temperatures (25–100 °C), different pressures (0–3 bar) and various time (5–72 h) to study the performance in more realistic conditions thus to be further considered in the separation of syngas.

Modification of porous polyetherimide hollow fiber membrane by dip-coating of Zonyl® BA for membrane distillation of dyeing wastewater.

Wetting and fouling have significantly affected the application of membrane distillation (MD). In this work, a dip-coating method was used for improving surface hydrophobicity of the polyetherimide (PEI) hollow fiber membrane. An air gap membrane distillation (AGMD) process was applied for treatment of the methylene blue (MB) solution. The porous PEI membrane was fabricated by a dry-wet spinning process and the hydrophobic 2-(Perfluoroalkyl) ethanol (Zonyl® BA) was used as the coating material. From FESEM, the modified PEI-Zonyl membrane showed an open structure with large finger-like cavities. The modified membrane displayed a narrow pore size distribution with mean pore size of 0.028 μm. The outer surface contact angle of the PEI-Zonyl membrane increased from 81.3° to 100.4° due to the formation of an ultra-thin coated layer. The pure water flux of the PEI-Zonyl membrane was slightly reduced compared to the pristine PEI membrane. A permeate flux of 6.5 kg/m2 h and MB rejection of 98% were found for the PEI-Zonyl membrane during 76 h of the AGMD operation. Adsorption of MB on the membrane surface was confirmed based on the Langmuir isotherm evaluation, AFM and FESEM analysis. The modified PEI-Zonyl membrane can be a favorable alternative for AGMD of dyeing wastewaters.

Performance studies of GO/PF127 incorporated Polyetherimide Ultrafiltration membranes for the rejection of oil from oil wastewater

Ultrafiltration Polyetherimide (PEI) polymeric membrane was modified by the incorporation of graphene oxide (GO) (0.2, 0.6 and 1 wt %) and PluronicF-127 (PF127) (1 wt %) using the phase inversion technique for synthetically produced oil-water separation. GO nanoparticles were prepared by the Hummers method and it was analyzed by FTIR, XRD, Raman, and TGA. ATR-FTIR is attributed to measure the functional groups in the prepared membrane. The effect of GO and PF127 loading on the prepared membranes was evaluated by SEM, AFM, viscosity, water uptake capacity, surface porosity, tortuosity, and pore radius. The contact angle measurements are performed to determine the hydrophilicity of the prepared membranes. The thermal and mechanical stability of prepared membranes is determined by TGA and mechanical test analyzer. The performances of prepared membranes were determined by permeability, rejection, and antifouling properties using crude oil as a feed solution. In the filtration performances, the membrane synthesized with composition PEI (17 wt %), PF127 (1 wt %) and GO (0.6 wt %) showed better rejection of 95% which ameliorates the flux of 266.5 L m−2 h−1 and also it bolster the flux recovery ratio of 93% with improved recyclability performance. The improved results were obtained by the modification of the PEI membrane matrix with the addition of highly hydrophilic synthesized GO nanoparticles, that produced an enhanced efficiency in the separation of oil wastewater.

Heparin immobilized graphene oxide in polyetherimide membranes for hemodialysis with enhanced hemocompatibility and removal of uremic toxins

Intermittent hemodialysis is a life-saving renal replacement therapy that removes excess water and uremic salts from patients who suffer from loss of kidney function. Hemocompatible polyetherimide membranes were fabricated by the incorporation of functionalized graphene oxide (f-GO). The f-GO was prepared by immobilizing heparin via the polydopamine anchor onto the nanosheets. The role of the f- GO in altering membrane morphology, surface roughness, wettability, porosity, and surface chemistry were evaluated in detail. The addition of f-GO suppressed the protein adsorption from platelet-poor plasma (>90%) lowered the adhesion (103 times)/activation of platelets, improved the blood clotting time (aPTT/TCT - ~235 s/58.5 s), decreased the thrombin generation and did not activate either complement pathways. Low aggregation of erythrocytes and <2% hemolysis ratio was another indication of improved membrane hemocompatibility. The cell proliferation of Chang liver cells on the f-GO incorporated membranes is an indication of low cytotoxicity of the prepared membranes. The modified hollow fiber membranes displayed exceptional capabilities compared to its pristine counterpart, evidenced by ~ four times higher ultrafiltration coefficient, outstanding removal of uremic toxins after 4 h (Urea- 77 ± 2.5%, creatinine- 68 ± 2% and Lysozyme 44 ± 2%) and ~95% retention of essential protein (albumin). No leaching of the f-GO could be observed from the membrane, and the prepared membranes were robust as they exhibited a sufficiently high solute removal (urea, creatinine, and phosphate) in the ex-vivo run using spiked goat blood. These preliminary investigations point to the fact that f-GO is a suitable modifier, and these membranes can be further explored for hemodialysis application.

DETAILED EVALUATION OF PERVAPORATION MODELING TO OBTAINING ANHYDROUS ETHANOL

Pervaporation requires operation at mild temperatures and provides low energy consumption, which makes this technology economically attractive. However, pervaporation is not yet a widespread process in the industry. One of the justifications is the complexity in the quantification of variables related to the membrane in the most diverse conditions. This factor results in the absence of generic models in the simulation software. This work aims at the rigorous phenomenological modeling of a pervaporation process using a polyetherimide membrane intended for the dehydration of ethanol. The model was developed on the Aspen Custom Modeler™ platform. Two approaches were implemented and compared: PERKAT and PERVAP models, being the last one the best model. The main variables of the process were evaluated. It was possible to verify the capacity of separation of the pervaporation module in breaking the barriers of the azeotrope, reaching a product with a high level of purity in ethanol, and recovery of up to 99.8%. In addition, the generic PERVAP model was exported to Aspen Plus™ and a cascade pervaporation unit was simulated. The specific energy consumption was calculated and compared to that of traditional separation processes. A 70% reduction was obtained compared to the most economical distillation configuration.

Enhanced Gas Separation Performance by Embedding Submicron Poly(ethylene glycol) Capsules into Polyetherimide Membrane

Recently, hollow filler as an emerging concept is attracting more attention in preparation of mixed matrix membranes (MMMs). Herein, poly(ethylene glycol) microcapsules (PMC) are synthesized via distillation precipitation polymerization and embedded into the polyetherimide (Ultem®1000) matrix to fabricate MMMs for CO2 capture. The PMC exhibits a preferential hollow structure within the Ultem matrix to furnish highways within membrane, and thus achieve high gas permeability. Meanwhile, the favorable affinity of poly(ethylene glycol) (PEG) microcapsule with ether oxygen group (EO) towards CO2 enhances the CO2 solubility selectivity. Such integration of physical and chemical microenvironments in the as-designed PEG microcapsule affords highly enhanced CO2 separation performance. Compared to pristine Ultem®1000, the membrane with 2.5 wt% PMC loading exhibits 310% increment in CO2 permeability and 22% increment in CO2/N2 selectivity, which shows the promising prospects of designing PEG-containing microcapsules as the filler of MMMs for CO2 capture.

Noncovalently Functionalized Sulfated Castor Oil-Graphene Oxide-Strengthened Polyetherimide Composite Membranes for Superior Separation of Organic Pollutants and Their Fouling Mitigation.

A novel sulfated castor oil (SCO)-graphene oxide (GO)-strengthened polyetherimide (PEI) membrane was prepared for the first time via phase inversion process for the efficient separation of multiple organic pollutants with superior long-term antifouling stability. X-ray diffraction, attenuated total reflectance-Fourier transfer infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and mechanical strength studies revealed that the SCO and GO were successfully incorporated into the PEI membrane with enhanced mechanical strength. The water flux of the PEI/SCO@GO membrane (410.6 L m-2 h-1) was about 50 times that of bare PEI (7.8 L m-2 h-1) and about 6 times that of PEI/SCO (64.5 L m-2 h-1) membranes. The surface hydrophilicity of the PEI/SCO@GO membrane was significantly increased in terms of the decrease of the water contact angle from 98.5° (bare PEI) to 40.4°. The PEI/SCO@GO membrane separation efficiency was found to be greater than 99.0%, particularly for both the oil-in-water emulsion and the humic acid solution, respectively. Because of the higher flux recovery ratio and the lower total fouling rate of the PEI/SCO@GO membrane, a comprehensive antifouling performance was observed during the long-term foulant filtration cycle analyses. Hence, the incorporation of both SCO and GO into the PEI matrix would render the highly hydrophobic PEI material as the suitable and desirable antifouling membrane toward the treatment of various organic foulants in wastewater.

Feasibility study of polyetherimide membrane for enrichment of carbon dioxide from synthetic biohydrogen mixture and subsequent utilization scenario using microalgae

Feasibility study of polyetherimide membrane for enrichment of carbon dioxide from synthetic biohydrogen mixture and subsequent utilization scenario using microalgae

Improvement in separation performance of PEI-based nanofiltration membranes by using L-cysteine functionalized POSS-TiO2 composite nanoparticles for removal of heavy metal ion

L-cysteine as an amino acid was used for the modification of glycidyl POSS in the synthesis of L-cysteine functionalized POSS, including carboxyl, hydroxyl, and diamine groups. Then, the synthesized nanoparticles were applied to fabrication of L-cysteine POSS-TiO2 composite nanoparticles. NF membranes were prepared from the incorporation of different concentrations of the synthesized composite nanoparticles into the polyether-imide (PEI) as the membrane matrix. The prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM) and atomic force microscope (AFM). Moreover, the separation performance of the NF membranes was examined by pure water flux (PWF) and the separation of Na2SO4, Pb(NO3)2, Cr(NO3)2 and Cu(NO3)2 aqueous solutions. The results showed the increase of pure water flux due to present hydrophilic groups on the membrane surface. The highest pure water flux obtained was 22.03 L/m2h in 1 wt% of nanoparticles. Furthermore, the rejection of Na2SO4 and Pb(NO3)2, CrSO4, and Cu(NO3)2 improved to 78%, 64%, 67% and 66% that increased 11%, 33%, and 22%, and 39% compared with the pristine PEI membrane, respectively. Finally, the best FRR% (81%) was obtained for 0.1 wt% of the composite nanoparticles (M3).

Minimizing Solvent Toxicity in Preparation of Polymeric Membranes for Gas Separation.

Toxic solvents such as dimethylformamide (DMF) are widely used for the preparation of polymeric membranes due to the strong dissolving power. Environmentally friendly solvents are available, but the developed membranes suffered from low performance due to the poor solubility of the polymer in the solvent. In this work, polyetherimide membranes were prepared using DMF with the addition of the biodegradable solvent γ-butyrolactone (GBL). Results show that mixing 75 wt % of DMF with 25 wt % GBL enhanced the membrane gas permeability toward hydrogen, methane, helium, carbon dioxide, and nitrogen. The overall permeability was increased by 9.6% compared to the permeability of the membrane made by 100 wt % DMF. Hydrogen-to-methane selectivity was also raised from 26.3 to 29.3.

New mixed matrix PEI nanofiltration membrane decorated by glycidyl-POSS functionalized graphene oxide nanoplates with enhanced separation and antifouling behaviour: Heavy metal ions removal

Surface functionalization of graphene oxide (GO) nanoplates was performed by glycidyl polyhedral oligosilsesquioxane (POSS), and was used to fabrication of polyetherimide (PEI) based nanofiltration membranes by phase inversion method. The prepared membranes characterized by Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray spectrometry (EDX) and atomic force microscopy (AFM) analysis. The effect of different concentrations of glycidyl POSS-GO (PG) in membrane matrix on separation performance and antifouling property of blended membranes was investigated by contact angle measurement, pure water flux, Na2SO4, Pb(NO3)2, CrSO4 and Cu(NO3)2 rejection and flux recovery ratio. The blended PEI/PG membranes showed significant separation performance and antifouling properties compared with neat PEI and PEI/GO membranes. The highest pure water flux measured 74.77 (L/m2·h) for the blended membrane with 0.001 wt% of PG whereas it was 51.06 (L/m2·h) for the PEI/GO membrane and 17.63 (L/m2·h) for pristine membrane at 4.5 bar pressure. The blended PEI/PG membranes showed outstanding Na2SO4 and Pb(NO3)2, CrSO4, and Cu(NO3)2 rejection compared to blended PEI/GO membranes and neat PEI ones. Furthermore, the highest flux recover ratio (FRR) value was obtained (96%) for the blended [PEI/0.1 %wt PG] membrane whereas FRR was (40%) for PEI/GO and (33%) for the neat PEI membranes.

Biomass derived carboxylated carbon nanosheets blended polyetherimide membranes for enhanced CO2/CH4 separation

The fillers/nanofillers combinations with ideal interfacial morphologies could adjust the performance of pristine polymeric membranes and enhance the gas separation performances. In this study, biomass-derived 2D carboxyl functionalized nanocarbon (nanosheets) were produced from pyrolysis of the rain/monkey pod tree (Samanea saman) leaves. The X-ray diffraction, Raman spectroscopy, and X-Ray photoelectron spectroscopy (XPS) confirmed the chemical structure and carboxyl functionalization of carbon nanosheets (CCNS). The carboxyl-functionalized nanosheets blended into polyetherimide (PEI) solutions was used to fabricate mixed matrix membranes (MMMs) through modified dry/wet phase inversion method using different wt. % [0.0%, 0.25%, 0.5% and 1.0% of CCNS] of fillers into the pristine PEI NMP solutions. Surface and cross-sectional micrographs discerned the defects and dispersion of CCNS into the polymer matrix. Finally, the transport properties of pure gases (CH4 and CO2) were evaluated using constant pressure/variable volume apparatus. The gas separation studies showed improved permeance and selectivity of MMMs [(PCO2 = 1.84 GPU, (α = CO2/CH4) = 42.73] than pristine PEI membranes [PCO2 = 1.29 GPU, (α = CO2/CH4) = 23.30] under identical conditions of pressure and temperature.