Carbon Nanotubes Mixed Matrix Membranes Research Articles

Polyvinylidene Fluoride/Nanoclays (Cloisite 30B and Palygorskite) Mixed Matrix Membranes with Improved Performance and Antifouling Properties

In this study, it was attempted to prove the effectiveness of nanoclays as economical and nontoxic nanofillers through comparison with carbon nanotubes (CNTs). Two hydrophilic nanoclays, namely, Cloisite 30B and palygorskite (PGS), were used as nanofillers to improve the morphology and performance of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes. A nonsolvent-induced phase separation (NIPS) method was used to prepare mixed matrix membranes (MMMs). The effects of the nanoclays on morphology, performance, and antifouling properties of the prepared MMMs were investigated. It was found that compared to PVDF membranes, the hydrophilicity, antifouling properties, and morphology of the fabricated MMMs are improved significantly. Compared to PVDF membranes, pure water flux (PWF) values of the MMMs containing the optimum contents of Cloisite 30B (0.5 wt %) and palygorskite (1 wt %) improved by 44.7 and 61.7%, respectively. Acid-treated CNTs were used as a reference additive, and the performance and antifouling properties of the prepared PVDF/nanoclay MMMs were compared with the prepared PVDF/acid-treated CNT MMMs. It was found that the PWF values of the MMM containing optimum contents of PGS and Cloisite 30B nanoclays are 86 and 77%, respectively, compared with that of the MMM containing acid-treated CNTs. The PVDF/Cloisite 30B MMM exhibited lower PWF than the PVDF/PGS MMM, which could be attributed to the plate-like structure of Cloisite 30B. Also, the flux recovery ratio (FRR) values of the mixed matrix membranes containing optimum contents of PGS and Cloisite 30B nanoclays were 95.65 and 92.06%, respectively, compared to that of the MMM containing acid-treated CNTs. Also, the BSA rejections of the prepared MMMs containing optimum contents of Cloisite 30B and palygorskite were comparable with that of the MMM containing acid-treated CNTs. Therefore, nanoclays can be suggested as economical and ecofriendly nanofillers for improving the PVDF membrane performance.

Blend cellulose acetate butyrate/functionalised multi-walled carbon nanotubes mixed matrix membrane for enhanced CO2/N2 separation with kinetic sorption study

Abstract The significant breakthroughs of the membrane technology, specifically the blend mixed matrix membrane (MMM) has revealed a promising carbon dioxide (CO2)/nitrogen (N2) separation performance. In this study, the blend MMMs were prepared by incorporating the functionalised multi-walled carbon nanotubes (MWCNTs-F) as inorganic dispersant into the CAB blend polymer matrix. The blend MMMs were fabricated by blending CAB at molecular weight (Mn) of 70,000 with CAB Mn of 12,000 (M1), 30,000 (M2) and 65,000 (M3). It was found that M2 presented the highest CO2/N2 selectivity of 17.09 ± 1.29 with a CO2 permeance of 341.15 ± 1.19 GPU. The high CO2 permeance for M2 was subsequently a result of the compatible combination between the CAB polymers (Mn of 70000:30000). The blending of CAB polymers demonstrated enhanced functional groups and lowered the chain spacing of the blend MMM. Moreover, through the kinetic sorption study M2 was capable of achieving a moderate solubility coefficient of 7.58 × 1012 cm3 (STP)/cm4 cmHg. In addition, M2 was able to achieve a composition selectivity of 7.85 ± 1.48 from the binary gas permeation study with a feed composition of 50:50 for CO2/N2. From this study, the newly synthesised blend MMM proved to possess excellent CO2/N2 separation performance and revealed that an effective selection of polymer at different molecular weights plays an important role in the fabrication of the blend MMM.

Bis(phenyl)fluorene-based polymer of intrinsic microporosity/functionalized multi-walled carbon nanotubes mixed matrix membranes for enhanced CO2 separation performance

Polymers of intrinsic microporosity (PIM) as one of potential next generation membrane materials for gas separation has attracted great interests due to its ultra-permeable characteristics. Herein, a novel bis(phenyl)fluorene-based PIMs (Cardo-PIM-1) based on 9,9-bis(3,4-dihydroxyphenyl) fluorene (BDPF), 2,3,5,6-tetrafluoroterephthalonitrile (TFTPN) and spirocyclic 5,5′,6,6′-tetrahydroxy-3,3′,3,3′-tetramethylspirobisindane (TTSBI) were prepared vis dibenzodioxane polymerization reaction, and then the functionalized multi-walled carbon nanotubes (f-MWCNTs) were incorporated into Cardo-PIM-1 to fabricate mixed matrix membranes (MMMs) with solution mixing method for CO2 separation. The structure analysis indicated that the MWCNTs were cut into short ropes and the amino groups were incorporated into the nanotubes surface after treated with acid mixtures followed by ethylenediamine modification. FTIR spectroscopy and nuclear magnetic resonance (NMR) measurement confirmed the formation of Cardo-PIM-1 macromolecule. BET and positron annihilation lifetime spectroscopy (PALS) analysis exhibited that Cardo-PIM-1 contained larger pore-size distribution and fractional free volume (FFV), and preferential CO2 adsorption capacity over N2 compared with that of PIM-1. This work investigated the structure of polymer as well as the effect of nanofillers in the gas separation performance. High CO2 permeability of 2.9 × 104 Barrer with a desirable CO2/N2 separation factor of 24.2 was achieved using the MMMs with 7.5 wt% f-MWCNTs loading, which were among the best performance for CO2 separation. The Cardo-PIM-1/f-MWCNTs MMMs will provide a promising alternative in industrial flue gas separation and CO2 capture process.

Surface modification of functionalized multiwalled carbon nanotubes containing mixed matrix membrane using click chemistry

Surface modification of mixed matrix membranes is especially challenging because functional groups on the surface are not precisely known. This study describes a novel concept of modification of the membrane surface by the reaction of the azide functionalized multiwalled carbon nanotubes mixed matrix membranes of polyether sulfone. The surface azide groups were reacted with terminal alkyne 1-pentyne, using the Cu(I) catalyzed [3 + 2] Huisgen cycloaddition. XPS confirmed the presence of the triazole group, typical of the ‘click reaction’, on the surface of the membrane. The surface hydrophilicity, wettability and water permeability were enhanced in the modified membrane. The water flux of the surface modified membrane increased reaching a maximum of 331.2 L/m2 h, while the rejection performance for heavy metals was comparable to the unmodified membrane. The BSA adsorption of the surface modified triazole containing membrane was considerably reduced, indicating an enhanced surface hydrophilicity. Surface hydrophilicity and porous structure of the membrane are factors for improved membrane performance and limiting the protein adsorption which indicates an enhanced fouling resistance.

Effect of Ethylene Oxide Functional Groups in PEBA-CNT Membranes on CO2/CH4 Mixed Gas Separation

Poly (ether-block-amide) /poly (ethylene glycol)/ carbon nanotubes mixed matrix membranes have been successfully fabricated using solvent evaporation method to determine the effect of ethylene oxide groups on the performance of produced membranes. The effects of CNTs (2-8 wt%) and PEG (up to 50 wt%)were investigated in both single and mixed gas test setup in different temperature and pressure. Finally the membranes were structurally characterized using Scanning Electron Microscopy, X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, and Atomic Force Microscopy.Results showed that addition of carbon nanotubes enhanced the gas separation performance of membranes and presences of ether groups in poly ethylene glycol improved the CO2 permeability. Membrane containing 8 wt % carbon nanotubes and 50 wt % poly ethylene glycol showed the best performance with CO2/CH4 selectivity of 45 and CO2permeability of 302 at pressure of 14 bars. Also, mixed gas permeation experiments were carried out and results showed dramatic decrease in CO2 selectivity due to membrane plasticizing. The permeability of CO2 in mixed gas test for membrane containing 50 wt% pol ethylene glycol and 8 wt% was 193 with CO2/CH4 selectivity of 19 in room temperature. Furthermore, membranes produced by 6 and 8 wt% carbon nanotubes and 50 wt% poly ethylene glycol placed above Robeson’s trade-off line. The effect of temperature on performance of fabricated membrane was finally investigated. Results showed an increase in permeability and decrease in selectivity for all membranes.

Removal of lead ions from polyether sulfone/Pb(II)-imprinted multi-walled carbon nanotubes mixed matrix membrane

In this study, ethylene diamine (EDA) was grafted on carboxyl-modified multi-walled carbon nanotubes (MWNTs-COOH) to obtain amino-functionalized MWNTs (MWNTs-NH2). Pb(II)-imprinted MWNTs was prepared by using MWNTs-NH2 via lead ion-imprinted technology to improve the selective adsorption of MWNTs to lead ions. Pb (II)-imprinted MWNTs were incorporated in polyether sulfone (PES) matrix to prepare PES/Pb (II)-imprinted MWNTs mixed matrix membranes (MMMs) by phase separation process. The hydrophilicity and antifouling property of pure PES membrane was improved by incorporating Pb(II)-imprinted MWNTs. Pb(II)-imprinted MWNTs and PES/Pb (II)-imprinted MWNTs MMMs possessed higher adsorption to lead ions than other metal ions, as well as showed selective adsorption to lead ions in the mixed solution including four different metal ions such as Pb2+, Zn2+, Co2+ and Ca2+. The results provided new insights for the removal of lead ions by MMMs embedded with Pb(II)-imprinted MWNTs with high recovery.

Fabrication of polyimide and functionalized multi-walled carbon nanotubes mixed matrix membranes by in-situ polymerization for CO 2 separation

Abstract Mixed matrix membranes (MMMs) consisting of acid-treated functionalized multi-walled carbon nanotubes (MWCNTs) incorporated into polyimide (PI) polymer were fabricated for gas separation. The functional groups and dispersion properties of the MWCNTs were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed that the functionalized MWCNTs were cut into short ropes and acid oxidation introduced oxygen containing functional groups such as hydroxyl (OH) and carboxylic acid (COOH) on the surface of MWCNTs. Based on the assumption of strong interfacial interactions between the functionalized MWCNTs and PI matrix, the MWCNTs were first incorporated into poly(amic acid) (PAA) to form a highly dispersed solution, then the PI/MWCNTs nanocomposites were formed after in-situ chemical imidization. Scanning electron microscopy (SEM) indicated that the functionalized MWCNTs were dispersed homogenously in the PI matrix. The gas separation performance showed that the CO2 permeability coefficient increased 292% at 3 wt.% MWCNTs incorporated into the MMMs, and there was a 145% increase in the selectivity of CO2/N2 and a 144% increase in the selectivity of CO2/CH4. This result demonstrates that the carboxylic and hydroxyl groups have a strong interaction with CO2, which increases the solubility coefficient of the polar gases. The in-situ polymerization approach of fabricated MMMs improves the interfacial interaction between the dispersed nanomaterials and the polymer matrix, which can be utilized in the practical gas separation technology.

The novel Elvaloy4170/functionalized multi-walled carbon nanotubes mixed matrix membranes: Fabrication, characterization and gas separation study

This is the first report of gas transport properties of polymer Elvaloy4170. Elvaloy4170 is a commercially available polymer, which has very low price and good mechanical properties. In this work, mixed matrix membranes (MMMs) were fabricated by embedding the multi-walled carbon nanotubes (MWNTs) into Elvaloy4170. Additionally, the effects of functionalization of the nanotubes with acid treatment and their loadings were evaluated on morphology and gas permeation properties of the membranes. The fabricated membranes were characterized by Raman spectroscopy, field emission scanning electron microscopy (FESEM) and differential scanning calorimeter (DSC). Moreover, the effects of filler loading and feed pressure (from 2 to 6 bar) on CO2/CH4 transport properties were considered in pure gas experiment. The gas permeability results of Elvaloy4170 membrane revealed that with increasing the pressure from 2 to 6 bar, CO2 permeability and CO2/CH4 selectivity increased 30% and 14%, respectively. Furthermore, compared to neat membrane, the MMM with 1 wt.% of f-MWNTs increased CO2 and CH4 permeabilities by 30% and 40%, respectively. In addition, it was found that the CO2/CH4 selectivity increased as the content of f-MWNTs increased from 1 wt.% to 4 wt.% in the polymer matrix. Finally, this study reveals that membranes fabricated from commercial polymer Elvaloy4170 were permeable and have the great potential to be applied for other gas separation membrane applications. Besides, due to the considerable reactivity of the epoxide group of Elvaloy4170, it tends to take part in chemical reactions and form covalent bond with functionalized groups to construct more efficient MMMs.

Erratum to: Functionalized carbon nanotubes mixed matrix membranes of polymers of intrinsic microporosity for gas separation.

Erratum to: Functionalized carbon nanotubes mixed matrix membranes of polymers of intrinsic microporosity for gas separation.

Gas separation properties of poly(amide-6-b-ethylene oxide)/amino modified multi-walled carbon nanotubes mixed matrix membranes

Amino modified multi-walled carbon nanotubes (MWNTs-NH2) were incorporated into poly(amide-6-b-ethylene oxide) (Pebax 1657) to prepare mixed matrix membranes (MMMs). The permeation properties of CO2, N2, CH4 and H2 were studied and the physical properties of Pebax/MWNTs-NH2 MMMs were characterized by X-ray diffractometer (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The incorporation of MWNTs-NH2 increased the amorphous region of Pebax phase in Pebax/MWNTs-NH2 MMMs, which was beneficial for the improvement of gas permeabilities. The apparent activation energy for permeation (Ep) for CO2 decreased with the increase of pressure, while those for N2, CH4 and H2 almost did not change. The Ep for CO2, N2, CH4 and H2 slightly decreased with the incorporation of MWNTs-NH2. Compared with pristine Pebax membrane, CO2 permeability increased almost 3 times for Pebax/MWNTs-NH2 MMMs with 33wt% MWNTs-NH2. With the increase of MWNTs-NH2 content, the normalized permeabilities of N2, CH4 and CO2 showed almost the same increment and the selectivities of CO2/N2, CO2/H2 and CO2/CH4 remained constant, which were consistent with the Maxwell model prediction. Thus, the incorporation of MWNTs-NH2 significantly improved the gas permeation properties of Pebax/MWNTs-NH2 MMMs.

SurfaceModification of Carbon Nanotubes Using Acid Treatment to Enhance Gas Separation Performance of Hybrid Nanocomposite Mixed Matrix Membrane

Recently, many researchers have explored the idea of hybrid mixed matrix membranes. Membrane separation processes based on hybrid mixed matrix membrane comprising inorganic material such as zeolite and carbon nanotubes (CNTs) embedded in polymer matrix have become one of the emerging technologies and extensively discussed in membrane separation literature. The present study is performed primarily to investigate the effect of chemical modification on carbon nanotubes surface towards gas separation performance of mixed matrix membrane. Polyethersulfone (PES)-carbon nanotubes mixed matrix membrane for modified and unmodified carbon nanotubes were casted using dry/wet phase inversion technique. The modified carbon nanotubes were prepared by treating the carbon nanotubes with acid treatment to allow PES chains to be attached to carbon nanotubes surface. The results of FESEM, DSC and FTIR analysis confirmed that chemical modification on carbon nanotubes surface had taken place. Meanwhile, the nanogaps in the interface of polymer and carbon nanotubes were appeared in the PES mixed matrix membrane with unmodified of carbon nanotubes. The modified carbon nanotubes mixed matrix membrane increases the mechanical properties, the productivity and purity of gas mixture compare to neat PES and unmodified carbon nanotubes mixed matrix membrane. For PES-modified carbon nanotubes mixed matrix membrane the maximum selectivity achieved for CO /CH are 24 32.59.

Enhanced biogas separation performance of nanocomposite polyethersulfone membranes using carbon nanotubes

This study is performed primarily to investigate the effect of chemical modification on carbon nanotubes surface towards biogas purification performance of mixed matrix membrane. In this study, polyethersulfone (PES)-carbon nanotubes mixed matrix hollow fiber membrane for modified and unmodified carbon nanotubese were spun using dry/wet spinning technique. The modified carbon nanotubes were prepared by treating the carbon nanotubes with acid treatment to allow PES chains to be attached on carbon nanotubes surface. The results from the FESEM, DSC and FTIR analysis confirmed that chemical modification on carbon nanotubes surface had taken place. Meanwhile, the nanogaps in the interface of polymer and carbon nanotubes were appeared in the PES mixed matrix membrane with unmodified of carbon nanotubes. The modified carbon nanotubes mixed matrix membrane increases the mechanical properties, the productivity and purity of biogas compare to neat PES and unmodified carbon nanotubes mixed matrix membrane. For PES-modified carbon nanotubes mixed matrix membrane the maximum selectivity achieved for CO 2 /CH 4 is 32.59.

Functionalized carbon nanotubes mixed matrix membranes of polymers of intrinsic microporosity for gas separation

The present work reports on the gas transport behavior of mixed matrix membranes (MMM) which were prepared from multi-walled carbon nanotubes (MWCNTs) and dispersed within polymers of intrinsic microporosity (PIM-1) matrix. The MWCNTs were chemically functionalized with poly(ethylene glycol) (PEG) for a better dispersion in the polymer matrix. MMM-incorporating functionalized MWCNTs (f-MWCNTs) were fabricated by dip-coating method using microporous polyacrylonitrile membrane as a support and were characterized for gas separation performance. Gas permeation measurements show that MMM incorporated with pristine or functionalized MWCNTs exhibited improved gas separation performance compared to pure PIM-1. The f-MWCNTs MMM show better performance in terms of permeance and selectivity in comparison to pristine MWCNTs. The gas permeances of the derived MMM are increased to approximately 50% without sacrificing the selectivity at 2 wt.% of f-MWCNTs' loading. The PEG groups on the MWCNTs have strong interaction with CO2 which increases the solubility of polar gas and limit the solubility of nonpolar gas, which is advantageous for CO2/N2 selectivity. The addition of f-MWCNTs inside the polymer matrix also improved the long-term gas transport stability of MMM in comparison with PIM-1. The high permeance, selectivity, and long term stability of the fabricated MMM suggest that the reported approach can be utilized in practical gas separation technology.

Increasing the Performance of PES-CNTs Mixed Matrix Membrane using Carbon Nanotubes (CNTs) Functionalization

A new type of mixed matrix membrane consisting of functionalized carbon nanotubes (CNTs) and polyethersulfone (PES) is prepared for biogas purification. PES mixed matrix membrane with and without modification of carbon nanotubes were prepared by a dry/wet phase inversion technique using a pneumatically flat sheet membrane casting machine system. The modified carbon nanotubes were prepared by treating the carbon nanotubes with chemical modification using Dynasylan Ameo (DA) silane agent to allow PES chains to be grafted on carbon nanotubes surface. The results from the FESEM, DSC and FTIR analysis confirmed that chemical modification on carbon nanotubes surface had taken place. Meanwhile, the nanogaps in the interface of polymer and carbon nanotubes were appeared in the PES mixed matrix membrane with unmodified of carbon nanotubes. The modified carbon nanotubes mixed matrix membrane increases the mechanical properties, the productivity and purity of biogas. For PES-modified carbon nanotubes mixed matrix membrane the maximum selectivity achieved for CO2/CH4 is 36.78

The Uses of Carbon Nanotubes Mixed Matrix Membranes (MMM) for Biogas Purification

A new type of mixed matrix membrane consisting of polyethersulfone (PES) and carbon nanotubes (CNTs) is prepared for biogas purification application. PES mixed matrix membrane with and without modification of carbon nanotubes were prepared by a dry/wet phase inversion technique using a pneumatically membrane casting machine system. The modified carbon nanotubes were prepared by treating the carbon nanotubes with chemical modification using acid treatment to allow PES chains to be grafted on carbon nanotubes surface. The results from the FESEM, DSC and FTIR analysis confirmed that chemical modification on carbon nanotubes surface had taken place. Meanwhile, the nanogaps in the interface of polymer and carbon nanotubes were appeared in the PES mixed matrix membrane with unmodified of carbon nanotubes. The modified carbon nanotubes mixed matrix membrane increases the mechanical properties and the permeability of all gases. For PES-modified carbon nanotubes mixed matrix membrane the maximum selectivity achieved for CO2/CH4 is 23.54.

CO2 Removal from Biogas Using Carbon Nanotubes Mixed Matrix Membranes

A new type of mixed matrix membrane consisting of polyethersulfone (PES) and carbon nanotubes (CNTs) is prepared for biogas purification application. PES mixed matrix membrane with and without modification of carbon nanotubes were prepared by a dry/wet phase inversion technique using a pneumatically membrane casting machine system. The modified carbon nanotubes were prepared by treating the carbon nanotubes with chemical modification using acid treatment to allow PES chains to be grafted on carbon nanotubes surface. The results from the FESEM, DSC and FTIR analysis confirmed that chemical modification on carbon nanotubes surface had taken place. Meanwhile, the nanogaps in the interface of polymer and carbon nanotubes were appeared in the PES mixed matrix membrane with unmodified of carbon nanotubes. The modified carbon nanotubes mixed matrix membrane increases the mechanical properties and the permeability of all gases. For PES-modified carbon nanotubes mixed matrix membrane the maximum selectivity achieved for CO 2/ CH 4 is 23.54

The Effect of Functionalization Carbon Nanotubes (CNTs) on the Performance of PES-CNTs Mixed Matrix Membrane

A new type of mixed matrix membrane consisting of functionalized carbon nanotubes (CNTs) and polyethersulfone (PES) is prepared for biogas purification. PES mixed matrix membrane with and without modification of carbon nanotubes were prepared by a dry/wet phase inversion technique using a pneumatically flat sheet membrane casting machine system. The modified carbon nanotubes were prepared by treating the carbon nanotubes with chemical modification using Dynasylan Ameo (DA) silane agent to allow PES chains to be grafted on carbon nanotubes surface. The results from the FESEM, DSC and FTIR analysis confirmed that chemical modification on carbon nanotubes surface had taken place. Meanwhile, the nanogaps in the interface of polymer and carbon nanotubes were appeared in the PES mixed matrix membrane with unmodified of carbon nanotubes. The modified carbon nanotubes mixed matrix membrane increases the mechanical properties, the productivity and purity of biogas. For PES-modified carbon nanotubes mixed matrix membrane the maximum selectivity achieved for CO 2 /CH 4 is 36.78