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Article

Study on the Performance of Cellulose Triacetate Hollow Fiber Mixed Matrix Membrane Incorporated with Amine-Functionalized NH2-MIL-125(Ti) for CO2 and CH4 Separation

by
Naveen Sunder
1,2,
Yeong-Yin Fong
1,2,*,
Mohamad Azmi Bustam
1,3 and
Woei-Jye Lau
4
1
Department of Chemical Engineering, Universiti Teknologi PETRONAS, Seri Iskandar 32610, Perak, Malaysia
2
CO2 Research Center (CO2RES), R&D Building, Universiti Teknologi PETRONAS, Seri Iskandar 32610, Perak, Malaysia
3
Centre of Research in Ionic Liquids (CORIL), Universiti Teknologi PETRONAS, Seri Iskandar 32610, Perak, Malaysia
4
Advanced Membrane Technology Research Centre (AMTEC), Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia, Skudai 81310, Johor, Malaysia
*
Author to whom correspondence should be addressed.
Separations 2023, 10(1), 41; https://doi.org/10.3390/separations10010041
Submission received: 5 December 2022 / Revised: 15 December 2022 / Accepted: 19 December 2022 / Published: 9 January 2023
(This article belongs to the Special Issue Membrane Preparation and Application for Separations and Water Treatment)
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Abstract

:
The increase in the global population has caused an increment in energy demand, and therefore, energy production has to be maximized through various means including the burning of natural gas. However, the purification of natural gas has caused CO2 levels to increase. Hollow fiber membranes offer advantages over other carbon capture technologies mainly due to their large surface-to-volume ratio, smaller footprint, and higher energy efficiency. In this work, hollow fiber mixed matrix membranes (HFMMMs) were fabricated by utilizing cellulose triacetate (CTA) as the polymer and amine-functionalized metal-organic framework (NH2-MIL-125(Ti)) as the filler for CO2 and CH4 gas permeation. CTA and NH2-MIL-125(Ti) are known for exhibiting a high affinity towards CO2. In addition, the utilization of these components as membrane materials for CO2 and CH4 gas permeation is hardly found in the literature. In this work, NH2-MIL-125(Ti)/CTA HFMMMs were spun by varying the air gap ranging from 1 cm to 7 cm. The filler dispersion, crystallinity, and functional groups of the fabricated HFMMMs were examined using EDX mapping, SEM, XRD, and FTIR. From the gas permeation testing, it was found that the NH2-MIL-125(Ti)/CTA HFMMM spun at an air gap of 1 cm demonstrated a CO2/CH4 ideal gas selectivity of 6.87 and a CO2 permeability of 26.46 GPU.

1. Introduction

With the global energy demand expected to increase by 3% in 2022 after its decline in 2020 due to the COVID-19 pandemic, the use of fossil fuels still maintains as the main supplying source for energy [1,2]. Consequently, this leads to a rise in global CO2 emissions to 38.0 Gt CO2, with fossil fuels contributing a 0.6% increase in CO2 emissions [3]. Although the purification of natural gas contributes to the rise in CO2 emissions, it is still considered as the cleanest form of energy among fossil fuels [4]. With nearly 37 Tcf of sour natural gas, Malaysia’s gas fields remain undeveloped due to the presence of a high content of acidic gas which mainly consists of CO2 [5]. For example, in Sarawak, the gas fields show CO2 contents of up to 87% [6]. Moreover, gas pipeline specifications only allow the presence of small quantities of CO2 because the existence of a high amount of acidic gases will create problems for gas production financially and operationally [7]. Therefore, the removal of CO2 from natural gas is mandatory.
Since the past decade, several technologies have been reported and implemented in gas processing industries to reduce the acid gas composition in sour natural gas. These include cryogenic distillation, amine adsorption, pressure swing adsorber, and temperature swing adsorber. However, these technologies suffer certain drawbacks such as high energy consumption, high carbon footprint production, high capital, and regeneration cost [8,9,10,11]. Thus, membranes for gas separation have gained popularity due to their advantages over the aforementioned technologies.
Membranes act as a semipermeable barrier that only allows certain molecules to pass through while restricting the penetration of other particles Membrane technologies have been utilized in various industrial applications such as wastewater treatment and gas separation [12]. Furthermore, membrane technologies offer several advantages over other separation technologies such as ease of operability, low footprint, cost-effectiveness, and low energy consumption [13]. With such advantages, membrane technologies have managed to attract considerable attention in recent years. However, membranes face challenges that include fouling, structural integrity, and most importantly, the tradeoff between permeability and selectivity [14]. Despite that, membranes are able to be fine-tuned by optimizing the materials used and the configurations applied to minimize or overcome the limitations faced by conventional flat-sheet membranes.
There are several types of materials that can be used for natural gas sweetening, most commonly polymeric, inorganic, metal-organic frameworks (MOFs), and mixed matrix membranes (MMMs) [15]. The most widely commercialized type of membrane is polymeric membranes, which have constantly undergone improvements to increase their CO2 permeability and selectivity. However, polymeric membranes have a key limitation, which is the tradeoff between permeability and selectivity as illustrated by the Robeson’s upper limit bound [16,17]. Polymeric membranes can be made from materials such as cellulose acetate, polysulfone, polyimide, and poly(ethyleneimine) [16]. Notably, cellulose acetate (CA) is a popular type of polymeric membrane used in various industries [18]. CA exhibited a CO2 permeability of 6.0 Barrer and a CO2/CH4 selectivity of 29 at a temperature and pressure of 35 °C and 27 kPa, respectively [19]. On the other hand, cellulose triacetate (CTA) demonstrated a higher affinity towards CO2 compared to CH4, which may result in greater gas separation capabilities despite being nearly chemically identical to CA but with a higher degree of hydrophobicity [20]. Furthermore, CTA is preferable compared to other polymers due to its low cost, ease of availability, and good mechanical and chemical stability [21]. It is noteworthy that the higher degree of acetylation of CTA exhibits higher CO2 permeability with lower CO2/CH4 selectivity [22].
Metal-organic frameworks (MOFs) are an innovative type of unique hybrid between organic and inorganic materials with an exceptionally high surface area and flexibility in pore size, shape, and structure [23,24,25,26,27,28,29,30]. The drawback of using a pure MOF film membrane for gas separation is the weak membrane–substrate bonding due to low adhesion forces which cause cracks and defects the formation on the membrane during drying or thermal activation [31,32]. To counteract the disadvantages of the polymeric and MOF-type membranes, MMMs are utilized as they provide the benefits of both organic and inorganic materials, with the polymer acting as a continuous phase and the filler serving as the dispersed phase. The frequently used fillers for MMMs fabrication include MOFs [29,33], zeolites [34], carbon [35], and metal oxides [36]. MOFs such as ZIF-8 [37,38], NH2-UiO-66(Zr) [39,40], NH2-MOF-199 [41], and NH2-MIL-125(Ti) [42] are among the most commonly researched fillers for the fabrication of MMMs in recent studies with high gas separation potential. The material selection for MOFs is crucial based on their purpose, pore size, and shape in order to ensure the desired separation performance [43]. In addition, amine-functionalized NH2-MIL-125(Ti) that contains octa-nuclear Ti-clusters can form a relatively cubic tetragonal structure arranged by 2-amino-1,4-benzenedicarboxylate ligands. Amine functionalization of the MOF allows facilitated diffusion to occur between the CO2 gas molecule and the NH2 carrier through reversible chemical reactions, therefore allowing CO2 to have a higher capture rate [44].
In a recent study reported by Mehmood et al. [45], the incorporation of a 0.4 wt% gamma-cyclodextrin (γ-CD) MOF into CA polymer was performed to fabricate a CA/γ-CD MMM with a CO2/CH4 selectivity of 38.49 with a CO2 permeability of 17 barrer. By comparison, pure CA obtained a CO2/CH4 selectivity of 1.9 with a CO2 permeability of 19 barrer. They concluded that the glassy nature of CA results in a decrease in CO2 permeability but an increase in CO2/CH4 selectivity when CA is used for MMM fabrication. Moreover, Saneeepur et al. [46] fabricated novel ion-exchanged zeolite (Co(II)-NaY)/CA MMMs at various loadings for CO2/N2 separation. Their research found that 15 wt% of Co(II)-NaY was an optimal loading in the CA matrix, which demonstrated a 43.9% and 14.5% CO2 gas permeation and CO2/N2 selectivity improvement, respectively, compared to the neat CA membrane, which resulted in a CO2 permeability of 3.28 barrer and a CO2/N2 selectivity of 29.2.
On the other hand, substituting a flat sheet membrane configuration with the industrially preferred hollow fiber configuration provides various benefits, For example, an increase in surface area to volume ratio due to it being cylindrical, and thus an increase in the gas penetration through the membrane [47]. HFMMMs have the potential to increase the membrane performance further, provided that the materials selected are compatible to prevent particle agglomeration, which could potentially deteriorate the performance of the membrane [44].
In this work, NH2-MIL-125(Ti) filler is incorporated into CTA polymer to form NH2-MIL-125(Ti)/CTA HFMMMs which are fabricated using a dry-wet phase inversion method. Neat CTA HFMs are also fabricated and used as a benchmark for the overall gas permeation process. The permeation of CO2 and CH4 gas and the CO2/CH4 gas pair selectivity of the resultant membranes at a fixed pressure and temperature are assessed. In addition, characterization studies using energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR), are conducted to analyze the filler dispersion, morphology, crystallinity, and functional groups of the resultant membranes.

2. Materials and Methods

2.1. Materials

Cellulose triacetate (CTA, d = 1.3 g/cm3, purity > 99.99%) and polydimethylsiloxane (PDMS, d = 95 g/mL3, purity > 99.99%) were acquired from ACROS Organics (Malaysia). Methanol (purity > 99.9%), N-methyl-2-pyrrolidone (NMP, purity > 99.8%), and n-hexane (purity > 99.99%) were obtained from Merck.

2.2. CTA HFM and NH2-MIL-125(Ti)/CTA HFMMM Fabrication

The fabrication of CTA HFMs and NH2-MIL-125(Ti)/CTA HFMMMs was conducted using a dry-wet phase inversion method. The NH2-MIL-125 MOF filler was synthesized based on the method reported in our previous work [42]. A vacuum oven set at 60 °C was used to dry the CTA pellets overnight. CTA/NMP dope solution with a pre-determined critical concentration of 13 wt% was then prepared. The CTA pellets were added to the NMP solution and continuously stirred overnight until they completely dissolved. The NH2-MIL-125(Ti)/CTA HFMMM with 1% filler loading was fabricated by firstly preparing a CTA/NMP solution and a NH2-MIL-125(Ti)/NMP suspension which were separately stirred overnight. The suspension was then added periodically into the CTA/NMP solution, and the final dope solution was further stirred overnight.
The bore fluid, NMP/DI water (90%/10%) solution was then prepared and pumped at 0.33 mL/min during the spinning process, while 3.5 rpm was used to extrude the CTA/NMP solution from the spinneret under N2 atmosphere. The extruded fibers were passed through the coagulant bath at 25 °C and collected using a take-up drum with its speed adjusted to free-fall. A range between 1 cm and 7 cm was used as the air gap distance. Table 1 lists the spinning parameters for the CTA HFMs and the NH2-MIL-125(Ti)/CTA HFMMMs spun in this study.

2.3. Solvent Exchange

The NMP solvent presence in the spun fibers was removed by solvent exchange using plain water, methanol, and n-hexane [48,49,50]. Firstly, water was used to soak the fibers for three days, with fresh water supplied between four hours and eight hours. Next, fibers were dipped into the methanol solvent for 30 min, 3 times, under mild stirring. This step was repeated by changing the methanol with n-hexane. Finally, the fibers were dried under ambient conditions for three days before use.

2.4. Post-Treatment

Post-treatment was conducted by coating the CTA HFMs and NH2-MIL-125(Ti)/CTA HFMMMs with PDMS. PDMS coating has been found to seal certain non-selective defects and also enhance the permeation of gas over the coated membranes. The PDMS solution was prepared using 3 wt% PDMS in n-hexane under continuous stirring [51]. The fibers were immersed in the PDMS solution for 10 min under mild stirring. Next, the fibers were air-dried at room temperature for at least 48 h. After coating and drying, the fibers proceeded to gas permeation testing and characterization study.

2.5. Characterization

The morphology of the NH2-MIL-125(Ti)/CTA HFMMMs was observed using a scanning electron microscope (SEM, Hitachi brand, model TM3030Plus). The fibers were split into smaller fibers after being submerged in liquid nitrogen. Then, the fibers were attached to a membrane holder and inserted inside the SEM machine. The SEM chamber was then vacuumed to avoid any discharge of electricity. Cross-sectional images of the membranes were then observed at 15 kV. Energy dispersive X-ray (EDX) was also used to examine the distribution of NH2-MIL-125(Ti) in the hollow fiber membranes through elemental mapping. Next, X-ray diffraction (XRD, Panalytical, Model: Xpert3 Powder) was used to determine the membrane crystallinity. The XRD was operated at temperatures of 25 °C with an electron beam energy set at 45 kV and 40 mA under vacuum conditions. The X-ray beams were diffracted within the XRD to produce the peaks at varying 2θ range. For the membrane samples, the diffraction data was collected at a scan step size of 0.026 for 2θ ranged from 5° to 40°.
Fourier Transform Infrared spectroscopy (FTIR, Perkin Elmer, Model: Frontier 01) was used to identify the chemical bonds present in the molecular structure of the membranes based on the ATR method. The FTIR spectrum of the fibers was achieved between 550 cm−1 and 4000 cm−1 under the transmittance mode at room temperature.

2.6. CO2 and CH4 Gas Permeation Testing

A module containing three fibers was prepared. Epoxy resin was used to fully seal one end of the module and partially seal the other end of the module as the permeate side. The epoxy was air-dried at room temperature for 48 h. Next, the module, after drying, was placed in a gas permeation housing cell and tightly sealed. The temperature and flowrate of the feed gas were set at 25 °C and 200 mL/min, respectively, and the gas was fed into the module’s shell side. A bubble flow meter and stopwatch were used to record the time taken for the bubble to reach a specific point. The time is used to measure the volumetric flowrate of permeate gas followed by the calculation of the CO2 permeance using Equation (1) as follows [52]:
P C O 2 L = Q A Δ P = Q n π D L m Δ P
where n, Lm (cm), Q (cm3/min), ΔP (cmHg), and D (cm) are the number of fibers, the effective length of fibers in each module, permeate flow rate, pressure drop, and outer diameter, respectively. 𝑃CO2 is the permeance of CO2 of the fiber measured in GPU (1 GPU = 1 × 10−6 cm3 (STP)/cm2.s.cmHg). The CO2/CH4 ideal selectivity was calculated using Equation (2) [52]:
α C O 2 / C H 4 = P C O 2 P C H 4
Figure 1 shows the gas permeation testing set up used in the current work [53].

3. Results and Discussion

3.1. Fabricated Membrane Characterization

Several characterizations were performed which included EDX, SEM, XRD, and FTIR to analyze the NH2-MIL-125(Ti) filler dispersion, morphology, crystallinity, and functional groups of the resultant membranes.

3.1.1. Energy Dispersive X-ray (EDX) and Scanning Electron Microscope (SEM)

Figure 2 shows the dispersion of NH2-MIL-125(Ti) fillers in the HFMMMs at varying air gaps using EDX mapping. The blue points shown in the EDX mapping represent the dispersed Ti elements on the surface of the HFMMMs. From Figure 2, it can be seen that the Ti elements were homogeneously dispersed with the absence of any agglomeration at all air gaps, possibly due to the use of a low NH2-MIL-125(Ti) loading percentage (1 wt%) in the HFMMMs.
Figure 3 shows the cross-sectional SEM images of the NH2-MIL-125(Ti)/CTA HFMMMs spun at air gap distances ranging from 1 cm to 7 cm. As shown in Figure 3, macrovoids are present in all membranes. The presence of the macrovoids could possibly be due to the non-solvent intrusion during die swell and also from the Marangoni effect [21,54], which could affect the gas permeation performance of the membranes.

3.1.2. X-ray Diffraction (XRD) of Resultant Membranes

XRD was utilized to examine the crystalline structure of the NH2-MIL-125(Ti)/CTA HFMMM. The neat CTA HFM and NH2-MIL-125(Ti)/CTA HFMMM XRD spectra are observed in Figure 4. From the analysis, broad amorphous peaks are found at 8° and 17°, which suggests the presence of the cellulose triacetate polymer structure [55]. However, with the incorporation of the filler into the CTA polymer, it can be observed that the peaks are slightly more prominent in the HFMMM. No other significant peak was observed for the HFMMM possibly due to the incorporation of a relatively low loading of the NH2-MIL-125(Ti) filler.

3.1.3. Fourier-Transformed Infrared (FTIR) Spectra of Resultant Membranes

FTIR was used to identify the interactions and chemical functionalities between CTA polymer and NH2-MIL-125(Ti) filler. The FTIR spectra of the CTA HFMs and NH2-MIL-125(Ti)/CTA HFMMMs for the band vibrations between 550 cm−1 and 4000 cm−1 are shown in Figure 5. The peaks found at 3530 cm−1, 2956 cm−1, and 1752 cm−1 for CTA HFM represent the O-H stretch bond, the C-H stretch bond, and the C=O stretch band, respectively [56]. The acetyl group was observed by the C-O stretch at 1220 cm−1, while the C-O-C stretch which represents the cellulose backbone was observed at 1040 cm−1 [55]. Similar CTA spectra were also reported elsewhere [57]. From the spectra analysis, both fibers showed ester characteristic adsorption bands based on the C=O stretching at 1752 cm−1 and the CH3 symmetrical deformation at 1371 cm−1 [58]. Moreover, with the addition of the NH2-MIL-125(Ti) filler in the HFMMMs, an NH2-group was identified in between the minor broad peaks of 3530 cm−1 and 3350 cm−1, despite the low loading percentage of 1 wt% [59,60,61].

3.2. CO2 and CH4 Gas Permeation Study

In this current study, CO2 and CH4 gas permeation testing was conducted for CTA HFMs and NH2-MIL-125(Ti)/CTA HFMMMs at ambient temperature and feed pressure of 5 bar gauge. Figure 6, Figure 7 and Figure 8 show the CO2 gas permeability, CH4 gas permeability, and CO2/CH4 gas pair selectivity of all fabricated fibers, respectively.
The fabricated neat CTA HFMs spun at 1 cm to 3 cm showed an increase in CO2 permeability followed by a gradual decrease in CO2 permeability for the HFM spun at an air gap of 7 cm. Meanwhile, CH4 permeability showed an increasing trend for the fibers spun at an air gap of 1 cm to 5 cm and then decreased for the fiber spun at 7 cm. Neat CTA HFMs spun at a 3 cm air gap demonstrated the highest CO2 permeability at 65.68 GPU while CTA HFMs spun at a 5 cm air gap exhibited the highest CH4 permeability of 90.69 GPU among CTA HFMs. However, neat CTA HFMs demonstrated low CO2/CH4 selectivity, possibly due to various surface defects. Therefore, PDMS coating which has been proven to reduce surface defects [51,62] was applied to the neat fibers to improve their gas permeation performance. Generally, PDMS-coated CTA HFMs showed a noticeable increment in CO2/CH4 selectivity with a significant drop in CO2 and CH4 permeability, especially for fibers spun at 3 and 5 cm air gaps, with a decrease in CO2 permeability up to 95% and 295%, respectively. PDMS coated CTA HFMs spun at a 7 cm air gap revealed the highest increase in CO2/CH4 gas pair selectivity, from 0.65 to 1.47, with an improvement of 126%. Despite that, PDMS coated CTA HFM spun at a 3-cm air gap showed a very marginal improvement of CO2/CH4 selectivity, besides demonstrating a 95% and 50% decrease in CO2 and CH4 permeability, respectively.
On the other hand, neat NH2-MIL-125(Ti)/CTA HFMMMs exhibited an improvement in gas permeation performance over the neat CTA HFMs due to the presence of an amine group, which resulted in the facilitated transport of CO2 over the membrane. The increment of CO2 permeability of up to 380% and CH4 permeability of up to 264% with a slight improvement in CO2/CH4 gas pair selectivity was found for the HFMMM. The increase in CO2 permeability may be attributed to the formation of defects and macrovoids found on the HFMMMs as seen in the SEM images in Figure 3. The CO2 permeability increased initially as the air gap increased after 1 cm and then maintained a similar gas permeance of about 128 GPU from an air gap of 3 cm to 7 cm. Nevertheless, the high CO2 and CH4 gas permeability obtained could be due to the presence of defects and macrovoids on the HFMMM as observed in Figure 3 [21,44,63]. After the PDMS coating was applied to the resultant HFMMMs, a decrease in CO2 permeability of 43% was observed for the HFMMM spun at an air gap of 1 cm, while the other HFMMMs spun at an air gap of 3 cm to 7 cm showed only a minor decrease in CO2 permeability. Whereas, for the CH4 permeability, a significant drop of 71% and 48% was observed for the fibers spun at an air gap of 1 cm and 5 cm, respectively. It can be observed that the HFMMM spun at an air gap of 3 cm showed lower performance compared to neat CTA HFMs, possibly due to the incorporation of the filler, which caused the stressing and widening of the macrovoids present on the membrane [64]. Subsequently, for the PDMS-coated HFMMM spun at an air gap of 1 cm, a noticeable tradeoff was observed, whereby the decrease in CO2 and CH4 gas permeability led to a slight increase in CO2/CH4 selectivity from 0.84 to 1.61. The improvements were 92% and 34% compared to the neat HFMMM and PDMS-coated HFM, respectively. An almost similar result trend was obtained for the PDMS-coated HFMMM spun at a 5 cm air gap. However, PDMS-coated HFMMMs spun at an air gap of 3 cm and 7 cm showed poorer results in terms of CO2/CH4 selectivity. This is likely due to the significant surface defects found on the fibers.
Moving on, a second layer of PDMS was applied to the NH2-MIL-125(Ti)/CTA HFMMM to further seal any possible non-selective defects. From the CO2/CH4 selectivity results obtained (as shown in Figure 8), the HFMMMs coated with double PDMS layers performed better than the other membranes spun at all air gaps. HFMMM spun at an air gap of 1 cm showed the highest performance with a CO2/CH4 selectivity of 6.87, a CO2 permeance of 26.46 GPU, and a CH4 permeability of 3.85 GPU. Among the tested HFMMMs coated with double PDMS coating layers, a fluctuating CO2/CH4 gas pair selectivity was obtained as the air gap increased, with the lowest CO2/CH4 selectivity of 1.68 obtained for the fiber spun at an air gap of 7 cm. The low performance of the fiber at the highest air gap (7 cm) could possibly be due to instability caused by the overstretching of the polymer chain leading to elongation and gravitational stress. This may further increase defects and macrovoids on the selective dense skin of the fiber, which was unable to be further improved by applying multiple PDMS coating layers [21,44,65].
In summary, HFMMMs coated with double PDMS layers showed a substantial boost in CO2/CH4 selectivity performance, especially for fibers spun at an air gap from 1 cm to 5 cm, but this led to a decrease in CO2 and CH4 permeability. A comparison between the CO2/CH4 gas permeability results of the current work with those results reported in the literature are presented in Table 2. Based on Table 2, the NH2-MIL-125/CTA HFMMMs fabricated at an air gap distance of 1 cm performed better than the NH2-MIL-53(Al)/CA HFMMM in terms of CO2 permeance but with a lower CO2/CH4 selectivity, while against the NH2-MIL-125(Ti)/PVDF HFMMM, it showed a greater CO2/CH4 selectivity and lower CO2 permeance. Therefore, by comparison, the NH2-MIL-125/CTA HFMMM prepared in this work show a reasonable gas separation performance with potential for improvement through optimization of the spinning parameters or filler loading.

4. Conclusions

In this study, NH2-MIL-125(Ti)/CTA HFMMMs were successfully spun at different air gaps ranging from 1 to 7 cm. EDX mapping analysis showed that filler dispersion in the HFMMM was homogeneous with no indication of agglomeration, possibly due to the use of a low loading percentage of filler. SEM cross-sectional images of the fabricated fibers showed the presence of macrovoids in all spun fibers. The amorphous broad peaks were shown in the XRD result for CTA HFMs but with the incorporation of the filler in the HFMMM, an amorphous phase was still observed mainly due to the low loading of the filler. FTIR spectra revealed a broad peak between 3530 cm−1 and 3350 cm−1 for HFMMM compared to the spectrum obtained for CTA due to the incorporation of the NH2-MIL-125(Ti) filler in CTA.
For the PDMS-coated CTA HFM, the best-performing fiber was found at a 7 cm air gap with a CO2 permeability of 23.42 GPU and a CO2/CH4 selectivity of 1.47, which achieved a 126% improvement over the uncoated CTA HFMs. On the other hand, the HFMMM spun at a 1 cm air gap and coated with a double layer of PDMS showed a CO2/CH4 selectivity of 6.87 and a CO2 permeance of 26.46 GPU. For future improvement, different loadings of fillers can be investigated to determine the optimum amount of filler required. Moreover, other spinning parameters such as the take-up speed and dope flowrate can be manipulated to find the optimum conditions for the enhancement of gas separation performance.

Author Contributions

Conceptualization, Y.-Y.F., M.A.B.; validation, Y.-Y.F.; formal analysis, N.S.; investigation, W.-J.L., N.S.; resources, M.A.B., Y.-Y.F.; data curation, N.S.; writing—original draft preparation, N.S.; writing—review and editing, W.-J.L., Y.-Y.F.; visualization, W.-J.L., N.S.; supervision, M.A.B., Y.-Y.F.; project administration, Y.-Y.F.; funding acquisition, Y.-Y.F. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Universiti Teknologi PETRONAS under the Joint Research Grant, cost center 015MDO-079 and the YUTP research grant, cost center 015LCO-099.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The financial and technical support provided by Universiti Teknologi PETRONAS under the Joint Research Grant (JRP, Cost Center: 015MD0-079), the Yayasan Universiti Teknologi PETRONAS (YUTP) Research Grant (Cost Center: 015LC0-099) and the CO2 Research Centre (Cost Center: 015NEC-001), Universiti Teknologi PETRONAS are duly acknowledged.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. International Agency Agency (IEA). Electricity Market Report—December 2020. Paris. 2020. Available online: https://www.iea.org/reports/electricity-market-report-december-2020 (accessed on 11 October 2022).
  2. Vega, F.; Cano, M.; Camino, S.; Fernández, L.M.G.; Portillo, E.; Navarrete, B. Solvents for Carbon Dioxide Capture. In Carbon Dioxide Chemistry, Capture and Oil Recovery; IntechOpen: London, UK, 2018. [Google Scholar] [CrossRef] [Green Version]
  3. Olivier, J.G.J.; Peters, J.A.H.W. Trends in Global CO2 and Total Greenhouse Gas Emissions; PBL Netherlands Environmental Assessment Agency: The Hague, The Netherlands, 2020; pp. 1–85. [Google Scholar]
  4. Abu Bakar, W.A.W.; Ali, R. Natural Gas. In Natural Gas; Primoz, P., Ed.; IntechOpen: Rijeka, 2010; p. Ch. 1. [Google Scholar]
  5. Sukor, N.R.; Shamsuddin, A.H.; Mahlia, T.M.I.; Mat Isa, M.F. Techno-Economic Analysis of CO2 Capture Technologies in Offshore Natural Gas Field: Implications to Carbon Capture and Storage in Malaysia. Processes 2020, 8, 350. [Google Scholar] [CrossRef] [Green Version]
  6. Darman, N.H.; Harun, A.R. Technical Challenges and Solutions on Natural Gas Development in Malaysia. In Proceedings of the The petroleum Policy and Management (PPM) Project 4th Workshop of the China—Sichuan Basin Case Study, Beijing, China, 30 May–3 June 2006. [Google Scholar]
  7. Hamad, F.; Qahtani, M.; Ameen, A.; Vaidya, M.; Duval, S.; Bahamdan, A.; Otaibi, F. Treatment of highly sour natural gas stream by hybrid membrane-amine process: Techno-economic study. Sep. Purif. Technol. 2020, 237, 116348. [Google Scholar] [CrossRef]
  8. Riboldi, L.; Bolland, O. Overview on Pressure Swing Adsorption (PSA) as CO2 Capture Technology: State-of-the-Art, Limits and Potentials. Energy Procedia 2017, 114, 2390–2400. [Google Scholar] [CrossRef]
  9. Shang, J.; Hanif, A.; Li, G.; Xiao, G.; Liu, J.Z.; Xiao, P.; Webley, P.A. Separation of CO2 and CH4 by Pressure Swing Adsorption Using a Molecular Trapdoor Chabazite Adsorbent for Natural Gas Purification. Ind. Eng. Chem. Res. 2020, 59, 7857–7865. [Google Scholar] [CrossRef]
  10. Grande, C.A. Advances in Pressure Swing Adsorption for Gas Separation. ISRN Chem. Eng. 2012, 2012, 982934. [Google Scholar] [CrossRef] [Green Version]
  11. Mondino, G.; Grande, C.A.; Blom, R.; Nord, L.O. Moving bed temperature swing adsorption for CO2 capture from a natural gas combined cycle power plant. Int. J. Greenh. Gas Control. 2019, 85, 58–70. [Google Scholar] [CrossRef]
  12. McKeen, L.W. Markets and Applications for Films, Containers, and Membranes. In Permeability Properties of Plastics and Elastomers; William Andrew Publishing: Oxford, UK, 2012; pp. 59–75. [Google Scholar] [CrossRef]
  13. Zhang, L.-Z. Heat and Mass Transfer in Hollow Fiber Membrane Bundles with Randomly Distributed Fibers. In Conjugate Heat and Mass Transfer in Heat Mass Exchanger Ducts; ResearchGate: Berlin, Germany, 2013; pp. 233–254. [Google Scholar]
  14. Warsinger, D.M.; Chakraborty, S.; Tow, E.W.; Plumlee, M.H.; Bellona, C.; Loutatidou, S.; Karimi, L.; Mikelonis, A.M.; Achilli, A.; Ghassemi, A.; et al. A review of polymeric membranes and processes for potable water reuse. Prog. Polym. Sci. 2016, 81, 209–237. [Google Scholar] [CrossRef]
  15. Wong, K.K.; Jawad, Z.A. A review and future prospect of polymer blend mixed matrix membrane for CO2 separation. J. Polym. Res. 2019, 26, 289. [Google Scholar] [CrossRef]
  16. Han, Y.; Ho, W.S.W. Recent advances in polymeric membranes for CO2 capture. Chin. J. Chem. Eng. 2018, 26, 2238–2254. [Google Scholar] [CrossRef]
  17. Robeson, L.M. The upper bound revisited. J. Membr. Sci. 2008, 320, 390–400. [Google Scholar] [CrossRef]
  18. Scholes, C.A.; Stevens, G.W.; Kentish, S.E. Membrane gas separation applications in natural gas processing. Fuel 2012, 96, 15–28. [Google Scholar] [CrossRef]
  19. Liu, C.; Wilson, S.T.; Kulprathipanja, S. Crosslinked Organic-Inorganic Hybrid Membranes and Their Use in Gas Separation. US 8,030,399 B2, 4 October 2011. [Google Scholar]
  20. Chen, G.-J.; Lee, D.-J. Synthesis of asymmetrical cellulose acetate/cellulose triacetate forward osmosis membrane: Optimization. J. Taiwan Inst. Chem. Eng. 2019, 96, 299–304. [Google Scholar] [CrossRef]
  21. Raza, A.; Askari, M.; Liang, C.Z.; Peng, N.; Farrukh, S.; Hussain, A.; Chung, T.-S. Advanced multiple-layer composite CTA/CDA hollow fiber membranes for CO2 separations. J. Membr. Sci. 2021, 625, 119124. [Google Scholar] [CrossRef]
  22. Puleo, A.C.; Paul, D.R.; Kelley, S.S. The effect of degree of acetylation on gas sorption and transport behavior in cellulose acetate. J. Membr. Sci. 1989, 47, 301–332. [Google Scholar] [CrossRef]
  23. Ma, D.-Y.; Li, Z.; Xiao, J.-X.; Deng, R.; Lin, P.-F.; Chen, R.-Q.; Liang, Y.-Q.; Guo, H.-F.; Liu, B.; Liu, J.-Q. Hydrostable and Nitryl/Methyl-Functionalized Metal–Organic Framework for Drug Delivery and Highly Selective CO2 Adsorption. Inorg. Chem. 2015, 54, 6719–6726. [Google Scholar] [CrossRef]
  24. Liu, J.; Liu, G.; Gu, C.; Liu, W.; Xu, J.; Li, B.; Wang, W. Rational synthesis of a novel 3,3,5-c polyhedral metal–organic framework with high thermal stability and hydrogen storage capability. J. Mater. Chem. A 2016, 4, 11630–11634. [Google Scholar] [CrossRef]
  25. Qin, N.; Pan, A.; Yuan, J.; Ke, F.; Wu, X.; Zhu, J.; Liu, J.; Zhu, J. One-Step Construction of a Hollow Au@Bimetal–Organic Framework Core–Shell Catalytic Nanoreactor for Selective Alcohol Oxidation Reaction. ACS Appl. Mater. Interfaces 2021, 13, 12463–12471. [Google Scholar] [CrossRef]
  26. Qin, L.; Liang, F.; Li, Y.; Wu, J.; Guan, S.; Wu, M.; Xie, S.; Luo, M.; Ma, D. A 2D Porous Zinc-Organic Framework Platform for Loading of 5-Fluorouracil. Inorganics 2022, 10, 202. [Google Scholar] [CrossRef]
  27. Qin, L.; Li, Y.; Liang, F.; Li, L.; Lan, Y.; Li, Z.; Lu, X.; Yang, M.; Ma, D. A microporous 2D cobalt-based MOF with pyridyl sites and open metal sites for selective adsorption of CO2. Microporous Mesoporous Mater. 2022, 341, 112098. [Google Scholar] [CrossRef]
  28. Feng, C.; Khulbe, K.C.; Matsuura, T.; Farnood, R.; Ismail, A.F. Recent Progress in Zeolite/Zeotype Membranes. J. Membr. Sci. Res. 2015, 1, 49–72. [Google Scholar]
  29. Vinoba, M.; Bhagiyalakshmi, M.; Alqaheem, Y.; Alomair, A.A.; Pérez, A.; Rana, M.S. Recent progress of fillers in mixed matrix membranes for CO2 separation: A review. Sep. Purif. Technol. 2017, 188, 431–450. [Google Scholar] [CrossRef]
  30. Zheng, M.; Chen, J.; Zhang, L.; Cheng, Y.; Lu, C.; Liu, Y.; Singh, A.; Trivedi, M.; Kumar, A.; Liu, J. Metal organic frameworks as efficient adsorbents for drugs from wastewater. Mater. Today Commun. 2022, 31, 103514. [Google Scholar] [CrossRef]
  31. Qian, Q.; Asinger, P.A.; Lee, M.J.; Han, G.; Mizrahi Rodriguez, K.; Lin, S.; Benedetti, F.M.; Wu, A.X.; Chi, W.S.; Smith, Z.P. MOF-Based Membranes for Gas Separations. Chem. Rev. 2020, 120, 8161–8266. [Google Scholar] [CrossRef] [PubMed]
  32. Makarov, I.S.; Golova, L.K.; Bondarenko, G.N.; Anokhina, T.S.; Dmitrieva, E.S.; Levin, I.S.; Makhatova, V.E.; Galimova, N.Z.; Shambilova, G.K. Structure, Morphology, and Permeability of Cellulose Films. Membranes 2022, 12, 297. [Google Scholar] [CrossRef] [PubMed]
  33. Vahabi, A.H.; Norouzi, F.; Sheibani, E.; Rahimi-Nasrabadi, M. Functionalized Zr-UiO-67 metal-organic frameworks: Structural landscape and application. Coord. Chem. Rev. 2021, 445, 214050. [Google Scholar] [CrossRef]
  34. Castro-Munoz, R.; Fila, V. Progress on Incorporating Zeolites in Matrimid((R))5218 Mixed Matrix Membranes towards Gas Separation. Membranes 2018, 8, 30. [Google Scholar] [CrossRef] [Green Version]
  35. Karousos, D.S.; Lei, L.; Lindbråthen, A.; Sapalidis, A.A.; Kouvelos, E.P.; He, X.; Favvas, E.P. Cellulose-based carbon hollow fiber membranes for high-pressure mixed gas separations of CO2/CH4 and CO2/N2. Sep. Purif. Technol. 2020, 253, 117473. [Google Scholar] [CrossRef]
  36. Davood Abadi Farahani, M.H.; Chung, T.-S. Solvent resistant hollow fiber membranes comprising P84 polyimide and amine-functionalized carbon nanotubes with potential applications in pharmaceutical, food, and petrochemical industries. Chem. Eng. J. 2018, 345, 174–185. [Google Scholar] [CrossRef]
  37. Sasikumar, B.; Bisht, S.; Arthanareeswaran, G.; Ismail, A.F.; Othman, M.H.D. Performance of polysulfone hollow fiber membranes encompassing ZIF-8, SiO2/ZIF-8, and amine-modified SiO2/ZIF-8 nanofillers for CO2/CH4 and CO2/N2 gas separation. Sep. Purif. Technol. 2021, 264, 118471. [Google Scholar] [CrossRef]
  38. Gong, X.; Wang, Y.; Kuang, T. ZIF-8-Based Membranes for Carbon Dioxide Capture and Separation. ACS Sustain. Chem. Eng. 2017, 5, 11204–11214. [Google Scholar] [CrossRef]
  39. Liu, B.; Li, D.; Yao, J.; Sun, H. Improved CO2 separation performance and interfacial affinity of mixed matrix membrane by incorporating UiO-66-PEI@[bmim][Tf2N] particles. Sep. Purif. Technol. 2020, 239, 116519. [Google Scholar] [CrossRef]
  40. Jiang, Y.; Liu, C.; Caro, J.; Huang, A. A new UiO-66-NH2 based mixed-matrix membranes with high CO2/CH4 separation performance. Microporous Mesoporous Mater. 2019, 274, 203–211. [Google Scholar] [CrossRef]
  41. Shah Buddin, M.M.H.; Ahmad, A.L. A review on metal-organic frameworks as filler in mixed matrix membrane: Recent strategies to surpass upper bound for CO2 separation. J. CO2 Util. 2021, 51, 101616. [Google Scholar] [CrossRef]
  42. Suhaimi, N.H.; Yeong, Y.F.; Jusoh, N.; Chew, T.L.; Bustam, M.A.; Suleman, S. Separation of CO2 from CH4 using mixed matrix membranes incorporated with amine functionalized MIL-125 (Ti) nanofiller. Chem. Eng. Res. Des. 2020, 159, 236–247. [Google Scholar] [CrossRef]
  43. Wang, M.; Wang, Z.; Zhao, S.; Wang, J.; Wang, S. Recent advances on mixed matrix membranes for CO2 separation. Chin. J. Chem. Eng. 2017, 25, 1581–1597. [Google Scholar] [CrossRef]
  44. Li, G.; Kujawski, W.; Válek, R.; Koter, S. A review—The development of hollow fibre membranes for gas separation processes. Int. J. Greenh. Gas Control. 2021, 104, 103195. [Google Scholar] [CrossRef]
  45. Mehmood, O.; Farrukh, S.; Hussain, A.; Younas, M.; Salahuddin, Z.; Pervaiz, E.; Ayoub, M. Investigation of cellulose acetate/gamma-cyclodextrin MOF based mixed matrix membranes for CO2/CH4 gas separation. Greenh. Gases Sci. Technol. 2021, 11, 313–330. [Google Scholar] [CrossRef]
  46. Sanaeepur, H.; Kargari, A.; Nasernejad, B.; Ebadi Amooghin, A.; Omidkhah, M. A novel Co2+ exchanged zeolite Y/cellulose acetate mixed matrix membrane for CO2/N2 separation. J. Taiwan Inst. Chem. Eng. 2016, 60, 403–413. [Google Scholar] [CrossRef]
  47. Chen, X.Y.; Kaliaguine, S.; Rodrigue, D. A Comparison between Several Commercial Polymer Hollow Fiber Membranes for Gas Separation. J. Membr. Sep. Technol. 2017, 6, 1–15. [Google Scholar] [CrossRef]
  48. Bernardo, P.; Tasselli, F.; Chiappetta, G.; Clarizia, G. Effect of the Post-Spinning Solvent Exchange on the Performance of Asymmetric, Polyimide Hollow Fibers Prepared by Using a Triple-Orifice Spinneret. Materials 2019, 12, 3632. [Google Scholar] [CrossRef] [Green Version]
  49. Isanejad, M.; Azizi, N.; Mohammadi, T. Pebax membrane for CO2/CH4 separation: Effects of various solvents on morphology and performance. J. Appl. Polym. Sci. 2017, 134, 44531. [Google Scholar] [CrossRef]
  50. Zhu, H.; Jie, X.; Wang, L.; Kang, G.; Liu, D.; Cao, Y. Effect of MIL-53 on phase inversion and gas separation performance of mixed matrix hollow fiber membranes. RSC Adv. 2016, 6, 69124–69134. [Google Scholar] [CrossRef]
  51. Hu, L.; Cheng, J.; Li, Y.; Liu, J.; Zhou, J.; Cen, K. Optimization of coating solution viscosity of hollow fiber-supported polydimethylsiloxane membrane for CO2/H2separation. J. Appl. Polym. Sci. 2018, 135, 45765. [Google Scholar] [CrossRef]
  52. Mubashir, M.; Yin fong, Y.; Leng, C.T.; Keong, L.K.; Jusoh, N. Study on the effect of process parameters on CO2/CH4 binary gas separation performance over NH2-MIL-53(Al)/cellulose acetate hollow fiber mixed matrix membrane. Polym. Test. 2020, 81, 106223. [Google Scholar] [CrossRef]
  53. Mubashir, M.; Yeong, Y.F.; Lau, K.K.; Chew, T.L. Effect of spinning conditions on the fabrication of cellulose acetate hollow fiber membrane for CO2 separation from N2 and CH4. Polym. Test. 2019, 73, 1–11. [Google Scholar] [CrossRef]
  54. Peng, N.; Chung, T.-S.; Wang, K.Y. Macrovoid evolution and critical factors to form macrovoid-free hollow fiber membranes. J. Membr. Sci. 2008, 318, 363–372. [Google Scholar] [CrossRef]
  55. Shaikh, H.M.; Anis, A.; Poulose, A.M.; Al-Zahrani, S.M.; Madhar, N.A.; Alhamidi, A.; Aldeligan, S.H.; Alsubaie, F.S. Synthesis and Characterization of Cellulose Triacetate Obtained from Date Palm (Phoenix dactylifera L.) Trunk Mesh-Derived Cellulose. Molecules 2022, 27, 1434. [Google Scholar] [CrossRef]
  56. Raza, A.; Japip, S.; Liang, C.Z.; Farrukh, S.; Hussain, A.; Chung, T.S. Novel Cellulose Triacetate (CTA)/Cellulose Diacetate (CDA) Blend Membranes Enhanced by Amine Functionalized ZIF-8 for CO2 Separation. Polymers 2021, 13, 2946. [Google Scholar] [CrossRef]
  57. Jawaid, M.; Li, F.; Sun, M.; Cheng, Q.; Yang, B.; Kenawy, E.-R. Preparation and Characterization of Graphene Oxide/Cellulose Triacetate Forward Osmosis Membranes. MATEC Web Conf. 2016, 67, 1015. [Google Scholar] [CrossRef]
  58. Cobo, F.N.; Faria-Tisher, P.C.S.; Duarte, J.L.; Carvalho, G.M. Preparation and characterization of microporous cellulose acetate films using breath figure method by spin coating technique. Cellulose 2017, 24, 4981–4995. [Google Scholar] [CrossRef]
  59. Suhaimi, N.H.; Yeong, Y.F.; Ch'ng, C.W.M.; Jusoh, N. Tailoring CO2/CH4 Separation Performance of Mixed Matrix Membranes by Using ZIF-8 Particles Functionalized with Different Amine Groups. Polymers 2019, 11, 2042. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  60. Zakariya, S.; Yeong, Y.F.; Jusoh, N.; Tan, L.S. Performance of Multilayer Composite Hollow Membrane in Separation of CO2 from CH4 in Mixed Gas Conditions. Polymers 2022, 14, 1480. [Google Scholar] [CrossRef] [PubMed]
  61. Zhu, X.; Yu, Z.; Wang, J.; Wang, P.; Li, X.; Long, R.; Wang, Q. Chemically stable NH2-MIL-125(Ti)/Sep/PDA composite membranes with high-efficiency for oil/water emulsions separation. Colloids Surf. A Physicochem. Eng. Asp. 2022, 646, 128899. [Google Scholar] [CrossRef]
  62. Pal, N.; Agarwal, M. Advances in materials process and separation mechanism of the membrane towards hydrogen separation. Int. J. Hydrog. Energy 2021, 46, 27062–27087. [Google Scholar] [CrossRef]
  63. Li, G.; Kujawski, W.; Knozowska, K.; Kujawa, J. Thin Film Mixed Matrix Hollow Fiber Membrane Fabricated by Incorporation of Amine Functionalized Metal-Organic Framework for CO2/N2 Separation. Materials 2021, 14, 3366. [Google Scholar] [CrossRef]
  64. Taurozzi, J.S.; Arul, H.; Bosak, V.Z.; Burban, A.F.; Voice, T.C.; Bruening, M.L.; Tarabara, V.V. Effect of filler incorporation route on the properties of polysulfone–silver nanocomposite membranes of different porosities. J. Membr. Sci. 2008, 325, 58–68. [Google Scholar] [CrossRef]
  65. Ahmad, A.L.; Otitoju, T.A.; Ooi, B.S. Hollow fiber (HF) membrane fabrication: A review on the effects of solution spinning conditions on morphology and performance. J. Ind. Eng. Chem. 2019, 70, 35–50. [Google Scholar] [CrossRef]
  66. Mubashir, M.; Yeong, Y.F.; Chew, T.L.; Lau, K.K. Optimization of spinning parameters on the fabrication of NH2-MIL-53(Al)/cellulose acetate (CA) hollow fiber mixed matrix membrane for CO2 separation. Sep. Purif. Technol. 2019, 215, 32–43. [Google Scholar] [CrossRef]
  67. Ding, S.H.; Oh, P.C.; Mukhtar, H.; Jamil, A. Fabrication of NH2-MIL-125 (Ti)/Polyvinylidene fluoride hollow fiber mixed matrix membranes for removal of environmentally hazardous CO2 gas. J. Nat. Gas Sci. Eng. 2022, 107, 104794. [Google Scholar] [CrossRef]
Separations 10 00041 g001 550
Figure 1. Equipment design for the in-house gas permeation test system used for the experiment [53].
Figure 1. Equipment design for the in-house gas permeation test system used for the experiment [53].
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Figure 2. NH2-MIL-125(Ti)/CTA HFMMMs spun at various air gap distances of (a) 1 cm, (b) 3 cm, (c) 5 cm, and (d) 7 cm.
Figure 2. NH2-MIL-125(Ti)/CTA HFMMMs spun at various air gap distances of (a) 1 cm, (b) 3 cm, (c) 5 cm, and (d) 7 cm.
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Figure 3. SEM cross-sectional images of NH2-MIL-125(Ti)/CTA HFMMM spun at different air gap distances of (a) 1 cm, (b) 3 cm, (c) 5 cm, and (d) 7 cm.
Figure 3. SEM cross-sectional images of NH2-MIL-125(Ti)/CTA HFMMM spun at different air gap distances of (a) 1 cm, (b) 3 cm, (c) 5 cm, and (d) 7 cm.
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Figure 4. XRD pattern of CTA HFM and NH2-MIL-125(Ti)/CTA HFMMM.
Figure 4. XRD pattern of CTA HFM and NH2-MIL-125(Ti)/CTA HFMMM.
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Figure 5. FTIR Spectra of CTA HFMs and NH2-MIL-125(Ti)/CTA HFMMMs.
Figure 5. FTIR Spectra of CTA HFMs and NH2-MIL-125(Ti)/CTA HFMMMs.
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Figure 6. CO2 gas permeance for the fabricated fibers at various air gap distances.
Figure 6. CO2 gas permeance for the fabricated fibers at various air gap distances.
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Figure 7. CH4 gas permeance for the fabricated fibers at various air gap distances.
Figure 7. CH4 gas permeance for the fabricated fibers at various air gap distances.
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Figure 8. CO2/CH4 gas pair ideal selectivity for the fabricated fibers at various air gap distances.
Figure 8. CO2/CH4 gas pair ideal selectivity for the fabricated fibers at various air gap distances.
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Table
Table 1. Parameters for the spinning of CTA HFM and NH2-MIL-125(Ti)/CTA HFMMM.
Table 1. Parameters for the spinning of CTA HFM and NH2-MIL-125(Ti)/CTA HFMMM.
ParametersConditions
Dope SolutionsCTA/NMP
NH2-MIL-125(Ti)/CTA/NMP
CTA (wt%)13
Bore Fluid (NMP/Water, wt%)90/10
Spinneret Dimensions (OD/ID, mm)0.8/0.4
Dope Flow Rate (rpm)3.5
Bore Flow Rate (mL/min)0.33
Coagulant Temperature (°C)25
Air Gap Distance (cm)1, 3, 5 and 7
Table
Table 2. Comparison of CO2/CH4 gas permeability results of CTA HFM and NH2-MIL-125(Ti)/CTA HFMMM in the current work with those results reported in the literature.
Table 2. Comparison of CO2/CH4 gas permeability results of CTA HFM and NH2-MIL-125(Ti)/CTA HFMMM in the current work with those results reported in the literature.
MembraneFiller
Loading (%)		ConfigurationAir Gap
Distance (cm)		Post
Treatment		CO2
Permeance		CO2/CH4
Ideal Selectivity		Ref
CTA-Hollow
fiber		1PDMS coating22.49 GPU1.20This work
NH2-MIL-125(Ti)/CTA1Hollow
fiber		1PDMS coating26.46 GPU6.87This work
NH2-MIL-53(Al)/CA15Hollow
fiber		5-14.30 GPU9.10[66]
NH2-MIL-125(Ti)/PVDF1Hollow
fiber		15-350 GPU4.00[67]
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Sunder, N.; Fong, Y.-Y.; Bustam, M.A.; Lau, W.-J. Study on the Performance of Cellulose Triacetate Hollow Fiber Mixed Matrix Membrane Incorporated with Amine-Functionalized NH2-MIL-125(Ti) for CO2 and CH4 Separation. Separations 2023, 10, 41. https://doi.org/10.3390/separations10010041

AMA Style

Sunder N, Fong Y-Y, Bustam MA, Lau W-J. Study on the Performance of Cellulose Triacetate Hollow Fiber Mixed Matrix Membrane Incorporated with Amine-Functionalized NH2-MIL-125(Ti) for CO2 and CH4 Separation. Separations. 2023; 10(1):41. https://doi.org/10.3390/separations10010041

Chicago/Turabian Style

Sunder, Naveen, Yeong-Yin Fong, Mohamad Azmi Bustam, and Woei-Jye Lau. 2023. "Study on the Performance of Cellulose Triacetate Hollow Fiber Mixed Matrix Membrane Incorporated with Amine-Functionalized NH2-MIL-125(Ti) for CO2 and CH4 Separation" Separations 10, no. 1: 41. https://doi.org/10.3390/separations10010041

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