Mixed Matrix Hollow Fiber Membranes Research Articles

Membranes fouling propensity of PSF/GO hollow fiber mixed matrix membranes for water treatment ultrafiltration application.

The study investigated the fouling propensity of polysulfone (PSF) hollow fiber (HF) mixed matrix membranes modified with 1.0 wt.% graphene oxide (GO). Using scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle (WCA), and mechanical assessments, the structural characteristics of both untreated and GO-modified PSF HF membranes were examined. Filtration experiments included pure water and model contaminants such as bovine serum albumin (BSA), humic acid (HA), E. coli, and oil-in-water emulsion. The GO-modified membranes demonstrated a significant enhancement in antifouling performance, recovering over 90% of their initial pure water flux with HA and oil, indicating high resistance to irreversible fouling. Additionally, the GO-modified membranes showed superior oil separation efficiency. However, fouling parameters for BSA were similar for both membrane types, suggesting that GO does not significantly affect membrane-BSA interactions. Both types of membranes displayed high retention capabilities for E. coli, with no noticeable improvement due to GO addition. This study highlights the potential of GO-modified PSF HF membranes in enhancing antifouling performance and oil separation efficiency.

Mixed matrix membranes with incorporated glycosaminoglycans have good blood biocompatibility combined to high toxin removal

Most patients in need of renal replacement therapy use peritoneal or hemodialysis (HD) therapy. Major drawbacks of HD are the incomplete removal of uremic solutes (especially middle-sized uremic solutes and protein-bound uremic solutes, PBUTs) as well as the non-continuous therapy (3 times per week for 4 h), causing large fluctuations in water balance and uremic waste, potassium, and phosphate. For achieving better patient outcomes, more continuous therapies are required including the application of home HD or portable HD. The latter require membranes with excellent long-term biocompatibility. Heparin-modified dialysis membranes can offer improved biocompatibility, but systemic anticoagulation is still needed, whereas potential heparin-induced thrombocytopenia (HIT) may occur.Glycosaminoglycans (GAGs) contribute to the kidney glomerular filtration barrier and provide natural anti-fouling properties. Here, we hypothesized that the incorporation of GAGs within polymeric membranes, either via membrane coating, post membrane fabrication, or via blending GAGs into the membrane forming polymer matrix, would provide membranes with improved hemocompatibility. We implemented these strategies to mixed matrix membranes (MMMs) which combine diffusion and adsorption for removing a broad range of uremic solutes. Firstly, we fabricated flat sheet MMMs with various GAG sources, including heparan sulphate from bovine kidney (HSBK), heparinase III-digested HSBK, HS isolated from cultured glomerular endothelial glycocalyx, GAGs from porcine intestinal mucosa (danaparoid, DA), or heparin. The flat sheet MMMs with DA blended within the membrane selective layer have excellent blood compatibility, based on a panel of anti-coagulation and immune activation assays, combined to high water transport and very low albumin leakage. Besides, these MMMs had low clot formation, did not activate immune cells or the complement system and had low platelet adhesion. Based on these findings, we also developed first hollow fiber MMMs with DA blended in the selective layer, which also had high water transport, no leakage of protein, and achieved very good removal of various uremic solutes, comparable to commercial HD membranes.

Fine-tuning zeolite pore structures with carbon coating for enhanced gas separation in polyimide-based mixed matrix membrane

Impregnated zeolite-carbon (IZC), also known as pore-modified zeolite, was used as a potential filler in a P84 co-polyimide-based hollow fiber mixed matrix membrane (HF MMM) to enhance gas separation. The presence of carbon structure on the zeolite framework pore was to avoid the trapped moisture that could lead to permeability reduction. This work seeks to investigate the impact of IZC addition (0.5, 1.0, and 1.5 wt%) to the P84 membrane and examine its permeability and separation performance. Adding IZC filler to the P84 membrane generates the enhancement of gas selectivity and permeability. The optimal enhancement was observed at 1 wt% of IZC loading, in which selectivity of CO2/CH4, CO2/N2, O2/N2, H2/N2, and H2/CH4 was enhanced by 50.506, 51.042, 5.693, 16.712, and 16.338%, respectively. On the other hand, H2, CO2, and O2 permeability at the loading were improved from 11.182 to 26.761, from 4.683 to 14.501, and from 1.637 to 3.546 Barrer, respectively. The improvement of gas selectivity was contributed by the presence of carbon in the zeolite framework, providing a molecular sieving effect while tuning carbon properties with pore regularity by templating in the zeolite framework enhances the gas permeability.

Polymeric hollow fiber (HF) mixed matrix membranes (MMMs): Mutual effect of graphene oxide (GO) and polyvinylpyrrolidone (PVP) on nano-structuration

Hollow fiber (HF) membranes were fabricated using polysulfone (PSF) and 1.0 wt% graphene oxide (GO) synthesized through Hummer's method. The dry-wet spinning process was employed for their preparation. The structure and properties of both unmodified PSF HF membranes and those modified with GO were characterized. This encompassed analyses using scanning electron microscopy, attenuated total reflection Fourier Transform Infrared spectroscopy, thermo-gravimetric analysis, water contact angle (WCA) measurements, as well as evaluations of water permeability and mechanical attributes. The outcomes highlighted favorable mechanical and thermal characteristics. Moreover, the GO-modified PSF HF membranes exhibited larger surface pore sizes, along with an approximate 10% reduction in WCA and a fourfold increase in water permeability compared to the raw PSF HF membranes. Additionally, the influence of varying wt% of the pore-forming agent Polyvinylpyrrolidone (PVP) on the GO-modified PSF HF membranes was investigated. While no evidence suggests that GO can replace PVP, it is plausible to infer that this two-dimensional material complements the pore-forming agent's role by stabilizing the polymer-lean phase. This contributes to the creation of larger pores via phase separation mechanisms.

Electrospinning and spinning techniques combined for novel mixed matrix hollow fiber membranes: Structural analysis

This study experimentally and theoretically explores the feasibility of combining electrospinning and spinning methods in delivering high performance hollow fiber membrane structure especially for biogas separation. In this preliminary study, the zeolitic imidazolate framework-8 (ZIF-8) crystals were successfully synthesized, and the electrospun fiber of polysulfones (PSF)/ZIF-8 was successfully achieved via the electrospinning process. Interestingly, the images from scanning electron microscopy (SEM) showed a consistent arrangement of ZIF-8 electrospun fibers at the lumen side of the PSF/ZIF-8 hollow fiber membrane. This phenomenon was believed to be due to the bore fluid type, which consisted of N-methyl-2-pyrrolidone (NMP) and water (H2O), which affected the backing layer of hollow fiber. Moreover, this study might provide insight into the effect of bore fluid on the position of electrospun ZIF-8 fibers, and further study can be conducted to confirm the feasibility of these membranes being used in the applications such as for gas separation processes.

Influence of NH2-MOF addition into PVDF and estimation of CO2 gas transport through membrane

Polyvinylidene fluoride (PVDF) had been vastly utilised for CO2/CH4 gas separation application. Nevertheless, pure polymeric membranes always suffer from a trade-off between permeability and selectivity as proven by Robeson in upper bound curves developed in gas separation applications. Thus, alternative modification like incorporating filler into polymer matrix to develop mixed matrix membranes (MMMs) is required. Besides, estimation of CO2 permeance of MMMs via unsuitable theoretical models would result in mismatch between experimental and predicted CO2 permeance data, subsequently causing troubles in membrane separation system designation. In the current work, PVDF hollow fiber mixed matrix membranes (HFMMMs) had been developed using NH2-MIL-125 (Ti) loadings of 1, 1.5, 2.5, and 3 wt%. The synthesized NH2-MIL-125 (Ti) and spun NH2-MIL-125 (Ti)/PVDF HFMMMs were characterized using Fourier transform infrared (FTIR). Furthermore, the Maxwell, Pal, modified Pal, Lewis–Nielson, Bruggeman and Bottcher model, were utilised to estimate the CO2 permeance of developed membranes. The additional FTIR peaks appeared at around 3440, 3358, 1478, 1430 cm−1 for developed HFMMMs when compared with pure PVDF indicate the presence of NH2-MIL-125 (Ti) in the HFMMMs. CO2 permeance estimation of 1.5 wt% PVDF HFMMM using all selected models yields around 1 absolute average relative error percent (AARE%). The remaining membranes displayed a high deviation, with an AARE% exceeding ± 5. AARE% obtained in the current work suggested that all the selected models can fit 1.5 wt% PVDF HFMMM.

Fundamental understanding of irradiation intensity and other process parameters on photocatalytic degradation of phenol in hollow fiber mixed matrix membrane

Lack of comprehensive general theoretical model on photocatalytic mixed-matrix-membrane (PMMM) makes its practical application infeasible. The dynamic process involves bulk and porous fluid-flow; bulk convection–diffusion, interfacial adsorptive-reactive mass transport. All-inclusive first-principle based two-dimensional transient model with the continuity, momentum transport and convective-diffusive-adsorption-reaction equations are solved numerically. Experimental validation was taken up for phenol removal from synthetic solution using PMMM hollow fibres with titanium-di-oxide nanoparticle. The validated model were used to predict the performance at various light intensity (I) and feed concentrations (c0) in long-term successfully for three different cases of PMMMs. For the chosen case of PMMM, minimum I and maximum transmembrane pressure (TMP) with variable c0 for safe permeate were determined. The ‘safe operating conditions’ is the favourable operating conditions that generates permeate stream featuring a contaminant concentration under the safe discharge limit for a substantial period of time. For futuristic PMMM, a thorough parameter study was undertaken. The optimum TMP for minimum energy cost for scale-up were calculated interrelating with cross flow rates. Volume run-down was determined at safe operating conditions. This comprehensive theoretical framework can be implemented as groundwork to design present or futuristic hollow fiber PMMMs.

ZIF-8-based dual layer hollow fiber mixed matrix membrane for natural gas purification

To prevent pipe damage and lower operating costs, natural gas must be cleaned of pollutants like carbon dioxide (CO2) and hydrogen sulphide (H2S). High selectivity of the functional material in the mixed matrix membranes (MMMs) allows for a more efficient gas separation compared to traditional polymeric membranes. However, poor dispersion and compatibility between the functional material and the polymer matrix become one of the major problems of MMMs. The use of zeolite imidazole (ZIF-8) in MMMs has been explored for its ability to separate CO2/CH4 due to its versatile gas molecule diameter range and effective CO2 adsorption. In this study, the effects of ZIF-8 at various loadings were examined on the physical and chemical properties of dual layer hollow fiber MMMs and gas separation efficiency. Following the successful production of 86.25 nm ZIF-8 nanoparticles, ZIF-8-based DLHF MMMs were created. The results showed that 0.5 wt% ZIF-8 loading provided the best results, with excellent interaction between the polymer PSf and the inorganic filler ZIF-8, strong heat resistance, and chemical stability. Increased CO2 permeability and CO2/CH4 ideal selectivity by 72.5 % and 1196.2 % respectively, compared to the unmodified membrane. It was inferred through this study that minimal loading of 0.5 wt% ZIF-8 in the DLHF MMMs improved their ability to separate gases, making them a good option for capturing CO2.

Synergistic Effect of 2D ZIF Loading and Ionic Liquid Modification on Improving Gas Separation Performance of PES-Based Mixed Matrix Hollow Fiber Membrane

Synergistic Effect of 2D ZIF Loading and Ionic Liquid Modification on Improving Gas Separation Performance of PES-Based Mixed Matrix Hollow Fiber Membrane

Highly concentrated multivariate ZIF-8 mixed-matrix hollow fiber membranes for CO2 separation: Scalable fabrication and process analysis

Here, we report on the fabrication of mixed matrix hollow fiber membranes (MMHFMs) for CO2 separation using highly-concentrated 6FDA-DAM/triple-ligand, amine-modulated zeolitic imidazolate framework-8 (TAZIF-8) (60/40 w/w) via a dip coating process. The application of a γ-alumina interlayer serves a dual purpose of reducing the infiltration of the 6FDA-/TAZIF-8 coating solution into the porous α-alumina support, while also providing a smooth surface for the support. Importantly, the co-solvent comprising N-methyl-2-pyrrolidone and dichloromethane further inhibits the formation of defects by maintaining an appropriate balance of volatility and polarity. This balanced combination is crucial in promoting phase separation and facilitating the dispersion of nanofillers within the polymer matrix, enabling the formation of a thin defect-free selective layer. The subsequent 40 wt% TAZIF-8 MMHFM attains superior CO2 separation performance to most existing MMHFMs (CO2 permeance of 648 GPU and CO2/N2 and CO2/CH4 selectivity of 39.0 and 34.2, respectively). Furthermore, it maintains excellent CO2 separation performance over 120 d owing to good interfacial interaction between 6FDA-DAM and TAZIF-8s. Last, but not least, our process analysis reveals that the introduction of the TAZIF-8 MMHFM into the first stage of a dual-stage membrane process can improve the total energy demand for post-combustion CO2 capture due to its excellent CO2/N2 selectivity. Our current study provides significant progress toward the industrial application of post-combustion CO2 capture.

Investigating the effect of zirconium‐based and titanium‐based metal–organic frameworks nanoparticles on the performance of polysulfone hollow fiber mixed matrix membrane for dialysis application

AbstractThis study aims to investigate polysulfone (PSF) mixed matrix membranes (MMMs) properties containing zirconium‐based and titanium‐based metal–organic frameworks (MOFs). for hemodialysis application. The nanoparticles were synthesized, and the membranes were produced by the phase inversion method. Membrane characterization conducted by attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR), field emission Scanning electron microscope (FE‐SEM), energy‐dispersive x‐ray analysis (EDX), transmission electron microscopy (TEM), x‐ray diffraction (XRD), and atomic force microscopy (AFM) confirmed the presence of MOF nanoparticles. Also, the evaluation of the specific surface area of nanoparticles was done by BET. The water contact angle reduced from 64.4° to 51.2°, indicating the hydrophilicity improvement, enhancing the pure water flux from 46.8 L/m2h for the pristine membrane to 76.7 L/m2h for the pristine membrane M4. The total fouling resistance decreased from 30% to 21%, and the bovine serum albumin (BSA) adsorption of modified membranes was lower than that of the pristine membrane. Urea and creatinine were cleared significantly for modified ones, up to 82.6% and 72.1%, respectively, and all membranes showed BSA retention of more than 93%. A comparison between MMMs that contained UIO‐66‐NH2 and MIL‐125‐NH2 showed that the former had a better effect on the performance. M4 had better results, indicating high water flux, the lowest fouling resistance, high porosity, lower BSA adsorption, proper clearance for urea and creatinine, and 94.2% BSA retention.

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

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.

Preliminary study on ZIF-8 containing hollow fiber mixed matrix membranes (HFMMMs) for CO2 and CH4 gas permeation

The advantages in terms of smaller footprint, higher energy efficiency, larger surface-to-volume ratio and higher flux have opened various opportunities for hollow fiber membranes in separation processes especially in carbon dioxide (CO2) capture. Although the development of polymeric hollow fiber membrane has emerged as an important material in membrane technology, currently existing polymeric materials suffer from a limiting trade-off between selectivity and permeability. Recently, it has been reported in the literature that the addition of metal–organic frameworks into polymer matrixes have radically improved the separation performance of CO2 from methane (CH4), as well as enhanced the thermal stability and structural properties of the membrane. In this preliminary study, ZIF-8/cellulose triacetate hollow fiber mixed matrix membranes are fabricated by varying the air gap distances and subsequently, the morphology of the resultant membranes was analysed using a scanning electron microscope while the dispersion of ZIF-8 fillers in the polymer matrix was observed using an energy dispersive X-ray. The results showed that the ZIF-8 fillers were homogeneously distributed into the cellulose triacetate polymer. Then, the performance of the resultant membranes before and after post-treatment with polydimethylsiloxane in CO2 and CH4 gases permeation were evaluated. Due to the presence of multiple defects, the overall performance of the fabricated membranes was low with no significant improvements after post-treatment. Hence, further optimization study on the fabrication process is still required to improve the performance of the ZIF-8/cellulose triacetate hollow fiber mixed matrix membrane in CO2 and CH4 gas permeation.

Aminosilane-Functionalized Zeolite Y in Pebax Mixed Matrix Hollow Fiber Membranes for CO2/CH4 Separation

Due to their interfacial defects between inorganic fillers and polymer matrices, research into mixed matrix membranes (MMMs) is challenging. In the application of CO2 separation, these defects can potentially jeopardize the performance of membranes. In this study, aminosilane functionalization is employed to improve the nano-sized zeolite Y (ZeY) particle dispersion and adhesion in polyether block amide (Pebax). The performance of CO2/CH4 separation of Pebax mixed matrix composite hollow fiber membranes, incorporated with ZeY and aminosilane-modified zeolite Y (Mo-ZeY), is investigated. The addition of the zeolite filler at a small loading at 5 wt.% has a positive impact on both gas permeability and separation factor. Due to the CO2-facilitated transport effect, the performance of MMMs is further improved by the amino-functional groups modified on the ZeY. When 5 wt.% of Mo-ZeY is incorporated, the gas permeability and CO2/CH4 separation factor of the Pebax membrane are enhanced by over 100% and 35%, respectively.

Potential effects of nano‐fumed silica particles (NFS)/PVDF mixed matrix hollow fiber membrane on the performance of direct contact membrane distillation

AbstractHydrophobic nano‐fumed silica (NFS) was incorporated in polyvinylidene fluoride (PVDF) hollow fiber (HF) membrane for improving direct contact membrane distillation (DCMD) performance. The NFS/PVDF mixed matrix hollow fiber membrane was fabricated by the phase inversion process. The potential effects of increasing the percentage of NFS additive (0–6 wt.%) in the dope solution on the hollow fiber membrane characteristics such as viscosity, membrane morphology, porosity, hydrophobicity, Fourier transformed infrared spectroscopy, and permeability were investigated. The performance outcomes showed that the dope solution incorporated with 1.5 wt.% NFS exhibited the most promising HF membrane for membrane distillation (MD). The optimal HF membrane demonstrated the highest flux through shorter and narrower finger‐like structure formation and targeted high porosity. The addition of NFS particle content in the dope solutions enhanced the hydrophobicity of the fabricated membranes while slightly decreasing the porosity due to increasing the viscosity of the dope solution. With a steady flux of 9.25 kg/m2 h compared with the neat membrane at 70°C/20°C of feed/permeate temperatures, 8 h operation, and above 99.9% salt rejection, this PVDF/NFS mixed matrix hollow fiber membrane could be of excellent potential and sustainability in desalination process through DCMD.

PPSU dual layer hollow fiber mixed matrix membranes with functionalized MWCNT for enhanced antifouling, salt and dye rejection in water treatment

AbstractLoose nanofiltration dual layer hollow fiber membranes (DLHFM) were prepared from polyphenylsulfone (PPSU) with a thin contact mixed matrix membrane (MMM) outer layer containing functionalized multiwalled carbon nanotubes (MWCNT). Two types of MWCNT were used; oxidized MWCNT (OMWCNT) and polyethyleneimine (PEI) functionalized MWCNT (PEI‐MWCNT). Z potential measurements indicate that OMWCNT and PEI‐MWCNT were negatively charged, being OMWCNT most negative. Na2SO4, MgSO4, and methylene blue (MB) rejection was enhanced due to OMWCNT and PEI‐MWCNT incorporation in DLHFM outer layer. Enhanced hydrophilicity and negatively charge mixed matrix DLHFM layer was the key factor for a better mixed matrix DLHFM performance. The best salt and MB rejection was found in those membranes prepared with (OMWCNT) followed by (PEI‐MWCNT) compared with neat PPSU membranes. An increase of 113% and 100% in Na2SO4 and MB rejection respectively was attained in DLHFM with 0.04 wt%, OMWCNT (relative to dope's weight) in comparison with the neat PPSU membrane. Antifouling test for bovine serum albumin (BSA) and MB showed better performance also for the mixed matrix DLHFM containing OMWCNT's. In antifouling tests, a 4.4% and 25% flux recovery increase for MB and BSA respectively was obtained in DLHFM with 0.04 wt% OMWCNT compared with the neat PPSU DLHFM.

Fabrication of NH2-MIL-125 (Ti)/Polyvinylidene fluoride hollow fiber mixed matrix membranes for removal of environmentally hazardous CO2 gas

Improper pairing of filler and polymer together with inappropriate filler loadings into polymer matrix may lead to structural defects such as large aggregations and interface void formations. Subsequently, the structural defects may sacrifice the selectivity of CO2 over CH4, which was unfavorable. In the current work, NH2-MIL-125 (Ti) (MIL = Material Institute Lavoisier), which possesses NH2-groups and theoretically capable of forming strong hydrogen bonding with F-groups of polyvinylidene fluoride (PVDF), was selected to spin hollow fiber mixed matrix membranes (HFMMMs). Besides, NH2-MIL-125 (Ti) can interact better with CO2 over CH4 via quadrupole moment, and NH2-groups also aid in CO2 selectivity due to its high CO2 adsorption capability. The HFMMMs were spun using a dry-wet spinning technique of filler loadings percentage ranging from 1 to 3 wt percent (wt%). The effect of filler and loadings percentage over HFMMMs properties, including contact angle, mechanical strength, thermal stability and cross-sectional morphology was investigated. The compatibility at interface of filler and polymer was observed to be good, and dispersion was observed to be acceptable up to 2 wt% filler loadings. However, apparent aggregation was observed beyond this point. The wt% of Ti, O, and N elements were found to increase from 0.72 to 2.05, 3.27 to 4.53, and 0.52 to 1.55, respectively, with increasing filler loading into HFMMMs. Subsequently, PVDF-2 membrane displayed the highest CO2/CH4 ideal selectivity with contact angle of 83.44 ± 1.45, ultimate tensile strength (UTS) of 1.33, 29.12 Young's Modulus, and 72.2% elongation at break. Therefore, optimizing loading percentage and selecting appropriate filler are considered practical methods to ensure good morphology and better hazardous CO2 removal.

Status and future trends of hollow fiber biogas separation membrane fabrication and modification techniques.

With the increasing global demand for energy, renewable and sustainable biogas has attracted considerable attention. However, the presence of various gases such as methane, carbon dioxide (CO2), nitrogen, and hydrogen sulfide in biogas, and the potential emission of acid gases, which may adversely influence the environment, limits the efficient application of biogas in many fields. Consequently, researchers have focused on the upgrade and purification of biogas to eliminate impurities and obtain high-quality and high-purity biomethane with an increased combustion efficiency. In this context, the removal of CO2 gas, which is the most abundant contaminant in biogas, is of significance. Compared to conventional biogas purification processes such as water scrubbing, chemical absorption, pressure swing adsorption, and cryogenic separation, advanced membrane separation technologies are simpler to implement, easier to scale, and incur lower costs. Notably, hollow fiber membranes enhance the gas separation efficiency and decrease costs because their large specific surface area provides a greater range of gas transport. Several reviews have described biogas upgrading technologies and gas separation membranes composed of different materials. In this review, five commonly used commercial biogas upgrading technologies, as well as biological microalgae-based techniques are compared, the advantages and limitations of polymeric and mixed matrix hollow fiber membranes are highlighted, and methods to fabricate and modify hollow fiber membranes are described. This will provide more ideas and methods for future low-cost, large-scale industrial biogas upgrading using membrane technology.

ZIF-8/styrene-IL polymerization hollow fiber membrane for improved CO2/N2 separation

Compared to supported ionic liquid membranes, poly(ionic liquid) membranes are synthesized by the polymerization of ionic liquid monomers to develop polymeric backbone to improve its membrane stability for gas separation process. However, the resulting dense membrane structure induced the lower gas permeance of the poly(ionic liquid) membranes. To overcome this limitation, in this study, ZIF-8, possessing the property of molecular sieves, was added to poly(styrene-ionic liquid) hollow fiber membranes (p(SIL) HFMs), providing a transport pathway. SIL monomers with different lengths of alkyl chain were polymerized and integrated with ZIF-8 fillers to synthesize ZIF-8/poly(ionic liquid) mixed matrix hollow fiber membranes (ZIF-8/p(SIL) MMHFMs). When the chain length of SIL monomers was increased, the CO2 permeance of p(SIL) HFMs increased from 3.6 to 4.6 GPU, while CO2/N2 selectivity decreased from 29 to 23. Additionally, the CO2 permeance of ZIF-8/p(SIL) MMHFMs was enhanced by 33% compared to that of p(SIL) HFMs. However, chain rigidification phenomenon was observed which cause the ZIF-8/p(SIL) MMHFMs showed the decreasing CO2 permeance when the ZIF-8 content was increased. The best separation performance of ZIF-8/p(SIL) MMHFMs was obtained with 0.5 wt% ZIF-8 addition, which exhibited a CO2 permeance and CO2/N2 selectivity of 6 GPU and 30. Therefore, adding ZIF-8 into p(SIL) HFMs to form the ZIF-8/p(SIL) MMHFMs is beneficial to enhance the CO2 permeance of membranes because of the characteristic of the pore size of 3.4 Å and transport pathway provided by ZIF-8 fillers.

On performance of polycarbonate/silica aerogel nanoparticle mixed matrix hollow fiber membrane coated with polydimethylsiloxane for membrane distillation

AbstractThe membrane distillation process is one of the most important membrane technologies being developed for water desalination, which has the ability to compete with expensive processes such as reverse osmosis. In this study, the performance of polycarbonate (PC) hollow fiber membranes modified with silica aerogel nanoparticles (SIA‐NPs) and polydimethylsiloxane (PDMS) coating solution for direct contact membrane distillation was investigated. The membranes were fabricated by dry jet‐wet spinning method. In this respect, 0.25, 0.5, and 1 wt% of SIA nanoparticles were coated over the hollow fiber surface in order to improve the performance of the membranes. The results indicated that the optimum loading of SIA was 0.5 wt% at which the contact angle of the surface shifted from 77.5° to 100° relative to the unmodified PC membrane. Although the addition of SIA nanoparticles to the membrane matrix did not alter the membrane conductivity, it increased the membrane thickness, thereby reduced the heat loss of the membrane. Accordingly, the results of performance tests for the membrane distillation (MD) showed that by adding 0.5% SIA nanoparticles to the membrane bulk and coating the surface with 0.5% SIA nanoparticles in 1.0% PDMS solution and 96% increase in energy efficiency, 33% increase in water flux, as well as higher stability of salt rejection were obtained. This study proved that the application of SIA nanoparticles have a great potential to modify and improve MD performance.