Performance Of Mixed Matrix Membranes Research Articles

Enhancing CO2 separation performance of mixed matrix membranes by incorporation of L-cysteine-functionalized MoS2

The incorporation of lamellar materials into polymer matrix can improve the gas separation performance of mixed matrix membranes (MMMs), which have great potential in chemical separation process. However, few intrinsic selectivity sites on MoS2 sheets suppress further employment in the membrane separation. In this work, the vacancies and defects-containing MoS2 sheets were prepared by high temperature oxidation and hydrothermal reaction in NaOH solution, and then L-cysteine-functionalized MoS2 (Cys-MoS2) was synthesized by a thiol-click chemistry reaction between S vacancies and thiol groups as confirmed by transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N2 absorption. After blending with polyether-block-amide (Pebax), the as-prepared MMMs showed outstanding mechanical properties as a result of the homogeneous dispersion of Cys-MoS2 and hydrogen bonding between two phases as evidenced by attenuated total reflectance-FTIR, scanning electron microscope (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The highest permeability of 297 Barrer accompanied with a CO2/N2 selectivity of 120 was obtained for MMMs loaded with 1.5 wt% Cys-MoS2, which were enhanced by 206.2 % and 124.7 % over the pristine Pebax membrane, respectively. Meanwhile, this value was superior to that of the previously reported Pebax-based MMMs, transcending 2019 upper bound. The enhanced gas separation performance is due to the improved CO2 adsorption selectivity by the vacancies and defects of Cys-MoS2, while the amine groups carrier enhanced CO2 reactivity selectivity.

Constructing rapid water vapor transport channels within mixed matrix membranes based on two-dimensional mesoporous nanosheets

Membrane technology is an effective strategy for gas dehumidification and fuel cell humidification. In this study, cerium fluoride oxide (F-Ce) two-dimensional (2D) mesoporous nanosheets and their composite with 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCA]) ionic liquids (ILs) (IL@F-Ce) are introduced as fillers into polyether block amide (PEBAX® 1074) to fabricate mixed matrix membranes (MMMs). The slit-shaped mesoporous structure of the nanosheets facilitates the construction of water vapor rapid transport channels in MMMs. The permeability and selectivity of water vapor for MMMs loaded with F-Ce nanosheets are greatly improved, and the performance of MMMs loaded with IL@F-Ce nanosheets are much better than the former. Particularly, the MMM with IL@F-Ce content of 4 wt.% achieves the highest H2O permeability of 4.53 × 105 Barrer, which is more than twice that of the pure PEBAX membrane, and the selectivity is increased by 83%. Thus, the MMMs based on 2D mesoporous nanosheets have considerable potential application in industrial-scale dehydration and humidification processes.

A polyimide/poly(N-vinylimidazole) membrane for CO2/CH4 separation with high selectivity and permeability

Membranes with both good permeation and selectivity are highly desired for gas separations. In this study, we synthesized a new 6FDA-type polyimide copolymer 6FDA-BDTA-ODA, and then an organic polymer of poly ( N-vinylimidazole) was doped into the polyimide to prepare mixed matrix membranes (MMMs). We also studied the effect of poly ( N-vinylimidazole) contents on the separation performance of MMMs. The results showed that the ideal selectivity for CO2/CH4 was improved by adding the poly ( N-vinylimidazole) filler. The ideal selectivity reached 63.5 with 6 wt% poly ( N-vinylimidazole) loading with the permeability of 29.2 Barrer. The highly permeable MMMs showed a considerably enhanced performance for CO2/CH4 that close to the 2008 Robeson upper-bound. The gas separation performance of the prepared MMMs for CO2/CH4 was improved compared to that of the pure polymer membrane, indicating that the copolyimide/poly ( N-vinylimidazole) MMMs have promising applications in CO2/CH4 gas separation.

MOF/Polymer Mixed-Matrix Membranes Preparation: Effect of Main Synthesis Parameters on CO2/CH4 Separation Performance.

Design and preparation of mixed-matrix membranes (MMMs) with minimum defects and high performance for desired gas separations is still challenging as it depends on a variety of MMM synthesis parameters. In this study, 6FDA-DAM:DABA based MMMs using MOF-808 as filler were prepared to examine the impact of multiple variables on the preparation process of MMMs, including variation in polymer concentration, filler loading, volume of solution cast per membrane area, solvent type used and solvent evaporation rate, and to identify their impact on the CO2/CH4 separation performance of these membranes. Solvent evaporation rate proved to be the most critical synthesis parameter, directly influencing the performance and visual appearance of the membranes. Although less dominantly influencing the MMM performance, polymer concentration and solution volume also had an important role via control over the casting solution viscosity, particle agglomeration, and particle settling rate. Among all solvents studied, MMMs prepared with chloroform led to the best performance for this polymer-filler system. Chloroform-based MMMs containing 10 and 30 wt.% MOF-808 showed 73% and 62% increase in CO2 permeability, respectively, without a decrease in separation factor compared to unfilled membranes. The results indicate that enhanced gas separation performance of MMMs strongly depends on the cumulative effect of various synthesis parameters rather than individual impact, thus requiring a system-specific design and optimization.

Influence of zwitterionic structure design on mixed matrix membrane stability, hydrophilicity, and fouling resistance: A computational study

Zwitterion-based mixed matrix membranes (MMMs) with designed characteristics of enhanced water flux, selectivity, and fouling mitigation have emerged as a new class of advanced membranes for oilsands process-affected wastewater (OSPW) treatment. Zwitterions (ZW) characterized by super-hydrophilicity and excellent fouling resistance have gained increasing attention in membrane modification research. In general, zwitterion properties are determined by the chemistry and structural properties of its constituents, including the polymer backbone, charged moieties, spacers, as well as molecular configuration. This study used molecular dynamics simulation (MDS) to investigate the effects of polymer backbone (PB), spacer length (SL), and spacer chemistry (SC) on ZW-based MMM properties such as stability, hydrophilicity, and oil-antifouling potentiality. Membrane performance was also assessed at high temperatures (50, 70, and 90 °C. The results suggest PB, SL, and SC all influence the resultant MMM performance, with SL being the most impactful structural parameter on stability and hydrophilicity. Variation of SL was suspected to alter the ionic association and partial charges of zwitterionic moieties, which affect their ability to interact with the polymer network and water molecules. Spacer chemistry (i.e., hydroxyl (-OH) groups) can initiate self-association between zwitterionic charged groups having short SL, lessening their inter-molecular networking ability. However, for ZWs with long SL, the presence of hydroxyl groups on the spacer can result in the formation of hydrogen bonds and/or electrostatic interactions with other ZW molecules and polyvinylidene difluoride (PVDF) polymer chains or water molecules, improving membrane stability and hydrophilicity. High temperatures reduced membrane stability but to a lesser extent for MMMs compared to unmodified PVDF membrane. While temperature greatly influenced membrane hydrophilicity, the impacts were membrane-specific. The oil-fouling propensity of pristine PVDF membrane increased with temperature but of MMMs appeared stable across the temperature range studied.

Ultrathin Ni-Co nanosheets with disparate-CO2-affinity nanodomains in membranes to improve gas separation

One of the biggest challenges of Pebax-based membranes is how to simultaneously achieve high CO2 permeability and selectivity. Hence, mixed matrix membranes (MMMs) were designed and fabricated by incorporating the ultrathin Ni-Co nanosheet (Ni-Co-NS) fillers into Pebax® MH 1657 (Pebax) matrix to improve CO2 separation performance. The ultrathin Ni-Co-NS fillers had disparate-CO2-affinity nanodomains and were endowed with three main functions in the Pebax/Ni-Co-NS MMMs: i) First, Ni and Co metals constituted CO2-philic and non-CO2-philic nanodomains, respectively, because the two metals had disparate CO2 adsorption enthalpy. CO2-philic nanodomains rendered a high affinity capacity, whereas non-CO2-philic nanodomains rendered low-friction diffusion. Thus, a combination of the disparate-CO2-affinity nanodomains significantly facilitated CO2 transport. ii) Second, the pore size of the nanosheets decreased from 0.79 nm to 0.49 nm by introducing the second Co metal into Ni-NS, and the decreased pores size contributed to strengthen CO2/CH4 selectivity. iii) Third, the uniform nanopores of Ni-Co-NS that paralleled to the gas concentration gradient constituted high-speed CO2 transport channels, which was conducive to improving CO2 permeability of MMMs. Therefore, CO2 separation performance of MMMs was remarkably improved by Ni-Co-NS fillers. Pebax/Ni-Co-NS MMMs with the content of 5 wt% Ni-Co-NS fillers showed the highest CO2 permeability of 483 ± 11 Barrer and CO2/CH4 selectivity of 39 ± 1.1. It implies that the introduction of nanosheets with two different metals is an effective method to fabricate MMMs with an excellent CO2 separation performance.

Efficient separation of methanol/dimethyl carbonate mixtures by UiO-66 MOF incorporated chitosan mixed-matrix membrane

Pervaporation shows great potential in separation of organic-organic mixtures that are widely involved in chemical and petrochemical industries, while the separation performance of polymeric membranes is undesirable for practical application. In this work, we incorporated UiO-66 (ZrCl4) metal-organic frameworks (MOFs) into chitosan (CS) membrane to separate methanol-dimethyl carbonate (DMC) mixtures. ZrOCl2·8H2O or ZrCl4 was selected as metal precursor to synthesize UiO-66, which aimed to investigate the structural defect of UiO-66 for the separation performance of mixed matrix membranes (MMMs). BET, 1H NMR and low-angle XRD characterizations indicated that UiO-66 (ZrCl4) with appropriate pore size is more suitable for preferentially permeate methanol over DMC. IR, dielectric relaxation and DSC characterizations combined with molecular simulations revealed the ideal interfacial morphology of UiO-66/CS MMMs was owing to the favorable molecular interactions including hydrogen bond interaction and van der Waals interaction. Pervaporation separation of methanol-DMC mixtures demonstrated that UiO-66 (ZrCl4) nanofillers can simultaneously enhance the permeation flux and separation factor of CS membrane. The optimized 10 wt% UiO-66 (ZrCl4)/CS MMM exhibited total flux and methanol/DMC separation factor of 355 g/m2h and 337 for 10 wt% methanol-DMC mixtures at 50 °C, which were 3.4-fold and 25-fold higher than that of the pure CS membrane, respectively, and outperformed the state-of-the-arts polymer-based membranes.

Enhanced CO2-capture performance of polyimide-based mixed matrix membranes by incorporating ZnO@MOF nanocomposites

Mixed matrix membranes (MMMs) have received numerous interests as promising membrane configurations for dealing with the energy-intensive gas separation processes. In this study, MMMs were fabricated by incorporating novel ZnO@MOF nanocomposites (ZnO@ZnBDC) into Matrimid (PI) matrix. The physico-chemical properties and microstructures of ZnO@ZnBDC nanocomposites and ZnO@ZnBDC/PI MMMs were characterized. The CO2/CH4 separation performance of MMMs was evaluated and analyzed according to the solution-diffusion mechanism. ZnBDC in the nanocomposites increased CO2 permeability by providing mass transfer pathways with low resistance in the MMMs, while ZnO increased the CO2/CH4 selectivity via high CO2 affinity. Owing to the synergistic effect of the nanocomposites, MMMs with 0.75 wt% ZnO@ZnBDC showed CO2 permeability of 11.5 Barrer and CO2/CH4 selectivity of 39.5, which increased by 67% and 33%, respectively, by comparing with control PI membrane.

PVA-Based MMMs for Ethanol Dehydration via Pervaporation: A Comparison Study between Graphene and Graphene Oxide

Two different types of 2D nanosheets, including hydrophobic graphene (GR) and hydrophilic graphene oxide (GO), were filled into poly (vinyl alcohol) (PVA) polymers to prepare mixed matrix membranes (MMMs) for ethanol dehydration via pervaporation. The relationship between the physical/chemical properties of graphene and pervaporation performance of MMMs was investigated by a comparison of GR/PVA and GO/PVA MMMs in microstructure and PV performance. The incorporation of GO nanosheets into PVA reduced PVA crystallinity and enhanced the membrane hydrophilicity, while the incorporation of GR into PVA led to the opposite results. The incorporation of GR/GO into PVA depressed the PVA membrane swelling degree, and the incorporation of GR showed a more obvious depression effect. GR/PVA MMMs showed a much higher separation factor than GO/PVA MMMs, while they exhibited a much lower permeation flux than GO/PVA MMMs and pristine PVA membranes. The huge difference in microstructure and performance between GO/PVA and GR/PVA MMMs was strongly associated with the oxygen-containing groups on graphene lamellae. The higher permeation flux of GO/PVA MMMs was ascribed to the facilitated transport of water molecules induced by oxygen-containing groups and exclusive channels provided by GO lamellae, while the much lower permeation flux and higher separation factor GR/PVA MMMs was resulted from the smaller GR interplanar spacing (0.33 nm) and hydrophobicity as well as barrier effect of GR lamellae on the sorption and diffusion of water molecules. It was presumed that graphene intercalated with an appropriate number of oxygen-containing groups might be a good choice to prepare PVA-based MMMs for ethanol dehydration, which would combine the advantages of GR’s high interlayer diffusion selectivity and GO’s high permeation properties. The investigation might open a door to achieve both of high permeation flux and separation factor of PVA-based MMMs by tuning the microstructure of graphene.

Enhancing enrichment ability of Co-Al- layered double hydroxides-mixed matrix membrane microextraction by deep eutectic solvent for analysis of warfarin in biological samples and its quantification via high-performance liquid chromatography-ultraviolet detection

Recent studies on the use of mixed-matrix membrane (MMM) in microextraction methods have considered the use of membrane extraction phase with wide surfaces and high porosity. Here, for the first time, the effect that deep eutectic solvents (DESs) have on the performance of MMM was investigated. The Co-Al-layered double hydroxides mixed matrix membrane (CO-Al-LDH-MMM) was prepared by immobilization of LDH on the pores of the hollow fiber membrane and used as a microextraction device. Deep eutectic solvent via hydrophilic and π-π interactions, aided the dissolution of analyte in the fiber membrane lumen and increases their adsorption onto LDH. Thus, a microextraction method based on the novel LDH-MMM–deep eutectic solvent (LDH-MMM-DES) system was developed and used for the extraction, preconcentration, and quantification of warfarin (as a model analyte) in biological samples. The principal variables that affective influence microextraction efficiency, including the extraction time, type of DES, stirring rate, desorption time, type of eluent solvent, and pH of the sample solution, were screened via Plackett-Burman design and then variables effective optimized by Box-Behnken design. Under the optimum conditions obtained, the developed method showed a good working range (R2 ≥ 0.9951). The limit of detection (LOD) and the limit of quantification (LOQ) ranged from 0.03 μg L−1 (water) to 0.30 μg L−1 (human plasma sample) and from 0.099 μg L−1 (water) to 0.999 μg L−1 (human plasma sample) variables, respectively. The intraday precision was in the range of 2.5–5.6. In order to experiment with the precision and applicability of the Co-Al LDH-MMM DES method, spiking recovery studies were performed in biological samples (urine and humane plasma samples). The recovery results for urine and plasma samples were calculated as 90–91% and 88–93 %, respectively. The results confirmed that the presented method would be promising for the analysis of warfarin in biological samples.

Enhancing So2 Separation Performance of Mixed-Matrix Membrane with P-Aminoazobenzene Decorated Photosensitive Metal-Organic Framework Additives

Enhancing So2 Separation Performance of Mixed-Matrix Membrane with P-Aminoazobenzene Decorated Photosensitive Metal-Organic Framework Additives

Veiled metal organic frameworks nanofillers for mixed matrix membranes with enhanced CO2/CH4 separation performance

The interfacial compatibility between fillers and polymers essentially influences the separation performance of mixed matrix membranes (MMMs). In this work, an one-pot synthesized functional layer veiled zeolite imidazolate frameworks-67 (VZIF-67) was used as an efficient nanofillers to fabricate MMMs via physical blending with 6FDA-Durene polyimide. Benefiting from the CO2 affinity from functional layer and the intrinsic characteristics of porous nanofillers, significant enhancement on separation performance was observed on the resultant MMMs. Specifically, the optimized VZIF-67 MMMs (30 wt% loading) exhibited CO2/CH4 selectivity of 32.5 with CO2 permeability of 1210 Barrer, which is 1.7 and 1.5 times higher than those of the control membrane, respectively. More importantly, the surface organic attribute and abundant amine groups of VZIF-67 reinforced the interfacial compatibility between the nanofillers and polymer matrix, leading to a doubled CO2/CH4 selectivity compared with the ZIF-67 MMMs. Overall, the performance of the VZIF-67 membrane toward CO2/CH4 separation surpasses the 2008-updated Robeson upper bound. These results indicate the functionalization strategy on porous nanofillers is a promising approach to fabrication of high performance of MMMs.

A Highly Permeable Mixed Matrix Membrane Containing a Vertically Aligned Metal–Organic Framework for CO2 Separation

Delicately regulating the distribution morphology of a filler is an effective strategy to promote the separation performance of mixed matrix membranes (MMMs). Herein, we describe a highly permeable metal-organic framework (MOF)-based MMM comprising vertically aligned ZIF-8 (V-ZIF-8) and polysulfone (PSF). The V-ZIF-8 is distributed uniformly within the PSF matrix. With this unique distribution morphology of ZIF-8, the shortest gas transport pathways are formed in the membrane. Meanwhile, the molecular-sieving pores of ZIF-8 can allow CO2 to pass through and crowding out N2. The obtained V-ZIF-8/PSF membrane shows a high CO2 permeability of 89.7 Barrer and a CO2/N2 selectivity of 30.0 that is stable over a period of 50 h. The CO2 permeability is enhanced about 11.8 times than that of the pure PSF membrane. The results prove that the vertically aligned distribution morphology of an MOF in a polymer matrix is an effective method to improve the separation performance of a membrane, providing a new concept for designing more advanced membranes.

Simultaneous degumming and deacidification of crude palm oil using mixed matrix PVDF membrane

The research work aimed to investigate the compatibility of polyvinylidene difluoride (PVDF) membrane embedded with various inorganic adsorbents for producing a mixed matrix membrane (MMM) and to examine the capability of mixed matrix PVDF membrane (PVDF-MMM) for simultaneous degumming and deacidification of crude palm oil (CPO). Four different adsorbent were tested which includes calcium silicate (CaS), magnesium silicate (MagS), ZSM-zeolite (ZSM) and activated carbon (AC). The in-house made PVDF-MMM was fabricated according to the dry-jet wet spinning method. The performances of these PVDF-MMMs were assessed with respect to the removals of phosphorus, FFA and colour. Based on finding showed that the combination of 18PVDF embedded with 3 wt% MagS showed the most compatible polymer-inorganic hybrid MMM to perform pre-treatment of CPO. Increasing the MagS concentration from 3 to 8 wt% in the polymer matrix recorded the highest removals of FFA at 16.51 %, phospholipid at 93.31 % and colour at 18.8 %, respectively. Nevertheless, high amount of MagS added to the polymer matrix affected the spinnability and reproducibility performance of MMM. Future work, surface modifications of inorganic adsorbent can be evaluated to facilitate good dispersion of filler in polymer matrix during membrane fabrication to maintain good membrane reproducibility.

Constructing MOF-doped two-dimensional composite material ZIF-90@C3N4 mixed matrix membranes for CO2/N2 separation

Two-dimensional nanomaterials have the characteristics of high aspect ratio and high space utilization, which has huge potential advantages in gas separation. In this work, g-C3N4 two-dimensional nanosheets with sieving pore structure were selected as templates and combined with ZIF-90 to construct a 0-dimensional/2-dimensional composite material ZIF-90@C3N4 (ZCN). The complete two-dimensional g-C3N4 nanosheets were stripped under acid etching conditions at 25 °C. ZIF-90 was distributed in an orderly manner on the two-dimensional nanosheets, and the nanosheets were spread out due to the growth of ZIF-90 to provide more free volume. The gas permeation experiment proved that the ZCN has a better CO2/N2 separation performance. The ZCN/Pebax mixed matrix membrane (MMM) with the optimized 8.0 wt% ZCN loading showed an improved CO2 permeability of 110.5 Barrer and a CO2 /N2 selectivity of 84.4, surpassing the Robeson upper bound (2008). The results demonstrated that the designed composite filler with 2D nanosheets is an effective strategy to enhance gas separation performance of MMMs and verified the application potential in gas purification industry.

Amino-functionalized NUS-8 nanosheets as fillers in PIM-1 mixed matrix membranes for CO2 separations

Membrane-based separation technologies are promising for various applications such as carbon capture and storage (CCS). Herein, we report the preparation and performance of mixed matrix membranes (MMMs) for carbon dioxide (CO2) separation. The MMMs comprise amino-functionalized metal-organic framework (MOF) nanosheets (NUS-8-NH2) dispersed in the polymer of intrinsic microporosity 1 (PIM-1). Specifically, the MOF nanosheets were synthesized through a bottom-up method and introduced into the PIM-1 matrix to fabricate NUS-8-NH2/PIM-1 MMMs. The uniformly dispersed MOF nanosheets could afford additional fast transport pathways through intra-flake pores and inter-flake nano-channels. Moreover, the amino groups could enhance CO2 transport within NUS-8-NH2/PIM-1 MMMs. In addition, hydrogen bonding between the NUS-8-NH2 filler and PIM-1 matrix improved interfacial compatibility. Therefore, the as-prepared MMMs could achieve a high filler loading of 15 wt% without sacrificing separation performance. Compared with the pure PIM-1 membrane, the MMM with 10 wt% NUS-8-NH2 showed CO2 permeability of ∼14000 Barrer and a CO2/N2 selectivity of ∼30, surpassing the 2008 Robeson's upper bound.

Fabrication and dialysis performance of functionalized multiwall carbon nanotubes integrated cellulose acetate/poly(vinylpyrrolidone) membranes

Mixed matrix membranes (MMMs) of cellulose acetate/poly(vinylpyrrolidone) (CA/PVP) infused with acid functionalized multiwall carbon nanotubes (f-MWCNTs) were fabricated by an immersion phase separation technique for hemodialysis application. Membranes were characterized using FTIR, water uptake, contact angle, TGA, DMA and SEM analysis. The FTIR was used to confirm the bonding interaction between CA/PVP membrane matrix and f-MWCNTs. Upon addition of f-MWCNTs, TGA thermograms and glass transition temperature indicated improved thermal stability of MMMs. The surface morphological analysis demonstrated revealed uniform distribution of f-MWCNTs and asymmetric membrane structure. The water uptake and contact angle confirmed that hydrophilicity was increased after incorporation of f-MWCNTs. The membranes demonstrated enhancement in water permeate flux, bovine serum albumin (BSA) rejection with the infusion of f-MWCNTs; whereas BSA based anti-fouling analysis using flux recovery ratio test shown up to 8.4% improvement. The urea and creatinine clearance performance of MMMs were evaluated by dialysis experiment. It has been found that f-MWCNTs integrated membranes demonstrated the higher urea and creatinine clearance with increase of 12.6% and 10.5% in comparison to the neat CA/PVP membrane. Thus, the prepared CA/PVP membranes embedded with f-MWCNTs can be employed for wide range of dialysis applications.

A Novel Composite Material UiO-66@HNT/Pebax Mixed Matrix Membranes for Enhanced CO2/N2 Separation.

Mixing a polymer matrix and nanofiller to prepare a mixed matrix membrane (MMM) is an effective method for enhancing gas separation performance. In this work, a unique UiO-66-decorated halloysite nanotubes composite material (UiO-66@HNT) was successfully synthesized via a solvothermal method and dispersed into the Pebax-1657 matrix to prepare MMMs for CO2/N2 separation. A remarkable characteristic of this MMM was that the HNT lumen provided the highway for CO2 diffusion due to the unique affinity of UiO-66 for CO2. Simultaneously, the close connection of the UiO-66 layer on the external surface of HNTs created relatively continuous pathways for gas permeation. A suite of microscopy, diffraction, and thermal techniques was used to characterize the morphology and structure of UiO-66@HNT and the membranes. As expected, the embedding UiO-66@HNT composite materials significantly improved the separation performances of the membranes. Impressively, the as-obtained membrane acquired a high CO2 permeability of 119.08 Barrer and CO2/N2 selectivity of 76.26. Additionally, the presence of UiO-66@HNT conferred good long-term stability and excellent interfacial compatibility on the MMMs. The results demonstrated that the composite filler with fast transport pathways designed in this study was an effective strategy to enhance gas separation performance of MMMs, verifying its application potential in the gas purification industry.

Effects of an Alternating Magnetic Field towards Dispersion of α-Fe2O3/TiO2 Magnetic Filler in PPOdm Polymer for CO2/CH4 Gas Separation.

Magnetic-field-induced dispersion of magnetic fillers has been proven to improve the gas separation performance of mixed matrix membranes (MMMs). However, the magnetic field induced is usually in a horizontal or vertical direction. Limited study has been conducted on the effects of alternating magnetic field (AMF) direction towards the dispersion of particles. Thus, this work focuses on the incorporation and dispersion of ferromagnetic iron oxide–titanium (IV) dioxide (αFe2O3/TiO2) particles in a poly (2,6-dimethyl-1,4-phenylene) oxide (PPOdm) membrane via an AMF to investigate its effect on the magnetic filler dispersion and correlation towards gas separation performance. The fillers were incorporated into PPOdm polymer via a spin-coating method at a 1, 3, and 5 wt% filler loading. The MMM with the 3 wt% loading showed the best performance in terms of particle dispersion and gas separation performance. The three MMMs were refabricated in an alternating magnetic field, and the MMM with the 3 wt% loading presented the best performance. The results display an increment in selectivity by 100% and a decrement in CO2 permeability by 97% to an unmagnetized MMM for the 3 wt% loading. The degree of filler dispersion was quantified and measured using Area Disorder of Delaunay Triangulation mapped onto the filler on binarized MMM images. The results indicate that the magnetized MMM presents a greater degree of dispersion than the unmagnetized MMM.

A comparative study for the rejection of nickel ions from waste water by PES, fMWCNTs/PES, TiO2/PES and TiO2-fMWCNTs/PES mixed matrix membranes

In this study, the neat polyethersulfone (PES) membrane and the mixed matrix membranes (MMMs) containing 20 wt. %polyethersulfone (PES) and different amounts of functionalized multi-walled carbon nanotubes (fMWCNTs), TiO2, and TiO2 coated on fMWCNTs were fabricated by wet phase inversion and conventional casting methods. The nickel ions rejection and permeate flux performance were then investigated and compared by these fabricated membranes. The characteristics of the membranes were performed by field emission scanning electron microscopy (FESEM), transmissionelectron microscopy (TEM), and contact angle (CA) measurement. The operational parameters such as polymer concentration, pressure, pH, time and nickel ion concentration for nickel ions rejection and permeability were firstly optimized on the neat PES membrane. The performance of MMMs containing various amounts of nanoparticles was then evaluated and compared under these optimized conditions. The obtained results indicated that the membrane containing 20 wt. % PES, and operational conditions like pressure 15bar, low concentration of nickel, time =30min, and various amounts of pH were the best conditions to achieve the highest rejection percentage of nickel ions and permeate flux. In such operational conditions, PES/fMWCNTs and PES/TiO2 membranes have the highest nickel ion rejection and permeate flux, respectively. Totally the prepared mixed matrix membranes showed that they have higher ability to reject nickel ions from wastewater and a higher permeate flux value compared with the neat PES membrane.