An atomistic simulation towards molecular design of silica polymorphs nanoparticles in polysulfone based mixed matrix membranes for CO2/CH4 gas separation

Incorporation of inorganic fillers into Polysulfone (PSF) to constitute mixed matrix membranes (MMMs) has become a viable solution to prevail over limitations of the pristine materials in natural gas sweetening process. Nevertheless, preparation of MMMs without defects and empirical investigation of membrane that exhibits characteristic of improved CO₂/CH₄ separation performance at experimental scale are difficult that require prior knowledge on compatibility between the filler and polymer. A computational framework has been conducted to construct validated PSF based MMMs using silica (SiO₂) as inorganic fillers. It is known that nanosized SiO₂ can coexist in varying polymorph configurations (ie, α-Quartz, α-Cristobalite, α-Tridymite) but molecular simulation study of SiO₂ polymorphs to form MMMs is limited. Therefore, this work is a pioneering study to elucidate feasibility in facile utilization of polymorphs to improve gas separation performance of MMMs. Physical properties and gas transport behavior of the simulated PSF based MMMs with different SiO₂ polymorphs and loadings have been elucidated. The optimal MMM has been found to be PSF/25 wt% α-Cristobalite at 55°C. The success in molecular simulation has shed light on how computational tools can provide understandings at molecular level to elucidate compatibility between varying pristine materials to MMMs for natural gas processing.     

Amine-impregnated natural zeolite as filler in mixed matrix membranes for CO2/CH4 separation

Flat mixed matrix membranes (MMMs) comprising polysulfone and clinoptilolite-type natural zeolite were prepared by casting. Zeolite was modified with three alkylamines: ethanolamine (EA), bis(2-hydroxypropyl)amine (BHPA), and polyethylenimine (PEI) by the impregnation method. Impregnated zeolite samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and N₂ adsorption–desorption. The alkylamine loading extent determined by thermogravimetric analysis was 5.2, 4.8, and 8.5% for EA, BHPA, and PEI, respectively. Analyses of MMMs showed that the incorporation of impregnated zeolite affected the glass-transition temperature (T_g) and mixed-gas transport properties. In this regard, a decreasing trend of the T_g values from 185.5 °C for the polymeric membrane up to 176.6 °C for Clino-EA-based MMM was recorded. In addition, the gas separation performance was evaluated at two different feed pressures. At 50 psi, MMMs showed an enhancement up to 30% on the CO₂ permeability (22.79 Barrer) and 55% on the CO₂/CH₄ selectivity (45.78) in comparison with the polymeric membrane (CO₂ permeability 17.34 Barrer; CO₂/CH₄ selectivity 29.38). These values varied depending on the alkylamine, BHPA being the most selective. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48286.     

Effect of gas permeation temperature and annealing procedure on the performance of binary and ternary mixed matrix membranes of polyethersulfone,SAPO‐34, and 2‐hydroxy 5‐methyl aniline

This study investigated the effect of annealing time and temperature on gas separation performance of mixed matrix membranes (MMMs) prepared from polyethersulfone (PES), SAPO‐34, and 2‐hydroxy 5‐methyl aniline (HMA). A postannealing period at 120°C for a week extensively increased the reproducibility and stability of MMMs, but for pure PES membranes no post‐annealing was necessary for stable and reproducible performance. The effect of operation temperature was also investigated. The permeabilities of H₂, CO₂, and CH₄ increased with increasing permeation temperature from 35°C to 120°C, yet CO₂/CH₄ and H₂/CH₄ selectivities decreased. PES/SAPO‐34/HMA ternary and PES/SAPO‐34 binary MMMs exhibited the highest ideal selectivity and permeability values at all temperatures, respectively. For H₂/CO₂ pair, when temperature increased from 35°C to 120°C, selectivity increased from 3.2 to 4.6 and H₂ permeability increased from 8 to 26.5 Barrer for ternary MMM, demonstrating the advantage of using this membrane at high temperatures. The activation energies were in the order of CH₄ > H₂ > CO₂ for all membranes. PES/SAPO‐34/HMA membrane had activation energies higher than that of PES/SAPO‐34 membrane, suggesting that HMA acts as a compatibilizer between the two phases. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40679.     

Polymer multilayer films for high temperature capacitor application

Advanced film capacitors require polymers with high thermal stability, high breakdown strength, and low loss for high temperature dielectric applications. To fulfill such requirements, two polymer multilayer film systems were coextruded via the forced assembly technique. High glass transition temperature (T _g) polycarbonate (HTPC, T_g = 165 °C) and polysulfone (PSF, T_g = 185 °C) were multilayered with a high dielectric constant polymer, poly(vinylidene fluoride) (PVDF), respectively. The PSF/PVDF system was more thermally stable than the HTPC/PVDF system because of the higher T_g for PSF. At temperatures lower than 170 °C, the HTPC/PVDF system exhibited comparable breakdown strength and hysteresis loss as the PSF/PVDF system. While at temperatures above 170 °C, the PSF/PVDF system exhibited a higher breakdown strength because of the higher T_g of PSF. The electric displacement-electric field (D-E) loop behavior of the PSF/PVDF system was studied as a function of temperature. Moreover, a melt-recrystallization process could further decrease the hysteresis loss for the PSF/PVDF system due to better edge-on crystal orientation. These results demonstrate that PSF/PVDF and HTPC/PVDF systems are applicable for high temperature film capacitors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47535.     

Poly(vinyl alcohol)/ZIF‐8‐NH2 mixed matrix membranes for ethanol dehydration via pervaporation

Ethanediamine‐modified zeolitic imidazolate framework (ZIF)‐8 particles (ZIF‐8‐NH₂) is synthesized and incorporated in the poly(vinyl alcohol) (PVA) matrix to fabricate novel PVA/ZIF‐8‐NH₂ mixed matrix membranes (MMMs) for pervaporation dehydration of ethanol. The PVA/ZIF‐8‐NH₂ MMMs exhibit enhanced membrane homogeneity and separation performance because of the higher hydrophilicity and restricted agglomeration of the particles, as compared to corresponding MMMs loaded with unmodified particles. The effect of ZIF‐8‐NH₂ loading in the MMMs is studied and the MMM with a 7.5 wt % ZIF‐8‐NH₂ loading shows the best pervaporation performance for ethanol dehydration at 40°C. Various characterization techniques (Fourier transform infrared, scanning electron microscope, contact angle, sorption test, etc.) are used to investigate the MMMs loaded with ZIF‐8 and ZIF‐8‐NH₂ particles. The impact of operation conditions on pervaporation performance is also performed. The performance benchmarking shows that the MMMs have superior separation factors and comparable flux to most other PVA hybrid membranes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1728–1739, 2016     

Iron oxide nanoparticles improved biocompatibility and removal of middle molecule uremic toxin of polysulfone hollow fiber membranes

Middle molecule uremic toxins constitute to a quarter of uremic toxins present in human blood. In a condition where these uremic toxins accumulate in bloodstream due to renal failure, blood purification process using a high performance membrane is required. Here, we develop biocompatible mixed matrix membranes (MMMs) made up of polysulfone (PSf) and iron oxide nanoparticles (Fe₂O₃ NPs) with the focus to remove middle molecule uremic toxin effectively. The MMMs were evaluated in terms of their biocompatibility and separation performance. At higher Fe₂O₃ NPs loading, the MMM displayed a huge reduction of protein adsorption and platelet adhesion while maintaining normal blood coagulation time and acceptable complement activation. The optimized MMM exhibited high permeability (110.47 L m⁻² h⁻¹ bar⁻¹), protein retention (99.9%) and demonstrated excellent clearance of urea (82%) and lysozyme (46.7%). The PSf/Fe₂O₃ MMM is proven to have promising attributes for hemodialysis application. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48234.     

Comparison of thermal degradation characteristics of poly(arylene sulfone)s using thermogravimetric analysis/mass spectrometry

Thermal degradation of poly(arylene sulfone)s had been studied by the combination of thermogravimetric analysis/mass spectrometry (TG/MS) with pyrolysis/gas chromatography/mass spectrometry (Py‐GC/MS) techniques. Through these two methods, the pyrolysates from poly(ether sulfone) (PES) and polysulfone (PSF) were identified in 11 and 21 sets of evolution curves, respectively, from room temperature to 900 °C. Among these pyrolysates, 12 products from PES and 25 products from PSF were obtained. The major mechanism for both PES and PSF was one‐stage pyrolysis involving main chain random scission and carbonization with evolution of SO₂ and phenol as major products. Although the initial thermal stability of PES was lower than that of PSF, the formation of sulfide groups in the condensed phase from PES, through reduction of sulfone group by hydrogen radicals, increased the fire retardation behavior of PES. In PES, the ether and sulfone groups showed similar thermal stability. The thermal stability of functional groups in PSF were in the order of sulfone < ether < isopropylidene group. The scission of the ether group in PSF, with evolution of phenol as the major product, reached maximum evolution amount at the temperature of the maximum thermogravimetry loss of TG (T_max). The scission of isopropylidene groups at high temperature (>580 °C) evolved higher mass derivatives that lower the fire retardancy of PSF. By using a simplified kinetic model, PES showed maximum activation energy with a conversion ratio of 0.2–0.3, which implies a high fire retardant effect of sulfide formation in PES. A comparative study with the proposed model and experimental data showed the theoretical pyrolysis curves to be in agreement with the experimental curves for PES and PSF pyrolysis, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2387–2398, 2001     

A polyvinyl alcohol-based mixed matrix membrane with uniformly distributed Schiff base network-1 for ethanol dehydration

In this study, Schiff base network (SNW)-1 nanoparticles with high hydrophilicity and large specific surface area were used to prepare polyvinyl alcohol (PVA)-based mixed matrix membranes (MMMs), which were evaluated for ethanol dehydration. Because of the low difference of density between SNW-1 and PVA, the as-prepared nanoparticles can be uniformly distributed into the PVA active layer. The effects of SNW-1 loading, feed temperature, and water concentration on pervaporation (PV) performance were further studied. The results showed the MMM with 10 wt% of SNW-1 loading exhibited a separation factor of 1,501 and a permeation flux of 187 g m⁻² h⁻¹ for feeding 95 wt% ethanol/water binary solution at 75°C. Overall, the SNW-1/PVA MMMs showed great prospect in ethanol dehydration via PV.     

Synthesis and Characterization of ETS-10/Chitosan Nanocomposite Membranes for Pervaporation

Chitosan (CS) and microporous titanosilicate ETS-10/CS mixed matrix membranes (MMMs) were prepared. The pervaporation performance was tested on the water-ethanol mixtures in the range 85–96 wt.% ethanol. The permeate flux increased from 0.45 to 0.55 kg m^?2 h^?1 at 50°C for the ETS-10/CS MMM with respect to the pure CS membranes. Characterization by SEM and TEM, XRD, DSC, and TGA allowed inferring an intimate contact between the dispersed ETS-10 and the continuous chitosan phase. The 5 wt.% loading of titanosilicate scarcely decreased the hydrophilic character of the mixed matrix membrane but increased the molecular sieving effect on the transport and separation properties, thus affecting the membrane behavior on pervaporation.     

Characterization of mixed matrix membranes by adsorption and fractal analysis

ABSTRACT

CO₂, CH₄ and N₂ adsorption properties of KFI- and RHO-polyvinyl acetate mixed matrix membranes (MMMs) were determined. A comparison was made between experimental and calculated adsorption capacities of the membranes. The fractal dimensions of the membranes were calculated from CO₂ adsorption data. A common discrepancy existed between experimental and calculated adsorption capacities of MMMs, which may be rationalized by the presence of an interphase between filler and polymer phases. The higher fractal dimension of KFI-polyvinyl acetate MMM, compared to RHO-polyvinyl acetate MMM indicated higher size sensitivity and thus an additional advantage for the adsorption of smaller molecules, such as CO₂.     

High-speed CO2 transport channel containing carboxymethyl chitosan/hydrotalcite membrane for CO2 separation

A comprehensive understanding of carboxymethyl chitosan (CMC)-based mixed matrix membrane (MMM) has been critically investigated. The present work elaborates the compatibility of hydrotalcite (HT) and CMC in terms of CO₂ separation application. Various spectroscopic and microscopic techniques have been utilized to characterize the respective properties of the prepared membrane. The temperature stability and moisture retention behavior of the membrane recognized itself as the flue gas separation membrane. The CO₂/N₂ separation experiment was performed on the MMM at different temperature (60–110 °C) and sweep/feed water flow to the saturator ratio (0.33 to 3). The membrane exhibited the optimum CO₂ permeance of 70 GPU at 90°C pertaining to water flow ratio of 2.33 (sweep/feed). The CO₂/N₂ selectivity observed at that same operating condition was 13. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48715.     

Fabrication of large diameter SiC monofilaments by polymer route

We demonstrate the possibility to fabricate SiC monofilaments with large diameters of 100 μm by a polymer route using a dry-spinning process. The properties of the spinning solution and the parameters of the spinning process were optimized to achieve a circular cross section of the spun filaments despite their large diameter. The evolution of the diameter and the mechanical properties of the filaments with pyrolysis temperature were studied. Filament shrinkage started above 400 °C. A radial shrinkage of about 25% was measured for pyrolysis temperatures of 1200 °C. The mechanical properties significantly start to increase at pyrolysis temperatures above 600 °C. At a diameter of 100 μm the filaments show a tensile strength of 620 MPa and a tensile modulus of 138 GPa after pyrolysis at 1200 °C. A decrease in the filament diameter leads to an improvement of the mechanical properties. We demonstrate the fabrication of these SiC monofilaments on spools.     

Improved sorption of reactive black 5 by date seed-derived biochar: isotherm,kinetic, and thermodynamic studies

ABSTRACT

In the present investigation, date seed-derived biochar was applied as economic and effective sorbent for remediation of reactive dye from contaminated solutions. Biochar produced at 350°C through pyrolysis process exhibited reactive black 5 (REB5) sorption capacity 2.7 times higher than virgin date seeds. The surface of biochar was analyzed through Fourier transform infrared and scanning electron microscope data. The maximum REB5 uptake determined through the Langmuir model was found to be 113.4 mg/g. The REB5 sorption kinetics were accurately described by the pseudo-first-order model than pseudo-second-order model. Thermodynamic parameters indicated that REB5 sorption was spontaneous, feasible, and endothermic process.     

Molecular transport through mixed matrix membranes: A time‐dependent density functional approach

The transport properties of gases in mixed matrix membranes (MMMs) are important in materials design. Here, a novel time‐dependent density functional theory (TDDFT) method to study the transport properties of gases in MMMs is developed. The MMM is modeled by inserting a spherical filler into the continuous polymer phase, which is similar to the Maxwell model; additionally, the inhomogeneity of the filler and the molecular correlations were taken into account in the TDDFT method. Transport properties such as permeation, density profile, flux, and chemical potential are examined and discussed. TDDFT prediction of the permeation is found to be higher than that of the Maxwell model, and the filler‐polymer interface is key to tuning this effect, which also seems to be the dominating factor in the transport process on both the microscopic and macroscopic scale. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4586–4594, 2017     

Improvement of polyimide/polysulfone composites filled with conductive carbon black as positive temperature coefficient materials

In this study, polyimide (PI)/polysulfone (PSF) blends filled with carbon black (CB) were developed for the use as positive temperature coefficient (PTC) materials in order to achieve the volume resistivity as lower than 10⁴ Ω.cm at room temperature. The weight ratios of PI/PSF were various from 100/0 to 10/90 with CB varied from 0 to 20 wt%. The use of conductive filler was reduced when PSF was blended with PI; the blends clearly possessed a percolation threshold decreased by 90%. The electrical conductivity of the CB-filled blends was higher than those of CB-filled pure PI. The transition temperature for PTC material was reported in the range of 180 to 210 °C. The preferential location of CB filler in PI domains could be observed using the optical microscope. In addition, the composites met the standards for the obtained mechanical and thermal properties, exhibiting the potential use as PTC materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48482.     

Facile preparation of Cu(I) impregnated MIL‐101(Cr) and its use in a mixed matrix membrane for olefin/paraffin separation

Cu(I) impregnated MIL‐100(Cr) [denoted Cu@MIL‐101(Cr)] is fabricated by a facile method and utilized in mixed matrix membranes (MMMs) for propylene/propane separation. Cu(I) is prepared from a CuCl₂ solution via mild reduction process using sodium sulfite as the reducing agent. The filler is incorporated into a polystyrene‐b‐polybutadiene‐b‐polystyrene (SBS) block copolymer matrix to form MMMs. As a result, both the permeability and selectivity of propylene/propane are improved after Cu(I) impregnation. The best performance is obtained for SBS/Cu@MIL‐101(Cr) MMM, and these values represent 17% and 54% improvements compared to those of SBS/MIL‐101(Cr) MMM, respectively. This result is attributed to the π‐complexation of the loaded Cu(I) by propylene gas, indicating that Cu@MIL‐101(Cr) with internal Cu(I) and a high pore volume acted as an effective filler to aid propylene/propane separation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46545.     

Asymmetric oxygen-functionalized carbon nanotubes dispersed in polysulfone for CO2 separation

Carbon dioxide separation from flue gases is an important challenge to be faced. Membrane processes are a promising alternative to increase technical and economical constraints once the development of materials with superior characteristics are attained. Integrally asymmetric mixed matrix membranes (MMMs) were prepared by dry/wet phase inversion process of polysulfone (PSF) containing oxygen-functionalized multiwalled carbon nanotubes (MWNT-O). Fourier transform infrared (FTIR) spectroscopy confirmed the presence of MWNT-O in MMMs. Thermal gravimetric analysis (TGA) showed that MMMs are stable up to 150°C. Photomicrographs from scanning electron microscopy (SEM) revealed that MMMs consist of an asymmetric structure with a skin layer supported on a sponge-like substructure. The pore size of the support of MMMs increased with MWNT-O content from 0.4 to 0.8 wt.% and the thickness of the dense layer decreased. However, when the content of MWNT-O increased to 1 wt.%, the pore size decreased, and the dense layer increased. Therefore, MMMs changed CO₂ separation performance. For 1 wt.% MWNT-O loading compared to the neat polymer, CO₂ permeance and CO₂/N₂ selectivity was increased from 1.5 to 2.7 GPU, and from 9.5 to 14.3, respectively.     

Characterization of a novel silicon-containing hybrid polymer by thermal curing,pyrolysis behavior,and fluorescence analysis

A novel linear silicon-containing hybrid polymer with C  C and Si H linkages, diphenyl-dihydroethynyl-silane (DPHES), had been conveniently synthesized and well characterized. The thermal curing, crosslinked structure and pyrolysis behavior were studied by DSC, Fourier transform infrared (FTIR), and Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The results suggest the crosslinked structures consist mainly of phenyl and aromatic fused rings, which are formed through cyclotrimerization, addition reaction, and hydrosilylation reaction. The thermal properties indicate that the crosslinked DPHES exhibits excellent thermal stability with the temperature at 5% weight loss are higher than 572 and 509 °C under nitrogen and air atmosphere, respectively. The fluorescence emission spectra show DPHES and its crosslinked product also have moderate fluorescence properties, emitting purple light, and visible blue light, respectively, which further verified the structure of DPHES. These results suggest that DPHES has the potential to be used as light-emitting materials with excellent thermal properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47403.     

Cassava (Manihot esculenta Crantz) stump biochar: Physical/chemical characteristics and dye affinity

Aiming investigated the pyrolysis of the agricultural waste known as cassava stump, the portion of the plant to which the tuberous roots and aerial parts of the plant are attached, this study had as objective to produce biochars from cassava stump by conducting vacuum pyrolysis at 400, 500, or 600?°C. The biochars were characterized by proximate analysis, thermogravimetric analysis, Fourier-transform infrared absorption spectroscopy, X-ray diffraction, scanning electron microscopy, and nitrogen adsorption. Adsorption affinity tests were performed with four different dyes: methylene blue, basic fuchsin, acid fuchsin, and alizarin. Biochar obtained at 500?°C, heating rate of 20?°C.min^?1, and 90?min of residence at the final temperature, had 22% higher fixed carbon content as compared to the other biochars and 3.16 times greater fixed carbon content than the original cassava stump. This biochar showed the best adsorption capacity (0.0679?mmol/g) and percentage of removal (87.6%) of methylene blue dye from aqueous solution. The material characterization reveals that biochars from Manihot esculenta Crantz stump may have potential application in carbon sequestering. Besides that, these biochars could be applied with efficiency as adsorbent of dyes.     

Binary metal oxides incorporated polyethersulfone ultrafiltration mixed matrix membranes for the pretreatment of seawater desalination

In this study, an attempt was made to pretreat seawater using polyethersulfone (PES) mixed matrix membranes (MMMs) incorporated with titania-based binary metal oxides. Two different titania-based binary metal oxides were prepared, namely titania-zirconia (TiZr) and titania-zinc oxide (TiZn). The influence of hydrophilic and negatively charged sulfonated poly(ether ether ketone) (SPEEK) polymer as additive of PES MMMs was also studied. Morphological and elemental analysis revealed that both ZrO₂ and ZnO were well dispersed in the as-prepared binary metal oxide TiZr and TiZn, respectively._. Thermogravimetry analysis indicated the good compatibility of TiZr and TiZn with the SPEEK/PES polymer. The binary metal oxide incorporated SPEEK/PES MMMs exhibited improved hydrophilic properties with a low water contact angle of 57° ± (0.6). SPEEK/PES MMMs incorporated with 0.5 wt% TiZr exhibited the highest permeability of 3.11 × 10⁻⁷ ± (0.2) m/s·kPa. Seawater pretreatment performance of membranes evaluated using natural organic matters containing high salinity feed water. TiZr and TiZn incorporated SPEEK/PES MMMs exhibited 95% rejection for humic acid. SPEEK/PES MMMs loaded with 0.5 wt% TiZr also showed the highest water flux and 87% water recovery within 90 min of seawater filtration. Both PES/SPEEK/TiZr and PES/SPEEK/TiZn MMMs exhibited superior antibacterial activity.