Pure Polysulfone Membrane Research Articles

Effect of ZIF-78 metal-organic framework crystal morphology and defect in resulting polysulfone mixed matrix membranes

BackgroundMixed matrix membranes (MMMs) provide a new possibility for membranes to exceed the tradeoff between permeability and selectivity found in pure polymeric membranes. Factors that enhance gas separation performance in MMMs include filler morphology and aspect ratio. MethodsHigh aspect ratio microporous ZIF-78, a metal-organic framework (MOF) demonstrated in literature to have one of the highest carbon dioxide uptake capacities, was successfully synthesized using a solvothermal method. These particles were incorporated into MMMs in non-defective and systematically defective forms by using two common solvents – chloroform and DMF. Detailed characterization of the various membranes was performed using BET, XRD, SEM, EDS, DSC, TGA, FTIR, and a custom-built gas permeability measurement apparatus. Significant findingsIntroduction of crystals with no apparent defect results in a more tortuous pathway for permeating gas molecules, demonstrated by nitrogen permeation results. Conversely, for carbon dioxide, strong dipole-quadrupole interaction with ZIF-78 creates excellent permeation pathways through the crystal themselves. The defective system possesses more inter-filler free volume which allow all gas components to permeate more easily, in addition to the original mechanism. The gas separation performance of the resulting MMMs in this work displayed a 140 % improvement of CO2 permeability and 129 % improvement of CO2/N2 ideal selectivity over pure polysulfone membranes. This work shows the potential of using deliberately designed fillers to increase performance via special pathways for gas molecules.

Investigation of ZIF‐8, amine‐modified ZIF‐8 and polysulfone based mixed matrix membranes for CO2/CH4 separation

AbstractMembrane separation is one of the techniques used for biogas upgradation. Mixed matrix membranes (MMMs) are currently being explored to overcome the trade‐off of selectivity‐permeability inherent in polymer membranes used for gas separation. A significant challenge associated with MMMs is the poor polymer‐metal–organic framework (MOF) filler interfacial compatibility, reducing the selectivity or permeability of gas. To address this issue, the present study focuses on the effect of the amine functionalization of ZIF‐8 to enhance the CO2 gas permeation without reducing the CO2/CH4 selectivity. MMMs were fabricated using unmodified ZIF‐8 and amine‐modified ZIF‐8 nanofillers dispersed in polysulfone at 5, 10, and 15 wt% loadings. MMMs were characterized by FTIR, DSC, TGA, and FESEM. X‐ray diffraction and FTIR analysis was conducted to verify the amine modification of ZIF‐8. Further, the performance of MMMs was tested with pure gasses (CO2 and CH4) and a model mixture of CO2 and CH4. In the mixed gas permeation test, the 10 wt% ZIF‐8 MMM exhibited the highest CO2 permeability of 25.4 Barrers, while 15 wt% NH2‐ZIF‐8 MMM exhibited the highest selectivity of 13.5. Notably, the ZIF‐8 MMMs demonstrated a 148% increase in CO2/CH4 selectivity, whereas the NH2‐ZIF‐8 MMMs exhibited a 155% increase compared to the pure polysulfone membrane.

Enhancing Polysulfone Mixed-Matrix Membranes with Amine-Functionalized Graphene Oxide for Air Dehumidification and Water Treatment.

Porous low-pressure membranes have been used as active membranes in water treatment and as support for thin-film composite membranes used in water desalination and gas separation applications. In this article, microfiltration polysulfone (PSf)mixed-matrix membranes (MMM) containing amine-functionalized graphene oxide (GO-NH2) were fabricated via a phase inversion process and characterized using XPS, SEM, AFM, DMA, XRD, and contact angle measurements. The effect of GO-NH2 concentration on membrane morphology, hydrophilicity, mechanical properties, and oil-water separation performance was analyzed. Significant enhancements in membrane hydrophilicity, porosity, mechanical properties, permeability, and selectivity were achieved at very low GO-NH2 concentrations (0.05-0.2 wt.%). In particular, the water permeability of the membrane containing 0.2 wt.% GO-NH2 was 92% higher than the pure PSf membrane, and the oil rejection reached 95.6% compared to 91.7% for the pure PSf membrane. The membrane stiffness was also increased by 98% compared to the pure PSf membrane. Importantly, the antifouling characteristics of the PSf-GO-NH2 MMMs were significantly improved. When filtering 100 ppm bovine serum albumin (BSA) solution, the PSf-GO-NH2 MMMs demonstrated a slower flux decline and an impressive flux recovery after washing. Notably, the control membrane showed a flux recovery of only 69%, while the membrane with 0.2 wt.% GO-NH2 demonstrated an exceptional flux recovery of 88%. Furthermore, the membranes exhibited enhanced humidity removal performance, with a permeance increase from 13,710 to 16,408. These results indicate that the PSf-GO-NH2 MMM is an excellent candidate for reliable oil-water separation and humidity control applications, with notable improvements in antifouling performance.

Impact of Silver-Decorated Graphene Oxide (Ag-GO) towards Improving the Characteristics of Nanohybrid Polysulfone Membranes.

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the modification of membrane characteristics, including but not limited to hydrophilicity, morphology, and selectivity. In this study, a nanohybrid polysulfone (PSf) membrane embedded with silver-graphene oxide (Ag-GO) was fabricated to overcome problems related to biofouling. The embedment of Ag-GO nanoparticles (NPs) is the aim towards producing membranes with antimicrobial properties. The fabricated membranes at different compositions of NPs (0 wt%, 0.3 wt%, 0.5 wt%, and 0.8 wt%) are denoted as M0, M1, M2, and M3, respectively. These PSf/Ag-GO membranes were characterized using FTIR, water contact angle (WCA) goniometer, FESEM, and salt rejection. The additions of GO significantly improved the hydrophilicity of PSf membranes. An additional OH peak at 3380.84 cm-1 of the nanohybrid membrane from FTIR spectra may be related to hydroxyl (-OH) groups of GO. The WCA of the fabricated membranes decreased from 69.92° to 54.71°, which confirmed the improvement in its hydrophilicity. In comparison to the pure PSf membrane, the morphology of the finger-like structure of the fabricated nanohybrid membrane slightly bent with a larger bottom part. Among the fabricated membranes, M2 achieved the highest iron (Fe) removal, up to 93%. This finding proved that the addition of 0.5 wt% Ag-GO NPs enhanced the membrane water permeability together with its performance of ionic solute removal (Fe2+) from synthetic groundwater. In conclusion, embedding a small amount of Ag-GO NPs successfully improved the hydrophilicity of PSf membranes and was able to achieve high removal of Fe at 10-100 mg L-1 towards purification of groundwater for safe drinking water.

Enhanced CO2 separation performance of polysulfone membranes via incorporation of pyrazole modified MCM-41 mesoporous silica as a nano-filler

Polymeric membranes are one of the widely used materials of choice for CO2 capture from major industrial sources. However, the current generation of polymeric materials are unable to keep up with the increasing separation needs of CO2 from the air (CO2/N2) or natural gas (CO2/CH4) on an industrial scale due to their so-called permeability-selectivity tradeoff. In an effort to improve the overall gas separation performance of polymeric membranes, mixed matrix membranes (MMMs) have been suggested as a substitute strategy. In this study, Polysulfone (PSf) based MMMs were prepared by incorporating pyrazole modified MCM-41 mesoporous silica (MP) as a nano-filler in the polymer matrix to enhance the gas separation properties of membranes. MCM-41 nano-filler was synthesized and functionalized by post-grafting technique to prepare the MMMs of three different loadings (10, 20, and 30 wt%). All the membranes were characterized for physical, chemical, and thermal analysis. The CO2 gas separation performance of membranes was assessed, and the results concluded that the MCM-41-based MMMs showed the tradeoff between permeability and selectivity in the case of ideal and mixed gases. This permeability-selectivity trade-off is solved by the MP-based MMMs due to the presence of CO2-philic functional groups present on the surface of membranes. The PSf-MP membrane with the highest nanofiller loading (30 wt%) showed 79% more permeability than the pure PSf membrane. Additionally, it showed a significant enhancement of 33% and 51% in ideal selectivity for CO2/CH4 and CO2/N2, respectively, compared to pure PSf membrane. These findings support the lack of membrane faults, the enhanced filler/polymer interface, and the remarkable nano-filler dispersion in the polymer matrix. The excellent outcomes demonstrated the potential of these membranes for more industrial gas separation applications.

Preparation and Characterization of Polyvinylalcohol/Polysulfone Composite Membranes for Enhanced CO2/N2 Separation

The unique properties of polyvinyl alcohol (PVA) and polysulfone (PSf), such as good membrane-forming ability and adjustable structure, provide a great opportunity for CO2-separation membrane development. This work focuses on the fabrication of PVA/PSf composite membranes for CO2/N2 separations. The membranes prepared by coating a 7.5 wt% PVA on top of PSf substrate showed a relatively thin selective layer of 1.7 µm with an enhanced CO2/N2 selectivity of 78, which is a ca. 200% increase compared to the pure PSf membranes. The CO2/N2 selectivity decreases at a rapid rate with the increase of feed pressure from 1.8 to 5 bar, while the CO2 permeance shows a slight reduction, which is caused by the weakening of coupling transportation between water and CO2 molecules, as well as membrane compaction at higher pressures. Increasing operating temperature from 22 °C to 50 °C leads to a slight decrease in CO2 permeance, but a significant reduction in the CO2/N2 selectivity from 78 to 27.1. Moreover, the mass transfer coefficient of gas molecules is expected to increase at a higher velocity, which leads to the increase of CO2 permeance at higher feed flow rates. It was concluded that the CO2 separation performance of the prepared membranes was significantly dependent on the membrane operating parameters, and process design and optimization are crucial to bringing CO2-separation membranes for industrial applications in post-combustion carbon capture.

Preparation and Characterization of Polysulfone Membranes Reinforced with Cellulose Nanofibers.

The mechanical properties of polymeric membranes are very important in water treatment applications. In this study, polysulfone (PSF) membranes with different loadings of cellulose nanofibers (CNFs) were prepared via the phase inversion method. CNF was characterized through transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The pore morphology, mechanical properties, membrane performance and hydrophilicity of pure PSF membranes and PSF/CNF membranes were investigated. The changes in membrane pore structure with the addition of different CNF contents were observed using SEM images. It was shown that the calculated membrane pore sizes correlate with the membrane water fluxes. The pure water flux (PWF) of fabricated membranes increased with the addition of CNFs into the PSF matrix. It was shown that the optimal CNF loading of 0.3 wt.% CNF improved both the elastic modulus and yield stress of the PSF/CNF membranes by 34% and 32%, respectively (corresponds to values of 234.5 MPa and 5.03 MPa, respectively). This result indicates a strong interfacial interaction between the PSF matrix and the reinforced nanofibers. The calculated compaction factor (CF) showed that the membrane resistance to compaction could be improved with CNF reinforcement. Compared to pure PSF membrane, the hydrophilicity was significantly enhanced with the incorporation of 0.1 wt.%, 0.2 wt.% and 0.3 wt.% CNF, as shown by the water contact angle (WCA) results. It can be concluded that CNFs are homogeneously dispersed within the PSF matrix at CNF loading less than 0.5 wt.%.

High–Selective Separation Performance of CO2 from CH4 by Interfacial Engineering of Ultra-low-dose Bimetallic Pyrazine-MOF based Mixed Matrix Membranes

The CO2 capturing is much more important not only in fuel upgrading but also for controlling global warming issues. Although much Metal-Organic Framework (MOF) based mixed matrix membranes (MMMs) exhibited great potential, the interfacial fine-tuning of inorganic MOF and organic membrane matrix was still a big obstacle. Herein, a novel bimetallic Pyrazine-functionalized MOF based polysulfone (PSf) mixed matrix membrane was prepared with adaptive interfaces via the interfacial plasticizer polyethylene glycol (PEG). The filler MOF greatly enhanced the CO2 capturing ability of pure PSf and PSf/PEG blend membranes. Structural characterizations revealed defect-free membranes. The mechanical test implied that by adding MOF in PSf, brittleness appeared and strength decreased from 2.84 to 2.26 MPa, but this strength increased up to 4.11 MPa by adding PEG. The interfacial-controlled PSf/PEG/Pyrazine-MOF membranes showed the highest CO2 permeability and solubility without loss of selectivity compared to regular MOF blended MMMs or PSf/PEG blend membranes. The permeability of CO2 significantly increased from 6.82 Barrer (for pure PSf membrane) to 17.13 Barrer (for PSf/PEG/Pyrazine-MOF membrane only adding 0.2% ultra-low-dose Pyrazine-MOF with 2% PEG). The study revealed a robust and efficient strategy to elevate gas separation performances of MMMs via the interfacial engineering.

Carbon capture via novel Cu(II)‐DDA metal–organic frameworks‐based hybrid membranes

AbstractAn important contributor to global warming is the incessant escalation in carbon dioxide gas (CO2) levels in the air, mainly attributed to combustion of fossil fuels. A promising strategy to regulate emission of greenhouse gases into open air is the implementation of carbon capture systems at existing and prospective carbon‐releasing infrastructures. Being a distinguished class of mesoporous materials, metal–organic frameworks (MOFs) have great potential to efficiently alleviate CO2 emissions into the atmosphere. Nanocrystals of a newly developed Cu(II)‐DDA MOF were incorporated into polysulfone (PSF) matrix in varying concentrations to fabricate hybrid membranes to enhance their carbon capture efficiency. The prepared mixed‐matrix membranes (MMMs) demonstrated better filler‐matrix interfacial adhesion, homogenous nanofiller dispersal, semicrystalline domains and thermally resistant structure. Gas adsorption tests conducted on both the Cu(II)‐DDA MOF nanocrystals and hybrid membranes indicated good adsorption capacity for CO2 as compared to N2. Experiments using cast MMMs revealed that doping the polymer matrix with MOF nanofillers increased the CO2 permeability and the CO2/N2 selectivity of the cast MMMs. In comparison to the pure PSF membrane, the CO2 permeability and CO2/N2 permselectivity of the composite membrane doped with 5 wt% Cu(II)‐DDA MOF nanocrystals were nearly doubled.

Improving dye removal and antifouling performance of polysulfone nanofiltration membranes by incorporation of UiO-66 metal-organic framework

In the present work, a series of polysulfone (PSf) mixed-matrix nanofiltration membranes containing highly water stable UiO-66 metal-organic framework (MOF) were prepared via a simple phase inversion technique. At first, UiO-66 particles were synthesized via a solvothermal technique, activated via two various activation methods, including Soxhlet extraction and centrifugation methods. Then their adsorption performance was investigated for adsorption of anionic methyl orange (MO)/methyl red (MR) and cationic methylene blue (MB)/malachite green (MG) dyes from water. The activated UiO-66 particles via the Soxhlet extraction method (named S-UiO-66) showed better performance for dye adsorption with an equilibrium adsorption capacity of 15.64, 48.06, 85.48, and 93.51 mg/g for MG, MB, MO, and MR dyes, respectively. Then, the S-UiO-66 particles were incorporated into the PSf matrix in different percentages (up to 12 wt%) to prepare MMMs for dye removal from water. Separation performances of the prepared MMMs were evaluated by pure water flux, organic dye rejection, flux recovery ratio (FRR), and antifouling properties. As a result, the fabricated MMMs showed good hydrophilicity and excellent dye rejection performance. Remarkably, the pure water flux of MMM-12 with 12 wt% S-UiO-66 loading exhibited an increase of 21,495% compared to the pure PSf membrane. Additionally, the prepared MMMs showed good dye rejection and improved antifouling ability, which is attractive for large-scale industrial wastewater treatment applications.

Synthesis and application of ZIF-67 on the performance of polysulfone blend membranes

Sodium nitrate and sodium sulfate are used to study the effect of ZIF-67 on the performance of polysulfone membranes. Zeolitic imidazolate frameworks (ZIFs) have a high surface area, thermally and chemically stable than any other metal–organic frameworks (MOFs) due to the presence of transition metals like cobalt. In this study, the concentration of ZIF-67 was varied from 0, 1, 3, 5 to 7 wt% in polysulfone membranes. It was observed that pure water flux was enhanced from 2.94 L/m2 h (using a pure polysulfone membrane) to 35.39 L/m2h for the membrane with 7 wt% ZIF-67 at 10 kgf/cm2. Also, at a high concentration of ZIF-67 in the membrane, due to aggregation of MOFs, rejection of salts and permeate collected slightly decreased. Hence, 5 wt% ZIF-67 is used as the optimum concentration for better performance in polysulfone membranes.

Investigating the role of copper and zinc oxide nanomaterials in abatement of biofouling of ultrafiltration membrane in dynamic conditions

AbstractIn the present work, we demonstrate the synthesis, characterization, and biofouling study of polysulfone‐based mixed matrix membranes prepared with hydrophilic CuO and ZnO nanomaterial as antibacterial agents. Permeate flux was increased to 462.2 LMH for PSf/CuO (0.1%) and 472.5 LMH for PSf/ZnO (1.0%) from 191.2 LMH for pure PSf and BSA rejections were enhanced (from 70.91% to 95.73% for PSf/CuO (0.1%), from 70.91% to 93.47% for PSf/ZnO (1.0%). Biofilm growth over the modified membrane (was very less significant as correlated by lower pressure drop compared to pure polysulfone membrane in membrane fouling simulator (MFS) for 48 h. Adhesions of the Escherichia coli bacteria over the membrane surface were analyzed through an alcian blue test followed by a scanning electron micrograph. It was seen that the modified membrane showed a significant anti‐biofouling property with less adherence of alcian blue dye on the membrane surface and scanning electron micrographs demonstrated significantly lower biofouling. Mechanical strength of modified membrane increased up to 62.55 MPa for PSf/CuO (2%) and 55.41 MPa for PSf/ZnO (2%) as compared to 16.41 MPa of PSf membrane.

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.

Mixed Dimensional Nanostructure (UiO-66-Decorated MWCNT) as a Nanofiller in Mixed-Matrix Membranes for Enhanced CO2 /CH4 Separation.

Mixed-matrix membranes (MMMs) with combination of two distinct dimensional nanofillers (such as 1D-3D, 2D-3D, or 3D-3D, etc.) have drawn special attention for gas separation applications due to their concerted effects on gas permeation and mechanical properties. An amine-functionalized 1D multiwalled carbon nanotube (NH2 -MWCNT) with exceptional mechanical strength and rapid gas transport was crosslinked with an amine-functionalized 3D metal-organic framework (UiO-66-NH2 ) with high CO2 affinity in a Schiff base reaction. The resultant crosslinked mixed-dimensional nanostructure was used as a nanofiller in a polysulfone (PSf) polymer matrix to explore the underlying synergy between 1D and 3D nanostructures on the gas separation performance of MMMs. Cross-sectional scanning electron microscopy and mapping revealed the homogenous dispersion of UiO-66@MWCNT in the polymer matrix. The MMM containing 5.0 wt. % UiO-66@MWCNT demonstrated a superior permeability 8.3 Barrer as compared to the 4.2 Barrer of pure PSf membrane for CO2 . Moreover, the selectivity (CO2 /CH4 ) of this MMM was enhanced to 39.5 from the 28.0 observed for pure PSf under similar conditions of pressure and temperature.

Synthesis and Evaluation of HSOD/PSF and SSOD/PSF Membranes for Removal of Phenol from Industrial Wastewater.

Phenol is regarded as a major pollutant, as the toxicity levels are in the range of 9–25 mg/L for aquatic life and humans. This study embedded silica sodalite (SSOD) and hydroxy sodalite (HSOD) nanoparticles into polysulfone (PSF) for enhancement of its physicochemical properties for treatment of phenol-containing wastewater. The pure polysulfone membranes and sodalite-infused membranes were synthesized via phase inversion. To check the surface morphology, surface hydrophilicity, surface functionality, surface roughness and measure the mechanical properties of the membranes, characterization techniques such as Scanning Electron Microscope (SEM), contact angle measurements, Fourier Transform Infrared, Atomic Force Microscopy (AFM) nanotensile tests were used, respectively. The morphology of the composite membranes showed incorporation of the sodalite crystals decreased the membrane porosity. The results obtained showed the highest contact angle of 83.81° for pure PSF as compared to that of the composite membranes. The composite membranes with 10 wt.% HSOD/PSF and 10 wt.% SSOD/PSF showed mechanical enhancement as indicated by a 20.96% and 19.69% increase in ultimate tensile strength, respectively compared to pure PSF. The performance evaluation of the membranes was done using a dead-end filtration cell at varied feed pressure. Synthetic phenol-containing wastewater was prepared by dissolving one gram of phenol crystals in 1 L of deionized water and used in this study. Results showed higher flux for sodalite infused membranes than pure PSF for both pure and phenol-containing water. However, pure PSF showed the highest phenol rejection of 93.55% as compared to 63.65% and 64.75% achieved by 10 wt.% HSOD/PSF and 10 wt.% SSOD/PSF, respectively. The two sodalite infused membranes have shown enhanced mechanical properties and permeability during treatment of phenol in synthetic wastewater.

Coupling of Immobilized Photosynthetic Bacteria with a Graphene Oxides/PSF Composite Membrane for Textile Wastewater Treatment: Biodegradation Performance and Membrane Anti-Fouling Behavior.

The membrane bioreactor (MBR), as one of the promising technologies, has been widely applied for treatments of wastewater. However, serious membrane fouling and low microbial activity have been reported as major problems hindering the development of the MBR. To overcome these drawbacks, we intend to improve the MBR process in the view of membrane surface modification and efficient granular bacteria cultivation. In the present study, immobilized photosynthetic bacteria integration with graphene oxide (GO)/polysulfone (PSF) composite membrane separation (IPMBR) was first applied for textile wastewater treatment. Due to the high activity of immobilized cells, the IPMBR system exhibited higher efficiency on the removal of color, ammonia–nitrogen, and chemical oxygen demand than the conventional MBR system. In comparison with a pure PSF membrane, GO/PSF composite membrane presented the higher hydrophilicity (water contact angles of 62.9°) and more attractive permeability (178.5 L/m2h) by reducing the adhesion of hydrophobic foulants. During the whole operation, the immobilized photobioreactor exhibited approximately seven times higher membrane permeability that that of the conventional MBR. Meanwhile, the effect of the structure and character of immobilized photosynthetic bacteria on the membrane fouling reduction was investigated in detail. The change of extracellular polymeric substance concentration, settleability and particle size of flocs was very beneficial to alleviate membrane fouling. As a result, this research will open a new avenue for developing efficient and anti-fouling MBR technology in the future.

Enhanced Gas Separation Prowess Using Functionalized Lignin-Free Lignocellulosic Biomass/Polysulfone Composite Membranes.

Delignified lignocellulosic biomass was functionalized with amine groups. Then, the pretreated lignin-free date pits cellulose and the amine-functionalized-date pits cellulose (0–5 wt%) were incorporated into a polysulfone polymer matrix to fabricate composite membranes. The amine groups give additional hydrogen bonding to those existing from the hydroxyl groups in the date pits cellulose. The approach gives an efficient avenue to enhance the CO2 molecules’ transport pathways through the membrane matrix. The interactions between phases were investigated via Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), whereas pure gases (CO2 and N2) were used to evaluate the gas separation performances. Additionally, the thermal and mechanical properties of the fabricated composites were tested. The pure polysulfone membrane achieved an optimum separation performance at 4 Bar. The optimum separation performance for the composite membranes is achieved at 2 wt%. About 32% and 33% increments of the ideal CO2/N2 selectivity is achieved for the lignin-free date pits cellulose composite membrane and the amine-functionalized-date pits cellulose composite membrane, respectively.

Preparation of a novel polysulfone membrane by incorporated with carbon dots grafted silica from rice husk for dye removal

This study demonstrated the modification of polysulfone (PSf) membrane by incorporating carbon dots (CDs) and silica (SiO2) as additives for membrane’s permeability and dye rejection enhancement. Both the CDs and SiO2 were synthesized from rice husk and the carbon dots were impregnated on SiO2 to form CD/SiO2 composite through a hydrothermal synthesis reaction. The impregnation of CDs had shown increment of hydrophilic functional groups with negative surface charge on the SiO2. A series of CD/SiO2 composite embedded ultrafiltration (UF) membranes was developed. Results revealed that the CD/SiO2 additive was endowed with enhanced membrane properties in terms of pore size, pore distribution, hydrophilicity and negative surface charge. All the modified membranes demonstrated higher permeability and dye rejection. Among the membranes, 1.0 wt% of CD/SiO2 loading showed excellent pure water permeability increment of 111 % due to improved membrane hydrophilicity and enlargement of membrane pores. Notably, the 2.5 wt% of CD/SiO2 membrane showed the highest dye removal of 50.54 % compared to pure PSf membrane of 14.52 % albeit it had similar permeability as the pure PSf membrane. This study had demonstrated a circular economy approach in turning rice husk biomass into useful additives for membrane nanotechnology application.

The effect of Cu-BTC metal–organic framework (MOF) in mixed matrix membranes on permeability and separation of carbon dioxide and methane

This research was conducted aimed to investigate the performance of mixed matrix membranes including polysulfone (PSF) and poly (ether sulfone) (PES) as polymers and cooper (II)-benzene-1, 3, 5-tricarboxylate (Cu-BTC) as filler with different blend ratios. The response surface methodology (RSM) was employed to design the experiments. The permeation of CO2 and CH4 gases was measured at a feed pressure of 3–9 bar. Morphology, thermal stability, spectral properties and mechanical properties of the membranes were evaluated by SEM, TGA, FTIR, XRD and tensile tests, respectively. According to the results, an increase in the pressure led to a gradual fall in the permeability of CO2 and CH4. Thermal and mechanical stability of the membranes increased by the addition of nanoparticles and polymers to the pure PSF and PES membranes, molecular interaction between the two polymers and MOF was observed by FTIR analysis. The morphology of the membranes was homogenous and good disperse of MOF in matrix polymer. Gas permeability studies indicated that the permeation and ideal selectivity were improved by 100% and 34% with the addition of the Cu-BTC (20%) and PES (73%) in the PSF matrix. It was concluded that synthesized PSF/PES/CUBTC mixed matrix membranes provided an optimized performance with a good combination of permeability, selectivity.

Assessment of sulfonated homo and co-polyimides incorporated polysulfone ultrafiltration blend membranes for effective removal of heavy metals and proteins

Sulfonated homo and co- polyimide (sPI) were synthesized with new compositional ratios, and used as additives (0.5 wt%, 0.75 wt%, and 1.0 wt%) to prepare blend membranes with polysulfone (PSf). Flat sheet membranes for ultrafiltration (UF) were casted using the phase inversion technique. Surface morphology of the prepared UF membranes were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Surface charge of the membranes were determined by zeta potential, and hydrophilicity was studied by contact angle measurement. The contact angle of the membrane decreased with increasing sPI additive indicates increasing the hydrophilicity of the blend membranes. Filtration studies were conducted for rejection of heavy metals (Pb2+ and Cd2+) and proteins (pepsin and BSA). Blend membranes showed better rejection than pure PSf membrane. Among the blend membranes it was observed that with increasing amount of sPIs enhance the membrane properties and finally, PSf-sPI5 membrane with 1 wt% of sPI5 showed the improved permeability (72.1 L m−2 h−1 bar−1), and the best rejection properties were found for both metal ions (≈98% of Pb2+; ≈92% of Cd2+) and proteins (>98% of BSA; > 86% of Pepsin). Over all, this membrane was having better hydrophilicity, porosity and higher number of sites to attach the metal ions. Its performance was even better than several-reported sulfonic acid based UF membranes. All these intriguing properties directed this new UF membrane for its potential application in wastewater treatment.