Membrane Properties Research Articles

Tailoring the gas transport properties of network polyimide membranes by bromination/debromination

Constructing membranes that possess both exceptional gas transport property and strong resistance to CO2-induced plasticization is a crucial need in membrane separation, yet it still stands as an ongoing challenge. In present study, we firstly added the bromine atom into the 2, 2′-bis(trifluoromethyl)benzidine (TF) to synthesis two new bromine substituted diamines, and subsequently one of the brominated diamines was employed as a comonomer alongside commercial tris(4-aminophenyl)amine (TAPA) and dianhydride 6FDA to prepare the network polyimide (PI) membrane via copolymerization. Following this, these new brominated PIs would undergo debromination process during the subsequent heating treatment. As a result, the bromination/debromination effect created new microporosity, which increased the d-spacing and BET surface area of the membrane, thereby largely enhancing the crosslinked PI membrane’s gas separation performance. Moreover, the robust network structures achieved through in-situ crosslinking way, derived from a segment of trifunctional TAPA monomers, enhance the resultant membrane's resistance to CO2 plasticization issue. An exemplified membrane referred to as 6 F-TA/TF-dBr-450 membrane displays outstanding CO2/CH4 separation capabilities, with a CO2 permeability of 1420.56 Barrer and a CO2/CH4 selectivity of 39.67, surpassing the 2008 Roberson upper bound by a considerable margin. Besides, this membrane demonstrates outstanding durability against CO2-induced plasticization, showcasing its strength under pressures of at least 35 Bar.

Mechanisms and mass transfer kinetics of Cr(VI) adsorbed by mussel shell incorporated adsorptive membrane

The presence of Cr(VI) results in pollution that threatens human health and aquatic life. Therefore, there is an urgent need for Cr(VI) to be removed from contaminated water. The mussel shell incorporated polyethersulfone (MSPES) membranes designed to form the flat sheet adsorptive membrane (FSAM) crossflow treatment systems was used to remove Cr(VI) from synthetic solution. The physicochemical properties of the MSPES membrane were verified using an atomic force microscope, scanning electron microscope, and water contact angle goniometer. The performance of MSPES2.0 to remove Cr(VI) ions ranged from 15.00 to 16.05 % was higher than that of MSPES2.2 ranged from 10.00 to 10.75 %, which observed for 1.5 h of the experiment. The MSPES2.0 adsorption capacity of 3.2 mg g−1 was higher than the MSPES2.2 adsorption capacity of 1.45 mg g−1. The applicability of Generalized Fulazzaky equations to simulate the experimental data was validated to predict the mechanisms and kinetics of Cr(VI) mass transfer by the MSPES membrane and to determine the resistance of mass transfer for adsorption of Cr(VI) depended on porous diffusion (PD) rate. The Cr(VI) adsorption controlled by PD was verified to provide an insight of how the mass transfer process contributed to advanced FSAM crossflow treatment system.

Gramicidin A as a mechanical sensor for mixed nonideal lipid membranes.

Gramicidin A (gA) is a short hydrophobic β-helical peptide that forms cation-selective channels in lipid membranes in the course of transbilayer dimerization. The length of the gA helix is smaller than the thickness of a typical lipid monolayer. Consequently, elastic deformations of the membrane arise in the configurations of gA monomers, conducting dimer, and the intermediate state of coaxial pair, where gA monomers from opposing membrane monolayers are located one on top of the other. The gA channel is characterized by the average lifetime of the conducting state. The elastic properties of the membrane influence the average lifetime, thus making gA a convenient sensor of membrane elasticity. However, the utilization of gA to investigate the elastic properties of mixed membranes comprising two or more components frequently relies on the assumption of ideality, namely that the elastic parameters of mixed-lipid bilayers depend linearly on the concentrations of the components. Here, we developed a general approach that does not rely on the aforementioned assumption. Instead, we explicitly accounted for the possibility of inhomogeneous lateral distribution of all lipid components, as well as for membrane-mediated lateral interactions of gA monomers, dimer, coaxial pair, and minor lipid components. This approach enabled us to derive unknown elastic parameters of lipid monolayer from experimentally determined lifetimes of gA channel in mixed-lipid bilayers. A general algorithm was formulated that allows the unknown elastic parameters of a lipid monolayer to be obtained using gA as a mechanical sensor.

Regulation of the Degradation Properties of Tyrosinase-Catalyzed Crosslinking Silk Membranes for Superficial Wound Repair.

Appropriate biodegradability to meet the demands of wound repair is critical for superficial wound repair membrane applications. Tyrosinase-catalyzed crosslinking SF (c-SF) membranes were constructed and regulated the degradation behavior in this study. The crosslinking degree of the c-SF membranes could be adjusted by reaction ratios of tyrosinase against SF (TYR/SF). Upon reaching a TYR/SF ratio of 20/6000, the degree of crosslinking increased to 88.17 ± 0.20%, without obvious changes in the crystal structure. The degradation behavior was regulated by the TYR/SF ratio and the degradation environment. All c-SF membranes remained stable after immersion without collagenase but showed an adjustable degradation behavior in the presence of collagenase. As the TYR/SF ratio increased, the residual weights increased from 23.31 ± 1.35% to 60.12 ± 0.82% after 7 days of degradation, occurring with low increased amounts of β-sheet structure and free amino acids. This work provides a new c-SF membrane with controllable rapid degradability and favorable cytocompatibility, which can help to meet requirements for biodegradable superficial wound repair membranes.

Effect of silane treatment on eggshell powder incorporated in poly (L-lactic acid) composite membrane

ABSTRACT The treatment of water containing oil from various industrial and environmental sources is a challenging issue. Polymeric composite membranes with reinforcing fillers have been extensively used to overcome this issue. In this study, poly(L-lactic acid) (PLLA) incorporated with eggshell powder (ESP) composite membranes were prepared to absorb oil in water. ESP has been modified into silane-treated ESP (SESP) by using the silane coupling agent, 3-(methacryloyloxy)propyl trimethoxysilane (MPTS) to enhance the compatibility of the ESP in the membrane. The concentration of MPTS solution used to treat the ESP has been varied at 1%, 3% and 5% denoted as SESP1, SESP3, and SESP5, respectively to observe the chemical and mechanical properties of the composite membrane. Composite membranes reinforced with SESP have high deformation resistance with a modulus value of 2105.45 MPa compared to 1892.77 MPa of PLLA membrane. At 5% MPTS concentration, the membrane’s water contact angle (WCA) increased to 75°. The oil absorption ability of the composite membrane filled with SESP5 increased from ~ 14% to 71%. The use of MPTS to modify the surface of the ESP has improved the compatibility between the reinforcing filler and the polymer matrix as well as with the oil absorption capability.

Tailoring polyamide membranes via dynamic interfacial manipulation with functional Fe3O4 nanoparticles for elevated Nanofiltration performance

This study investigates the enhancement of thin-film-composite polyamide (TFC-PA) membranes for nanofiltration (NF) by conducting direct interfacial polymerization (IP) at a substrate-free water/n-hexane interface. Fe3O4 nanoparticles, stabilized with surfactants sodium laurate (SL) and hexadecyltrimethylammonium bromide (CTAB), were employed to dynamically influence the diffusion of piperazine (PIP) monomers. The incorporation of these nanoparticles enabled the modulation of the IP process, yielding membranes with distinct morphologies and performance characteristics. Specifically, membranes with SL-stabilized Fe3O4 (SLF) demonstrated enhanced cross-linking and superior salt rejection capabilities for divalent cations, with MgCl2 and CaCl2 rejection rates notably increasing to 95.5 % and 93.4 % respectively. Conversely, CTAB-stabilized Fe3O4 (CTABF) membranes, characterized by smoother surfaces and a looser structure, exhibited increases in water permeance up to 140 % relative to controls, but with a significant reduction in salt rejection efficacy as nanoparticle concentration increased. This study highlights the crucial impact of surfactant-stabilized nanoparticle modifications in manipulating the IP process and tailoring the filtration properties of PA membranes, offering promising avenues for optimizing NF membrane technology.

Investigation of Permeability Against Some Metals with a Functional Thiophene Based Polymeric Membrane Sensor

AbstractThere are many advantages of using membranes in the separation of wastewater, but their uses are limited because they are not reusable due to blockages in the membrane. In this study, alginate‐based poly(ethyl‐methacrylate) (PEMA) polymeric membranes containing previously synthesized IOS, which are known to be selective against Fe3+, were prepared and their permeability against heavy metals such as Cd2+, Co2+, Cu2+, Fe3+, Hg2+ and Pb2+ were investigated. The properties of membranes characterized by UV‐Vis and FT‐IR spectrophotometry, were investigated with analysis techniques such as SEM, contact angle measurements, TG‐DTG, DSC and AFM. As a result of the measurements taken from the UV spectrophotometer of the filtrates passed through various aqueous ion solutions of the membranes as mentioned above, it was concluded that the ion to which the membrane was most selective was the Fe3+ ion. Moreover, it could be said that thanks to the repeated filtration processes the membrane prepared retained some Fe3+ ion in each measurement and could be used many times in the filtration process. Resultantly, it is possible to say that the polymeric Fe3+ membrane sensor produced may be suitable for use when it is necessary to remove Fe3+ ion from a polluted aqueous environment.

Power-to-ammonia synthesis process with membrane reactors: Techno- economic study

This work aims at investigating the potential of catalytic membrane reactors (CMRs) for ammonia production from renewable hydrogen. To achieve this objective, computer-aided process simulation is deployed using Aspen plus v14 simulation tool. A 1D model is developed to describe the integration of a ruthenium catalyst into a CMR equipped with inorganic membranes that are selective to NH3 over N2 and H2. First, the CMR performance is studied across a broad spectrum of membrane properties and operating conditions. Subsequently, the CMR model is integrated into several Power-to-Ammonia (PtA) process layouts, which are optimized and techno-economically compared against a traditional PEM-based PtA production process, employing condensation for the purification stage. Key findings at the reactor level confirmed that beyond a selectivity threshold towards hydrogen of 10–20, both the degree of conversion and recovery tend to be generally independent of the membrane's selectivity. However, for producing pure ammonia permeate, highly selective membranes (>1000 towards H2) depending on the pressure drop are found essential making this alternative elusive based on existing membranes. At the PtA level, results in terms of efficiency indicates that the use of membrane reactor increases the system efficiency by around ∼8% with respect to reference case while ∼15% enhancement is achieved with this process when using SOEC technology. When examining the final Levelized Cost of Ammonia (LCOA), incorporating a membrane reactor in conjunction with condensation separation results in a cost that nearly matches the reference case. Future research should focus on replacing the condensation process with a method of purification at lower pressures. This could potentially further improve efficiency and reduce the cost of the membrane reactor compared to the traditional one.

Revealing structure-property relationship of polyimide membrane for gas separation: Insight into monomer ratio via molecular simulation

The molecular design of polyimide (PI) offers a simple yet effective approach in improving gas separation efficiency by adjusting chain stiffness and fractional free volume (FFV). In this study, the configuration of 6FDA-DAM:DABA PI was tailored by varying the diamines ratio at 1:1, 2:3 and 3:2. Leveraging molecular dynamics simulation as a robust predictive tool, the impact of monomer ratio on the physical and gas transport characteristics of the resulting PIs was analyzed. The outcome demonstrated that the total dipole moment of polymer chains and the presence of bulky groups both affect a membrane's FFV. 6FDA-DAM:DABA (3:2) demonstrated the highest glass transition temperature (Tg) due to its highest DAM composition in the polymer backbone. Furthermore, diffusivity and solubility of the three PIs were also evaluated and compared with literature data. In overall, this study provided an alternative way of assessing the membrane properties beyond conventional experimental methods.

Permeate gap thermo-osmotic system for simultaneous freshwater production, energy storage, and power generation

The emerging thermo-osmotic system enables harvesting low-grade thermal energy below 100 °C for the simultaneous production of fresh water and electricity. Considering the fluctuation of low-grade heat sources, a novel permeate gap thermo-osmotic system without pump pressurization was proposed in this study, which also allows for energy storage. A lab-scale setup with a 32 cm2 membrane area was built, by which a 2 W light bulb was successfully illuminated through the thermal energy-potential energy-electricity conversion process. In the pressurization process of the permeate side, the hydrophobic membranes with non-woven support exhibit higher pressure resistance, capable of withstanding pressures exceeding 200 kPa. Through experimental and theoretical analyses, the influences of different operation conditions and membrane properties on system performance were studied. Furthermore, utilizing solar energy as the heat source, a case study was conducted based on real meteorological data from a typical coastal city over a consecutive 72-hour period. In the solar-driven PGTO system with a power capacity of approximately 150 kW, the exergy efficiency can achieve 1.04 %, with a power density surpassing 0.1 W m−2, and an average daily freshwater production of over 70000 t. The energy storage function enables stable power generation within the 72 h, and it can sustain steady operation for nearly 7 h thereafter in the absence of sunlight. This study demonstrated the potential of the proposed PGTO system to efficiently utilize fluctuating low-grade thermal energy.

Absence of alka(e)nes triggers profound remodeling of glycerolipid and carotenoid composition in cyanobacteria membrane

Abstract Alka(e)nes are produced by many living organisms and exhibit diverse physiological roles, reflecting a high functional versatility. Alka(e)nes serve as waterproof wax in plants, communicating pheromones for insects, and microbial signaling molecules in some bacteria. Although alka(e)nes have been found in cyanobacteria and algal chloroplasts, their importance for photosynthetic membranes has remained elusive. In this study, we investigated the consequences of the absence of alka(e)nes on membrane lipid composition and photosynthesis using the cyanobacterium Synechocystis PCC6803 as a model organism. By following the dynamics of membrane lipids and the photosynthetic performance in strains defected and altered in alka(e)ne biosynthesis, we show that drastic changes in the glycerolipid contents occur in the absence of alka(e)nes, including a decrease in the membrane carotenoid content, a decrease in some digalactosyldiacylglycerol (DGDG) species and a parallel increase in monogalactosyldiacylglycerol (MGDG) species. These changes are associated with a higher susceptibility of photosynthesis and growth to high light in alka(e)ne-deficient strains. All these phenotypes are reversed by expressing an algal photoenzyme producing alka(e)nes from fatty acids. Therefore, alkenes, despite their low abundance, are an essential component of the lipid composition of membranes. The profound remodeling of lipid composition that results from their absence suggests that they play an important role in one or more membrane properties in cyanobacteria. Moreover, the lipid compensatory mechanism observed is not sufficient to restore normal functioning of the photosynthetic membranes, particularly under high-light intensity. We conclude that alka(e)nes play a crucial role in maintaining the lipid homeostasis of thylakoid membranes, thereby contributing to the proper functioning of photosynthesis, particularly under elevated light intensities.

Breaking barriers in passive sampling: The potential of PTFE membranes in the monitoring of hydrophilic micropollutants

Passive samplers are key tools to sample hydrophilic micropollutants in water. Two main approaches address the influence of hydrodynamics: (1) determining site-specific sampling rate (RS) by characterizing kw, the mass transfer coefficient of the water-boundary layer (WBL), and (2) reducing WBL impact using a diffusive material to control the uptake. The first requires calibration data and the second has only been achieved using fragile diffusive material. This study assesses the transfer of hydrophilic contaminants through polytetrafluoroethylene (PTFE; 30 µm thick), a new membrane material with lower sorption than commonly used polyethersulfone (PES). Combined for the first time in a Chemcatcher-like configuration, we calibrated the modified samplers for 44 micropollutants to provide RS – kw relationships for in-situ RS determination (approach 1). Micropollutants accumulated over 2000 times more on the sorbent than on PTFE. PTFE-based RS (0.027 to 0.300 L day-1) were 2.5 higher than previously reported with PES. Membrane property measurements (porosity, tortuosity) indicated that accumulation is primarily controlled by the membrane. Extrapolation indicated that using thicker PTFE membranes (≥ 100 µm) would shift uptake control entirely to the membrane in river conditions (approach 2). This finding could enable RS prediction based on contaminants properties, thus representing a significant advancement in passive sampling.

Effect of membrane properties on the odor emanating from training aids for explosive-detecting canines.

Canines are widely used for real-time detection of explosives and have proven to be on par with instrumental methods. Canines are thought to rely largely upon detection of volatile chemical constituents of the explosives, though not necessarily the explosive itself. Hence, it is crucial to understand the odor available to them as generated by training aids. Previous studies have established that the Training Aid Delivery Device (TADD) developed by SciK9 is a reliable training aid that reduces cross-contamination and doubles as a storage device. A TADD comprises a standardized container, a synthetic membrane, a membrane holder, and a lid. In the work presented, activated charcoal strips were placed above and below the TADD membrane to determine the relative amounts of volatiles emitted by dynamite (i.e., ethylene glycol dinitrate (EGDN) and trinitroglycerin (NG)). The strips were eluted and the extracts tested using gas chromatography-mass spectrometry in negative ion chemical ionization mode. A series of t-tests at 95% confidence level were performed to determine any differences in vapor composition above and below the membranes. Nine synthetic membranes and six glass fiber membranes were tested in this study. It was expected that the relative concentration of volatiles would remain the same on both sides of the membrane; however, selective removal of nitroglycerin by some membranes was observed. Synthetic membranes with larger pore sizes showed no alteration in the vapor composition. Both synthetic and glass fiber membranes did not show a significant change in relative concentration of the other volatile compound in dynamite, i.e., EGDN. Out of all the membranes tested, three synthetic membranes and four glass fiber membranes showed selective alteration in odor availability of nitroglycerin in dynamite. For training purposes, membranes that do not alter the vapor composition should be used in the training aid.

Detection and intelligent optimization of blood glucose signals based on MXene-assisted sensors

Two-dimensional materials exhibit unique properties that make them ideal for electronic sensing applications, particularly in the field of biosensors. In this study, a Ti3C2Tx MXene/graphene composite was investigated for its potential use in non-invasive blood glucose detection. The strong electrostatic interaction between MXene and graphene nanosheets effectively reduces the self-stacking of both components, resulting in the formation of a porous interlayer structure with enlarged interlayer spacing. This unique structure creates an efficient nanoscale transport channel, which increases the number of active sites and shortens ion diffusion paths. Consequently, the electrochemical properties of the composite membrane are enhanced, making it a promising candidate for sensing element applications. As the human blood glucose level is primarily determined by the glucose concentration in the blood, the concentration of glucose solution serves as the foundation for noninvasive blood glucose concentration detection. In this work, a prediction model was established using the partial least squares fitting method to correlate the electrochemical fingerprinting data with the glucose aqueous solution concentration, and the reliability of the model was verified. To address the limitations of the partial least squares method, which lacks nonlinear fitting capabilities, an RBF (radial basis function) network model was employed. Finally, a genetic algorithm was utilized to perform global optimization of the training parameters of the RBF network, and the quantitative relationship between the NIR spectral data and glucose concentration was validated. The findings of this study provide a theoretical basis for the development of equipment and the improvement of measurement accuracy in the field of human noninvasive glucose detection.

Effects of polyvinylpyrrolidone additive on structures and properties of Poly(m-phenylene isophthalamide) hollow fiber membranes -experiment observation and computation approach

This study systematically investigates the effect of introduction of polyvinylpyrrolidone (PVP) used as a hydrophilic additive and its molecular weight change on the morphological, mechanical properties, and membrane performances of poly(m-phenylene isophthalamide) (PMIA) hollow fiber (HF) membranes prepared by dry-jet wet spinning method. The results of the morphological and mechanical properties clearly show an increased proportion of a sponge-like pore structure and an overall improvement in the mechanical properties of the PMIA HF membranes with higher molecular weight PVP, respectively. Interestingly, molecular dynamics simulation showed that the presence of PVP within the PMIA matrix activated the overall movement of PMIA molecules, suggesting that the overall flexibility of the system, which can potentially inhibit the collapse of relatively brittle membranes, is increased by the presence of PVP. Finally, as the molecular weight of PVP increases, a typical trade-off phenomenon is observed on PMIA HF membranes, where the water permeability decreases while the rejection rate increases. Based on these results, the findings on the influence of PVP additive and its potential as a reinforcing agent observed in this study through experimental analysis and computational approaches are expected to provide new insights into the development of high-performance polymeric HF membranes.

Highly selective polyphenylene sulfide nanocomposite membranes based on two-dimensional metal–organic frameworks for molecular separation

Two-dimensional MOF nanomaterials with planar spacing and porosity can effectively transport water molecules and have a wide range of applications in dye wastewater treatment. In this work, two types of nanosheets, Cu-TCPP and Zn(Bim)(OAc), were loaded onto polyphenylene sulfide(PPS) ultrafiltration membranes by vacuum-assisted self-assembly, and stable Cu-TCPP/Zn(Bim)(OAc) composite membranes were prepared by taking advantage of the hydrogen bonding and π-π conjugation between the two types of nanosheets. Cu-TCPP/Zn(Bim)(OAc) 2:1 composite membrane showed an optimum selectivity of 97.8% and a permeability of 14.6 L m−2 h−1 bar−1 for aqueous rhodamine B. The surface morphology, chemical environment and properties of the composite membranes were analyzed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle measurement (DSA) and zeta potential. The rejection rates of the five dyes, saffron T (ST), eriochrome black T (BT), rhodamine B (RB), crystal violet (CV)and Congo red (CR), were 95.8%, 98%, 97.8%, 97.2% and 98.8%, respectively. After immersion in 0.5 mol of different acids, the rejection rate of Congo red dye still reached 96%, composite membrane has good acid resistance. The interaction between the surface groups of the two MOF materials not only resulted in better separation effect, but also gave the composite membrane better contamination resistance and stability. This method of using two-dimensional MOF materials to construct the selective layer of composite membranes has good application prospects.

Arid1b haploinsufficiency in pyramidal neurons causes cellular and circuit changes in neocortex but is not sufficient to produce behavioral or seizure phenotypes.

Arid1b is a high confidence risk gene for autism spectrum disorder that encodes a subunit of a chromatin remodeling complex expressed in neuronal progenitors. Haploinsufficiency causes a broad range of social, behavioral, and intellectual disability phenotypes, including Coffin-Siris syndrome. Recent work using transgenic mouse models suggests pathology is due to deficits in proliferation, survival, and synaptic development of cortical neurons. However, there is conflicting evidence regarding the relative roles of excitatory projection neurons and inhibitory interneurons in generating abnormal cognitive and behavioral phenotypes. Here, we conditionally knocked out either one or both copies of Arid1b from excitatory projection neuron progenitors and systematically investigated the effects on intrinsic membrane properties, synaptic physiology, social behavior, and seizure susceptibility. We found that disrupting Arid1b expression in excitatory neurons alters their membrane properties, including hyperpolarizing action potential threshold; however, these changes depend on neuronal subtype. Using paired whole-cell recordings, we found increased synaptic connectivity rate between projection neurons. Furthermore, we found reduced strength of excitatory synapses to parvalbumin (PV)-expression inhibitory interneurons. These data suggest an increase in the ratio of excitation to inhibition. However, the strength of inhibitory synapses from PV interneurons to excitatory neurons was enhanced, which may rebalance this ratio. Indeed, Arid1b haploinsufficiency in projection neurons was insufficient to cause social deficits and seizure phenotypes observed in a preclinical germline haploinsufficient mouse model. Our data suggest that while excitatory projection neurons likely contribute to autistic phenotypes, pathology in these cells is not the primary cause.

Enhanced Lithium-Ion Transport in Lithium Metal Batteries Using ZSM-5 Nanosheets Hybridized Solid Polymer Electrolytes.

Solid polymer electrolytes (SPEs) are the key components of lithium metal batteries to overcome the obstacle of insecurity in conventional liquid electrolytes; however, the trade-off between their ionic conductivity and mechanical properties remains a significant challenge. In this work, two-dimensional ZSM-5 nanosheets as fillers are incorporated into a poly(ethylene oxide) (PEO) matrix and lithium salts to obtain composite polymer electrolytes (CPEs). The improved physicochemical and electrochemical properties of the CPE membranes are characterized in full detail. Stripping/plating measurements in symmetric Li/Li cells and cyclic charge/discharge tests are performed to investigate the cyclability and stability of the CPEs. All-solid-state LiFePO4/Li batteries deliver excellent cycling performance with an initial discharge capacity of 152.3 mAh g-1 and 91.4% capacity retention after 200 cycles at 0.2 C, with a discharge specific capacity of 118.8 mAh g-1 remaining after 350 cycles at 0.5 C. Therefore, CPEs containing ZSM-5 nanosheets are a promising option for all-solid-state lithium-ion batteries.

Enhancement of antifouling and mechanical properties of polysulfone membrane using zwitterionic biphenyl polyimide as additive

Biphenyl polyimides, which are known by its excellent heat resistance and mechanical properties, were synthesized by adjusting the molar ratio of monomers, followed by end-functionalized with zwitterionic group via reaction with 1,3-propanesultone. The zwitterionic sulfobetaine biphenyl polyimide (z-biph-PI) copolymers with different hydrophobic chain lengths were employed as the additive for the preparation of polysulfone (PSf) membrane. X-ray photoelectron spectrometry (XPS) measurement on membrane surfaces revealed that the sulfobetaine groups of z-biph-PI migrated toward water in the membrane formation process, during which a large amount of porous, narrow and densely packed pores were created as illustrated in scanning electron microscopy (SEM) images. Therefore, the incorporation of z-biph-PI simultaneously enhanced the pure water flux and protein rejection ratio of membranes, overcoming the trade-off effects between permeability and selectivity. The adsorption of bovine serum albumin decreased from ∼47.7 μg/cm2 for the pristine membrane to a minimum of ∼12.4 μg/cm2 for the blend membrane. More importantly, the tensile strength and elongation at break were also simultaneously improved due to the unique mechanical property of biph-PI and the strong π-π interaction between biphe-PI and PSf. Meanwhile, the blend membrane exhibited excellent filtration and thermal stability. All these characteristics of the blend membrane made it promising in ultrafiltration application.

Improving selectivity and antifouling properties of a PES hollow fibre membrane with a photo-enzyme for the removal of ciprofloxacin and sulfamethoxazole

ABSTRACT A multifunctional hollow fibre was prepared by the modification of polyethersulfone (PES) with laccase (Lac) and phosphorus-doped graphitic carbon nitride (P-gC3N4) for the removal of ciprofloxacin and sulfamethoxazole. The properties and structure elucidation of the prepared membranes were evaluated using contact angle analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), correlative light electron microscopy (CLEM), atomic force microscopy (AFM), tensile strength, water-intake capacity, and pure water flux. The modified multifunctional hollow fibre membranes showed increased root mean square surface roughness from 50 nm for neat PES to 104 nm, which contributed to the significantly higher water flux of 90 L.m−2h−1 compared to 54 L.m−2h−1 for pristine PES. The hydrophilicity also improved after modification as the contact angle reduced from 72° ± 1.01° to 42° ± 2.26°. The modified hollow fibre membranes showed an enhanced removal of ciprofloxacin (77%) and sulfamethoxazole (80%). Moreover, antifouling properties towards bovine serum albumin were 89% for FRR, 7% for Rr , 9% for Rir and 17% for Rt . Regeneration studies showed that the multifunctional hollow fibre membrane obtained a high removal percentage of 79% towards sulfamethoxazole after five cycles. Hence, this work proposes a new system that can be successfully utilized in the treatment of emerging pharmaceutical pollutants in water.