Fabrication Of Polymeric Membranes Research Articles

Supramolecular Interfacial Assembly: Integrating Supramolecular Hosts into Polymeric Membranes through an Aqueous Interface

Efficient incorporation of supramolecular hosts in polymeric membranes can impart the overall matrix with new properties for a range of cutting‐edge applications. Here, we introduce a Supramolecular Interfacial Assembly (SIA) method for the fabrication of polymeric membranes featuring embedded macrocycles. Through harnessing the quasi‐liquid nature of the concentrated polymer solution, SIA orchestrates the homogenous spreading of macrocycles in an aqueous layer on its surface, leading to the creation of an interface between “water/water” phases, subsequently forming a cross‐linked membrane driven by supramolecular electrostatic interactions. Remarkably, compared to the traditional interfacial polymerization, SIA adheres to a “green” paradigm without the need for organic solvents. The resultant composite membrane exhibits superior performance in organic solvent nanofiltration (OSN), owing to the precise molecular sieving property provided by the macrocycles with well‐defined permanent cavities. This fabrication method holds great promise for the innovative design of composite membranes, which can greatly impact the production of smart membrane materials for advanced technology applications in the future.

Supramolecular Interfacial Assembly: Integrating Supramolecular Hosts into Polymeric Membranes through an Aqueous Interface.

Efficient incorporation of supramolecular hosts in polymeric membranes can impart the overall matrix with new properties for a range of cutting-edge applications. Here, we introduce a Supramolecular Interfacial Assembly (SIA) method for the fabrication of polymeric membranes featuring embedded macrocycles. Through harnessing the quasi-liquid nature of the concentrated polymer solution, SIA orchestrates the homogenous spreading of macrocycles in an aqueous layer on its surface, leading to the creation of an interface between "water/water" phases, subsequently forming a cross-linked membrane driven by supramolecular electrostatic interactions. Remarkably, compared to the traditional interfacial polymerization, SIA adheres to a "green" paradigm without the need for organic solvents. The resultant composite membrane exhibits superior performance in organic solvent nanofiltration (OSN), owing to the precise molecular sieving property provided by the macrocycles with well-defined permanent cavities. This fabrication method holds great promise for the innovative design of composite membranes, which can greatly impact the production of smart membrane materials for advanced technology applications in the future.

Can plant extracts be directly used in the fabrication of polymeric membranes for enhanced performance? A study on ultrafiltration membranes with Lycopodium

In this study, flat sheet PVDF membranes containing Lycopodium extracted with acetone and NMP were fabricated using the phase inversion method. When acetone was used as a solvent, PWF and reversible fouling rates were decreased. On the other hand, the PWF of NMP membranes fabricated with 0 %L, 1 %L, 2.5 %L, and 5 %L concentrations were found to be 198, 189, 167, and 148 L/m2.h, respectively. Although a decrease in fluxes was observed, an increase in FRR and reversible fouling rates was observed. Moreover, according to CLSM results, the live/dead cell ratio in the 5 %L-NMP membrane decreased from 16.7 to 0.7. Membranes with improved antifouling and antimicrobial properties were obtained by direct Lycopodium extraction in NMP. It is believed that these environmentally friendly membranes, produced through a more sustainable method, will perform well, especially in MBR applications.

Himalayan essential oils: Future novel green solvent in polymer nano-processing

Conventional toxic organic solvents used for the fabrication of polymeric membranes are harmful to the environment and human health. Herein, we have investigated Himalayan essential oils (EOs) as green solvents for some polymers. Hit and trial method is used to introduce suitable EOs solvent for the desired polymer to develop thin films and nano/microfibrous membranes. Solvent casting and electrospinning methods are employed to develop polycaprolactone (PCL) thin films and electrospun fibrous membranes, respectively. The physicochemical properties of as-fabricated membranes were investigated using FESEM, TGA, and FTIR spectroscopy. Nano/microfibrous electrospun membranes are successfully developed from PCL using cinnamon oil as a solvent. The antibacterial activity and biocompatibility evaluation revealed that as-fabricated PCL membranes would have high potential in tissue engineering. These findings provide a new platform in the green electrospinning process for the fabrication of nano/microfibrous membranes from a variety of polymers.

Poloxamer 407 Combined with Polyvinylpyrrolidone To Prepare a High-Performance Poly(ether sulfone) Ultrafiltration Membrane.

At present, the design and fabrication of polymer membranes with high permeability and good retention ability are still huge challenges. In this study, the commercial Poloxamer 407 (Pluronic F127) is selected as a multifunctional additive, and polyvinylpyrrolidone is used as a pore-forming agent to modify the poly(ether sulfone) membrane by liquid-liquid phase conversion technology to prepare an ultrafiltration membrane with excellent performance. The hydrophobic poly(propylene oxide) segment in Poloxamer 407 guarantees that this copolymer can be firmly anchored to the poly(ether sulfone) matrix, and the hydrophilic poly(ethylene oxide) segments in Poloxamer 407 impart a stronger hydrophilic nature to the modified membrane surface. Therefore, the permeability and hydrophilicity of the modified membrane are significantly improved and the modified membrane also has good stability. When the amount of Poloxamer 407 added to the casting solution reached 0.6 g, the water flux of the modified membrane was as high as 368 L m-2 h-1, and the rejection rate of bovine serum albumin was close to 98%. In the test to isolate organic small molecule dyes, the retention rate of the modified membrane to Congo red is 94.27%. In addition, the modified membrane shows an excellent water flux recovery rate and antifouling ability. It performs well in subsequent cycle tests and long-term membrane life tests and can be used repeatedly. Our work has resulted in poly(ether sulfone) membranes with good performance, which show great potential in the treatment of biomedical wastewater and the removal of industrial organic dye wastewater, it provides ideas for the development and application of amphiphilic polymer materials.

Various waste polystyrene for useful membrane fabrication: Comparative experimental study

Plastic waste recycling is drawing great attention to prevent the harmful effects resulting from the accumulation of plastic waste, especially as an integrated waste-to-product process. This study introduced a comparative study of two polystyrene (PS) wastes for polymeric membrane fabrication. Two types of polystyrene wastes, transparent and white-coloured, used for yoghurt packaging, were utilized. The commercial PS membrane was also fabricated for comparison. Polystyrene membranes were prepared by a non-solvent induced phase separation (NIPS) method. The prepared membranes were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), measurements of contact angle (CA), porosity, and pore size distribution. According to the results, the prepared membranes showed an asymmetric structure with a blocked skin layer. Also, the prepared membrane surfaces were partially hydrophilic. Increasing polymer concentration (from 10 to 18 wt.%) enhanced the structural homogeneity of the membrane by obtaining smaller pores. On the other hand, the membranes' porosity decreased with the rise in the polymer concentration. Measurements highlighted the successful fabrication of similar membrane characteristics using two types of PS wastes, making them vivid candidates for water desalination and gas separation applications.

Spray coating polymer substrates from a green solvent to enhance desalination performances of thin film composites

Spray coating creates highly porous polymer films that enhance pure water permeance by 7-fold, overcoming the trade-off between poor desalination performances and the sustainability offered by using green solvents in polymer membrane fabrication.

Dibasic esters as green solvents for PVDF membrane preparation

Dibasic ester solvents are introduced for PVDF membrane fabrication. These solvents are non-hazardous, biodegradable, cheap, and widely available.

Fabrication of Thin Film Composite Membranes on Nanozeolite Modified Support Layer for Tailored Nanofiltration Performance.

Thin-film composite (TFC) structure has been widely employed in polymeric membrane fabrication to achieve superior performance for desalination and water treatment. In particular, TFC membranes with a thin active polyamide (PA) selective layer are proven to offer improved permeability without compromising salt rejection. Several modifications to TFCs have been proposed over the years to enhance their performance by altering the selective, intermediate, or support layer. This study proposes the modification of the membrane support using nanozeolites prepared by a unique ball milling technique for tailoring the nanofiltration performance. TFC membranes were fabricated by the interfacial polymerization of Piperazine (PIP) and 1,3,5-Benzenetricarbonyl trichloride (TMC) on Polysulfone (PSf) supports modified with nanozeolites. The nanozeolite concentration in the casting solution varied from 0 to 0.2%. Supports prepared with different nanozeolite concentrations resulted in varied hydrophilicity, porosity, and permeability. Results showed that optimum membrane performance was obtained for supports modified with 0.1% nanozeolites where pure water permeance of 17.1 ± 2.1 Lm−2 h−1 bar−1 was observed with a salt rejection of 11.47%, 33.84%, 94%, and 95.1% for NaCl, MgCl2, MgSO4, and Na2SO4 respectively.

Fabrication and evaporation time investigation of water treatment membranes using green solvents and recycled polyethylene terephthalate

AbstractMany materials traditionally used for polymeric membrane fabrication incur significant environmental impacts and limit sustainability of the process; therefore, more eco‐friendly materials are needed in membrane fabrication. In this study, recycled polyethylene terephthalate (rPET) and a solvent blend of Rhodiasolv® PolarClean (PolarClean) and gamma‐valerolactone (GVL) were used as eco‐friendly materials to fabricate polysulfone (PSf) ultrafiltration membranes. The calculated Hansen solubility parameter affinity and relative energy difference values for PET and PolarClean‐GVL of 6.94 and 0.86, respectively, indicate favorable dissolution to create the preceding dope solution. At a baseline evaporation time of 30 s, the resulting rPET‐PSf/PolarClean‐GVL membranes outperformed the filtration capabilities of PSf/NMP membranes with 3.5% higher permeability (23.4 LMH/bar) and 53.2% greater rejection (84.9%) of bovine serum albumin (BSA). Increasing the evaporation time to 60 s resulted in a 32.4 LMH/bar decrease in permeability and 0.8% increase in BSA rejection, whereas decreasing the evaporation time to 0 s generally led to a 235.8 LMH/bar increase in permeability and 4% increase in BSA rejection. The findings indicate the potential for eco‐friendly materials to serve as alternatives for traditional materials in polymeric membranes.

A review on fabrication, characterization of membrane and the influence of various parameters on contaminant separation process

In most developing countries, the availability of drinking water is a major problem. This creates the need for treatment of wastewater, reusability of water, etc. The membrane technology has its place in the market for treating such water. This review compares polymeric membrane fabrication techniques, characteristics, and factors responsible for effective membrane separation for different materials. Although extensive knowledge is available on membrane fabrication, fabricating a membrane is still more challenging, which is more prone to antifouling properties. The competency in different fabrication methods like phase inversion, interfacial polymerization, stretching, track etching and electrospinning are elucidated in the current study. Further, the challenges and adaptability of different application fabrication methods are studied. Important surface parameters like surface wettability, roughness, surface tension, pore size, surface charge, surface functional group and pure water flux are analyzed for different polymeric membranes. In addition, the properties responsible for fouling the membrane are also covered in detail. Flow direction and velocity are the main factors that characterize a membrane's antifouling nature. Antifouling separation can still be achieved by characterizing feed properties such as pH, temperature, diffusivity, ion concentration, and surface content. Understanding fouling properties is a key to progress in membrane technology to develop an effective membrane separation.

Waste Reutilization in Polymeric Membrane Fabrication: A New Direction in Membranes for Separation.

In parallel to the rapid growth in economic and social activities, there has been an undesirable increase in environmental degradation due to the massively produced and disposed waste. The need to manage waste in a more innovative manner has become an urgent matter. In response to the call for circular economy, some solid wastes can offer plenty of opportunities to be reutilized as raw materials for the fabrication of functional, high-value products. In the context of solid waste-derived polymeric membrane development, this strategy can pave a way to reduce the consumption of conventional feedstock for the production of synthetic polymers and simultaneously to dampen the negative environmental impacts resulting from the improper management of these solid wastes. The review aims to offer a platform for overviewing the potentials of reutilizing solid waste in liquid separation membrane fabrication by covering the important aspects, including waste pretreatment and raw material extraction, membrane fabrication and characterizations, as well as the separation performance evaluation of the resultant membranes. Three major types of waste-derived polymeric raw materials, namely keratin, cellulose, and plastics, are discussed based on the waste origins, limitations in the waste processing, and their conversion into polymeric membranes. With the promising material properties and viability of processing facilities, recycling and reutilization of waste resources for membrane fabrication are deemed to be a promising strategy that can bring about huge benefits in multiple ways, especially to make a step closer to sustainable and green membrane production.

Thermodynamic Modeling and Validation of the Temperature Influence in Ternary Phase Polymer Systems.

The effect of the temperature, as a process variable in the fabrication of polymeric membranes by the non-solvent induced phase separation (NIPS) technique, has been scarcely studied. In the present work, we studied the influence of temperature, working at 293, 313 and 333 K, on the experimental binodal curves of four ternary systems composed of PVDF and PES as the polymers, DMAc and NMP as the solvents and water as the non-solvent. The increase of the temperature caused an increase on the solubility gap of the ternary system, as expected. The shift of the binodal curve with the temperature was more evident in PVDF systems than in PES systems indicating the influence of the rubbery or glassy state of the polymer on the thermodynamics of phase separation. As a novelty, the present work has introduced the temperature influence on the Flory–Huggins model to fit the experimental cloud points. Binary interaction parameters were calculated as a function of the temperature: (i) non-solvent/solvent (g12) expressions with UNIFAC-Dortmund methodology and (ii) non-solvent/polymer (χ13) and solvent/polymer (χ23) using Hansen solubility parameters. Additionally, the effect of the ternary interaction term was not negligible in the model. Estimated ternary interaction parameters (χ123) presented a linear relation with temperature and negative values, indicating that the solubility of the polymers in mixtures of solvent/non-solvent was higher than expected for single binary interaction. Finally, PES ternary systems exhibited higher influence of the ternary interaction parameter than PVDF systems.

Fabrication and characterization of polysulfone and polyethersulfone membranes applied in the treatment of fish skin tanning effluent

The tanning industries are responsible for generating high amounts of contaminated effluent and membrane separation processes can be used to treat this type of wastewater. This paper aimed at the fabrication of polymeric membranes from the phase inversion technique and its application in the treatment of fish skin dye tanning effluent. The membranes were characterized with thermal analysis, scanning electron microscopy, contact angle, water absorption, porosity, average size pore and permeation with distilled water in the range of 1–4 bar. The antifouling properties of the membranes were evaluated after filtration of solution of bovine albumin (BSA) (Cycle 1) and the tannery effluent (Cycle 2). The characterization showed that the prepared membranes are anisotropic with porous sub-layer, thermally resistant up until 300 °C and hydrophilic. The membranes with the highest percentage of polyethersulfone (PES) in the composition showed greater hydrophilicity and porosity. Regardless of the polymeric composition, all membranes showed 80% BSA rejection. The membrane with 16.4 wt%PES, 5.0 wt%PSU and 3.0 wt%NaCl showed the best results, reducing 88% of the chemical oxygen demand and 92% of the absorbance of fish skin tanning effluent. Regardless of composition and hydrophilicity, all membranes had their flux recovery higher than 95% after permeation of BSA and effluent. The results obtained with fabrication membranes from polymer blends showed themselves to be promising for treatment of fish skin dye effluent.

Stromal cell-derived factor loaded co-electrospun hydrophilic/hydrophobic bicomponent membranes for wound protection and healing.

Chronic wounds are one of the key concerns for people with diabetes, frequently leading to infections and non-healing ulcers, and finally resulting in the amputation of limbs/organs. Stromal cell-derived factor 1 (SDF1) is a major chemokine that plays a significant role in tissue repair, vascularization, and wound healing. However, the long-term sustained delivery of SDF1 in a chronic wound environment is a great challenge. In order to facilitate the sustained release of SDF1 in diabetic wounds, it could be incorporated into wound-healing patches. Herein, we report the fabrication of a hydrophilic/hydrophobic bicomponent fiber-based membrane, where SDF1 was encapsulated inside hydrophilic fibers, and its applicability in wound healing. A co-electrospinning technique was employed for the fabrication of polymeric membranes where PVA and PCL form the hydrophilic and hydrophobic components, respectively. Morphological analysis of the developed membranes was conducted via scanning electron microscopy (SEM). The mechanical strength of the membranes was investigated via uniaxial tensile testing. The water uptake capacity of the membranes was also determined to understand the hydrophilicity and exudate uptake capacity of the membranes. To understand the proliferation, viability, and migration of skin-specific cells in the presence of SDF1-loaded membranes, in vitro cell culture experiments were carried out using fibroblasts, keratinocytes, and endothelial cells. The results showed the excellent porous morphology of the developed membranes with distinguishable differences in fiber diameters for the PVA and PCL fibers. The developed membranes possessed enough mechanical strength for use as wound-healing membranes. The co-electrospun membranes showed good exudate uptake capacity. The controlled and extended delivery of SDF1 from the developed membranes was observed over a prolonged period. The SDF1-loaded membranes showed enhanced cell proliferation, cell viability, and cell migration. These biocompatible and biodegradable SDF1-loaded bicomponent membranes with excellent exudate uptake capacity, and cell proliferation and cell migration properties can be exploited as a novel wound-dressing membrane aimed at chronic diabetic wounds.

On the organic solvent free preparation of ultrafiltration and nanofiltration membranes using polyelectrolyte complexation in an all aqueous phase inversion process

Sustainable polymeric membrane fabrication aims for processes without the use of hazardous organic solvents or crosslinkers. One promising alternative method represents the fabrication of polyelectrolyte complex (PEC) membranes based on aqueous phase separation. We present the fabrication of PEC membranes from salt dilution induced phase separation. The complexation of the polyanion PSS and polycation PDADMAC is suppressed by an overcritical KBr concentration. The overcritical liquid polymer solution is cast and subsequently immersed in deionized water. The concentration gradient leads to salt diffusion out of, and water into the liquid polymer solution until the composition enters the demixing gap. Further salt dilution induces polyelectrolyte precipitation in the two phase region and forms the final porous PEC membrane. The presented approach shows similarities to the established non-solvent induced phase separation (NIPS), so high potential for the transfer of existing expertise. Most notably, the influence of simultaneous demixing of polyions is observed for different polyanion/polycation ratios in the liquid polymer solution. Three monomer ratios lead to membranes with different morphologies and separation properties in the range of ultrafiltration and nanofiltration. The presented method can be applied with commercially available polyelectrolytes and is easy to implement. This method is a promising approach to eliminating the use of organic solvents and realizing a sustainable alternative to the state of the art polymeric membrane fabrication processes.

Cellulose Acetate Polymeric Membrane Fabrication by Nonsolvent-Induced Phase Separation Process: Determination of Velocities of Individual Components

Abstract In this work, the velocities of individual components during the immersion process using mathematical modeling of a nonsolvent-induced phase separation process are investigated. For this purpose, a mass average velocity correction factor was defined as the ratio of mass average velocity in the absence of a zero polymer velocity assumption to the mass average velocity with zero polymer velocity assumption. The velocities were computed and the result was coherent with observations of a considered case study. It was concluded that the polymer moves towards the interface, as the sign of the polymer velocity at early moments of immersion was positive, which is in accord with accumulation and vitrification of the polymer at the interface. The positive sign of the solvent and the negative sign of nonsolvent are in accord with the observations as solvent leaves the cast film and nonsolvent penetrates into the film. The reduction of velocity values to the order of magnitude of diffusivities is in accord with the limiting role of the rigid skin layer for mass exchanges. Relatively large velocity values of the solvent rather than the nonsolvent imply that much more solvent is probably left in the cast film rather than the nonsolvent enters into it as observed by densification of the cast film.

Construction of a thermoresponsive magnetic porous polymer membrane enzyme reactor for glutaminase kinetics study.

Fabrication of polymer membranes with nanopores and a confinement effect toward enzyme immobilization has been an enabling endeavor. In the work reported here, an enzyme reactor based on a thermoresponsive magnetic porous block copolymer membrane was designed and constructed. Reversible addition-fragmentation chain transfer polymerization was used to synthesize the block copolymer, poly(maleic anhydride-styrene-N-isopropylacrylamide), with poly(N-isopropylacrylamide) as the thermoresponsive moiety. The self-assembly property of the block copolymer was used for preparation of magnetic porous thin film matrices with iron oxide nanoparticles. By covalent bonding of glutaminase onto the surface of the membrane matrices and changing the temperature to tune the nanopore size, we observed enhanced enzymolysis efficiency due to the confinement effect. The apparent Michaelis-Menten constant and the maximum rate of the enzyme reactor were determined (Km = 32.3 mM, Vmax = 33.3 mM min-1) by a chiral ligand exchange capillary electrochromatography protocol with L-glutamine as the substrate. Compared with free glutaminase in solution, the proposed enzyme reactor exhibits higher enzymolysis efficiency, greater stability, and greater reusability. Furthermore, the enzyme reactor was applied for a glutaminase kinetics study. The tailored pore sizes and the thermoresponsive property of the block copolymer result in the designed porous membrane based enzyme reactor having great potential for high enzymolysis performance. Graphical abstract ᅟ.

In situ crosslinking and micro-cavity generation in fabrication of polymeric membranes for pervaporation dehydration on methanol aqueous solutions

Crosslinked membranes exhibiting in situ crosslinking and micro-cavity generation in membrane fabrication processes have been reported for pervaporation dehydration on methanol aqueous solutions. Meldrum's acid (MA) modified poly(2,6-dimethyl-1,4-phenylene oxide) (PPO-MA) with various MA contents have been synthesized and well characterized with Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. PPO-MA polymers could perform thermally-induced self-crosslinking reaction through cycloaddition reaction between ketene groups generated from MA thermolysis reaction. Meanwhile, MA thermolysis reaction evolves CO2 and acetone molecules which contribute to generation of micro-cavities in the formed membranes. Consequently, compared to the pervaporative separation performance of pristine PPO membrane (permeation flux: 290 g m−2 h−1; separation factor: 57) on a 90 wt% methanol solution at 25 °C, the crosslinked PPO-MA membrane shows a separation factor of 809 with a slight decrease in permeation flux to about 226 g m−2 h−1. Based on the pervaporation separation index (PSI, the product of permeation flux and separation factor), an 11-times enhancement has been achieved.

High-strength N-methyl-2-pyrrolidone-containing process wastewater treatment using sequencing batch reactor and membrane bioreactor: A feasibility study

N-methyl-2-pyrrolidone (NMP) is widely used as a solvent in polymeric membrane fabrication process, its elimination from the process wastewater (normally at a high concentration > 1000 mg/L) prior to discharge is essential because of environmental concern. This study investigated the feasibility of treating high-strength NMP-containing process wastewater in a sequencing batch reactor (SBR; i.e., batch feeding and intermittent aerobic/anoxic condition) and a membrane bioreactor (MBR; i.e., continuous feeding and aeration), respectively. The results showed that the SBR with the acclimated sludge was capable of removing >90% of dissolved organic carbon (DOC) and almost 98% of NMP within 2 h. In contrast, the MBR with the acclimated sludge showed a decreasing NMP removal efficiency from 100% to 40% over 15-day operation. The HPLC and LC-MS/MS analytical results showed that NMP degradation in SBR and MBR could undergo different pathways. This may be attributed to the dissimilar bacterial community compositions in the SBR and MBR as identified by 16s rRNA gene sequencing analysis. Interestingly, the NMP-degrading capability of the activated sludge derived from MBR could be recovered to >98% after they were operated at the SBR mode (batch feeding mode with intermittent aerobic/anoxic condition). This study reveals that SBR is probably a more feasible process to treat high-strength NMP-containing wastewater, but residual NMP metabolites in the SBR effluent need to be post-treated by an oxidation or adsorption process in order to achieve zero-discharge of toxic chemicals.