Non-solvent Induced Phase Separation Research Articles

Form-Factor Control of Alginate Aerogels Via Thixotropic Sols: From Monoliths to Fibers to Films.

Producing homogeneous alginate aerogel monoliths is challenging due to the uncontrollably fast gelation of sodium alginate (NaALG) solutions, which is typically induced with metal ions. This issue is overcome by decoupling molding from gelation. Aqueous NaALG solutions are first converted into thixotropic liquids via in situ acidification with acetic acid (AcOH) generated gradually through the hydrolysis of acetic anhydride (Ac2O), thus, providing time for casting in molds. The resulting solid-like thixotropic liquids are rigidized into wet gels conforming to the molds by a membraneless dialysis process via nonsolvent-induced phase separation, treatment with strong acids (HCl), or aqueous metal ion solutions (Ca2+, Cu2+, Fe3+, Ni2+, Ag+, Au3+). The thixotropic nature of the NaALG/Ac2O mixtures enables extrusion into fibers or spreading into films, followed by rigidization using the same methods. Wet gels in monolithic, fibrous, or film form were dried into aerogels with supercritical fluid (SCF) CO2. All aerogels were characterized by SEM, N2-sorption porosimetry, IR spectroscopy, solid-state CP MAS 13C NMR, and elemental analysis. Oscillatory rheology tracked the transition of NaALG to thixotropic liquids during Ac2O and AcOH titrations run in parallel. Thixotropic liquids from both titrations were rigidized with the nonsolvent-induced phase separation method and were processed into aerogels establishing that AcOH from the hydrolysis of Ac2O converts up to ∼30% mol/mol of NaALG to alginic acid (ALGH). Conversion of the remaining NaALG in thixotropic liquids to ALGH (>95% mol/mol) requires a strong acid (HCl), while rigidization with metal ions just replaces residual Na. Dynamic mechanical analysis (DMA) showed nearly identical storage moduli (E') for wet gels and aerogels, confirming that the solid network is formed during the rigidization step and is unaffected by subsequent processing. Notably, elemental analysis, porosimetry, and DMA data indicated that gels rigidized with Fe3+ included a secondary network, which, based on literature Mössbauer reports, is assigned to sol-gel-derived iron oxide.

Use of green polar aprotic solvents TamiSolve® NxG, DMSO and methyl-THF for the synthesis of asymmetric polyimide-based biogas purification membranes

Use of green polar aprotic solvents TamiSolve® NxG, DMSO and methyl-THF for the synthesis of asymmetric polyimide-based biogas purification membranes

Preparation of Am-MSN/PVDF Mixed Matrix Membranes for Enhanced Removal of Reactive Black 5

The discharge of large volumes of textile dyeing wastewater, characterized by poor biodegradability and high toxicity, poses severe threats to the environment. In this study, polyvinylidene difluoride (PVDF) membranes were prepared using the nonsolvent-induced phase separation (NIPS) method, with porous amino-functionalized mesoporous silica nanoparticles (Am-MSNs) mixed into the casting solution to fabricate the Am-MSN/PVDF mixed matrix membranes. By varying the amount of Am-MSNs added, the microstructure and overall performance of the membranes were comprehensively analyzed. The results demonstrated that the addition of Am-MSNs significantly enhanced the hydrophilicity of the membranes. The high specific surface area and amino groups of Am-MSNs facilitated interactions with dye molecules, such as Reactive Black 5 (RB5), through hydrogen bonding, electrostatic attraction, and physical adsorption, resulting in a marked improvement in RB5 rejection rates. Static adsorption tests further validated the superior adsorption capacity of the Am-MSN/PVDF mixed matrix membranes for RB5. Additionally, the nanoscale mesoporous structure of Am-MSNs enhanced the mechanical strength of the membranes. The synergistic effects of the mesoporous structure and amino groups significantly increased the efficiency and stability of the Am-MSN/PVDF mixed matrix membranes in dye removal applications, providing an effective and sustainable solution for the treatment of dye-contaminated wastewater.

Elucidation of effects of pore structure in dual-scale electrodes on mass transfer in VRFB via nonsolvent-induced phase separation and laser perforation

Elucidation of effects of pore structure in dual-scale electrodes on mass transfer in VRFB via nonsolvent-induced phase separation and laser perforation

Effects of polyvinylidene difluoride (PVDF) molecular weight on hydrophobic membranes prepared by the plasma assisted nonsolvent induced phase separation (PANIPS) method

Effects of polyvinylidene difluoride (PVDF) molecular weight on hydrophobic membranes prepared by the plasma assisted nonsolvent induced phase separation (PANIPS) method

Tissue Mimetic Membranes for Healing Augmentation of Tendon-Bone Interface in Rotator Cuff Repair.

The globally prevalent rotator cuff tear has a high re-rupture rate, attributing to the failure to reproduce the interfacial fibrocartilaginous enthesis. Herein, a hierarchically organized membrane is developed that mimics the heterogeneous anatomy and properties of the natural enthesis and finely facilitates the reconstruction of tendon-bone interface. A biphasic membrane consisting of a microporous layer and a mineralized fibrous layer is constructed through the non-solvent induced phase separation (NIPS) strategy followed by a co-axial electrospinning procedure. Cationic kartogenin (KGN)-conjugated nanogel (nGel-KGN) and osteo-promotive struvite are incorporated within the membranes in a region-specific manner. During in vivo repair, the nGel-KGN-functionalized microporous layer is adjacent to the tendon which intends to suppress scar tissue formation at the lesion and simultaneously heightens chondrogenesis. Meanwhile, the struvite-containing fibrous layer covers the tubercula minus to enhance stem cell aggregation and bony ingrowth. Such tissue-specific features and spatiotemporal release behaviors contribute to effective guidance of specific defect-healing events at the transitional region, further leading to the remarkably promoted regenerative outcome in terms of the fibrocartilaginous tissue formation, collagen fiber alignment, and optimized functional motion of rotator cuff. These findings render a novel biomimetic membrane as a promising material for clinical rotator cuff repair.

Novel Ultrafiltration Polyethersulfone Membranes Blended with Carrageenan.

The development of ultrafiltration (UF) polymeric membranes with high flux and enhanced antifouling properties bridges a critical gap in the polymeric membrane fabrication research field. In the present work, the preparation of novel PES membranes incorporated with carrageenan (CAR), which is a natural polymer derived from edible red seaweed, is reported for the first time. The PES/CAR membranes were prepared by using the nonsolvent-induced phase separation (NIPS) method at 0.1-4.0 wt.% CAR loadings in the casting solutions. The use of dimethylsulfoxide (DMSO), which is a bio-based and low-toxic solvent, is reported. Scanning electron microscopy, atomic force microscopy, water contact angle, porosity, and zeta potential measurements were used to evaluate the surface morphology, structure, pore size, hydrophilicity, and surface charge of the prepared membranes. The filtration performance of PES/CAR membranes was tested with bovine serum albumin (BSA) solutions. It was shown that CAR incorporation in the casting solutions notably increased hydrophilicity, porosity, pore size, surface charge, and fouling resistance of the prepared membranes compared with plain PES membranes due to the hydrophilic nature and pore-forming properties of CAR. The PES/CAR membranes showed a significant reduction in irreversible and total fouling during filtration of BSA solutions by 38% and 32%, respectively, an enhancement in the flux recovery ratio by 20-40%, and an improvement in mechanical properties by 1.5-fold when compared with plain PES membranes. The findings of the present study indicate that CAR can be used as a promising additive for the development of PES UF membranes with enhanced properties and performance for water treatment applications.

Preparation of polyvinylidene fluoride membranes with enhanced hydrophobicity and its applications in chromium recovery using supported liquid membranes in practical scale

This study focuses on the development of polyvinylidene fluoride (PDVF) membranes with enhanced hydrophobicity and their application for supported liquid membrane (SLM)-based solvent extraction. Flat sheet membranes were prepared via vapor-induced phase separation (VIPS), followed by non-solvent-induced phase separation (NIPS). PVDF flat sheet membrane was prepared with different solvents, namely N-methylpyrrolidone, dimethylformamide (DMF), dimethylacetamide, and dimethylsulfoxide, and at different VIPS times. The effect of different solvents and VIPS time on the membrane characteristics and performance was studied. PVDF membrane prepared with DMF solvent with VIPS time of 7.5 min gave optimum results in terms of membrane characteristics and performance with a water contact angle of 95.5°. The optimized PVDF flat sheet membrane was used as support in a SLM setup for the extraction and recovery of chromium from a simulated aqueous feed solution similar to tannery effluent with concentrations ranging from 5 to 75 ppm. Dodecane, modified with 1-dodecanol and decalin, was used as an organic solvent with tri-caprylmethylammonium chloride (Aliquat 336) as an extractant. NaNO3 solution was used as a stripping solution. The processes of extraction and stripping were carried out simultaneously in a single-step operation to recover chromium. The extraction of chromium achieved in 3 h using an in-house-prepared hydrophobic PVDF membrane as support for the liquid membrane varies from 63.08% for feed containing 5 ppm chromium to 50.59% for feed containing 75 ppm chromium, with a maximum extraction of 70.92% for feed with 50 ppm chromium.

Morphological And Chemical Analysis of PAN/a-CNx Composites Membranes For CO₂ Separation

Thin polymeric membranes have attracted significant interest for CO₂ separation due to their high gas permeance and low cost. However, enhancing selectivity often requires an additional selective layer. This study investigates the role of amorphous carbon nitride (a-CNx) thin film deposited via radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) as a selective layer on polyacrylonitrile (PAN) membrane fabricated through non-solvent induced phase separation (NIPS). Structural and chemical modifications of the membrane due to the introduction of a-CNx thin film were analyzed using Field Emission Scanning Electron Microscopy (FESEM), Brunauer-Emmett-Teller (BET) analysis, and Fourier-Transform Infrared Spectroscopy (FTIR). FESEM shows a textured surface on PAN/a-CNx membrane which confirmed the successful uniform deposition of the a-CNx thin film. BET revealed a slight reduction in BET surface area from 49.84 m²/g to 48.13 m²/g after deposition due to partial pore coverage by the a-CNx thin film. The Langmuir surface area increased from 89.94 m²/g to 97.08 m²/g, indicating the creation of more uniform adsorption sites. BJH analysis showed an increase in cumulative mesopore volume from 0.0994 cm³/g to 0.1073 cm³/g and a significant rise in mesopore width from 8.57 nm to 13.40 nm which implies the merging of smaller pores that led to increase mesoporosity. Both membranes exhibited Type IV isotherms with H3 hysteresis loops that represent characteristic of mesoporous materials, with the PAN/a-CNx membrane displaying a slightly wider hysteresis loop that indicates potential shifts toward slit-like pores. FTIR spectra confirmed the incorporation of a-CNx thin film into the PAN matrix, with characteristic peaks of N-H stretching, C=N stretching, and aromatic C-N stretching. The increase of nitrogen functionalities by the deposition of a-CNx thin film potentially increases CO₂ adsorption through acid-base interactions with nitrogen sites. These findings offer valuable insights for future research on high-performance gas separation membranes.

Optimization of Polyelectrolyte Coacervate Membranes via Aqueous Phase Separation.

Polymeric membranes fabricated via the nonsolvent-induced phase separation process rely heavily on toxic aprotic organic solvents, like N-methyl-pyrrolidine (NMP) and dimethylformamide. We suggest that the "saloplastic" nature of polyelectrolyte complexes (PECs) makes them an excellent candidate for fabricating next-generation water purification membranes that use a more sustainable aqueous phase separation process. In this study, we investigate how the properties of PECs and their interactions with salt can form pore-containing membranes from the strong polyelectrolytes poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) in the presence of potassium bromide (KBr). How the single-phase polymer-rich (coacervate) dope solution and coagulation bath impacted the formation, morphology, and pure water permeance (PWP) of the membranes was systematically evaluated by using scanning electron microscopy and dead-end filtration tests. The impact of a salt annealing post-treatment process was also tested; these treated PEC membranes exhibited a PWP of 6.2 L m-2 h-1 bar-1 and a dye removal of 91.7% and 80.5% for methyl orange and methylene blue, respectively, which are on par with commercial poly(ether sulfone) nanofiltration membranes. For the first time, we have demonstrated the ability of the PEC membranes to repel Escherichia coli bacteria under static conditions. Our fundamental study of polyelectrolyte membrane pore-forming mechanisms and separation performance could help drive the future development of sustainable materials for membrane-based separations.

Characteristics of Polyethersulfone Membranes Modified by Silika and Nanocellulose Extracted from Biomass as Additives

Polyethersulfone membranes were fabricated using non-solvent-induced phase separation (NIPS) with silica and nanocellulose additives extracted from rice husk ash and genjer (Limnocharis flava). N-methyl pyrrolidone served as the solvent. The study aimed to prepare membranes with diverse characteristics by incorporating various combinations of additives. Silica acted as a pore-forming agent, while nanocellulose enhanced membrane hydrophilicity. Characterization techniques included Fourier-transform infrared spectroscopy (FTIR) for functional group analysis, which revealed the presence of C-S, Si-O, and Si-O-Si vibrations in the membranes. Additionally, scanning electron microscopy (SEM) was employed to examine the surface and cross-sectional structure of the membranes. To assess membrane performance, a flux test was conducted. The membrane containing 2% nanocellulose and 1% silica exhibited the highest flux value of 21.37 L/m².h, corresponding to a permeability of 21.37 L/m².h.bar. Based on these results, the membrane with 2% nanocellulose and 1% silica is considered optimal due to its superior performance.

High-Performance Porous Supports Based on Hydroxyl-Terminated Polysulfone and CO2/CO-Selective Composite Membranes.

The scope of this work was to develop a thin-film composite (TFC) membrane for the separation of CO2/CO mixtures, which are relevant for many processes of gas processing and gasification of carbon-based feedstock. Special attention was given to the development of highly permeable porous polysulfone (PSF) supports (more than 26,000 GPU for CO2) since both the selective and support layers contribute significantly to the overall performance of the TFC membrane. The PSF porous support is widely used in commercial and lab-scale TFC membranes, and its porous structure and other exploitation parameters are set during the non-solvent-induced phase separation (NIPS) process. Since the casting solution properties (e.g., viscosity) and the interactions in a three-component system (polymer, solvent, and non-solvent) play noticeable roles in the NIPS process, polysulfone samples in a wide range of molecular weights (Mw = 76,000-122,000 g·mol-1) with terminal hydroxyl groups were synthesized for the first time. Commercial PSF with predominantly terminal chlorine groups (Ultrason® S 6010) was used as a reference. The PSF samples were characterized by NMR, DSC, and TGA methods, and the Hansen solubility parameters were calculated. It was found that increasing the ratio of terminal -OH over -Cl groups improved the "solubility" of PSF in N-methyl-2-pyrrolidone (NMP) and water. A direct dependence of the gas permeance of porous supports on the coagulation rate of the casting solution was identified for the first time. It was shown that the use of synthesized PSF (Mw = 76,000 g·mol-1, Mw/Mn = 3.0, (-OH):(-Cl) ratio of 4.7:1) enabled a porous support with a CO2 permeance of 26,700 GPU to be obtained, while the support formed from a commercial PSF Ultrason® S 6010 (Mw = 68,000 g·mol-1, Mw/Mn = 1.7, (-OH):(-Cl) ratio of 1:1.9) under the same conditions demonstrated 4300 GPU. The siloxane-based materials were used for the selective layer since the thin films based on rubbery polymers do not undergo the same accelerating physical aging as glassy polymers. Two types of materials were screened for the selective layer: synthesized polymethyltrifluoroethylacrylate siloxane-polydecylmethylsiloxane (50F3) copolymer, and polydimethylsiloxane (PDMS). 50F3 siloxane was studied for gas separation applications for the first time. It was shown that the permeance of composite membranes based on high-performance porous supports from the PSF samples synthesized was 3.5 times higher than that from similar composite membranes based on supports from a commercial Ultrason® S 6010 PSF with a permeance value of 4300 GPU for CO2. It was found that the enhanced gas permeance of composite membranes based on the highly permeable porous PSF supports developed was observed for both 50F3 polysiloxane and commercial PDMS. At the same time, the CO2/CO selectivity of the composite membranes with a 50F3-selective layer (9.1-9.3) is 1.5 times higher than that of composite membranes with a PDMS-selective layer. This makes the F-containing 50F3 polysiloxane a promising polymer for CO2/CO separation.

Effect of stretching ratio on the structure and enactment of porous PVDF-HFP hollow fiber membranes for CO2 absorption

Carbon dioxide (CO2) is responsible for increment of the Earth surface temperature and the subsequent environmental issues. In this regard, membrane contactor is one of the emerging technologies that can be applied for controlling CO2 emission. More specifically, the intrinsic structure of membrane plays an important role to govern the performance of CO2 absorption. In this study, considering stretching ratio (SR) as a key factor to affect membrane structural properties, highly porous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) hollow fiber membranes were fabricated by a non-solvent induced phase separation method. The results showed that the membrane dimension and thickness were significantly reduced by optimizing the SR. The optimum membrane structure was found at SR of 1.5 where the mean pore size, CO2 permeance, collapsing pressure and liquid entry pressure of 0.032 μm, 3440 GPU, 550 kPa and 500 kPa were achieved, respectively. The prepared membranes showed open structure with overall porosity of more than 80%. The upgraded membrane at SR of 1.5 presented the maximum CO2 absorption flux of 9.8 × 10− 4 mol/m2 s and the minimum mass transfer resistance of 49,544 (m/s)−1. Furthermore, a stable CO2 absorption performance was achieved during 80 h continuous operation with a flux decline of only about 9%. The findings of this work demonstrated that by applying a cost-effective fabrication method, we can potentially enhance the PVDF-HFP membrane properties for CO2 adsorption without requiring an additional post-modification step.

Crystallization-driven formation of cluster assemblies on surface for super-hydrophobic poly (L-lactic acid)/ZnO composite membrane.

The poly(L-lactic acid) (PLLA)/ZnO composite membrane with cluster assemblies microstructure was constructed by a combination of non-solvent induced phase separation (NIPS) and the Breath-Figure method. In this novel method, the controllable diffusion rate between solvent and non-solvent was introduced to the system by adjusting the non-solvent solubility parameters. The humidity was adjusted to control non-solvent solubility parameters in the Breath-Figure method, which avoids the instantaneous phase separation induced by direct coagulation of water droplets. Hydrophobic modified ZnO nanoparticles were used as heterogeneous nucleation points to induce PLLA crystallization and formation of micro-nano structures. Controlling molecular chain growth with crystal nuclei as templates and constructing cluster assemblies microscopic morphology at 99% humidity, and the size of the cluster decreases gradually from 10μm to 3μm as the nanoparticles content increased up to 5wt%. The surface water contact angle could reach 153.8° with cluster morphology. In addition, the porous structure formed by the polymer-lean phase could increase the porosity to 93.1% and exhibit an excellent oil absorption capacity up to 12.64g/g. It is foreseeable that porous PLLA/ZnO composite membranes have potential applications as biodegradable oil-water separation materials.

Polypyrrole as the MOFs/polymer interfacial binder applied in mixed matrix porous separator for high temperature safe lithium-ion batteries

Polypyrrole as the MOFs/polymer interfacial binder applied in mixed matrix porous separator for high temperature safe lithium-ion batteries

Strength enhanced expandable polyvinyl alcohol/chitosan cryogel for non-compressible hemostasis

For penetrating and deep non-compressible bleeding, hemostatic materials need to meet the demand of easy filling and rapid expansion to close the wound. However, developing an expandable material with sufficient mechanical strength remains a challenge. This study proposed an improved non-solvent induced phase separation (NIPS) method to prepare polyvinyl alcohol/chitosan (PVA/CS) cryogel with large pore structure (70-75 um) and enhanced mechanical properties. The pore structure on the surface enables blood to quickly enter the dry and shape-fixed PVA/CS cryogel, triggering volume expansion. By regulating the hydrogen bond of PVA molecules by CS, the hydrophilia of cryogel was enhanced and the full volume recovery time of PVA/CS15% was shortened (27±3s). The aggregation of PVA molecular in solution enhances the crosslinking, endowing the prepared PVA/CS cryogel with good mechanical properties. The tensile strength of PVA/CS cryogel is up to 0.694±0.044MPa, and the compressive strength reach to 0.32±0.04MPa with 75% compression. The good mechanical properties are beneficial for providing physical support. The preparation method does not require the introduction of toxic chemical cross-linking agents and complicated operation process, which has potential applications in non-compressible hemostasis.

Preparation of a Bi12TiO20/U6M1/PES composite membrane for rhodamine B degradation under visible-light irradiation

Preparation of a Bi12TiO20/U6M1/PES composite membrane for rhodamine B degradation under visible-light irradiation

Low-temperature rapid fabrication of crosslinked poly(quaterphenyl piperidine) membrane for anion exchange membrane water electrolyzers

Low-temperature rapid fabrication of crosslinked poly(quaterphenyl piperidine) membrane for anion exchange membrane water electrolyzers

Influence of different polyether sulfone substrate of thin-film composite forward osmosis membrane on neodymium rejection

Influence of different polyether sulfone substrate of thin-film composite forward osmosis membrane on neodymium rejection

Synergy of molybdenum carbide nanosheets with PMIA separator for regulated Li+ transport in high-performance lithium-ion batteries

Synergy of molybdenum carbide nanosheets with PMIA separator for regulated Li+ transport in high-performance lithium-ion batteries