Coagulation Bath Temperature Research Articles

Investigating the impact of coagulation bath temperature on the properties of biphasic calcium phosphate/poly(vinylidene fluoride)‐based membrane scaffold via immersion precipitation

AbstractIn this study, composite membrane scaffolds comprising poly(vinylidene fluoride) (PVDF) and boron‐containing biphasic calcium phosphate (BCP) are developed using a non‐solvent‐induced phase separation technique at coagulation bath temperatures of −5, 0, 10, and 20 °C. The morphology, pore size and tensile strength of the scaffolds are primarily influenced by the bath temperature. Moreover, raising the bath temperature enhances the thermal properties and β‐crystalline phase fraction. Results demonstrate that changes in the temperature increase the surface hydrophilicity and reduce the degree of swelling. According to the in vitro bioactivity analysis, apatite growth is affected by the interactive relation between the surface of the samples and the simulated body fluid (SBF) medium, in addition to the superior bioactivity of the scaffolds. In vitro cytotoxicity assay results confirm the extensive spreading of L‐929 cells on the sample surfaces, indicating the high biocompatibility of the scaffolds. Based on these favorable properties, the novel composite membranes produced, particularly at 20 °C coagulation bath temperature, may contribute to applications in bone tissue engineering.

Toward Predicting the Formation of Integral-Asymmetric, Isoporous Diblock Copolymer Membranes.

The self-assembly and nonsolvent-induced phase separation (SNIPS) process of block copolymers and solvents enables the fabrication of integral-asymmetric, isoporous membranes. An isoporous top layer is formed by evaporation-induced self-assembly (EISA) and imparts selectivity for ultrafiltration of functional macromolecules or water purification. This selective layer issupported by a macroporous bottom structure that is formed by nonsolvent-induced phase separation (NIPS) providing mechanical stability. Thereby the permeability/selectivity tradeoff is optimized. The SNIPS fabrication involves various physical phenomena-e.g.,evaporation, self-assembly, macrophase separation, vitrification - and multiple structural, thermodynamic, kinetic, and process parameters. Optimizing membrane properties and rationally designing fabrication processes is a challenge which particle simulation can significantly contribute to. Using large-scale particle simulations, it is observed that 1) a small incompatibility between matrix-forming block of the copolymer and nonsolvent, 2) a glassy arrest that occurs at a smaller polymer concentration, or 3) a higher dynamical contrast between polymer and solvent results in a finer, spongy substructure, whereas the opposite parameter choice gives rise to larger macropores with an elongated shape. These observations are confirmed by comparison to experiments on polystyrene (PS)-block-poly(4-vinylpyridine) (P4VP) diblock copolymer membranes, varying the chemical nature of the coagulant or the temperature of coagulationbath.

Adsorption of steroid hormone micropollutant by polyethersulfone ultrafiltration membranes with varying morphology

The effective removal of micropollutants necessitates the use of dense membranes, such as thin-film composite (TFC) reverse osmosis (RO) and nanofiltration (NF) membranes. TFCs have a polyamide active layer interfacially polymerized on a support layer that is typically made of polysulfone (PSu) or polyethersulfone (PES). Retention by NF and RO is often incomplete because micropollutants are adsorbed to the polymer material and subsequently permeate via a combination of convection and diffusion, which evidences a breakthrough curve. When describing breakthrough phenomena, the role of the support membrane is commonly neglected, even though the adsorption in this layer can be significant. This work investigated the adsorption of steroid hormone micropollutants (17β-estradiol, E2) by fabricated and commercial PES ultrafiltration membranes with varying morphology.By increasing the coagulation bath temperature between 10 and 70 °C, the pure water permeability increased from 13 to 3800 L/m2·h−1·bar−1, and consequently, the average pore size rose from 12 to 191 nm. The fabricated membranes with smaller pore sizes showed higher E2 removal via adsorption which can be attributed to the higher internal surface area. The adsorbed mass of fabricated PES membranes (using dimethylformamide (coded as PDG) and N-methyl-2-pyrrolidone (coded as PNG) and PES (Istanbul Technical University (ITU), with non-woven supports) varies from 0.30 to 0.60, 0.27–0.60 and 1–1.2 ng·cm−2, respectively. These values are lower than the adsorbed masses with commercial Biomax (Millipore Inc.) membranes (0.5–2.0 ng·cm−2). Ultrafiltration membranes used as support for composite membranes, nanofiltration or as filters in sample preparation benefit from lower micropollutant adsorption.

On the role of the porous support membrane in seawater reverse osmosis membrane synthesis, properties and performance

In this study, we explore the role of the polysulfone (PSU) support membrane skin-layer and whole-body pore morphology on the physical-chemical properties and separation performance of hand-cast polyamide-PSU (PA-PSU) composite seawater reverse osmosis (SWRO) membranes. We tailor the support membrane pore morphology by varying the PSU concentration and the coagulation bath temperature. In order to isolate the impacts of the PSU support, all of the porous supports are coated using identical m-phenylene diamine (MPD) and trimesoyl chloride (TMC) solution compositions, reaction conditions, and post-treatments. As PSU concentration increases, PSU support membrane pore size, surface and body porosity, water permeability, MPD mass uptake (by the PSU support), and PA-PSU composite membrane water permeability decrease, while MPD and TMC conversion, PA film mass and thickness, crosslinking degree (XD), and PA-PSU composite membrane NaCl rejection increase. As PSU support membrane coagulation bath temperature increases, support membrane pore size, surface and body porosity, MPD uptake, PA film mass, thickness and XD, MPD and TMC conversion, and NaCl rejection increase, while composite PA-PSU membrane water and NaCl permeability decrease. Composite membrane permeabilities were 70–90 percent of the (theoretical) unsupported PA film permeabilities due to the high XD and low PA coating film thickness. Composite PA-PSU membrane water/salt permeabilities both correlate most strongly with PA coating film mass/thickness and XD, which in turn correlate most strongly with TMC conversion. The key to increasing water permeability is lower PA film mass/thickness and XD with higher support membrane surface pore size and porosity. In contrast, the key to increasing NaCl rejection is higher PA film mass/thickness and XD with lower support membrane surface pore size and porosity.

Optimizing influential phase separation parameters on polyethersulfone/ Fe3O4/ZnO membranes for environmental wastewater

Membrane fabrication via phase inversion depends on various influential parameters which may result in enhanced membrane performance. In this study, metal oxide nanoparticles i.e. Fe3O4/ZnO were modified with glycine and diethylene glycol and then embedded onto polyethersulfone (PES) membranes to form PES/Fe3O4/ZnO membranes. These membranes were used to remove manganese, copper, and lead ions from wastewater. Transmission electron microscope images confirmed that Fe3O4/ZnO were composed of cubic and spherical morphologies. Fourier Transform Infrared spectra confirmed that Fe3O4/ZnO nanoparticles were successfully modified using glycine and diethylene glycol. The surface and cross-sectional images showed that polyvinylpyrrolidone (PVP) and the coagulation bath temperature influenced the resulting membrane surface and confirmed the successful addition of nanocomposite concentrations (0.25, 0.50 and 0.75 wt%) onto PES membranes. The 0.50 wt% Fe3O4/ZnO loaded membrane showed highest permeability with water flux of 682 L/m2.h, and high flux recovery ratio (%) of 98.75 %, 88.88 % and 71.77 % for BSA, HA and wastewater samples, respectively, indicative of less prone to fouling. The chemical and mechanical enhancement through PVP concentration, coagulation bath temperature and nanoparticle loading significantly influenced the selectivity and fouling propensity of the PES membranes. Therefore, all parameters played a role in tuning the chemical and physical structure of the prepared membranes.

Influence of PEG-PPG-PEG Block Copolymer Concentration and Coagulation Bath Temperature on the Structure Formation of Polyphenylsulfone Membranes.

The effect of amphiphilic block copolymer polyethylene glycol (PEG)-polypropylene glycol (PPG)-PEG concentration in the polyphenylsulfone (PPSU) casting solution and coagulation bath temperature (CBT) on the structure, separation, and antifouling performance of PPSU ultrafiltration membranes was studied for the first time. According to the phase diagram obtained, PPSU/PEG-PPG-PEG/N-methyl-2-pyrrolidone (NMP) systems are characterized by a narrow miscibility gap. It was found that 20 wt.% PPSU solutions in NMP with the addition of 5-15 wt.% of PEG-PPG-PEG block copolymer feature upper critical solution temperature, gel point, and lower critical solution temperature. Membrane composition and structure were studied by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, and water contact angle measurements. The addition of PEG-PPG-PPG to the PPSU casting solution was found to increase the hydrophilicity of the membrane surface (water contact angle decreased from 78° for the reference PPSU membrane down to 50° for 20 wt.%PPSU/15 wt.% PEG-PPG-PEG membrane). It was revealed that the pure water flux increased with the rise of CBT from 18-20 L·m-2·h-1 for the reference PPSU membrane up to 38-140 L·m-2·h-1 for 20 wt.% PPSU/10-15 wt.% PEG-PPG-PEG membranes. However, the opposite trend was observed for 20 wt.% PPSU/5-7 wt.% PEG-PPG-PEG membranes: pure water flux decreased with an increase in CBT. This is due to the differences in the mechanism of phase separation (non-solvent-induced phase separation (NIPS) or a combination of NIPS and temperature-induced phase separation (TIPS)). It was shown that 20 wt.% PPSU/10 wt.% PEG-PPG-PEG membranes were characterized by significantly higher antifouling performance (FRR-81-89%, DRr-26-32%, DRir-10-20%, DT-33-45%) during the ultrafiltration of bovine serum albumin solutions compared to the reference PPSU membrane prepared at different CBTs (FRR-29-38%, DRr-6-14%, DRir-74-89%, DT-88-94%).

Development and Study of Novel Ultrafiltration Membranes Based on Cellulose Acetate.

Recently, increasing attention of researchers in the field of membrane technology has been paid to the development of membranes based on biopolymers. One of the well-proven polymers for the development of porous membranes is cellulose acetate (CA). This paper is devoted to the study of the influence of different parameters on ultrafiltration CA membrane formation and their transport properties, such as the variation in coagulation bath temperature, membrane shrinkage (post-treatment at 80 °C), introduction to casting CA solution of polymers (polyethylene glycol (PEG), polysulfone (PS), and Pluronic F127 (PL)) and carbon nanoparticles (SWCNTs, MWCNTs, GO, and C60). The structural and physicochemical properties of developed membranes were studied by scanning electron and atomic force microscopies, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements. The transport properties of developed CA-based membranes were evaluated in ultrafiltration of bovine serum albumin (BSA), dextran 110 and PVP K-90. All developed membranes rejected 90% compounds with a molecular weight from ~270,000 g/mol. It was shown that the combination of modifications (addition of PEG, PS, PL, PS-PL, and 0.5 wt% C60) led to an increase in the fluxes and BSA rejection coefficients with slight decrease in the flux recovery ratio. These changes were due to an increased macrovoid number, formation of a more open porous structure and/or thinner top selective, and decreased surface roughness and hydrophobization during C60 modification of blend membranes. Optimal transport properties were found for CA-PEG+C60 (the highest water-394 L/(m2h) and BSA-212 L/(m2h) fluxes) and CA-PS+C60 (maximal rejection coefficient of BSA-59%) membranes.

Facile modification of polyvinylidene fluoride membrane for enhancing dialysis performance: sulfonation, adding polyethylene glycol and tuning coagulation bath temperature

Modifications were successfully carried out on the polyvinylidene fluoride (PVDF) flat sheet membrane, involving the sulfonation and adding polyethylene glycol (PEG), along with variations in the coagulation bath temperature (CBT). The primary objective of these modifications was to examine their impact on the physicochemical characteristics of the membrane and its permeability to a creatinine solution. The findings revealed that the sulfonated PVDF/PEG membrane, printed at a temperature of 30 °C, displayed substantial increases in porosity, hydrophilicity, water uptake and swelling degree. It is important to note that modifications to the PVDF membrane led to a reduction in thermal stability and an increase in creatinine transport efficiency. For the unmodified PVDF membranes, the clearance values for creatinine in phosphate buffer and phosphate buffer saline media were 0.43 (Transport = 28.65%) and 0.42 mg/dL (Transport = 28.05%), respectively. Conversely, the highest creatinine clearance values were achieved by the SPP30 membrane (sulfonated PVDF/PEG-CBT 30 °C), measuring 0.64 mg/dL (Transport = 42.81%) for creatinine and 0.60 mg/dL for urea (Transport = 39.66%). These results indicate that the sulfonated PVDF/PEG membrane exhibits strong potential for use in hemodialysis applications.

Evaluation of anti‐wetting nano‐fumed silica/PVDF hollow‐fiber membrane by central composite design optimization towards efficient desalination performance via membrane distillation

AbstractBACKGROUNDMembrane distillation (MD) is considered a viable technology to overcome the issue of water scarcity by desalination of seawater. However, the application of MD has been severely restricted by membrane‐wetting phenomena. This study aims to optimize the desired mixed‐matrix hollow‐fiber (HF) membrane conditions that have anti‐wetting characteristics for efficient desalination. Response surface methodology based on central composite design was used to predict and optimize the permeate flux and salt rejection (SR). The combined effects of polymer (polyvinylidene fluoride, PVDF) concentration, nano‐fumed silica (NFS) particle loading, coagulation bath temperature (CBT) and air gap distance (AG), as well as their interactions in terms of desalination performance, have been investigated.RESULTSThe linear factors (NFS, CBT), the quadratic effects of all variables, as well as the interacting terms between (PVDF, NFS), (PVDF, CBT) and (NFS, CBT) had significant effects for both pure water and permeate fluxes. For SR, only PVDF presented a linear effect, while a quadratic effect was obtained in (NFS, AG) and an interaction effect was obtained between PVDF and NFS. Under optimal conditions of PVDF (15.03 wt%), NFS (1.21 wt%), CBT (54.85 °C) and AG (9.9 cm), the optimal mixed‐matrix HF membrane demonstrated higher experimental average values for pure water and permeate fluxes, which reached up to 11.95 and 11.61 kg m−2 h−1 respectively, and an SR of 99.96% as compared to the pristine membrane.CONCLUSIONOur research provides an efficient anti‐wetting NFS/PVDF mixed‐matrix HF membrane, indicating that the optimal membrane possesses high potential for the direct contact membrane distillation (DCMD) process. © 2023 Society of Chemical Industry (SCI).

Preparation and characterization of PSF/SPSF blended ultrafiltration membranes

Purpose This paper aims to improve the permeability and antifouling of polysulfone (PSF) ultrafiltration membranes, the PSF matrix was modified by incorporating sulfonated polysulfone (SPSF). Design/methodology/approach Systematic investigations were conducted on the synergistic effects of a pore-forming agent, coagulation bath temperature and SPSF doping in the casting solution on blended ultrafiltration membranes. The chemical composition of the membranes was analyzed using Fourier transform infrared spectroscopy. The morphology and surface roughness of the membranes were characterized using scanning electron microscopy and atomic force microscopy. The hydrophilicity of the membrane surface was analyzed using a contact angle meter. The permeability and antifouling properties of the blended membranes were also investigated through filtration experiments. Findings The results indicated that the blended ultrafiltration membranes demonstrated an optimal overall performance when PVP-K30 content was 5.0 Wt.%, coagulation bath temperature was 30°C and SPSF content was 2.4 Wt.%. In comparison to a pure PSF ultrafiltration membrane, there was a significant increase in pure water flux (390.7 L·m−2·h−1) by 2.2 times, while bovine serum albumin retention slightly decreased to 93.8%. In addition, the flux recovery rate improved by 2.1 times (71.4%) compared to that of the original PSF ultrafiltration membrane. Practical implications The method provided a simple and practical solution for improving the antifouling and permeability of PSF ultrafiltration membranes. Originality/value SPSF was anticipated to serve as an excellent modification additive for the preparation of ultrafiltration membranes with superior properties.

Separation of oil-water emulsion by cellulose acetate ultrafiltration membranes

ABSTRACT This study reports the separation of oil from water using cellulose acetate (CA) ultrafiltration (UF) membranes. The CA membranes were fabricated by varying bath temperatures such as 5 ± 2°C, 25 ± 2°C and 45 ± 2°C using the phase inversion technique and assess their performance based on the oil removal efficiency. Changing the coagulation bath temperature (CBT) at that stage of membrane formations affects the porosity, pore size, hydraulic resistance, morphological structure and performance of membranes. The obtained results revealed increased porosity and pore size and also decreased hydraulic resistance of the membranes as the CBT increases. Field Emission Scanning Electron Microscopy (FESEM) images indicate that a large number of surface pores are visibly found at the higher bath temperature. Atomic force Microscopy (AFM) images show increased average roughness (R a) of the membrane as the CBT of the membrane increases. The water flux and permeate flux of all the membranes tend to increase with an increase in CBT. From Chemical Oxygen Demand (COD) studies, the oil removal efficiency was maximum for the lower bath temperature membrane. The results indicate that conditions of the coagulation bath significantly affect the porous structure, morphology and performance of the membrane.

Upcycling Poly(ethylene terephthalate) by Fabricating Membranes for Desalination

Waste plastic upcycling is attracting increasing attention as a green and sustainable route for membrane fabrication. However, the existing literature in this domain is limited only to few commercial applications. This work presents the performance of membranes synthesized from recycled poly(ethylene terephthalate) (PET) for water desalination. PET extracted from waste plastic bottles was used to produce asymmetric membranes via nonsolvent-induced phase separation. The membrane performance was optimized by fine-tuning the PET, cosolvent, and additive concentration and the coagulation bath temperature. Increasing the PET content in the casting solution led to a decline in permeance across all experiments. A higher % composition of the volatile cosolvent in the solution improved the membrane selectivity. The addition of poly(ethylene glycol) as a pore-forming agent enhanced the permeance, and a higher NaCl rejection was observed when the coagulation bath temperature was decreased from 25 to 0 °C. Subsequently, PET membranes were also used as a support to fabricate thin-film composite membranes via interfacial polymerization of trimesoyl chloride and piperazine. These membranes demonstrated a remarkable permeance of 73 ± 4 L m–2 h–1 bar–1 with a 33 ± 2% NaCl rejection. The findings of this study offer promising prospects for developing high-performance membranes using commercial plastic waste.

Phase-Field Simulation of the Effect of Coagulation Bath Temperature on the Structure and Properties of Polyvinylidene Fluoride Microporous Membranes Prepared by a Nonsolvent-Induced Phase Separation.

We used the phase-field model of the existing Nonsolvent Induced Phase Separation (NIPS) method to add the variable of temperature in simulating the changes in the process of membrane formation. The polyvinylidene fluoride (PVDF) membrane system was applied to examine the influence of coagulation bath temperature change on the skin-sublayer of the membrane structure, thereby elucidating the development process of membrane structure under different conditions and shedding light on the most suitable coagulation bath temperature ranges. It was found that as coagulation bath temperature increased, the number of interface pores in the outer skin layer decreased, but the size increased. As a result, it changed from the crack shape to round-hole shape, thus making the pore structure looser. In the sublayer, the mesh support structure was increased, which enhanced the mechanical strength of the membrane. Relevant experiments also verify the effectiveness of the model.

Influence of ethanol content and temperature in coagulation bath on the microstructure and performance of polyvinylidene fluoride ultrafiltration membranes

In this article, polyvinylidene fluoride (PVDF) ultrafiltration membranes were prepared via phase inversion method. The influence of different ethanol content and temperature in coagulation bath on the microstructure of PVDF membranes was discussed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM) measurements. Rejection experiment was conducted with the bovine serum albumin (BSA) solution. The FTIR and XRD analysis showed the higher ethanol content and temperature of coagulation bath promoted the α crystal form of PVDF membranes. The increase of ethanol content in coagulation bath led to a decrease in the mean pore size and porosity and the increase of BSA rejection rate and break strength of PVDF membranes. This was because of the increase of ethanol content in coagulation bath that resulted in the formation of the more sponge-like structures and the fewer finger-like structures, which enhanced the compactness of the membranes. The PVDF membrane prepared in ethanol/pure water (60/40) coagulation bath at 20 °C showed a greater BSA rejection rate of 91.87% and break strength of 1.89 MPa with a mean pore size of 29.26 nm. Meanwhile, the increase in temperature of coagulation bath had a positive effect on the mean pore size, porosity, and hydrophilicity of PVDF membranes to a certain extent.

UiO-66-NH2 nanocomposites incorporated cellulose acetate for forward osmosis membranes of high desalination performance

ABSTRACT In this paper, the hydrophilic UiO-66-NH2 nanomaterial was synthesized by the solvent-thermal method and characterized. Then, UiO-66-NH2 was introduced into the casting membrane solution of cellulose acetate (CA) forward osmosis (FO) membrane, and CA/UiO-66-NH2 forward osmosis membrane was prepared by the phase inversion method. The optimum preparation conditions of CA/UiO-66-NH2 mixed matrix membranes were determined as follows: the content of UiO-66-NH2 was 0.4 wt%, the coagulation bath temperature was 35°C, the mixing temperature was 50°C and the heat treatment temperature was 50°C. FTIR, SEM, water contact angle and AFM were carried out on CA/UiO-66-NH2 forward osmosis membrane prepared under the best preparation conditions. Compared to the CA forward osmosis membrane, the permeability and selectivity of the CA/UiO-66-NH2 membrane were improved. The water flux and reverse salt flux of the CA/UiO-66-NH2 forward osmosis membrane reached 52.32 L/(m2·h) and 2.43 g/(m2·h), respectively. The permeability selectivity of CA membranes and CA/UiO-66-NH2 membranes did not change much during 180 min, indicating that the two membranes had good long-term stability. This study shows a potential advantage of UiO-66-NH2 as additives for improvement in the desalination performance of forward osmosis membranes.

Development of High Flux Nanocomposite Polyphenylsulfone/Oxidized Multiwalled Carbon Nanotubes Membranes for Ultrafiltration Using the Systems with Critical Solution Temperatures.

The study deals with the investigation of the effect of the modification of polyphenylsulfone (PPSU) flat sheet membranes for ultrafiltration using oxidized multiwalled carbon nanotubes (O-MWCNT) in order to enhance membrane permeability and antifouling performance. The effect of O-MWCNT loading to the PPSU-polyethylene glycol (PEG-20,000, Mn = 20,000 g·mol−1)-polyvinylpyrrolidone (PVP K-30, Mn = 40,000 g·mol−1)-N-methy-2-pyrrolidinone (NMP) colloid systems on the phase state and viscosity was studied. It was found that PPSU-PEG-20,000-PVP K-30-O-MWCNT-NMP colloid systems feature a gel point (T = 35–37 °C) and demixing temperature (T = 127–129 °C) at which two bulk phases are formed and a polymer system delaminates. According to the study of the phase state and viscosity of these colloid systems, a method for the preparation of high flux PPSU membranes is proposed which includes processing of the casting solution at the temperature higher than gel point (40 °C) and using a coagulation bath temperature lower than gel point (25 °C) or lower than demixing temperature (40 °C and 70 °C). Membrane structure, topology and hydrophilic-hydrophobic balance were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and water contact angle measurements. The effect of coagulation bath temperature and O-MWCNT concentration on the membrane separation and antifouling performance in ultrafiltration of human serum albumin and humic acids solutions was studied. It was found that the modification of PPSU ultrafiltration membranes by O-MWCNTs yielded the formation of a thinner selective layer and hydrophilization of the membrane surface (water contact angle decreased from 53–56° for the reference PPSU membrane down to 33° for the nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT). These changes resulted in the increase in membrane flux (from 203–605 L·m−2·h−1 at transmembrane pressure of 0.1 MPa for the reference membrane up to 512–983 L·m−2·h−1 for nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT depending on coagulation bath temperature) which significantly surpasses the performance of PPSU ultrafiltration membranes reported to date while maintaining a high level of human serum albumin rejection (83–92%). It was revealed that nanocomposite membrane demonstrated better antifouling performance (the flux recovery ratio increased from 47% for the reference PPSU membrane up to 62% for the nanocomposite membrane) and higher total organic carbon removal compared to the reference PPSU membrane in humic acids solution ultrafiltration.

Preparation and characterization of porous polyimide fibers with electromagnetic wave absorption properties

AbstractThe porous polyimide (PI) composite fibers, which exhibit high‐efficiency electromagnetic wave adsorption (EMWA) performance, were successfully fabricated by controlling temperature of the coagulation bath during the wet spinning process. The mechanical properties of composite fiber decreased and average radius of micropores increased gradually with the rise of coagulation bath temperature. In addition, carbon nanotubes (CNTs) and nano‐Fe3O4 were introduced into the system by in situ polymerization. CNTs and nano‐Fe3O4 contribute to the attenuation of electromagnetic wave (EMW) through microwave absorption and reflection loss (RL), and the porous structure was able to provide multiple reflection paths for incident EMW and achieved higher attenuation. Particularly, when the temperature of coagulation bath was 50°C, the minimum RL (RLmin) value of the PI/CNTs/nano‐Fe3O4 (PI/C‐Fe) composite fibers was demonstrated to be −54.61 dB with the matching thickness of 2.10 mm. The successful preparation of PI/C‐Fe composite fiber in this study pointed out a new direction for the application of PI‐based fiber materials in structural EMWA materials.

Fabrication of polysulfone membrane with sponge-like structure by using different non-woven fabrics

The porous support layer with sponge-like structure has been widely used in thin-film composite (TFC) membranes. A series of polysulfone (PSf) support membranes with different sponge-like structure were fabricated via non-solvent induced phase separation (NIPS) method. The influences of membrane fabrication parameters including coagulation bath temperature, relative humidity, pre-evaporation time and membrane thickness on PSf membrane properties were systematically explored. The sponge-like-structured PSf membranes were formed while the coagulation bath temperature, relative humidity, pre-evaporation time and membrane thickness were 60 °C, 20%, 30 s, and 60 μm, respectively. Additionally, three types of polyethylene terephthalate (PET) non-woven fabrics (NWFs) with different properties were selected to study the influencing mechanism on PSf membrane with sponge-like structure. It was found that the PSf membrane (PSf-NWF-01) formed on more hydrophilic PET NWFs exhibited higher porosity (63%) and excellent performances (with a pure water flux of 463.69 L/(m2·h) and the BSA rejection of 97.58%), which was caused by a higher adhesion existed between more hydrophilic NWF surface and PSf casting solution. Moreover, the PSf-NWF-01 membrane also exhibited the highest flux recovery ratio of 88.59% and the lowest irreversible fouling of 11.41%. This work academically clarified the influence mechanism of PET NWFs properties on spongy-like PSf membranes, which also had theoretical guidance for selecting appropriate PET NWFs for the preparation of PSf membranes in industry.

Antipathogenic upcycling of face mask waste into separation materials using green solvents

The use of disposable face masks has considerably contributed toward waste generation, particularly during the current COVID-19 pandemic. Little attention has been dedicated to the actual examination of recycling strategies for increasing the life cycle of this biomedical waste, as the most common treatment for disposing used masks is incineration. In this study, we screened green solvents for the recycling of face masks by taking advantage of their antipathogenic nature for sterilization purposes. This work is timely and unique because it presents for the first time the successful recovery of polypropylene from face masks, and upcycle of the masks into either a microbead or free-standing membranes as separation materials. Owing to their excellent chemical stability, the membranes are well-suited for organic solvent nanofiltration. The fabricated membranes exhibited molecular weight cut-off values between 665 and 964 g mol−1, which were fine-tuned by adjusting the coagulation bath temperature from 20 °C to 60 °C. The membranes demonstrated long-term stability over 5 days of continuous filtration at 30 bar, with rejection values exceeding 98% for roxithromycin and rose bengal. This scalable methodology for upcycling used face masks into high-value products has the potential to reduce a crucial environmental threat associated with the global rapid growth of the face mask market.

Investigating the Effects of Nonsolvent Additive and Spinning Conditions on Morphology and Permeation of PAN Hollow Fiber Membranes

In this study, polyacrylonitrile hollow fiber (PAN HF) membranes were designed and fabricated with desired morphology and permeability for low pressure-driven applications via the dry-wet phase-inversion spinning process. The effects of multiple design and fabrication parameters on permeation, morphology, thickness, and pore size of membranes were investigated using various techniques. Moreover, the effects of water as the nonsolvent additive, chemical composition of the bore solution, dope solution flow rate, air gap, coagulation bath temperature, and tensile ratio (take-up speed) were investigated. The addition of 3% wt. water as the nonsolvent additive into the dope solution resulted in a seventeen-times increment in the water flux up to 495 L m-2 h-1 bar-1. It showed a significant improvement in membrane porosity compared with those prepared without water nonsolvent additive. Utilization of 90% wt. of the solvent in water solution as the bore solution instead of pure water showed the most significant effect on the water flux and membrane structure among the fabrication parameters. It resulted in a reduction in threshold permeation pressure by more than ten times. The results revealed that whichever variation, including increased dope solution flow rate or coagulation bath temperature, or reduced air gap or traction, leads to promotion of membrane water flux. Still, different effects on the structure and morphology of the membranes were observed. Based on the outcomes of this study and according to the SEM images, one can conclude that outer surface pore size reduction from about 300 nm resulted in decreased water flux from 448 to 226 L m-2 h-1 bar-1, so that no pores were observed in the outer surface until 50 K magnification of the SEM image. The findings in this study provide instructive guidelines for the design and fabrication of high-performance hydrophilic PAN-based hollow fiber membranes with the desired morphology and water flux. Best ranges of investigated parameters for relatively high permeate water flux and desired membrane morphology were reported.