Polyvinylidene Fluoride Hollow Fiber Membranes Research Articles

Design of continuous flow membrane reactor for in-situ sonophotocatalytic degradation of ciprofloxacin

Antibiotics in the aquatic environments pose a severe threat to global public health. Hence, a sonophotocatalytic membrane reactor (SPMR) of sonophotocatalysis coupled membrane separation was designed to realize continuous and stable degradation of ciprofloxacin (CIP) by Bi2MoO6/FeVO4 in this study. The prepared catalysts were characterized by XRD, SEM, TEM, BET, UV–vis DRS, PL, and EIS. Under the optimal hydraulic retention time (HRT) of 55 min, 93.43% of CIP (10 mg/L) was degraded by Bi2MoO6/FeVO4 (500 mg/L) after 200 min sonophotocatalytic reaction in the presence of H2O2 (20 mM). The synergy index (SI) of sonocatalysis and photocatalysis was calculated to 1.80 during the catalytic process. The SPMR effluent turbidity was basically nil after 10 min separation of catalyst by polyvinylidene fluoride (PVDF) hollow fiber membrane. The changes of PVDF membrane before and after use in SPMR were observed by SEM and FTIR. The membrane fouling behavior in the SPMR was investigated by membrane water flux, flux recovery rate, and membrane resistances. The mechanisms of CIP degradation are attributed to·OH and·holes (h+) generated by Bi2MoO6/FeVO4 under ultrasonic and visible light irradiation. Besides, the solution matrix effects on sonophotocatalytic removal of CIP were investigated. The results proved that SPMR still maintained satisfactory sonophotocatalytic degradation efficiency in typical natural water bodies and simulated water matrices. In this work, the continuous operation process of CIP degradation and catalyst separation was realized, and the membrane fouling was alleviated by ultrasonic.

Enhanced permeability and stability of PVDF hollow fiber membrane in DCMD via heat-stretching treatment

Membrane distillation (MD) demonstrates excellent desalination application potential for high salt concentration wastewater. However, keeping the membrane flux and rejection high during long-term operation remains one of the critical challenges. In this work, a heat-stretching treatment method was proposed to improve the structure of polyvinylidene fluoride (PVDF) hollow fiber membrane and enhance its stability in the MD process. The membrane's pore size decreased after a heat-stretching treatment in water at 120 °C for 1 h. However, the liquid entry pressure of water (LEPw) value and membrane strength increased significantly, making it less prone to pore deformation during the drying or MD process and thus improving the membrane flux and stability in the MD process. The heat-stretching treatment made the PVDF chain arrangement more compact and oriented, avoiding shrinkage in the length direction. Besides stretching, the shrinkage of hollow fiber can be constricted by the combinedeffects of pore filling and stretching due to water or glycerol filling in the membrane pores, thus eliminating the capillary stress caused by liquid evaporation during the air-drying. Consequently, the heat-stretching treatment broke the trade-off between high permeate flux and high stability in the MD process.

Surface modification of porous polyvinylidene fluoride hollow fiber membrane by sulfonated poly(ether ether ketone) coating for membrane distillation of oily wastewater

AbstractHighly porous polyvinylidene fluoride hollow fiber membranes were fabricated by a non‐solvent induced phase separation process. The membranes were modified by coating an ultra‐thin hydrophilic layer of sulfonated poly(ether ether ketone) (sPEEK) onto the inner surface. An industrial oily wastewater treatment was performed through an air gap membrane distillation (AGMD) process. From field emission scanning electron microscopy, the modified membrane showed an open structure with a large finger‐like outer layer and sponge‐like inner layer. The thickness of the coated sPEEK layer on the inner surface was about 0.5 μm. The coated membrane presented mean pore size of 36 nm and overall porosity of 73%. The inner surface water contact angle decreased from about 82° to 57°. Using Langmuir adsorption experiment, minor oil adsorption on the modified membrane surface was confirmed. A stable water flux of about 12 kg m−2 h−1 and oil rejection of 99% were found during 72 h of the AGMD process for treating the oily wastewater of NGL‐900 (Gachsaran, Iran) plant. The high flux recovery ratio of about 98% was related to the improved anti‐oil‐fouling property. The modified membrane can be a potential candidate for oily wastewater treatment through the MD processes.

Unveiling the Impacts of Sodium Hypochlorite on the Characteristics and Fouling Behaviors of Different Commercial Polyvinylidene Fluoride Hollow Fiber Membranes.

Sodium hypochlorite (NaOCl) is a commonly used cleaning agent for recovering membrane performance in membrane technologies. A thorough understanding of the impacts of NaOCl exposure on membrane properties and fouling behavior is important for optimizing chemical cleaning process and extending membrane lifespan. In this study, three commercial polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration membranes (SMM-1010, MEMCOR® CS II and ZeeWeed 500) were used to systematically explore the effects of NaOCl dose and solution pH (8 and 10) on membrane properties. The results showed that membrane pores increased with exposure time prolonging, and more pores were observed at pH 8 aging condition. The amide group in the Fourier transformation infrared spectra was disappeared, while the carboxylic acid and succinimide groups were formed at pH 10 and pH 8 conditions, respectively. The hydrophilicity and pure water permeability (PWP) of SMM-1010 and MEMCOR® CS II membranes had insignificant changes during NaOCl aging process, whereas the hydrophilicity of ZeeWeed 500 membrane slightly decreased and its PWP increased by 1.4-fold. The antifouling properties of NaOCl-aged SMM-1010 and MEMCOR® CS II membranes were slightly improved, whereas the NaOCl-aged ZeeWeed 500 membrane showed severer flux decline with humic acid filtration. Our findings could provide guidance for practical chemical cleaning process optimization.

Surface modification of PVDF membrane via graft polymerization of acetic and acrylic acid

Surface modification of polyvinylidene fluoride (PVDF) hollow fibre membranes through simple chemical treatment is carried out to graft the surface with the presence of carboxylic acid groups. This is to provide means for TiO2 immobilisation in subsequent stages for photocatalysis application. The focus of this study was to identify the highest degree of grafting in order to provide abundant potential sites for subsequent TiO2 assembly. Both acetic and acrylic acid, at varying concentrations, were used and compared as the grafting monomer. It was observed that acrylic acid provides significantly higher grafting degree compared to acetic acid. The highest degree 238 μg/cm2 was obtained at 70% acrylic acid in water, where the surface contact angle significantly reduced to 37o. The highest grafting degree obtained using acetic acid was at 60% in water, which only achieved 31 μg/cm2. Minor improvement was also observed when the solvent for grafting solution was changed from water to toluene; the grafting degree slightly improved by 2% from 238 μg/cm2 to 243 μg/cm2. Higher grafting degree shall allow for more of TiO2 to be immobilized onto the membrane in subsequent work, hence potentially leading to better photocatalysis performance.

Membrane Fouling Mechanism of HTR-PVDF and HMR-PVDF Hollow Fiber Membranes in MBR System

Membrane fouling has attracted a lot of attention in the membrane separation field. Herein, we selected the homogeneous-reinforced polyvinylidene fluoride (HMR-PVDF) and heterogeneous-reinforced polyvinylidene fluoride (HTR-PVDF) hollow fiber membranes to investigate the fouling mechanism of membranes in membrane bioreactor (MBR) systems. The filtration models, membrane adsorption experiment, and membrane resistance distribution after a long or short time operation were assessed to compare their antifouling properties in order to verify the optimal membrane. The outer surface, shown by an SEM observation of the HMR-PVDF and HTR-PVDF membranes, was rough and smooth, respectively. Moreover, the HMR-PVDF membranes had a higher adsorption capacity than the HTR-PVDF membranes when an equilibrium state was almost 2.81 times that of the original membrane resistance. A cleaning method (mainly physical and chemical) was utilized to illustrate the operational stability of the membranes. In summary, the HMR-PVDF hollow fiber membrane presented better antifouling properties than the HTR-PVDF membranes, which was conducive to industrial implementation.

Sound absorption of woven fabrics produced from braid-reinforced polyvinylidene fluoride hollow fiber membranes

Noise pollution has become one of the four major pollutants in modern society, and the development of acoustical materials with superior noise reduction performance is urgent. In order to develop new and high-performance acoustic materials, braid-reinforced (BR) polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared via the dry–wet spinning process and were used to prepare woven fabrics with different basic textures. The effects of pump flux on the structure and performance of BR PVDF hollow fiber membranes was studied. The results showed that pump flux had an impact on the structural parameters, including the diameter, inner coating layer thickness and porosity, and the fabricated BR PVDF hollow fibers with a porous-resonant composite sound absorption structure had good interface bonding performance. Furthermore, the sound absorption of the woven fabrics was measured by using the impedance tube method in frequency range of 100–6300 Hz. The results demonstrated that plain fabric had a smaller thickness of 2.17 mm and better acoustical properties with a maximum sound absorption coefficient of 0.71. These woven fabrics may potentially be used as ideal materials for controlling noise in fields such as building and transportation.

Hollow fiber membrane-protected amino/hydroxyl bifunctional microporous organic network fiber for solid-phase microextraction of bisphenols A, F, S, and triclosan in breast milk and infant formula

Bisphenols and triclosan have been used in various products, and exposure to these chemicals may affect human health. The present study proposes a sensitive method for the determination of bisphenols A, F, S, and triclosan. The fiber was coated by amino/hydroxyl bifunctional microporous organic network and protected by polyvinylidene fluoride hollow fiber membrane for direct immersion solid phase microextraction. The limit of detection was 0.005 μg/L (μg/kg), and the recoveries were in the range of 76.7% to 107.5% (87.4% to 107.6%) for breast milk (infant formula), with intra-day and inter-day precisions <10.5% (7.3%) and 13.6% (8.4%), respectively. Fiber-to-fiber reproducibility of < 9.5% and a lifespan of >100 cycles were obtained. The 95th percentile estimated daily intake of total bisphenols was close to temporary tolerable daily intake for infants fed by human milk, which highlighted the needs for further attention on human exposure to BPA and its substitutes.

Novel Sandwich-Structured Hollow Fiber Membrane for High-Efficiency Membrane Distillation and Scale-Up for Pilot Validation.

Hollow fiber membranes were produced from a commercial polyvinylidene fluoride (PVDF) polymer, Kynar HSV 900, with a unique sandwich structure consisting of two sponge-like layers connected to the outer and inner skin layers while the middle layer comprises macrovoids. The sponge-like layer allows the membrane to have good mechanical strength even at low skin thickness and favors water vapor transportation during vacuum membrane distillation (VMD). The middle layer with macrovoids helps to significantly reduce the trans-membrane resistance during water vapor transportation from the feed side to the permeate side. Together, these novel structural characteristics are expected to render the PVDF hollow fiber membranes more efficient in terms of vapor flux as well as mechanical integrity. Using the chemistry and process conditions adopted from previous work, we were able to scale up the membrane fabrication from a laboratory scale of 1.5 kg to a manufacturing scale of 50 kg with consistent membrane performance. The produced PVDF membrane, with a liquid entry pressure (LEPw) of >3 bar and a pure water flux of >30 L/m2·hr (LMH) under VMD conditions at 70–80 °C, is perfectly suitable for next-generation high-efficiency membranes for desalination and industrial wastewater applications. The technology translation efforts, including membrane and module scale-up as well as the preliminary pilot-scale validation study, are discussed in detail in this paper.

A hydrophobic-hydrophilic MXene/PVDF composite hollow fiber membrane with enhanced antifouling properties for seawater desalination

Hollow fiber membrane-based humidification-dehumidification desalination of seawater is a low-carbon freshwater-harvesting technology that can be powered by low-grade solar energy. Polyvinylidene fluoride (PVDF) can be easily fabricated into membranes and is considered the most promising material for industrial seawater desalination. However, membrane fouling and wetting have always been major obstacles with this technology. In this study, a hydrophobic-hydrophilic MXene/PVDF composite hollow fiber membrane (PVDF-MP) with remarkable antiwetting and antifouling properties was successfully prepared using a chemical grafting method. The interfacial dehydration reaction between the hydrophilic substrate layer (PVDF-OH) and the hydrophobic skin layer (MXene-P [MP]) was verified by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy, and a detailed reaction mechanism was provided. The hydrophilic substrate layer decreased moisture transfer resistance, while the hydrophobic skin layer reduced the membrane surface energy and increased the surface roughness. This resulted in a contact angle of 156.2°, which was measured using a new method that accounted for the curvature of the membrane. The superhydrophobic surface possessed a strong repulsive force toward water, and the air gap between the water and membrane impeded pollutant deposition on the inner surface of the membrane. Moreover, the rough surface created high entry pressure and prevented water from entering the membrane pores. Thus, the permeate flux of the PVDF-MP membrane persisted over 120 h during desalination tests, surpassing the performance of traditional materials. • A hydrophobic-hydrophilic MXene/PVDF composite hollow fiber membrane was prepared. • The PVDF hollow fiber membrane inner surface was superhydrophobically modified. • The interfacial force between the modified layer and substrate was enhanced. • A measuring method for the contact angle of hollow fiber membranes was proposed. • The composite membrane exhibited excellent anti-fouling and anti-wetting ability.

Effect of hollow fiber membrane properties and operating conditions on preventing scale precipitation in seawater desalination with vacuum membrane distillation

Membrane distillation (MD) has attracted attention as a seawater desalination technology because it can treat feed solutions with high osmotic pressures that cannot be treated by reverse osmosis. However, scale precipitation is one of the most significant challenges of MD seawater desalination because it can decrease the vapor permeability and hydrophobicity of MD membranes. Here, the impact of various Reynolds numbers of the feed stream on scaling was investigated. Vacuum MD (VMD) operations with superhydrophobic polyvinylidene fluoride hollow fiber (HF) membranes were performed using seawater at various linear velocities as a feed. Two types of HF membranes with different inner diameters were used. Following 24-h VMD, the amount of scale precipitation on the bore surface of the membrane decreased satisfactorily at a Reynolds number above 1200 due to the decrease in concentration polarization at the bulk/membrane interface. The vapor flux also increased with the Reynolds number. Membranes with larger inner diameters could reduce the amount of scale precipitation and pressure drop, even at the same linear velocity. Thus, it is important for stable VMD seawater desalination to operate at a Reynolds number above 1200 with an HF membrane of large inner diameter.

Experimental and modeling investigation of ultrafine polyvinylidene fluoride hollow fiber membrane module for recovery of lactic acid from aqueous solutions

AbstractThis study investigated the aqueous lactic acid extraction process using indigenous ultrafine polyvinylidene fluoride (PVDF) hollow fiber membrane contactor. Ultrafine PVDF hollow fibers with tighter pore structure were produced by wet spinning technique and fabricated in‐house with an epoxy resin. A kinetic study was performed by varying acid concentrations ranging from 60 to 1320 mol/m3 in an aqueous phase and 210–620 mol/m3 tri‐n‐octylamine (TOA) concentration in 1‐octanol diluent. The solutions were allowed to flow countercurrently using peristaltic pumps at constant aqueous and organic flow velocity of 0.006 and 0.005 m/s, respectively. A PRO/II simulation of the membrane contactor system was carried out to validate experimental results. The study showed a maximum acid extraction of 88 ± 0.1% for initial acid and amine concentrations of 250 and 620 mol/m3, respectively, which corresponds to a high KD value of 11.5 which is larger than the value found from PRO/II simulation for direct mixing of the aqueous and organic phases which demonstrates the merit of the membrane contactor. The exploratory study on kinetics has helped in understanding the mass transfer phenomena of the solute across the membrane. In addition, membrane characterization was done to investigate the surface and cross‐sectional morphologies and mechanical strength properties.

Decreasing free fatty acid of crude palm oil with polyvinylidene fluoride hollow fiber membranes using a combination of chitosan and glutaraldehyde

Crude palm oil (CPO) has emerged as a significant commodity in the economic and social development of producer nations. However, the presence of free fatty acids (FFAs) results in decreased CPO quality. Due to many advantages, the PVDF hollow fiber membrane has a higher potential to remove FFA from CPO than other polymeric membranes, despite the fact that FFA rejection performance remains poor. To solve this issue, membrane surface modification has emerged as one of the potential options for increasing electrostatic contact between the membrane surface and the FFA, resulting in high efficiency FFA separation from CPO. In this investigation, the membrane surface was coated with chitosan (CS) as a coating agent and glutaraldehyde (GA) as a crosslinking agent. The findings of the characterization demonstrated that the presence of a CS/GA combination with a low CS weight on the membrane surface resulted in enhanced hydrophilicity, porosity, water flow, and surface roughness. Furthermore, as compared to the uncoated PVDF hollow fiber membrane, the performance of the CPO with PVDF/CS 0.5 hollow fiber membrane achieved a maximum result of FFA rejection of up to 14.99%. The use of a mixture of CS and GA on the PVDF membrane surface to improve FFA reduction has been shown to be a promising technique for scaling up membrane technology.

Preparation and assessment of polyvinylidene fluoride hollow fiber membrane for desalination by membrane distillation

Preparation and assessment of polyvinylidene fluoride hollow fiber membrane for desalination by membrane distillation

Desirable PVDF hollow fiber membrane engineered with synergism between small molecular weight additives for DCMD treating of a hypersaline brine

Developing membrane for brine waste reclamation via direct contact membrane distillation (DCMD) requires specially membrane characteristics engineering. Toward practical and scalable hydrophobic micromembrane with desirable properties, attaining energy-efficient and durability during hypersaline treatment remains a great challenge. Herein, polyvinylidene fluoride (PVDF) hollow fiber (HF) membranes were developed for particular use in DCMD for treating hypersaline (100,000 mg/L of NaCl solution) via adopting mixture of small molecular weight (MW) additives, including water, lithium chloride (LiCl), and ethylene glycol (EG). Engineered to suppress the limitation of single small MW additives only possessing a unique enhancement in the tailoring of specific properties for improving the partial DCMD performance, the research emphasis is placed on the synergistic effect between small molecular weight additives, resulting in a much-enhanced performance. The dope solution of PVDF/LiCl/H2O/N-Methyl-2-pyrrolidone (NMP) = 12/2/2/84 (wt%) spun HF membrane, P-L-W2, has been shown to reveal the most desirable membrane characteristics for DCMD, including comparable porosity (ε, 74.2 ± 0.4%), superior liquid entry pressure (LEP, 3.05 bar), and robust mechanical properties. The P-L-W2 membrane also exhibited enhanced water flux, energy efficiency, and anti-wetting ability in comparison with the neat PVDF HF membrane. With advantage of easy implement, the concept of adoption of additives mixture provides a novel platform to customize desirable PVDF HF membranes with enhanced DCMD performance.

Fabrication of a superhydrophobic mixed matrix PVDF-SiO2-HDTMS hollow fiber membrane for membrane contact carbon dioxide absorption

In order to obtain high performance polyvinylidene fluoride (PVDF) hollow fiber membrane for post combustion carbon dioxide (CO2) capture from flue gas by membrane contact absorption technology, a novel mixed matrix membrane fabrication process was proposed in this study. The mixed matrix PVDF-SiO2 (silicon dioxide)-HDTMS (hexadecyltrimethoxysilane) hollow fiber membranes fabricated via this process exhibit super-hydrophobicity on the outer surface and high mechanical strength. Among the membranes, the PVDF-SiO2(1.5)-HDTMS membrane exhibited the highest CO2 absorption performance, which was due to its excellent properties. It had water and diethanolamine (DEA, 1 mol/L) contact angles of 159.3° and 157.5°, respectively. Tensile strength, elongation at break, and LEPW (liquid entry pressure of water) of it were 3.2 × 106 Pa, 35.0%, and 9.0 × 105 Pa, respectively. The CO2 absorption flux of PVDF-SiO2(1.5)-HDTMS membrane attained 2.39 × 10−3 mol‧m−2‧s−1, which was 7.2% and 141.4% higher than that of the PVDF-HDTMS-1.5 and PVDF membranes, respectively. Moreover, CO2 absorption flux of the PVDF-SiO2(1.5)-HDTMS membrane decreased only 3% after twenty days of continuous operation. Highlighted by the outstanding performance in membrane contact CO2 absorption, the PVDF-SiO2(1.5)-HDTMS membrane shows great potential in the application of membrane contact absorption for post-combustion CO2 capture.

Seawater Desalination by Modified Membrane Distillation: Effect of Hydrophilic Surface Modifying Macromolecules Addition into PVDF Hollow Fiber Membrane.

Hollow fiber membranes of polyvinylidene fluoride (PVDF) were prepared by incorporating varying concentrations of hydrophilic surface-modifying macromolecules (LSMM) and a constant amount of polyethylene glycol (PEG) additives. The membranes were fabricated by the dry-wet spinning technique. The prepared hollow fiber membranes were dip-coated by hydrophobic surface-modifying macromolecules (BSMM) as the final step fabrication. The additives combination is aimed to produce hollow fiber membranes with high flux permeation and high salt rejection in the matter of seawater desalination application. This study prepares hollow fiber membranes from the formulation of 18 wt. % of PVDF mixed with 5 wt. % of PEG and 3, 4, and 5 wt. % of LSMM. The membranes are then dip-coated with 1 wt. % of BSMM. The effect of LSMM loading on hydrophobicity, morphology, average pore size, surface porosity, and membrane performance is investigated. Coating modification on LSMM membranes showed an increase in contact angle up to 57% of pure, unmodified PVDF/PEG membranes, which made the fabricated membranes at least passable when hydrophobicity was considered as one main characteristic. Furthermore, The PVDF/PEG/4LSMM-BSMM membrane exhibits 161 °C of melting point as characterized by the DSC. This value indicates an improvement of thermal behavior shows so as the fabricated membranes are desirable for membrane distillation operation conditions range. Based on the results, it can be concluded that PVDF/PEG membranes with the use of LSMM and BSMM combination could enhance the permeate flux up to 81.32 kg·m−2·h−1 at the maximum, with stable salt rejection around 99.9%, and these are found to be potential for seawater desalination application.

Impact of NaOCl ageing on reinforced PVDF hollow fiber membranes used in membrane bioreactor

Reinforced hollow fiber membranes are commercially available but its information is limited on open literature. Its notable mechanical properties due to the reinforced layer makes it suitable for membrane bioreactor (MBR) application. On the other hand, polyvinylidene fluoride (PVDF) is an increasingly popular material choice for membrane used in MBR due to its good chemical resistance against chlorine present in sodium hypochlorite (NaOCl), which is commonly used as a cleaning agent. The impact of NaOCl on the PVDF membrane characteristics was reported in literature, but little information is available about the membrane performance of the aged PVDF membrane caused by NaOCl in MBR operation. In this study, the membrane performance of a reinforced PVDF hollow fiber membranes after NaOCl ageing were investigated thoroughly in MBR operations. A series of characterization on virgin and fouled membranes with/without NaOCl exposure were carried out. The accelerated NaOCl ageing experiments revealed that reinforced hollow fiber membranes have notable mechanical strength, which is not significantly affected by NaOCl ageing as compared to their non-reinforced counterpart. Additionally, there was no significant effect on the membrane behaviours in MBR after the membranes were exposed to a 5000 ppm NaOCl solution at pH 7 for 48 h, which is equivalent to 246,000 ppm.hr (~6.1 years) NaOCl exposure using a normal dose of NaOCl for regular membrane cleaning. However, after 524,000 ppm.hr (~13.1 years) of NaOCl exposure, the membrane failed to perform and a sharp transmembrane pressure (TMP) increase during MBR operation was observed. The severe fouling of aged membranes was found to be attributed to the changes in hydrophobicity, pore size and the foulants left on the membrane despite cleaning. Even though the membrane was fouled quickly after 524,000 ppm.hr (~13.1 years) of NaOCl exposure, the permeate quality was not affected much as indicated by >90% removal for dissolved organic carbon (DOC) and soluble chemical oxygen demand (sCOD), which suggests that the reinforced PVDF hollow fiber membranes used in current study exhibit considerable chemical resistance against chlorine and can be used in the MBR system for a long period of operation.

Fabrication of High Performance PVDF Hollow Fiber Membrane Using Less Toxic Solvent at Different Additive Loading and Air Gap

Existing toxic solvents in the manufacturing of polymeric membranes have been raising concerns due to the risks of exposure to health and the environment. Furthermore, the lower tensile strength of the membrane renders these membranes unable to endure greater pressure during water treatment. To sustain a healthier ecosystem, fabrication of polyvinylidene fluoride (PVDF) hollow fiber membrane using a less toxic solvent, triethyl phosphate (TEP), with a lower molecular weight polyethylene glycol (PEG 400) (0–3 wt.%) additive were experimentally demonstrated via a phase inversion-based spinning technique at various air gap (10, 20 and 30 cm). Membrane with 2 wt.% of PEG 400 exhibited the desired ultrafiltration asymmetric morphology, while 3 wt.% PEG 400 resulting microfiltration. The surface roughness, porosity, and water flux performance increased as the loading of PEG 400 increased. The mechanical properties and contact angle of the fabricated membrane were influenced by the air gap where 20 cm indicate 2.91 MPa and 84.72°, respectively, leading to a stronger tensile and hydrophilicity surface. Lower toxicity TEP as a solvent helped in increasing the tensile properties of the membrane as well as producing an eco-friendly membrane towards creating a sustainable environment. The comprehensive investigation in this study may present a novel composition for the robust structure of polymeric hollow fiber membrane that is suitable in membrane technology.

Mechanically strong Janus tri-bore hollow fiber membranes with asymmetric pores for anti-wetting and anti-fouling membrane distillation

Wetting, fouling and mechanical robustness are three major challenges constraining the commercial applications of membrane distillation (MD). Herein, we have developed a robust Janus tri-bore hollow fiber membrane with anti-wetting/fouling resistance. The unique membrane was fabricated by an oxidant-induced deposition of polydopamine/polyethylenimine (PDA/PEI) and a subsequent grafting of sodium-functionalized carbon quantum dots (Na+-CQDs) on top of a hydrophobic tri-bore polyvinylidene fluoride (PVDF) hollow fiber membrane. The PDA/PEI deposition resulted in a nanoporous top layer, and the Na+-CQD grafting significantly enhanced the membrane surface hydrophilicity. In MD operations, the nanoporous PDA/PEI layer endowed the membrane with an excellent rejection to surfactants, thus reducing the wetting propensity, while the grafted Na+-CQDs facilitated the formation of a surface hydration layer, thereby mitigating the oil fouling. This study may expand the applications of mechanically robust tri-bore MD hollow fiber membranes to desalinate hypersaline and harsh wastewaters containing amphiphilic and hydrophobic contaminants.