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Membrane separation technology as an effective and energy-saving method is playing an important role in solving water crisis. High-density polyethylene (HDPE) with excellent comprehensive performance is an ideal material for the preparation of separation membrane. However, it is susceptible to fouling during separation process owing to its inherent hydrophobicity and is difficult to prepare HDPE porous membranes with uniform pore size distribution. In this work, HDPE membranes with improved hydrophilicity and uniform pore size distribution were successfully prepared via thermally induced phase separation with white oil as diluent. Meanwhile, ethylene–vinyl acetate (EVA) and polyethylene glycol (PEG20000) as hydrophilic polymer additives were added, while silica nanoparticles (SiO2) or multilayer graphene oxide were used as hydrophilic inorganic additives respectively. In particular, the influence of additives and coagulation bath temperatures on the properties of the membranes were investigated in detail. The hydrophilicity of the HDPE membranes was improved, and the thickness of the dense skin layer decreased effectively with the addition of 5% EVA, 5% PEG20000 and 2% SiO2. The pure water flux (407.63 L·m–2·h–1) was about 7.65 times higher than the pure HDPE membrane. In particular, the appropriate increase in the coagulation bath temperature was conducive to crystal growth and diluent aggregation. Furthermore, the mean pore size, porosity, and pure water flux all increased significantly, while the BSA rejection ratio decreased slightly. The prepared HDPE membranes showed high rejection ratio (> 99.9%) for the carbon ink particles, long-term and cyclic filtration stability, and excellent corrosion resistance to the aggressive chemical solutions. [ABSTRACT FROM AUTHOR]

The matrix of poly(fluorinated ethylene‐propylene) (FEP) was modified with graphene (GE) as filler, and then the composite fibers were prepared by melt spinning method with a twin‐screw extruder. The effects of both the draw ratio and GE content on the structures and properties of FEP/GE composite fibers were investigated. The results showed that the addition of nanoparticles reduced the crystallization of molecular chains and the orientation of crystalline units in the fibers, while the drafting and heat setting process could effectively improve the crystallinity and orientation of composite fibers. Moreover, the addition of GE improved the mechanical properties of the composite fibers and had no effect on the chemical resistance of the composite fibers. A significant enhancement of mechanical properties of the composite fibers was obtained at low GE content, that, a 35.5% improvement of tensile strength and a 19.5% increase of Young's modulus were achieved at a GE content of only 0.3 wt%. Compared with pure FEP fibers, the oil affinity of composite fibers was also significantly improved. The prepared FEP/GE composite fibers that showed excellent chemical resistance have potential application in oil‐water separation, especially in high temperature resistant fibrous materials. [ABSTRACT FROM AUTHOR]

A novel polyvinylidene fluoride-co-hexafluoropropyle (PVDF-HFP)/graphene (GE) tubular nanofiber membrane (TNM) for application in continuous oil/water separation was firstly fabricated in this study. The obtained PVDF-HFP/GE TNMs showed outstanding mechanical properties due to the reinforcement of polyester braided tube. In addition, the effect of GE concentrations on membrane structure and performance was investigated by field-emission scanning electron microscopy, hydrophobicity, pore size and its distribution, porosity and liquid entrance pressure. The results showed that, the prepared TNMs had ideal membrane structure and performance with moderate addition of GE. When the GE concentration was 0.03 wt%, the obtained TNMs exhibited a superior selective wettability and could achieve separating surfactant- stabilized water-in-oil emulsion with a remarkable separation rate and separation efficiency. [ABSTRACT FROM AUTHOR]

Abstract In general, the twisted fiber bundle with good fiber cohesion could be regarded as a new kind of supporting layer. Herein, a new type of poly(p-phenyleneterephthalamide) (PPTA) twisted fiber bundle-reinforced (FR) cellulose triacetate (CTA) hollow fiber reverse osmosis (RO) membrane was fabricated using a twin-screw spinning machine by the melt spinning method. Moreover, the morphologies, surface analysis and permeability of FR CTA hollow fiber RO membrane were investigated by scanning electron microscopy, confocal scanning microscopy and filtration performance. The CTA separation layer exhibited the favorable interfacial bonding state between CTA separation layer and PPTA twisted fiber bundle supporting layer. Especially, the advantages of FR CTA hollow fiber RO membrane could overcome the negative effect of permeability flux loss, due to the easy vulnerable to the compaction of CTA membrane when operating at moderate or high pressure process. Besides, the tensile strength increased from 9.2 to 96.8 MPa because of the higher interfacial stress transfer coefficient, which was achieved due to the interfacial bonding of FR CTA hollow fiber RO membrane. Besides, based on the filtration performance and long-term running test, FR CTA hollow fiber RO membrane with thin separation layer not only produced higher and more stable permeability flux while their salt rejection were basically the same, but also came into being smaller amount of deformation without defects than pristine CTA hollow fiber RO membranes after 200 h operation. Highlights • Twisted fiber bundle-reinforced CTA hollow fiber RO membrane was prepared for the first time. • Membrane with thinner separation layer possessed of higher permeate flux with tiny change of salt rejection. • Twisted fiber bundle-reinforced CTA hollow fiber RO membranes displays long-term operation stability. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The PSF/GO loose NF hollow fiber membranes were fabricated by one-step NIPS method. • Air was used as bore fluid to eliminate the double diffusion in the inner surface. • The membranes exhibited excellent separation performance for textile wastewater. Abstract In this work, we reported the fabrication of novel loose nanofiltration (NF) hollow fiber membranes with dense-loose structure by one-step non-solvent induced phase separation (NIPS) method without post treatment. We selected air and graphene oxide (GO) as bore fluid and additive, respectively. The effects of air and GO on the properties of the prepared membranes were investigated based on field emission scanning electron microscope (SEM) image, pore size distribution, differential scanning calorimetry (DSC), Raman spectra, X-ray photoelectron spectrometer (XPS), water contact angle, zeta potential, mechanical strength, permeability, and rejection. The prepared membranes presented a long-term stability with a high dye rejection of 99.9% for treating the simulated textile wastewater. Meanwhile, the flux was much higher than those of the other reported membranes. Therefore, our prepared membranes showed a great potential for treating textile wastewater. [ABSTRACT FROM AUTHOR]

Graphene and its derivatives have been considered intensively in the development and application of new types of adsorption and separation functional materials, due to its unique structure and superior performance. A comprehensive review on recent studies on adsorption and separation functional materials is given, including graphene, graphene oxide, graphene gel, graphene‐based sponge, graphene separation membrane as well as graphene continuous oil absorption and separation materials. Moreover, the preparation methods and application prospects are mainly utilized to illustrate the research progress. Especially, it is predicted that layered graphene membrane and graphene continuous oil absorption and separation materials may be the most research worthy. Due to their unique structure and excellent performance, graphene and its derivatives are considered as promising candidates in the development and application of new types of adsorption and separation functional materials, helping in water and environmental pollution. Recent studies on adsorption and separation functional materials, preparation methods, and application prospects are overviewed. [ABSTRACT FROM AUTHOR]

Abstract We proposed a facile and robust strategy for fabricating tubular polytetrafluoroethylene (PTFE) / poly (tetrafluoroethylene- co -hexafluoropropylene) (FEP) ultrafine fibers-covered porous membranes for continuous oil/water separation via electrospinning-sintering method. Specifically, PTFE/FEP/poly (vinyl alcohol) (PVA) ultrafine fibers were electrospun covering on a porous supporting tube which served as the outer layer of the porous membranes. Manipulation of shapes by control of FEP additions enabled the creation of PTFE porous membranes with optimized membrane pore structure during the sintering process. Meanwhile, the obtained membranes had excellent oil/water selectivity in oil/water separation. Moreover, they could effectively separate surfactant-stabilized water-in-oil emulsions with separation efficiency as high as 99.9% and high flux (134 L m−2·h−1 at 0.5 bar). Therefore, tubular PTFE/FEP ultrafine fibers-covered porous membranes enabled an efficient separation for various oil/water emulsions, showing attractive potential for practical oil/water separation. Graphical abstract fx1 Highlights • Tubular PTFE/FEP ultrafine fibers-covered porous membrane were prepared through electrospinning and sintering method. • The introduction of FEP particles was expected to fully fuse to optimized membrane pore structure. • The prepared porous membrane exhibited superhydrophobic and superoleophilicity. • The prepared porous membrane had excellent selectivity and flexibility in oil/water separation. [ABSTRACT FROM AUTHOR]

Non-woven fabric (NWF) has become one of the most important segments in filtration field. Herein, a new type of polyethylene-terephthalate (PET) NWF reinforced “sandwich” cellulose triacetate (CTA) composite reverse osmosis (RO) membrane (NCR membrane) was prepared by melting method. Moreover, the structure and performance of NCR membranes with different separation layer thickness were investigated by ATR-FTIR, SEM, and mechanical property and so on. The results indicated that the NWF supporting layer not only provided well interfacial bonding state with separation layer but also overcame the negative effect of CTA RO membrane's permeate flux loss, due to its easy compaction at a moderate or high operating pressure. Furthermore, all the same ATR-FTIR spectrum of NCR membranes indicated that NWF was wrapped up by CTA melt. Besides, the mechanical property exhibited that the tensile strength increased from 7.5 to 19.5 MPa when introducing the NWF into membrane matrix. Also, based on both membrane morphologies and performance, the optimal membrane thickness was 150 μm with adequate permeate flux and higher salt rejection. Finally, the long-term stable RO testing also exhibited that introducing NWF supporting layer with suitable thickness of separation layer was useful for compaction resistance and stable permeability of NCR membranes. [ABSTRACT FROM AUTHOR]

In this study, a novel thermally stable thin film composite (TFC) nanofiltration (NF) membrane was prepared by interfacial polymerization using poly (m-phenyleneisophthalamide) (PMIA) membrane as substrate. The effect of reaction conditions and the properties of substrates on performance of TFC NF membranes were investigated. The substrates and TFC NF membranes were characterized by field emission scanning electron microscope (FESEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscope (XPS) and contact angle goniometer, respectively. The PMIA TFC NF membrane showed an excellent thermal stability. The water flux of PMIA TFC NF membrane increased about three times while the rejection remained stable as the operating temperature increased from 25 °C to 90 °C. The PMIA TFC NF membrane exhibited a great potential application in the treatment of simulated textile wastewater. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) porous membranes are fabricated via thermally induced phase separation (TIPS) with mixed diluent (dibutyl phthalate (DBP)/dioctyl phthalate (DOP)). The effects of mixed diluent are discussed in detail in term of morphology, mean pore size, selective wettability, etc. The results show that the membrane structure changes from spherulitic to bicontinuous with the change of DBP/DOP ratio. It is also found that the degree of crystallization decreases with the decrease of DBP/DOP ratio in mixed diluent. When liquid--liquid (L-L) phase separation precedes solid--liquid (S-L) phase separation, the obtained membranes have outstanding hydrophobicity and lipophilicity, excellent mechanical property. Additionally, the PVDF-HFP hybrid membranes are prepared with silica (SiO2) particles and the effect of SiO2 content on structure and properties is discussed. It is found that the PVDF-HFP hybrid membrane with 2 wt % SiO2 (M3-S2) has better properties and higher filtration rate and separation efficiency for surfactant-stabilized water-in-oil emulsion separation. Moreover, the membrane M3-S2 also exhibits excellent antifouling performance for long-running. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) has attracted significant attention on account of its unique structure and superior performance, deriving a new research field for materials science. Herein, cellulose triacetate (CTA) flat-sheet RO composite membrane was fabricated with GO embedding in its layer via melting method, which exhibited higher permeate flux as compared to pristine CTA RO membrane. The morphologies and structural arrangements of the obtained composite membranes were analyzed by X-ray diffraction (XRD), Raman spectroscopy, Confocal scanning microscopy (CSM), and Scanning electron microscopy (SEM), respectively. It was found that thermogravimetric (TG) spectrograms revealed GO generating the degradation centres and changing degradation process with the increase addition of GO. Moreover, the mechanical property indicated that the incorporation of GO could contribute to the improvement of tensile strength from 10.2 MPa to 23.1 MPa because of the dominant interactions between C O groups from CTA and OH and COOH groups from GO. Finally, the RO membranes' performance showed that the permeate flux of membrane increased from 1.67 L·m − 2 ·h − 1 to 4.74 L·m − 2 ·h − 1 with the increasing GO content. However, the salt rejection compromised at the same time, perhaps due to the formation of channels which might offer the passageway of water accompanying by salt with the increasing GO content. [ABSTRACT FROM AUTHOR]

Superhydrophobic-superoleophilic poly(ethylene chlorotrifluoroethylene) (ECTFE)-SiO 2 hybrid porous membrane with hierarchical micro/nano-structural surface was successfully fabricated via thermally induced phase separation (TIPS) method using bis(2-ethylhexyl) adipate (DEHA) and diethyl phthalate (DEP) as binary diluent, hydrophobic SiO 2 as the additive. The effect of SiO 2 content on the morphology, pore size distribution, wettability and mechanical properties of prepared membrane was characterized by scanning electron microscope, automatic mercury porosimeter, contact angle goniometer and tensile testing instrument, respectively. The results showed that, the prepared hybrid membrane surface evolved into superoleophilic and superhydrophobic when the SiO 2 content was 4 wt%. The separation experiments for different kinds of surfactant-free and surfactant-stabilized water-in-oil emulsions indicated that prepared superhydrophobic-superoleophilic membrane had high oil/water separation efficiency. The antifouling performance of the membrane was also studied for reuse many times in various pH conditions. This study provided a novel material and a facile method to fabricate superhydrophobic-superoleophilic membrane. [ABSTRACT FROM AUTHOR]

This work focuses on the mass transfer in hydrophobic polyvinylidene fluoride (PVDF) and poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP) hollow fiber membranes, using a combination of experiments and computational fluid dynamics (CFD) model. Our experimental design considered a wider range of viscosity and surface tension for the feed solution (kerosene, lubricating oil and water), a larger span of operation temperature (25–85 °C), and longer usage time (8 h). The membranes were characterized for the permeability, morphologies, pore size distribution, porosity, water contact angle (WCA), roughness, differential scanning calorimetry (DSC) and tensile property. Numerical simulations of two-phase and single-phase flow in micron membrane channels were performed for several selected groups to assist interpretations of the experiments and to examine the effects of wettability, viscosity and pore size on the mass transfer process. The simulations base on the OpenFOAM-model agree well with the experimental results. Collectively, this study provides new insights regarding mass transfer in membrane channels and reference data for the use of fluoropolymers membranes for non-aqueous solution, especially high viscosity oil. [Display omitted] • 7.54 times of lubricating oil flux improvement of PVDF HFMs at 85 °C. • Quantified the effects of wettability, viscosity and pore size on mass transfer. • Showcased solution-membrane interaction: thermal expansion, swelling and extrusion. [ABSTRACT FROM AUTHOR]

Poly( p-phenylene terephthamide) (PPTA) hollow fiber membrane with outstanding thermal and chemical stability (endures above 60 °C and almost any organic solvents) has been fabricated by dry-wet spinning method for the first time. The heat and solvent resistance as well as anti-fouling performances was studied in this paper. The properties of thermal stability were characterized by pure water flux, mechanical strength, FTIR, and pore size distribution, and the properties of chemical resistance were characterized by organic solvent flux. The results showed that PPTA hollow fiber membrane was a kind of inner and outer dual-skin layer structure. The flux was stable in hot water and organic solvents, which indicated that the membrane structure hardly changed. The average pore size was slightly increased during high-temperature experiment. Moreover, the properties of anti-fouling were characterized by simulated activated sludge filtration. The fouled PPTA membranes were cleaned by ultrasonic, citric acid, and alkali treatments, and the membrane surface was detected by energy-dispersive X-ray spectroscopy. The results showed that the effect of the citric acid treatment was more preferable to the other ways, which indicated that the inorganic substance was easily adsorbed on the membrane surface compared with organic substance. Therefore, PPTA hollow fiber membrane exhibited the excellent anti-fouling performance by the reason of strong hydrophilicity and electronegativity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PVDF hollow fiber membrane with nanofibers and micro/nanospheres was prepared. • The micro/nanospheres were restricted by deposited nanofibers to prevent shedding. • Three-D micro/nano structure was adjusted by adding SiO 2 in electrospray solution. • The membrane had excellent mechanical property and oil-water separation property. The PVDF nanofibers and the PVDF/silica (SiO 2) micro/nanospheres were deposited simultaneously on the outer surface of a rotating PVDF braided tube by electrospinning and electrospraying to fabricate a new type of enhanced hollow fiber membrane. By adjusting the content of SiO 2 in electrospraying solution, the micro/nanospheres with different morphology were obtained to optimize the performance of the prepared membranes. When 2 wt% SiO 2 was added, the deposited micro/nanospheres mainly took loose porous PVDF aggregates as the skeleton and SiO 2 particles as the filler to construct the micro/nano structure on the membrane surface like that on the lotus leaf surface. Therefore, the membrane surface exhibited superoleophilicity (θ o = 0°) and underoil superhydrophobicity (θ uow = 154°). In addition, the deposited micro/nanospheres can effectively weakened the stacking between the deposited nanofibers. The resultant membrane not only had the high permeability with pure oil flux of 8557 L·m−2·h−1, but also possessed the excellent oil-water separation performance with separation efficiency of 99.70%. Meanwhile, it also showed the outstanding tensile strength of 79.40 MPa. The preparation method was simple and easy to operate, which would provide more possibilities for the preparation of hollow fiber membranes with efficient separation performance to the water-in-oil emulsion. [ABSTRACT FROM AUTHOR]

Poly(tetrafluoroethylene-co-hexafluoropropylene)(FEP) hydrophobic hollow fiber membranes were prepared through melt spinning method. The performances and structures of membrane samples with different stretching ratios were investigated. It can be seen that the increased stretching ratios (nascent, 50%, 100% and 150%) brought about obvious interfacial microvoids (IFMs) which improved the membrane's porosity, while decreased the liquid entry pressure (LEP) and mechanical strength. In addition, the FEP hollow fiber membranes exhibited strong hydrophobicity, excellent chemical and thermal stability owing to its perfluoro structure. Therefore, the performances of membrane samples were measured by vacuum membrane distillation (VMD) using alkaline aqueous with high temperature. The results showed that the FEP hollow fiber membranes' salt rejections achieved as high as 99.0%. In addition, the MD flux, salt rejection and mechanical strength kept stable in the strong alkaline aqueous (NaOH concentration of 300 g/L, 80 °C) through a long term operation of 48 h. However, the compared poly(vinylidenefluoride) (PVDF) hollow fiber membrane exhibited weak alkaline and thermal endurance with obvious decrease of mechanical strength and salt rejection. Therefore, this study indicated that the obtained FEP hollow fiber membrane could be used in the VMD which exhibited satisfying salt rejection. [ABSTRACT FROM AUTHOR]

A novel braid-reinforced (BR) cellulose acetate (CA) hollow fiber membrane consisting of separation layer and ‘hybrid’ braid was reported in this study. The ‘hybrid’ braid containing CA and polyacrylonitrile (PAN) fiber not only provided the membrane well interfacial bonding state but also overcame the negative effect of CA fiber׳s swelling on membrane permeability. The influences of braid composition and CA concentration on the structure and performance of BR CA membranes were investigated. There were two kinds of interfaces between the braid and the separation layer, which were named homogeneous-reinforced (HMR) interface and heterogeneous-reinforced (HTR) interface. Taking into account both interfacial bonding state and membrane permeability, the best ratio of the fibers in the braid was 2/1(CA/PAN). Increased CA concentration brought about reduced permeate flux and increased protein rejection. The BR CA membranes exhibited excellent anti-fouling property with flux recovery rates higher than 80%. The tensile strength of BR CA hollow fiber membranes varied from 16.0 MPa to 62.9 MPa by adjusting the braid composition. The BR CA membrane showed similar performance with the commercial hydrophilic polyvinylidene fluoride (PVDF) hollow fiber membrane during the filtration of milk solution, and the flux could be recovered by chemical cleaning. [ABSTRACT FROM AUTHOR]

Poly( p -phenylene terephthamide) (PPTA) hybrid porous membrane has been fabricated via a solution phase inversion method for the first time. The mixtures of PPTA/PEG/PVP/SiO 2 /H 2 SO 4 were used in this study. Membranes’ corresponding ultrafiltration performances were characterized in terms of pure water flux, porosity, contact angle, mechanical strength, thermogravimetric analysis (TGA), and rejection rate. The morphologies of PPTA hybrid porous membranes were observed by a field emission scanning electron microscope (FESEM). The results showed that the PPTA hybrid porous membrane was a kind of asymmetrical membrane. The dissolved pore-creating agents brought about the fibrillar micro-void structure on the lower surface. The performances of PPTA hybrid porous membrane were obviously affected by the addition of SiO 2 particles. It was found that the permeability, hydrophilicity, mechanical strength and rejection substantially increased with the promotion of the appropriate contents of SiO 2 . The rejection rate of ovalbumin reached more than 90%, while the oil/water emulsion reached more than 80%. What is more, the flux recovery ratio of them could also reach above 90%, which shows excellent anti-fouling property. [ABSTRACT FROM AUTHOR]

Polyvinyl chloride (PVC) matrix reinforced hollow fiber membranes including separation layer and porous supported matrix were fabricated via dry–wet spinning process. The mixtures of PVC or polyvinylidene fluoride (PVDF) polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by a melt-spinning method. The influences of pre-wetting solutions and polymer concentration on structure and performance of homogenous-reinforced (HMR) PVC hollow fiber membranes were investigated. Furthermore, the interfacial bonding state of HMR PVC hollow fiber membranes was characterized by an indirect method and comparative analysis. The results showed that a dense interface formed in the HMR PVC hollow fiber membrane between these two layers without pre-wetting process. Compared with the matrix membrane which had a rougher outer surface with obvious big pores, the prepared HMR PVC hollow fiber membrane possessed a dense and smooth outer surface with no obvious big pores. Due to the filling of the pre-wet solutions into the pores in the outer edge of the matrix membrane, the HMR PVC hollow fiber membranes formed porous interface in the coating process which improved its permeability. The HMR PVC hollow fiber membranes had a more favorable interfacial bonding than the heterogeneous-reinforced (HTR) PVDF hollow fiber membranes. The tensile strength of prepared PVC matrix reinforced hollow fiber membranes was higher than 12 MPa but lower than the original PVC hollow fiber matrix membrane. [ABSTRACT FROM AUTHOR]

The crystallization kinetics of polypropylene and poly (butyl methacrylate-co-hydroxyethyl methacrylate) blend was investigated with differential scanning calorimetry. The isothermal crystallization analysis based on the Avrami theory indicated a heterogeneous nucleating effect from the copolymer. A systematic study of the nonisothermal crystallization kinetics was undertaken using the Avrami equation and its later modifications by Ozawa, Mo, and Zhang. The results demonstrated that the linear relationship failed in the different cooling rates because the Avrami method did not take into account that the crystallization temperature was lowered continuously. The Ozawa and Mo methods could be successful in describing the overall nonisothermal process of polypropylene and the blend. In addition, the nonisothermal crystallization energy values were estimated by the Kissinger and Freidman models. There are two mutually opposite effects on the crystallization behavior of the blend: nucleation ability and growth retardation. [ABSTRACT FROM AUTHOR]

A series of blend fibers based on a certain weight polypropylene (PP) and poly(butyl methacrylate-co-hydroxyethyl methacrylate) (PBMA-co-HEMA) were prepared via melt spinning in a corotating twin screw extruder. The morphology and structure of the blend fiber was studied by stereoscopic microscopy, polarized optical microscopy, wide-angle x-ray diffraction and field emission scanning electronic microscopy. Thermal properties were carried out by means of differential scanning calorimetry and melt flow index. The results demonstrated that the crystalline structure is proven to be greatly destroyed owing to the entanglement and cross-linking of molecular chains caused by hydrogen bond network of the copolymer in the blend. Oil absorbency decreases with increasing mass fraction of PP in the blend fiber. Moreover, the enthalpy of crystallization and supercooling temperature decrease as the content of PBMA-co-HEMA component increases. [ABSTRACT FROM PUBLISHER]

Abstract: Homogeneous-reinforced (HR) polyvinyl chloride (PVC) hollow fiber membranes consisting of coating layer and matrix layer were fabricated via coating process. The mixtures of polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by melt-spinning method. The influences of PVC concentration and poly(ethylene glycol) (PEG) molecular weight in polymer solutions on structure and performance of HR membranes were investigated. The results showed that the HR PVC membranes had a dense and smooth outer surface compared with matrix membrane. The maximum pure water flux and protein permeation flux of HR PVC membranes were obtained as the PVC concentration reached to 10wt.% and PEG molecular weight was 2000. The increase of PVC concentration and PEG molecular weight brought about the increase of protein rejection rate and the decrease of membrane porosity. The high flux recovery rate (>85.00%) indicated that the HR membranes had excellent anti-fouling property. Moreover, the HR PVC membranes had a favorable interfacial bonding force between the coating layer and matrix membrane. The tensile strength of HR membranes decreased slightly compared with matrix membrane and was nearly 19MPa, but the elongation at break was opposite which was nearly 102%. [Copyright &y& Elsevier]

Abstract: Reinforced polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) hollow fiber membranes were prepared through dry–wet spinning process and included PVDF or PAN polymer solutions (coating layer) and matrix PVDF membrane. The performance of the membranes varies with different polymer solutions and is characterized in terms of ink solution and activated sludge flux, dynamic mechanical analysis (DMA), mean pore size, a mechanical strength test, and morphology observations by a scanning electron microscope (SEM). The results of this study indicate that PAN coating layer is easy to peel off from the matrix membrane. Interfacial bonding strength is also detected by dynamic mechanical analysis indirectly. The reinforced membranes show a narrower pore size distribution and smaller mean pore size than the matrix membrane. The elongation at break increases much more and the membranes are endowed with better flexibility performance. The homogeneous-reinforced (HMR) and heterogeneous-reinforced (HTR) membranes have a lower rate of flux decline compared with matrix membrane during ink solution filtration. The main types of all membranes fouling in microfiltration of ink solution were attributed to initial pore blocking followed by cake formation. Then, in the activated sludge solution, the reinforced membranes have stable efficiency in antifouling property for the real MBR system. [Copyright &y& Elsevier]

The homogeneous fiber-reinforced PVDF hollow fiber membrane was prepared successfully through dry-wet spinning process based on nonsolvent induced phase separation (NIPS) method. The three homogeneous fibers were evenly distributed in the separation layer (membrane matrix), and parallel to the axis of the membrane. The reinforcement mechanism was studied based on the change of structure and tensile properties of fibers before and after dry-wet spinning. The mechanical properties of the membrane reinforced by homogeneous fibers were improved significantly, which could meet the long-term use. Its breaking strength could reach 8.3 MPa, which was four times bigger than that of membrane without fiber reinforcement. And its pullout force could reach 4.48 N, which was sixteen times greater than that of polyester fiber-reinforced membrane. Meanwhile, its separation properties can still reach the level of the membrane without fiber reinforcement. In particular, the membranes properties could be adjusted by using the homogeneous fibers with different structures. • The PVDF hollow fiber membrane was reinforced by three homogeneous filaments. • The tensile and interfacial bonding properties of membrane were notably improved. • The reinforcement mechanism was studied by the change of fiber during spinning. • The properties of membrane could be adjusted by changing the structure of fiber. [ABSTRACT FROM AUTHOR]

Hydrophobic and oleophilic polymethacrylates with moderate crosslinking have been increasingly used for oil cleanup. In view of oil recovery and absorbent reusability, the particle-like polymethacrylates are not satisfied completely due to flaccid absorption and unfacilitated assembly. Fiber is now considered as an optimal candidate for oil absorbents. This review summarizes the most promising approaches to fabricate polymethacrylate fibers including post-crosslinking, low-crosslinking (physical crosslinking or entanglement), and blend, and then illustrates the structure-property relations of as-prepared materials. The resulting polymethacrylate fibers are effective oil-absorptive materials because of fast absorption, facility, reusability, and easy disposal, pointing to the immense potential for future development. [ABSTRACT FROM AUTHOR]

In this study, the melt-spinning and stretching processes were used to prepare polyvinylidene fluoride (PVDF)/polyacrylonitrile (PAN) blend hollow-fiber membranes. These blend membranes have a higher tensile strength than those prepared via the wet phase inversion method. The influence of stretching temperature and draw ratios on the membrane microstructure, pure water flux, and porosity of the membranes was studied. The draw ratio and the stretching temperature can greatly affect the morphology and the permeation performance of the membranes. The Fourier transform infrared spectra demonstrate the differences in the PVDF/PAN blend membranes before and after hydrolysis. The water flux of the hydrolyzed PVDF/PAN blend membranes is sensitive to pH value and salt ionic strength. The effects of different salt ions on the permeability of the hydrolyzed membranes were also investigated. [ABSTRACT FROM PUBLISHER]

Abstract: Polyurethane-based (PU-based) hollow fiber membranes were fabricated by melt-spinning method. The influence of hot-air treatment conditions including theoretical draw ratio, temperature and time on morphology and performance of membranes were investigated. The results showed that the maximum mean pore size and pure water flux were obtained as the theoretical draw ratio and treatment temperature reached to 2 and 70°C, respectively. The deformation-recovery was mainly governed by the treatment temperature in comparison with theoretical draw ratio when the membrane was treated in hot air. The least treatment time that obtained the best pure water flux was 30min. However, when the membrane treated in stress free conditions, the pore sizes on membrane outer surface were shrunk and the pure water flux decreased with the increment of heat treatment temperature. Moreover, a dense and smooth outer surface with thick skin layer formed as treatment temperature reached at 150°C. The PU-based hollow fiber membranes which treated at the optimum treatment conditions were used to the microfiltration test of the Direct Sky Blue 5B dye wastewater and the removal rate of Direct Sky Blue 5B particles was higher than 94.57%. [Copyright &y& Elsevier]

Abstract: Homogeneous-reinforced (HR) polyvinylidene fluoride (PVDF) hollow fiber membranes include PVDF polymer solutions (coating layer) and the matrix membrane prepared through the dry-wet spinning process. The performance of HR membranes varies with the polymer concentration in the polymer solutions and is characterized in terms of pure water flux, rejection of protein, porosity, infiltration property, a mechanical strength test, and morphology observations by a field emission scanning electron microscope (FESEM). The results of this study indicate that the tensile strength of the HR PVDF membranes decreases slights compared with that of the matrix membrane, but the elongation at break increases much more and the hollow fiber membranes are endowed with better flexibility performance. The HR PVDF hollow fiber membranes have a favorable interfacial bonding between the coating layer and the matrix membrane, as shown by FESEM. The infiltration property is characterized by the contact angle experiments. Pure water flux decreases while the rejection ratio with an increase in polymer concentration increasing. The protein solution flux of the HR PVDF membranes is higher than that of the matrix membrane after 100min of infiltration. [Copyright &y& Elsevier]

A series of polypropylene (PP)/poly (butyl methacrylate-co-hydroxyethyl methacrylate) (PBMA-co-HEMA) blend fibers were prepared by the melt-spinning method. The surface properties of the oil absorptive fibers were investigated for the first time by contact angle measurement in various liquids. The results indicate that as-prepared fibers, as a potential material for oil spill application, are both very hydrophilic and oleophilic. Surface energies were evaluated by the Zisman (28 kJ/m2 for surface energy of PP) and Owens-Wendt-Rabel-Kaelbel (28.9 and 0.3 kJ/m2 for dispersive and polar fraction of the 50-50 blend fiber, respectively) methods. A synergistic toughening effect between PP and PBMA-co-HEMA is presented by tensile measurement and micrographs. Dynamic mechanical analysis (DMA) measurements demonstrate the limited partial compatibility of the two polymers. Moreover, the storage modulus of the blend decreases with increase in copolymer content. [ABSTRACT FROM AUTHOR]

The functionalized copolymers, based on butyl methacrylate (BMA), and lauryl methacrylate (LMA) with crosslinking agent HEMA (hydroxyethyl methacrylate) or DVB (divinyl benzene), have been innovatively synthesized by suspension polymerization for oil absorption. Further, the copolymers and polypropylene (PP) blend fiber were attained via melt spinning. Swelling behaviors were evaluated by equilibrium swelling experiment, oil absorbency test, gel fraction measurement, and optical observations in toluene. The thermal properties and morphologies of the blend fibers were analyzed by thermogravimetry (TGA) and a field-emission scanning electron microscope, respectively. The results show that the copolymers and their blend fibers have an impressive absorbency. PBMA/LMA/HEMA can be up to 35.18 g/g, showing the highest absorption in trichloroethylene. Optical images of swollen polymers in toluene depicted a colloidal translucence with gel structure. Thermogravimetric measurement demonstrates that the copolymer and PP are incompatible and PBMA/LMA/DVB component possesses more thermal stability. The micrographs of the blend fibers exhibit coarse surface and porous cross-section, which leads to the fibers being much more readily wetted by oil and provides a huge space for oil storage. [ABSTRACT FROM AUTHOR]

Abstract: Polyurethane-based hollow fiber membrane was prepared by melt-spinning method. The object of this research was to study the fouling mechanism of this kind of membrane in microfiltration. Three materials (CaCO3, sodium alginate and humic acid) which could induce typical fouling were used as foulants. Results showed that cake layer formation by CaCO3 suspension was easier to be removed by backwashing; the difference between fouling mechanism of sodium alginate and humic acid was that the flux lost caused by humic acid was irreversible by backwashing for its hydrophobicity. Based on experimental data, an empirical formula for fouling mechanism was supplemented to improve the fitting result accuracy of the microfiltration processes of polyurethane-based membrane. [Copyright &y& Elsevier]

Butyl methacrylate-hydroxyethyl methacrylate (BMA-HEMA) copolymers were synthesized by the method of suspension polymerization. The copolymer fibers were prepared for absorbing liquid organic matter by gelation-spinning in a twin screw extrusion machine. The swelling parameters and mechanical properties were investigated, and the morphology was observed by scanning electron microscope (SEM). The results show that the degree of equilibrium swelling for the fibers increased with increasing the mass fraction of HEMA in the monomer feed when toluene, trichloroethylene, or chloroform were selected as organic absorbates. All of the interaction parameters, χ 1, for the fibers and organic liquids were less than 0.5, with the order of the interaction parameters χ 1 being as follows: toluene > trichloroethylene > chloroform. Average molecular weights between crosslink points, M c, and effective crosslink density, V e, were dependent on the selected organic liquids; for the different organic liquids, M c and V e were different. The breaking tenacity, initial modulus, and yield stress of the fibers increased with an increase in the mass fraction of HEMA. However, elongation at break and elongation at yield decreased with increasing the mass fraction of HEMA; in particular, for the mass fraction of HEMA equal to 15 wt%, the fiber did not yield, and underwent a brittle fracture. [ABSTRACT FROM PUBLISHER]

Abstract: A novel method was proposed to improve the hydrophilicity and permeation of poly (vinyl chloride)/polyacrylonitrile/SiO2 (PVC/PAN/SiO2) composite hollow fiber membranes (HFMs) by the interfacial hydrolysis of PAN between PVC and SiO2. PVC/PAN/SiO2 composite HFMs were prepared by phase inversion method, using water as inner and outer coagulation. Sodium hydroxide solution was fed to the composite HFMs to introduce hydrolysis reaction. The Fourier transform infrared spectroscopy (FTIR), bubble point pore diameter and scanning electron micrograph (SEM) were used to characterize the chemical, pore size and morphological changes of the membranes. The changes of permeation performance and mechanical properties were also investigated. Water contact angle (WCA) and protein filtration were employed to evaluate the hydrophilicity and the anti-fouling performance of the membranes. The alkaline hydrolysis occurred in the composite HFMs, both water permeation and the anti-fouling performance were improved while mechanical strength was still kept at a high level. [Copyright &y& Elsevier]

Functional fiber based on butyl methacrylate-hydroxyethyl methacrylate copolymer and low density polyethylene was prepared via the method of gelation-spinning, and then the kinetics model and mechanism of organic matter absorption into the functional fiber were investigated. The results show that a lot of microvoids are constructed within the cross section of the functional fiber, but the microvoids do not make a significant contribution to the absorption of organic matter. The functional fiber can absorb toluene at a quick rate, while it can absorb trichloroethylene and chloroform at a relatively slower rate. The swelling capability of the blend fiber in selected organic matter is weaker than the one of butyl methacrylate-hydroxyethyl methacrylate copolymer fiber, and the swelling behavior is controlled by stress relaxation in the amorphous portion of the polymer blend network. Furthermore, second-order kinetics model is more suitable for describing the process of organic matter absorption than first-order kinetics model. [ABSTRACT FROM AUTHOR]

Abstract: Polyurethane-based (PU-based) hollow fiber membranes were fabricated by melt-spinning method and then treated under different conditions to investigate the effects of post-treatment on their morphology and performance. The post-treatment included two processes, a water bath post-treatment for 48h at various temperatures and a dry air oven heat-treatment at 20°C for 48h. During the treatment process, membranes were treated at different draw ratios and their deformations were studied. Elastic deformation-recovery was associated with the treatment temperature and was affected slightly by draw ratio. For membranes treated in stress free conditions, pore size on the inner surface shrunk with increasing treatment temperature. Stretching could enlarge the mean and maximum pore size of membrane. The best water flux was obtained when the hollow fiber membranes were treated at 50°C, and the least treatment duration was 50min. Meanwhile, the extension ratio 3 was adopted as the optimal draw ratio. [Copyright &y& Elsevier]

Abstract: UHMWPE/PVDF/SiO2 hollow fiber membranes with a multi-pore structure were fabricated via thermally induced phase separation combining with stretching (TIPS-S). The preparation process utilized mineral oil as the diluent. A finite element calculation was used to predict generation of interface pores and the deformation of the polymer matrix. This approach enabled assumptions about phase separation and interface pore generation to be formulated. The formation and development of the interface pores were studied by scanning electron microscopy (SEM). Membrane performance was characterized by a variety of metrics including permeability, melting and crystallization behavior, porosity and pore diameter, and single-fiber tensile properties. The results indicated that the membrane evidenced a multi-pore-structure consisting of TIPS-generated pores, broken pores in the amorphous region, and interface pores formed by drawing. This complex pore structure enabled improved membrane permeability. These experimental results were in agreement with the assumptions obtained from the use of finite element analysis. [Copyright &y& Elsevier]

A series of polymers system based on poly(butyl methacrylate) (PBMA) and poly (hydroxyethyl methacrylate) semi-interpenetrating polymer networks (semi-IPN) (PBMA/ PHEMA = 70/30 by weight) have been attained by a sequential polymerization method using divinylbenzene (DVB) as cross-linking agent. Oil-absorptive fibers are prepared by wet-spinning processing. Oil absorbencies, swollen diameter variation, tensile strength, percentage elongation at break of the oil-absorptive fibers are reported. Crystalline structures have been estimated using wide angle X-ray diffraction (WXRD). Thermogravimetric analyzer (TGA), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC) are used to investigate thermal properties of oil-absorptive fibers. The results show that the cross-linking agent has a full impact on the properties of the oil-absorptive fiber. With an increase in DVB, oil absorbency can be improved, and the fiber shows many special phenomena including perfect cross-linking structure, excellent entanglement behaviors, good thermal stability and mediated crystalline temperature. However, glass transition temperature increases, and crystallization behavior becomes poor as increasing the cross-linking agent of DVB. [ABSTRACT FROM AUTHOR]

A novel absorptive fiber based on butyl methacrylate (BMA)-hydroxyethyl methacrylate (HEMA) copolymer and low density polyethylene (LDPE) was prepared by the method of gelation-spinning in twin screw extruding machine, swelling behavior, thermal behavior, crystallization behavior and nonisothermal crystallization kinetics were investigated, finally, the morphology structure for the cross-section was observed by SEM. The results show that the saturated absorbency for the blend fiber gradually decreases with increasing mass fraction of LDPE in mixture ratio from 10 wt% to 30 wt%. The results analyzed by DSC and WAXD show that crystallization and melting behaviors for the blend fiber are similar to those for pure LDPE fiber, and the crystallinity for the blend fiber decreases with decreasing mass fraction of LDPE. The results observed by SEM show that the cross-section for BMA-HEMA copolymer fiber shows a mono-phase structure with many cavities, as mass fraction of LDPE increases from 10 wt% to 30 wt%, the morphology structure with one continuous phase is transformed into another structure with two continuous phases, and the number of the cavities in the cross-section decreases, finally, the cross-section for LDPE fiber again shows a mono-phase structure without any cavities. [ABSTRACT FROM AUTHOR]

Abstract: Polycaprolactam (PA6) fibers were coated with polyaniline (PANI) by a novel dissolving-coating method. In the dissolving-coating method, dissolution of PA6 fiber surface is the necessary condition for imparting conductivity to PA6 fiber. But the dissolution of fiber surface would cause the structural integrity of PA6 fiber being destroyed. In this research, the effect of solvent concentration and roller speed on the mechanical and electrical properties of PANI-coated PA6 fiber were discussed. The results showed that the optimum condition for PANI-coated PA6 fiber is 75% formic acid aqueous solution and 100rpm. The coating durability of PANI was tested by TG, FT-IR, water washing and heating to different temperatures. The experimental data indicate that PANI coating is difficult to peel off after the heating and washing treatment. [Copyright &y& Elsevier]

Abstract: On principle of polymer blend phase separation, PVDF/PVA hollow fiber membranes were prepared using phase inversion method. The membrane morphology and performance varied with the blending ratio. The PVDF/PVA blends showed incompatibility by the results of dynamic mechanical analysis (DMA) and infrared attenuated total reflection (FTIR-ATR) sampling technique. Based on bursting pressure and tensile strengths results, we suggest that the mechanical properties of PVDF/PVA blend membranes are worse than that of PVDF membrane. PVA can improve the hydrophilicity of PVDF/PVA hollow fiber membranes, which could be illuminated by the decrease in contact angle, the increase in equilibrium water content (EWC) and the variety in dynamic moisture regain. The pure water flux increases while the rejection ratio decreases with PVA content increasing. Moreover, PVA can improve the anti-fouling property of PVDF/PVA hollow fiber membranes, which could be illuminated by the result of increase coefficient of resistance. [Copyright &y& Elsevier]

Abstract: The Ozawa and the modified Avrami models were usually used to describe the nonisothermal crystallization of polymers. A computer simulation approach was adopted to verify the two models. The results show that the Ozawa model is suitable under constant heating and cooling rate conditions, but not the modified Avrami model. Therefore, the Ozawa model was extended to acquiring the linear growth rate of polymer entities. A nonlinear relationship between the logarithm of the rate function and temperature was found. The values of the Avrami exponent are approximate to the designed value and the linear growth rates of the entities obtained are consistent with the designed ones. [Copyright &y& Elsevier]

Abstract: A polypiperazine amide (PA) composite membrane was prepared by interfacial polymerization using a trimesoyl hexane solution as the oil phase and a piperazine aqueous solution as the water phase on a polysulfone ultrafiltration substrate. The surface was inspected by attenuated total reflection–Fourier transform infrared spectroscopy, showing that a polyamide layer was formed. The molecular structure of polypiperazine amide was simulated using Materials Studio as a plane molecule with hexagon rings of 1.5 nm in diameter of the inscribed circle. Incorporating the result of wide angle X-ray diffraction pattern, the supermolecular structure of the PA was predicted as an irregular laminated structure. This model appears good according to the performance of the membrane. Also investigated was the morphology of the membrane by scanning electron microscope, showing a dense layer of 300 to 400 nm on the porous substrate. The composite membrane obtained is a high-performance nanofiltration membrane. [Copyright &y& Elsevier]

In this work, we developed a solvent-free and green route to prepare poly(vinylidene fluoride) (PVDF) hollow fiber membranes through melt-spinning and stretching (MS-S) technique based on the interface pore theory. The bisphenol A polysulfone (PSF) molecular chain contained the rigid aromatic rings, which was introduced into the PVDF melt for improving the interface layer between the matrix phase (PVDF) and the dispersed phase (PSF). Due to the poor compatibility of the two phases, the interface pore structure could occur and be controlled precisely through the further stretching. Interestingly, the pore size of the prepared membranes could be controlled from 0.172 to 0.550 μm by changing the stretching ratios. Applied to filter the SiO 2 and active sludge suspensions, the prepared membranes showed a high rejection (99.99%), and the turbidity decreased sharply (˂0.01 NTU). In addition, the obtained membranes exhibited outstanding mechanical properties, which could meet the long-term service demand. In particular, there were not any hazardous solvents used in the preparation process, which could achieve green preparation of PVDF membranes. Image 1 • PVDF membranes were fabricated via melt spinning and stretching (MS-S) process. • PSF was used as a rigid dispersed phase particle to promote higher porosity and flux. • Pores formed along the interface between dispersed and continuous phases. • Microfiltration pore size can be controlled by changing the stretching ratios. • MS-S is a "green" process that avoids use of toxic organic solvents. [ABSTRACT FROM AUTHOR]

In this work, polyvinylidene fluoride (PVDF) loose nanofiltration (NF) hollow fiber membranes with multilayer structure were prepared successfully based on a solvent-free process. Graphene oxide (GO) was used to cover the interface pores of the pristine PVDF membranes via vacuum filtration, and polypyrrole (PPy) was polymerized on the surface to further decorate the membrane structure. Interestingly, the modified membranes exhibited a multilayer structure due to synergistic effect of GO and PPy. The structure and property of PVDF loose NF membranes were investigated in detail. After modifying by GO and PPy, the hydrophilicity improved obviously. Moreover, the molecular weight cut off (MWCO) was about 3580 Da, and the smallest pore size of skin layer decreased to 2.5–4 nm. Furthermore, the PVDF loose NF hollow fiber membranes presented a high dye rejection (˃98.5%) for negative dyes, whereas a low salt rejection for NaCl (about 4%), showing a great potential for separating dye/salt accurately. Specifically, there were not any solvent used in all the preparation processes. The work offered a novel strategy for green preparation of loose NF membranes. Unlabelled Image • We offered a green route to prepare PVDF loose NF hollow fiber membranes. • There were not any solvent used in all the preparation steps. • The prepared membranes showed a high dye rejection (˃98.5%) for negative dyes. [ABSTRACT FROM AUTHOR]

• Hollow fiber membrane technologies have historically received widespread attention. • The integration of green process with sustainable fabrication methods is attractive. • Widely discussed recent progress of hollow fiber membranes on preparation technology. • This review proposes the recommendations for future research and development. Membrane separation using hollow fiber membrane has become one of the emerging technologies which underwent rapid development for various applications during the past few decades. A further improvement and development of the membrane technology is required for satisfying the current needs of environmental protection, rational use of resources and special separation under harsh conditions. A new solvent-free or solvent-poor process alternative may have great potential to compete with traditional processes. In this regard, sustainable processes and environment-friendly preparation techniques have been developed in making high-performance hollow fiber membranes recently. This article provides an overview of recent progresses on common preparation method of polymeric hollow fiber membranes from the view of environmental protection and health safety. Recent advances in fabrication techniques of hollow fiber membranes from the green and sustainable perspective, especially by melt/solution integrated homogeneous-reinforcement method, homogeneous braid reinforced hollow fiber membrane, melt spinning-stretching interfacial phase separation method, and nanofibers-covered hollow fiber membrane via continuous electrospinning have been introduced in detail. The review ends with several recommendations for future research and development on hollow fiber membranes. [ABSTRACT FROM AUTHOR]

• GPNM was simply fabricated avoiding multistep-reaction or post-treatment. • The embedded GE is of great importance for enhancing the permeability of GPNM. • GPNM can effectively separate various water-in-oil emulsions along with high flux. • GPNM can selectively absorb a series of oils with the Q value of 10–25 g/g. Highly efficient separation of emulsified oily wastewater, especially for surfactant-stabilized water-in-oil emulsions is urgently demanded and still worldwide challenge. Herein, a superoleophilic and under oil superhydrophobic Poly (vinylidene fluoride) (PVDF)/graphene (GE) composite nanofibrous membrane (GPNM) was fabricated through a simple one-step electrospinning strategy for highly efficient gravity-driven surfactant-stabilized water-in-oil emulsions separation. The resultant membrane possessed water contact angel of 140.1°±1.1°, oil contact angel of nearly 0°, as well as under oil ultralow water adhesion ability. Furthermore, the morphology, pore size and surface wettability of as-prepared nanofibrous membranes were simply tuned by adjusting the concentration of GE in electrospinning solution. Thanks to the narrow pore size distribution, high porosity (＞92.8%), and the intrinsic strong oil affinity of GE nanosheet, the composite membrane showed outstanding Span 80 surfactant-stabilized water-in-oil emulsions separation efficiency as high as 99.8% with corresponding permeation flux up to 23794 ± 928 L m−2 h−1 bar−1 during gravity-driven separation process. The exceptional oil absorption performance was also displayed by collecting floated oils on water surface. The results would make our composite nanofibrous membranes a great promise of dealing with practical oily wastewater remediation. [ABSTRACT FROM AUTHOR]

• We offered a completely green route to fabricate PVDF hollow fiber membranes. • The produced wastewater was treated and recycled to achieve sustainable development. • The prepared PVDF hollow fiber membranes showed switchable pore size. In this work, the poly(vinylidene fluoride) (PVDF) hollow fiber membranes with switchable pore size were fabricated by melt-spinning and stretching (MS–S) process based on a completely green and sustainable route. The membrane preparation process and pore formation mechanism were discussed and investigated in detail. Meanwhile, the effect of stretching ratio on the membrane structure and property was studied based on scanning electron microscopy (SEM), pore size distribution, N 2 flux, pure water flux, mechanical property and so on. The prepared membranes with different stretching ratios exhibited excellent tensile strength in the range from 23.0 to 62.6 MPa. The mean pore size of the prepared membranes with stretching 100 % (M-100) was about 0.317 μm, which showed a high dye rejection (<93.9 %) for Direct Black 19. Specifically, there were not any organic solvent and low-molecular-weight diluent used during the preparation process. The recycled PEO and water were obtained after treating the wastewater by membrane filtration. In addition, the recycled PEO could be reused as pore forming agent, which could achieve completely green and sustainable membrane preparation process. [ABSTRACT FROM AUTHOR]

In this study, a novel and multifunctional polyvinylidene fluoride-co-hexafluoropropyle (PVDF-HFP)/catechol-polyethyleneimine (CA-PEI)/Ag/3-glycidyloxy propyltrimethoxysilane (KH560) tubular nanofiber membrane (TNM) for applications in dye degradation and oil/water separation was fabricated. Firstly, the PVDF-HFP tubular nanofiber membranes were modified by using a mussel-inspired method. Then, Ag nanoparticles were assembled on the nanofiber surface to improve their excellent catalytic capacity for Methylene blue (MB) and Congo red (CR). Finally, the hydrophilic KH560 was grafted on nanofiber surface and the effects of KH560 concentration on the membrane performance were investigated. The results showed that when the KH560 concentration was 3 wt%, the modified membranes possessed a higher hydrophilicity and permeability. Meanwhile, it could also effectively separate various oil-in-water emulsions with high separation rate and separation efficiency at 0.02 MPa. Moreover, the catalytic and oil/water separation performances had no discernible decay after ten cycle tests, which promoted the potential application of modified PVDF-HFP TNMs for the treatment of practical oily wastewater. • Hydrophilicity and underwater superoleophobicity. • Excellent catalytic capacity and separation performances. • Dye degradation and oil/water separation. [ABSTRACT FROM AUTHOR]

Developing a reusable and durable catalyst for heterogeneous photo-Fenton process is of great importance for the practical application in the environment remediation. In this study, poly(vinyl alcohol) (PVA)/sodium alginate (SA) hydrogel beads were constructed using FeCl3 and boric acid as cross-linking agents. Characterizations and tests were employed to investigate the structure, optical property and durability of the obtained beads. The photo-Fenton performance of the PVA/SA-FeCl3 beads was evaluated by degradation of tetracycline (TC) under visible-light irradiation. The results show that the constructed beads exhibit porous structure, display a broad absorption band in the visible region and behave excellent stability against mechanic effects. The photocatalytic experiment result indicates that the removal rate of TC reaches 90.5% under optimized conditions, while the removal rate of total organic carbon reaches 28.6%. By analyzing the degradation of TC after adding active species scavengers, a photocatalytic mechanism was proposed. Moreover, PVA/SA-6% FeCl3 beads could be easily separated and recycled in water purification. This work provides a facile and robust method to construct reusable and durable Fe(III)-containing hydrogel beads with acceptable photo-Fenton catalytic performance under visible-light irradiation, paving the way for its practical application in wastewater treatment. [ABSTRACT FROM AUTHOR]

The photocatalysis for environment purification and clean energy production has attracted widespread attention, however, traditional powder-form photocatalysts cannot meet the practical application due to their poor recyclability, especially in slurry system. Here, polypyrrole/cadmium sulfide/nickel (PPy/CdS/Ni) multi-layer hollow fibrous photocatalyst with favorable photocatalytic activity for pollutants removal and hydrogen (H 2) evolution was successfully fabricated, which possesses a narrow band gap of ∼1.87 eV and enhanced visible-light photocatalytic activity. The removal efficiency of methylene blue (MB) and tetracycline can reach up to ∼94.76% and ∼76.1%, respectively. Simultaneously, the TOC removal efficiency with regard to MB can reach up to 78.1% and Cd2+ leakage is extremely low (<3 mg⋅L−1). More interestingly, H 2 evolution rate of PPy/CdS/Ni hollow fiber is up to as high as 665.7 μmol⋅g−1⋅h−1, which is about 1.43 and 1.86 folds higher than the PPy/CdS/Ni/PET fiber (466.3 μmol⋅g−1⋅h−1) and CdS/Ni/PET fiber (357.1 μmol⋅g−1⋅h−1), respectively. As a fiber-form intrinsic photocatalyst, our catalytic fiber shows great promise for pollutants removal and hydrogen energy production due to its easy-handling and recyclement. [Display omitted] • A novel PPy/CdS/Ni hollow fiber with photocatalytic activity was synthesized. • Pollutant removal efficiency and H 2 evolution rate are appreciable. • Possible photocatalytic mechanism was proposed. • PPy/CdS/Ni hollow fiber shows good photocatalytic stability and recyclability. [ABSTRACT FROM AUTHOR]