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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.

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.

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.

Magnetic Fe3O4/graphene oxide (GO) composite particles with excellent properties of magnetic susceptibility and hydrophilicity were synthesized by a facile one-step chemical coprecipitation method. Then the prepared magnetic Fe3O4/graphene oxide (MGO) particles were introduced to polyvinylidene fluoride (PVDF) casting solution to fabricated PVDF/MGO hybrid membrane under the magnetic field. The directional migration and ordered arrangement of MGO sheets in magnetic field were investigated. The preparation of multilayer composite membrane was in the form of functional layer and support substrate in series, in which the functional layer with MGO orderly embedded into the membrane surface was prepared via magnetic field induced MGO sheets to the membrane surface during the phase inversion process. There was obvious effects of this novel structure on the pure water flux, hydrophilicity and antifouling properties of the membranes. The PVDF/MGO membranes showed high pure water flux (484 L m−2 h−1) and high flux recovery ratio (up to 83.0%).

Superhydrophobic-superoleophilic poly(ethylene chlorotrifluoroethylene) (ECTFE)-SiO2 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 SiO2 as the additive. The effect of SiO2 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 SiO2 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.

A novel tubular polyvinyl chloride (PVC) hybrid nanofiber membrane with three-dimensional structure interwoven by three-dimensional microspheres and two-dimensional nanofibers was fabricated via electrospinning process, with the polyester (PET) hollow braided tube as the support and hydrophobic nano silica (SiO2) as the inorganic additive. The fabricating strategy was designed as the double-needle electrospinning methods with two-component in respective needles. The synergistic effect of two-dimensional nanofibers interwoven with three-dimensional microspheres endowed the three-dimensional nanofiber membrane with the continuous water-oil-solid interfaces, which slowed down the water wetting process and improved the hydrophobic stability of the membrane. With high porosity and multistage rough structures, the three-dimensional nanofiber membrane could be used as an efficient liquid separation membrane, which had excellent separation efficiency for various surfactant-stabilized water-in-oil emulsions separation without external force. When the SiO2 content reached to 4 wt%, the membrane revealed excellent lipophilicity and superhydrophobicity under oil. Moreover, it produced a high permeation flux up to 358.60 L/m2.h with outstanding separation efficiency more than 95% under the driving of gravity, and the excellent reuse performance in water-in-oil emulsion. In addition, the three-dimensional tubular nanofiber membranes prepared by this method have high porosity, excellent mechanical properties, good thermal stability and hydrophobic stability. This simple, economical and environmentally friendly method provided a convenient and cheap platform for the field of waste oil containing water remediation.

New-style thin film composite nanofiltration (TFC NF) membrane with a stripe-like surface structure, superior interfacial bonding, expected permeability and antifouling performance was successfully fabricated via interfacial polymerization. The aminated polyvinyl chloride (APVC) membrane prepared by amination reaction of polyvinyl chloride (PVC) with triethylenetetramine (TETA) was used as the support layer. The new graphene oxide-polyamide (GO-PA) selective layer was formed by adding graphene oxide (GO) to the aqueous solution to participate in the interfacial polymerization process. The effects of amination modification of PVC substrate membrane and addition of GO during the interfacial polymerization on the structure and performances of the TFC NF membranes were studied. The results indicated that both of the amine group on the surface of the APVC membrane and GO participated in the interfacial polymerization, which endowed the GO-PA/APVC membrane with a new-style stripe-like surface structure and a thicker, gradually looser cross-sectional structure. Meanwhile, the effective desalination active layer of the GO-PA/APVC membrane was much thinner than that of the PA/APVC membrane. The special structure was beneficial to accelerate the speed of water transmission and effectively overcome the trade-off effect during the desalination process. Therefore, the water permeability of GO-PA/APVC membrane was improved more than 60% while the salt rejection remained stable compared with PA/APVC membrane. Moreover, the GO-PA/APVC membrane exhibited superior interfacial bonding and antifouling properties.

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.

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.

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.

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 30 min. 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%.