Dry-wet Spinning Technique Research Articles

Preparation of photothermal alginate/chitosan derivative/CuS@polydopamine composite fibers and application in desalination

A polyelectrolyte system consisting of sodium alginate (SA) and quaternary ammonium chitosan (QAC) blended with polydopamine-coated copper sulfide particles (CuS@PDA) was chosen to investigate the function of CuS@PDA in the uniform binary blending of anionic and cationic polyelectrolytes in detail. A smart composite fiber SA/QAC/CuS@PDA was prepared via a dry-wet spinning technique. With the addition of CuS@PDA (about 4.3 % in fiber), the as-prepared SA/QAC/CuS@PDA-0.50 fibers (SQCuS@P-0.50 SCFs) showed notably enhanced intensity 359.2 MPa, excellent moisture response, and photothermal conversion performance, with the temperature increasing from 25.9 to 80.7 °C as irradiated under a 980 nm infrared lamp at distance 20 cm away for 120 s. The photothermal performance was maintained after 6 lighting on-and-off cycles. The tensile strength decreased ~23.8 % after 4 cycles, then remained fixed. The diameter increases to ~480 % in wet state but decreases to the original size in dry state for 10 cycles. When the fabric with 90 wt% SQCuS@P-0.50 SCFs was used as a water evaporator, the water evaporation rate and efficiency were 1.68 kg·m−2·h−1 and 102 % under 1 sun irradiation. This work provides a simple and ecofriendly strategy for fabricating photothermal fabrics by designing and preparing composite fibers.

Enhanced water permeability of hollow fiber composite reverse osmosis membrane using porous α-cellulose/polysulfone hollow fiber membrane as the substrate

The hollow fiber composite (HFC) reverse osmosis (RO) membrane with a special self-supporting structure has attracted a great deal of attention in the fields of separation and purification. However, low permeability is an urgent problem restricting its wide application. A porous polysulfone (PSF) hollow fiber support membrane was fabricated through the dry–wet spinning technique and hydrophilic α-cellulose © powder was incorporated in the PSF membrane matrix to improve the membrane’s water permeability. The HFC RO membrane was prepared via the interfacial polymerization process on the inner surface of the C/PSF support membrane. The membrane morphology and surface hydrophilicity were evaluated through scanning electron microscopy observation and dynamic water contact angle (WCA) measurement. The effects of α-cellulose incorporation on the separation performance of PSF hollow fiber membranes and HFC RO membranes were investigated. The results showed that the surface hydrophilicity and water permeability of the PSF membrane were significantly improved after the introduction of α-cellulose. The WCA of the modified PSF support membrane decreased from 84.6° for the neat PSF membrane to 70.25°, and the pure water flux can reach a maximum value of 102.1 L/(m2 · h) (0.1 Mpa), which was 1.3 times that of the pristine membrane. The HFC RO membrane using the hydrophilic modified PSF membrane as the substrate exhibited an enhanced water flux of 15.6 L/(m2 · h) and, meanwhile, the membrane salt rejection remained above 97.6% (1.0 wt% NaCl aqueous solution, 0.7 Mpa). The HFC RO membrane showed extremely high rejection rates (99%) for different dyes (congo red and methylene blue). No obvious performance deterioration was observed for the HFC RO membrane during continuous vacuum membrane distillation (VMD) experiments for 60 h.

Fabrication of NH2-MIL-125 (Ti)/Polyvinylidene fluoride hollow fiber mixed matrix membranes for removal of environmentally hazardous CO2 gas

Improper pairing of filler and polymer together with inappropriate filler loadings into polymer matrix may lead to structural defects such as large aggregations and interface void formations. Subsequently, the structural defects may sacrifice the selectivity of CO2 over CH4, which was unfavorable. In the current work, NH2-MIL-125 (Ti) (MIL = Material Institute Lavoisier), which possesses NH2-groups and theoretically capable of forming strong hydrogen bonding with F-groups of polyvinylidene fluoride (PVDF), was selected to spin hollow fiber mixed matrix membranes (HFMMMs). Besides, NH2-MIL-125 (Ti) can interact better with CO2 over CH4 via quadrupole moment, and NH2-groups also aid in CO2 selectivity due to its high CO2 adsorption capability. The HFMMMs were spun using a dry-wet spinning technique of filler loadings percentage ranging from 1 to 3 wt percent (wt%). The effect of filler and loadings percentage over HFMMMs properties, including contact angle, mechanical strength, thermal stability and cross-sectional morphology was investigated. The compatibility at interface of filler and polymer was observed to be good, and dispersion was observed to be acceptable up to 2 wt% filler loadings. However, apparent aggregation was observed beyond this point. The wt% of Ti, O, and N elements were found to increase from 0.72 to 2.05, 3.27 to 4.53, and 0.52 to 1.55, respectively, with increasing filler loading into HFMMMs. Subsequently, PVDF-2 membrane displayed the highest CO2/CH4 ideal selectivity with contact angle of 83.44 ± 1.45, ultimate tensile strength (UTS) of 1.33, 29.12 Young's Modulus, and 72.2% elongation at break. Therefore, optimizing loading percentage and selecting appropriate filler are considered practical methods to ensure good morphology and better hazardous CO2 removal.

In-situ compatibilized starch/polyacylonitrile composite fiber fabricated via dry-wet spinning technique

An in-situ compatibilized starch (St) and polyacrylonitrile (PAN) composite spinning solution was designed by preparing starch-graft-polyacrylonitrile (St-g-PAN) through graft copolymerizing acrylonitrile from soluble starch and using ammonium cerium nitrate (CAN) as initiator. As dimethyl sulfoxide (DMSO) was used as the solvent, St/St-g-PAN/PAN/DMSO spinning solution was prepared and St/St-g-PAN/PAN composite fibers were obtained by dry-wet spinning technique. The effects of air gap, coagulation bath, hot drawing and stretching, and thermal-setting process were studied in detail. Fourier transform infrared spectroscopy (FT-IR), solid state nuclear magnetic resonance (13C NMR), thermogravimetric analysis (TGA), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM) were used to characterize the structure and morphology of the copolymer and the fibers. Single fiber strength tester and sonic orientation instrument were performed to measure the fiber mechanical properties and orientation degrees. The results showed that as the grafting ratio ~150.0% and the reacting mixture containing St ~9.8%, St-g-PAN ~81.6%, and homo-PAN ~8.6% in DMSO solution with 6.0 wt% in concentration were used, the spinning parameters such as air gap ~35 mm, coagulation bath concentration ~70%, temperature ~25 °C, and positive stretching ~48%, hot drawing and stretching 6 times at 80 °C, thermal-setting at 90 °C for 3 h under constant length mode were met, composite fibers with breaking strength 3.41 cN·dtex−1, breaking elongation 14.41%, sonic orientation factor 0.625, moisture recovery ratio 10.53% under standard condition (1 atm, 22 °C, and relative humidity 65%), and boiling water shrinkage ratio 9.60% were obtained. The as prepared composite fiber was better than common viscose fiber 2.11 cN·dtex−1 and cotton fiber ~3.24 cN·dtex−1 and expected to be used in the fields of medical gauze, bandage, protective clothing, et al. besides of common textiles. The in-situ compatibilization method can be applied in preparation of other composite polymer materials.

New mixed matrix membrane for the removal of urea from dialysate solution

Urea removal is one of the biggest challenges in dialysate regeneration in Wearable Artificial Kidney (WAK) devices. In this work, a new Mixed Matrix Membrane (MMM) is developed for urea removal in WAK applications. The MMM consists of polystyrene-based ninhydrin particles within a polyethersulfone/polyvinylpyrrolidone polymer blend matrix. The MMM is prepared via dry-wet spinning technique and characterized in terms of its morphology via electron microscopy and clean water permeance. Urea removal is studied both in static and in dynamic conditions. Thanks to the good dispersion of small size ninhydrin particles (size < 63 µm), the MMM removed under static conditions, at 70 °C, 2.1 ± 0.1 mmol of urea per grams of particles at 24 h, while urea removal by the particles in suspension reached 1.7 ± 0.1 mmol/g under the same conditions. Importantly, in continuous recirculation experiments, performed at 70 °C using a laboratory scale module, the MMM removed 3.4 ± 0.3 mmol of urea per grams of particles, in 4 h, due to the high particle accessibility by urea within the membrane. Based on these results it is estimated that only 215 g of MMM are needed for removing the daily produced urea from spent dialysate (400 mmol) making MMM suitable for application to WAK, where miniaturization and lightweight are required.

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.

Highly Permeable Mixed Matrix Hollow Fiber Membrane as a Latent Route for Hydrogen Purification from Hydrocarbons/Carbon Dioxide.

This work reported on the fabrication and investigation of a mixed matrix hollow fiber membrane (MMHFM) by incorporating commercially available alumina particles into a polyetherimide (PEI) polymer matrix. These MMHFMs were prepared by the dry-wet spinning technique. Accordingly, optimizing the spinning parameters, including the air gap distance and flow rate ratio, is key to determining the gas separation performance. However, there are few studies regarding the effect of the filler dimensions. Consequently, three sizes of alumina particles, 20 nm, 30 nm, and 1000 nm, were respectively added into the PEI phase to examine the influence of filler size on gas permeation property. Moreover, the permeation properties of lower hydrocarbons (i.e., ethane and propane) were also measured to evaluate potential for emerging applications. The results indicated the as-synthesized membrane exhibited a remarkable hydrogen permeance of 1065.24 GPU, and relatively high separation factors of 4.53, 5.77, and 5.39 for H2/CO2, H2/C2H6, and H2/C3H8, respectively. This resulted from good compatibility between the larger fillers and the PEI polymer, as well as a reduction in the finger-like voids. Overall, the MMHFM in this work was deemed to be a promising candidate to separate hydrogen from gas streams, based on the comparison of the separation performance against other reported studies.

Experimental and Numerical Study of CO2/CH4 Separation Using SAPO-34/PES Hollow Fiber Membrane

The poor compatibility between polymeric matrix and inorganic filler in mixed matrix membrane (MMM) generates interfacial defects that reduce the gas selectivity. In this work, the defects in poletherysulfone (PES)/silicoaluminophosphate (SAPO)-34 zeolite mixed matrix membrane was prepared by dry–wet spinning technique for the separation of CO2/CH4 mixtures. In this regard, the synthesized PES/SAPO-34 mixed matrix membranes (MMMs) were characterized via FESEM, TGA and DSC analyses. The response surface methodology (RSM) was applied to find the relationships between several explanatory variables such as air gap distance, jet strech ratio and zeolite content and CO2 permeance as responses. The results were validated with the experimental data, which the model results were in good agreement with the available experimental data. The effects of feed temperature and feed pressure on permeation and CO2/CH4 selectivity of membranes were investigated. The MMMs showed better performance than the neat PES membrane. Two dimensional countercurrent mathematical model for membrane separation has been incorporated with Aspen HYSYS as a user defined unit operation in order to optimize and design the membrane system for CO2 capture from natural gas. Parameter sensitivities, along with process economics, have been studied for different design configurations (including recycle streams and multiple stages). It has been observed that double stage with permeate recycle system gives the optimum design configuration due to minimum process gas cost involved with it. Permeation results manifested that the PES/SAPO-34 fabricated at optimum conditions has incredible worth from the prospective of industrial separations of CO2 from flue and natural gas.

Influence of Particle Size on the Structure and Properties of 316L Hollow Fiber Membranes Sintered Under Argon Atmosphere

316L based stainless steel hollow fiber membranes (HFs) are used as an alternative for polymer and ceramic based membranes. Application areas of 316L hollow fiber membranes are applications such as support or particle filter of gas and liquid separations in chemical and waste treatment industries. Among various methods, dry-wet spinning technique was selected as the production method of hollow fiber membranes since it is the most popular one. The aim of the study is to produce hollow fiber membranes in different powder particle sizes (coarse, fine, and their mixture), and to examine their structure and also their properties such as chemical compositions, pore amount, average pore size, and pore distribution. 3-point bending tests were also used to determine their mechanical properties. HFs produced from fine particles show higher densification than coarse particle size samples. In terms of pore structure, mixed particle size yields lower porosity and pore size than the finest particle size. On the other hand, the finest particle size yields the highest bending strength and bending deflection.

Study on the effect of air gap on physico-chemical and performance of PVDF hollow fibre membrane

Polyvinylidene fluoride (PVDF) was chosen in this study as the main material in fabricating membrane due to its excellent chemical resistance and good thermal stability. Combination of triethyl phosphate (TEP) with DMAc produce better structure of membrane which safer and provide high mechanical strength for membrane. Surface modified PVDF hollow fibre membrane (HFM) was prepared using dry-wet spinning technique by varying air gap namely 10 cm, 20 cm and 30 cm. The morphology was evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM), mercury intrusion porosimetry (MIP), contact angle, tensile test and performing water flux testing. From the characterization data, PVDF HFM with 3 wt.% PEG 400, HFM 3-10 and HFM 3-20 referred as microfiltration membrane with pore size range 0.1-0.8 µm. While, HFM 3-30 act as ultrafiltration membrane with pore size ranging 0.01-0.1 µm. Experimental results revealed that by increasing the air gap from 10 cm to 30 cm, the porosity and finger-like length decreased due to the higher elongational stress that shift the pores from broad to narrow. Thus, PVDF HFM at 10 cm air gap, HFM 3-10 achieve the highest water flux due to the higher porosity, longer finger-like length and hydrophilicity achieved. The modified HFM at shorter air gap was found to be a promising membrane structure for excellence water performance and eco-friendly to environment.

Effects of spinning conditions on structure and properties of aramid-based hollow fiber blend separation membranes

The rigid-rod-like poly(p-phenylene terephthalamide) (PPTA), as the raw material of aramid 1414, has the characteristics of high modulus and hydrophilicity. The flat sheet poly(vinylidene fluoride) (PVDF)/PPTA blend separation membranes with improved hydrophilicity and enhanced modulus have been successfully prepared using in situ polycondensation method in our previous study. In this study, PPTA/PVDF hollow fiber blend separation membranes with enhanced hydrophilicity and mechanical strength were fabricated through the dry–wet spinning technique. Monomers of PPTA were polymerized in the PVDF solution, and the polymerization system was directly used as the spinning solution to fabricate the hollow fiber blend membrane. The effects of spinning conditions including the air-gap distance; the composition of core fluid; and composition of coagulation bath on the structure and properties including the separation properties, surface hydrophilicity, and mechanical properties of PPTA/PVDF hollow fiber blend membranes were well investigated. Membrane surface and cross-sectional morphologies were observed through scanning electron microscope. The enhancements of these spinning conditions weakened the phase separation process as a result of the formation of a small pore structure. The pore size distribution, water flux, and solute rejection varied accordingly. Different spinning conditions have different effects on the mechanical and hydrophilic properties of the hollow fiber blend membranes. Compared with pure PVDF hollow fiber membrane, blend membranes fabricated under different spinning conditions exhibited enhanced surface hydrophilicity and tensile properties. Finally, the change rates of the pure water flux and the solute rejection with different spinning conditions were calculated to further analyze and compare the statistically significant effects.

INCORPORATION OF IMPRINTED-ZEOLITE TO POLYETHERSULFONE/CELLULOSE ACETATE MEMBRANE FOR CREATININE REMOVAL IN HEMODIALYSIS TREATMENT

Polyethersulfon (PES) membrane has been widely used in the biomedical field especially in hemodialysis application. Many modifications of membranes have been applied into hemodialysis such as diffusion, adsorption, and mixed-matrix membrane. The main problem of those membranes is less selectivity to attract the uremic toxins. In this study, we report the modification of PES mixed with cellulose acetate (PES/CA) membrane as mixed-matrix membrane (MMM) using imprinted-zeolite (PES/CA/IZC) in order to increase the selectivity for targeted analyte. The hollow fibre membranes (HFM) were fabricated by dry-wet spinning technique. The successful zeolite A synthesised and was characterised by x-ray diffraction (XRD). The mixed-matrix membranes were characterised in terms of morphology using scanning electron microscopy (SEM), water contact angle (WCA), pure water flux (PWF), clearance of creatinine (CC), and BSA adsorption. In accordance with the results of characterisation, the synthesis of zeolite A, and imprinted-zeolite creatinine was successfully fabricated. The SEM results showed that the PES/CA/IZC membrane has uniform pores and fingerlike structure. The same result was obtained for PES/CA membrane, but not for PES/CA/ZA membrane. The WCA of the PES/CA; PES/CA/ZA; and PES/CA/IZC were 85.63; 84.98; and 77.53 (o), respectively. While the PWF were 22.84; 27.57, and 40.52 (Lm-2h-1), respectively. The addition of imprinted-zeolite into the membrane improved creatinine removal up to 74.99%. It showed that PES/CA/IZC has succeeded in increasing the selectivity of membranes to attract the creatinine as target analyte. Compared to the PES/CA, the creatinine clearance of membranes improved and increased up to 5.2%. For protein rejection, the PES/CA/IZC rejected 79.05% of bovine serum albumin (BSA). Based on these results, it can be concluded that PES/CA/IZC can be considered as hemodialysis membranes.

Nickel hollow fiber membranes for hydrogen separation from reformate gases and water gas shift reactions operated at high temperatures

High temperature H2-selective membranes can be applied as the membrane reactor for pure hydrogen production by catalytic reforming of alcohols or hydrocarbons. Conventional Pd-based membranes are limited for this purpose due to the low thermal stability, significant hydrogen embrittlement, quick poisoning by other impurity species and high material cost. In this work, metallic nickel (Ni) hollow fiber membranes with thin wall thickness and optimal microstructure were fabricated by the dry-wet spinning and sintering technique, and employed for H2 separation from the model reformate mixtures containing CO2, CO, H2O and H2S at elevated temperatures up to 1000 °C. The prepared Ni hollow fiber membranes possess 100% H2-permselectivity, only allowing for the hydrogen in the reformate mixtures to permeate through under experimental conditions. In the presence of CO, CO2 and H2O (vapor), the hydrogen recovery from reformate mixtures may be noticeably influenced due to the water gas shift reaction (WGS: CO + H2O ↔ CO2 +H2). Multiple cycling operation and long-term tests were conducted, indicating that the Ni hollow fiber membranes have good cycling operation performance and high resistance to CO, CO2, H2O and H2S poisoning at high temperatures. The excellent thermal and chemical stability as well as the high permeation performance make the Ni hollow fiber membranes great potentials in advanced applications such as the portable hydrogen sources or the large-scale hydrogen production from coal gasification.

Antibiofouling hollow-fiber membranes for dye rejection by embedding chitosan and silver-loaded chitosan nanoparticles

The removal of toxic dyes from the wastewater and industrial effluents is a major environmental challenge. Various techniques have been employed for the removal of dyes, including the application of nano-sized adsorbents, nanocomposite membranes and photodegradation. Membrane filtration is an alterntive but suffers from drawbacks such as fouling. Here we present a simple approach for the development of antibiofouling membranes based on chitosan. The application of chitosan-based nanoparticles as additives for wastewater treatment is poorly explored. The chitosan and silver-loaded chitosan nanoparticles were synthesized by ionic gelation method and incorporated to fabricate hollow-fiber membranes by dry–wet spinning technique. The prepared membranes were characterized by morphological study, permeability test, antibiofouling study and dye rejection study. The nanocomposite hollow-fiber membranes displayed superior performance than their pristine form. The incorporation of 0.30 weight percent of the chitosan and silver-loaded chitosan nanoparticles into the hollow-fiber membranes enhanced the antifouling property with flux recovery ratio of 81.21 and 86.13%, respectively. The dye rejection results showed maximum rejection of 89.27 and 86.04% for Reactive Black 5 and Reactive Orange 16, respectively. Hence, it can be concluded that hollow-fiber membranes with silver-loaded chitosan nanoparticles are pertinent in developing antibiofouling membranes for the treatment of industrial dye effluents.

Effect of Jet Stretch in the Fabrication of Polyethersulfone Hollow Fiber Spinning for Water Separation

The effect of jet stretch on the morphology, pure water permeation and sodium chloride rejection of hollow fiber membranes is analyzed by varying the spinning take up speed. Polyethersulfone hollow fibers were spun using dry–wet spinning technique. The membrane formulation of PES/NMP/Water/PVPk10 is spun at constant extrusion rate of 3.0 cm3/ min. The fiber take up speed during spinning varied from 19.7 to 29.5 cms–1, revealed that the flux of hollow fiber membranes is minimal when the fiber take up speed is equivalent to the velocity of dope extrusion. At low jet stretch, the permeability of membranes is high with elevated ionic solutes rejection produced. The influence of elongation stress towards hollow fiber membranes morphology and its performance for water separation is also highlighted.

Quality of Kiwifruit Juice Clarifed by Modifed Poly(Ether Ether Ketone) Hollow Fiber Membranes

Poly(ether ether ketone) with cardo group-based (PEEK-WC) membranes, in hollow fber (HF) confguration, were prepared via the dry-wet spinning technique through the phase inversion process and used to clarify kiwifruit juice. The depectinised juice was processed according to a batch concentration confguration in selected operating conditions (transmembrane pressure, 1.6 bar; feed flowrate 70 L/h; temperature, 25±2 °C) up to a volume reduction factor (VRF) of 1.8. The quality of clarifed juice was analysed in terms of total antioxidant activity (TAA), content of ascorbic, malic, succinic and citric acid, total polyphenols, suspended solids and total soluble solids (TSS). The prepared membranes allowed to remove suspended solids producing a clear juice with a content of organic acids, vitamin C and polyphenols comparable to that of the fresh juice. Accordingly, the TAA of the fresh juice was well preserved in the clarifed juice.

Antifouling polyethersulfone hemodialysis membranes incorporated with poly (citric acid) polymerized multi-walled carbon nanotubes

Poly (citric acid)-grafted-MWCNT (PCA-g-MWCNT) was incorporated as nanofiller in polyethersulfone (PES) to produce hemodialysis mixed matrix membrane (MMM). Citric acid monohydrate was polymerized onto the surface of MWCNTs by polycondensation. Neat PES membrane and PES/MWCNTs MMMs were fabricated by dry-wet spinning technique. The membranes were characterized in terms of morphology, pure water flux (PWF) and bovine serum albumin (BSA) protein rejection. The grafting yield of PCA onto MWCNTs was calculated as 149.2%. The decrease of contact angle from 77.56° to 56.06° for PES/PCA-g-MWCNTs membrane indicated the increase in surface hydrophilicity, which rendered positive impacts on the PWF and BSA rejection of the membrane. The PWF increased from 15.8Lm−2h−1 to 95.36Lm−2h−1 upon the incorporation of PCA-g-MWCNTs due to the attachment of abundant hydrophilic groups that present on the MWCNTs, which have improved the affinity of membrane towards the water molecules. For protein rejection, the PES/PCA-g-MWCNTs MMM rejected 95.2% of BSA whereas neat PES membrane demonstrated protein rejection of 90.2%. Compared to commercial PES hemodialysis membrane, the PES/PCA-g-MWCNTs MMMs showed less flux decline behavior and better PWF recovery ratio, suggesting that the membrane antifouling performance was improved. The incorporation of PCA-g-MWCNTs enhanced the separation features and antifouling capabilities of the PES membrane for hemodialysis application.

Syntheses of flame-retardant cellulose esters and their fibers

3-(Hydroxyphenylphosphinyl)-propanoic acid (3-HPP) esters of cellulose (HPP-Cellulose) were synthesized homogeneously in ionic liquid 1-butyl-3-methylimidazoliumchloride by in situ activation. The chemical structure of the cellulose esters is characterized by FTIR and NMR. The degree of substitution was easily controlled within 0.38-1.51 by varying the molar ratio of 3-HPP/anhydroglucose unit, reaction time, and temperature. All the products showed excellent solubility in common organic solvents. The results of TGA, DTG, LOI, and cone calorimeter test show that 3-HPP has a positive influence on the thermal properties and flame retardance of cellulose. Based on the volatilized products analysis by TGA-IR, the presence of 3-HPP reduces the intensity of volatilized product and accelerates the dehydration action. Moreover, the addition of cellulose (3 wt%) is beneficial to prepare HPP-Cellulose fibers using a dry-wet spinning technique, and the blended fibers possess good mechanical properties as well as flame resistance.

Effects of sintering atmospheres on properties of stainless steel porous hollow fiber membranes

Stainless steel (SS) is one of excellent materials for fabrication of hollow fiber membranes because of its good mechanical property. Phase inversion technique is a promising method for preparation of SS hollow fibers. The sintering step is critical for controlling the quality of SS hollow fibers by removal of organic additives and activation of particle binding. In this work, we prepared SS porous hollow fiber membranes by combined dry-wet spinning and sintering technique. The influence of sintering atmosphere (air, CO2, N2, He and H2) on microstructure and properties of SS hollow fibers were investigated extensively. It was found that air and CO2 could lead to metal oxidation while inert atmospheres (He and N2) caused carbon remaining in SS hollow fibers. By contrast, H2 atmosphere was effective in removing organic additives without metal oxidation. High mechanical strength could be achieved for the hollow fiber membranes sintered in H2 atmosphere. At 1100°C for 1h, the as-sintered SS hollow fiber showed high bending strength of >200MPa and nitrogen permeance up to 9.5×10−5mols−1m−2Pa−1.

Preparation and characterization of novel PSf/PVP/PANI-nanofiber nanocomposite hollow fiber ultrafiltration membranes and their possible applications for hazardous dye rejection

In the present study, PANI (polyaniline)-nanofibers were synthesized by interfacial polymerization technique, dispersed in n-Methyl-2-Pyrrolidone (NMP) solvent and blended with PVP (Polyvinylpyrrolidone)/PSf (Polysulfone) for preparing the novel hollow fiber membrane by dry–wet spinning technique. The newly prepared nanocomposite ultrafiltration hollow fiber membrane is characterized by Scanning Electron Microscope (SEM), Contact Angle, Zeta Potential and Differential Scanning Calorimeter (DSC). Filtration studies are conducted to measure the membrane pure water flux (PWF), rejection of hazardous dye (Reactive Red 120) and fouling resistance. The maximum rejections are obtained for M 0.5 membrane with 99.25% rejection of RR120 hazardous dye at 2bar pressure. The pure water flux, percentage rejection, antifouling property and thermal resistance increased with an increase in PANI-nanofiber concentration. The contact angle of the membrane decreased with increasing PANI-nanofiber concentration, which indicated increased hydrophilicity of the new membranes.