Blend Hollow Fiber Research Articles

Fabrication of PVDF/EVOH blend hollow fiber membranes with hydrophilic property via thermally induced phase process

In this study, thermally induced phase separation (TIPS) technology was used to fabricate the PVDF/EVOH blend hollow fiber membranes using water-soluble mixed diluents. An interconnected bulk structure was formed by L-L phase separation for both the pristine membrane and blend membrane. The surface enrichment for EVOH during the cooling process enhanced the hydrophilicity of prepared hollow fiber membranes. It was found that the tensile strength of the blend membrane significantly increased from 2.6 MPa to 8.8 MPa. The variation of the membrane structure made the water permeability increase from 60 L m−2 h−1 bar−1 to 287 L m−2 h−1 bar−1 for the optimized blend membrane. Compared with the pristine membrane, EVOH blend membrane exhibited higher antifouling properties for BSA, HA, and oil-in-water emulsion filtrations.

In-situ grown inorganic layer coated PVDF/PSF composite hollow fiber membranes with enhanced separation performance

Poly(vinylidene fluoride) (PVDF) membranes are widely employed for water treatment but mainly limited by their hydrophobic properties that increase the separation resistance. To make hydrophilic PVDF membranes, inorganic layer coated PVDF blend hollow fiber membranes are reported here. PVDF/polysulfone (PSF) blend hollow fiber membranes with pore size of ~110 nm were fabricated using PolarClean as a green solvent. Then, a facile and green method was employed to in-situ grow an inorganic layer (including TiO2 and Al2O3 layers) on these high strength membranes. Pluronic L61 was used as a dispersing agent to distribute the precursors in isopropanol, and enhanced adhesive strength between the polymer membrane and inorganic particles as characterized by XPS. The inorganic layers on the PVDF/PSF membrane surface both improved the mechanical strength from 7.7 MPa to 9.2 MPa and decreased the membrane roughness from ~50 nm to ~10 nm. The water permeance of the composite membranes can be finely tuned from 50 to 500 Lm−2h−1bar−1. In addition, the resulting membranes simultaneously enhanced the separation performance and anti-fouling performance characterized by bovine serum albumin (BSA) rejection behavior and flux recovery rate (FRR), respectively. The best BSA rejection and FRR of the PVDF/PSF-inorganic composite membranes reach 95% and 72.2%, respectively. The anti-fouling performance of composite membranes is mainly attributed to the decreased membrane roughness and enhanced hydrophilic properties compared with pristine PVDF/PSF membranes. Furthermore, the in-situ grown inorganic layers on the PVDF/PSF membrane surface effectively prevent foulants from blocking the pore channels as they are easily washed by the hydraulic washing method.

Improving permeability, hydrophilicity and antifouling characteristic of PES hollow fiber UF membrane using carboxylic PES: A promising substrate to fabricate NF layer

In this work, carboxylic polyethersulfone (CPES) was synthesized through acetylation and oxidation of polyethersulfone (PES). The success rate of the reaction and the formation of CPES were analyzed by fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Negatively charged CPES/PES blend hollow fiber ultrafiltration (UF) membranes were fabricated via the wet-spinning method. Surface and structural properties of the membranes were characterized by scanning electron microscopy (SEM), water contact angle (WCA), and atomic force microscopy (AFM). significant improvement of the membranes’ hydrophilicity due to the presence of the CPES was approved through the decrease of WCA from 76°(neat PES) to 42°. The permeability was increased up to about three times of the neat PES membrane, while the rejection was not affected that much and just decreased from 94% to 86%. Membrane’s antifouling properties were significantly improved according to the flux recovery ratio (FRR) of more than 90%. The best-suited hollow fiber membrane was used as a substrate for hyperbranched polyethyleneimine (HPEI) thin-film layer assembly to achieve nanofiltration (NF) membrane. It was shown that the presence of the CPES improved the layer assembly of the HPEI and thus the MgCl2 rejection in NF membranes. In this case, the salt rejection increased up to 95% for the best-suited membrane from 81% for the membrane with a neat PES substrate.

Biodegradation Process of PSF-PUR Blend Hollow Fiber Membranes Using Escherichia coli Bacteria-Evaluation of Changes in Properties and Porosity.

This work was focused on biodegradation with Escherichia coli bacteria studies of PSF-PUR blend semipermeable hollow fiber membranes that possibly can undergo a partial degradation process. Hollow fiber membranes were obtained from polysulfone (PSF) and polyurethane (PUR) containing ester bonds in the polymer chain in various weight ratios using two solvents: N,N-Dimethylmethanamide (DMF) or N-Methylpyrrolidone (NMP). The membranes that underwent the biodegradation process were tested for changes in the ultrafiltration coefficient (UFC), retention and cut-off point. Moreover, the membranes were subjected to scanning electron microscopy (SEM), MeMoExplorerTM Software and Fourier-transform infrared spectroscopy (FT-IR) analysis. The influence of E. coli and its metabolites has been proven by the increase in UFC after biodegradation and changes in the selectivity and porosity of individual membranes after the biodegradation process.

Chemical Degradation of PSF-PUR Blend Hollow Fiber Membranes-Assessment of Changes in Properties and Morphology after Hydrolysis.

In this study, we focused on obtaining polysulfone-polyurethane (PSF-PUR) blend partly degradable hollow fiber membranes (HFMs) with different compositions while maintaining a constant PSF:PUR = 8:2 weight ratio. It was carried out through hydrolysis, and evaluation of the properties and morphology before and after the hydrolysis process while maintaining a constant cut-off. The obtained membranes were examined for changes in ultrafiltration coefficient (UFC), retention, weight loss, morphology assessment using scanning electron microscopy (SEM) and MeMoExplorer™ Software, as well as using the Fourier-transform infrared spectroscopy (FT-IR) method. The results of the study showed an increase in the UFC value after the hydrolysis process, changes in retention, mass loss, and FT-IR spectra. The evaluation in MeMoExplorer™ Software showed the changes in membranes’ morphology. It was confirmed that polyurethane (PUR) was partially degraded, the percentage of ester bonds has an influence on the degradation process, and PUR can be used as a pore precursor instead of superbly known polymers.

Polyacrylonitrile homogeneous blend hollow fiber membrane with stable structure as a substrate to support Fe/Mn oxide and its enhanced capability to purify dye wastewater

Abstract Blending different molecular weight polyacrylonitrile (PAN) was adopted to solve the shrinkage problem of high molecular weight PAN hollow fiber membrane, to enhance the application performance of low molecular weight PAN membrane, and to adjust the porosity, pore size distribution, and hydrophilicity of the end product. The structurally-optimized membrane was chosen as a substrate to support Fe/Mn oxides and then used as a reactor to remove dyes from their solutions in the presence of H2O2. The results showed that the flux of methylene blue (MB) aqueous solution was 83.7 L/m2 h for the PAN homogeneous blend membrane, much higher than 29.1 L/m2 h of high molecular weight PAN membrane; MB removal efficiency was 97.3%, higher than 62.3% of low molecular weight PAN membrane, and it could be reused 25 times to remove dyes from their solutions without any loss in removal efficiency. The membrane was also found to have the application advantages of decreasing H2O2 dosage, reducing operation pressure, and raising MB removal efficiency compared with other membranes reported in the pieces of literature. Therefore, we were confident that the hollow fiber membrane fabricated by us would exhibit great application potential in the field of decontaminating dye wastewater.

The structure and properties of poly(vinylidene fluoride)/ultrahigh-molecular -weight polyethylene blend hollow fiber membranes via TIPS with mixed diluents

To synchronously improve mechanical properties and permeability of poly (vinylidene fluoride) (PVDF) membranes, PVDF/ultrahigh-molecular-weight polyethylene (UHMWPE) blending hollow fiber membranes were prepared by a thermally induced phase separation method, with mineral oil and dibutyl phthalate as mixed diluents. To study the fluidity, phase separation and crystallization behavior of the membrane-forming system, the element distribution state, morphology and pore structure of the membrane were observed by energy -dispersive X-ray testing microanalysis, field-emission scanning electron microscopy, gas-liquid interface pore size measurements and porosity measurements. Finally, the permeability, separation and mechanical properties were measured by gas flux, pure water flux, talc powder rejection rate and tensile experiments. The results showed that solid-liquid phase separation caused by PVDF preferential crystallization, liquid-liquid phase separation between UHMWPE and mineral oil, and solid-liquid phase separation caused by UHMWPE crystallization occurred sequentially during cooling. The connectivity of membrane was enhance by UHMWPE microfiber. When water flux of the blending membranes reached 8000 L/m2/h/MPa, the strength also reached 11.8 MPa. The membranes had outstanding permeability and mechanical property simultaneously. With UHMWPE content increased, the porosity and average pore size decreased, which caused a decrease in the flux and an increase in the rejection rate.

Purification of Polyphenols from Green Tea Leaves and Performance Prediction Using the Blend Hollow Fiber Ultrafiltration Membrane

Hollow fiber–based ultrafiltration is used as a tool to enhance purity of polyphenols and in particular epigallocatechin gallate (EGCG), from microfiltered green tea leaves. Polysulfone-polyvinylidene fluoride (PVDF) blend was used to prepare the hollow fibers and membrane M-3 having 6-wt% PVDF in polymer solution with 30-kDa molecular weight cut off, permeability 17.7 × 10−11 m/Pa s with an average pore radius 5.3 nm, was identified as the suitable one. Increase in PVDF in spinning solution made the membrane more porous. The higher cut off membrane suffered from acute pore blocking leading to low flux recovery ratio, high flux decline ratio, and relatively lower polyphenol and EGCG purity. A transport phenomena–based model was formulated to calculate the profiles of permeate flux and concentration of polyphenols in the permeate. The model parameters were evaluated by matching the calculated data with experimental results. Permeation results indicated that 138-kPa transmembrane pressure drop and 30-l/h cross flow rate were desirable operating conditions having high permeate flux 55 l/m2 h with polyphenol purity 88% and EGCG purity 81%.

EVOH in situ fibrillation and its effect of strengthening, toughening and hydrophilic modification on PVDF hollow fiber microfiltration membrane via TIPS process

In order to enhance the strength and overcome the poor antifouling capacity of poly(vinylidene fluoride) (PVDF) membrane used in water treatment, herein, poly(ethylene-co-vinyl alcohol) (EVOH) was selected and the PVDF/EVOH blend hollow fiber microfiltration membrane was prepared via the thermally induced phase separation (TIPS) technique. The morphology for the pristine and blend membrane was compared, and the distribution of EVOH on outer surface and within matrix was explored. The fibrous-shaped EVOH enhanced the breaking strength of the membrane markedly (up to 13.63 MPa) due to the in situ fibrillation; especially, when the blend membrane was immersed into water, the internal plasticization of water molecular enhanced the toughness of the membrane and the elongation at break increased up to 86.39% compared with 27.63% for the corresponding dry membrane and 36.62% for the pristine membrane, respectively. The addition of EVOH introduced hydroxyl group into the bulk and thus endowed the membrane with a better hydrophilicity (the contact angle is as low as 43°) and higher pure water flux (up to 449.11 L m−2 h−1) compared with pristine PVDF membrane. Moreover, the blend membrane showed a better rejection of carbonic particle (nearly 100%) and higher flux recovery rate (up to 87.30%). The present investigation offers an effective and simple pattern to regulate microstructure and enhance mechanical strength, flux and hydrophilicity of the polymeric microfiltration membrane via the TIPS process for water treatment.

Fabricating PVDF hollow fiber microfiltration membrane with a tenon-connection structure via the thermally induced phase separation process to enhance strength and permeability

In this work, thermally induced phase separation (TIPS) method was adopted to manufacture polyvinylidene fluoride (PVDF) blend hollow fiber microfiltration membrane with tenon-connection structure, which is used to fasten in Chinese traditional building by the stronger friction between rabbet and mortise, for water treatment by blending polyvinyl butyral (PVB). In this microstructure formation process, the distribution of PVB within the matrix and its regulatory role were investigated. Especially, the comprehensive effect of rabbeting and PVB adhesion on strength (The maximum breaking strength reached 17.08 MPa) was discussed. The results showed that a suitable PVB will markedly reduce the thickness of skin-layer close to the outside surface even for the solid-liquid (S-L) phase separation while the excessive PVB result in a thick skin-layer. Besides the strength, PVB markedly improved the hydrophilicity and permeability of the membrane. The breaking strength is more than 8 MPa, the maximum pure water flux is as high as 929.23 L m−2 h−1 and the rejection rate of carbon particles is nearly 100% even the polymer content is only 22%. In addition, the membrane showed a β-phase and an improved anti-fouling capacity. The investigation presented a simple way to regulate microstructure, enhance mechanical strength, flux and anti-fouling capacity of the membrane via the TIPS process for water treatment.

Fabrication of novel PVDF/P(VDF-co-HFP) blend hollow fiber membranes for DCMD

In this research, porous hollow fiber membranes for DCMD desalination were fabricated by non-solvent induced phase inversion. The membrane materials were PVDF 6010 and its blend with P(VDF-co-HFP), expected to combine the advantages of each material. It was found that with higher P(VDF-co-HFP) content in the blend, the membrane materials acquired stronger hydrophobicity. The maximum tensile strength was obtained with hollow fibers having 30% P(VDF-co-HFP), which was 2.86 MPa. Cloud point test showed that the one phase region of the solution with neat P(VDF-co-HFP) was closer to the polymer-solvent axis in the phase diagram, indicating a lower thermodynamic stability of this polymer solution. The varied degree of the liquid/liquid demixing and the solid/liquid demixing induced by changing P(VDF-co-HFP) content might be the underlying factor causing the dissimilarities in the above membrane structural and mechanical characteristics. DSC was employed to corroborate the crystallinity of the membranes. The DCMD tests using NaCl aqueous solution showed that membranes with higher PVDF 6010 content provided apparently higher flux. Stable salt rejection above 99% were obtained with all the membranes under the operation conditions investigated.

TIPS behavior for IPP/nano-SiO2 blend membrane formation and its contribution to membrane morphology and performance

Abstract In the present work, the TIPS behavior of isotactic polypropylene (iPP)/di-n-butyl phthalate (DBP)/dioctyl phthalate (DOP)/nano-SiO2 system and the competition relation between liquid–liquid phase separation and polymer crystallization are successfully adjusted by adding nano-SiO2. The liquid–liquid phase separation temperature of the system increases with increasing nano-SiO2 content. Besides, iPP crystallization temperature is also changed after adding nano-SiO2. IPP/nano-SiO2 blend hollow fiber microporous membrane is prepared via TIPS method. SEM photos show that the membrane exhibits mixed morphology combining cellular structure relating to liquid–liquid phase separation and branch structure originating from polymer crystallization. The relative weight of cellular structure first decreases and then increases with the increase of nano-SiO2 content. Furthermore, porosity, connectivity among pores and pure water flux of the membrane first increase and then decrease with increasing nano-SiO2 content. However, mechanical performance of the membrane is improved at all times with increasing nano-SiO2 content.

Robust self cleaning polypyrrole‐polysulfone blend hollow fiber membrane for biofouling mitigation

AbstractBACKGROUNDPersistent biofouling of membrane is the most commonly encountered problem during separation diminishing the throughput of the system. Many techniques have been adopted to mitigate biofouling. This paper describes the fabrication of polysulfone and polypyrrole blend hollow fiber membrane with outstanding self‐cleaning potential. Blending of polypyrrole promoted excellent anti‐biofouling surface against Gram positive and Gram negative bacteria. The impact of flow rate and pressure on membrane performance was also evaluated during the separation process.RESULTSLoading of polypyrrole resulted in enhanced hydrophilicity, permeability, zeta potential and tensile strength. Scanning electron microscopy confirmed the appearance of macrovoids with increase of polypyrrole concentration, indicating the porous structure of the membrane. Hollow fibers exhibited negative potential at pH 7, leading to excellent anti‐biofouling surface. Roughness of fibers was dramatically reduced from 120 to 3 nm with polypyrrole concentration imparting superior self cleaning surface on the membrane. Fluorescence microscopy analyses revealed significant reduction in bacteria adhesion on 1 wt% polypyrrole loaded fibers. Modified membrane showed striking antibacterial property due to the leakage of cytoplasmic materials through lysis, as supported by A260nm absorption study. Morphological analysis of the used blend membrane showed almost no deposition of bacteria even after a long run, holding the promise of biofouling mitigation.CONCLUSIONModification of membrane by polypyrrole imparted an outstanding self‐cleaning property to the hollow fiber; hence, it is a simple and scalable approach to prevent biofouling during long‐term performance. © 2018 Society of Chemical Industry

Evaluating the Antifouling Properties of Poly(ether sulfone)/Sulfonated Poly(ether sulfone) Blend Membranes in a Full-Size Membrane Module

To evaluate the antifouling properties of the poly(ether sulfone) (PES)/sulfonated poly(ether sulfone) (SPES) blend membranes, the full-size membrane modules containing pure PES hollow fiber membranes and PES/SPES blend hollow fiber membranes were prepared and compared. First, a series of PES/SPES blend hollow fiber membranes with different SPES fraction were fabricated by a nonsolvent-induced phase separation (NIPS) process. The surface chemical compositions, morphology, surface wettability, permeability, and mechanical strength of the membranes were characterized. After assembling the module, the permeability and antifouling properties of the full-size modules were tested in a lab-scale evaluation system. Each full-size membrane module in this study included approximately 330 pieces of 1 m long hollow fiber membranes with an effective area of approximately 1 m2. Three model foulants, i.e., sodium alginate (SA), humic acid (HA), and bovine serum albumin (BSA), and three real river water samples were used...

Titanium white waste acid concentration by DCMD: Wetting, crystallization, and fouling

We have investigated titanium white waste acid (TWWA) concentration by direct contact membrane distillation (DCMD) using self-made (PVDF)/poly(vinylidene-co-hexafluoropropylene) (P(VDF-co-HFP)) blend hollow fiber membranes. The concentration degree, ferrous sulphate (FeSO4) precipitation and membrane fouling/cleaning were investigated at different temperature and flow rate of feed streams. It was found that membrane with PVDF/P(VDF-co-HFP) ratio of 12/6 (w/w) (M1) had slightly larger contact angle, but very low flux (<6 kg/m2-h). Another ratio with more PVDF delivered membranes (M2) with significantly better flux. With the modules M2 batch of hollow fibers, the feed acid was concentrated up to around 58% at 70 °C (feed) and FeSO4 precipitated out during the DCMD. Surface fouling was confirmed by SEM analysis; the situation of surface fouling is more serious with higher concentration. Tests regarding effect of feed flow rate indicated that higher speed could reduce the fouling degree and foulant particle size. The final sulfuric acid (H2SO4) concentration is highest for modules operated at 150 ml/min of feed flow. Membrane cleaning involving HCl solution rinsing and air drying restored the salt rejection to be higher than 99%, but with depreciation in vapor flux.

Immobilization of copper ions on chitosan/cellulose acetate blend hollow fiber membrane for protein adsorption

The prepared IMAM (CS/CA-Cu) achieved a high adsorption capacity of 69 mg-BSA per g-membrane.

PVDF/PVDF-g-PACMO blend hollow fiber membranes for hemodialysis: preparation, characterization, and performance

A novel approach to improve the biocompatibility of PVDF hollow fiber membrane by blending PVDF-g-PACMO copolymer for hemodialysis is provided.

Solvent effect and macrovoid formation in cellulose acetate phthalate (CAP)–polyacrylonitrile (PAN) blend hollow fiber membranes

ABSTRACTThe interactions which govern the morphology of blend hollow fiber membranes is explored in detail in the present work. A hydrophilic (cellulose acetate phthalate) and a relatively hydrophobic polymer (polyacrylonitrile, critical surface tension 47.0 mJ/m2) blend in three solvents, viz., n‐methylpyrrolidone (NMP), dimethyl formamide (DMF), and dimethylsulfoxide (DMSO), has been selected as an example to understand the polymeric blend—solvent and nonsolvent interactions. The deviation intrinsic parameter ( ) is estimated as well as cloud point, linearized cloud point (LCP), and Fourier transform‐infrared (FT‐IR) analysis have been performed for the blend membranes. The analysis yields that is negative for both DMF and NMP indicating miscibility, whereas for DMSO it is positive indicating immiscibility. Cloud point and LCP analysis too reveal DMSO to be the poorest solvent and liquid‐liquid demixing is the governing phenomenon for the phase inversion. In depth interaction is conducted with help of FT‐IR spectra. The higher red shift of &gt;C==O (1747 to 1665 cm−1) after complete phase inversion indicates stronger interaction in DMF and NMP, whereas, no shift in &gt;C==O stretching in DMSO indicates weak or no interaction. This reveals that polymer blend‐solvent interaction is weak in case of DMSO than DMF or NMP. These observations manifest in DMSO membranes being most porous, with highest permeability and molecular weight cut off with poor tensile strength. On the other hand, NMP and DMF hollow fiber membranes yields denser structure with better mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44366.

Modification of polyethersulfone hollow fiber membrane with different polymeric additives

The improvement of fouling resistance of porous polymeric membrane is one of the most important targets in membrane preparation for water purification in many process like wastewater treatment. Membranes can be modified by various techniques, including the treatment of polymer material, blending of hydrophilic polymer into polymer solution, and post treatment of fabricated membrane. This research proposed the modifications of morphology and surface property of hydrophobic membrane by blending polyethersulfone (PES) with three polymeric additives, polyvinylpyrrolidone (PVP), Pluronic F127 (Plu), and Tetronic 1307 (Tet). PES hollow fiber membranes were fabricated via dry-wet spinning process by using a spinneret with inner and outer diameter of 0.7 and 1.0 mm, respectively. The morphology changes of PES blend membrane by those additives, as well as the change of performance in ultrafiltration module were comparatively observed. The surface structure of membranes was characterized by atomic force microscopy and Fourier transform infra red spectroscopy. The cross section morphology of PES blend hollow fiber membranes was investigated by scanning electron microscopy. The results showed that all polymeric additives blended in this system affected to improve the performances of PES membrane. The ultra-filtration experiment confirmed that PES-PVP membrane showed the best performance among the three membranes on the basis of filtration stability.

Clarification and storage study of bottle gourd (Lagenaria siceraria) juice by hollow fiber ultrafiltration

Ultrafiltration of bottle gourd juice was undertaken in this study using hollow fibers with the objective to have juice with long shelf life without heat treatment, preservatives and additives maintaining the natural taste, flavor and nutritional quality intact. Five blend hollow fiber membranes (M-1 to M-5) with 15wt% polyacrylonitrile (PAN) and 5wt% cellulose acetate phthalate (CAP) were prepared. No additive was used in M-1 membrane. For M-2 and M-3 membranes polyethylene glycol (PEG) of molecular weight 200Da was used as an additive with concentration 1.5 and 3wt%, respectively. 3wt% PEG of molecular weight 1500Da was used in M-4 and same concentration of PEG of molecular weight 4000Da was used in M-5 membrane. The membranes were characterized in terms of permeability, molecular weight cut off, permeate flux, permeate quality and anti-fouling characteristics. M-3 membrane was selected based on performance. Experiments were conducted both in total recycle and batch concentration mode. In case of total recycle mode, transmembrane pressure drop (TMP) was varied from 35 to 104kPa and that of cross flow rate (CFR) was from 10 to 20l/h. Quality of the filtered juice was analyzed in terms of color, clarity, total soluble solid, polyphenol, concentration of protein, sodium and potassium. TMP 104kPa and CFR 20l/h were found to be suitable operating conditions for filtration. The filtered juice was stored for 8 weeks under normal refrigeration. All the nutritional parameters (total protein, polyphenol, sodium, potassium and total soluble solids) including taste were monitored and it was found that the quality of the juice was maintained with a positive purchase intention.