Blend Hollow Fiber Membranes Research Articles

On performance and anti-fouling properties of double-skinned thin film nanocomposite hollow fiber membranes in forward osmosis system

This study involves the preparation of a double-skinned thin film composite (TFC) and thin film nanocomposite (TFN) hollow fiber (HF) membrane for forward osmosis (FO) applications. The porous substrate consisted of a Polyvinyl chloride (PVC) / Polycarbonate (PC) blend HF membrane. Interfacial polymerization (IP) was then applied to coat a polyamide (PA) layer on the lumen surface and the porous substrate's outer surface. In addition, the impact of the outer PA active layer and the addition of nanoparticles to the outer selective layer on the FO flux and internal concentration polarization (ICP) were studied. By adding the second active layer to the substrate, water flux, reverse salt flux and ICP decreased. Also, the decline of water flux decreased over time due to the fouling agent. To compensate for the decrease in water flux in the double-skinned membrane, graphene oxide (GO) nanoparticles with 0.05% and 0.1%wt were added to the outer active layer. Addition of 0.1%wt graphene oxide nanoparticle to the outer active layer can help to improve water flux about 78% without spoiling the reverse salt flux. Moreover, the performance of double-skinned membranes against osmotic dilution process for oily wastewater treatment was investigated. The findings of this study demonstrated that the novel double-skinned TFN HF membrane exhibited high FO performance with low ICP and fouling.

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.

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.

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.

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.

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.

Effects of post-treatment on the structure and properties of PVDF/FEP blend hollow fiber membranes

Polyvinylidene fluoride (PVDF)/poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) blend hollow fiber membranes were prepared by the melt-spinning method.

Performance of an optimized Zr-based nanoparticle-embedded PSF blend hollow fiber membrane in treatment of fluoride contaminated water

Consumption of water that has excessive fluoride can cause adverse health impacts on human beings. A Zr-based nanoparticle-embedded PSF blend hollow fiber membrane was successfully prepared and optimized for removal of fluoride from the aqueous solution. Both static and dynamic adsorption of fluoride on the membrane was investigated. It was showed that the membrane could effectively remove fluoride within a wide pH ranging from 3 to 10. At neutral pH, the adsorption equilibrium was reached within 24 h. The maximum adsorption capacity of the optimized membrane was 60.65 mg/g, much higher than many commercial adsorbents. The presence of NO3−, SiO32− or HA has insignificant effects on the fluoride removal. However, the removal was retarded as the concentration of HCO3− or PO43− was increased. Furthermore, the membrane could remove fluoride efficiently through the continuous filtration, even in presence of natural organic matters. The spent membrane could be regenerated and then reused for the removal of fluoride with great efficiency. The adsorption history could be well described by an intraparticle diffusion model. The XPS analysis showed that the adsorption of fluoride was mainly associated with the ion-exchange between SO42− and F− ions. Finally, the toxicity analysis revealed that the treated water was safe for human consumption.

Preparation of Poly(vinyl chloride) Blend Hollow Fiber Membranes with Improved Antifouling Properties

Preparation of Poly(vinyl chloride) Blend Hollow Fiber Membranes with Improved Antifouling Properties

A novel Zr-based nanoparticle-embedded PSF blend hollow fiber membrane for treatment of arsenate contaminated water: Material development, adsorption and filtration studies, and characterization

Arsenic contamination in natural water has received a great attention due to its high toxicity, ease in accumulation in human body, and high carcinogenicity. A novel Zr-based nano-particle (NP) PSF blend hollow fiber membrane (HFM) was successfully fabricated for removal of arsenate from the aqueous solution. The NP-embedded HFM was characterized by morphology, hydrophilicity, porosity, water flux, mechanical strength and arsenic adsorption capacity. It was shown that the addition of NP changed the structure of the membranes and increased hydrophilicity, by which the water flux of the HFM was enhanced. The batch adsorption experiments indicated that the membrane could effectively remove arsenate at pH ranging from 2 to 9 and the maximum adsorption capacity was as high as 131.78mg/g that was much higher than many commercialized materials. The adsorption equilibrium could be established in 48h. Such co-existing anions as carbonate, fluoride, silicate and phosphate species had less significant effect on the adsorption. The membrane could remove arsenate efficiently via the continuous filtration, even in the presence of humic acid. A good performance for regeneration with a high recovery rate of 90.1% was achieved. The cytotoxicity analysis through the breast cancer stem cell line (MCF7) indicated that the water treated by the HFM was safe for human consumption. Finally, the XPS study showed that the hydroxyl and sulfate groups were associated with the uptake of arsenic. The sulfate played a key role in the arsenate removal.

Improvement of the antifouling properties of poly (lactic acid) hollow fiber membranes with poly (lactic acid)–polyethylene glycol–poly (lactic acid) copolymers

Poly (lactic acid) hollow fiber membranes with poly (lactic acid)–polyethylene glycol–poly (lactic acid) (PLA–PEG–PLA) triblock copolymers were synthesized using different molecular weight PEG segments, and were used as hydrophilic copolymers for the preparation of PLA/PLA–PEG–PLA blend hollow fiber membranes. The effects of the addition of PLA–PEG–PLA copolymers with different PEG segment lengths on the membrane morphology, hydrophobicity, and filtration performance were studied. Fouling experiments performed using BSA indicated that PLA–PEG–PLA copolymers with longer PEG segment lengths were more effective in improving the antifouling properties of the hollow fiber membranes, because of the higher retention of the synthesized copolymer additive in the membrane.