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1.
Mitigated membrane fouling in an SMBR by surface modification   总被引:1,自引:0,他引:1  
Fouling is a major obstacle in membrane processes applied in membrane bioreactor. To improve the antifouling characteristics of polypropylene hollow fiber microporous membranes (PPHFMMs) in a submerged membrane bioreactor (SMBR), the PPHFMMs were surface modified by NH3, CO2 plasma treatment, photoinduced graft polymerization of acrylamide and acrylic acid. The structural and morphological changes on the membrane surface were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (FT-IR/ATR) and field emission scanning electron microscopy (FE-SEM). The change of surface wettability was monitored by contact angle measurements. The results of XPS and FT-IR/ATR clearly indicated the successful modification on the membrane surface. The static water contact angle of the modified membrane reduced obviously. The antifouling characteristics of the modified membranes in an SMBR were evaluated. The modified membranes showed better filtration performances in the submerged membrane bioreactor than the unmodified one, and the acrylic acid-grafted membrane presented the best antifouling characteristics. The results demonstrated that (1) the surface carboxyl-containing membranes were better than the surface amido-containing membranes; (2) surface-grafted membranes were better than the plasma-treated membranes.  相似文献   

2.
The major objective of this research was to modify the surface characteristics of poly(L ‐lactide) (PLA) by grafting a combination of hydrophilic polymers to produce a continuum of hydrophilicity. The PLA film was solvent cast, and the film surfaces were activated by ultra violet (UV) irradiation. A single monomer or combination of two monomers, selected from vinyl acetate (VAc), acrylic acid (AA), and acrylamide (AAm), were then grafted to the PLA film surface using a UV induced photopolymerization process. The film surfaces resulting from each reaction step were analyzed using ATR‐FTIR spectroscopy and contact angle goniometry. Results showed that AAm dominated the hydrophilicity of the film surface when copolymerized with VAc or AA, while the water contact angles for PLA films grafted with poly(vinyl acetate‐co‐acrylic acid) varied more gradually with feed composition. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6534‐6543, 2006  相似文献   

3.
Novel ultrafiltration membranes were prepared by simple blending of polyethersulfone (PES) and soybean phosphatidylcholine (SPC). X-ray photoelectron spectroscopy (XPS) and water contact angle measurements indicated SPC enrichment at the membrane surfaces. The immobilization and arrangement of PC groups at surfaces rendered the membranes more hydrophilic. BSA adsorption amount decreased from 56.2 μg/cm2 for SPC-free PES membrane to 2.4 μg/cm2 for PES/SPC blend membrane. The fouling-resistant property of the blend membranes was improved considerably with an increase of SPC content while the pure water permeation flux decreased remarkably. Using PEG/PVP mixture instead of PEG as pore-forming agent increased pure water flux of PES/SPC blend membrane to some extent.  相似文献   

4.
PVDF/(PEI‐C/PAA)n functional membranes were prepared by layer‐by‐layer (LbL) assembly, and their heavy metal ions adsorption capability was investigated. The changes in the chemical compositions of membrane surfaces were determined by X‐ray photoelectron spectroscopy (XPS). XPS results show that the surface of the PVDF membrane can be alternatively functionalized by PEI‐C and PAA. The membrane surface hydrophilicity was evaluated through water contact angle measurement. Contact angle results show that the surface hydrophilicity of the membrane surface depends on the outermost deposited layer. Morphological changes of membrane surfaces were observed by scanning electron microscopy (SEM). The water fluxes for these membranes were elevated after modification. The performances of the PVDF/(PEI‐C/PAA)n membranes on the adsorption of copper ions (Cu2+) from aqueous solutions were investigated by inductively coupled plasma (ICP). The results indicate that the PVDF/(PEI‐C/PAA)n functional membranes show high copper ions adsorption ability. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

5.
The blend surface of polyamide 6 and polytetrafluoroethylene (PA 6/PTFE) and its change as a function of annealing time are investigated by means of attenuated total reflection (ATR)‐FTIR spectroscopy, contact angle (CA) measurement, as well as atomic force microscopy (AFM) under ambient condition; meanwhile the surface elemental compositions are obtained by X‐ray photoelectron spectroscopy (XPS). The results show that the addition of fluoro content can decrease the surface energy compared with the pure polyamide, while, an evident influence on the surface energy has not been detected with increasing fluoro contents. Upon annealing at 120 °C, there is a profound enrichment of the low‐surface energy component to the sample surface; yet this situation becomes more complex when samples are annealed at 150 °C—not only the segregation effect from the low surface energy PTFE, but also the crystallization of the PA 6 will come into play for the blend with 50% PTFE. These observations are ascribed to the presence of the polar group of the polyamide component, as well as its strong tendency to crystallize when subjected to thermal treatment at sufficiently high temperatures, and this behavior would basically offset the segregation tendency of fluoro component to the sample surface. This assumption is further corroborated by the XPS measurement in the current researches. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 138–152, 2007  相似文献   

6.
Membrane-bioreactor processes have increased considerably in recent years. However, the natural disadvantages of common membrane materials, such as hydrophobic surface, cause membrane fouling and cumber further extensive applications. In this work, hydrophilic surface modification of polypropylene microporous membranes was carried out by the sequential photoinduced graft polymerization of d-gluconamidoethyl methacrylate (GAMA) to meet the requirements of wastewater treatment and water reclamation applications. The grafting density and grafting chain length were controlled independently in the first and second step, respectively. Attenuated total reflection–Fourier transform infrared spectroscopy (FT-IR/ATR) and X-ray photoelectron spectroscopy (XPS) were employed to confirm the surface modification on the membranes. Water contact angle was measured by the sessile drop method. Results of FT-IR/ATR and XPS clearly indicated that GAMA was grafted on the membrane surface. It was found that the grafting chain length increased reasonably with the increase of the UV irradiation time. Water contact angle on the modified membrane decreased with the increase of the grafting chain length, and showed a minimum value of 43.2°, approximately 51.8° lower than that of the unmodified membrane. The pure water fluxes for the modified membranes increased systematically with the increase of the grafting chain length. The effect of the grafting chain length on the antifouling characteristics in a submerged membrane-bioreactor for synthetic wastewater treatment was investigated. After continuous operation in the submerged membrane-bioreactor for about 70 h, reduction from pure water flux was 90.7% for the virgin PPHFMM, and ranged from 80.8 to 87.2% for the modified membranes, increasing with increasing chain length. The flux of the virgin PPHFMM membrane after fouling and subsequent washing was 31.5% of the pure water flux through the unfouled membrane; for the modified membranes this ranged from 27.8 to 16.3%, decreasing with increasing chain length. These results demonstrated that the antifouling characteristics for the glucopolymer-modified membranes were improved with an increase in GAMA chain length.  相似文献   

7.
Regenerated cellulose (RC) membranes which have pH modulated permeability have been prepared by anchoring the hydroxyl groups on the membrane surface with 2‐bromoisobutyryl bromide, followed by grafting with acrylic acid (AA) using atom transfer radical polymerization (ATRP). The obtained membranes were analyzed by X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared attenuated total reflection spectrometer (ATR‐FTIR), scanning electron microscopy (SEM), TGA and the results showed that AA had been grafted onto the membrane surfaces successfully. Then the pH modulated permeability properties were tested by water flux measurement. All results show that the pH modulated permeability properties of a RC membrane can be obtained by surface‐initiated ATRP. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

8.
Two kinds of polypeptides were tethered onto the surface of polypropylene microporous membrane (PPMM) through a ring opening polymerization of L-glutamate N-carboxyanhydride initiated by amino groups which were introduced by ammonia plasma and y-aminopropyl triethanoxysilane treatments. X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR/ATR), scanning electron microscopy (SEM), together with water contact angle measurements were used to characterize the modified membranes. XPS analyses and FT-IR/ATR spectra demonstrated that polypeptides are actually grafted onto the membrane surface. The wettability of the membrane surface increases at first and then decreases with the increase in grafting degrees of polypeptide. Platelet adhesion and murine macrophage attachment experiments reveal an enhanced hemocompatibility for the polypeptide modified PPMMs. All these results give evidence that polypeptide grafting can simultaneously improve the hemocompatibility as well as reserve the hydrophobicity for the membrane, which will provide a potential approach to improve the performance of polypropylene hollow fiber microporous membrane used in artificial oxygenator.  相似文献   

9.
《中国化学》2017,35(7):1109-1116
We fabricate a novel cellulose acetate (CA) ultrafiltration membrane modified by block copolymer F127‐b‐ PDMAEMA, which is synthesized using F127 and DMAEMA via the ARGET ATRP method. Compared to conventional ultrafiltration membranes, the incorporation of both F127 and PDMAEMA can not only readily increase the hydrophilicity of the membrane, but also exhibit stimuli‐responsiveness to temperature and pH. Fourier transform infrared spectroscopy (FT‐IR), nuclear magnetic resonance spectroscopy (NMR), and gel permeation chromatography (GPC) are employed to analyze the structure of the F127‐b‐PDMAEMA. The membrane properties are evaluated via scanning electron microscope (SEM) imaging, porosity test, automatic target recognition Fourier transform infrared spectroscopy (ATR‐FTIR), water contact angle test and permeation test. The results indicate that the F127‐b‐PDMAEMA is an excellent pore agent, which contributes to an enhancement of the membrane in sensitivity to temperature and pH. The modified membrane also exhibits lower water contact angle (64.5°), which is attributed to the good anti‐fouling performance and high water permeation.  相似文献   

10.
The perfluorosulfonic acid membranes which are used in direct methanol fuel cells were modified with argon plasma under various conditions, and the physicochemical and transport properties of the resulting membranes were investigated using various analytical techniques. The plasma treatment was found to change the surface morphology and physicochemical properties of the membranes. The surface roughness of the membranes was increased by the etching effect of plasma. From the FTIR and XPS analyses, the incorporation of new oxygen functionalities, such as the peroxide group, was confirmed. The breakage of both the sulfonic acid groups and ether linkages were also found to cause an increase in the equivalent weight of the modified skin layer of the membrane. The incident water contact angle of the modified membrane in a dry state decreased with an increased plasma treatment, because of the hydrophilic groups that developed on the membrane surface. The time-dependent water contact angle, however, increased in proportion to the extent of the plasma treatment, due to the reduced concentration of sulfonic acid groups. Although the equilibrium water uptake of the modified membrane was almost invariable because of the negligible thickness of the modified skin layer, the transport properties of the membrane such as methanol permeability and proton conductivity were significantly reduced.  相似文献   

11.
RAFT mediated grafting of poly(t‐butyl acrylate) onto the surface of a commercial poly(ethylene‐co‐propylene), Elpro, has been carried out using initiation by 60Co γ‐radiation at 298 and 273 K. The polymerizations were in bulk monomer and using the RAFT agent 1‐phenylethyl phenyldithioacetate. The rates of homopolymerization and grafting were found to decrease with increasing RAFT agent concentration, indicating that both polymerization processes involve participation of the RAFT agent. There was good agreement between the predicted and experimental molecular weights of the homopolymer that had a narrow polydispersity. The poly(t‐butyl acrylate) grafts were hydrolyzed by trifluoroacetic acid to form poly(acrylic acid) grafts, which could either be further functionalized or used to control the surface polarity of the Elpro. ATR‐FTIR spectroscopy was used to characterize the grafts and Raman spectroscopy was used to assess the depth of the grafts. The water contact angle for the Elpro surface grafted with poly(acrylic acid) was found to be linearly dependent on the amount of the graft present. The living nature of the grafted chains was demonstrated by the addition of a second block of polystyrene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1074–1083, 2007  相似文献   

12.
An amphiphilic comb polymer consisting of poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) [P(VDF‐co‐CTFE)] main chains and poly(oxyethylene methacrylate) (POEM) side chains was synthesized using direct initiation of the chlorine atoms in CTFE units through atom transfer radical polymerization, as confirmed by 1H NMR and FTIR spectroscopy. The P(VDF‐co‐CTFE)‐g‐POEM comb polymer was introduced as an additive to prepare poly(vinylidene fluoride) antifouling ultrafiltration membranes. As the contents of comb polymer increased, the mechanical properties of membranes slightly decreased due to the decreased crystallinity of the membranes, as revealed by universal testing machine and X‐ray diffraction. However, water contact angle measurement and X‐ray photoelectron spectroscopy showed that the hydrophilic POEM segments spontaneously segregated on the membrane surfaces. As a result, the antifouling property of the membranes containing P(VDF‐co‐CTFE)‐g‐POEM comb polymer was considerably improved with a slight change of water flux. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 183–189, 2010  相似文献   

13.
Accumulation of water in ion‐selective membranes, can lead to inconsistent potentiometric responses with solid‐contact ion‐selective electrode (SC‐ISE) formats, and hence it is essential to restrain their water uptake. We have used FTIR‐ATR spectroscopy to study how the water uptake is influenced by the intermixing of a poly(3‐octylthiophene) (POT) SC and a poly(methyl methacrylate):poly(n‐decyl methacrylate) (PMMA:PDMA) based polymeric membrane matrix, the only SC‐ISE system for which direct evidence was provided on the aqueous layer elimination. Numerical simulations of the FTIR‐ATR spectra of 1 or 5 wt% POT containing PMMA:PDMA membranes showed that the addition of 5 wt% POT to the membrane lowered the equilibrium water uptake, whereas the diffusion coefficients of water in the membrane were found to be less affected. Consequently, POT is beneficial for preventing the formation of detrimental water layers in the SC‐ISE structure.  相似文献   

14.
A series of temperature‐sensitive poly(CSA‐co‐NIPAAm) membranes that were suitable for cell culture and confluent cell sheets detachment were prepared. The membranes with thermo‐responsive surface properties were synthesized by the copolymerization of acrylic acid‐derivatized chitosan (CSA) and N‐isopropylacrylamide (NIPAAm) in aqueous solution. Characterization of the membranes were carried out by means of the Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and water contact‐angle (WCA) measurements. The adhesion and detachment of mouse fibroblast (L929) cells on these membranes have been investigated. The study showed that poly(CSA‐co‐NIPAAm) membranes could not only enhance fibroblasts attachment but also harvest confluent cell sheets by simply lowering the temperature. Furthermore, the detached cells retained high viability and could proliferate again after transferred to a new culture surface. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

15.
To endow hydrophobic poly(vinylidene fluoride) (PVDF) membranes with reliable hydrophilicity and protein resistance, an amphiphilic hyperbranched-star polymer (HPE-g-MPEG) with about 12 hydrophilic arms in each molecule was synthesized by grafting methoxy poly(ethylene glycol) (MPEG) to the hyperbranched polyester (HPE) molecule using terephthaloyl chloride (TPC) as the coupling agent and blended with PVDF to fabricate porous membranes via phase inversion process. The chemical composition changes of the membrane surface were confirmed by X-ray photoelectron spectroscopy (XPS), and the membrane morphologies were measured by scanning electron microscopy (SEM). Water contact angle, static protein adsorption, and filtration experiments were used to evaluate the hydrophilicity and anti-fouling properties of the membranes. It was found that MPEG segments of HPE-g-MPEG enriched at the membrane surface substantially, while the water contact angle decreased as low as 49 degrees for the membrane with a HPE-g-MPEG/PVDF ratio of 3/10. More importantly, the water contact angle of the blend membrane changed little after being leached continuously in water at 60 degrees C for 30 days, indicating a quite stable presence of HPE-g-MPEG in the blend membranes. Furthermore, the blend membranes showed lower static protein adsorption, higher water and protein solution fluxes, and better water flux recovery after cleaning than the pure PVDF membrane.  相似文献   

16.
The sulfonated poly(ether ether ketone sulfone) (SPEEKS)/heteropolyacid (HPA) composite membranes with different HPA content in SPEEKS copolymers matrix with different degree of sulfonation (DS) were investigated for high temperature proton exchange membrane fuel cells. Composite membranes were characterized by Fourier transfer infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). FTIR band shifts suggested that the sulfonic acid groups on the copolymer backbone strongly interact with HPA particles. SEM pictures showed that the HPA particles were uniformly distributed throughout the SPEEKS membranes matrix and particle sizes decreased with the increment of copolymers' DS. The holes were not found in SPEEKS‐4/HPA30 (consisting of 70% SPEEKS copolymers with DS = 0.8 and 30% HPA) composite membrane after composite membranes were treated with boiling water for 24 h. Thermal stabilities of the composite membranes were better than those of pure sulfonated copolymers membranes. Although the composite membranes possessed lower water uptake, it exhibited higher proton conductivity for SPEEKS‐4/HPA30 especially at high temperature (above 100 °C). Its proton conductivity linearly increased from 0.068 S/cm at 25 °C to 0.095 S/cm at 120 °C, which was higher than 0.06 S/cm of Nafion 117. In contrast, proton conductivity of pure SPEEKS‐4 membrane only increased from 0.062 S/cm at 25 °C to 0.078 S/cm at 80 °C. At 120 °C, proton conductivity decreased to poor 0.073 S/cm. The result indicated that composite membranes exhibited high proton conductivity at high temperature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1967–1978, 2006  相似文献   

17.
We synthesized the isomeric polyimides, 6FDA-m-DDS and 6FDA-p-DDS, and investigated the gas selectivity of the asymmetric polyimide membranes with an oriented surface skin layer. Particularly, we focused on the effect of the chemical structure of the polyimide on the molecular orientation. The asymmetric membranes with the oriented skin layer were prepared by a dry–wet phase inversion process at different shear stresses. The gas permeances of the asymmetric polyimide membranes were measured using a high vacuum apparatus with a Baratron absolute pressure gauge at 76 cmHg. The molecular orientation in the asymmetric polyimide membranes was measured using polarized ATR–FTIR spectroscopy. The gas selectivity of the asymmetric 6FDA-m-DDS membrane increased with an increased in the shear stress and were greater than that of the dense membrane. In contrast, the gas selectivities of the asymmetric 6FDA-p-DDS membrane did not depend on the shear stress and were similar to those of the dense membrane. We clarified that a parallel oriented surface formed on the asymmetric 6FDA-m-DDS membrane caused the enhanced gas selectivity of the membrane.  相似文献   

18.
In our recent study, an ABA amphiphilic triblock copolymer poly(vinyl pyrrolidone)‐b‐poly(methyl methacrylate)‐b‐poly(vinyl pyrrolidone) (PVP‐b‐PMMA‐b‐PVP) was synthesized and directly blended with polyethersulfone (PES) to prepare membranes. To further investigate the effects of surface energy and miscibility on the near‐surface composition profile of the membranes, evaporation membrane and phase inversion membrane of PES/PVP‐b‐PMMA‐b‐PVP were prepared by evaporating the solvent in a vacuum oven, and by a liquid–liquid phase separation technique, respectively. The surface composition and morphology of the membranes were investigated using XPS and tapping mode atomic force microscopy, and the surface segregations of the membranes were compared and discussed. For the evaporation membrane, PVP blocks were buried below the lower surface energy PMMA blocks and PES substrate at the airside surface. For the phase inversion membrane, however, the hydrophilicity of PVP blocks were the biggest driving force because of the high speed exchange between water and solvent, and present at the membrane surface. Thus, the modified PES membrane prepared by using phase inversion method has a layer of PVP block brushes on its surface and has the better anticoagulant property, which might improve the blood compatibility of the membrane and has potential to be used in blood purification. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

19.
In this research a series of pore‐filling electrolyte membranes were prepared, based on a sulfonated and hydrogenated styrene/butadiene block copolymer (SHSBS) and plasma‐treated microporous polyethylene (PE) membranes. The pore‐filling electrolyte membranes were characterized by means of scanning electronic microscopy (SEM), infrared spectroscopy (FTIR‐ATR), and dynamic mechanical analysis (DMA). In addition, the water uptake and methanol/water uptake capacities of these membranes were determined using several methanol in water solutions, as well as the permeability coefficients, for both water and methanol, using a 2 M methanol in water solution and pure methanol. Finally, electrical behavior was recorded by means of electrochemical impedance spectroscopy (EIS) and the four probe technique (FPT). The SEM images recorded show good coating of the pore‐filling electrolyte membranes on the plasma‐treated PE matrices, and DMA shows the proper relaxations of the two components: PE and SHSBS. Furthermore, the methanol/water absorption capacity was observed to diminish with plasma treatment of the matrix. Methanol permeability of the pore‐filling electrolyte membranes is notably lower than that of the Nafion® membrane, ion conductivity moving in the order of 10−2 S cm−1. Both of these characteristics qualify the experimental membranes as candidates to be applied as proton exchangers in fuel cells (FCs). © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1684–1695, 2008  相似文献   

20.
The miscibility and underlying hydrogen‐bonding interactions of blends of a fluorinated copolymer containing pyridine and a nonfluorinated copolymer containing methacrylic acid were studied with differential scanning calorimetry (DSC), transmission Fourier transform infrared (TX‐FTIR) spectroscopy, and X‐ray photoelectron spectroscopy (XPS), whereas the surface properties of the blends were investigated with contact‐angle measurements, time‐of‐flight secondary‐ion mass spectroscopy, XPS, and attenuated total reflectance Fourier transform infrared spectroscopy. DSC studies showed that the presence of a sufficient amount of 4‐vinylpyridine units in the fluorinated copolymer produced miscible blends with the nonfluorinated copolymer containing methacrylic acid. TX‐FTIR and XPS showed the existence of pyridine–acid interpolymer hydrogen‐bonding interactions. Even though the anchoring effect of hydrogen bonding hindered the migration of the fluorinated component to the blend surface, it could not completely eliminate the surface enrichment of the fluorinated component and the surface rearrangement of the fluorinated pendant chain. The air–blend interface was mainly occupied by the fluorinated pendant chain, and the surface energies of the blends were extremely low, even with only 1.5 wt % of the fluorinated component in the blends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1145–1154, 2004  相似文献   

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