Preparation and hydrogen permeation properties of BaCe_(0.95)Nd_(0.05)O_(3-δ) membranes

Dense mixed proton and electron conducting membrane made of BaCe_(0.95)Nd_(0.05)O_(3-δ)(BCNd5)was prepared by pressing followed by sintering.X-ray diffraction(XRD)was used to characterize the phase structure of both the powder and the sintered membranes.The microstructure of the sintered membranes was studied by scanning electron microscopy(SEM).Hydrogen permeation through the BCNd5 membrane was studied using a high temperature permeator.The hydrogen permeation fluxes under wet conditions are higher than those under dry conditions,which is due to H~ hopping via surface OH groups.At 925℃,a hydrogen permeation flux of 0.02 mL/min cm~2 was obtained under wet condition,which recommends BCNd5 as a potential material for hydrogen-selective membranes.     

Novel SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) membrane for hydrogen separation

<正>Dense ceramic membranes with protonic and electronic conductivity have attracted considerable interest in recent years.In this paper,the powders of SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) were synthesized via the liquid citrate method,and the membranes of SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) were prepared by pressing followed by sintering.X-ray diffraction(XRD) was used to characterize the phase structure of both the powder and sintered membrane.The microstructure of the sintered membranes was studied by scanning electron microscopy(SEM).Hydrogen permeation through the SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) membranes was carried out using gas permeation setup at 900℃.Hydrogen permeation flux of SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) membrane reaches up to 0.042 mL/ min cm~2 at H_2 partial pressure of 0.4 atm.The hydrogen permeation fluxes obtained in this paper are similar to that of SrCe_(0.95)Tm_(0.05)O_(3-δ),and Zr doping can increase mechanical strength of SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) membranes and the resistance to reducing circumstance.     

Preparation and thermal treatment of Pd/Ag composite membrane on a porous alumina tube by sequential electroless plating technique for H2 separation

Pd/Ag/α-Al2O3 composite membranes were prepared by sequential electroless plating technique. The prepared membranes were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive spectroscopy, and inductively coupled plasma atomic emission spectroscopy techniques （ICP-AES）. Effects of annealing time, Ag content, and air treatment on the hydrogen permeation flux and morphology of the alloys were investigated. The results of the investigation showed that the prepared type of tube had a good potential as substrate for membrane preparation. In addition, a uniform defect-free alloy was prepared by annealing at 550 ℃ in H2 atmosphere. The permeation results showed an increase in H2 permeation flux by increasing the Ag content and the annealing time. In addition, the air treatment of the prepared membranes at 400 ℃ for 1 h changed the morphology of the alloy and substantially enhanced the hydrogen flux.     

Hydrophilic nanofiltration membranes with self-polymerized and strongly-adhered polydopamine as separating layer

Inspired by the self-polymerization and strong adhesion characteristics of dopamine in aqueous conditions,a novel hydrophilic nanofiltration（NF） membrane was fabricated by simply dipping polysulfone（PSf） ultrafiltration（UF） substrate in dopamine solution.The changes in surface chemical composition and morphology of membranes were determined by Fourier transform infrared spectroscopy（FTIR-ATR）,X-ray photoelectron spectroscopy（XPS）,scanning electron microscopy（SEM） and atomic force microscopy（AFM）.The experimental results indicated that the self-polymerized dopamine formed an ultrathin and defect-free barrier layer on the PSf UF membrane.The surface hydrophilicity of membranes was evaluated through water contact angle measurements.It was found that membrane hydrophilicity was significantly improved after coating a polydopamine（pDA） layer,especially after double coating.The dyes filtration experiments showed that the double-coated membranes were able to reject completely the dyes of brilliant blue,congo red and methyl orange with a pure water flux of 83.7 L/（m²·h） under 0.6 MPa.The zeta potential determination revealed the positively-charged characteristics of PSf/pDA composite membrane in NF process.The salt rejection of the membranes was characterized by 0.01 mmol/L of salts filtration experiment.It was demonstrated that the salts rejections followed the sequence:NaCl2SO₄422,and the rejection to CaCl₂ reached 68.7%.Moreover,the composite NF membranes showed a good stability in water-phase filtration process.     

Electrospinning Preparation of β-Cyclodextrin/Glutaraldehyde Crosslinked PVP Nanofibrous Membranes to Adsorb Dye in Aqueous Solution

The insoluble β-cyclodextrin/glutaraldehyde crosslinked polyvinylpyrrolidone nanofibrous membranes were prepared by electrospinning technique. The membranes were extensively characterized by various techniques including attenuated total reflectance Fourier transform infrared spectroscopy（ATR-FTIR）, X-ray diffraction（XRD）, scanning electron microscopy（SEM） and UV-visible absorption to correlate membrane characteristics with their performance. The adsorption ability of the nanofibrous membranes was tested by performing extraction of Methyl orange（MO） dye in water. It was observed that β-cyclodextrin incorporated in polyvinylpyrrolidone provided the characteristics of high adsorption capacity of polyvinylpyrrolidone. Results of sorption experiments show that the nanofibrous membranes exhibited an adsorption rate of more than 95% for MO and the MO absorbent was 39.82 mg to per gram of fl-cyclodextrin glutaraldehyde（β-CDXFM） crosslinked PVP under the optimized experimental conditions.     

Polymerizable ionic liquid copolymer P(MMA-co-BVIm-Br) and its effect on the surface wettability of PVDF blend membranes

Polymerizable ionic liquid copolymer P(MMA-co-BVIm-Br) was synthesized by radical polymerization technique, and characterized by Fourier transform infrared spectrometry(FTIR), 1H Nuclear magnetic resonance(1H-NMR) and gel permeation chromatography(GPC). The resulting copolymer was used to prepare poly(vinylidene fluoride)(PVDF) blend membranes via a phase inversion method. The effects of the copolymer on the polymorphism, surface wettability and zeta potential(ζ) of the blend membranes were investigated by ATR-FTIR, contact angle instrument and zeta potential analyzer. Scanning electron microscopy(SEM and SEM-EDS) was also applied to investigate the morphology and the surface element changes of the fabricated membranes. The results indicated that P(MMA-co-BVIm-Br) copolymer existed on the surface of the membrane which made the blend membrane have a positive surface during the experimental p H range. The copolymer was also in favor of the formation of β crystal phase in PVDF membranes. The contact angle experiment indicated that P(MMA-co-BVIm-Br) copolymer could switch the wettability of the blend membranes from hydrophilic to hydrophobic by exchanging Br-anion with PF-6. Compared with pure PVDF membranes, the water flux and water recovery flux of the blend membranes were enhanced obviously. The results from the flux recovery ratio(FR) and total fouling ratio(Rt) all suggested that the blend membranes had good anti-fouling properties.     

Preparation of high density polyethylene/polyethylene-block-poly(ethylene glycol) copolymer blend porous membranes via thermally induced phase separation process and their properties

<正>High density polyethylene(HDPE)/polyethylene-block-poly(ethylene glycol)(PE-b-PEG) blend porous membranes were prepared via thermally induced phase separation(TIPS) process using diphenyl ether(DPE) as diluent.The phase diagrams of HDPE/PE-b-PEG/DPE systems were determined by optical microscopy and differential scanning calorimetry(DSC).By varying the content of PE-b-PEG,the effects of PE-b-PEG copolymer on morphology and crystalline structure of membranes were studied by scanning electron microscopy(SEM) and wide angle X-ray diffraction(WAXD). The chemical compositions of whole membranes and surface layers were characterized by elementary analysis,Fourier transform infrared spectroscopy-attenuated total reflection(FTIR-ATR) and X-ray photoelectron spectroscopy(XPS).Water contact angle,static protein adsorption and water flux experiments were used to evaluate the hydrophilicity,antifouling and water permeation properties of the membranes.It was found that the addition of PE-b-PEG increased the pore size of the obtained blend membranes.In the investigated range of PE-b-PEG content,the PEG blocks could not aggregate into obviously separated domains in membrane matrix.More importantly,PE-b-PEG could not only be retained stably in the membrane matrix during membrane formation,but also enrich at the membrane surface layer.Such stability and surface enrichment of PE-b-PEG endowed the blend membranes with improved hydrophilicity,protein absorption resistance and water permeation properties,which would be substantially beneficial to HDPE membranes for water treatment application.     

Fabrication and evaluation of molecularly imprinted regenerated cellulose composite membranes via atom transfer radical polymerization

A simple and effective method for surface molecularly imprinted composite membranes （MICMs） for artemisinin （Ars） based on regenerated cellulose membranes was first prepared through surface- initiated atom transfer radical polymerization （ATRP）, and the as-prepared MICMs were then evaluated as adsorbents for selective recognition and separation of Ars molecules. Batch rebinding studies were conducted to determine the specific adsorption equilibrium, kinetics and selective permeation performance. The adsorption capacity of MICMs toward Ars by the Langmuir isotherm model was 2.008 mgg-1, which was nearly 5.0 times higher than non-molecularly imprinted composite membranes （NICMs）. The kinetic property of MICMs was well-fitted by the pseudo-second-order rate equation. The selective permeation experiments were successfully investigated to prove the excellent selective permeation performance for Ars than the competitive analog （artemether）.     

Thermo-responsive and antifouling PVDF nanocomposited membranes based on PNIPAAm modified TiO2 nanoparticles

A novel hydrophilic nanocomposite additive(TiO2-g-PNIPAAm) was synthesized by the surface modification of titanium dioxide(TiO2) with N-isopropylacrylamide(NIPAAm) via "graft-from" technique. And the nanocomposite membrane of poly(vinylidene fluoride)(PVDF)/TiO2-g-PNIPAAm was fabricated by wet phase inversion. The graft degree was obtained by thermo-gravimetric analysis(TGA). Fourier transform infrared attenuated reflection spectroscopy(FTIR-ATR) and X-ray photoelectronic spectroscopy(XPS) characterization results suggested that TiO2-g-PNIPAAm nanoparticles segregated on membrane surface during the phase separation process. Scanning electron microscopy(SEM) was conducted to investigate the surface and cross-section of the modified membranes. The water contact angle measurements confirmed that TiO2-g-PNIPAAm nanoparticles endowed PVDF membranes better hydrophlilicity and thermo-responsive properties compared with those of the pristine PVDF membrane. The water contact angle decreased from 92.8° of the PVDF membrane to 61.2° of the nanocompostie membrane. Bovine serum albumin(BSA) static and dynamic adsorption experiments suggested that excellent antifouling properties of membranes was acquired after adding TiO2-gPNIPAAm. The maximum BSA adsorption at 40 °C was about 3 times than that at 23 °C. The permeation experiments indicated the water flux recover ratio and BSA rejection ratio were improved at different temperatures.     

Degradation Mechanism of Phenol in C/PTFE O2-Fed Cathode by Determining the Product of Oxygen Electroreduction

A terylene membrane which kept pH〉12 in cathode compartment was used to construct a divided cell with a carbon/polytetrafluoroethylene（C/PTFE） O2-fed cathode. The concentrations of hydrogen peroxide （H2O2） and hydroxyl radical （HO^-）in the catholyte were 8.3 mg/L and 2.15 μmol/L, respectivel.y, which were determined by permanganate titration, electron spin resonance （ESR） spectrum and the fluorescence spectra. ;The efficiency of the removal of phenol achieved 100% as a result of these two kinds of stronger oxidizer.     

Partial oxidation of methane in Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3-δ ceramic membrane reactor

Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3δ(BSCFNiO) perovskite oxides were synthesized using a combined EDTA-citrate complexation method,and then pressed into disk and applied in a membrane reactor.The performance of the BSCFNiO membrane reactor was studied for partial oxidation of methane over Ni/α-Al 2 O 3 catalyst.The time dependence of oxygen permeation rate and catalytic performance of BSCFNiO membrane during the catalyst initiation stage were investigated at 850 C.In unsteady state,oxygen permeation rate,methane conversion and CO selectivity were closely related to the state of the catalyst.After 300 min from the initial time,the reaction condition reached to steady state and oxygen permeation rate were obtained about 11.7cm 3 cm 2 min 1.Also,the performance of membrane reactor was studied at the temperatures between 750 and 950 C.The results demonstrated good performance for the membrane reactor,as CH 4 conversion and CO selectivity permeation rate reached 98% and 97.5%,respectively,and oxygen permeation rate was about 14.5 cm 3 cm 2 min 1 which was 6.8 times higher than that of air-helium gradient.Characterization of membrane surface by SEM after reaction showed that the original grains disappeared on both surfaces exposed to the air and reaction side,but XRD profile of the polished surface membrane indicated that the membrane bulk preserved the perovskite structure.     

Preparation and oxygen permeation properties of SrFe（Cu）O3-δ dense ceramic membranes

Mixed oxygen-ionic and electronic conducting membranes of SrFe(Cu)O3−δ were prepared by solid-state reaction method. The crystal structure, oxygen nonstoichiometry, and phase stability of the materials were studied by TGA and XRD. Oxygen permeation fluxes through these membranes were studied at operating temperature ranging from 750 to 950 ℃. Results showed that doping Cu in SrFeO3−δ compound had a significant effect on the formation of single-phased perovskite structure. For SrFe1−xCuxO3−δ series materials, the oxygen nonstoichiometry and the oxygen permeation flux increased considerably with the increase of Cu-doping content (x = 0.1–0.3). The sintering property of the membrane decreased significantly when the Cu substitution amount reached 40%. SrFe0.7Cu0.3O3−δ showed high oxygen permeation flux, but SrCuO2 and Sr2Fe2O5 phases formed in the compound after oxygen permeation test induced cracks in the membrane.     

Immobilization and Properties of Lipase from Candida rugosa on Electrospun Nanofibrous Membranes with Biomimetic Phospholipid Moities

Reported here is a protocol to fabricate a biocatalyst with high enzyme loading and activity retention, from the conjugation of electrospun nanofibrous membrane having biomimetic phospholipid moiety and lipase. To improve the catalytic efficiency and activity of the immobilized enzyme, poly（acrylonitrile-co-2-methacryloyloxyethyl phosphorylcholine）s（PANCMPCs） were, respectively, electrospun into nanofibrous membranes with a mean diameter of 90 nm, as a support for enzyme immobilization. Lipase from Candida rugosa was immobilized on these nanofibrous membranes by adsorption. Properties of immobilized lipase on PANCMPC nanofibrous membranes were compared with those of the lipase immobilized on the polyacrylonitrile（PAN） nanofibrous and sheet membranes, respectively. Effective enzyme loading on the nanofibrous membranes was achieved up to 22.0 mg/g, which was over 10 times that on the sheet membrane. The activity retention of immobilized lipase increased from 56.4% to 76.8% with an increase in phospholipid moiety from 0 to 9.6%（molar fraction） in the nanofibrous membrane. Kinetic parameter Km was also determined for free and immobilized lipase. The Km value of the immobilized lipase on the nanofibrous membrane was obviously lower than that on the sheet membrane. The optimum pH was 7.7 for free lipase, but shifted to 8.3-8.5 for immobilized lipases. The optimum temperature was determined to be 35 ℃ for the free enzyme, but 42-44℃ for the immobilized ones, respectively. In addition, the thermal stability, reusability, and storage stability of the immobilized lipase were obviously improved compared to the free one.     

Activation in the initial stage of oxygen permeation in SrCo0.9Ta0.1O3-δ

Mixed conducting perovskite oxide SrCo_0.9Ta_0.1O_3-δ（SCT） is synthesized by solid-state reaction method.The activation in the initial stage of oxygen permeation through the SCT membrane is investigated.The results show that the activation in the initial stage of oxygen permeation has activate-memory,the first activation can only help to reduce active time of the next cycles,but it is helpless to increase the final oxygen permeation flux.XRD characterization shows that the imperfect perovskite phase structure is gradually improved and the crystal lattice has made some self-adjustment under the permeation conditions,therefore,the oxygen permeation flux of SCT disk membrane increases gradually and till it reaches a steady state.     

Effect of solution extrusion rate on morphology and performance of polyvinylidene fluoride hollow fiber membranes using polyvinyl pyrrolidone as an additive

<正>Polyvinylidene fluoride(PVDF) hollow fiber membranes prepared from spinning solutions with different polyvinyl pyrrolidone(PVP) contents(1%and 5%) at different extrusion rates were obtained by wet/dry phase process keeping all other spinning parameters constant.In spinning these PVDF hollow fibers,dimethylacetamide(DMAc) and PVP were used as a solvent and an additive,respectively.Water was used as the inner coagulant.Dimethylformamide(DMF) and water(30/70) were used as the external coagulant.The performances of membranes were characterized in terms of water flux,solute rejection for the wet membranes.The structure and morphology of PVDF hollow fiber were examined by BET adsorption,dry/wet weight method and scanning electron microscopy(SEM).It is found that the increase in PVP content and extrusion rate of spinning solution can result in the increase of water flux and decrease of solute rejection.The improvements of interconnected porous structure and pore size are induced by shear-thinning behavior of spinning solution at high extrusion rates,which could result in the increase of water flux of hollow fiber membranes.The increase of extrusion rate also leads to the increase of membrane thickness due to the recovery effect of elastic property of polymer chains.     

氟胞嘧啶与牛血清白蛋白结合反应研究

The binding of flucytosine to bovine serum albumin （BSA） was studied by means of fluorescence and absorption spectra under the conditions of simulant clay physiology. It showed a powerful ability to quench the fluorescence launching from BSA. After analyzing the fluorescence quenching data by Stem-Volmer equation and Lineweaver-Burk double-reciprocal equation, it was found that they matched the latter better and so they belonged to static quenching. The binding constant was calculated to be 5.710 × 10^3 L·mol^-1 at 297 K. The binding locality was a distance 2.49 nm away from tryptophan residue-212 based on Foster＇s non-radiation energy transfer mechanism. The binding power is mainly the hydrogen bond and van der Waals force according to the thermodynamic parameters. The information of BSA conformation was acquired by synchronous fluorescence spectrum and three-dimensional fluorescence spectrum.     

Preparation and pervaporation performance of high-quality silicalite-1 membranes

High-performance silicalite-1 membranes were successfully synthesized on novel porous silica tubes by two-step in-situ hydrothermal synthesis.The flux and separation factor towards ethanol/water mix- ture at 60℃were 0.56 kg/(m2·h)and 84,respectively.The as-synthesized silicalite-1 membranes were characterized by scanning electron microscopy(SEM).The influence of different synthesis conditions on the separation performance of the silicalite-1 membranes was investigated.It was found that the average flux of silicalite-1 membranes was improved by about 26?ter filling the silica tubes with mixed solution containing glycerol and water.After calcinating at 400℃for 5 h repeatedly,membrane synthesized on silica tube still showed high pervaporation performance towards ethanol/water mixture even at a calcination rate of 4℃/min,which suggested that silica support was more suitable for pre- paring high-performance silicalite-1 membranes.     

An ethanol biosensor based on a bacterial cell-immobilized eggshell membrane

An ethanol biosensor was fabricated based on a Methylobacterium organophilium-immobilized eggshell membrane and an oxygen（O₂） electrode.A linear response for ethanol was obtained in the range of 0.050-7.5 mmol/L with a detection limit of 0.025 mmol/L（S/N= 3） and a R.S.D.of 2.1%.The response time was less than 100 s at room temperature and ambient pressure. The optimal loading of bacterial cells on the biosensor membrane is 40 mg（wet weight）.The optimal working conditions for the microbial biosensor are pH 7.0 phosphate buffer（50 mmol/L） at 20-25℃.The interference test,operational and storage stability of the biosensor are studied in detail.Finally,the biosensor is applied to determine the ethanol contents in various alcohol samples and the results are comparable to that obtained by gas chromatographic method and the results are satisfactory.Our proposed biosensor provides a convenient,simple and reliable method to determine ethanol content in alcoholic drinks.     

CHARACTERIZATION OF REGENERATED CELLULOSE MEMBRANES HYDROLYZED FROM CELLULOSE ACETATE

A series of cellulose acetate membranes were prepared by using formamide as additive, and then were hydrolyzedin 4 wt% aqueous NaOH solution for 8 h to obtain regenerated cellulose membranes. The dependence of degree ofsubstitution, structure, porous properties, solubility and thermal stability on hydrolysis time was studied by chemical titration,Fourier transform infrared spectroscopy, scanning electron microscopy, wide-angle X-ray diffraction, and differentialscanning calorimetry, respectively. The results indicated that the pore size of the regenerated cellulose membranes wasslightly smaller than that of cellulose acetate membrane, while solvent-resistance, crystallinity and thermostability weresignificantly improved. This work provides a simple way to prepare the porous cellulose membranes, which not only kept thegood pore characteristics of cellulose acetate membranes, but also possessed solvent-resistance, high crystallinity andthermostability. Therefore, the application range ofcellulose acetate membranes can be expanded.     

Morphology Evolution of Poly（vinylidene fluoride） Membranes during Supercritical CO2 Assisted Phase Inversion

A supercritical carbon dioxide（Sc CO2） assisted phase inversion was developed to produce microporous poly（vinylidene fluoride）（PVDF） membranes whose morphology characteristics arise from both liquid-liquid demixing and solid-liquid demixing（crystallization）. This result was confirmed by Fourier transform infrared spectroscopy（FTIR）, from which both α and β crystals were found. As revealed by contact angle experiment, the PVDF membranes prepared via Sc CO2 assisted phase inversion were more hydrophobic compared with the control membrane produced via conventional immersionprecipitation technique. In particular, the sample with 15 wt% PVDF prepared at 45 °C and 13 MPa exhibited a contact angle of 142°, which was mainly caused by the multilevel micro- and nano- structure. The effects of polyethylene glycol（PEG）, polyvinyl pyrrolidone（PVP） and lithium chloride（Li Cl） on the structures and crystal form were investigated. PVP promoted the formation of β phase crystal form, while PEG boosts the evolution of α phase. Li Cl restrained the crystallization degree of PVDF membrane under Sc CO2.