Gradient nanoporous phenolics as substrates for high-flux nanofiltration membranes by layer-by-layer assembly of polyelectrolytes

Thin film composite(TFC) membranes represent a highly promising platform for efficient nanofiltration(NF)processes. However, the improvement in permeance is impeded by the substrates with low permeances. Herein,highly permeable gradient phenolic membranes with tight selectivity are used as substrates to prepare TFC membranes with high permeances by the layer-by-layer assembly method. The negatively charged phenolic substrates are alternately assembled with polycation polyethylenimine(PEI) and polyanion poly(acrylic acid)(PAA)as a result of electrostatic interactions, forming thin and compact PEI/PAA layers tightly attached to the substrate surface. Benefiting from the high permeances and tight surface pores of the gradient nanoporous structures of the substrates, the produced PEI/PAA membranes exhibit a permeance up to 506 L? m~(-2)?h~(-1)?MPa~(-1), which is ～2–10 times higher than that of other membranes with similar rejections. The PEI/PAA membranes are capable of retaining N 96.1% of negatively charged dyes following the mechanism of electrostatic repulsion. We demonstrate that the membranes can also separate positively and neutrally charged dyes from water via other mechanisms.This work opens a new avenue for the design and preparation of high-flux NF membranes, which is also applicable to enhance the permeance of other TFC membranes.     

CO2通过合成聚合物膜的促进传递

Two kinds of fixed carrier membrane materials containing secondary amine and carboxyl groups which can be used as carriers of CO2 were prepared. One was poly(N-vinyl-7-sodium aminobutyrate)(PVSA), which was obtained through the hydrolysis of polyvinylpyrrolidone (PVP) synthesized with N-vinylpyrrolidone(NVP) by radical polymerization. The other was poly(N-vinyl-7-sodium aminobutyrate-co-sodium acrylate)(VSA-SA), which was obtained through the hydrolysis of copolymer of N-vinylpyrrolidone and acrylamide(AAm) (NVP-AAm). The composite membranes were developed with PVSA or VSA-SA as active layer and polysulfone (PS) as support membranes. The permeation rates of pure CO2 and CH4 gas as well as binary mixtures of CO2/CH4 through the composite membranes were measured. The results show that the composite membranes present better CO2 permeation rates than other fixed carrier membranes do reported in literature. For example, at 26℃, 1330 Pa of CO2 pressure, the PVSA/PS composite membrane displays a CO2 permeation     

添加剂和凝结剂温度对用无溶剂致相位分离法生产高性能PVDF/聚醚F127混合中空光纤膜的影响(英文)

Poly(vinylidene fluoride)(PVDF) has become one of the most popular materials for membrane prepara-tion via nonsolvent induced phase separation(NIPS) process.In this study,an amphiphilic block copolymer,Plu-ronic F127,has been used as both a pore-former and a surface-modifier in the fabrication of PVDF hollow fiber membranes to enhance the membrane permeability and hydrophilicity.The effects of 2nd additive and coagulant temperature on the formation of PVDF/Pluronic F127 membranes have also been investigated.The as-spun hollow fibers were characterized in terms of cross-sectional morphology,pure water permeation(PWP),relative molecular mass cut-off(MWCO),membrane chemistry,and hydrophilicity.It was observed that the addition of Pluronic F127 significantly increased the PWP of as-spun fibers,while the membrane contact angle was reduced.However,the size of macrovoids in the membranes was undesirably large.The addition of a 2nd additive,including lithium chlo-ride(LiCl) and water,or an increase in coagulant temperature was found to effectively suppress the macrovoid for-mation in the Pluronic-containing membranes.In addition,the use of LiCl as a 2nd additive also further enhanced the PWP and hydrophilicity of the membranes,while the surface pore size became smaller.PVDF hollow fiber with a PWP as high as 2530 L?m?2?h?1?MPa?1,a MWCO of 53000 and a contact angle of 71° was successfully fabricated with 3%(by mass) of Pluronic F127 and 3%(by mass) of LiCl at a coagulant temperature of 25 °C,which shows better performance as compared with most of PVDF hollow fiber membranes made by NIPS method.     

CO2通过合成聚合物膜的促进传递

Two kinds of fixed carrier membrane materials containing secondary amine and carboxyl groups whichcan be used as carriers of CO2 were prepared. One was poly(N-vinyl-γ-sodium aminobutyrate)(PVSA), whichwas obtained through the hydrolysis of polyvinylpyrrolidone (PVP) synthesized with N-vinylpyrrolidone(NVP) byradical polymerization. The other was poly(N-vinyl-γ-sodium aminobutyrate-co-sodium acrylate)(VSA-SA), whichwas obtained through the hydrolysis of copolymer of N-vinylpyrrolidone and acrylamide(AAm) (NVP-AAm). Thecomposite membranes were developed with PVSA or VSA-SA as active layer and polysulfone (PS) as supportmembranes. The permeation rates of pure CO2 and CH4 gas as well as binary mixtures of CO2/CH4 throughthe composite membranes were measured. The results show that the composite membranes present better CO2permeation rates than other fixed carrier membranes do reported in literature. For example, at 26℃, 1330 Pa of CO2pressure, the PVSA/PS composite membrane displays a CO2 permeation rate of 5.95 × 10-7 cm3.cm-2.s-1.pa-1with CO2/CH4 ideal separation factor of 212.1. At 20℃, 6400Pa of CO2 pressure, the VSA-SA/PS compositemembrane displays a CO2 permeation rate of 4.24 × 10-8 cm3@cm-2.s-1.Pa-1 with CO2/CH4 ideal separationfactor of 429.7. The results with the gas mixtures are not as good as those obtained with pure gas because ofthe coupling effects between CO2 and CH4. The heat cross-linked membrane shows good separation factor due todensification of the polymer.     

Fabrication of graphene oxide composite membranes and their application for pervaporation dehydration of butanol

As a new kind of 2D nanomaterials, graphene oxide (GO) with 2–4 layers was fabricated via a modified Hummers method and used for the preparation of pervaporation (PV) membranes. Such GO membranes were prepared via a facile vacuum-assisted method on anodic aluminium oxide disks and applied for the dehydration of butanol. To obtain GO membranes with high performance, effects of pre-treatments, including high-speed centrifugal treat-ment of GO dispersion and thermal treatment of GO membranes, were investigated. In addition, effects of oper-ation conditions on the performance of GO membranes in the PV process and the stability of GO membranes were also studied. It is of benefit to improve the selectivity of GO membrane by pre-treatment that centrifuges the GO dispersion with 10000 r·min?1 for 40 min, which could purify the GO dispersion by removing the large size GO sheets. As prepared GO membrane showed high separation performance for the butanol/water system. The separation factor was 230, and the permeability was as high as 3.1 kg·m?2·h?1 when the PV temperature was 50 °C and the water content in feed was 10%(by mass). Meanwhile, the membrane still showed good stabil-ity for the dehydration of butanol after running for 1800 min in the PV process. GO membranes are suitable candidates for butanol dehydration via PV process.     

溶胶-凝胶法制备H3PW12O40/SiO2及催化合成三羟甲基丙烷三庚酸酯

H3PW12O40/SiO2 (PW/SiO2) was prepared by the sol-gel method and trimethylolpropane triheptanoate (TMH) was synthesized by trimethylolpropane (TMP) and heptylic acid (HA) in the presence of H3PW12O40/SiO2. The results showed that the catalyst with 50% (mass) PW had good activity and stability. The optimal esterification conditions were as follows: nTNP：nHA = 1：4, 2%(mass) PW/SiO2, reaction temperature 120-200℃ and 3 h. The structure of TMH was characterized by GC, IR, ^1HNMR spectra and the rate of esterification was up to 95%.     

Fabrication of poly(vinylidene fluoride) membrane via thermally induced phase separation using ionic liquid as green diluent

Ionic liquid(IL), 1-butyl-3-methylimidazolium hexafluorophosphate([BMIM]PF6) as a new and environmentally friendly diluent was introduced to prepare poly(vinylidene fluoride)(PVDF) membranes via thermally induced phase separation(TIPS). Phase diagram of PVDF/[BMIM]PF6 was measured. The effects of polymer concentration and quenching temperature on the morphologies, properties, and performances of the PVDF membranes were investigated. When the polymer concentration was 15 wt%, the pure water flux of the fabricated membrane was up to nearly 2000 L·m~(-2)·h~(-1), along with adequate mechanical strength. With the increasing of PVDF concentration and quenching temperature, mean pore size and water permeability of the membrane decreased. SEM results showed that PVDF membranes manufactured by ionic liquid(BMIm PF6) presented spherulite structure. And the PVDF membranes were represented as β phase by XRD and FTIR characterization. It provides a new way to prepare PVDF membranes with piezoelectric properties.     

Partial pore blockage and polymer chain rigidification phenomena in PEO/ZIF-8 mixed matrix membranes synthesized by in situ polymerization

Nanostructured zeolitic imidazolate frameworks(ZIF-8) was incorporated into the mixture of poly(ethylene glycol) methyl ether acrylate(PEGMEA) and pentaerythritol triacrylate(PETA) to synthesize mixed matrix membranes(MMMs) by in situ polymerization for CO_2/CH_4 separation. The solvent-free polymerization between PEGMEA and PETA was induced by UV light with 1-hydroxylcyclohexyl phenyl ketone as initiator. The chemical structural characterization was performed by Fourier transform infrared spectroscopy. The morphology was characterized by scanning electron microscope. The average chain-to-chain distance of the polymer chains in MMMs was investigated by X-ray diffraction. The thermal property was evaluated by differential scanning calorimetry. The CH_4 and CO_2 gas transport properties of MMMs are reported. The relationship between gas permeation–separation performances or physical properties and ZIF-8 loading is also discussed. However, the permeation–separation performance was not improved in Robeson upper bound plot compared with original polymer membrane as predicted. The significant partial pore blockage and polymer rigidification effect around the ZIFs confirmed by the increase in glass temperature and the decrease in the d-spacing, were mainly responsible for the failure in performance improvement, which offset the high diffusion induced by porous ZIF-8.     

乙二胺四乙酸四钠盐缓释微胶囊的制备与表征

The microcapsules with cores of ethylenediamine tetraacetic acid tetrasodium salt (Na4-EDTA) and walls of polyurea were synthesized via an interfacial polycondensation reaction with 2,4-tolylene diisocyanate as an oil-soluble monomer and diethyl triamine as a water-soluble monomer. Various manufacturing parameters, including the amount of emulsifier, agitation speed, stirring time and ratios of the wall materials to core materials, were altered to optimize process variables during the synthesis of microcap-sules, and the effects of these parameters on the characteristics of the microcapsules were examined. The structure, morphology, mean particle size and size distribution were characterized by optical microscope and scanning electron microscopy (SEM), showing that the mean diameter of optimal microspheres was approximately 6 μm, and microcapsules were spherical. In vitro release of Na4-EDTA from these microcapsules was performed in distilled water. Under the optimal preparation conditions, the Na4-EDTA re-lease profiles were biphasic with a burst release followed by a gradual release phase. After an initial burst, a continuous Na4-EDTA release was up to 5-7 days. The optimal synthesis conditions for the microcapsules with stable, good morphology and good con-trolled-release properties were as follows: emulsifier Span-80 10% (by mass), agitation speed 900 r&;#8226;min－1, stirring time 30 min, and the ratio of the wall materials to core materials 0.15.     

热带假丝酵母不对称还原3,5-双三氟甲基苯乙酮制备手性醇(英文)

(S)-3,5-bistrifluoromethylphenyl ethanol is a key chiral intermediate for the synthesis of NK-1 receptor antagonists. Enantioselective synthesis of (S)-3,5-bistrifluoromethylphenyl ethanol was successfully performed in high enantiomeric excess (e.e.) through asymmetric reduction of 3,5-bis(trifluoromethyl) acetophenone catalyzed by Candida tropicalis 104 cells. The influence of some key reaction parameters such as substrate concentration, co-substrate and its concentration, biomass and reaction time was examined, respectively. The results showed that these factors obviously influence the yield, but the optical purity of the prepared product remains intact. The opti-mum conditions for the preparation of (S)-3,5-bistrifluoromethylphenyl ethanol were found to be as follows: sub-strate concentration 50 mmol?L?1; 50 g·L-1 of maltose as co-substrate; wet cell concentration 300 g·L-1; reaction for 30 h. Under above optimal conditions, the maximum yield for (S)-3,5-bistrifluoromethylphenyl ethanol reached 70.3% with 100% of product e.e.     

Synthesis of 4-Aminobenzoylpiperazine for Preparing the Thin Film Composite Nanofiltration Membrane by Interfacial Polymerization with TMC

A new synthesis method of aromatic diamine, 4-aminobenzoylpiperazine (4-ABP), was studied from 4-aminobenzoic acid and 1-formyl piperazine for the preparation of nanofiltration membrane. The structure of 4-ABP was identified by FT-IR spectra and ¹H NMR spectra. The resulting 4-ABP was used as aqueous monomer to fabricate a thin film on porous polyethersulfone (PES) ultra filtration membranes by interfacial polymerization (IP) with trimesoyl chloride (TMC) as organic monomer. The salt rejection order of these thin film composite (TFC) nanofiltration(NF) membranes is Na₂SO₄>MgSO₄>MgCl₂>NaCl. This sequence indicated that the membranes were negatively charged.     

Separation performance of thin-film composite nanofiltration membrane through interfacial polymerization using different amine monomers

Four kinds of thin-film composite (TFC) membranes were prepared via interfacial polymerization using diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and piperazidine (PIP) as water-soluble monomer, and trimesoyl chloride (TMC) as organic-soluble monomer. The surface chemical features of the resultant membranes were confirmed by contact angle measurement and Fourier transform infrared spectroscopy (FTIR). The membrane morphology and surface charges were investigated through Scanning electronic microscopy (SEM) and Zeta potential, respectively. Salt rejection was used to evaluate the separation performance of the four kinds of TFC membranes. The results showed that all the four kinds of TFC membranes exhibited typical negatively charged nanofiltration membrane characteristics. The salt rejections followed the sequence: Na₂SO₄ > MgSO₄ > MgCl₂ and the rejection of Na₂SO₄ was all over 80%. It was also found that the solubility of water-soluble monomer in organic solvent played an important role in manipulating the membrane structure, charge properties and thus the separation performance.     

Novel thin-film composite nanofiltration membranes fabricated via the incorporation of ssDNA for highly efficient desalination

In this work, the biomacromolecule, single-stranded deoxyribonucleic acid (ssDNA) was innovatively incorporated into the polyamide layer to tailor the permeate flux and antifouling performance of the nanofiltration (NF) membranes. With active amines groups, the ssDNA was as the aqueous phase monomers along with piperazine (PIP), and reacted with trimesoyl chloride on polyethersulfone substrate to fabricate thin-film composite (TFC) NF membranes. The NF membrane prepared under optimal ratio of ssDNA/PIP had a pure water permeability of 75.8 L m⁻² h⁻¹ (improved 58% compared to PIP NF membrane) and Na₂SO₄ rejection of 98.0% at 6.0 bar. The rejections for different inorganic salts were the order: Na₂SO₄ (98.0%) > MgSO₄ (89.2%) > MgCl₂ (72.8%) > NaCl (23.0%). Furthermore, the TFC NF membranes showed good antifouling performance in long-term running with 300 ppm bovine serum albumin and humic acid solution. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 47102.     

氨基化氧化石墨烯界面聚合制备超薄复合纳滤膜

采用氨基化氧化石墨烯（NGO）为界面聚合水相单体,制备了超薄复合纳滤膜。研究采用傅里叶变换红外光谱（FTIR）、X射线光电子能谱（XPS）、透射电子显微镜（TEM）、扫描电子显微镜（SEM）、原子力显微镜（AFM）表征了NGO以及复合纳滤膜的化学组成和形貌。系统考察了水相单体浓度、有机相单体浓度对于制备的超薄复合纳滤膜性能的影响。该超薄复合膜在低压（0.2 MPa）下纯水通量可达27.8 L·m^-2·h^-1,对小分子染料有较高的截留率（甲基橙截留率74.8%,橙黄钠截留率96.0%,刚果红截留率98.5%,甲基蓝截留率99%）,对于无机盐的截留率较低（Na₂SO₄截留率21.4%,MgSO₄截留率10.7%,NaCl截留率5.3%,MgCl₂截留率1.5%）,展现出优异的染料/盐分离性能。同时制备的复合纳滤膜展现了较好的长周期稳定性以及抗污染特性。     

Nanofiltration thin-film-composite polyesteramide membranes based on bulky diols

Polyesteramide thin-film-composite (TFC) membranes have promise for diafiltration applications due to their relatively good oxidative resistance coupled with the ability to tailor the membrane rejection profile by varying the ester/amide ratio. The incorporation ofester linkages in interfaciallyprepared polyesteramide TFC membranes has been previously shown to increase the oxidation resistance of the membrane. It was also found that polyesteramide TFC membranes incorporating hydroquinone (HQ) or bisphenol-A (Bis-A) had high rejection for monovalent salts, i.e., their rejection profiles matched those of reverse osmosis rather than nanofiltration membranes. We report the properties of polyesteramide TFC membranes incorporating bulky diols such as phenolphthalein (Phe) and terabromobisphenol-A (TBrBis-A). The data were used to correlate the influence of different ester fanctionalities on membrane flux and rejection characteristics. Membranes incorporating TBrBis-A had relativelyhigh rejections for monovalent salts coupled with low water permeance. By contrast, membranes incorporating Phe showed 10 times higher flux and a rejection profile which appears to be of interest for diafiltration applications involving the separation of organics with molecular weight >400 grnol⁻¹ from low-molecular-weight organics and salts. The Phe-based membranes show rejection characteristics for monovalent and multivalent salts typical of negatively charged membranes.     

Interfacially polymerized thin film nanofiltration membranes on TiO2 coated polysulfone substrate

In this study, a new approach was developed to prepare the novel thin film composite nanofiltration membranes. In this new approach, nanoparticles were coated completely under the polymeric thin film layer. Thin film composite (TFC) membranes were fabricated by interfacial polymerization on polysulfone (PSf) sublayer using m-phenylenediamine (MPD) and trimesoyl chloride (TMC) respectively as amine monomer and acid chloride monomer. Scanning electron microscopy and atomic force microscopy were used to study surface morphology and roughness properties of NF membranes. Energy dispersive X-ray microanalysis (EDX) was used to analyze the elemental change before and after filtration experiment. Chemical structure and thickness of polyamide formed on TFC membranes were observed by Fourier transmission infrared attenuated total reflectance (FTIR-ATR) spectroscopy. Permeability, salt rejection and pepsin macromolecule rejection of prepared membranes were tested using dead end filtration cell. Antifouling behavior of the membranes was studied by filtering pure water before and after pepsin solution filtration. A smoother and thicker surface without any defect appeared as the concentration of nanoparticle was increased. NaCl rejection was increased from 70% for neat nanofiltration membrane to 84% for 0.5 wt% TiO₂ modified nanofiltration membrane. Antifouling and permeability behavior of the prepared membranes were improved in the new approach. Antibacterial property of prepared membranes was improved as a result of photocatalytic characteristic of TiO₂ nanoparticles.     

A thin film composite membrane supported by a hydrophilic poly(vinyl alcohol‐co‐ethylene) nanofiber membrane: Preparation,characterization, and application in nanofiltration

In this study, a fabricated hydrophilic poly(vinyl alcohol‐co‐ethylene) (PVA‐co‐PE) nanofiber membrane was used as the middle support layer to prepare thin film composite (TFC) membranes for nanofiltration. The effects of the supporting nonwoven layer, grams per square meter (GSM) of nanofiber, reaction time, heat treatment, monomer concentration, operating pressure, and pH value on the separation performance of the TFC membranes were analyzed. These results show that the TFC membranes prepared with the PVA‐co‐PE nanofiber membrane can be used to filtrate different metal ions. For NaCl, Na₂SO₄, CaCl₂, CuCl₂, CuSO₄, and methyl orange solutions, the rejection rates of the TFC membrane with nonwoven polyester as the supporting layer and a nanofiber GSM of 12.8 g/m² are 87.9%, 93.4%, 92.0%, 93.1%, 95.8%, and 100%, respectively. This indicates the potential application of the PVA‐co‐PE nanofiber membrane in the preparation of nanofiltration and reverse‐osmosis TFC membranes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46261.     

Preparation and modification of thin film composite membrane using a bulky dianhydride monomer

One of the most effective methods to modify thin film composite (TFC) membranes is changing the chemistry of top selective layer by different monomers and different monomer concentrations. Herein, we report the preparation of modified TFC membranes using a pyromellitic dianhydride (PMDA) mixed with organic phase (trimesoyl chloride) and meta phenylene diamine (MPD). By manipulating the PMDA amount in organic phase, the structures and chemical compositions of polyamide selective layer could be modified. It was realized that the presence of PMDA could result in a modified membrane with higher surface roughness, less dense selective layer, more surface charge density, and better hydrophilic properties and consequently less fouling. The optimum PMDA concentration was found 0.05 wt%, such that the obtained membrane had 35.6 L m⁻² h⁻¹ pure water flux, about 1.6-fold higher than the reference membrane with similar salt rejection. Fouling intensity for the reference membrane was 38.1%, while for the modified membranes it decreased to 16.7%.     

Highly improved permeation property of thin-film-composite polyamide membrane for water desalination

Thin-film-composite (TFC) polyamide membranes with flux-enhancement were prepared by the interfacial polymerization of m-phenylenediamine with trimesoyl chloride on porous polysulfone support. The addition of 1,3-propanesultone (PS) in the organic phase is used to influence the interfacial polymerization process and the morphology of polyamide layer to improve water flux. FTIR, ¹H NMR and UV spectra were performed to investigate the effect of PS on interfacial polymerization process. In order to study the forming mechanism of TFC membrane, the resulting TFC membranes were characterized by SEM, AFM, ATR-FTIR, XPS, as well as static contact angle. In comparison with conventional polyamide membrane, the TFC membranes fabricated with PS as the additive exhibit much more improved water flux without NaCl rejection decreasing. Notably, the optimal TFC membrane with 0.04% (wt/v) PS as the additive in organic phase shows the best performance with a NaCl rejection of 99.39% and a water flux of 48.57 L m^?2 h^?1 at 1.55 MPa, which has increased 41% compared to the value of the conventional TFC membrane.     

Novel copolymers of trisubstituted ethylenes with styrene — 7. Methyl 2-cyano-3-dihalophenyl-2-propenoates

Summary Methyl 2-cyano-3-dihalophenyl-2-propenoates, R₂C₆H₃CH=C(CN)CO₂CH₃ (R₂= 2,4-difluoro, 2,5-difluoro, 2,6-difluoro, 3,4-difluoro, 3,5-difluoro, and 2-chloro-6-fluoro), were prepared by the piperidine catalyzed Knoevenagel condensation of corresponding disubstituted benzaldehydes and methyl cyanoacetate. Novel copolymers of the propenoates and styrene were prepared at equimolar monomer feed by solution copolymerization in the presence of a radical initiator. The order of relative reactivity (1/r ₁) was 2,5-difluoro (2.11) > 2,6-difluoro (1.84) > 3,5-difluoro (1.71) > 2,4-difluoro (1.4) > 3,4-difluoro (0.65) > 2-chloro-6-fluoro (0.59). The copolymers were characterized by IR, ¹H and ¹³C NMR, GPC, DSC and TGA. High glass transition temperatures of the copolymers compared that of polystyrene indicates a substantial decrease in chain mobility of the copolymers due to the high dipolar character of the trisubstituted ethylene monomer unit. Received: 12 June 2000/Revised version: 12 September 2000/Accepted: 12 September 2000