Cross-linked PAN-based thin-film composite membranes for non-aqueous nanofiltration

A new approach on the development of cross-linked PAN based thin film composite (TFC) membranes for non-aqueous application is presented in this work. Polypropylene backed neat PAN membranes fabricated by phase inversion process were cross-linked with hydrazine to get excellent solvent stability toward dimethylformamide (DMF). By interfacial polymerization a selective polyamide active layer was coated over the cross-linked PAN using N,N′-diamino piperazine (DAP) and trimesoyl chloride (TMC) as monomers. Permeation and molecular weight cut off (MWCO) experiments using various dyes were done to evaluate the performance of the membranes. Membranes developed by such method show excellent solvent stability toward DMF with a permeance of 1.7 L/m² h bar and a molecular weight cut-off of less than 600 Da.     

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。     

Polyamide composite membranes for enhanced organic solvent nanofiltration performance by metal ions assisted interfacial polymerization method

Herein, thin-film composite membranes consisting of poly(m-phenyleneisophthalamide) substrate and polyamide active layer were constructed by transition metal ion-assisted interfacial polymerization method. As compared to the traditional polyamide membranes, a much thinner polyamide layer (33 vs. 200 nm) can be synthesized with higher permeance (3.2 vs. 0.62 L m⁻² h⁻¹ bar⁻¹) in the organic solvent nanofiltration. Similarly, the prepared membranes maintained a high rejection (>99%) for various dyes. Optimal membranes prepared by using Co²⁺ exhibited strong tolerance to various organic solvents with good long-term stability. Positron annihilation spectroscopy and other characterization methods were used to investigate the relationships between the membrane microstructures and the enhanced separation performance. Based on molecular dynamics simulation, it was found that the diffusion coefficient of polyethyleneimine monomer decreased by about 18 times after adding Co²⁺ to the aqueous solution (forming coordination interaction). This procedure has great potential and sustainability for practical organic solvent nanofiltration applications.     

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.     

Thin-film composite crosslinked polythiosemicarbazide membranes for organic solvent nanofiltration (OSN)

In this work we report a new class of solvent stable thin-film composite (TFC) membrane fabricated on crosslinked polythiosemicarbazide (PTSC) as substrate that exhibits superior stability compared with other solvent stable polymeric membranes reported up to now. Integrally skinned asymmetric PTSC membranes were prepared by the phase inversion process and crosslinked with an aromatic bifunctional crosslinker to improve the solvent stability. TFC membranes were obtained via interfacial polymerization using trimesoyl chloride (TMC) and diaminopiperazine (DAP) monomers. The membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and contact angle measurement.The membranes exhibited high fluxes toward solvents like tetrahydrofuran (THF), dimethylformamide (DMF) and dimethylsulfoxide (DMSO) ranging around 20 L/m² h at 5 bar with a molecular weight cut off (MWCO) of around 1000 g/mol. The PTSC-based thin-film composite membranes are very stable toward polar aprotic solvents and they have potential applications in the petrochemical and pharmaceutical industry.     

耐氧化芳香聚酰胺纳滤膜的研究进展

芳香聚酰胺纳滤膜不耐氧化,易被活性氯氧化降解,导致膜性能急剧下降,缩短膜的使用寿命,目前已成为制约芳香聚酰胺纳滤膜应用和发展的关键问题之一。本文综述了芳香聚酰胺纳滤膜的材料和结构,重点概述了芳香聚酰胺氯化和膜性能下降的机制,并进一步介绍了近年来耐氧化芳香聚酰胺纳滤膜的研究进展。     

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.     

Preparation and characterization of nanofiltration composite membranes using polyacrylonitrile (PAN). II. Preparation and characterization of polyamide composite membranes

Polyamide (PA) composite membranes in which PA active layers were interconnected with support layers via the formation of ionic bonds were prepared by the interfacial polymerization of piperazine (PIP) with trimesoyl chloride (TMC) on the surfaces of microporous polyacrylonitrile (PAN) supports containing carboxylic acid groups. Formation of the ionic bonds through an acid‐base reaction between ? NH group of PIP and ? COOH of the support was studied using FTIR‐ATR spectroscopy. Variation of the surface morphologies of the composite membranes that was induced by the presence of the ionic bonds was observed with a FESEM and an AFM. Permeation tests with various feed solutions such as PEG 600, Na₂SO₄, MgSO₄, MgCl₂, and NaCl solutions were carried out to see how the characteristics of the PAN supports affected on the flux and rejection of the corresponding PA composite membranes. Chemical stabilities of the composite membranes with the ionic bonds were studied and compared with that of a conventional PA composite membrane, using alcohol solutions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2729–2736, 2001     

Evaluation of a modified spray-applied interfacial polymerization method for preparation of nanofiltration membranes

Nanofiltration (NF) membranes were fabricated by using piperazine (PIP) and trimesoyl chloride (TMC) by conventional and spray-applied interfacial polymerization methods, studying the effect of the application method for both phases, the number of applied layers, and the displacement speed for the spray application. A polysulfone ultrafiltration membrane was used as support. NF membranes were characterized by different spectroscopic, microscopic, and physicochemical techniques. Rejection capacity was evaluated for sodium chloride (NaCl), sodium sulfate (Na₂SO₄), and magnesium sulfate (MgSO₄) salts; the decreasing rejection order was Na₂SO₄ > MgSO₄ > NaCl for each NF membrane. NF membrane prepared with one layer of the sprayed out TMC solution and conventional application of PIP solution exhibited the highest salt rejection (99% for 1000 ppm Na₂SO₄) and a permeated flux of 10.28 L m⁻² h⁻¹ at 0.55 MPa. The modified method is a facile-reproducible preparation methodology that reduces the consumption of time, effort, and reagents leading to a scalable manufacturing process for separation technology. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48129.     

Preparation,characterization, and application of thin film composite nanofiltration membranes

The active aromatic polyamide layers of thin film composite nanofiltration (NF‐TFC) membranes were prepared via interfacial polymerization (IP) from three different types of polyamine: p‐phenylenediamine (PPD), m‐phenylenediamine (MPD), or piperazine (PRP), and trimesoyl chloride (TMC) on polysulfone/sulfonated polysulfone (PSf/SPSf) alloy substrates. Chemical components, cross section structures, and thermal properties of the polyamide active layers and the bulk membranes, characterized by Fourier transfer IR spectroscopy and attenuated total reflection IR spectroscopy, scanning electron microscopy, and differential scanning calorimetry and thermogravimetry, respectively, revealed an interpenetrating layer between the polyamide active layer and the substrate. A ridge–valley structural active layer was formed on the PSf/SPSf substrate for the NF‐TFC membrane with a thick polyacrylamide (PA) layer. Compared with the NF‐TFC membranes on PSf substrates, those on PSf/SPSf alloy substrates had a higher permeability without losing the selectivity by introducing the hydrophilic SPSf into the hydrophobic PSf substrates. The binding between the modified substrate and the active PA layer was also improved. Good separation performances using these NF‐TFC membranes were obtained in the polyvalent ion separation, the ground water softening, and the treatment of wastewater from adipic acid plants in a wide pH range. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1251–1261, 2005     

Characteristics of the nanofiltration composite membranes based on PVA and sodium alginate

Chemically stable nanofiltration (NF) composite membranes based on poly(vinyl alcohol) (PVA) and sodium alginate (SA) (hereafter, these membranes are called PVA/SA composite membranes) were prepared by coating microporous polysulfone (PSF) supports with dilute PVA/SA blend solutions. The PSF supports were pretreated with small monomeric compounds to reduce their pore size and to improve their hydrophilicity before coating with the PVA/SA blend solutions. The concentration of the PVA/SA blend solutions ranged from 0.1 to 0.3 wt %. The membranes prepared in this study were characterized with various methods such as SEM, FTIR, permeation tests, and z‐potential measurements. Especially, chemical stabilities of the membranes were tested, using three aqueous solutions with different pHs such as a HCl solution (pH 1), a K₂CO₃ solution (pH 12.5), and a NaOH solution (pH 13). Their chemical stabilities were compared with that of a polyamide (PA) composite membrane prepared from piperazine (PIP) and trimesoyl chloride (TMC). In this study, it was found that the PVA/SA composite membranes prepared showed not only good chemical stabilities but also good permeation performances in the range from pH 1 to 13. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2471–2479, 2001     

Enhancement of flux and solvent stability of Matrimid® thin‐film composite membranes for organic solvent nanofiltration

The development of high flux and solvent‐stable thin‐film composite (TFC) organic solvent nanofiltration (OSN) membranes was reported. A novel cross‐linked polyimide substrate, consisting of a thin skin layer with minimum solvent transport resistance and a sponge‐like sublayer structure that could withstand membrane compaction under high‐pressure was first fabricated. Then the solvent flux was significantly enhanced without compromising the solute rejection by the coupling effects of (1) the addition of triethylamine/camphorsulfonic acid into the monomer solution, and (2) the combined post‐treatments of glycerol/sodium dodecyl sulphate immersion and dimethyl sulfoxide (DMSO) filtration. Finally, the long‐term stability of the TFC membrane in aprotic solvents such as DMSO was improved by post‐crosslink thermal annealing. The novel TFC OSN membrane developed was found to have superior rejection to tetracycline (MW: 444 g/mol) but was very permeable to alcohols such as methanol (5.12 lm^?2h^?1bar^?1) and aprotic solvents such as dimethylformamide (3.92 lm^?2h^?1bar^?1) and DMSO (3.34 lm^?2h^?1bar^?1). © 2014 American Institute of Chemical Engineers AIChE J, 60: 3623–3633, 2014     

PA/ZIF-8/PVDF复合纳滤膜的制备及其性能

采用反向扩散法在聚偏氟乙烯(PVDF)基膜表面原位生长一层均匀、致密的金属有机骨架材料ZIF-8纳米晶体层,并进一步优化界面聚合反应,制备高性能聚酰胺(PA)/ZIF-8/PVDF复合纳滤膜.采用SEM、XRD、FTIR、AFM、XPS、水接触角测定仪以及固体表面Zeta电位仪对ZIF-8/PVDF复合膜及PA/ZIF-8/PVDF复合纳滤膜的组成、结构和形貌进行了表征,考察了ZIF-8亚层的生长对界面聚合反应、复合纳滤膜结构及性能的影响.结果表明,ZIF-8晶体亚层在PVDF膜表面的均匀连续生长改善了PA分离层与PVDF基膜的界面相容性,提高复合纳滤膜PA分离层的交联度.在0.6 MPa下,复合纳滤膜纯水通量可达24.05 L/(m2·h),对MgSO4、Na2SO4、NaCl和MgCl24种盐的截留率分别达到97.34％、93.57％、89.31％和85.16％,具有优异的抗污染性能.     

界面聚合聚酰胺纳滤膜渗透选择性能优化的研究进展

纳滤因其分离效率高、操作压力低、环境友好等优点,在废水处理、海水淡化和工业分离纯化等众多领域有着重要的应用。界面聚合法制备的聚酰胺（PA）纳滤膜是最为常用的纳滤膜种类之一。然而界面聚合反应速度快,如何通过调控界面聚合过程,优化纳滤膜选择分离层的结构从而提高渗透选择性,以满足不同领域对纳滤膜需求仍是亟需解决的问题。本文从影响界面聚合单体扩散因素的角度出发,综述了近年来PA纳滤膜渗透选择性能优化的研究进展,包括新型PA纳滤膜、纳米材料/PA混合基质膜及超薄PA纳滤膜3个方面,探讨了选择分离层结构调控与纳滤膜渗透选择性能优化的关系,最后指出目前界面聚合制备高渗透选择性PA纳滤膜在规模化、稳定性及可控性存在的问题,并对未来界面聚合纳滤膜在微观结构和聚合过程调控方面的研究进行了展望。     

界面聚合法PI/PP耐溶剂复合纳滤膜的制备与表征

以丙烯酰胺接枝的聚丙烯(PP)超滤膜为支撑层,间苯二胺(MPD)、均苯四甲酰氯(BTAC)分别为水相及有机相功能单体,通过界面聚合及其后续的酰亚胺化制备了聚酰亚胺(PI)/PP耐溶剂复合纳滤膜。讨论了水相浓度、有机相浓度及酰亚胺化溶液配方等条件对复合膜结构及其分离性能的影响。分别采用傅里叶红外光谱仪(FTIR)、扫描电子显微镜(SEM)表征分离层的化学组成及复合膜的形态结构,得到膜的分离、透过及其耐溶剂性能。结果表明,有机相浓度的影响最为显著,支撑膜表面形成了均匀致密的PI分离层,复合膜呈负电性,并具备优秀的耐溶剂性能。实验范围内,MPD、BTAC的浓度分别为8、2 g·L-1,酰亚胺化溶液乙酸酐∶三乙胺∶苯体积比为1∶1∶10时,所制备膜的分离性能较佳,对Na2SO4、酸性艳蓝6B的截留率分别达93.8%和96.9%。     

Solvent and pH resistance of surface crosslinked chitosan/poly(acrylonitrile) composite nanofiltration membranes

The resistance of novel surface crosslinked Chitosan/poly(acrylonitrile) (PAN) composite nanofiltration (NF) membranes to pH and organic solvents was studied with respect to the effects of crosslinking parameters, namely, glutaraldehyde concentration and crosslinking time. The pH resistance was determined by permeation of aqueous acidic (pH 2.5) and basic (pH 11) solutions as well as swelling studies in the pH range of 2.5–11. The solvent resistance was determined by swelling, immersion, and permeation studies with several industrially important organic solvents, namely methanol, ethanol, iso‐propanol, methyl ethyl ketone, ethyl acetate and hexane. It was observed that the crosslinked composite membranes maintain the permeate fluxes for test solvents for 2 h of continuous operation without any significant change in flux. SEM studies on membrane samples after immersion as well as permeation with the above‐mentioned solvents indicated that the membrane morphology was maintained. The results are explained in terms of solvent–membrane polar and hydrophobic interactions, using solubility parameters of membrane and solvents and dielectric constants of solvents. Pure water flux and polyethylene glycol transmission data indicated that at pH 2.5 and 11, the membrane stability increased with increasing glutaraldehyde concentration and was much better at pH 11 than at pH 2.5. All surface crosslinked membranes showed reduced swelling between pH 4–10. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1782–1793, 2000     

Reinforced thin-film composite nanofiltration membranes: Fabrication,characterization, and performance testing

Hollow-fiber (HF) membranes have the advantage of a higher packing density compared to flat-sheet and spiral-wound configurations. However, the low pressure tolerance of HF membranes limits their applications in nanofiltration (NF). In this study, reinforced thin-film composite (r-TFC) HF NF membranes were fabricated and evaluated in tests with water containing different salts and organic matter. Reinforced polysulfone ultrafiltration membranes were used as a support for a polyamide layer prepared from piperazine and trimesoyl chloride monomers. The interfacial polymerization conditions were optimized via selection of the trimesoyl chloride reaction time that gave the highest membrane performance. A specific permeate flux of 5.1 L m^–2 h^–1 bar^–1, an MgSO₄ rejection of 69%, and an NaCl rejection of 26% at a transmembrane pressure of 6 bars were obtained with the optimized r-TFC membranes. Performance studies with water characterized by synthetic solution demonstrated removals of the total organic carbon, ultraviolet absorbance at 254 nm, and turbidity in excess of 65, 80, and 90%, respectively. The results of this study illustrate the feasibility of manufacturing r-TFC HFs and using them in water-treatment applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48001.     

Effect of adding a smart potassium ion-responsive copolymer into polysulfone support membrane on the performance of thin-film composite nanofiltration membrane

Thin-film composite (TFC) nanofiltration (NF) membranes were fabricated via the interfacial polymerization of piperazine (PIP) and 1,3,5-benzenetricart)oiiyl trichloride on polysulfone (PSf) support membranes blended with K^+-responsive poly(N-isopropylacryamideco- acryloylamidobenzo-15-crown-5)(P(NIPAM-co- AAB15C5)). Membranes were characterized by attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscope, scanning electron microscope, contact angle, and filtration tests. The results showed that:(1) Under K^+-free conditions, the blended P(NIPAM-co-AAB15C5)/PSf supports had porous and hydrophilic surfaces, thereby producing NF membranes with smooth surfaces and low MgSO4 rejections;(2) With K^+ in the PIP solution, the surface roughness and water permeability of the resultant NF membrane were increased due to the K^+-induced transition of low-content P(NIPAM-co-AAB15C5) from hydrophilic to hydrophobic;(3) After a curing treatment at 95℃, the improved NF membrane achieved an even higher pure water permeability of 10.97 L·m^-2·h^-1 - bar1 under 200 psi. Overall, this study provides a novel method to improve the performance of NF membranes and helps understand the influence of supports on TFC membranes.     

Thin-film composite nanofiltration membranes prepared by electropolymerization

A novel approach to preparation of composite asymmetric nanofiltration membranes is reported based on a thin selective layer deposited by electropolymerization (EP) on top of an asymmetrically porous and electronically conductive porous support. Support films with ultrafiltration characteristics were cast from a concentrated dispersion of carbon black particles, a few tens of nanometers large, in a solution of polysulfone followed by precipitation in a non-solvent bath (phase inversion). Composite membranes with poly(phenylene oxide) and polyaniline thin top layers were prepared by EP deposition from solutions of phenol and aniline, respectively, of which polyaniline film demonstrated a dense uniform structure and water flux and rejection to sucrose and magnesium sulfate in the nanofiltration range.