Preparation and characterization of glutaraldehyde crosslinked chitosan nanofiltration membrane

In this article, we prepare chitosan (CS) membrane on polyacrylonitrile (PAN) ultrafiltration membrane, and utilize the protonated amine group (? NH₃⁺) on the CS to retain γ‐aminobutyric acid (GABA) in a solution with a pH condition below the amino acid isoelectric point, so as to separate the amino acid from a mixture with sodium acetate that simulates the amino acid fermentation broth. To improve the acid resistance of the composite membrane, we chelate the amine groups on the CS by copper sulfate first, then crosslink the hydroxyl groups in glutaraldehyde solution, and remove the copper ion in hydrochloric acid finally to release the amine groups. This crosslinked CS/PAN composite membrane achieves 95% GABA rejection in pH 4.69 solution under the operation pressure of 0.2 MPa, while over 90% of the sodium acetate permeates the membrane. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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     

Optimization of water flux and salt rejection properties of polyamide thin film composite membranes

Optimizing synthesis factors of polyamide top layers is an important requirement in the design of thin film composite (TFC) membranes. In this research, the top layer fabrication method (conventional, heat curing, and spin coating), type of acid acceptor (sodium carbonate, sodium hydroxide, and triethylamine), type of organic phase solvent (hexane, heptane, and mixed hexane/heptane), and concentration of surfactant sodium dodecyl sulfate (0, 0.5, and 1 wt %) are selected as the control parameters of this synthesis and optimized using the Taguchi approach. The analysis of variance shows that the layer fabrication method is the most influential parameter on water flux and salt (NaCl) rejection of TFCs. Furthermore, although the type of organic solvent has not a significant contribution to the water flux, it is another significant factor affecting the rejection. The optimized membrane is then used to construct structure–property relationships and to understand the influence of each individual factor on the desalination performance. Accordingly, a TFC membrane with the top layer fabricated by the heat curing method, in the presence of Na₂CO₃ as the acid acceptor, hexane as the organic phase solvent and 0.5 wt % of the surfactant is prepared that shows water permeance of 2.73 L m⁻² h⁻¹ bar⁻¹ and NaCl rejection of 98.1%. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48858.     

Novel charged chitosan composite nanofiltration membranes containing chiral mesogenic group

To improve the performance of nanofiltration (NF) membranes, a chiral mesogenic compound, a positively charged compound, and a negatively charged compound were grafted to chitosan, respectively. Series of novel composite NF membranes were prepared by over‐coating the polysulfone ultrafiltration membrane with the mixture of chitosan and modified chitosan. The chiral mesogenic compound, the positively charged compound, the negatively compound and their chitosan derivatives were characterized by infrared spectrophotometer, differential scanning calorimetry, polarized optical microscope; the structure of the membrane was characterized by scanning electron microscopy. The performance of composite NF membranes was strictly related to the novel compounds grafted to chitosan and its composition. The rejection reached the maximum of 95.7% for CaCl₂ with P_2‐7 composite NF membrane, corresponding flux was 3155 Lm^?2h^?1. The rejection reached the maximum of 93% for Na₂SO₄ with P_3‐5 composite NF membrane, corresponding flux was 3879 Lm^?2h^?1. Comparing with conventional NF membranes, the membranes were used in low pressure with high flux, especially for the separation of high‐valence ions from solution. The membranes were typical charged NF membranes. POLYM. ENG. SCI., 57:22–30, 2017. © 2016 Society of Plastics Engineers     

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.     

Preparation and characterization of carboxylated multiwalled carbon nanotube/polyamide composite nanofiltration membranes with improved performance

Polyamide thin‐film composite nanofiltration (NF) membranes were prepared via the interfacial polymerization (IP) process of piperazine and 1,3,5‐trimesoyl chloride on the polysulfone/nonwoven fabric ultrafiltration membrane surface. Carboxylated multiwalled carbon nanotubes (cMWNTs) were incorporated into the aqueous phase during the IP process to improve the membrane performance. The composition and morphology of the membrane surface were examined by means of attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy–energy dispersive spectrometry, and atomic force microscopy. The effects of the cMWNTs content on the membrane hydrophilicity, separation performance, and antifouling properties were characterized through water contact angle and crossflow filtration measurements. The experimental results show that membrane surface hydrophilicity, water permeability, salt rejection (R ), and antifouling properties all improved. In particular, when the cMWNTs content was 50 ppm, the magnesium sulfate R of the composite NF membrane reached a maximum value of 98.5%; meanwhile, the membrane obtained an obviously enhanced water flux (62.1 L m^?2 h^?1 at 0.7 MPa), which was two times larger than that of the original NF membrane. The modified NF membranes showed enhanced antifouling properties; this was mainly attributed to changes in the microstructures and surface features of the polyamide layer after the addition of the cMWNTs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45268.     

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.     

Taurine as an additive for improving the fouling resistance of nanofiltration composite membranes

A hydrophilic compound, taurine, was investigated as an additive in the interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC) to prepare thin‐film composite (TFC) membranes. The resulting membranes were characterized by X‐ray photoelectron spectroscopy and attenuated total reflectance–Fourier transform infrared spectroscopy. The morphology and hydrophilicity of the membranes were investigated through scanning electronic microscopy and water contact angle measurements. The separation performance of the TFC membranes was investigated through water flux and salt rejection tests. The protein‐fouling resistance of the films was evaluated by water recovery rate measurements after the treatment of bovine serum albumin. The membrane containing 0.2 wt % taurine showed the best performance of 92% MgSO₄ rejection at a flux of 31 L m^?2 h^?1 and better antifouling properties than the PIP–TMC membranes. An appropriately low concentration of taurine showed the same MgSO₄ rejection as the PIP–TMC membranes but a better fouling resistance performance. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41620.     

荷负电手性壳聚糖纳复合滤膜的制备与性能研究

以聚砜超滤膜作为基膜,以壳聚糖和壳聚糖衍生物的混合物为功能层制备纳滤膜。P2-5复合纳滤（NF）膜对Na2SO4的截留率为93%,相应的通量501.3 L/（m2·h）。电荷效应对NaCl几乎没有影响,而对Na2SO4影响显著。该膜为典型的荷负电膜,适合分离高价阴离子。     

Ionic conductivity and related properties of crosslinked chitosan membranes

Crosslinked chitosan membranes were prepared with a relatively low degree of crosslinking with epichlorohydrin and glutaraldehyde as crosslinking agents under heterogeneous and homogeneous conditions, respectively. The tensile properties, crystallinity, swelling index, and ionic conductivity of the crosslinked membranes were investigated. A significant decrease in the crystallinity and a large change in the swelling ratio of the crosslinked membrane were observed. In comparison with the uncrosslinked chitosan membrane, when the chitosan membrane was crosslinked with an appropriate degree of crosslinking under homogeneous conditions, its ionic conductivity after hydration for 1 h at room temperature increased by about one order of magnitude. In addition, with a lower concentration of the crosslinking agent, the tensile strength and breaking elongation of the crosslinked membrane were almost unchanged. Moreover, up to a critical value, the tensile strength of the membrane increased gradually, and the breaking elongation decreased slowly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 306–317, 2003     

Preparation and characterization of PVA/SA composite nanofiltration membranes

Nanofiltration (NF) composite membranes based on poly(vinyl alcohol) (PVA) and sodium alginate (SA) were prepared by coating PVA/SA (95/5 in wt %) mixture solutions on microporous polysulfone (PSF) supports. For the formation of a defect free thin active layer on a support, the PSF support was multi‐coated with a dilute PVA/SA blend solution. The PVA/SA active layer formed was crosslinked at room temperature by using an acetone solution containing glutaraldehyde as a crosslinking agent. The prepared composite membranes were characterized with a scanning electron microscopy (SEM), a Fourier transform infrared spectroscopy (FTIR), an electrokinetic analyzer (EKA) and permeation tests: The thicknesses of the active layers were about 0.25 μm and 0.01 μm depending on the preparation conditions. The crosslinking reaction of the active layers were completed in less than three minutes via the formation of acetal linkage. The surface of the PVA/SA composite membrane was found to be anionic. The permeation properties of the composite membrane were as follows: 1.3 m³/m² day of flux and > 95% of rejection at 200 psi for 1000 ppm PEG600 solution. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 347–354, 2000     

Interfacially polymerized nanofiltration membranes: Atomic force microscopy and salt rejection studies

Interfacial polymerization is one of the main techniques for producing composite nanofiltration (NF) membranes. In this study, five NF membranes were produced through interfacial polymerization under different conditions of reactions, namely varying reaction time, as well as monomer concentrations. The membranes were then imaged using atomic force microscope (AFM). AFM images provided information of the average pore size, pore size distribution, and surface roughness. For some of the membranes, discrete pore sizes were visible. Increasing the reaction time resulted in decreasing water permeabilities but based on AFM imaging the pore size was of similar value. Increasing the monomer concentration also resulted in decreasing water permeabilities. However, based on AFM imaging the pore size differs considerably. Additional permeation experiments were also carried out using NaCl and Na₂SO₄ solutions with membranes identified as NF. By fitting the rejection data using a model such as the Donnan‐steric‐pore model, the variation in effective charge density of the membranes was also determined. The ability to tailor composite NF membranes with the right properties will significantly improve membrane performance. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 605–612, 2005     

Preparation and characterization of high-performance dehydrating pervaporation alginate membranes

In a previous work, sodium alginate dense membranes demonstrated a good combination of selectivity and permeation flux for dehydrating organic solvents by pervaporation. In this article, the pervaporation performances of alginate composite membranes has been investigated to find out the best condition of membrane formation and the optimum operating conditions. Some ultrafiltration membranes made of poly-(vinylidene fluoride), polyacrylonitrile, and hydrolyzed polyacrylonitrile—either commercially available or prepared in our laboratories—were used as supports for the composite membranes. Sodium alginate dense membranes, modified through ion exchange of sodium with multivalent metal ions (such as Al³⁺, Cr³⁺, Fe³⁺, and Mg²⁺) have also been prepared, and their permselectivities have been tested for the water–ethanol mixture. An interesting stability of the modified membranes in long-term operation is expected. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 959–968, 1998     

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     

Preparation and characterization of asymmetric polyethersulfone nanofiltration membranes: The effects of polyvinylpyrrolidone molecular weights and concentrations

In this study, asymmetric flat‐sheet polyethersulfone (PES) nanofiltration (NF) membranes were prepared via immersion precipitation phase inversion with the addition of polyvinylpyrrolidone (PVP). The effects of PVP with the molecular weights (MW) from 17 to 1400 kDa and the concentration from 0 to 3.0 wt % on the morphologies and performances of PES membranes were systematically studied. The prepared membranes were characterized by SEM, AFM, ATR‐FTIR, contact angle, membrane porosity, the water flux, and the rejection measurement. The results indicated that the porosity and the hydrophilicity of PES NF membrane increased with increasing PVP concentration, and the hydrophilicity of PES NF membrane also improved with increasing PVP MW. The enhancements of the porosity and hydrophilicity resulted in the higher water flux of PES NF membrane. The rejection of Bordeaux S (MW 604.48 Da) for the prepared PES membrane was increased to above 90% with the low PVP concentration, but it turned to decrease remarkably when the PVP concentration reached to a critical value which related to PVP MW. It was concluded that the addition of a small amount of PVP could significantly increase the permeability of PES NF membrane and maintain its rejection of Bordeaux S above 90%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43769.     

Preparation of highly selective nanofiltration composite membranes based on a novel soluble rigidly contorted monomer

Nanofiltration composite membranes with high selectivity are one of the most critical cores in water treatment, and regulating the surface charge and pore structure of active separation layers in thin film composite membranes is one of the most effective means to improve the selectivity of composite membranes. This article synthesized a novel monomer with positive charge and a rigid twisted Tröger's base structure (named TBDA-SO₃), which was manipulated to improve the microporous structure and surface charge of the composite membrane. By interfacial polymerization, TBDA-SO₃, and piperazine were co-reacted with trimesoyl chloride to successfully prepare positively charged, highly selective, and strongly microporous polyamide composite nanofiltration membranes. The best-performing composite nanofiltration membrane in this article has a permeability similar to that of the control group's poly(piperazine amide) (PPA) membrane (pure water flux, 7.8 L m⁻² h⁻¹ bar⁻¹), but has excellent divalent cation selectivity (52.57), which is 4.4 times that of the control group's PPA membrane.     

Synthesis and characterization of crosslinked chitosan immobilized on bentonite and its grafted products with polyaniline

Chitosan immobilized bentonite (CIB) namely chitosan‐coated bentonite (5% chitosan content) was synthesized in 2% acetic acid solution, followed by crosslinking, using epichlorohydrien (ECH). The so‐obtained crosslinked chitosan immobilized on bentonite (CIB‐ECH) and CIB composites were grafted with polyaniline (PANI) through oxidative‐radical copolymerization using ammonium peroxydisulfate in acidic medium to produce PANI‐grafted crosslinked chitosan immobilized on bentonite (PANI‐g‐CIB‐ECH) and PANI‐grafted‐chitosan immobilized on bentonite (PANI‐g‐CIB) composites, respectively. The resultant composites were characterized by using X‐ray diffraction (XRD), thermo gravimetric analysis/differential scanning calorimetry, scanning electron microscopy, Fourier transform infrared (FTIR), and electrical conductivity. XRD and FTIR analyses indicate that chitosan was not intercalated into the silicate layer. Also the electrical conductivity elucidates that the grafted composites fall in the range required for the application as electrostatic dissipation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41078.     

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     

Preparation and characterization of composite membranes of polysulfone and microcrystalline cellulose

Physical and chemical modifications of polymeric ultrafiltration membranes are necessary to improve their hydrophilic properties, strength, and other characteristics. Microcrystalline cellulose (MCC) was prepared from cellulose pulp by acid‐catalyzed hydrolysis in the presence of ultrasonic radiation, and the properties of MCC were evaluated. Through the addition of MCC to a polysulfone (PS) membrane solution, a casting solution of a PS/MCC blend was obtained. Subsequently, the ultrafiltration membrane from the blend was further developed in a phase‐inversion process comprising immersion and deposition. The capacity for ultrafiltration was better with increasing MCC content. When the ratio of MCC to PS was 0.3, the pure water flux of the composite membrane reached 234.2 L/m²/h, and the retention of a bovine serum albumin solution (1 g/L) was as high as 93.4%. The membranes were also observed with scanning electron microscopy and atomic force microscopy to study their microstructures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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.