Preparation Of Nanofiltration Membranes Research Articles

Preparation of nanofiltration membranes and relating surface chemistry with potential and topography: Application in separation and desalting of amino acids

Thin film composite membranes were prepared on polysulphone substrate by interfacial polymerization reaction of trimesoyl chloride separately with piperazine (Membrane I) or m-phenylene diamine (Membrane IV) or mixture of piperazine and m-phenylene diamine (90:10 and 65:35 w/w for Membrane II and III respectively). Among the four membranes the highest hydrophilicity and molecular weight cut-off values as well as highest negative surface potential were observed for polypiperazine trimesamide membrane (I). The thickness of the dense/rejection layer observed for Membrane IV>III>II>I. SEM study revealed homogeneous surface morphology for Membranes I and IV and heterogeneous morphology for Membranes II and III. The membranes were used for desalting of glutamic acid and glycine and also for the separation of these two amino acids from their mixture. Among the four membranes, Membrane I possessed the highest water flux and rejection ratio of 3.29:1 between MgSO4 and NaCl. For this membrane the rejections of glycine and glutamic acid are respectively 48.5% and 92.6% which are 22.1% and 66.2% higher than the rejection of NaCl. By proper monitoring of the solution pH it is possible to achieve >50% rejection difference between glutamic acid and glycine by this membrane.

Nanofiltration hollow fiber membranes with high charge density prepared by simultaneous electron beam radiation-induced graft polymerization for removal of Cr(VI)

A novel kind of nanofiltration (NF) hollow fiber membranes with high density of negative charges and relative high permeate flux was prepared by grafting of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) onto a polysulfone (PSf) ultrafiltration hollow fiber membrane using the simultaneous electron beam radiation-induced method. ATR-FTIR and FESEM analyses revealed that the monomer was grafted on both the outer and inner surfaces of the membrane. The effects of irradiation dose and monomer concentration on the mean pore size and performance of the membranes were investigated. The prepared NF membranes were used for removal of Cr(VI) from aqueous solution under varying conditions such as pH value, initial Cr(VI) concentration and coexisting ions. The experimental results showed that Cr(VI) could be effectively removed by the resulting NF membranes when the pH of the solution was higher than 8 and the performance of Cr(VI) removal was nearly not affected by the presence of Na2SO4 and NaCl in the experimental range. It was indicated that the high negative charge density resulting from the high degree of grafting made the grafted membranes achieve nanofiltration performance at a relative large pore size.

Preparation of PVA Nanofiltration Membrane with Good Solvent Resistance

Polyvinylalcohol (PVA) with good solvent resistance was used in preparation of nanofiltration membrane. The preparation parameter such as PVA concentration, cross-linking agent concentration and reaction time are studied in detail. When the composite membrane was prepared under optimized conditions and tested at 0.4 MPa and 20 °C, the flux of the NF membrane was about 15 L/m2h and the Na2SO4 rejection of it was about 53.3%.

Studies on the Preparation of Nanofiltration Membrane for Ultra-low Pressure Application through Hydrophilization of Porous PVDF Membrane Using Inorganic Salts

Studies on the Preparation of Nanofiltration Membrane for Ultra-low Pressure Application through Hydrophilization of Porous PVDF Membrane Using Inorganic Salts

Preparation of an efficient nanofiltration membrane based on blending of polysulfone and polysulfone-g-butylacrylate prepared by ATRP

Polysulfone is one of the most common used polymers for preparation of nanofiltration membranes. These membranes are highly susceptible to fouling problems because of their surface hydrophobic nature. In this paper a new approach for modification of polysulfone to overcome the fouling problems was introduced. The modification was carried out via blending of polysulfone with a modified grafted polysulfone using atom transfer radical polymerization (ATRP) method. The modified grafted polysulfone was synthesized via ATRP grafting of n-butylacrylate from chloromethylated polysulfone. The graft copolymers were characterized by FT-IR, NMR, DSG and TGA techniques. Furthermore, surface morphology and performance of the corresponding membrane were studied in detail using SEM and pure water flux and salt rejection experiments, respectively. The results indicated that the prepared modified polysulfone membranes have high surface hydrophilicity and therefore better fouling resistance and very good water permeability.

One-step self-assembly fabrication of amphiphilic hyperbranched polymer composite membrane from aqueous emulsion for dye desalination

Organic solvent usually was used in a polymer-based membrane fabricating process. In this study, otherwise pure water was utilized to prepare the polymer composite membrane. A pure aqueous emulsion was firstly prepared through directly dissolving a commercially available amphiphilic hyperbranched polymer (HBP), Boltorn W3000 into water. As the cross-linking agent, glutaraldehyde, glycol, triethylamine, or tetraethyl orthosilicate was then added into the emulsion, respectively. Finally, the HBP was self-assembled onto the surface of polyacrylonitrile (PAN) ultrafiltration membrane by immersing the PAN substrate into the emulsion to form the composite membrane. The homogeneous dispersion of the HBP in the emulsion was confirmed by transmission electron microscopy, and the formation of the composite membrane was characterized by IR spectra, field emission scanning election microscopy and atomic force microscopy. Importantly, the composite membrane performed an excellent separation performance in dye retention and desalination. For example, with the operation pressure of 0.5MPa, the retention of methyl blue could reach 97.0% with a flux of 55.0Lm−2h−1, while the salt retention was lower than 12.0%. This work thus not only illustrated a new approach for the preparation of nanofiltration membrane in aqueous solution, but also produced a potentially useful polymer-based composite membrane for highly efficient dye desalination.

Preparation and characterization of positively charged polysulfone nanofiltration membranes

Abstract Charged nanofiltration (NF) membranes were prepared from aminated polysulfone (APSF) via a phase inversion technique, by varying the polymer and solvent weight ratios. A two-step phase inversion technique, adopted for the preparation of NF membranes, involved chloromethylation, and subsequent amination of the polymer, polysulfone (PSF). Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopic analyses of the prepared chloromethylated PSF (CPSF) membrane confirmed the incorporation of chloromethylated groups on the polymer backbone. Also, the separation capability of the prepared membranes was evaluated by compaction studies, pure water fluxes (PWF) at different pressures, and hydraulic membrane resistance measurements. Furthermore, scanning electron microscopic (SEM) and atomic force microscopic (AFM) images revealed that the pore size and pore distribution decreased with increase in the polymer weight ratio. In addition, the functionality of the prepared membranes as a nano-filter was analyzed by constructing a stirred batch NF cell and evaluated towards a feed solution containing different concentrations of Cr (III) ions. The performance of the prepared membrane was compared with commercially available (NFT-50) NF membrane.

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.

Preparation and Characterization of Nanofiltration Membranes Synthesized by Hyperbranched Polyester and Terephthaloyl Chloride (TPC)

Thin-film composite (TFC) nanofiltration (NF) membranes were developed by terephthaloyl chloride (TPC) crosslinked the hydroxyl ended groups of hyperbranched polyester (HPE) on polyacrylonitrile (PAN) support. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) indicated that a thin layer of crosslinked HPE molecules were deposited on PAN porous membrane surface successfully. The preparation conditions were also optimized. The separation performance of PAN-HPE-TPC NF membranes are mainly related with the concentration of monomer in the aqueous phase rather than that in the organic phase. Water permeability and salts rejections of the membranes were measured. The flux and rejection of these NF membranes for Na2SO4 (1 g/L) reached 11.43 L/m2h and 96.5% under 0.6 MPa, respectively. At the same time, the nanofiltration properties were compared with other membranes prepared with hyperbranched polymers. All NF membranes prepared with hyperbranched polymers showed relative high permeate flux.

REMOVED: Preparation of Nanofiltration Membranes using Sol–gel Transition of Organic Molecular Networks in their Phase–separating Mixtures with Linear Polymers

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Preparation and characterization of polysulfone and modified poly isobutylene-alt-maleic anhydride blend NF membrane

Recently nanofiltration (NF) is gaining more importance for water treatment. It is replacing the conventional method of water treatment due to advantages of NF membranes over RO system. In this work, we are discussing the preparation of NF membrane for desalination of sea water. We herein report the synthesis of polymer, by the reaction of p-amino benzoic acid (PABA) and poly isobutylene-alt-maleic anhydride (PIAM) and its blend membrane preparation with polysulfone (PSf). The new membranes were characterized by SEM images, surface wettability to investigate the hydrophilic nature of the membrane, water swelling, pure water flux, molecular weight cut-off and salt rejection of the membranes. The membranes showed nano size (<50nm) pores in SEM image, and the contact angle data revealed that membrane surface is moderately hydrophilic. Membrane with 70:30 (PSf:modified PIAM) composition has shown good salt rejection of 96% at 200kPa for 3500ppm of NaCl solution with a pure water flux of 38.36Lm−2h−1.

Preparation and Characterization of a Novel Organic-Inorganic Nanofiltration Membranes Prepared by Interfacial Polymerization

A novel organic-inorganic nanocomposite NF membrane containing SiO2 were prepared by interfacial polymerization on polysulfone (PSF) ultrafiltration membrane with poly(amidoamine) (PAMAM) dendrimer and trimesoyl chloride (TMC) as monomers. The membranes were investigated by Thermal Gravimetric Analysis (TGA), Field Emission Scanning Electron Microcopy(FESEM) and Energy Dispersive X-ray Detector(EDX), then the separation performance of salt solution was investigated. The results indicated that the nanoparticles were well-distributed in the membranes. The addition of SiO2 in the skin layer increased thermal stability and improved roughness and hydrophility of membrane. The pure flux for PA-SiO2 increased than neat PA membrane while the rejection rate of Na2SO4 salt solution was lower than the latter.

Preparation of polysulfone nanofiltration membranes by UV-assisted grafting polymerization for water softening

The rising demand for high quality water heightens the need to soften hard and very hard water. In this study, flat sheet polysulfone ultrafiltration membranes were prepared by phase inversion and modified by UV-induced polymerization of acrylic acid in order to prepare nanofiltration membranes for water desalination. Polyethylene glycol of different molecular weights mainly in the range of 1500–4000 Da were used in the casting solution and acrylic acid was polymerized on the membrane surface. In this way, a manipulated membrane was prepared with higher pore size and higher surface charge density for improved water softening. The results show that by increasing irradiation time and monomer concentration in the photografting process, pure water flux declines and salt rejection increases. For a membrane photografted for 180 min with acrylic acid solution (6 wt.%) and PEG-4000 as additive, the rejection of Na 2SO 4, MgSO 4, NaCl and CaCl 2 follows a decreasing in order of 100%, 77.9%, 49.9% and 35.9% respectively. The RMS roughness of the prepared membrane is 1.65 nm, which is well in the nanofiltration roughness range. Featuring a large pore size and high surface charge density, the developed nanofiltration membranes show a promising capability for water desalination.

Preparation and characterization of a novel nanofiltration membrane

In this study, poly[2-(N, N-dimethyl amino)ethyl methacrylate] (PDMAEMA) was prepared by bulk polymerization using AIBN as an initiator. Aqueous PDMAEMA solution was then purified by hollow fiber ultrafiltration membrane technology to remove oligomers. PDMAEMA/polysulfone (PSF) positively charged nanofiltration (NF) membrane was developed by interfacial polymerization by using PSF ultrafiltration membrane as the substrate, PDMAEMA aqueous solution as the coating solution and p-xylylene dichloride dissolved in n-heptane as the organic crosslinker. Effects of substrate material, concentration of monomer, pH value of PDMAEMA, coating time and crosslinking time were then carefully examined on the separation properties of the prepared NF membrane. Data suggested that the rejection rate of the composite NF membrane to 1 g/l of MgSO4 was around 86.7 %, and the water flux was about 18.4 L·m−2·h−1. Therefore, the developed NF membrane is suitable for rejection and desalination of alkaline dyes.

Preparation of N, O-carboxymethyl chitosan/cellulose acetate blend nanofiltration membrane and testing its performance in treating industrial wastewater

An N, O carboxymethyl chitosan (NOCC)/cellulose acetate (CA) blend nanofiltration (NF) membrane was prepared in acetone solvent. From our previous work on miscibility experiments, it was proposed to take 0.4 wt% of NOCC in NOCC/CA blend membrane preparation. The newly prepared blend membrane was characterized with the help of scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and mechanical properties of membrane. Molecular weight cut-off (MWCO) of newly prepared blend membrane was found to be 710 Da, which was in the range of nanofiltration. The performance of the prepared NF membrane had been tested to separate chromium and copper from a common effluent treatment plant (CETP) wastewater at different operating conditions. The highest rejection for chromium and copper were observed to be 83.40 and 72.60%, respectively, at 1 MPa applied pressure and 16 L/min (LPM) feed flow rate.

Polyelectrolyte membranes prepared by dynamic self-assembly of poly (4-styrenesulfonic acid- co-maleic acid) sodium salt (PSSMA) for nanofiltration (I)

In recent years, the layer-by-layer (LBL) self-assembly of polyelectrolyte has attracted much attention for the preparation of nanofiltration (NF) membranes. However, most researchers focused on the homopolymers, few studied on the copolymers for the preparation of NF membranes. In the present work, a series of nanofiltration membranes were prepared by dynamic self-assembly of a copolymer polyelectrolyte containing both weakly and strongly ionized groups, poly (4-styrenesulfonic acid- co-maleic acid) sodium salt (PSSMA), with poly (allylamine hydrochloride) (PAH) and poly (styrenesulfonic acid sodium salt) (PSS) on the modified polyacrylonitrile (PAN) ultra-filtration membranes. The effects of substrate, deposition pH, SS/MA ratio in PSSMA, concentration of the PSSMA and bilayer number on the properties of the NF membranes were investigated. The results indicated that the performances of the NF membranes prepared by dynamic self-assembly process were superior to those prepared by the static self-assembly process. The membranes terminated with PSSMA were negatively charged. Due to the changes of charge density and conformation of PSSMA in different pH conditions, the [PAH/PSS] 1PAH/PSSMA membrane prepared at pH 2.5 showed higher Na 2SO 4 rejection and larger flux than those of the membrane prepared at pH 5.7. The NF membrane [PAH/PSS] 1PAH/PSSMA composed of only two bilayers exhibited 91.4% Na 2SO 4 rejection and allowed solution flux of 28.6 L/m 2 h at 0.2 MPa. The solution flux increased to 106.6 L/m 2 h at 0.8 MPa, meanwhile, no obvious decrease in Na 2SO 4 rejection was observed.

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.

Nanofiltration membrane preparation by photomodification of cardo polyetherketone ultrafiltration membrane

Hydrophilic nanofiltration membranes were prepared by UV-assisted graft polymerization of hydrophilic monomers onto the surface of ultrafiltration membranes made of cardo polyetherketone (PEK-C). The effect of irradiation time and monomer nature on the membrane performances was investigated. Analyses by Fourier transform infrared in attenuated total reflection mode, contact angles of the modified-membrane surface showed that the grafting degree and the hydrophilicity increase with the irradiation/grafting time or irradiation intensity. It was found that the UV-assisted grafting can be performed on the PEK-C chains with or without benzophenone (BP). The grafting inside the pores of the UV sensitive PEK-C membrane is demonstrated by the change of the membrane retention characteristic from that of an UF membrane to that of a nanofiltration membrane. The retentions to sodium chloride and sodium sulfate of the membrane with poly(acrylic acid) grafted for 90 min. UV irradiation under a 1.6 mW/cm 2 irradiation were 36 % and 94.1%, respectively, while the water flux through the membrane was ca. 31.3 L m −2 h −1, at 0.4 MPa.

Nanofiltration membrane prepared from polyacrylonitrile ultrafiltration membrane by low-temperature plasma: 4. grafting of N-vinylpyrrolidone in aqueous solution

In order to control surface pore sizes of polyacrylonitrile (PAN) ultrafiltration membranes and their distribution, the present work concerns the graft-modification of membranes by Ar low-temperature plasma. Some typical plasma irradiation conditions such as plasma power of 30–40 W, irradiation time of 60 s and pressure of 15–20 Pa were experimentally selected by our previous experiments. N-vinylpyrrolidone (NVP) monomers mixed in water were grafted onto the PAN membrane surface in this investigation. The effectiveness of grafting was systemically studied under different graft reaction conditions, such as concentration of monomer, reaction time and reaction temperature. The chemical changes at the modified surface were characterized by reflection FTIR, X-ray photoelectron spectroscopy (XPS). The permeation of the prepared nanofiltration membranes were studied using pure water. Water flux significantly declines with increase in both graft reaction time and temperature of grafting medium. In the low concentration range studied, NVP monomer concentration did not have strong effect on flux. At 2 MPa and 30°C filtration conditions, the grafted membrane has a retention of 83.5% salts for a mixed salt aqueous solution (0.03 MMgSO 4 + 0.02 MNaCl).

From ultrafiltration to nanofiltration hollow fiber membranes: a continuous UV-photografting process

A new way to prepare nanofiltration membranes, consisting of in-line external modification of the skin of a polysulfone ultrafiltration hollow fibre skin, is described. The paper presents a continuous process (dip-coating followed by photografting) and the influence of the operating conditions on the membrane characteristics. This study is focused on a simplified model based on the evaluation of the two sources of monomer available for grafting: one is monomer contained in the thin film drawn from the dip bath, second is contained in the pores of the membrane. The results show that two extreme types of modification can be produced, depending on the experimental conditions: a high rate coupled with a short dip contact time leads essentially to an external grafting whereas a low rate coupled with a long dip residence time leads essentially to an “in pore” grafting.