Preparation and characterization of a composite nanofiltration membrane interfacially polymerized from cis,cis‐1,3,5‐triaminocyclohexane and trimesoyl chloride

cis,cis‐1,3,5‐Triaminocyclohexane (TAC) was synthesized and used to prepare composite nanofiltration (NF) membranes by interfacial polymerization with trimesoyl chloride (TMC). The surface elemental composition, morphology, and hydrophilicity of the prepared NF membranes were characterized. The separation performances were examined with various salts and polyethylene glycol (PEG400, PEG600) solutions. The effects of preparation conditions were also systematically studied. The NF membrane was negatively charged and exhibited a salt rejection in the order Na₂SO₄ (98.2%) > MgSO₄ (90.8%) > MgCl₂ (84.5%) > NaCl (54.6%). The water permeability was 1.56 L m^?2 h^?1 bar^?1, and the molecular weight cutoff was 600 Da. The TAC/TMC membrane exhibited some characteristics that were different from the ones made from common diamines such as m‐phenylenediamine: (1) the surface was smoother, without a ridge‐and‐valley structure; (2) there were two kinds of crosslinking points in the polyamide chains; (3) the active layer was formed faster (only 5 seconds was required to reach a Na₂SO₄ rejection of 98%). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43511.     

Preparation of sulfonated polysulfone/polysulfone and aminated polysulfone/polysulfone blend membranes

Sulfonation and amination of polysulfone (PSf) were performed in this study to improve the hydrophilicity of PSf membranes. The sulfonated polysulfone (SPSf) and aminated polysulfone (APSf) membranes with a higher degree of reaction exhibited a higher water flux and worse mechanical strength than that of the original PSf membranes. Therefore, SPSf/PSf and APSf/PSf blended membranes were prepared in this study to improve their individual properties. By altering the formulations of casting solutions and forming conditions of the membranes (e.g., blending ratios of both polymers, additives, evaporation time, and gelation temperature), different SPSf/PSf and APSf/PSf blending membranes were prepared; and their performance in water flux and salt rejection were measured and are discussed. A difference in salt rejection was also observed between both SPSf/PSf and APSf/PSf blending membranes that rejected the various salts. Experimental results indicated that water flux increased and salt rejection decreased with an increase of the SPSf/PSf blending ratio from 1: 9 to 2: 1. The order of salt rejection, in which the SPSf/PSf blended membranes rejected four varieties of salts, was Na₂SO₄ > MgSO₄ > NaCl > MgCl₂. Furthermore, the opposite order was obtained by the APSf/PSf blended membranes. © 1996 John Wiley & Sons, Inc.     

Development of light‐induced functionalized asymmetric polysulfone membranes

The introduction of functionality into asymmetric polysulfone membranes has widened their applicability. They are modified with acrylic acid with a light‐induced technique. Fourier transform infrared, contact‐angle, porometry, and atomic force microscopy studies have been carried out to characterize the membranes. The performance of the modified membranes has been investigated with permeation measurements. The salt rejection (NaCl and Na₂SO₄) performance of the modified membranes shows evidence of functionalization on them. The modification of the membranes also develops the retention of small organic molecules (glucose and 2,4‐dichlorophenol). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Development of multilayer polyelectrolyte thin‐film membranes fabricated by spin assisted layer‐by‐layer assembly

Polyelectrolyte multilayer (PEM) thin films consisting of alternate layers of two PEM systems, that is poly(diallyl dimethyl ammonium chloride)/poly(vinyl sulfate) (PDAC/PVS) and poly(allyl amine hydrochloride) (PAH)/ are successfully deposited on polysulfone (PSF) support using spin‐assisted layer‐by‐layer assembly. The films are characterized using atomic force microscope, Fourier transform Infrared, and contact angle measurement. The salt (NaCl) rejection and water flux of the [PDAC/PVS] and [PAH/PVS] membranes are also evaluated using a crossflow permeation test cell. The permeation test shows that 120 bilayers of [PAH/PVS] on PSF substrate provide salt rejection of 53% and water flux of 37 L/m² h, whereas that of PDAC/PVS on PSF substrate provide salt rejection of 21% and water flux of 90 L/m² h for a 2000‐ppm NaCl solution feed at a pressure of 40 bar and temperature of 25°C. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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.     

Relation between salt rejection and electrokinetic properties on Shirasu porous glass (SPG) membranes with nano-order uniform pores

The salt rejection by Shirasu porous glass (SPG) membranes having nano-order uniform pores was investigated for understanding the electrokinetic mechanism resulting from the surface charge developed on the membrane when in contact with salt solutions. Due to the dissociation of the hydroxyl groups such as silanol groups on the membrane surface, the membrane was negatively charged over a pH range of 3–10 from electrophoretic measurements. Cross-flow filtration experiments showed that up to 63% of NaCl was rejected by an SPG membrane having a mean pore diameters of 33 nm in a 1 mol m⁻³ NaCl solution at pH 7 under a transmembrane pressure of 74 kPa, even though the pore diameter is much larger than the ion diameter. This is a consequence of the electrostatic repulsive interaction between the co-ions (Cl⁻ ions) and the membrane surface. At the same pH, the rejection factor of NaCl decreased with increasing salt concentration due to an increase in the ionic strength. More negative charge on the membrane surface at higher pH resulted in higher rejection factors of NaCl for a fixed salt concentration. Higher rejection factors of NaCl by SPG membranes with smaller pore sizes for a fixed concentration are due to the higher ratio of the thickness of the electric double layer (Debye length) to the pore radius. The SPG membrane showed a salt rejection sequence: Na₂SO₄, NaCl and CaCl₂ at the same pH. This is because divalent anions (SO₄²⁻) are more strongly repelled by the negatively charged membrane, while divalent cations (Ca²⁺) adsorb specifically onto the membrane surface than monovalent cations (Na⁺). The salt rejection factor increased with increasing permeate volume flux. Due to the stronger acidity of the membrane materials, SPG membranes had a higher rejection factor and a lower isoelectric point (IEP < 3) than ceramic membranes.     

Synthesis and characterization of poly(amide–imide)s and their precursors as materials for membranes

Water soluble diamine amic acids (DAAs) were synthesized by reacting aliphatic diamines with pyromellitic dianhydride. Poly(amide–amic acid)s (PAAs) were prepared by interfacial polycondensation of DAAs in aqueous sodium hydroxide solution with isophthaloyl chloride in dichloromethane. Poly(amide–imide)s (PAIs) containing alternating (amide–amide)–(imide–imide) sequences were obtained by thermal cycloimidization of the PAA films at 175°C for 4 h in a forced air woven. The PAIs were readily soluble in polar aprotic solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, and N‐methyl‐2‐pyrrolidone. The inherent viscosities of the polymers are in the range of 0.97–1.7 dL/g. The polymers were characterized by IR, ¹H nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA). Thin film composite membranes containing PAA ultrathin barrier layer were prepared by in situ interfacial polycondensation of DAA in water with trimesoyl chloride or isophthaloyl chloride in hexane on the surface of a porous polysulfone membrane. The membranes were characterized for water permeability and for the separation of NaCl and Na₂SO₄. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1721–1727, 2000     

Flux,antifouling and separation characteristics enhancement of nanocomposite polyethersulfone mixed-matrix membrane by embedding synthesized hydrophilic adipate ferroxane nanoparticles

Polyethersulfone (PES) nanofiltration (NF) membranes were prepared by blending of synthesized hydrophilic adipate ferroxane nanoparticles (AFNPs) as a novel multifunctional nanofiller via the phase inversion method. The water contact angle measurement indicated the higher hydrophilicity of the NF membranes. The water flux of the membranes improved significantly after the addition of AFNPs, from 10.4 to 32.2 kg/m²h. Antifouling characteristics of AFNPs/PES membranes were improved by increased hydrophilicity and decreased membrane surface roughness. The 0.6 wt% AFNPs/PES membrane exhibited the highest FRR (96%) and the lowest irreversible fouling resistance (6%). The nanofiltration performance of the prepared membranes was evaluated by dye removal and salt retention. The results proved the high dye removal capability of modified membranes (98% rejection) compared with the unfilled PES membrane (89% rejection). The salt retention sequence for membrane with 0.2 wt% of nanoparticles was Na₂SO₄ (70%)>MgSO₄ (60%)>NaCl (18%).     

Nanofiltration and reverse osmosis thin film composite membrane module for the removal of dye and salts from the simulated mixtures

Nanofiltration (NF) and reverse osmosis (RO) thin film composite polyamide membrane modules were used to remove the color from the contaminated solution mixture. The feasibility of membrane processes for treating simulated mixture by varying the feed pressures (100-400 psi) and feed concentrations was studied to assess the separation performance of both NF and RO membranes. It was found that the efficiency of NF and RO membranes used in the treatment of colored water effluents was greatly affected by the presence of salts and dyes in the mixture. Color removal by NF with a high rejection of 99.80% and total dissolved solids (TDS) of 99.99% was achieved from RO by retaining significant flux rate compared to pure water flux, which suggested that membranes were not affected by fouling during the simulated wastewater process operation. The effect of varying concentrations of Na₂SO₄ salt and methyl orange (MO) dye on the performance of spiral wound membranes was determined. Increasing the dye concentration from 500 to 1000 mg/L resulted in a decrease of salt rejection at all operating pressures and for both concentrations of 5000 and 10,000 mg/L as the feed TDS. Increasing the salt concentration from 5000 to 10,000 mg/L resulted in a slight decrease in dye removal.     

Influence of Chloride,Nitrate, and Sulphate on the Removal of Fluoride Ions by Using Nanofiltration Membranes

Abstract

This study investigates the removal of fluoride from various solutions(NaF, NaCl, NaNO₃, and Na₂SO₄) by using three commercial nanofiltration membranes denoted NF70(Filmtec), DESAL5 DL(Osmonics), and MT08(PCI) under 8 bars, 293 K in batch recirculation mode. The membranes were tested for their rejection potential of fluorides in the presence of chlorides, nitrates and sulphates. To identify the mechanisms of selectivity, we successively analyzed the rejections in turn of different combinations of NaF, NaCl, NaNO₃, and Na₂SO₄ in order to simulate the behavior of a real brackish water from Senegal. Fluorides rejection efficiency ranges from 78% to 95%. The efficiency of nanofiltration membranes improved is closely linked to the nature of the solution. The high rejection level(above 98%) of the divalent sulphate ions(50 or 200 mg/L) induces a Donnan effect establishment. In brackish water conditions, for all the membranes, there was a noticeable influence of anion size and hydration energy on fluoride rejection.     

Preparation and characterization of a composite nanofiltration membrane from cyclen and trimesoyl chloride prepared by interfacial polymerization

A novel nanofiltration (NF) membrane was prepared with cyclen and trimesoyl chloride by interfacial polymerization on a poly(ether sulfone) ultrafiltration membrane with a molecular weight cutoff of 50,000 Da. The effects of the reaction time, monomer concentration, and heat‐treatment temperature are discussed. The physicochemical properties and morphology of the prepared NF membrane were characterized by Fourier transform infrared spectroscopy–attenuated total reflectance, scanning electron microscopy, energy‐dispersive spectrometry, and atomic force microscopy. The NF performances were evaluated with solutions of Na₂SO₄, MgSO₄, Mg(NO₃)₂, and NaCl. The salt‐rejection order of the prepared NF membrane was as follows: Na₂SO₄ > MgSO₄ > Mg(NO₃)₂ > NaCl. The resulting rejection of Na₂SO₄ and PEG600 (polyethylene glycol with the average molecular weight of 600) were more than 90%, whereas that of NaCl was approximately 10%. After the addition of silica sol in the aqueous phase (silica sol concentration = 0.1% w/v), the salt rejection of the membrane changed slightly. However, the water flux was from 24.2 L·m^?2·h^?1 (25°C, 0.6 MPa) up to 38.9 L·m^?2·h^?1 (25°C, 0.6 MPa), and the resulting membrane exhibited excellent hydrophilicity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42345.     

Conductance investigation of p‐MIECs fabricated by poly(3,4‐ethylenedioxy thiophene), polyacrylic acid,polyethylene oxide,and lithium‐ion salt

Polymer blends and composite films were facilely prepared from their aqueous solutions with varying contents of poly(3,4‐ethylenedioxythiophene) (PEDOT), polyethylene oxide (PEO), and polyacrylic acid (PAA). The physicochemical and electric properties of the composite films were analyzed by Raman spectra, infrared spectra (FT‐IR), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), and four‐point probe method. PEDOT was successfully incorporated into each blend which was confirmed by spectra analysis. The crystallization of PAA or PEO and the structure of PEDOT should be taken into consideration for the electronic conductivity. According to Raman spectra, in the case of PEDOT–PAA–PEO, conformation of the PEDOT backbone changed from the quinoid to the benzoid structure partly. The ionic conductivities of lithium‐ion salt‐mixed PAA–PEO and ternary blend were characterized by AC impedance spectroscopy. The ternary blend with LiCoO₂ presents good electronic and ionic conductivity, and it appears to be a new candidate for polymeric mixed ionic electronic conductor. POLYM. COMPOS., 36:2076–2083, 2015. © 2014 Society of Plastics Engineer     

Preparation,Characterization, and Separation Performances of Novel Surface Modified LbL Composite Membranes from Polyelectrolyte Blends and MWCNT

Here, it was aimed to modify the surface of NF90 with layer by layer (LbL) blended poly(allylamine hydrochloride) (PAH)-chitosan (CHI) and poly(acrylic acid) (PAA) with/without functionalized multiwalled carbon nanotube (fMWCNT) for reverse-osmosis applications. Using Quartz Crystal Microbalance Dissipation monitoring, it was observed that PAH-CHI/PAA LbL films grew linearly after a few bilayers and no LbL film degradation occurred during synthetic seawater treatment. Thermal degradation of all LbL blended membranes was similar. NF90 had a heterogeneous surface while the surface of LbL blend membranes exhibited some agglomerations due to the polyelectrolyte (PE) complex formation and fibrillary appearance depending on the use of fMWCNT. [(PAH50-CHI50/(PAA-fMWCNT)]₃₀ indicated the highest flux with 14.5 L m² h⁻¹ at 40 bar. The sodium and chlorine ion rejections were 75% and 87%, respectively, for the same membrane. The use of fMWCNT led to a significant enhancement in flux with a slight decay in ion rejections. On the other hand, chlorine ion rejection of [(PAH50-CHI50/(PAA-fMWCNT)]₃₀ decreased by 25% at 40 bar while 60 and 90 bilayers of [(PAH50-CHI50/(PAA-fMWCNT)] disintegrated after NaOCl treatment. Briefly, the flux and ion rejections of the LbL blended membranes can be controlled depending on the use of fMWCNT and different PE couples without multilayer decomposition against synthetic seawater. POLYM. ENG. SCI., 60: 341–351, 2019. © 2019 Society of Plastics Engineers     

Preparation of graphene oxide/polyamide composite nanofiltration membranes for enhancing stability and separation efficiency

Polyamide (PA) NF membranes are synthesized on a hollow fiber support by the interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC). Then, GO is coated on the PA layer to decorate the NF membrane surface (denoted GO/PA-NF). This strategy aims to improve the hydrophilicity, chlorine resistance and separation stability of the membrane. The optimization, chemical composition, morphology, and hydrophilicity of the synthesized GO/PA-NF membrane are characterized. Results indicate that the optimized GO/PA-NF in terms of rejection rate and flux are with 0.05 wt% GO. The rejection of GO/PA-NF for Na2SO₄ and MgSO₄ is 99.4% and 96.9%, respectively. Even if the GO/PA-NF is immersed in 1000 ppm NaClO solution for 48 h, the NF membrane still maintains stable salt rejection. The developed NF membranes exhibit excellent treatment performance on dying wastewater. The permeate flux and rejection of GO/PA-NF toward Congo red solution are determined to be 44.2 L/m²h and 100%, respectively. Compared with the PA membrane, GO/PA-NF presents a higher rejection for Na₂SO₄ (99.4%) and a lower rejection for NaCl (less than 20%), which shows that the NF membranes have a better divalent/monovalent salt separation performance. This study highlights the superior performance of GO/PA-NF and shows its high potential for application in wastewater treatment.     

Characteristics of thin-film nanofiltration membranes at various pH-values

Salt rejection and ion selectivity of NF-255 and NF-45 nanofiltration (NF) membranes were investigated. The rejection of two cations (Na⁺, Ca²⁺) and two anions (Cl⁻, SO_4²⁻) which are common in natural and in industrial wastewater, were studied as a function of pH at permanent pressure and temperature. The ion rejection of NF membranes were investigated in single salt solutions like NaCl, CaCl₂, Na₂SO₄, CaSO₄, and in multicomponent systems that contained all the previous ions. We found that, there is a minimum rejection of the Na⁺ and Cl⁻ ions between pH 4-5 in NF-255 and between pH 7-8 in NF-45. The rejection of calcium ions were increased in each case at lower pH in both membranes. However the pH value where the ion rejection behaviour of membranes changed, were different: pH 4 in NF-255 and pH 8 in NF-45. In NF-45 the chloride ion has negative rejection which depends on the quality of ions and the pH. We found that below pH values of 4 the selectivity of mono- and multivalent cations considerable increased in NF-255. This phenomena may be used for separation of calcium ions from sodium ions from weakly acidic (hydrochloric and sulfuric acid) solution, e.g. regeneration solution of sodium form softening ion exchangers.     

Formation and Characterization of Carboxymethyl Cellulose Sodium (CMC‐Na)/Poly (vinylidene fluoroide) (PVDF) Composite Nanofiltration Membranes

Abstract

A series of carboxymethyl cellulose sodium composite nanofiltration membranes were prepared through the method of coating and cross‐linking. Effects of the preparation techniques and the operating conditions on the rejection performance of the resulting membranes were investigated, respectively. It suggested that the resulting composite NF membrane with excellent rejection performance should be prepared through a certain preparing technology. Attenuated total reflection infrared spectroscopy and atomic force microscopy were employed to characterize the resulting membrane. The rejection of this kind of negatively charged membrane to the electrolyte solutions decreased in the order of Na₂SO₄, NaCl, MgSO₄, and MgCl₂.     

Nanoparticles modified Polyacrylonitrile/Polyacrylonitrile – Polyvinylidenefluoride blends as substrate of high flux anti-fouling nanofiltration membranes

Thin-film composite nanofiltration membranes were prepared by interfacial polymerization reaction of piperazine and trimesoylchloride on virgin and nanoparticles (SiO₂/TiO₂) modified Polyacrylonitrile/70:30 and 30:70 Polyacrylonitrile – Polyvinylidenefluoride blend ultrafiltration substrates. The membranes were characterized for surface hydrophilicity and potential, surface and cross-sectional morphology and equilibrium water content. Pure water permeability and differential rejection of multi (MgSO₄) and monovalent salts (NaCl) of the membranes were studied. Nanofiltration (NF) membranes prepared on nanoparticle modified UF substrates exhibit higher flux than the membranes prepared on virgin UF substrates. NF membranes prepared on TiO₂ modified substrates are exhibiting higher flux than the other membranes. Membrane prepared on TiO₂ modified 70:30 blend substrate exhibits the highest rejection ratio (4.63) of divalent to monovalent salts. Nanofiltration membranes prepared on nanoparticle modified substrates are displaying comparatively higher flux recovery ratio (FRR) and lower total fouling ratio (TFR) values than the NF membranes prepared on virgin ultrafiltration substrates.     

Oxidative chemical polymerization of 3, 4‐ethylenedioxythiophene and its applications in antistatic coatings

The oxidative chemical polymerization of 3, 4‐ethylenedioxythiophene (EDOT) was conducted at room temperature in the presence of poly(styrene sulfonate) (PSS) as the doping agent, sodium supersulphate (Na₂S₂O₈) and ferric sulphate(Fe₂(SO₄)₃) as the compound oxidant and deionized water as the solvent. In order to remove sodium ion (Na⁺), ferric ion (Fe³⁺), and sulfate ion (SO4^2?), certain amount of ion exchanger was added after 24 h, the dark blue poly(3, 4‐ethylenedioxythiophene) (PEDT)/PSS solution was obtained. The influence of different proportions of EDOT and PSS, different proportions of EDOT and the compound oxidant, different stirring rates on the morphology, and surface resistivity were discussed. The influence of pH value of the PEDT/PSS solution, the coating thickness, and soak time on the surface resistivity was investigated. Recipe and experimental conditions were optimized and the PEDT/PSS solution was obtained with excellent performance which has relatively low in surface resistance, good water tolerance, and light transmittance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dynamic polyacrylamide membranes in the reverse osmosis

Dynamic formation of Polyacrylamide membranes on a Millipore filter in the reverse osmosis was optimised concerning rejection of a standard NaCl water solution.Optimised membranes were tested under 70 bars with selected salts in single-solute water solutions.Exclusion of salts with alcali cations depend on the kind of anion and is in the order SO^2-₄ > F^- > HCO^-₃ > Cl^- > NO^-₃ > J^-.Rejection of salts with alkaline earth cations is generally lower than corresponding salts with alcali cations.Especially concentration dependence of rejection of SO^2-₄ and NO^-₃ through these membranes was tested using different cations.Remarkable is the relatively high rejection of Na₂SO₄, which is 93,6% for a 5 g/l water solution under a flux of 820 l/m²· d.Dynamic PAA membranes are not useful for sea water desalination but they could be used for treatment of water with higher SO^2-₄ content.     

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.