Tannic acid/Fe^(3+)interlayer for preparation of high-permeability polyetherimide organic solvent nanofiltration membranes for organic solvent separation

Organic solvent nanofiltration(OSN)membranes have a great application prospect in organic solvent separation,but the development of OSN membranes is mainly restricted by trade-off between permeability and rejection rate.In this work,a TA/Fe^(3+)polymer was introduced into polyetherimide(PEI)ultrafiltration membranes crosslinked with hexamethylene diamine as the intermediate layer,and OSN membranes with high separation performance and solvent permeability were obtained through interfacial polymerization and solvent activation.The interlayer with high surface hydrophilicity and a fixed pore structure controlled the adsorption/diffusion of the amine monomer during interfacial polymerization,forming a smooth(average surface roughness<5.5 nm),ultra-thin(separation layer thickness reduced from 150 to 16 nm)and dense surface structure polyamide(PA)layer.The PA-Fe^(3+)_3-HDA/PEI membrane retained more than 94%of methyl blue(BS)in 0.1 g·L^(-1)BS ethanol solution at 0.6 MPa,and the ethanol permeation reached 28.56 L^(-1)·m^(-2)·h^(-1).The average flux recovery ratio(FRR)of PA-Fe^(3+)_(3)-HDA/PEI membrane was found to be 84%,which has better fouling resistance than PA-HDA/PEI membrane,and it was found to have better stability performance through different solvent immersion experiments and continuous operation in 0.1 g·L^(-1)BS ethanol solution.Compared with thin-film composite nanofiltration membranes,the PA-Fe^(3+)_(3)-HDA/PEI membrane can be manufactured from an economical and environment-friendly method and overcomes the trade-off between permeability and rejection rate,showing great application potential in organic solvent separation systems.

Preparation of N, O-carboxymethyl Chitosan Composite Nanofiltration Membrane and Its Rejection Performance for the Fermentation Effluent from a Wine Factory

N, O-carboxymethyl chitosan （NOCC） composite nanofiltration （NF） membranes were prepared by coating and cross-linking. The fermentation effluent from a wine factory was treated with the resulting NOCC/polysulfone （PSF） composite NF membranes. The permeate flux and the removal efficiencies of the resulting NF membranes for the color, chemical oxygen demand （CODcr）, total organic carbon （TOC）, and conductivity of the fermentation effluent were investigated in relation to the driving pressure, the feed flow, and the operation time. The permeate flux and the removal efficiencies were found to increase with the increase of the driving pressure or the feed flow. At 0.40 MPa and ambient temperature the removal efficiencies were 95.5%, 70.7%, 72.6%, and 31.6% for color, CODcr, TOC, and conductivity, respectively. The membrane was found to be stable over a 10-h ooeration for the fermentation effluent treatment.

Preparation of pH-sensitive Composite Nanofiltration Membrane

Positively charged composite nanofiltration （NF） membranes were prepared through interfacial polymerization of poly[2-（N,N-dimethyl amino）ethyl methacrylate]（PDMAEMA） on porous polysulfone （PSF） substrate membranes. The effects of pH on swelling ratio （SR） of the pure crosslinked PDMAEMA membrane and on separation performances of the composite NF membrane were investigated. The results show that the quaternized amino groups produced through interfacial polymerization technique are soluble in both phases, which accelerate the crosslinking reaction as self-catalysts. The swelling/contracting behavior of the pure crosslinked PDMAEMA exhibited a well reversible pH sensitive property. Importantly, the rejection and flux of the composite NF membrane show pH-sensitive behavior in NF process. Furthermore, with the help of a relatively novel method to measure membrane conduction, the true zeta potentials calculated on the basis of the streaming potential measurements proved the pH-sensitive behavior of the NF membrane.

Treatment of Textile Dye Effluent Using a Self-made Positively Charged Nanofiltration Membrane

A selfmade positively charged nanofiltration （NF） membrane was used to treat textile dye effluent to generate water for reuse, and the factors affecting nanofiltration process such as operating pressure, feed flow and membrane cleaning were investigated. With an applied pressure of 1.0 MPa and a feed flow of 40 L/h, this NF membrane has a removal of 93.3% for CODor and a reduction of approximately 51.0% in TDS, salinity and conductivity achieving the chroma removal of 100%. The permeate obtained through this membrane is suitable for recycling. Moreover, the membrane could be reused after being cleaned with 1% NaOH solution.

Novel nanofiltration membranes with tunable permselectivity by polymer mediated phase separation in polyamide selective layer

Microstructure in selective layer has played a decisive role in permselectivity of nanofiltration(NF) membranes,and nanomaterials were well-known additives that had been applied to mediate the microstructure and permeability of polyamide NF membranes. However, nanoadditives generally displayed a poor dispersion in membranes or in fabrication process. To solve this problem, we showed an interesting concept that novel NF membranes with hybrid selective layer consisting of flexible polyisobutylene(PIB) and rigid polyamide could be fabricated from well-defined interfacial polymerization. The hydrophobic polymer mediated phase separation and microdomains formation in polyamide layer were found. The immiscibility between the rigid polyamide and flexible PIB as well as the resultant interface effect was interpreted as the reason for the polymer enhanced permselectivity, which was similar with the well-known thin film nanocomposite(TFN) membranes that nanoparticles incorporated contributed significantly to membrane permeability and rejection performance.Our results have demonstrated that novel NF membranes with enhanced performance can be prepared from immiscible polymers, which is a new area that has not been extensively studied before.

Fabrication of anti-fouling polyamide nanofiltration membrane by incorporating streptomycin as a novel co-monomer

Polyamide(PA)thin-film composite(TFC)na nofiltration(NF)membrane has extremely broad application prospects in separation of monovalent/diva lent inorganic salts mixed solutio n.However,membrane fouling is the main obstacle to the application of PA,TFC and NF membrane.Streptomycin(SM)is a hydrophilic antibiotic containing a large number of hydroxyl and amino groups.In this work,the NF membrane was prepared via interfacial polymerization(IP)between trimesoyl chloride(TMC)in the organic phase and SM/piperazine(PIP)mixture in the aqueous phase.The NF membrane structure and performance were characterized in detail.The results showed that SM successfully participated in the IP.The negative charge and hydrophilicity of membrane surface were improved.The prepared membrane exhibited good anti-adhesion and anti-bacterial performance,Additionally,when the SM concentration was 2%,the prepared membrane exhibited the optimal permselectivity.The water permeance was 89.4L·m^(-2)·h^(-1)·MPa^(-1).The rejection of NaCl and Na_(2)SO_(4) were 17,17%and 97.84%,respectively.The NaCl/Na_(3)SO_(4) separation factor of the SM2-PIP/TMC membrane in 1000 mg·L^(-1) NaCl and 1000 mg·L^(-1)Na_(2)SO_(4) mixed solution was 40,which was 3.3 times that of PIP/TMC membrane.It indicated that SM2-PIP/TMC demonstrated excellent monovalent/divalent salts separation performance.This work provided an easy and effective approach to preparing anti-fouling NF membrane while possessing superior monovalent/divalent salts separation performance.

A NOVEL NANOFILTRATION MEMBRANE PREPARED WITH PAMAM AND TMC (Ⅰ)

A series of nanofiltration (NF) membranes were prepared with poly(amido-amine) (PAMAM) and trimesoyl chloride (TMC) via in situ interfacial polymerization.The effects of the generation number and concentration of PAMAM on the properties of NF membranes were discussed.Fourier transform infrared spectroscopy (FTIR-ATR),atomic force micrgscopy (AFM),scanning electron microscopy (SEM) and contact angle measurements were employed to characterize the resulting membranes.The nanofiltration performances were evalua...

Biofimls Formation in Nanofiltration Membranes

Technological advances in the past 30 years have boosted the use of PSM （membrane separation processes）, important for its efficiency and flexibility of operation. These processes can be used in many types of separation, with some advantages over the usual separation processes. NF （nanofiltration） is a membrane separation technique, which has properties intermediate between reverse osmosis and ultrafiltration in terms of separated species, because the average of the pores is in the range of 1/2 to 10 nm, and the separation occurs in function of load and size of the species. Usually removes species in solution with an effective diameter of about 1 nm or larger and multivalent ions to a greater extent than monovalent ions. The objective was to study the formation of biofouling on the surface of commercial nanofiltration membrane （Osmonics/GE） and surface membrane synthesized in our laboratory. The study was conducted in permeation system with filtration cell with tangential displacement of 15 bar for 8 days flow. DBNPA （2,2-dibromo-3-nitrilopropionamide） was used as a biocide agent, and an anti-fouling, in concentrations of 5 and 300 ppm, respectively, added to the water coming from the Beach Sea Galleon, RJ. The results demonstrated that there was no change in the flow and rejection of sulphate ions, even in the presence of anti-fouling. The count of aerobic, anaerobic and BRS （sulfate reducing bacteria） in seawater before and after using the DBNPA showed efficiency in controlling these groups of microorganisms and biofouling microbial consortium consisting of the existing in seawater.

Preparation and Characterization of Tri-channel Hollow Fiber Nanofiltration Membrane

Improvement strength is beneficial to the popularization of hollow fiber nanofiltration(NF) membrane.The tri-channel hollow fiber NF membrane was prepared by interfacial polymerization(IP).The high strength tri-channel hollow fiber ultrafiltration(UF) membrane were used as the support membrane,m-phenylenedianline(m-PDA),and polyethylenimine(PEI) were used as aqueous phase monomer,and trimesoyl chloride(TMC) was used as organic phase monomer.Fourier transform infrared spectroscopy(FTIR),scanning electron microscope(SEM),and gas sorption analyzer(GSA) were applied in structural analysis of NF membrane.Polymer FTIR illustrates the IP occurrence between aqueous phase monomer and organic phase monomer.The SEM images of NF membrane show the formation of a thin dense layer on surface of support membrane after IP.The flux(J) of optimal NF membrane is 11.2 L·m-2· h-1 at the 0.35 MPa operating pressure.Its retention(R) for NaCl,Na2SO4,MgCl2,Xylenol orange,and Neutral red is 17.4%,30.2%,16.1%,94.3%,and 51.0%,respectively.The NF membrane is on negative charge and its pore radius distributes between 0.3-2.0 nm.

Prussian Blue/Cellulose Acetate Thin Film Composite Nanofiltration Membrane for Molecular Sieving and Catalytic Fouling Resistance

Nanofiltration(NF)membranes as high selective separators are appealing for molecular sieving,which still remains a great challenge for the mixed dyes with same charge.In this study,cellulose acetate(CA)membranes were firstly aminated by ethylene imine polymer(PEI),and then the thin film of metal organic frameworks(MOFs)were constructed onto aminated CA membrane through forward-diffusion,slow crystallization and in situ growth of Fe Co-Prussian blue(FeCo-PB)crystallization layers.The designed PB@CA composite NF membrane shows an ideal rejection for Congo red(CR)/methyl orange(MO)mixture solution,with 99.7%±0.2%for CR and 33.5%±2%for MO.In addition,the composite NF membrane demonstrated good efficiency for photocatalytic degradation of organic fouling(permeability recovery ratio was up to 92%)due to the active FeCo-PB micro-cubes.Thus,this work provides a practical strategy to prepare MOFs mediated thin film composite nanofiltration membrane for precise molecular sieving and catalytic antifouling performances.

Tailoring the microstructure and properties of PES/SPSf loose nanofiltration membranes using SPES as a hydrophilic polymer for the effective removal of dyes via steric hindrance and charge effect

Herein,polyethersulfone(PES)and sulfonated polysulfone(SPSf)blend membranes were prepared with addition of sulfonated polyethersulfone(SPES)as a hydrophilic polymer and adipic acid as a porogen via non-solvent induced phase separation method for effective fractionation of dyes based on the influence of steric hindrance and charge effect.Raman spectroscopy and molecular dynamic simulation modeling confirmed that hydrogen bonds between PES,SPSf,SPES,and adipic acid were crucial to membrane formation and spatial arrangement.Further addition of hydrophilic SPES resulted in a membrane with reduced pore size and molecular weight cut-off as well as amplified negative charge and pure water permeance.During separation,the blend membranes exhibited higher rejection rates for nine types of small molecular weight(269.3–800 Da)dyes than for neutral polyethylene glycol molecules(200–1000 Da).This was attributed to the size effect and the synergistic effect between steric hindrance and charge repulsion.Notably,the synergistic impact decreased with dye molecular weight,while greater membrane negative charge enhanced small molecular dye rejection.Ideal operational stability and anti-fouling performance were best observed in M2(PES/SPSf/SPES,3.1 wt%).Summarily,this study demonstrates that SPES with–SO3‒functional groups can be applied to control the microstructure and separation of membranes.

HYDROPHILIC NANOFILTRATION MEMBRANES WITH SELF-POLYMERIZED AND STRONGLY-ADHERED POLYDOPAMINE AS SEPARATING LAYER

Inspired by the self-polymerization and strong adhesion characteristics of dopamine in aqueous conditions, a novel hydrophilic nanofiltration （NF） membrane was fabricated by simply dipping polysulfone （PSf） ultrafiltration （UF） substrate in dopamine solution. The changes in surface chemical composition and morphology of membranes were determined by Fourier transform infrared spectroscopy （FTIR-ATR）, X-ray photoelectron spectroscopy （XPS）, scanning electron microscopy （SEM） and atomic force microscopy （AFM）. The experimental results indicated that the self-polymerized dopamine formed an ultrathin and defect-free barrier layer on the PSf UF membrane. The surface hydrophilicity of membranes was evaluated through water contact angle measurements. It was found that membrane hydrophilicity was significantly improved after coating a polydopamine （pDA） layer, especially after double coating. The dyes filtration experiments showed that the double-coated membranes were able to reject completely the dyes of brilliant blue, congo red and methyl orange with a pure water flux of 83.7 L/（mE.h） under 0.6 MPa. The zeta potential determination revealed the positively-charged characteristics of PSf/pDA composite membrane in NF process. The salt rejection of the membranes was characterized by 0.01 mmol/L of salts filtration experiment. It was demonstrated that the salts rejections followed the sequence： NaC1 〈 NaaSO4 〈 MgSO4 〈 MgC12 〈 CaCl2, and the rejection to CaC12 reached 68.7%. Moreover, the composite NF membranes showed a good stability in water-phase filtration process.

High-performance polyamide nanofiltration membrane with arch-bridge structure on a highly hydrated cellulose nanofiber support

Nanofiltration(NF)membranes with outstanding performance are highly demanded for more efficient desalination and wastewater treatment.However,improving water permeance while maintaining high solute rejection by using the current membrane fabrication techniques remains a challenge.Herein,polyamide(PA)NF membrane with archbridge structure is successfully prepared via interfacial polymerization(IP)on a composite support membrane of saltreinforced hydrophilic bacterial cellulose nanofibers(BCNs)nanofilm/polytetrafluoroethylene(BCNs/PTFE).The strong hydration of BCNs promotes Marangoni convection along water/organic solvent interface during the IP process,which creates extra area for interfacial reaction and produces a thin PA active layer with arch-bridge structures.These arch-bridge structures endow the resulting PA active layer with substantial larger active area for water permeation.Consequently,the PA NF membrane exhibits exceptional desalination performance with a permeance up to 42.5 L m^-2h^-1bar^-1 and a rejection of Na2SO4as high as 99.1%,yielding an overall desalination performance better than almost all of the state-of-the-art NF membranes reported so far in terms of perm-selectivity.

Influence of incorporating beta zeolite nanoparticles on water permeability and ion selectivity of polyamide nanofiltration membranes

A novel polyamide(PA) thin film nanocomposite(TFN) membrane modified with Beta( β) zeolite was prepared by interfacial polymerization on a poly(ether sulfone)(PES) ultrafiltration membrane. Compared with the PA thin film composite(TFC) membrane, the introduction of β zeolite with porous structure notably increased the water flux of TFN membrane. Because the β zeolite with tiny-sized and well-defined inner-porous acted as prior flow channels for water molecules and a barrier for the sulfate ions. The successful introduction of β zeolite into the(PA) selective layer and their dispersion in the corresponding layer were verified by scanning electron microscope(SEM) and atomic force microscopy(AFM). Water contact angle, zeta potential measurements were used to characterize the changes of membrane surface properties before and after incorporating the β zeolite. With the β zeolite introducing, the water contact angle of modified TFN membrane was decreased to 47.8°, which was benefited to improve the water flux. Meanwhile, the negative charges of the modified TFN membrane was increased, resulting in an enhancement of separation effect on SO4^2- and Cl^-. In term of nanofiltration(NF) experiments, the highest pure water flux of the TFN membranes reached up to 81.22 L m^(-2) hr^-1 under operating pressure of 0.2 MPa, which was 2.5 times as much as the pristine TFC membrane.

Modeling of the separation performance of nanofiltration membranes and its role in the applications of nanofiltration technology in product separation processes

Although there is a voluminous literature on the determination of structural parameters(the pore radius,the ratio of membrane porosity to membrane thickness)of a nanofiltration(NF)membrane and its separation perfor-mance(such as the rejection and the permeation flux)by the simplified Teorell-Meyer-Sievers(TMS)model,little of this research comments on other theories and the consequences of linking modeling evaluation to technological application.Theories used to predict the separation performance of an NF membrane usually include:the non-equilibrium thermo-dynamic model,the pore model,the space charge model,the TMS model,the electrostatic and steric-hindrance model,and the semiempirical model.In the article,we briefly trace the origins or the general ideas of the above-mentioned theories.From there,recent researches on the characterization of mem-brane structural parameters and electrical properties(such as the surface charge density qw)are reviewed.We then turn to research on the separation performance of an NF membrane for single-component solutions of inorganic electrolytes,neutral organic solutions,and a mixture solution of electro-lytes or that of an electrolyte and neutral organic solute.Afterwards,we outline the applications of NF technology in the processes of product separation and conclude with a discussion on the role of models in such applications.

Polyamide Nanofiltration Membrane from Surfactant-assembly Regulated Interfacial Polymerization of 2-Methylpiperazine for Divalent Cations Removal

Removal of metal ions from water can not only alleviate the scaling problem of domestic and industrial water,but also solve the water safety problem caused by heavy metal ion pollution.Here,we fabricate a positively charged nanofiltration membrane via surfactant-assembly regulated interfacial polymerization(SARIP)of 2-methylpiperazine(MPIP)and trimesoyl chloride(TMC).Due to the existence of methyl substituent,MPIP has lower reactive activity than piperazine(PIP)but stronger affinity to hexane,resulting in a nanofiltration(NF)membrane with an opposite surface charge and a loose polyamide active layer.Interestingly,with the help of sodium dodecyl sulfate(SDS)assembly at the water/hexane,the reactivity between MPIP and TMC was obviously increased and caused in turn the formation of a positively charged polyamide active layer with a smaller pore size,as well as with a narrower pore size distribution.The resulting membrane shows a highly efficient removal of divalent cations from water,of which the rejections of MgCl_(2),CoCl_(2)and NiCl_(2)are higher than 98.8%,98.0%and 98.0%,respectively,which are better than those of most of other positively charged NF membranes reported in literatures.

Supramolecular fabrication of hyperbranched polyethyleneimine toward nanofiltration membrane for efficient wastewater purification

Nanofiltration technology has opened an efficient pathway to addressing the grand issue of wastewater purification.Polyethyleneimine(PEI),as a hydrophilic polymer,is a promising material to manufacture separation membranes owing to its superiority.Here,we prepared a hyperbranched PEI-based separation mem-brane through the supramolecular hydrogen bond interaction for wastewater purification.The amino groups in the PEI molecule were partially oxidized to the nitro groups with sodium hypochlorite(NaClO).Moreover,the PEI molecu-lar chains can be regulated from the hyperbranched state to the internal nucle-ation state.Molecular dynamics simulation results further indicated the strong hydrogen bonds among the oxidized PEI(O-PEI)molecular chains and the decreased gyration radius of the O-PEI molecule due to the formation of the nitro groups.In addition,the wettability and zeta potential of O-PEI membranes can be controlled by adjusting the molecular weight and oxidation degree of the PEI molecules.Under the collective effect of size screening and charge repulsion,the O-PEI separation membrane displayed a wide range of purification capabilities for contaminations,such as dye molecules and salts.This work may offer a new strategy to fabricate hyperbranched O-PEI membranes for wastewater purifica-tion.

Removal of sulfamethoxazole by nanofiltration membrane

The retention of sulfamethoxazole (SMZ) by nanofiltration (NF) membranes is strongly influenced by the pH value of the solution. The retention of SMZ reaches its peak value when the solution pH rises above its pKa2 value as the compound transforms into a negatively charged species. Charge repulsion is the main mechanism involved in SMZ removal by NF membranes. In this study, the removal of SMZ by NF membranes, as a function of solution chemistry, was examined at pH 8.9 to investigate the effect of solution conditions on charge repulsion. The results show that the retention of negatively charged SMZ is relatively independent of SMZ concentration, and an increase in the ionic strength of the solution causes a relatively small reduction in retention. A small effect of humic acid (HA) on SMZ retention was noticed at pH 8.9, which can be explained by a small but insignificant improvement in the zeta potential of the membrane caused by HA at high pH values. However, it was found that SMZ concentration in the feed decreased significantly in solutions containing tannic acid (TA). The Adams-Bohart model was applied to our experimental data and was found to be suitable for describing the initial part of the breakthrough curves. The adsorptive parameters of the membrane were determined.

Surface modification of polypiperazine-amide membrane by self-assembled method for dye wastewater treatment

Polypiperazine-amide membranes were modified with poly(ethyleneimine)(PEI) by self-assembled method,through which PEI molecules were fixed on the membrane surface by ionic interaction. In the experiments,the PEI concentration ranged from 50 to 2000 mg·L-1while the depositing time was fixed at 20 min. The results showed that low PEI concentration resulted in a slight increase of pure water flux, which was attributed to the enhanced membrane surface hydrophilicity. The PEI adsorption on membrane surface had less effect on the rejections to neutral PEG and sucrose, but improved the rejections to divalent cationic ions and methylene blue as the result of reversion of the membrane surface charge from negative to positive according to the XPS analysis and zeta potential measurements. The membrane modified at PEI = 1500 mg·L-1exhibited high rejection to methylene blue(MB) and is potential to be applied in the treatment of effluents containing positively charged dyes.

Synthesis of polypiperazine-amide thin-film membrane on PPESK hollow fiber UF membrane

A new interfacial polymerization （IP） procedure is developed in order to synthesize polypiperazine-amide thin-film membrane on the inner surface of poly（phthalazinone ether sulfone ketone） （PPESK） hollow fiber ultrafiltration （UF） membrane. A hollow fiber composite membrane with good performance was prepared and studied by PT-IR and scanning electron microscopy.