Na2SO4 Rejection Research Articles

Highly permeable composite nanofiltration membrane via γ-cyclodextrin modulation for multiple applications

The treatment of pharmaceutical wastewater has become a worldwide problem. Highly efficient treatment for wastewater is extremely critical for ecological environment. Herein, a thin-film nanofibrous composite (TFNC) nanofiltration (NF) membrane modulated by γ-cyclodextrin (γ-CD) was prepared via interfacial polymerization. The γ-CD and piperazine (PIP) were adopted and acting as the mixed reaction monomers in aqueous phase for the fabrication of the separation layer. Not only PIP, γ-CD units would also react with organic phase trimesoyl chloride (TMC) at the interface and participate into the polymerization network. Compared with pure polyamide TFNC membranes, the γ-CD modulated TFNC membranes demonstrated thinner skin thickness. Owing to the 3D hollow structure of γ-CD, the self-contained through cavities would provide additional direct nanochannels to facilitate the water transport. Under 0.5 MPa, the optimized PIP0.5γCD0.5 and PIP0.5γCD1.5 TFNC membranes showed much higher permeate flux of 23.27 and 26.34 L m-2h−1 bar−1, respectively, than that of pure polyamide membranes (9.13 and 9.85 L m-2h−1 bar−1) and the Na2SO4 rejection remained high (>98.7%). Moreover, both TFNC membranes exhibited extremely high rejection (>99%) for several pharmaceuticals (doxycycline hydrochloride, tetracycline, and amoxicillin), and the PIP0.5γCD0.5 TFNC membrane exhibited a good separation factor (31.8) for NaCl/tetracycline solution. In addition, both optimized TFNC membranes showed good pressure resistance and long-term operating stability. This research revealed a facile modulation strategy for the fabrication of high-performance NF membrane and indicated the great promise for desalination, pharmaceuticals wastewater treatment and antibiotics concentration.

In Situ Chemical Modification with Zwitterionic Copolymers of Nanofiltration Membranes: Cure for the Trade-Off between Filtration and Antifouling Performance.

Breaking the trade-off between filtration performance and antifouling property is critical to enabling a thin-film nanocomposite (TFC) nanofiltration (NF) membrane for a wide range of feed streams. We proposed a novel design route for TFC NF membranes by grafting well-defined zwitterionic copolymers of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) and 2-aminoethyl methacrylate hydrochloride (AEMA) on the polyamide surfaces via an in situ surface chemical modification process. The successful grafting of a zwitterionic copolymer imparted the modified NF membranes with better surface hydrophilicity, a larger actual surface area (i.e., nodular structures), and a thinner polyamide layer. As a result, the water permeability of the modified membrane (i.e., TFC-10) was triple that of the pristine TFC membrane while maintaining high Na2SO4 rejection. We further demonstrated that the TFC-10 membrane possessed exceptional antifouling properties in both static adsorption tests and three cycles of dynamic protein and humic acid fouling tests. To recap, this work provides valuable insights and strategies for the fabrication of TFC NF membranes with simultaneously enhanced filtration performance and antifouling property.

Recycling of aged RO membranes as NF/UF membranes: Biosafety evaluation and aging process

With dramatic growth of reverse osmosis (RO) in water treatment, more than 1.5 million waste RO membrane modules will be generated worldwide annually, which will lead to waste of resources and environmental pollution if not properly disposed. The present study aims at evaluating the feasibility of using aged RO membranes in NF/UF process. And ultraviolet (UV) irradiation was used to simulate the aging process. In addition to the conventional separation performance, virus (bacteriophage MS2) removal rate was used to evaluate the ability that membranes ensure the biosafety of the permeate. After 48 h continuous UV irradiation (313 nm, 1 W/m2), the membrane maintained high Na2SO4 rejection (88%) and phage MS2 removal rate (>4 log), which was comparable to NF-like membrane. After 96 h, the membrane manifested sound virus removal rate (>3.4 log) and high pure water permeability (122.6 L·m−2·h−1·bar−1), but the ability for salt rejection was rather weak, which approximated to a UF-like membrane. It was noteworthy that the aged membrane maintained a high virus removal rate within 0–96 h, which ensured the biosafety of the permeate. The results provided a basis for direct recycling of aged membranes.

High‐Precision and High‐Flux Separation by Rationally Designing the Nanochannels and Surface Nanostructure of Polyamide Nanofiltration Membranes

High‐precision separation with increased water permeability is critical for efficient membrane‐based water treatment processes. To achieve high selectivity toward different targeted species while allowing rapid water transportation, the structure of the membrane polyamide selective layer requires delicate regulation. Herein, an effective approach to systematically expand the pore size of polyamide layers by incorporating ammonium ion‐modified carbon dots (CDs) into the polyamide network is developed. The ammonium ions with different alkyl chain lengths attached to the CDs create nanochannels of different sizes in the network to lower the energy barrier for water transportation while maintaining high selectivity to targeted species. When the alkyl chain length of the ammonium ions reaches eight carbon atoms (i.e., C8 ions), the amphiphilic C8‐CDs induce the formation of the ridged nanostructure on the membrane surface and hence the increased membrane filtration area. The resultant thin‐film nanocomposite (TFN) membrane, denoted as the TFN‐C8‐CDs membrane, demonstrates a higher Na2SO4 rejection of 98.9% and NaCl/Na2SO4 selectivity of 83.1 than the pristine polyamide membrane, together with a tripled pure water permeability of 29.0 L m−2 h−1 bar−1. Herein, a viable approach for ingeniously designing the nanochannels and surface nanostructure of polyamide membranes for more efficient filtration processes is provided.

Thin-Film Composite Nanofiltration Membrane Modified by Fulvic Acid to Enhance Permeability and Antifouling Performance

A novel thin-film composite (TFC) nanofiltration (NF) membrane was manufactured by interfacial polymerization (IP) with addition of the additive fulvic acid (FA) into the piperazine (PIP) aqueous solution onto a poly(m-phenylene isophthalamide) (PMIA) substrate. The aqueous phase additive FA can effectively modify the PA layer structure by slowing down the diffusion of the PIP monomer and reacting with trimesoyl chloride (TMC) to generate ester groups. The pure water permeability (PWP) of the optimized NF membrane enhanced from 10.4 to 22.3 L m–2 h–1 bar–1, and the Na2SO4 rejection remained above 97.8%. The outstanding performance benefited from superior hydrophilicity, enlarged pores, and a relatively thin separation layer. Furthermore, the obtained NF membrane presented ascendant thermal stability, long-term stability, and fouling resistance. Therefore, this work offers novel insight into regulation of the PA layer structure and promotion of NF membrane performance.

Modulating interfacial polymerization with phytate as aqueous-phase additive for highly-permselective nanofiltration membranes

Modulating interfacial polymerization (IP) process has been recognized as an effective way to optimize the physicochemical structure of polyamide membranes and thus elevating nanofiltration performance. Herein, phytic acid dodecasodium salt (PADS), a small molecule salt with high solubility, is used as an aqueous-phase additive to modulate the piperazine (PIP) monomers diffusion behavior via electrostatic interaction during the IP process. The PADS with a high charge density can form long-range electrostatic interaction with the PIP molecules to retard their diffusion. The diffusion coefficient of PIP can be effectively modulated within an order of magnitude (∼10−5-10−6 cm2 s−1) by varying the amount of PADS. Accordingly, the growth of polyamide layer is inhibited and the membrane thickness is reduced from 95 nm to 50 nm. The optimized membrane presents a two-fold increase in water permeance while maintaining excellent salt rejection performance (Na2SO4 rejection >97%), outperforming the benchmark commercial nanofiltration membranes.

Enhancing the Permselectivity of Thin-Film Composite Membranes Interlayered with MoS2 Nanosheets via Precise Thickness Control.

The demand for highly permeable and selective thin-film composite (TFC) nanofiltration membranes, which are essential for seawater and brackish water softening and resource recovery, is growing rapidly. However, improving and tuning membrane permeability and selectivity simultaneously remain highly challenging owing to the lack of thickness control in polyamide films. In this study, we fabricated a high-performance interlayered TFC membrane through classical interfacial polymerization on a MoS2-coated polyethersulfone substrate. Due to the enhanced confinement effect on the interface degassing and the improved adsorption of the amine monomer by the MoS2 interlayer, the MoS2-interlayered TFC membrane exhibited enhanced roughness and crosslinking. Compared to the control TFC membrane, MoS2-interlayered TFC membranes have a thinner polyamide layer, with thickness ranging from 60 to 85 nm, which can be tuned by altering the MoS2 interlayer thickness. A multilayer permeation model was developed to delineate and analyze the transport resistance and permeability of the MoS2 interlayer and polyamide film through the regression of experimental data. The optimized MoS2-interlayered TFC membrane (0.3-inter) had a 96.8% Na2SO4 rejection combined with an excellent permeability of 15.9 L m-2 h-1 bar-1 (LMH/bar), approximately 2.4 times that of the control membrane (6.6 LMH/bar). This research provides a feasible strategy for the rational design of tunable, high-performance NF membranes for environmental applications.

Poly(vinylidene fluoride) Substrate-Supported Polyamide Membrane for High-Temperature Water Nanofiltration

Conventional polysulfone and polyethersulfone membrane-supported polyamide (PA) nanofiltration (NF) membranes suffer an obvious performance decline due to the drastic pore shrinkage of their membranes during high-temperature (HT) desalination processes. Herein, a thermally stable PA NF membrane (PVDF-IP-2) was successfully constructed over a relatively hydrophobic polyvinylidene fluoride (PVDF) membrane using a continuous interfacial polymerization (CIP) method. The PVDF-IP-2 membrane had a moderate water permeance of 8.3 L m–2 h–1 bar–1 and a 99.7% Na2SO4 rejection at room temperature, which were comparable to those of commercial NF membranes. Introducing calcium ions (Ca2+) into the aqueous solutions further confined the transport rate of the piperazine monomer across the reaction interface through the coordination functions between Ca2+ and piperazine molecules, forming a high-flux (15.9 L m–2 h–1 bar–1 at room temperature) NF membrane (PVDF-IP-Ca) with an excellent Na2SO4 rejection (∼98.6%). Impressively, the PVDF-IP-Ca membrane presented an excellent antifouling behavior and performance stability during both fouling and high-temperature filtration tests. The Ca2+-assisted IP (Ca–CIP) strategy is expected to be a facile and universal approach to preparing TFC desalination membranes for HT environmental applications on relatively hydrophobic supports.

Facile preparation of dopamine mediated graphene oxide composite membranes with enhanced stability for nanofiltration: Structure, performance and stability

Stability is a key issue to improve the commercialization of graphene oxide (GO) membranes for aqueous separation. Herein, the effect of dopamine (DA) addition mass on the performance and stability of the DA-mediated GO membranes was systematically investigated. The d-spacing of GO/DA membranes increased from 0.78 to 1.02 nm with DA loading from 0 to 25%. The improvement of water flux for GO/DA membranes was ascribed to the increased hydrophilicity and enlarged d-spacing, but excessive crosslinkers contributed to the declining water flux. The Na2SO4 rejection of GO/DA membranes showed the opposite trend with variations of less than 10%. The 30-day immersed evaluation further validated that the stability of DA-mediated GO membrane improved with increasing DA addition. The spacing modulation and functional groups in the interlayer galleries contributed to the rejection performance and swelling of the GO membranes. The negligible effect of pharmaceutical adsorption on the d-spacing demonstrated the stability of the GO/25%DA membrane. The density functional theory (DFT)-based molecular simulations indicated the GO membranes could be crosslinked by the interaction of polydopamine with the oxygenated groups of GO nanosheets, and the hydration of the residual hydrophilic functional group or the bounded DA monomers of GO was responsible for the slight swelling effect.

Pore size regulation of polyamide composite membrane via a sol-gel process confined within the selective layer

Membrane with pores of homogeneous size distribution is vital to high fraction efficiency of nanofiltration process. In this study, a novel approach of space-confined sol-gel was put forward to regulate the size and distribution of the pores of interfacially synthesized polyamide composite membrane for enhanced fraction efficiency. Tetraethyl orthosilicate (TEOS) was introduced into the porous polyamide network of the selective layer and employed to in situ generate a new silica network through space-confined hydrolysis and condensation. Membrane property including pore size distribution and separation performance was tuned by regulating the content of TEOS and systematically characterized by ATR-FTIR, XPS, SEM, AFM and cross-flow permeation test. The sol-gel of TEOS molecules confined within the selective layer was found to form a new polyamide-silica based separation layer with decreased pore size and homogenized pore size distribution. The mean size in diameter and geometric standard deviation of size distribution of the pores of the virgin polyamide based membrane were about 0.64 nm and 1.32, while those of the desired polyamide-silica based membrane obtained with a TEOS content of 3.0 v/v% were 0.59 nm and 1.26, respectively. The glucose rejection increased significantly from 58.0% of virgin polyamide membrane to 81.5% of the desired polyamide-silica based membrane. Permeation tests with concentrated mixed solution also revealed that, the desired polyamide-silica based membrane possessed better efficiency in the removal of sodium sulfate from the concentrated brine compared to the commercial membrane NF270, showing an average Na2SO4 rejection above 98.3%, a water flux around 120.0 l/m2 h, and nearly no NaCl rejection to a concentrated brine containing 200.0 g/L NaCl and 10.0 g/L Na2SO4 under 30.0 bar and 40.0 °C.

G-C3N4 nanofibers network reinforced polyamide nanofiltration membrane for fast desalination

Enhancing the water permeability of reverse osmosis and nanofiltration (NF) membranes without sacrificing the quality of water production can potentially lead to substantial savings in cost and has considerable practical impact on broad application. Herein, we report a facile fabrication of thin film composite (TFC) NF membrane with crumple polyamide (PA) active layer based on a graphitic carbon nitride (g-C3N4) nanofibers network interlayer via interfacial polymerization, where the g-C3N4 nanofibers network film is formed simultaneously with the formation of PA active layer by a self-deposition process. The special g-C3N4 nanofibers network film possesses ultra-high hydrophilicity, high porosity and relative smooth surface, which is favorable to form a defect-free and crumple PA active layer. The g-C3N4 nanofibers network interlayer assisted TFC NF membrane exhibits a high water flux up to 152 L m-2h−1 (4 bar) while maintains a high salt rejection with Na2SO4 rejection of 98.9%.

Performance regulation of a thin film composite (TFC) NF membrane by low-temperature interfacial polymerization assisted by the volatilization of n-hexane

Reducing the thickness of the polyamide (PA) layer has been confirmed as a feasible strategy to improve the permeability of the thin film composite (TFC) nanofiltration (NF) membrane. In this study, a novel interfacial polymerization (IP) approach assisted by the volatilization of n-hexane was proposed to promote the formation of a thinner PA layer, in which a small amount of n-hexane was added onto the substrate membrane after aqueous phase immersion and before the organic phase coating, then the temperature of the substrate membrane together with the water-soluble monomer solution would be decreased due to the volatilization of n-hexane. The infrared thermographies demonstrated that 7.8 μL cm−2n-hexane dosage was the most efficient, which can sharply decrease the surface temperature from room temperature (25 °C) to 7.9 °C. The TFC membranes prepared at the lower temperature presented much higher permeability. When PIP concentration was 0.3% w/v, TMC concentration was 0.1% w/v and IP reaction time was 40 s, the PA layer formed at this low temperature was smoother and more hydrophilic. Its thickness was reduced from 26.97 nm to 11.98 nm and water permeability was increased by 50% to 36.7 L m−2 h−1 bar−1 while maintaining Na2SO4 rejection of 96.5%.

Enhancing interface compatibility of UiO-66-NH2 and polyamide by incorporating dopamine into thin film nanocomposite membranes

The introduction of nanoparticles into nanofiltration (NF) membranes is an effective approach to improve the NF performance as the construction of water channels in the nanoparticles. However, the poor compatibility between polymer matrix and nanoparticles is a crucial issue that attracts numerous researchers. In this paper, dopamine (DA) molecule was introduced into the aqueous solution for preparing NF membranes by interfacial polymerization to build a bridge between polyamide matrix and nanoparticles (polydopamine coated UiO-66-NH2, U@PD) for its self-polymerization and high reactive activity of abundant of hydroxyl and amino groups. It was found that the addition of DA in aqueous reaction phase solution effectively reduced the membrane surface roughness, anchored more U@PD nanoparticles, improved the hydrophilicity of the membrane, and participated in the interfacial polymerization reaction to crosslink the nanoparticles and the polyamide matrix. The DA introduced TFN membrane achieved high water permeance (13.87 L·m−2·h−1·bar−1) and Na2SO4 rejection (97.96%) with DA concentration of 0.3 g/L, U@PD incorporating amount of 0.3 wt%, cross-linking reaction time of 45 min, and pH of 8.5. Additionally, the as-prepared membrane had an excellent selectivity of Cl−/SO42− (α = 45.85), which was higher than that of the membrane without DA crosslinking agent (α = 14.40). It is concluded that the addition of DA in the interfacial polymerization aqueous solution can effectively repair the defects between the nanoparticles and the polymer, thus provide a new idea for seawater desalination.

MoS2 @PDA thin-film nanocomposite nanofiltration membrane for simultaneously improved permeability and selectivity

Recent studies have documented that the incorporation of nanomaterials can effectively enhance the permselectivity of thin-film composite (TFC) membrane. The distribution and compatibility of molybdenum disulfide (MoS2) nanosheets lack of functional groups within polymer matrices are research hotspots. Here we present polydopamine (PDA) modified MoS2 (MoS2 @PDA) nanosheets as nanofillers to prepare thin-film nanocomposite (TFN) nanofiltration (NF) membrane. PDA not only enhanced the dispersion and compatibility of MoS2 in the polyamide matrices, but also resulted in defect-free TFN membranes due to its self-polymerization. The obtained TFN membrane loaded with 0.01 wt% MoS2 @PDA nanosheets (TFN-0.01) had water permeability of 6.7 L m−2 h−1 bar−1, 1.45 times of the TFC membrane. The Na2SO4 rejection increased from 97.1% to 98.2%, thus overcoming the long-standing permeability-selectivity trade-off of desalination membranes. Moreover, TFN-0.01 NF membrane had excellent long-term stability. Our results showed that PDA can effectively solve the dispersibility and compatibility problems of nanofillers in polymer matrices, especially for the nanofillers lack of functional groups.

2D nanosheets seeding layer modulated covalent organic framework membranes for efficient desalination

Covalent organic frameworks (COFs) are emergent ideal membrane materials, owing to their pre-designable and well-defined pore structures. However, COFs typically exist as solid powder and are hard to dissolve in most solvent, which renders COFs poor processability in membrane formation. In this study, TpPa-SO3H/PAN COF membranes (COFMs) were prepared via counter diffusion method, which is modulated by the pre-assembled two-dimensional (2D) crystalline TpPa-SO3H nanosheets as seeding layer. The TpPa-SO3H seeding layer regulated the diffusion-reaction behavior of monomers and induced the confined growth of TpPa-SO3H COFs, which is favorable for eliminating the intergranular defects inside the TpPa-SO3H/PAN COFMs. The thickness of TpPa-SO3H seeding layer can be controlled by the amount of TpPa-SO3H nanosheets. The charge of the channel wall inside the membrane can fortify the electrostatic repulsion mechanism and facilitate efficient desalination. Under the optimal conditions, the Na2SO4 rejection rate of TpPa-SO3H/PAN COFMs can reach 97.4%. Unlike conventional polyamide membranes whose desalination performance usually decreases with the increase of salt concentration, the TpPa-SO3H/PAN COFMs preserved superior desalination performance toward high salt concentration up to 10,000 ppm.

Fabrication of high-performance nanofiltration membranes by using sulfated cellulose nanofibril as the intermediate support layer

The preparation of high-performance nanofiltration membranes with high permeability and selectivity is a big challenge. Herein, we proposed a novel composite nanofiltration membrane used sulfated cellulose nanofibril (SCNF) to prepare the intermediate support layer. Three SCNFs with different amounts of surface charge was prepared by deep eutectic solvent pretreatment and mechanical treatment. The composite nanofiltration membrane was fabricated with three layers, and physicochemical properties and separation performance of composite nanofiltration were analyzed. The results showed that with the increase of the amount of surface charge of the intermediate support layer of SCNF, the roughness and absolute value of surface zeta potential of the composite nanofiltration membrane all increased, the maximum roughness value was 112 nm, while the absolute value of surface zeta potential was 85 mV. The decreasing of water contact angle indicated that hydrophilicity of composite nanofiltration membrane enhanced. The membrane exhibited high Na2SO4 rejection above 98% and water permeability above 30 L/m2/h under 2 bars. Moreover, the optimal membrane of PES/H-SCNF/PIP-TMC showed the rejection order was Na2SO4 (98.91%) > Mg2SO4 (78.42%) > MgCI2 (49.80%) > NaCI (21.23%) > CaCI2 (12.31%). These outstanding separation characters endowed the membranes with a great prospect in the process of desalination for future application.

2D nanosheets optimized electrospray-assisted interfacial polymerization polyamide membrane with excellent separation performance

Electrospray-assisted interfacial polymerization has recently raised researchers’ attention during membrane fabrication process due to the thickness of the polyamide layer is tunable in nanometers. Here we report that 2D molybdenum disulfide (MoS2) nanosheets could endow the electrospray-assisted interfacial polymerization polyamide membrane with improved selectivity at a short spray time. The nanosheets dispersed uniformly under the electric field. The optimal TFN-15 membrane demonstrated water permeance of 9.23 L m−2 h−1·bar−1 and Na2SO4 rejection of 95.4%. Furthermore, the obtained polyamide membranes showed splendid stability and antifouling. Our research provides an effective strategy for the optimization of the fabrication process of the electrospray-assisted interfacial polymerization polyamide membrane with high-performance.

Negatively charged nanofiltration membrane with high performance via the synergetic effect of benzidinedisulfonic acid and trimethylamine during interfacial polymerization

Negatively charged surface is preferred for thin film composite (TFC) nanofiltration (NF) membrane with excellent separation performance for divalent anions, and ultra-smooth surface is beneficial for antifouling in practical application. Herein a kind of high-flux sulfonated polyamide TFC NF membrane, termed as TFC-BDSA, was successfully fabricated via interfacial polymerization (IP) between the aqueous monomers, 2,2-benzidinedisulfonic acid (BDSA) mixed with piperazine (PIP), and the organic monomer, trimesoyl chloride (TMC), with triethylamine (TEA) as aqueous catalyst. The results proved that BDSA and TEA have synergetic effect on the performance of the fabricated NF membrane. BDSA enabled the formation of more negatively charged, more hydrophilic and much smoother surfaces, which greatly improved the separation performance and antifouling capability of the prepared TFC-BDSA membrane. TEA not only act as an acid receiver, but could form a complex salt with BDSA and thus help to manipulate the diffusion rate of BDSA and PIP as well as the interfacial polymerization process, which helps to form a more smooth, more hydrophilic, more negatively charged, as well as more antifouling and defect-free membrane skin layer. With 1.0 wt% BDSA in the aqueous monomer solution and at pH 11.2 which is adjusted by TEA, the resultant TFC-BDSA membrane displays an excellent water permeance of 122 L m−2h−1 MPa−1, which is more than twice the pristine baseline TFC membrane. Meanwhile, the resultant TFC-BDSA membrane achieved an extremely higher Na2SO4 rejection of 99.6 %, which is more than 2.0 % higher than that of the latter. Moreover, the flux recovery ratios were 101.1 % and 99.5 % (after two cycles of filtration - cleaning) for the TFC-BDSA membrane fouled with sodium alginate and humic acid, respectively, indicating its excellent antifouling performance. Furthermore, the TFC-BDSA membrane shows an excellent operation stability over a 120 h filtration process. In summary, this study provides a new approach to prepare high performance NF membranes for water treatment.

Ultrathin sulfonated mesoporous interlayer facilitates to prepare highly-permeable polyamide nanofiltration membranes

Highly-permeable nanofiltration (NF) membranes are strongly required and have become more crucial with increasing concerns in water treatment and purification. Herein a versatile approach is developed to prepare a highly-permeable polyamide (PA) NF membrane via the traditional interfacial polymerization (IP) process facilitated by an ultrathin sulfonated mesoporous interlayer. A series of the interlayers with a thickness of 110–250 nm and a cut-off around 12 nm is prepared and employed to prepare the PA NF membrane from piperazine (PIP) and 1, 3, 5-benzotriformyl chloride (TMC). Influence factors on the membrane preparation including the interlayer thickness and monomer concentrations are investigated in detail. Sulfonic groups on the interlayer greatly facilitate the PIP adsorption and thus increase the PIP storage in the interlayer, resulting in the formation of a defect-free, 10–50 nm-thick PA membrane at a low monomer concentration. The thickness and surface roughness of PA layer increase with the interlayer thickness simultaneously. Typically, the 40 nm-thick PA membrane has a pure water permeance of high to 36.3 L m−2 h−1 bar−1 with a Na2SO4 rejection of 98.5%. The newly developed approach has a wide application in the preparation of highly-permeable PA membranes for various fields including water treatment and chemical separation.

5-Sulfoisophthalic acid sodium incorporated polyamide nanofiltration membrane with enhanced separation performance

Highly permeable nanofiltration membrane has attracted great attention in energy-efficient liquid separation. However, the preparation of selective membranes with high permeability and good antifouling capability remains challenging. Here we first reported 5-sulfoisophthalic acid sodium (SSIPA) co-deposition for designing crosslinked polymer nanofilm via interfacial polymerization. The composite membranes composed of thinner sulfated polyamide nanofilms (18.0 ± 2.2 nm) had enhanced hydrophilicity and electronegativity as well as smoother surface and enlarger pore size. The SSIPA integrated polyamide nanofiltration membrane presented approximately 4.8 folds pure water flux of the membrane without SSIPA. The prepared membrane suitable for water desalination had 18.0 and 28.3 LHM/bar pure water permeance with the comparable Na2SO4 rejection of 96.3% and 91.8%, respectively. More importantly, the membrane fabricated with a high proportion of SSIPA achieved better dye/salt fraction performance with dye fluxes of 49.3 LMH/bar as well as superior CR rejection (99.0%) and NaCl passage (97%). At the same time, the natural organic matter (BSA, SA) could be almost completely removed. Significantly, the SSIPA-integrated membrane exhibited excellent long-term stability and antifouling capacity. These novel loose TFC membranes with outstanding separation performance provide potential applications for water desalination and organic separation.