High-performance Thin-film Composite Membranes Research Articles

Hyperbranched aromatic poly(amidoamine) mediated interfacial polymerization for high-performance thin film composite membranes

The escalating global demand for clean water has driven a growing interest in developing thin-film composite (TFC) membranes with high permeability and selectivity for wastewater treatment and desalination processes. Engineering polymer materials with precisely tunable properties for selective molecular separation remains a challenging step toward achieving this goal. Herein, we have fabricated a highly permselective asymmetric polyamide nanofilm with a dual-layer structure in which the bottom layer is a porous hyperbranched aromatic polyamide (HBPA) interlayer, and the top layer is a dense polyamide layer with a nanostrip structure. The HBPA porous layer was covalently assembled in situ via oxidative coupling reaction with ammonium persulfate on a polysulfone (PSF) substrate. The hydrophilic porous HBPA interlayer forms nanosized cavities that may enhance the storage and confine amine monomer diffusion, leading to the construction of a striped pattern PA nanofilm. The resulting asymmetric PA membrane exhibits excellent water permeability of 18.39 ± 1 L m−2 h−1 bar−1 (3.98 times that of control membranes) and improved divalent salt (Na2SO4) rejection (≥98 %), surpassing most of the commercial and reported nanofiltration membranes. The HBPA-regulated interfacial polymerization provides a groundbreaking framework for developing high-performance membranes for precisely controlled nanofiltration.

Structurally tuned polyamide membranes via the polyvinylpyrrolidone-modulated interfacial polymerization reaction for enhanced forward osmosis performance

Controllable interfacial polymerization (IP) reaction is an important strategy to fabricate high-performance polyamide (PA) thin-film composite (TFC) membranes. In this work, a new TFC membrane was successfully fabricated by incorporating polyvinylpyrrolidone (PVP) with different molecular weights (K15, K30 and K60) at different concentrations into the aqueous phase of IP process. Due to an increased solution viscosity and interaction between PVP and amine monomers, the lower diffusion rate of amine monomers resulted into a thin (the thinnest basal PA layer of approximately 30 nm) and smooth PA layer with a high crosslinking degree. Among, the optimum PVP K60–0.25 TFC membranes with the highest molecular weights and lower incorporating concentrations had a more positive effect on forward osmosis performance, which presented a pure water flux of 11.2 L m−2 h−1, 25 % higher, and a specific salt flux of 0.04 g L−1, 43 % lower than the original membrane. Our work provides a low-cost and simple approach to obtain high-performance TFC membrane with an improved trade-off effect, and helps to deeply understand the role played by additives in PA layer modulation.

High-performance thin-film composite (TFC) membranes with 2D nanomaterial interlayers: An overview

Thin-film composite (TFC) membranes have been widely used in various separation and purification fields. However, the inherent “trade off” effect limits further improvement in the separation performance. Recently, the construction of nanomaterial interlayers between porous substrates and the selective layer has been widely investigated to enhance the permeability and selectivity of TFC membranes simultaneously. Among the interlayer materials, two-dimensional (2D) nanomaterials possess high lateral size and large aspect ratios and can be stacked to cover the pores on the substrate surface, providing a smooth and flat surface for interfacial polymerization. In this review, we first briefly introduced the effects of 2D nanomaterial interlayers in TFC membranes, including the roles of 2D nanomaterial interlayers in the interfacial polymerization process and in the membrane performance. Then, interlayers prepared from some typical 2D nanomaterials are detailedly discussed for the preparation of high-performance TFC membranes. The 2D nanomaterials include graphene oxide (GO), graphitic carbon nitride (g-C3N4), MXene, covalent organic framework (COF), metal organic frameworks (MOFs), and some other nanomaterials. In the fourth part, we summarized the typical applications (e.g., nanofiltration and gas separation) of the TFC membranes with 2D nanomaterial interlayers. Furthermore, we suggested the challenges and prospects of high-performance TFC membranes based on 2D nanomaterial interlayers.

Dual 2D nanosheets with tunable interlayer spacing enable high-performance self-cleaning thin-film composite membrane

Interlayered thin-film composite (TFC) membranes are promising in overcoming the permeability-selectivity tradeoff of conventional membranes. However, fabricating high-performance TFC membranes with tunable interlayer spacing and antifouling properties remains challenging. Here we develop a high-performance self-cleaning TFC graphene oxide (GO) membrane by employing multifunctional bismuthyl bromide (BiOBr) nanosheets to construct a unique photocatalytic GO@BiOBr interlayer. BiOBr has multiple functions, including regulating the GO nanosheet spacing (i.e., the channel size), mediating the surface properties of the interlayer to enable a desirable selective layer during interfacial polymerization, and imparting photocatalytic properties to the TFC membrane. Because of the dimensional difference between GO and BiOBr nanosheets, the spacing of the dual 2D nanosheets (GO and BiOBr) can be finely tailored by adjusting BiOBr loading. Coupling of the 2D nanosheets enables tunable interlayer properties and a highly thin and selective rejection layer, leading to significantly enhanced separation performance of the TFC membrane. The GO@BiOBr interlayered TFC membrane shows a water permeability of 29.9 L·m−2·h−1·bar−1, which is six times higher than the TFC membrane without an interlayer. The GO@BiOBr interlayered TFC membrane displays 100% rejections to various small molecules (e.g., Rhodamine B, Basic Blue 26 and Ofloxacin). The rise of BiOBr loading in the GO@BiOBr composite increases the interlayer spacing of the dual 2D nanosheets, likely leading to more monomer diffusion and eruptive interfacial polymerization. As a result, thicker and rougher polyamide layers are formed, resulting in decreased water permeability of the TFC membrane. This study presents a viable approach for engineering the next generation of high-performance self-cleaning TFC membranes for reverse osmosis, forward osmosis and nanofiltration within the realm of water treatment.

Enhanced separation performance of composite nanofiltration membranes via electrostatic air spray PSS/PEI interlayer

Thin-film composite (TFC) membranes with an interlayer were prepared extensively for desalination, but the hydrophilicity and permeability were not well improved. In this work, a smooth and hydrophilic interlayer was constructed by electrostatic air spray deposition (EASD) of poly (sodium 4-styrenesulfonate) (PSS) and polyethyleneimine (PEI) on the polyethersulfone substrate and an ultra-thin separation layer was prepared using interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) to acquire high-performance composite nanofiltration (NF) membranes. The polymer solution was atomized into tiny particles under a high-pressure electrostatic air spray effect, facilitating the deposition of PSS/PEI with good homogeneity and enabling a denser and smoother interlayer surface. The introduction of PSS/PEI enhanced the hydrophilicity of TFC membranes and increased the repulsion of divalent cations to improve the salt rejection. The impacts of PEI concentration and EASD time on the separation performance of NF membrane were explored. The optimized TFC-3 NF membrane had a permeate flux of 74.5 ± 1.6 L·m−2·h−1 under 0.5 MPa, which was 2.5 times higher than the water flux of conventional TFC-0 membrane, while retaining up to 99.2 ± 0.5 % of Na2SO4. This work provides a prospective strategy to develop high-performance TFC membranes with great extensive progress for seawater purification.

Biomimetic peptoid-assisted fabrication of antibiofouling thin-film composite membranes

Polyamide (PA) thin-film composite (TFC) membranes are extensively used in water purification but suffer from chronic biofouling, which has spurred extensive research on the development of antibiofouling membranes. In this study, we present a facile method to fabricate a biofouling-resistant, high-performance PA TFC membrane by adding a biomimetic antimicrobial peptoid (i.e., oligo-N-substituted glycines) to the reaction medium during an interfacial polymerization (IP) process. The amphiphilic peptoid facilitates IP by acting like a surfactant, thereby enabling the formation of a highly crosslinked and permeable PA separation layer. Consequently, the peptoid-added TFC (pept-TFC) membrane exhibits superior separation performance compared with pristine, commercial, and other laboratory-made TFC membranes. Furthermore, because the peptoid is strongly incorporated into the PA separation layer network, the resultant pept-TFC membrane is endowed with excellent antimicrobial and antibiofouling properties. Importantly, the enhanced separation and antibiofouling performances of the pept-TFC membrane persist during long-term membrane operation, indicating the robust implantation of the peptoid and permanent changes in the structure and properties of PA. The proposed strategy provides a versatile and environmentally benign platform for fabricating functional membranes by simply employing structurally tailored peptoids with specific functions.

Synergistic effect between tannic acid-Fe3+ and chitosan hydrogel-coated covalent organic framework: Endowing better nanofiltration performance and stability

The weak interfacial interaction of nanomaterials and substrate is an important factor affecting the stability and rejection of nanofiltration membranes. Herein, two materials of covalent organic framework modified by chitosan hydrogels (CH@COF) and tannic acid (TA)-Fe3+ served as an interlayer of the thin-film composite (TFC) membrane to overcome this problem. The synergistic effect between CH@COF and TA-Fe (such as constructing stable chemical bonds between the polyamide layer and substrate, increasing the degree of cross-linking of the polyamide layer, and decreasing its thickness) endows the TFC/TA-Fe(CH@COF) membrane with excellent nanofiltration performance and stability. Its water permeability was 16.17 L m−2 h−1 bar−1, which was 185% of that of the TFC-control membrane (8.74 L m−2 h−1 bar−1), and the rejections of the membrane for norfloxacin, ciprofloxacin, and ofloxacin were 94.89%, 99.07%, and 99.10%, respectively. In addition, its flux recovery rate (FRR) values for high-concentration sodium alginate and bovine serum albumin were 98.32% and 97.99%, respectively, indicating outstanding antifouling performance. This work emphasizes the synergy and potential of different materials as an interlayer in high-performance TFC membranes.

Construction of high-performance thin-film composite membrane for CO2 separation via interface engineering

High-efficiency CO2 capture has become increasingly vital for alleviating the ongoing global temperature which leads to severe impacts on virtually every aspect of human life. Thin-film composite membranes (TFCM) have attracted growing attention for conducting CO2 capture, owning to their energy-efficient and environment-friendly merits. However, the nonideal interface between the gutter layer and the separation layer hampers the fabrication of defect-free and thin separation layer, which renders low separation performance. In this work, we developed a strategy, i.e., coupling the oxygen-plasma modification with spin-coating, for engineering the interface between the gutter layer and separation layer of TFCM. Leveraging this idea, the TFC membrane, consisting polydimethylsiloxane (PDMS) served as the gutter layer and poly (ether-block-amide) (PEBA) as the thin separation layer, was manufactured by conveniently spin-coating PEBA solution on the oxygen-plasma-treated PDMS layer. The optimized PEBA-based TFCM membrane realized superior separation performance, e.g., a CO2 permeance of 2011 GPU, a CO2/N2 selectivity of 24, and 100-hour stably running, which outperformed most of the reported PEBA-based TFCM. Thus, the interface engineering strategy proposed in this study opens a new door for rational fabrication of high-performance TFCM.

Polymer-Infiltrated Metal–Organic Frameworks for Thin-Film Composite Mixed-Matrix Membranes with High Gas Separation Properties

Thin-film composite mixed-matrix membranes (TFC-MMMs) have potential applications in practical gas separation processes because of their high permeance (gas flux) and gas selectivity. In this study, we fabricated a high-performance TFC-MMM based on a rubbery comb copolymer, i.e., poly(2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] ethyl methacrylate)-co-poly(oxyethylene methacrylate) (PBE), and metal-organic framework MOF-808 nanoparticles. The rubbery copolymer penetrates through the pores of MOF-808, thereby tuning the pore size. In addition, the rubbery copolymer forms a defect-free interfacial morphology with polymer-infiltrated MOF-808 nanoparticles. Consequently, TFC-MMMs (thickness = 350 nm) can be successfully prepared even with a high loading of MOF-808. As polymer-infiltrated MOF is incorporated into the polymer matrix, the PBE/MOF-808 membrane exhibits a significantly higher CO2 permeance (1069 GPU) and CO2/N2 selectivity (52.7) than that of the pristine PBE membrane (CO2 permeance = 431 GPU and CO2/N2 selectivity = 36.2). Therefore, the approach considered in this study is suitable for fabricating high-performance thin-film composite membranes via polymer infiltration into MOF pores.

High-performance thin-film composite membrane consisting of a single layer of m-phenylenediamine/trimesoyl chloride fabricated via spin-assisted molecular layer-by-layer assembly

High-performance thin-film composite membrane consisting of a single layer of m-phenylenediamine/trimesoyl chloride fabricated via spin-assisted molecular layer-by-layer assembly

A Facile Strategy toward the Preparation of a High-Performance Polyamide TFC Membrane with a CA/PVDF Support Layer.

In this study, polyamide (PA) thin-film composite (TFC) nanofiltration membranes were fabricated via interfacial polymerization on cellulose acetate (CA)/poly(vinylidene fluoride) (PVDF) support layers. Several types of CA/PVDF supports were prepared via the phase inversion method. With increasing CA, the PVDF membrane surface pore size decreased and hydrophilicity increased. The effect of the support properties on the performance and formation mechanism of PA films was systematically investigated via an interfacial polymerization (IP) process. The permselectivity of the resulting TFC membranes was evaluated using a MgSO4 solution. The results show that the desired polyamide TFC membrane exhibited excellent water flux (6.56 L/(m2·h·bar)) and bivalent salt ion rejection (>97%). One aim of this study is to explore how the support of CA/PVDF influences the IP process and the performance of PA film.

Using Cu-TCPP Nanosheets as Interlayers for High-Performance Organic Solvent Nanofiltration Membranes

The development of highly permeable and selective thin-film composite (TFC) membranes is essential for organic solvent nanofiltration (OSN) applications. However, overcoming the permeability–selectivity trade-off in polymer membranes remains highly challenging owing to the difficulty in controlling the thickness and nanostructures of the selective layers. In this study, TFC OSN membranes with sandwich-like structures were developed via interfacial polymerization on Cu-TCPP nanosheet-modified microporous polyvinylidene fluoride (PVDF) substrate surface. The interfacial polymerization was done by using mixed amine (polyethyleneimine and piperazine) in the aqueous phase and the 1,3,5-benzenetricarbonyl trichloride in the hydrophobic ionic liquid phase as monomers. It was found that the Cu-TCPP nanosheets of micrometer lateral dimensions and nanometer thickness (1.5 ± 0.6 nm) can be deposited on the PVDF substrate as an interlayer to facilitate the following interfacial polymerization reaction. The Cu-TCPP interlayer also can be served as a binder between the polyamide selective layer and the microporous PVDF substrate to enhance their mechanical strength. As compared with the PVDF/PA membrane, the PVDF/t-Cu-TCPP/PA membrane exhibited higher elongation (8.0 vs. 4.6%) while ensuring slightly lower tensile strength (36.0 vs. 48.6 MPa). Under optimal synthetic conditions, the TFC membranes could achieve 2.7 L m–2 h–1 bar–1, and 98.9% and 95.0% rejection to Brilliant Blue R (826 Da) and Congo red (697 Da), respectively, in ethanol. Furthermore, the membranes showed steady performance throughout the 36 h nanofiltration of the Rose bengal/ethanol mixture and exhibited good performance in the concentration of lecithin in methanol. Accordingly, this work highlights the potential of using thin metal–organic framework nanosheets as interlayers to develop high-performance TFC membranes for OSN applications.

Metal-assisted multiple-crosslinked thin film composite hollow fiber membrane for highly efficient bioethanol purification

Polyamide (PA)-based thin film composite (TFC) membranes have been extensively applied in various membrane-based separations. However, research works for bioethanol purification are relatively limited due to insufficient hydrophilicity and chain packing density of the PA selective layer by conventional interfacial polymerization. In this work, a new TFC hollow fiber (HF) membrane is fabricated by metal-assisted multiple crosslinking strategy, that is, metal-coordinated crosslinking of the pristine PA layer and coordination complexation between metal ions and phytic acid (PhA) for advanced water/ethanol separation. By tuning coordination abilities of metal ions with PA and PhA and the cycle number of PhA/metal ion assembly, PA-based TFC HF membrane is perfected. Additionally, a joint experiment/simulation characterization is deployed to reveal the coordination abilities of various metal ions with the pristine PA and grafted PhA. Ultimately, the synergistic effect between PA layer and PhA-metal ion complexes (i.e., 1 + 1 > 2 effect) is embodied in the separation performance of water/ethanol separation. The resulting TFC-Fe3+-PhA membrane with the strongest PhA-metal ion coordination ability exhibits the best water/ethanol separation performance, i.e., the separation factor of 1703 (34 times higher than pristine PA TFC HF membrane) and total flux of 1705 g/m2 h. This metal-assisted multiple crosslinking strategy is therefore believed to shed important lights on the development of next-generation high-performance TFC membranes for bioethanol purification.

Air plasma assisted spray coating of Pebax-1657 thin-film composite membranes for post-combustion CO2 capture

With recent focus on achieving carbon neutrality to tackle global warming, there is an increasing need for advanced carbon capture technology to reduce carbon emission to the atmosphere. Membrane separation is one of such technologies that can remove carbon dioxide (CO2) in an energy-efficient and cost-effective way. In particular, the well-studied thin-film composite (TFC) membranes based on commercial polyethylene oxide (PEO)-containing materials have demonstrated strong promise for large-scale industrial post-combustion CO2 capture. However, to realize high-performance PEO-based TFC membranes, a key challenge lies in maximizing the reduction in the thickness of the selective layer without compromising membrane integrity, which to date has achieved little progress probably due to the failure in addressing the poor selective/gutter layer interfacial compatibility issue. Here, we adopted a facile spray coating method to design a TFC membrane comprising an ultrathin Pebax-1657 selective layer, a polydimethylsiloxane (PDMS) gutter layer, and a porous polysulfone (PSF) substrate. To increase surface hydrophilicity and wettability for enhancing interfacial compatibility between the selective and gutter layers, the surface of the PDMS gutter layer was activated for a few seconds by air plasma prior to Pebax-1657 spray coating. Coupled with well-controlled spray coating manipulation, a defect-free Pebax-1657 selective layer with an ultrathin thickness as low as 30 nm could be formed. Correspondingly, the optimized TFC membrane exhibited a highest CO2 permeance at 2022 GPU with a CO2/N2 selectivity of close to 30.0, far surpassing the threshold for commercially viable post-combustion CO2 capture (CO2 permeance ≥1000 GPU and CO2/N2 selectivity ≥20). More importantly, the use of spray coating endows the TFC design with great scalability potential, rendering our membranes, which are made solely from commercially available materials, highly relevant for industrial CO2 separation.

A zwitterionic copolymer-interlayered ultrathin nanofilm with ridge-shaped structure for ultrapermeable nanofiltration

Interlayered thin-film composite (TFC) membranes have a great potential for enhancing salt separation in wastewater reclamation, because of the highly permeable and selective properties. However, mechanistic insights regarding the structural features of the surface nanofilms and their corresponding interlayers, which lead to enhanced separation efficiency, remain poorly understood. Herein, we report a zwitterionic copolymer 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-amino-ethyl methacrylate hydrochloride (AEMA) (P[MPC-co-AEMA]) interlayered TFC membrane that exhibits an ultrahigh water permeance of 20.4 L m−2 h−1 bar−1 (almost three folds higher water permeance than that of the pristine PA membrane), together with a simultaneously enhanced rejection of inorganic salts (96.8% against Na2SO4). Detailed mechanistic investigations revealed that the promoted membrane separation property was mainly explained as the enriched amine monomer diffusion-driven instability induced by the P[MPC-co-AEMA] interlayer. This triggers membrane sealing and inhibits its growth, leading to the formation of an ultrathin PA nanofilm with a thickness of 12 nm, a ridge-shaped surface structure with enhanced specific surface area, and enhanced crosslinking. The fundamental mechanism revealed in this study lays a solid foundation for the engineering of the high-performance TFC membrane, which is appealing for the energy-efficient water remediation industry.

Interfacial polymerization of thin film selective membrane layers: Effect of polyketone substrates

Thin film composite (TFC) membranes are the most widely used technology in reverse osmosis (RO)-based desalination processes, due to their desirable separation performance derived from the combined structure of the porous support and thin film active layer. Typically, TFC membranes are fabricated via an interfacial polymerization (IP) technique, where the porous substrate plays an indispensable role in forming the thin film layer. In this study, a porous polyketone membrane with a fibrous structure and intrinsically moderate hydrophilicity prepared using non-solvent induced phase separation (NIPS) was employed as the substrate to explore its suitability for fabricating high-performance TFC membranes. Investigations on structure control and chemistry regulation via the NIPS process and in-situ post-treatment revealed that porous polyketone substrates display different morphologies and chemistries, significantly altering the thin layer formation during IP. The resulting TFC membranes exhibited up to 14-fold permeance difference, which was attributed to the variance of “ridge-and-valley” structures in different thin film layers formed on different polyketone substrates. It was found that a polyketone membrane with an appropriate surface roughness could generate favorable “ridge-and-valley” structures in the thin film layer to enhance the surface area, realizing high water permeance as well as high salt rejection in reverse osmotic desalination of NaCl solution.

Ultrapermeable Composite Membranes Enhanced Via Doping with Amorphous MOF Nanosheets.

Thin-film composite (TFC) polymeric membranes have attracted increasing interest to meet the demands of industrial gas separation. However, the development of high-performance TFC membranes within their current configuration faces two key challenges: (i) the thickness-dependent gas permeability of polymeric materials (mainly poly(dimethylsiloxane) (PDMS)) and (ii) the geometric restriction effect due to the limited pore accessibility of the underlying porous substrate. Here we demonstrate that the incorporation of trace amounts (∼1.8 wt %) of amorphous metal–organic framework (MOF) nanosheets into the gutter layer of TFC assemblies can simultaneously address these two limitations by the creation of rapid, transmembrane gas diffusion pathways. The resultant PDMS&MOF membrane displayed excellent CO2 permeance of 10450 GPU and CO2/N2 selectivity of 9.1. Leveraging this strategy, we successfully fabricate a novel TFC membrane, consisting of a PDMS&MOF gutter and an ultrathin (∼54 nm) poly(ethylene glycol) top selective layer via surface-initiated atom transfer radical polymerization. The complete TFC membrane exhibits excellent processability and remarkable CO2/N2 separation performance (1990 GPU with a CO2/N2 ideal selectivity of 39). This study reveals a strategy for the design and fabrication of a new TFC membrane system with unprecedented gas-separation performance.

Intrinsically antibacterial thin film composite membranes with supramolecularly assembled lysozyme nanofilm as selective layer for molecular separation

Biofouling is a pervasive and crucial issue in membrane separation processes, as it leads to the deterioration in separation efficiency. To address this issue, the antibacterial membrane with high biofouling resistance is in urgent demand, what has been remained challenging. In this work, an intrinsically antibacterial thin film composite (TFC) membranes was prepared using supramolecularly assembled lysozyme (SAL) nanofilm as a selective layer. The nanofilms were achieved by depositing onto a hydrolyzed polyacrylonitrile (h-PAN) support membrane using phase transition and aggregation of lysozyme from its aqueous solution. The prepared membranes showed a high rejection ratio towards vitamin B12 (95.3%) with a water permeation flux of 48.6 L·m−2·h−1 under 0.4 MPa, showing great potential in the molecular separation. Furthermore, the antibacterial efficiencies of the typical membrane toward E. coli and S. aureus reached 93.2% and 92.2%, respectively, indicating that the SAL selective layer can effectively resist bacterial adhesion and reproduction on the membrane surface. This work provides an innovative strategy and insight in fabricating the high-performance antibacterial TFC membranes for aqueous molecular separation via protein supramolecular assembly.

Fabrication of High-Performance Thin-Film Composite Nanofiltration Membrane by Dynamic Calcium-Carboxyl Intra-Bridging during Post-Treatment.

Widespread applications of nanofiltration (NF) and reverse osmosis (RO)-based processes for water purification and desalination call for high-performance thin-film composite (TFC) membranes. In this work, a novel and facile modification method was proposed to fabricate high-performance thin-film composite nanofiltration membrane by introducing Ca2+ in the heat post-treatment. The introduction of Ca2+ induced in situ Ca2+-carboxyl intra-bridging, leading to the embedment of Ca2+ in the polyamide (PA) layer. This post modification enhanced the hydrophilicity and surface charge of NF membranes compared to the pristine membrane. More interestingly, the modified membrane had more nodules and exhibited rougher morphology. Such changes brought by the addition of Ca2+ enabled the significant increase of water permeability (increasing from 17.9 L·m−2·h−1·bar−1 to 29.8 L·m−2·h−1·bar−1) while maintaining a high selectivity (Na2SO4 rejection rate of 98.0%). Furthermore, the intra-bridging between calcium and carboxyl imparted the NF membranes with evident antifouling properties, exhibiting milder permeability decline of 4.2% (compared to 16.7% of NF-control) during filtration of sodium alginate solution. The results highlight the potential of using Ca2+-carboxyl intra-bridging post-treatment to fabricate high-performance TFC membranes for water purification and desalination.

Improving the water permeability and antifouling property of the nanofiltration membrane grafted with hyperbranched polyglycerol

This study evaluated the performance of the high performance nanofiltration (NF) membrane by grafting the recently developed hyperbranched polyglycerol (hPG) with a unique three-dimensional (3D) globular structure and superhydrophilicity on thin-film composite (TFC) polyamide layer. The hPG modified TFC (hPG-TFC) NF membrane possessed an outstanding hydrophilic surface and high permeance without compromising salt rejection. Compared with the pristine TFC membrane, the hPG modified membrane exhibited a permeate flux increase of 30% while maintaining Na2SO4 rejection of 97%. Irrespective of foulants, the hPG grafted TFC persistently generated an enhanced antifouling ability. Among the model foulants, the humid acid shows the most severe fouling potential for NF membranes. Notwithstanding, the hPG-TFC exhibits an improved normalized water flux of 65% and flux recovery of 75%, much higher than the pristine TFC membrane (44% and 47%, respectively). In addition, in order to better understand the antifouling behavior of our hPG modified NF membranes, the Q-sense quartz-crystal microbalance with dissipation (QCM-D) was used to determine both the adsorption rate and amount of model foulants on the membrane surface. Therefore, the successful application of 3D hPG polymers on the NF membrane should serve as a source of inspiration for the surface engineering of high performance TFC membrane with high water permeability and enhanced antifouling performance in pressure-driven NF membrane processes.