Polyamide Thin-film Nanocomposite Membranes Research Articles

Salt-responsive polyamide thin-film nanocomposite membrane based on zwitterionic polymeric nanoparticles for high-efficient dye desalination

To simultaneously improve the water permeability, selectivity, and antifouling properties of polyamide nanofiltration (NF) membranes in textile wastewater treatment, we fabricated a salt-responsive thin-film nanocomposite (TFN) membrane with the incorporation of zwitterionic polymeric nanoparticles (ZNPs) into polyamide selective layer. Herein, the ZNPs were synthesized via an inverse miniemulsion polymerization with zwitterionic monomer, amino monomer, and cross-linker reagent. The salt-responsive property of ZNPs rendered their resultant membranes TFN-ZNPs with adjustable microstructure and separation performance via varying the sodium chloride (NaCl) concentration in water. The water permeance of TFN-ZNPs was enhanced to be 1.7 times that of its pure water permeance with the 10 g L−1 NaCl solution, and the salt-responsive behavior was reversible. Moreover, this salt-responsive property endowed the membrane with outstanding separation performance for the salt/dye or dye/dye mixtures. The selectivity of TFN-ZNPs to NaCl/congo red and methyl orange/neutral blue was enhanced to ∼104 and ∼127, respectively. The TFN-ZNPs with salt-responsive property also exhibited an improved antifouling performance, i.e., the flux recovery ratio was enhanced from 85.6 % to 96.5 % by washing with NaCl solution instead of deionized water. Thus, this work provided a paradigm shift in the fabrication of salt-responsive TFN membranes for the highly efficient separation of organic molecules and inorganic salts and wastewater treatment.

Engineering Interfacial Structure and Channels of Polyamide Thin-Film Nanocomposite Membranes to Enhance Permselectivity for Water Purification

Engineering Interfacial Structure and Channels of Polyamide Thin-Film Nanocomposite Membranes to Enhance Permselectivity for Water Purification

In-situ interfacial polymerization of polyamide TFN membranes by adding a diamino-silane coupling agent: Toward enhanced desalination performance

The primary challenge faced by thin film nanocomposite (TFN) membrane in nanofiltration (NF) process is to effectively resolve the trade-off effect between permeability and selectivity. Herein, a polyamide (PA) TFN membrane with enhanced NF performance was prepared through in-situ interfacial polymerization (in-situ IP) method, using piperazine (PIP) and 3-diamino-methyl-cyclohexyl triethoxysilane (DTES) as co-amine monomers to undergo a reaction with 1,3,5-benzenetricarbonyl trichloride (TMC). This study investigated the effects of DTES on the surface chemical composition, morphologies, hydrophilicity, separation efficiency, and anti-fouling properties of the novel DTES/PIP/TMC TFN membranes. It was found that SiO2 nanoparticles were generated in-situ from the reacted DTES through hydrolysis and self-condensation, resulting in their uniform distribution within the formed PA selective layer with high compatibility and without aggregation. The optimal PA TFN membrane was achieved by adjusting the ration of Si-OH group in formed SiO2 nanoparticles through varying the concentration of DTES concentration. Meanwhile, the induction of SiO2 into the PA layer resulted in an enlargement in membrane pore size and improved surface hydrophilicity. When the concentration of added DTES was 0.333 wt%, the optimal PA TFN membrane (TFN-4) exhibited the highest quantity of formed Si-OH groups, resulting in the excellent performance, including a markedly enhanced water permeability flux of 76.8 L·m−2·h−1 (2-fold larger than that of the pure TFC membrane), a great Na2SO4 rejection of 97.5 %, and a superior Cl−/SO42− permeation selectivity of 46.0. Moreover, the TFN-4 membrane exhibited exceptional stability and superior antifouling properties attributed to its unparalleled hydrophilicity. This work provided a strategy for preparing uniform and high-performance TFN membranes.

Effect of functionalized nanodiamonds and surfactants mediation on the nanofiltration performance of polyamide thin-film nanocomposite membranes

Effect of functionalized nanodiamonds and surfactants mediation on the nanofiltration performance of polyamide thin-film nanocomposite membranes

Reticulated Polyamide Thin-Film Nanocomposite Membranes Incorporated with 2D Boron Nitride Nanosheets for High-Performance Nanofiltration.

Nanofiltration (NF) technology has been widely used in saline wastewater treatment due to its unique separation mechanism. However, the NF membrane, as the core of the nanofiltration technology, is restricted by the trade-off between permeability and selectivity, which greatly restricts the development of NF membranes. The interlamellar arrangement of 2D boron nitride nanosheets (BNNSs) can provide additional transport channels and selectivity, as well as strong adsorption capacity due to its high specific surface area, exhibiting significant potential for advanced membranes. In this work, BNNSs prepared by tannic acid (TA)-assisted exfoliation (TA@BNNSs) were successfully adopted to fabricate thin-film nanocomposite (TFN) membranes via interfacial polymerization (IP). The resultant TFN membranes' structure and properties were systematically characterized via various methods. The results demonstrated that the surface morphology of polyamide membranes evolved gradually from a nodular structure to a reticular topography, accompanied by the decrease of the thickness of the polyamide selective layer when incorporating TA@BNNSs into the membranes. This phenomenon can be mainly ascribed to that the uptake density and diffusion of piperazine (PIP) monomer were effectively regulated by BNNSs. This is validated by molecular dynamics and revealed by the adsorption of PIP in BN models, the diffusion coefficients, and interaction energies, respectively. In addition, the TFN membranes demonstrated improved permeance and stable solute rejection for the inorganic salts. Specifically, the water flux of PA-TA@BNNSs-10%/PMIA membrane could reach up to 109.1 ± 2.49 L·m-2·h-1 while keeping a high rejection of 97.5 ± 0.38% to Na2SO4, which was superior to most of the reported membranes in the literature. Besides, the PA-TA@BNNSs-10%/PMIA membrane exhibited an excellent stability in the long-term filtration process. The finding in this work provides a potential strategy for developing the next-generation 2D material-based membranes with high-performance for separation applications.

Fabrication of polyamide thin film nanocomposite membranes with enhanced desalination performance modified by silica nanoparticles formed in-situ polymerization of tetramethoxysilane

The high separation performance polyamide (PA) thin film nanocomposite (TFN) reverse osmosis (RO) membrane for desalination was fabricated by incorporating the silica nanoparticles formed by in-situ polymerization of TMOS in the polyamide layer. The different contents and mixing methods of TMOS were investigated. The in-situ synthesized silica was uniformly embedded in the PA layer because TMOS could be fully dissolved in the organic phase solution. The agglomeration and uneven dispersion of traditional nanofillers in the polyamide layer were avoided. The best performance TFN membrane was prepared by mixing 0.8 wt% TMOS in organic phase solution and interfacial polymerization for 2 min. For brackish water desalination and high-pressure seawater desalination, the water flux of best performance membrane reached 58.4 L m−2 h−1 and 72.77 L m−2 h−1 respectively, which was 3 times and 2.6 times of that of pure polyamide thin film composite (TFC) membrane, while maintaining a satisfactory salt rejection (NaCl, 98.5%). The anti-fouling and long-term stability performance of prepared TFN membrane were also superior. This work demonstrated the potential of TMOS in-situ synthesis of nanofillers embedded in PA layer to prepare TFN membrane with high separation performance, and provided a new idea for simple preparation of TFN membrane.

Polyamide thin film nanocomposite membranes with in-situ integration of multiple functional nanoparticles for high performance reverse osmosis

Polyamide (PA) thin film nanocomposite (TFN) reverse osmosis (RO) membranes have been vigorously developed, which could be used in saline water desalination, wastewater treatment and chemicals separation and purification. Aiming at further improving the TFN RO membrane comprehensive performances, such as the perm-selectivity, stability and anti-fouling/-microbial properties remains a great challenge. Herein, we proposed a biomimetic nanoparticle redox strategy to in-situ integration of multiple functional nanoparticles, i.e., biomimetic nanoparticles (BNPs) and silver (Ag) nanoparticles into the PA matrix for simultaneously regulating the membrane microstructure and optimizing the surface property. A much hydrophilic selective layer with interior transporting channel structure renders the resultant RO membrane PA-BNP-Ag with an enhanced water permeance of ∼4.2 L m−2·h−1bar−1 without sacrificing NaCl rejection (∼98.1%). The BNPs induce Ag nanoparticles uniformly distributed within the PA matrix, which significantly improves the membrane anti-fouling/-bacterial property. The water flux recovery ratio of PAM-BNP-Ag was improved to be higher than 96% during several cycles filtration of saline solution containing bovine serum albumin foulants. More importantly, the membrane sterilization rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) achieves nearly 100%. This work provides a new strategy for the construction of advanced PA TFN membranes with both high perm-selectivity and anti-fouling/-microbial property in RO desalination.

Enhanced Separation Performance of Polyamide Thin-Film Nanocomposite Membranes with Interlayer by Constructed Two-Dimensional Nanomaterials: A Critical Review.

Thin-film composite (TFC) polyamide (PA) membrane has been widely applied in nanofiltration, reverse osmosis, and forward osmosis, including a PA rejection layer by interfacial polymerization on a porous support layer. However, the separation performance of TFC membrane is constrained by the trade-off relationship between permeability and selectivity. Although thin-film nanocomposite (TFN) membrane can enhance the permeability, due to the existence of functionalized nanoparticles in the PA rejection layer, the introduction of nanoparticles leads to the problems of the poor interface compatibility and the nanoparticles agglomeration. These issues often lead to the defect of PA rejection layers and reduction in selectivity. In this review, we summarize a new class of structures of TFN membranes with functionalized interlayers (TFNi), which promises to overcome the problems associated with TFN membranes. Recently, functionalized two-dimensional (2D) nanomaterials have received more attention in the assembly materials of membranes. The reported TFNi membranes with 2D interlayers exhibit the remarkable enhancement on the permeability, due to the shorter transport path by the "gutter mechanism" of 2D interlayers. Meanwhile, the functionalized 2D interlayers can affect the diffusion of two-phase monomers during the interfacial polymerization, resulting in the defect-free and highly crosslinked PA rejection layer. Thus, the 2D interlayers enabled TFNi membranes to potentially overcome the longstanding trade-off between membrane permeability and selectivity. This paper provides a critical review on the emerging 2D nanomaterials as the functionalized interlayers of TFNi membranes. The characteristics, function, modification, and advantages of these 2D interlayers are summarized. Several perspectives are provided in terms of the critical challenges for 2D interlayers, managing the trade-off between permeability, selectivity, and cost. The future research directions of TFNi membranes with 2D interlayers are proposed.

Post-synthetic modification of MOFs to enhance interfacial compatibility and selectivity of thin-film nanocomposite (TFN) membranes for water purification

Efficient discrimination of ions and small neutral contaminants remains a challenge for polyamide thin-film nanocomposite (TFN) water separation membranes due to the presence of interfacial defects and particle-agglomeration-induced nonselective voids in the polyamide layer. In this work, highly selective TFN membranes were successfully fabricated by leveraging post-synthetic modifications of (3-glycidyloxypropyl)triethoxysilane (GPTES) and trimesoyl chloride (TMC) on MIL-101(Cr)–NH2 MOF filler nanoparticles. GPTES modification suppresses particle agglomeration during interfacial polymerization for membrane formation by forming a stable particle suspension in the organic monomer solution, while TMC-induced in situ chemical crosslinking between filler particles and polyamide addresses the phase compatibility and interfacial issues at the filler–polyamide interface. The resulting TFN membranes show high NaCl, MgCl2, Na2SO4, and MgSO4 rejections of 99.0–99.6% at 150 psi with a water permeance of 0.9 L m−2 h−1 bar−1. Compared to the thin-film composite (TFC) control membrane, the incorporation of the MOF particles yields a 53.0% and 24.5% increase in water permeance and NaCl rejection. Importantly, the TFN membranes also exhibit excellent rejections to small neutral contaminants such as PEG200 (99.2% rejection) and boric acid (89.0% rejection at a pH value of 7.5) at a relatively low pressure of 150 psi, which is higher than the respective value obtained by the commercial Dow SW30XLE TFC control membrane at the same conditions. The outstanding long-term performance stability revealed the robust structure of the MOF TFN membranes. Our results demonstrate a facile strategy to effectively control particle agglomeration and interfacial defects in polyamide TFN membranes by manipulating the surface chemistry of the filler nanoparticles, which can be applied to the fabrication of effective TFN membranes with molecular level size-exclusion selectivity.

Catalytic TFN membranes containing MOF loaded Ag NPs prepared by interfacial polymerization

Efficiency and sustainability of catalytic thin-film nanocomposite (TFN) membranes are crucially important for the reverse-osmosis performance of thin film composite (TFC) membranes in many fields. Herein, Ag@UiO-66-NH 2 catalytic nanoparticles were fabricated and incorporated into the polyamide active layer through by covalent bond via the interfacial polymerization (IP) method. Polyamide TFN membranes with high efficiency, sustainable catalytic degradation of Rhodamine B (RhB), and excellent self-cleaning performance were prepared conveniently. The 0.8 wt % Ag@UiO-66-NH 2 composite membrane has excellent permeability stability, and the flux recovery rate can reach 81.6% after 7 runs. In addition, the degradation rate of RhB can reach 99.6% by using this membrane. More importantly, the degradation efficiency of 250 mL RhB solution can still reach 94.5% after 7 cycles of catalytic test. The degradation effect of RhB by the TFN membranes was enhanced significantly owing to the synergistic effect of the adsorption and catalytic properties of Ag@UiO-66-NH 2 nanoparticles. Moreover, it provides a universal method for preparing TFN membrane with a catalytic active layer, which can be applied in other fields of catalytic film by replacing Ag NPs with other particles. • Polyamide TFN membrane containing Ag@UiO-66-NH 2 is prepared via interfacial polymerization method. • Ag@UiO-66-NH 2 nanoparticles are incorporated into the polyamide active layer through by covalent bond. • Catalyst powder Ag@UiO-66-NH 2 improves comprehensive performance of the polyamide TFN membrane. • Polyamide TFN membrane containing Ag@UiO-66-NH 2 exhibits excellent catalytic performance and cyclic stability.

Ultra-smooth and ultra-thin polyamide thin film nanocomposite membranes incorporated with functionalized MoS2 nanosheets for high performance organic solvent nanofiltration

Organic solvent nanofiltration (OSN) membranes are the key factors for the treatment of organic solution via OSN technology. In this work, we fabricated a kind of ultra-thin and ultra-smooth thin-film nanocomposite (TFN) OSN membrane using interfacial polymerization (IP) process with ultra-low concentration for both the aqueous and the organic monomers, together with doped tannic acid (TA) functionalized Molybdenum disulfide (MoS2) nanosheets of ultra-low content in the aqueous monomer solution, and followed by post-IP chemical crosslinking and solvent activation procedures. The results demonstrated that the incorporated TA-MoS2 nanosheets not only help to promote the solvent permeation, but also help to increase the solvent resistance and fouling resistance of the fabricated membrane. The optimal TFN OSN membrane fabricated using 0.05 wt% aqueous m-phenylenediamine (MPD) solution doped with TA-MoS2 nanosheets content of 50 mg L−1 and 0.0025 wt% trimesoyl chloride (TMC) / n-hexane solution has an ultra-thin barrier layer, with an average thickness of about 15 nm. This endows it a much higher pure DMF permeance of 219.1 L m−2 h−1 MPa−1, which is much superior over most of literature works. Meanwhile, the fabricated TFN OSN membrane achieves a rejection of 99.1 % for rhodamine B (RDB, 479 Dalton), which is about 10.1 % increment compared with that of the baseline thin-film composite (TFC) membrane. The TFN OSN membrane also features an ultra-smooth skin layer, with a surface roughness of merely about 2.0 nm, which is quite beneficial for its fouling resistance performance. Moreover, the TFN OSN membrane features outstanding high solvent resistance. It remained a nearly constant and extremely high rejection for Rose Begal (RB, 1017 Dalton), about 99.9 %, and a much higher DMF permeance, 101 ± 2 L m−2 h−1 MPa−1, after cross-flow filtration for more than 200 h using 100 mg L−1 RB / DMF solution as feed, which is seldomly reported in literature. Even being immersed in DMF at 80 °C for more than 144 h, it remained a rejection of higher than 98 % for Rhodamine B (479 Dalton), indicating its superior solvent resistance and promising industrial application prospect.

Polyamide thin-film nanocomposite membrane containing star-shaped ZIF-8 with enhanced water permeance and PPCPs removal

Pharmaceuticals and personal care products (PPCPs) are universally detected in natural waters, posing potential risks to drinking water safety. Nanofiltration (NF) is an advanced technology for water purification; however, its removals of PPCPs are unsatisfying, especially for hydrophobic species. In this study, the 3D architecture of nanomaterials were used to manipulate the performance the polyamide (PA) thin-film nanocomposite (TFN) membrane. In-situ addition of polyethyleneimine (PEI) successfully induced the assembly of ZIF-8 nanocrystals into star-shaped clusters (ZIF-8-PEI) due to the coordination between PEI and Zn2+. Together with the improved hydrophilicity, these ZIF-8-PEI clusters became excellent scaffolds for water drop retention after discretely loading onto the porous substrate. The conical protrusions of the ZIF-8-PEI clusters supported the defect-free PA film produced by the interfacial polymerization (IP), leaving big interfacial cavities underneath. These cavities worked as gutters for water transport, and the water permeance of the optimal TFN was 79% higher than that of the pristine thin-film composite (TFC) membrane. Moreover, the water impregnated cavities markedly alleviated the hydrophobic interaction between the PA film and hydrophobic PPCPs, impeding the transport of PPCPs across the membrane. Our results demonstrated the importance of the 3D architecture of nanofillers for the improving membrane performance.

Polyamide thin film nanocomposite membrane with internal void structure mediated by silica and SDS for highly permeable reverse-osmosis application

The pursuit of highly permeable thin film nanocomposite (TFNC) membrane is an eternal topic for reverse-osmosis (RO) application. Here, we developed a new avenue based on interfacial polymerization to generate a polyamide TFNC membranes EVOH-SiS-PA by adding silica nanorods (SNRs) and sodium dodecyl sulfate (SDS) in water phase on the surface of EVOH nanofibrous scaffold. The resultant membrane presents a foam-like PA layers with a hierarchical internal voids structure, which is 2–3 μm in thick and distinctly differs to the membranes reported to date. The structure feature can be attributed to the fast reaction between MPD and TMC, Marangoni convection in water phase synergistically determined by SDS molecules on water/hexane interface and SNRs with abundant hydroxyl groups. Comparatively, PA TFNC membranes without SDS and/or SNRs just present a PA layer with smaller thickness (1–2 μm), surface roughness and surface area. As a result, a high permeance of 8.5 L m−2 h−1 bar−1 and a reasonably high rejection to NaCl, CuSO4 and MO feed solution (97.1%–2000 ppm NaCl, 98.2% rejection to 2000 ppm CuSO4 and 99.2% to 20 ppm MO) were obtained towards EVOH-SiS-PA, outperforming the currently reported RO membranes. Here, we provide an approach to fabricate advanced PA TFNC membranes with excellent performance, highlighting their great potential in reverse-osmosis application.

Influence of graphene oxide with different sizes or layers on polyamide thin-film nanocomposite membranes

Influence of graphene oxide with different sizes or layers on polyamide thin-film nanocomposite membranes

Effect of Functionalized Nanodiamonds and Surfactants Mediation on the Nanofiltration Performance of Polyamide Thin-Film Nanocomposite Membranes

Effect of Functionalized Nanodiamonds and Surfactants Mediation on the Nanofiltration Performance of Polyamide Thin-Film Nanocomposite Membranes

Antifouling and antibacterial β-cyclodextrin decorated graphene oxide/polyamide thin-film nanocomposite reverse osmosis membranes for desalination applications

• β-cyclodextrin-functionalized graphene oxide enhanced membrane properties. • Membrane with improved surface hydrophilicity and pure water permeability obtained. • Superior antibacterial and antifouling properties imparted on membrane. • Potentially a robust reverse osmosis membrane with an improved life-span. Incorporating functional nanomaterials in polyamide-based membranes has opened up new alternative ways to develop reverse osmosis membranes with excellent performance, biological stability, chemical stability and longer life-span. In this study, β-cyclodextrin functionalized graphene oxide nanosheets (β-CD-f-GO) were synthesized and used to fabricate polyamide thin film nanocomposite membranes possessing excellent reverse osmosis performance, antifouling and antibacterial properties. The β-CD functionalized graphene oxide nanosheets were prepared via an amide-mediated coupling reaction between ethylenediamine-grafted β-CD and graphene oxide. The fabricated nanosheets were then embedded in the polyamide thin film composite membranes via interfacial polymerization of m-phenylenediamine in an aqueous solution containing β-CD-f-GO nanosheets with trimesoyl chloride. The influence of the nanosheets on the membrane surface chemistry, permselectivity performance, antibacterial and antifouling properties was investigated. The results revealed that the water permeation flux and antibacterial activity of the β-CD-f-GO incorporated membranes showed an improvement by approximately 38% and 45.9%, respectively, relative to an unmodified polyamide membrane, with an insignificant change in salt rejection. In addition, the nanocomposite membranes exhibited improved antifouling properties with a lower total fouling ratio of 26.2% and a higher flux recovery ratio of 88.3% in comparison to the respective 46.8% and 74.1% obtained with the unmodified polyamide membrane. Additionally, the nanomposite membranes showed long term stability over a period of 144 h of reverse osmosis testing and improved chlorine resistance. With this study, it can be concluded that the β-cyclodextrin-functionalized graphene oxide nanocomposite has a good potential in the fabrication of membranes with improved stability and lifespan for desalination applications.

Improving permeability and anti-fouling performance in reverse osmosis application of polyamide thin film nanocomposite membrane modified with functionalized carbon nanospheres

• –COOH and Ag-functionalized carbon nanospheres are successfully synthesized. • TFN membranes containing functionalized CNs are prepared for RO application. • Carboxyl groups in nanofillers significantly influence the membrane structure. • TFN-Cs-COOH membrane shows high water flux of 63 LMH and NaCl rejection over 96.8%. • The TFN–Cs–COOH/Ag membrane possesses remarkable anti-bacterial property. In this study, carboxyl group-functionalized carbon nanospheres (CNs–COOH) and silver-coated products (CNs–COOH/Ag) were successfully realized and used as nanofillers to fabricate thin-film nanocomposite (TFN) membranes via the interfacial polymerization of m -phenylenediamine (MPD) and trimesoyl chloride (TMC) solutions. The structure of the functionalized CNs modified TFN membranes (TFN–Cs–COOH, TFN–Cs–COOH/Ag) was significantly different from that of the CNs modified TFN (TFN–Cs) and TFC membranes, as the carboxyl groups in the nanofillers strongly influence the process of interfacial polymerization. The permeability and anti-fouling performances of the TFN membranes were significantly enhanced owing to the changes in the membrane structure. The water fluxes of the TFN–Cs–COOH and TFN–Cs–COOH/Ag membranes were respectively 91.9% and 73.2% higher than that of the TFC membrane, with the NaCl rejection exceeding 96%. The nanofillers of CNs–COOH/Ag with monodispersed silver nanoparticles (NPs) resulted in outstanding anti-bacterial performance in the TFN–Cs–COOH/Ag membrane. Overall, this work demonstrates that, when functionalized carbon NPs are used as nanofillers, the practical performance of TFN membranes can be improved for reverse osmosis.

Layer-by-layer polyamide thin film nanocomposite membrane: synthesis, characterization and using as pervaporation membrane to separate methyl tertiary butyl ether/methanol mixture

In this work, layer by layer (LbL) thin film nanocomposite (TFN) membranes were prepared and used as pervaporation membranes to separate methyl tertiary butyl ether (MTBE)/methanol (MeOH) mixture. TFN membranes, comprising of carbon nanotubes (CNT), were prepared by interfacial polymerization (IP) of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) monomers on the porous polyethersulfone/polyethylene glycol (PES/PEG) sublayer. Carbon nanotubes were functionalized by ethylenediamine (EDA) and incorporated into the polyamide (PA) layer at 0.01–0.04 wt.% loadings. After that, the surface roughness, surface hydrophilicity, and morphology of the resulting membranes were characterized. Also, the effect of the sequence of reactants deposition and concentrations of the nanotubes on the membrane performance were investigated using pervaporation of MTBE/MeOH under feed temperature and feed flow rate of 30 °C and 4 L.h-1, respectively. The pressure of permeate-side was about 100 mbar. Obtained results showed that both separation factor and permeation flux of LbL TFN membranes increased by adding CNT into the PA layer up to 0.02 wt.%. By increasing CNT loading to 0.04 wt.%, the separation factor decreased from 106 to 77.6, while permeation flux increased from 0.56 to 0.81 kg.m-2.h-1. It should be noted that, in the single-layer membrane, the separation factor decreased from 73.2 for TFC membrane to 56.4 for TFN membrane with increasing the CNT loading from the beginning. According to these results, LbL TFC and TFN membranes are expected to be the next generation of high-performance PV membranes.

Environmentally friendly approach for the fabrication of polyamide thin film nanocomposite membrane with enhanced antifouling and antibacterial properties

In this work, we employed an environmentally friendly approach based on plasma enhanced chemical vapour deposition (PECVD) to modify titania nanotubes (TNTs), aiming to obtain better dispersion of nanofillers in polyamide (PA) layer of thin film nanocomposite (TFN) reverse osmosis membrane. Owing to the hydrophilic nature of TNTs, dispersing it homogenously in organic solvent during interfacial polymerization process is difficult to achieve. Therefore, the TNTs are mildly modified by PECVD technique in order to ameliorate its stability in organic solvent. Our results showed that depositing thin layer of methyl methacrylate (MMA) on the TNTs surface could enhance its dispersion quality in organic solvent and further improve the properties of PA layer by enhancing membrane water flux by 16% without compromising NaCl rejection. More importantly, the developed TFN membrane showed excellent fouling resistance by recording flux recovery rate of 85.77% compared to 57.94% shown by the control membrane. Its antibacterial property was also obviously better than that of control membrane. Overall, the developed TFN membrane demonstrated good performance stability with respect to NaCl rejection and water permeability and the trace amount of nanofillers detected in the water sample (in the level ofμg/L) did not negatively influence the membrane filtration performance.

Employing the synergistic effect between aquaporin nanostructures and graphene oxide for enhanced separation performance of thin-film nanocomposite forward osmosis membranes

In this study, novel thin-film nanocomposite (TFN) membranes were developed by incorporating graphene oxide (GO) and Aquaporin Z (AqpZ) reconstituting nanostructure (AQN) into the polyamide (PA) active layer to improve the forward osmosis (FO) performances of the PA TFN membranes. First, the AQN loading in the PA layer was optimized, followed by the GO addition in PA layer at various loadings until the optimal FO process performance was attained. Experimental results showed that GO flakes increased membrane water flux but decreased selectivity by creating non-selective voids in PA layer. Whereas, AQN increased membrane selectivity by healing the non-selective PA defects created by the GO flakes. The synergistic effect of GO-AQN improved the water flux without deteriorating the selectivity of the membrane. The TFN membrane with 0.2 wt% AQN and 0.005 wt% GO loading (TFN50) showed almost 3 folds increase in water flux (24.1 L·m−2·h−1) in comparison to the TFC membrane (8.2 L·m−2·h−1), while retaining the membrane selectivity (0.37 g.L−1). Interestingly, the TFN50 membrane demonstrated a 27% lower specific reverse salt flux (SRSF) and a marginal increase in water flux than the TFN membrane embedded with 0.005 wt% GO and no AQN (TFNGO50). The overall experimental results confirmed that the addition of AQN into GO-based PA TFN membranes could improve the membrane selectivity by reducing the non-selective PA defects created by GO flakes. The results of this study could provide strategies to further enhance the selectivity of GO-based TFN membranes by preventing the formation of defective PA layer.