Thin Film Nanocomposite Nanofiltration Membrane Research Articles

Exploiting sulfonated covalent organic frameworks to fabricate long-lasting stability and chlorine-resistant thin-film nanocomposite nanofiltration membrane

Incorporating hydrophilic and charged porous nanofillers to prepare high-performance thin film nanocomposite (TFN) nanofiltration (NF) membranes is an effective method to achieve efficient water treatment. In this study, we synthesize the sulfonated covalent organic framework nanosheets (S-CONs) with higher hydrophilicity and electronegativity by immobilizing sulfonic acid groups (–SO3H) on TpPa-1 nanosheets. The S-CONs are incorporated in the PA layer by interfacial polymerization (IP) reaction. The results indicated that the S-CONs could modulate the hydrophilicity, thickness, and electronegativity of TFN-NF membranes. At the optimal addition of S-CONs (0.006 g), the pure water permeance increases to 8.84 L⋅m−2⋅h−1⋅bar−1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\rm{L}}\\cdot{\\rm{m}}^{-2}\\cdot{\\rm{h}}^{-1}\\cdot{\\rm{bar}}^{-1}$$\\end{document}, which is about 1.75 times than the TFC membrane, with a high Na2SO4 rejection reaching 98.97%. The improvement of the separation performance mainly results from the reduction of PA layer thickness (from ~178.00–198.00 to ~100.00–128.00 nm) and the increase of surface electronegativity (from −20.37 to −44.41 mV at pH = 7.00). More interestingly, the amide bond formed between the S-CONs and TMC improved the chlorine resistance of the membranes. This study reveals the potential of using functionalized 2D CONs as nanofillers to modify TFC membranes for efficient nanofiltration.

Tannic acid etched ZIF-8 incorporated thin-film nanocomposite nanofiltration membrane with enhanced performance

Incorporating functionalized nanomaterials in the selective layer of conventional polyamide nanofiltration (NF) membrane is a promising strategy for overcoming the trade-off between permeability and selectivity. Highly hydrodispersible TA/ZIF-8 composite nanomaterials were prepared by etching ZIF-8 with tannic acid, and the thin-film nanocomposite (TFN) NF membranes were prepared by introducing TA/ZIF-8 into the interfacial polymerization aqueous phase solution. The nanomaterials and NF membranes' structure, chemical composition, and hydrophilicity were comprehensively characterized. The influence and mechanism of introducing TA/ZIF-8 into the polyamide layer on the separation performance of the TFN membranes were discussed by separating typical mono- and divalent salts. The optimal TFN membrane had a water flux of 26.59 LMH-bar−1 (increased by 86.6% than that of the TFC-blank membrane) with 94.95% rejection of Na2SO4 while having good antifouling performance and stability. Furthermore, the inverse size exclusion phenomenon of chlorine-contained salts was explored through relevant control experiments. This work is valuable for expanding the application of 3D nanomaterials in membrane separation technology and preparing high-performance TFN nanofiltration membranes.

Application of a functionalized thin-film composite nanofiltration membrane in water desalination

To prepare a thin-film nanocomposite (TFN) nanofiltration (NF) membrane, characterized with high desalination rate and antifouling performance, carboxylated multi-walled magnetic 1,2,3,4-butanetetracarboxylic acid carbon nanotubes (hereafter, the C-MWCNT-MBTCA) with a choice of hydrophilic groups were initially synthesized in this study, and then incorporated into the polyamide (PA) layer via interfacial polymerization (IP). After that, the surface morphology and hydrophilicity of the fabricated NF membrane was examined by the field emission scanning electron microscopy (FESEM) and water contact angle measurements, respectively. To assess the membrane application, the solutions (2000 mg/L) of sodium sulfate (Na2SO4), magnesium sulfate (MgSO4), calcium chloride (CaCl2), and sodium chloride (NaCl) were consistently tested. On account of the ample carboxylic acid (R-COOH) groups in the modified TFN membrane, the study outcomes revealed that the given membrane could enhance the flux along with the desalination rate upon the addition of the C-MWCNT-MBTCA (0.04 wt%). Likewise, the pure water flux significantly grew from 58.8 to 110.5 Lm-2h−1 after the utilization of the C-MWCNT-MBTCA (0.04 wt%), and the Na2SO4 removal rate promoted from 87 to 98 %. Ultimately, it was established that the C-MWCNT-MBTCA could be used as an economical modifying agent to boost the performance of NF membranes for water desalination purposes.

Water recovery from the high salinity brine: Effect of the interlayer structure in the polyamide nanofiltration membrane

Water recovery by nanofiltration (NF) from the high salinity brine is emerging as a promising technology to alleviate the water shortage. Thin film composite membranes with polyamide (PA) selective layer are the mainstream in the field of NF. Nevertheless, the trade-off between permeance and retention as well as the structural stability of the mainstream PA membrane still restrict their widespread application. Herein, a novel interlayered thin-film nanocomposite (TFNi) nanofiltration membrane was fabricated based on the interfacial polymerization. The PDA@MXene hybrid was employed as the interlayer to modulate the adsorption and diffusion process of amine monomers, giving rise to the formation of thin and rough PA selective layer, which could accelerate the transport of water molecules. Moreover, PM-TFNi membrane demonstrated higher crosslinking degree and more negatively charged surface, significantly benefiting the repulsion of inorganic salt ions. In this context, PM-TFNi membrane rendered a competitive permselectivity with the water flux of 18.3 L m−2 h−1 bar−1 and the Na2SO4 rejection of 98.0%. In addition, PM-TFNi membrane exhibited distinguished long-term stability and pH resistance. Overall, this work would provide a paradigm shift in designing high-performance and robust NF membrane for the water treatment.

Graphene oxide incorporated thin film nanocomposite nanofiltration membrane to enhance permeation and antifouling properties

Aiming at the problems of low permeation flux and low salt rejection of polyamide (PA) nanofiltration (NF) membrane, this study improved the surface properties and structure of PA layer by adding hydrophilic GO nanosheets. Polyethylimide (PEI), GO and trimethylchloride (TMC) were prepared on the surface of polyether sulfone (PES) substrate by interfacial polymerization. After adding GO, the hydrophilicity and zeta potential of NF membrane were improved. The NF test showed that when the amount of GO was 0.1%, the permeation flux of the membrane was increased from 7.06 to 12.285 L·m−2·h−1 (improve 73.94%), and the rejection of MgSO4 was increased from 90.23% to 95.9%. In the test of repulsion of univalent ion and bivalent ion, the repulsion value of bivalent ion is above 95%, and the repulsion degree of univalent ion is moderate. Compared with the original TFC membrane, the composite membrane also showed higher anti-fouling. This study provides a shortcut for improving the hydrophilicity and anti-fouling properties of NF membranes by using GO nanosheets.

Incorporating etched ZnO nanoparticles to fabricate positively charged composite membrane for heavy metal removal

The removal of heavy metal ions by nanofiltration (NF) membranes is attractive, but it is limited by a trade-off effect between permeation and solute rejection. Generally, the permeability of the NF membrane is closely related to its hydrophilicity, while the solute rejection is closely related to size exclusion and the Donnan effect. In this study, porous etched zinc oxide (ZnO) nanoparticles were prepared through alkali etching, and a thin-film nanocomposite (TFN) NF membrane was fabricated by interfacial polymerization (IP) method between PEI and TMC on a polysulfone (PSF) substrate. The incorporation of 0.01 wt% etched ZnO nanoparticles increased the hydrophilicity and positive charge of the NF membrane, resulting in an increase in the permeability (from 6.0 L m−2 h−1 bar−1 to 8.1 L m−2 h−1 bar−1) and rejection of heavy metal ions (Cu2+, Zn2+, and Ni2+ increased from 85 % to over 96 %). Long-term filtration experiments using the simulated wastewater demonstrated that the prepared NF membrane exhibited good stability and had the potential for industrial applications. It opens a new pathway for studying TFN NF membranes, indicating that alkaline etching can transform smooth nanoparticles into nanoparticles with higher specific surface area and porosity, thereby improving the performance of membranes.

Thin film nanocomposite nanofiltration with tannic acid-Fe(III) complexes functionalized Ti3C2Tx for enhanced divalent-salinity-water separation with a superior durability

Incorporating nanomaterials for a thin film nanocomposite (TFN) layer has been verified effective to improve the separation performance of nanofiltration (NF) membranes, whereas the poor compatibility between nanomaterials and polyamide (PA) matrix leads to a decrease in the salt rejection and pollution resistance. In this study, inspired by a new interface-bridging idea, Ti3C2Tx was bonded with tannic acid-Fe(III) (TA-Fe(III)) complexes, and then incorporated into a PA matrix for the first time to obtain a novel TFN NF membrane. The introduction of TA-Ti3C2Tx was found to effectively reduce the diffusion of piperazine, and thus result in the induction of a thinner, lower roughness, more hydrophilic, and defect-free PA layer. With the addition of 0.015 wt% TA-Ti3C2Tx, the TFN membrane obtained the highest water permeability of 12.17 L m−2 h−1 bar−1, almost twice that of the pristine membrane, with a high Na2SO4 rejection above 97 %. In addition, the TA-Ti3C2Tx-filled TFN membranes were verified to exhibit excellent antifouling performance and pressure resistance with a high durability, which is crucial for the practical application in salinity water treatment. This study provides an effective strategy to tailor the interfacial microstructural of nanoparticle-filled NF membranes for superior divalent-salinity-water separation.

Deep learning models for assisted decision-making in performance optimization of thin film nanocomposite membranes

The performance of thin film nanocomposite nanofiltration membranes (TFNNMs) is frequently constrained by the trade-off between the permeability and rejection/selectivity of the membrane. In this study, to provide assisted decision-making in performance optimization of TFNNMs, we utilized a dataset comprising four categories of impact parameters, including membrane manufacturing conditions, membrane performance, nanoparticle material performance, and organic solvent nanofiltration conditions, and trained a dual output neural network (D-ANN) to simulate the relative permeability (RP) and relative rejection/selectivity (RR) of TFNNMs. The D-ANN model outperformed conventional machine learning models and single-output neural networks in predicting both RP and RR, indicating its potential in uncovering correlations between output variables. The Shapley additive explanation method was employed to elucidate the contribution and marginal effects of each influencing parameter on RP and RR, among them, NP size, NP loading, water contact angle, and chloride concentration were influential parameters that are important for both RP and RR. Based on the D-ANN model, we extrapolated two sets of unknown data and achieved good predictive performance (RP-error <15%, RS-error <7% for most sample points). Furthermore, we observed that the predicted performance of the data points rarely exceeded the actual performance, indicating a low probability of overestimation. Based on these premises, the influential parameters can be optimized using the D-ANN model, which ultimately led to exceptional performance for a total of 22 datasets in four pairs of organic solvent and solute purifications guided by the D-ANN model. This study demonstrates that the D-ANN model can provide decisions for the performance optimization of TFNNMs while highlighting the enhancement of nanofiltration performance by thin film nanocomposites, significantly facilitating the design of high-performance TFNNMs.

Incorporating of β-cyclodextrin based nanosheet for advanced thin-film nanocomposite nanofiltration membrane with improved separation and anti-fouling performances

Nanotechnology has created numerous opportunities for the development of novel thin film nanocomposite (TFN) membranes. In this study, we prepared a novel β-cyclodextrin based nanosheets (β-CDNSs) with a lateral size of approximately 200–400 nm and thickness of ∼10 nm through the interfacial polymerization method and used it as the nanofillers in aqueous phase to prepare advanced nanofiltration (NF) membranes. The high microporosity, organic attribute, hydrophilic COOH and reactive OH groups present in β-CDNSs are conducive to the microstructural parameters fine-tuning of the resultant TFN membranes. The optimal membrane TFN-0.02 presented the PA selective layer with thinner thickness, less crosslinking degrees, prominent globule microstructures, and increased hydrophilic properties. As a result, it achieved a remarkable enhancement in pure water permeability (21.46 L m−2 h−1 bar− 1, versus 8.79 L m− 2 h− 1 bar− 1, nearly 2.4-fold increase), high rejection of divalent salt (above 98% for Na2SO4) and an outstanding selectivity of αNaCl/Na2SO4 = 50.27. Moreover, the tailored membrane TFN-0.02 exhibited superior resistance towards four typical organic foulants BSA, LYZ, DTAB and SDS. Overall, this work provides insightful guidance for the design of novel organic nanomaterials with desired properties for greatly enhanced separation performances of as-fabricated membranes.

Development of micropollutants removal process using thin-film nanocomposite membranes prepared by green new vapour-phase interfacial polymerization method

The presence of emerging micropollutants in water bodies and potable water, has become a topic of great concern globally. In this study, a newly modified vapour-phase interfacial polymerization (VP-IP) method has been used to fabricate thin-film composite (TFC) and thin-film nanocomposite (TFN) nanofiltration (NF) membranes to study the removal of micropollutants, diclofenac (DIC) and triclosan (TRI) from water. The method used is an economically and environmentally greener method as the reaction takes place between the aqueous monomer solution and vapours of the organic phase, thereby avoiding the utilization of organic solvent hence named as vapour-phase interfacial polymerization (VP-IP) method. Polydopamine (PDA) coated polyethersulfone (PES) membranes were used to support the TFC and TFN membranes. The TFN membranes were incorporated with different concentrations of amine-functionalized cloisite Na+ 2D clay nanosheets (NH2-CMMT) to enhance the physicochemical properties of the TFN membranes. The performance study of the prepared TFN membranes based on different hours and pressures demonstrated an excellent rejection percentage of ∼99 ± 0.5% for both DIC and TRI compared to the TFC membrane. The membranes showed improved water permeate fluxes of ∼109 ± 5 Lm-2h-1 for DIC and ∼150 ± 5 Lm-2h−1 for TRI. The prepared TFN membranes demonstrated positive results for the antifouling test as well as exhibited antibacterial activity tested against Escherichia coli (E. coli) bacteria. The findings of this study show that our prepared TFN membranes combined with NH2-CMMT 2D clay nanosheets exhibit enhanced hydrophilicity, improved flux rate, excellent removal efficiency, antibacterial activity, and improved antifouling properties, indicating the potential to be used for removing emerging micropollutants from water.

Incorporating imine-based covalent organic frameworks nanosheet as an active filler for long-term nanofiltration desalination

Covalent organic frameworks nanosheets (CONs) are two-dimensional porous nanomaterials exfoliated from covalent organic frameworks (COFs). The ordered permanent microchannels and excellent water stability of CONs make them attractive active fillers for the preparation of thin-film nanocomposite (TFN) nanofiltration (NF) membranes. Herein, we report the fabrication of TFN membranes by incorporating covalent organic framework nanosheets TpPa-1 CONs as an active filler in the organic phase during the interfacial polymerization (IP) reaction. The addition of TpPa-1 CONs promotes the formation of extra water channels (pores and interfacial cavities) in the PA layer, rendering the TFN membranes with a higher pure water permeance of 8.54 L m−2 h−1 bar−1, which is about 1.4 times compared to TFC membrane, and excellent Na2SO4 rejection of about 98.1%. Owing to the hydrophilic nature of TpPa-1 CONs, the synthesized TFN membranes also exhibited higher hydrophilicity and superior anti-fouling performance. Meanwhile, the 35-days stability experiment verified that the TpPa-1 CONs TFN membrane has superior long-term stability. As a 2D porous nanosheets, TpPa-1 CONs provided some guidance for the preparation of long-term stability NF membranes with excellent separation performance.

Conductive thin-film nanocomposite nanofiltration membrane comprising N-doped graphene quantum dots with relieved concentration polarization for sulfate separation from high-salinity solution

Conductive thin-film nanocomposite nanofiltration membrane comprising N-doped graphene quantum dots with relieved concentration polarization for sulfate separation from high-salinity solution

Two dimensional sulfonated molybdenum disulfide (S–MoS2) thin-film nanocomposite nanofiltration membrane for selective desalination

Nano-fillers will be an attractive strategy to improve salt fractionation of nanofiltration (NF) membrane if the integrity problem of nano-fillers in PA layer is well addressed. In this work, molybdenum disulfide (MoS2) nanosheets sulfonated with 1,3-propane sultone was added to the aqueous phase to participate in the interfacial polymerization reaction and construct a novel thin-film nanocomposite (TFN) nanofiltration membrane. A series of characterization and discussion were carried out on the obtained nanomaterials and membranes. The S–MoS2 nanosheet can be well wrapped by the resulted PA layer, thereby preserving the integrity of the PA skin. Furthermore, The TFN membranes possessed enhanced electronegativity and hydrophilicity and the PA layer became thinner and denser after introducing the sulfonated MoS2 nanosheets (S–MoS2) in the PA matrix. In particular, the optimal S–MoS2 composite membrane exhibits excellent performance, which approximately reach 99% divalent salt (Na2SO4) rejection and 1.4-fold water permeance of the pristine membrane. Overall, this study provided a novel way for separation treatment of hypersaline wastewater.

Polyvinyl alcohol/attapulgite interlayer modulated interfacial polymerization on a highly porous PAN support for efficient desalination

Interlayered thin film nanocomposite nanofiltration (TFNi-NF) membranes have the potential to overcome the permeability and selectivity limitations of conventional NF membranes. This work is the first attempt to construct the polyvinyl alcohol/attapulgite (PVA/ATP) nanocomposite interlayer by chemical cross-linking between PVA and glutaraldehyde (GA) in which the nanomaterial ATP was connected with covalent bonds. Meanwhile, the support layer of the NF membranes was chosen to be a microporous membrane with high porosity and a three-dimensional (3D) network porous structure prepared by the innovative atomization-assisted non-solvent induced phase separation (AA-NIPS) method, greatly enhancing the water transport channels. The ATP acted as a multifunctional regulator to tune the porous structure of the PVA/ATP nanocomposite interlayer through physicochemical interactions. By manipulating monomer diffusion behavior, a dense polyamide (PA) layer with only 12 nm in thickness was prepared, leading to enhanced permeability and rejection for divalent ions. In addition, the structure and performance of the TFNi-NF membranes are highly tunable by changing the ATP loading. The prepared TFNi-NF membranes have shown great potential for seawater desalination and the separation and purification of aqueous electrolytes.

Photo-Fenton reaction derived self-cleaning nanofiltration membrane with MOFs coordinated biopolymers for efficient dye/salt separation

Membrane technology has been widely used in textile industry for the separation of dye/salt mixtures. However, membranes inevitably suffered from the fouling issue, which greatly abated the water permeability and reduced the separation efficiency of membranes. Herein, a novel thin film nanocomposite (TFN) nanofiltration (NF) membrane was prepared by introducing photocatalytic sensitive material into the selective layer to directly degrade the foulants on the membrane surface. This functional selective layer was achieved by a complexation of carboxymethyl cellulose (CMC) and MIL-53 (Fe), which greatly enhanced the self-cleaning ability of the TFN membrane while MIL-53 (Fe) was served as nanofiller and photocatalyst simultaneously. The optimized TFN NF membrane modified with 0.5 mg CMC and 0.075 mg MIL-53 (Fe) exhibited a high pure water permeability of 39.83 L m−2 h−1 bar−1, while maintaining high dye rejections above 99.00 % for CR, G250 and MB. Meanwhile, the obtained membrane exhibited impressive rejections of salts (61.49 % for Na2SO4 and 17.22 % for NaCl). This simple fabrication strategy provided new insights to augment the separation performance of TFN NF membrane with self-cleaning ability in organic separation systems.

Incorporation of Functionalized Halloysite Nanotubes (HNTs) into Thin-Film Nanocomposite (TFN) Nanofiltration Membranes for Water Softening

Incorporating nanoparticles (NPs) into the selective layer of thin-film composite (TFC) membranes is a common approach to improve the performance of the resulting thin-film nanocomposite (TFN) membranes. The main challenge in this approach is the leaching out of NPs during membrane operation. Halloysite nanotubes (HNTs) modified with the first generation of poly(amidoamine) (PAMAM) dendrimers (G1) have shown excellent stability in the PA layer of TFN reverse-osmosis (RO) membranes. This study explores, for the first time, using these NPs to improve the properties of TFN nanofiltration (NF) membranes. Membrane performance was evaluated in a cross-flow nanofiltration (NF) system using 3000 ppm aqueous solutions of MgCl2, Na2SO4 and NaCl, respectively, as feed at 10 bar and ambient temperature. All membranes showed high rejection of Na2SO4 (around 97-98%) and low NaCl rejection, with the corresponding water fluxes greater than 100 L m-2 h-1. The rejection of MgCl2 (ranging from 82 to 90%) was less than that for Na2SO4. However, our values are much greater than those reported in the literature for other TFN membranes. The remarkable rejection of MgCl2 is attributed to positively charged HNT-G1 nanoparticles incorporated in the selective polyamide (PA) layer of the TFN membranes.

Positively-charged PEI/TMC nanofiltration membrane prepared by adding a diamino-silane coupling agent for Li+/Mg2+ separation

Positively charged nanofiltration membrane has gained significant interest in magnesium and lithium separation due to its separation mechanism, especially in salt lake-based lithium industry. To obtain a high-density positive charged surface and high Li+/Mg2+ selectivity, a novel thin-film nanocomposite (TFN) nanofiltration (NF) membrane for recovery of Li+ from Mg/Li mixtures with Mg2+/Li+ ratios of 20 was successfully prepared by using polymeric amine polyethyleneimine (PEI) and monomeric amine silane coupling agent (3-diamino-methyl-cyclohexyl triethoxysilane, DTES). Then the effect of DTES on the surface properties and performance of the prepared DTES/PEI/TMC TFN membranes were investigated. Chemical composition analysis revealed that DTES not only hydrolyzed to Si–OH and then self-polymerized to Si–O–Si, but also reacted with the self-carrying acyl chloride of 1,3,5-benzene trichloromethane (TMC). Moreover, SiO2 nanoparticles were in-situ generated from DTES inside the PA layer with high compatibility. Due to the compatible properties with the positively charged PEI polymer, the reacted DTES was distributed uniformly in the formed TFN selective layer with no noticeable aggregation. The doping of SiO2 into the polyamide network gave rise to the enlargement of the membrane pore size, enhanced the surface hydrophilicity, and reinforced the surface positive charges. The water flux of the DTES/PEI/TMC membrane improved from 36.9 L m−2 h−1 to 49.58 L m−2 h−1 compared to the PEI/TMC membrane. Additionally, the Mg2+ and Li + rejection of the optimized membranes was 91.46% and −10.5%, respectively, with permeability and selectivity (SLi, Mg = 12.95) superior to that of the commercial NF membranes. Considering the commercial availability of DTES, this study not only offers a high-performance nanofiltration membrane for recovering lithium from brines but also provides a feasible strategy for industrial separation of other monovalent and divalent ions.

A Novel Approach for the Development of Low-Cost Polymeric Thin-Film Nanocomposite Membranes for the Biomacromolecule Separation.

The separation of biomacromolecules, mainly proteins, plays a significant role in the pharmaceutical and food industries. Among the membranes' techniques, thin-film nanocomposite nanofiltration membranes are the best choice due to their high energy efficiency, excellent productivity, cost-effective and tuneable properties that have captured the attention of the efficient separation of biomacromolecules, especially from the industrial perspective. The present work directs the efficient separation study of proteins, namely, lysozyme, trypsin, pepsin, bovine serum albumin (BSA), and cephalexin, using a thin-film nanocomposite membrane integrated with Arg-MMT (arginine-montmorillonite) clay nanoparticles. The surface morphology and cross-section images of the TFN membranes were studied using a field emission scanning electron microscope (FE-SEM) and a high-resolution transmission electron microscope (HR-TEM). The thermal stability and hydrophilicity of the membranes were examined using thermogravimetric analysis (TGA) and contact angle, respectively. The surface chemistry of the selective layer has different functional groups that were analyzed using FTIR spectroscopy. The performance of the membranes was studied at different trans-membrane pressures and permeation times. The effect of monomer concentration on the separation performance of the membranes was also studied at different permeation times. The membranes' antibacterial activity was evaluated using the Muller-Hinton disk diffusion method using gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus) bacteria. The highest rejection was achieved for BSA up to 98.92 ± 1%, and the highest permeation was obtained against lysozyme feed solution up to 26 L m-2 h-1 at 5 bar pressure. The membrane also illustrated excellent rejection of cephalexin antibiotics with a rejection of 98.17 ± 1.75% and a permeation flux of 26.14 L m-2 h-1. The antifouling study performed for the membranes exhibited a flux recovery ratio of 86.48%. The fabricated thin-film nanocomposite membrane demonstrated a good alternative for the separation of biomacromolecules and has the potential to be used in different sectors of industry, especially the pharmaceutical and food industry.

Nano-striped polyamide membranes enabled by vacuum-assisted incorporation of hierarchical flower-like MoS2 for enhanced nanofiltration performance

Introducing nanomaterials into the polyamide layer of thin-film composite (TFC) membranes during interfacial polymerization process can customize the physicochemical properties of membranes and further enhance the membrane permeability without sacrificing selectivity. In this study, we prepared novel thin-film nanocomposite (TFN) nanofiltration membranes by varying the deposition density of hierarchical flower-like structured molybdenum disulfide (HF–MoS2) with the assistance of vacuum filtration. Ascribed to the unique 3D hierarchical structure of HF–MoS2, a nano-sized striped polyamide film with a decreased thickness of 30–40 nm was formed, which increased the membrane effective filtration area and reduced the mass transfer resistance for water permeation. In addition, compared to the control TFC membrane, the TFN membranes possessed relatively looser polyamide layers with higher surface hydrophilicity and more negative surface charges. When the deposition density of HF–MoS2 was 10 μg/cm2, the optimal performance of the TFN membranes was obtained, i.e., a water permeability of 18.4 L m−2 h−1 bar−1 and rejections above 98% for Na2SO4 and MgSO4. Moreover, the optimal TFN membrane demonstrated an excellent separation performance and structure stability in the mixed salt solution and the long-term filtration test of 120 h, respectively. This work provides a novel approach to design high-performance TFN membranes applied for water/wastewater treatment.

Ionic liquid modified COF nanosheet interlayered polyamide membranes for elevated nanofiltration performance

Presently, advanced Thin-film nanocomposite (TFN) nanofiltration membranes fabricated using microporous materials displayed distinctly enhanced separation performance. Herein, tetrakis(hydroxymethyl) phosphonium chloride (THPC)-modified COF nanosheets (termed as IL@COF-367 NSs) were designed as the intermediate layer to construct a high-hydrophilic membrane support, with the purpose of regulating interfacial polymerization (IP) to optimize the physicochemical characters of polyamide films. Due to the high hydrophilicity and favored dispersion of IL@COF-367 NSs in aqueous phase, the as-fabricated COF nanosheet interlayer not only promotes uniform distribution of amine monomers, but also slows down their diffusion toward the organic interface. Compared pristine thin-film composite (TFC) membranes, the IC-TFN membranes yield a nodular polyamide film with a higher surface roughness (from 14.5 to 54.5 nm) and a lower film thickness (from 95 to 30 nm). Introducing IL@COF-367 NSs additionally improves the pore size (from 0.31 to 0.47 nm) of the functionalized TFN membrane revealed by the MWCO measurement. Consequently, IL@COF-367 NSs-interlayer polyamide (IC-TFN) membrane manifests a high permeability of 36.5 L m−2 h−1 bar−1 and satisfactory Na2SO4 rejection of 98.5 %. The usage of 2D hydrophilic COF nanosheet as an interlayer to optimize the polyamide membranes offers a guideline for the design of high-performance TFN membrane.