Thin Film Nanocomposite Membranes Research Articles

Polydopamine-modified HKUST-1 as nanofiller of PPS@PA membrane with well improved desalination performance

In order to improve the permeability and desalination performance of the thin-film nanocomposite (TFN) membranes supported by polyphenylene sulfide ( PPS ), the polydopamine (PDA) modified HKUST-1 (mHKUST-1) nanocomposite materials were added into polyamide ( PA ) functional layer. The mHKUST-1 nanoparticles with good dispersity and chemical compatibility were successfully embedded in PA layer to develop a new negative charged nanofiltration membrane. The optimized PPS/12-mHKUST-1@PA membrane showed an excellent permeability of up to 27.35 L∙m −2 h −1 ∙bar −1 , twice as much as the PPS@PA membranes. Meanwhile, the considerable rejection performance of 91.67% to MgSO 4 and 90.06% to Na 2 SO 4 at 4 bar was mainly up to the repulsive effect of negative charge on membrane surface. Moreover, the PPS/mHKUST-1@PA membranes also has stable filtration performance under long time operation. The results suggested that the membrane modification method in this work have great potential for applications in desalination. • The perfect separation layer by mHKUST-1 nanoparticles combined well with PA layer. • Improving the permeability and desalination performances of TFN membranes significantly. • Negatively charged of TFN membranes surface for the separation of sulfate and hydrochloride.

Development of polymer-based new high performance thin-film nanocomposite nanofiltration membranes by vapor phase interfacial polymerization for the removal of heavy metal ions

The vapor phase interfacial polymerization is the new method for the development of thin-film nanocomposite (TFN) and thin-film composite (TFC) membranes. Generally, interfacial polymerization (IP) is done between aqueous phase monomers and organic phase monomers (containing organic solvent like n-hexane) but in this work, IP was done between aqueous phase monomer with vapour phase of organic monomer (TMC) which is the greener method. First time TFN membranes were prepared by vapour phase interfacial polymerization method. TiO2 nanoparticles act as very good nanofillers to prepare the polymeric nanocomposite membranes to tackle the problem of heavy metal pollution in water. However, their weak interaction with the matrix phase is an issue that causes them to leach out during the filtration process of pressure-driven nanofiltration membrane. Functionalizing the TiO2 nanoparticles with polar functional groups is a solution to this issue. After synthesizing carboxylic acid-functionalized TiO2 (COOH-TiO2) nanoparticles were incorporated in the TFN membranes while IP using DETA and TMC containing amine and acyl group monomers, respectively to modify the membrane surface. The effect of different loading concentrations of COOH-TiO2 nanoparticles in TFN has been studied and compared with the TFC membrane. The prepared membranes are subjected to a cross-filtration system for removing Na+, Cu+2, Hg+2, and Pb+2 from their respective Na2SO4, CuSO4, HgCl2, and Pb(NO3)2 feed solutions. The results of TFN membranes were compared with the TFC membrane. The outcomes have shown 87.03 ± 2% rejection of Na+, 86.89 ± 2% rejection of Cu+2, 77.01 ± 2% rejection of Hg+2 and 83.42 ± 1.5% rejection of Pb+2 ions by using TFN membranes. The effect of the monomeric concentration on the performance of the developed membranes was also studied. The antifouling tendency of the membranes was analysed as well by measuring different antifouling parameters like total fouling (FT), flux recovery ratio (FRR), reversible fouling (FR) and irreversible fouling (FIR). The results obtained are outstanding; incorporating nanomaterial results in lowering the irreversible fouling and enhancing the antifouling tendency.

Hydrophilic montmorillonite in tailoring the structure and selectivity of polyamide membrane

2D nanomaterials have been extensively studied for their superiority in desalination applications. For instance, the incorporation of Graphene-Family nanomaterials has been reported to enhance membrane separation performance significantly, yet the other important low-cost 2D nanomaterial, montmorillonite (MMT), is less studied. For the first time, we systematically studied the formation and performance of polyamide membranes with the modification of exfoliated MMT. The exfoliated MMT has overcome the classical membrane permeability-selectivity trade-off attributed to its uniformity, excellent dispersion and compatibility with monomer m-phenylenediamine (MPD). The effects of MMT charges on the perm-selectivity of resultant TFN membranes were also studied symmetrically. MMT can tailor the surface morphology, roughness, hydrophilicity, and crosslink density of polyamide due to tunable charges and ionic strength. In addition, it was found that MMT exhibited a positive effect on the chlorine resistance of the membrane. Taken together, our work provides fundamental insights into the formation and transport mechanisms in thin-film nanocomposite (TFN) membranes.

Incorporating Ag@RF core-shell nanomaterials into the thin film nanocomposite membrane to improve permeability and long-term antibacterial properties for nanofiltration

Ag@resorcinol-formaldehyde resin (Ag@RF) core-shell nanomaterials were prepared by Stöber method, and introduced into polyamide (PA) selective layer of thin-film nanocomposite (TFN) membranes through the interfacial polymerization (IP) process. Due to the abundant hydroxyl groups on the surface and suitable particle size, Ag@RF nanoparticles (Ag@RFs) could be uniformly dispersed in the piperazine aqueous solution and participate in the IP process to precisely regulate the microstructure of the PA selective layer. The resulting “crater structure” and irregular granular structure enlarged the permeable area and contributed to the surface hydrophilicity. For the nanofiltration application, the water flux of TFN membrane modified by Ag@RFs to Na2SO4 solution reached 150 L·m−2·h−1 which was 87.5% greater than TFC, and salt rejection was maintained. The antibacterial efficiency of the prepared TFN membrane on E. coli reached 99.6% in the antibacterial experiment. In addition, due to the special structure of Ag@RFs, the TFN membrane also showed an expected slow-release capability of Ag+, allowing for long-term anti-biofouling properties. This work demonstrates that Ag@RF core-shell nanoparticles with high compatibility of organic nanoparticles and antibacterial properties of Ag nanoparticles could be used as promising nanofillers for designing functional nanofiltration TFN membranes.

Polyoxometalate-modified halloysite nanotubes-based thin-film nanocomposite membrane for efficient organic solvent nanofiltration

Polyoxometalate-modified halloysite nanotubes (POM@MHNTs) were synthesized and doped into the polyamide (PA) matrix by interfacial polymerization to prepare doped POM@MHNTs thin-film nanocomposite (TFN) membranes for organic solvent nanofiltration (OSN). Likewise, thin-film composite (TFC) and TFN membranes doped with HNTs were fabricated. It is worth noting that the methanol flux of the TFN can be efficiently enhanced by tuning the contents of POM@MHNTs. The as-synthesized optimal sample (TFN-0.10) exhibits superior methanol flux of TFN-0.10 membrane of 14.80 L m−2 h−1 bar−1 (1.76 times of that of undoped TFC membrane and 1.12 times of that of doped HNTs membrane (TFN-HNTs-0.10). These are mainly due to the tubular structure of POM@MHNTs providing additional solvent transfer channels and the ridge-valley morphology of the membrane surface increasing the contact area between the membrane and the solvent. Meanwhile, the POM@MHNTs nanohybrids are similarly electrostatically attracted by the amide groups on the polyamide chains produced by interfacial polymerization, improving the compatibility of POM@MHNTs with polyamide membranes. TFN-0.10 OSN membrane showed stable chemical properties in medium polar organic (methanol, ethanol, THF), acid polar organic (acetonitrile), and strong polar organic (DMF) solvents. Prepared TFN OSN membranes exhibited strong long-term operation capability and organic solvent resistance after 80 °C DMF immersion for 7 days with inconspicuous separation performance changes. This work offers the prospect of using organic-inorganic hybrid modified nanomaterials to improve OSN performance.

Facile membrane preparation from colloidally stable metal-organic framework-polymer nanoparticles

UiO-MOFs are based on zirconium cluster and carboxylic acid linkers. They have excellent chemical and thermal stability, tolerance to linkers of different length and functionalities, making them good candidates for a broad range of applications. However, difficulties of processing the polycrystalline powder of MOFs limit their application. Here, we report for the first time the synthesis of the UiO-66 in the presence of a well-defined poly (methacrylic acid)-b-poly (methyl methacrylate) (PMAA-b-PMMA) nanoparticles (NPs) prepared via Reversible Addition−Fragmentation Chain-transfer Polymerization controlled Polymerization Induced Self-Assembly (RAFT-PISA). The PMAA-b-PMMA NPs with multi carboxylic acid groups on their surface, well defined in shape and size, act as multivalent connecting agent for the synthesis of the UiO-66. The resulting colloidally stable UiO-polymer NPs are crystalline, porous, and with an improved processability as was demonstrated by the preparation of a thin film nanocomposite (TFN) membrane. This membrane was applied in the filtration of Nickel (II) phthalocyanine-tetrasulfonic acid tetrasodium salt aqueous solution obtaining a water permeability circa 20 L m−2 h−1 bar−1 with a rejection of more than 90%. This unprecedented facile synthesis approach could be universally applied to other MOFs, expanding their application in different fields due to their enhanced processability.

Functionalized-MXene Thin-Film Nanocomposite Hollow Fiber Membranes for Enhanced PFAS Removal from Water.

Due to adverse health effects and the broad sources of per- and polyfluoroakyl substances (PFAS), PFAS removal is a critical research area in water purification. We demonstrate the functionalization of thin-film composite (TFC) hollow fiber nanofiltration (HFN) membranes by MXene nanosheets during the interfacial polymerization (IP) process for enhanced removal of perfluorooctane sulfonic acid (PFOS) from water. A MXene-polyamide (PA) selective layer was fabricated on top of a polysulfone (PSF) hollow fiber support via IP of trimesoyl chloride (TMC) and a mixture of piperazine (PIP) and MXene nanosheets to form MXene-PA thin-film nanocomposite (TFN) membranes. Incorporating MXene nanosheets during the IP process tuned the morphology and negative surface charge of the selective layer, resulting in enhanced PFOS rejection from 72% (bare TFC) to more than 96% (0.025 wt % MXene TFN), while the water permeability was also increased from 13.19 (bare TFC) to 29.26 LMH/bar (0.025 wt % MXene TFN). Our results demonstrate that both electrostatic interaction and size exclusion are the main factors governing the PFOS rejection, and both are determined by PA selective layer structural and chemical properties. The lamella structure and interlayer of MXene nanosheets inside the PA layer provided different transport mechanisms for water, ions, and PFAS molecules, resulting in enhanced water permeability and PFAS rejection due to traveling through the membrane by both diffusions through the PA layer and the MXene intralayer channels. MXene nanosheets showed very promising capability as a 2D additive for tuning the structural and chemical properties of the PA layer at the permeability-rejection tradeoff.

Novel thin-film nanocomposite membranes with crosslinked polyvinyl alcohol interlayer for Perfluorinated Compounds (PFCs) removal

Conventional polyamide-based interface polymerized nanofiltration (NF) membranes exhibit trade-off characteristics between water permeability and salt selectivity. The introduction of nanomaterial interlayers into thin-film composite (TFC) membranes is expected to overcome the limitation. Herein, a novel membrane was constructed via coating a polyvinyl alcohol (PVA) interlayer on the PES supporting film. Trace amounts of MXene nanosheets were used to form a barrier to avoid the occupancy of large pores by PVA. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectra, water contact angle (WCA), zeta potential, and other characterizations were used to evaluate the chemical and physical properties of the prepared membranes. Due to the PVA hydrophilicity, the composite membranes achieved higher hydrophilicity. Besides, the electronegativity enhancement and roughness improvement facilitate the film to have better application prospects. At the lab scale, the optimized membranes achieved a high-water flux of 22.8 L m⁻2h⁻1bar⁻1 and a 94.5% MgSO4 rejection. The typical kinds of PFCs, including PFOA, PFOS, PFHxA and PFBA, were quantitatively evaluated and analyzed by electrostatic interaction. The excellent performance was maintained in the case of environmental changes owing to the stableness of the PVA interlayer. This study provides a new avenue for fabricating robust NF membranes for actual production.

High‐Performance PA Nanofiltration Membrane with Coral‐Reef‐Like Morphology atop Polydopamine Decorated EVOH Nanofiber Scaffold

AbstractThe pursuit of highly permeable thin‐film nanocomposite (TFNC) nanofiltration (NF) membranes with desirable selectivity is an eternal topic for desalination and wastewater treatment. Herein, a facile route to engineer polyamide (PA) NF membranes is reported with a coral‐reef‐like thin PA active layer atop a polydopamine pre‐decorated ethylene vinyl alcohol copolymer (EVOH) nanofiber scaffold (EVOH‐PDA) via interfacial polymerization (IP). EVOH‐PDA possesses a submicron pore size and super‐hydrophilic surface, which provides abundant thin water layers covering nanofibers in the IP process resulting in the PA layer with a morphology of coral‐reef‐like highland surrounded by flat low‐lying regions. The resultant NF membrane presents high permeance of 32.19 L m−2h−1bar−1 and high rejection of 96.52% to 1000 ppm Na2SO4 feed solution with a stable performance against operation time and high salt concentration. This work provides a new approach to fabricating PA TFNC membranes with outstanding NF performance in liquid separation applications.

Mesoporous hollow nanospheres with amino groups for reverse osmosis membranes with enhanced permeability

Aiming at enhancing the permeability of reverse osmosis (RO) membranes, polyaniline-co-polypyrrole hollow mesoporous nanospheres (PPHMNs) were synthesized with aniline and pyrrole monomers via a simple and rapid one-step method, and then added to the aqueous phase of interfacial polymerization to fabricate thin-film nanocomposite (TFN) membranes. Hollow cores of the PPHMNs embedded in polyamide layers could reduce the interior transfer resistance of the membrane and shorten the transmission pathway of water molecules. Mesoporous shell of PPHMNs provided more channels for rapid transmission of water molecules. Moreover, amino groups in PPHMNs originated from the monomer of aniline could not only be bonded to polyamide (PA) layer by reacting with acyl chloride groups to prevent the leakage but also improve hydrophilicity of the membrane. Water flux of TFN membrane doped with PPHMNs (TFN-Ps) of 0.005 wt% addition concentration was 34.1 L·m−2·h−1 which is 76.7% higher than that of thin-film composite (TFC) membrane, and the NaCl rejection all kept over 99.0%. The TFN-Ps also showed excellent long-term stability, chlorine resistance and anti-fouling performance. This work opens an avenue for application of mesoporous hollow nanospheres with amino groups synthesized by simple and time-saving methods in developing TFN membranes with improved water flux.

Thin-Film Nanocomposite Forward Osmosis Membranes Prepared on PVC Substrates with Polydopamine Functionalized Zr-Based Metal Organic Frameworks

Thin-Film Nanocomposite Forward Osmosis Membranes Prepared on PVC Substrates with Polydopamine Functionalized Zr-Based Metal Organic Frameworks

Assessing the properties of thin-film nanocomposite membrane embedded with GO nanosheets using the DSPM-DE model

In this work, the effect of embedding graphene oxide (GO) nanosheets into the polyamide (PA) layer of thin-film nanocomposite (TFN) membrane properties, including the pore radius (rp), pore dielectric constant (εp), and charge density (Xd), was studied by applying Donnan-steric-pore-model-dielectric-exclusion (DSPM-DE) model. A TFN membrane was fabricated via interfacial polymerization by dispersing GO in an aqueous m-phenylenediamine solution. Characterizations using atomic force microscopy, zeta potential and contact angle of fabricated TFN membrane showed a smooth surface, a high negative surface charge and hydrophilic nature. X-ray photoelectron spectroscopy and Fourier transform infrared analyses confirmed the incorporation of GO in the PA layer of the TFN membrane. The Supply–Demand-Based Optimisation (SDO) algorithm was applied as an appropriate technique to fit experimental values of NaCl rejection with the DSPM-DE model to predict membrane properties. The SDO algorithm showed an excellent agreement between experimental data and the DSPM-DE model and the ability to predict accurate values of TFN membrane characteristics. The obtained results indicate no significant effect of GO nanosheets on the pore radius of the PA layer. The Xd of membranes increased toward negative with NaCl concentration due to adsorbing chloride ions onto the membrane surfaces. The Xd increase in TFN membrane was more because of GO presence; thereby TFN membrane performance improved. The εp value of the solution inside pores for the TFC membrane decreased more than the TFN membrane.

Nano-filtration performance and temperature dependency of thin film composite polyamide membranes embedded with thermal responsive zwitterionic nanocapsules

Incorporation of thermal responsive nanofillers is a promising strategy to induce thermal responsiveness in thin film nanocomposite (TFN) polyamide NF membranes. In this work, thermal responsive zwitterionic nanocapsules (ZNCs) were embedded in the polyamide (PA) active layers to form thermal responsive water transporting channels for thermal responsive nanofiltration performance. The impact from loading level, diameter, cross-linker ratio, and core/shell ratio of ZNCs on the structure, nanofiltration (NF) performance, and thermal responsive sensitivity of TFN membranes were systematically investigated. It was found that ZNCs with the diameter of 100–110 nm, cross-linker ratio of 50 wt% and core/shell ratio of 3:1, and loading level of 0.01% w/v in aqueous phase had induced the highest permeance change slope of 1.04 L m−2 h−1·bar−1 °C−1 (LMHBC) and flux change slope of 6.24 L m−2·h−1·°C −1(LMHC) for ZNCs-TFN membrane, which was 8.7 times higher than that of the pristine TFC-PA NF membranes. The water flux of such ZNCs-TFN membrane increased from 57 L m−2 h−1 (LMH) to 88 LMH at 0.6 MPa from 25 °C to 30 °C without losing its salt rejection rates.

Thin-film nanocomposite forward osmosis membrane for water desalination: synthesis, characterization and performance improvement

Abstract The major scope of this study is the fabrication and development of a substrate and polyamide rejection layer for an efficient thin-film hydrophilic composite forward osmosis (TFC-FO) membrane. Fabrication of a thin-film nanocomposite forward osmosis membrane employing interfacial polymerization and modification of substrate characteristics using titanium dioxide (TiO2) nanoparticles as additives (TFNC-FO) are studied. Characterizations of the prepared TFC-FO and TFNC-FO membranes were determined. The morphologies of cross-section, upper and bottom surfaces for the TFC-FO and TFNC-FO membranes were studied using scanning electron microscopy (SEM). Energy-dispersive X-ray (EDX) spectroscopy was used to examine the compositions of different elements for both membranes. The hydrophilicity of the prepared TFC-FO and TFNC-FO membranes was investigated using the measurement of the contact angle test. A Fourier Transform Infrared (FT-IR) spectrophotometer was used to observe the existing functional groups of the TFC-FO and TFNC-FO membranes. The thermal stability of the membrane was evaluated via thermogravimetric analysis (TGA). The overall performance of TFC-FO membranes was evaluated with and without adding TiO2 nanoparticles through different parameters, such as membrane flux, initial feed concentration, draw solution concentrations, reverse solute fluxes, membrane permeabilities, and finally, the effect of FO membrane orientations. FO membrane performance was successfully enhanced by adding different concentrations of TiO2 nanoparticles from 0.5 to 1.5 wt%. The findings indicated that an increase in the concentration from 0.5 to 1 wt% leads to a clear increase in both the porosity and hydrophilicity of the nanocomposite substrate and consequently, an increase in the water flux. However, further increasing the concentration of TiO2 nanoparticles to more than 1 wt% affects the membrane performance.

In situ assembled zeolite imidazolate framework nanocrystals hybrid thin film nanocomposite membranes for brackish water desalination

Metal organic frameworks (MOFs) can provide additional angstrom-scale channels for unimpeded transport of water, thus various attempts are increasingly being made to effectively embed them into polyamide (PA) nanofilms. Conferring the inherent advantages of MOFs nanofillers to the thin-film nanocomposite membranes (TFN) remains challenging. Here, a novel coordination-driven in-situ self-assembly strategy is proposed for fabricating ZIF-8 nanocrystals hybrid TFN membrane with enhanced remarkably desalination performance. In this way, ZIF-8 nanocrystals are evenly in-situ grown onto the porous ultrafiltration substrate induced by poly(sodium 4-styrenesulfonate) (PSS)-metal ions complex interlayer, then are wrapped in-situ into PA active layer without agglomeration and defects via interfacial polymerization (IP) process. Benefiting from the homogeneous incorporation of ZIF-8 nanofillers, the optimal TFN-ZIF-8 membrane evinces a water flux of nearly four times that of the traditional TFC membrane, while remaining an improved NaCl rejection (∼99.03%). Moreover, the in-situ assembled ZIF-8 nanocrystals layer can tune surface morphology to evolve from typical leaf-like structures to smooth nodular features. Consequently, the significantly decreased surface roughness and increased surface hydrophilicity endow the TFN-ZIF-8 membrane with superior antifouling performance. In addition, it is universal for other MOFs nanofillers (ZIF-67 and HKUST-1) to fabricate the highly-permeable hybrid TFN membranes. Therefore, this work promotes the advancement of competent TFN membranes to overcome the current bottleneck for brackish water desalination.

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

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

Treatment of textile industry wastewater by using high-performance forward osmosis membrane tailored with alpha-manganese dioxide nanoparticles for fertigation.

Forward osmosis (FO) technology has been acknowledged as an energy-efficient cutting-edge water treatment innovation; however, the inefficient performance of polymer-based membranes remains a tailback in the practical utilization of FO. A significant issue in FO is membrane fouling, which negatively influences the flux efficiency, working expenses and membrane life expectancy. Membranes having high water flux and minimum reverse solute flux at low operating pressures are the ideal membranes for this process. This study reports a thin-film nanocomposite (TFNC) membrane for the treatment of textile industry wastewater utilizing fertilizer as draw solution fabricated via the phase inversion process. The chemical structure and morphology of the synthesized manganese oxide (MnO2) incorporated membrane were studied by various characterization techniques like X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy-energy-dispersive X-ray spectroscopy, contact angle and gravimetry. The outcomes demonstrated that the nanoparticles were bonded to cellulose acetate polymer via covalent bonds and showed very hydrophilic membrane surface, along with an increased osmotic water flux of 52.5 L.m2.h-1 and reverse salt flux of 10.9g.m2.h-1, when deionized wastewater and potassium chloride were used as the feed solution and the draw solution, respectively. In this manner, incorporating manganese oxide into the FO membrane may introduce its extraordinary possible application for the production of diluted fertilizer solution with balanced nutrients.

Capillary-Assisted Fabrication of Thin-Film Nanocomposite Membranes for Improved Solute-Solute Separation.

Efficient separation of harmful contaminants (e.g., per- and polyfluoroalkyl substances, PFASs) from valuable components (water and nutrients) is essential to the resource recovery from domestic wastewater for agricultural purposes. Such selective recovery requires precise separation at the angstrom scale. Although nanofiltration (NF) has the potential to achieve solute-solute separation, the state-of-the-art polyamide (PA) membranes are typically constrained by limited precision of solute-solute selectivity and their well-documented permeability-selectivity trade-off. Herein, we present a novel capillary-assisted interfacial polymerization (CAIP) approach to generate metal-organic framework (MOF)-PA nanocomposite membranes with reduced surface charges and more uniform pore sizes that favor solute selectivity by enhanced size exclusion. By uniquely regulating the PA-MOF interactions using the capillary force, CAIP results in effective exposure of MOF nanochannels on the membrane surface and a PA matrix with a high cross-linking gradient in the vertical direction, both of which contribute to an exceptional water permeance of ∼18.7 LMH/bar and an unprecedentedly high selectivity between nutrient ions and PFASs. Our CAIP approach breaks new ground for utilizing nanoparticles with nanochannels in fabricating the next-generation, fit-for-purpose NF membranes for improved solute-solute separations.

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

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

Amino-embedded carbon quantum dots incorporated thin-film nanocomposite membrane for desalination by pervaporation

This study provides an in-depth investigation on the incorporation of carbon quantum dots (CQDs) in fabricating novel thin-film nanocomposite (TFN) membranes to address the high demand for highly water-permeable pervaporation (PV) membranes for desalination processes, especially for treating high-salinity water, brine, or wastewater. CQDs have emerged as a green nanofiller for improving membrane performance owing to its excellent biocompatibility, non-toxicity, uniform dispersion, and rich functional groups. Herein, we synthesize amino-embedded carbon quantum dots (ACQDs) via a simple one-pot hydrothermal method and employ them in interfacial polymerization to fabricate the ACQD-TFN membrane. Benefiting from the incorporation of ACQDs, the optimized ACQD-TFN membrane exhibited an enhanced water flux of 23.2 kg·m−2·h−1 at 70 °C during the treatment of a 10 wt% NaCl solution, which was 44% higher performance than that of the unmodified thin-film composite membrane. The ACQD-TFN membrane's salt rejection remained at 99.9% even after 96,000 ppm·h chlorine exposure, exhibiting excellent chlorine resistance. Also, the ACQD-TFN membrane's regular surface microstructure and increased hydrophilicity endowed good anti-fouling property, and its flux recovery rate reached 91% after 5 fouling-cleaning cycles. This work provides a feasible strategy for fabricating highly permeable, chlorine-resistant, and anti-fouling PV membranes for desalination applications.