Polyamide Thin Film Research Articles

Fabrication and Optimization of Parameters of High-Performance Polyamide Thin Film Composite Membranes for Desalination

Abstract Herein, we report the synthesis of polyamide thin film composite (PA-TFC) membranes through interfacial polymerization (IP) using an aqueous solution of diaminodiphenylmethane (DDM) and terephthaloyl chloride (TPC) in n-hexane, onto polysulfone (PSF) surface. The synthesized membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscope (SEM) and contact angle measurement. To optimize the conditions for achieving a better membrane function, desalination (%) and permeate flow rate (L/m2.h.bar) were evaluated as a function of synthesis conditions. The membrane efficiency for salt rejection was evaluated against NaCl using a bench-top cross-flow filtration assembly where the membrane showed up to 73.13% salt rejections of NaCl. While, the salt rejection of Na2SO4 and MgSO4 were showed up to 84.92% and 82.94%. The promising synthesized membranes exhibited a permeate flux of 41.7 L/m2.hr.bar. The contact angle analysis revealed that the synthesized PA-TFC membranes are hydrophilic as the value of contact angle measured as 109°-100°. The synthesized membrane offered facile and effective access for the synthesis of high-performance PA-TFC membranes.

Using zero nano-valent iron/thin film composite (ZNVI/TFC) membrane for brackish water desalination and purification

This study looked at the use of synthetic Zero Nano-valent Iron (ZNVI) particles in a unique interfacial polymerization technique on a polyamide thin film PA(TF) composite membrane for the treatment and desalination of brackish wastewater. Zero nano-valent iron (ZNVI) particles were created utilizing chemical reduction technique. ZNVI/PA(TF) NCs membrane is the outcome of advancing the PA(TF) membrane by combining with different concentration of ZNVI particles into the organic phase 1,3,5-benzenetricarbonyl trichloride (TMC). ZNVI/PA(TF) NCs membranes and ZNVI particles' surface properties were examined by the use of mechanical activity, contact angle, BET, FTIR, SEM, XRD, zeta potential, TEM analysis, and EDX studies. Using a variety of salt solutions, such as NaCl, Na2SO4, MgSO4, NaHCO3, CaSO4, CaCl2, and MgCl2, the ZNVI/PA(TF) NCs membrane performance towards salt rejection, flux (at varying pressure), anti-fouling activity, and ZNVI particles stability was assessed. This work investigated the removal efficiency of four dyes: methylene blue (MB), methyl orange (MO), Congo red (CR), and malachite green oxalate (MG). The water flux of the pristine PA(TF) membrane improved from 22 to 35 L/m2.h at 15 bar, indicating a 63% flux enhancement and the NaCl rejection was improved from 88.5 to 98.6%, indicating an 11.4% rejection improvement by incorporation of 0.3 wt.% of ZNVI particles into PA(TF) matrix. The ZNVI/PA(TF) NCs membrane's separation performances were evaluated using 5000 mg/L feed solutions of various salts at 15 bar. It was discovered that the water flux and salt rejection are, respectively, 33.4, 33, 32.7, 32, 31, 30 and 29 L/m2.h for CaSO4, MgSO4, Na2SO4, NaCl, CaCl2, MgCl2, and NaHCO3, and 97.4, 97, 96.5, 96, 94, 93.2, and 92.8%. It demonstrates that the flux recovery ratio (FRR) of the ZNVI/PA(TF) NCs membrane is greater than that of pristine PA(TF) (78%), coming in at 87%. High stability and fixing of the ZNVI particles on the modified membrane surface is indicated by the low overall ZNVI particles release rate over the course of the 10-day experiment.

Self-assembled nanoflower-mediated interfacial polymerization through tunable intra- and inter-layer channels to boost total heat exchange performance

Total heat exchange membranes (THEMs) are vital for minimizing energy consumption and enhancing indoor air quality in energy recovery ventilation (ERV) systems. Manipulating the surface morphology of polyamide (PA) membranes via nanofiller-mediated interfacial polymerization is key to advancing total heat recovery performance. This study presented the fabrication of PA thin-film nanocomposite (TFN) membranes by integrating self-assembled poly(amic acid-imide) nanoflowers (P(AA-I)-NFs) with intertwined nanosheets into the organic phase. This facile approach effectively eliminated nonselective interphase voids and defects, owing to the superior polymer affinity of the organic nanoflowers. The finely tuned intra- and inter-layer channels within P(AA-I)-NFs significantly impacted monomer mass transfer, facilitated the shuttle effect, expanded the interfacial polymerization zone, and led to the formation of a rougher, thicker PA layer with enhanced surface area. The optimized P(AA-I)-NFs/PA TFN membranes exhibited outstanding performance, including CO₂ permeability of 0.51 GPU, water vapor permeability of 656.59 GPU, and an enthalpy exchange efficiency of 71.47 %, surpassing the trade-off limitations typically observed in commercial and other advanced THEMs. These findings underscored the potential of P(AA-I)-NFs-mediated TFN membranes as highly competitive candidates for next-generation ERV systems.

Expanding interfacial polymerization for gas separation beyond water purification

Extending interfacial polymerization (IP) to gas separation is challenging due to microdefects in dry conditions, despite its attractive and straightforward processability. This study presents a systematic defect-tailoring approach for highly reproducible polyamide (PA) thin film composite (TFC) membranes with precise size-sieving ability. The approach combines highly porous polyethylene support, extended IP reaction time (60 min), and post-thermal/solvent treatments, resulting in a homogeneous PA selective layer. Particularly, isopropanol treatment removes less-reacted amine-rich monomers/oligomers and promotes PA network chain relaxation, enhancing molecular-sieving capability. The resulting PA TFC membrane exhibits a remarkable H2/CO2 selectivity of 24.8 (±3.1) and an H2 permeance of 13.6 (±1.8) gas permeation unit, surpassing the polymeric upper bound. It also ensures mechanical stability under high feed pressure and resistance to physical aging, highlighting its robustness. Additionally, universality is validated using different amine monomers. This systematic method provides a valuable framework for producing reproducible PA TFC membranes with exceptional gas separation performance, enabling practical implementation across industrial sectors.

Brine separation with polyamide and polyimine thin film composite nanofiltration membranes obtained from biobased monomers

Thin film composite (TFC) membranes are state-of-the-art membranes that are widely applied in water treatment and seawater desalination. However, these membranes are typically prepared using petrochemical-based monomers and toxic solvents. Herein, plant-based monomers, namely priamine (PA), 2,5-furandicarboxaldehyde (FDA) are used to fabricate green PA–FDA TFC membranes via interfacial polymerization. Additionally, PA was also combined with trimesoyl chloride (TMC) to obtain PA–TMC TFC membranes. The reaction conditions were varied to investigate their effects on membrane morphology and performance. The resultant membranes exhibited smooth surfaces with an average roughness ranging from 15 to 30 nm, and increasing the monomer concentration increased the film thickness. The PA–TMC free-standing films had higher thicknesses (130–300 nm) than the PA–FDA films (36–122 nm). Furthermore, PA–TMC and PA–FDA films were hydrophobic due to the long aliphatic chains of PA. Moreover, PA–TMC membranes demonstrated a water permeance of ∼4 L m−2 h−1 bar−1 with 74% NaCl rejection, while PA–FDA membranes achieved better NaCl rejection (∼80%) but lower water permeance (0.3–4 L m−2 h−1 bar−1). Applied in brine separation, the membranes demonstrated ∼90% divalent ion rejection and only 70% monovalent ion rejection. The proposed plant-based monomer combination provides a steppingstone toward green TFC membrane manufacturing for water treatment and desalination applications.

A facile solvent activation process manipulates the structure and filtration performance of oxidized poly (arylene sulfide sulfone) TFC membrane

In this study, solvent-resistant polyamide (PA) thin film composite (TFC) nanofiltration (NF) membranes were successfully prepared based on an ultrasolvent-resistant oxidized poly (arylene sulfide sulfone) (O-PASS) substrate. The effects of different substrates on interfacial polymerization (IP) process were systematically studied. The O-PASS-TFC membranes were activated to different degrees by a controlled activation process using the mixture solvent of DMF/H2O with different ratio of DMF, the solubility power can be designed by adjusting DMF volume fraction, as the activation solvent. The membrane followed pure DMF treatment was found to have the excellent performance: the surface morphology of TFC membrane was activated to smooth and high negative charged, yield nanofiltration (NF) performance with a solution permeance of 8.82 LMH bar−1 (~621 % increase) and a pure water permeance (PWP) of 11.59 LMH bar−1 (~607 % increase), Na2SO4 rejection maintained above 98.7 %. On the other hands, the same O-PASS-TFC membrane activated with solvent mixture volume ratio of DMF/H2O = 0.5 exhibited enhanced Na2SO4 rejection of 99 %, with greater solution permeance of 3.01 LMH bar−1 (~212 % increase). The correlations between the different activation treatment-membrane structure-separation properties of O-PASS-TFC membranes with different solvent activation degrees were investigated in detail. In this work, the ultrasolvent-resistant property of O-PASS substrate was combined to regulate its TFC membrane structure, and then further to endow the TFC membrane with multiple excellent filtration performance by fully utilizing the solvent activation effect of DMF. Through this strategy, it supplies a facile and promising route for preparation of high efficiency TFC membrane.

Pentahomoserine functionalized graphene oxide decorated polyamide thin film for enhanced separation of green tea polyphenols

The isolation of valuable compounds from the byproducts of food processing industries presents a significant contemporary challenge. Thin film nanocomposite (TFN) membranes have been identified as potential media for separating bioactive compounds. In this work, pentahomoserine functionalized graphene oxide (FGO) based TFN membranes were prepared for the effective separation of tea polyphenols epigallocatechin (EGC) and epigallocatechin gallate (EGCG). The nanocomposite selective polyamide (PA) layer was prepared through the dispersion of FGO in an aqueous monomer solution. The prepared membranes possess high average surface roughness with improved hydrophilicity and thermal stability. Additionally, FGO membranes contain more hydroxyl or carboxyl groups with cross-linked PA layer through interfacial polymerization (IP) process. Moreover, FGO membranes featured increased hydroxyl or carboxyl groups, facilitating cross-linking with the PA layer via intermolecular forces. The effects of amine functionality on the membrane characteristics such as surface morphology, roughness and hydrophilicity were also investigated. Remarkably, the membranes demonstrated rejection efficiency of 96.3% towards polyphenols. Furthermore, comprehensive assessments of reusability performance of the membrane highlighted their potential for industrial applications. This study provides valuable insights into the fabrication of highly efficient TFN membranes for biomolecule separation across diverse technological domains.

Characterization of polyamide thin films by atomic force microscopy

This study directly compares the mechanical behavior of novel molecular layer deposition (MLD) and analogous interfacial polymerization (IP) polyamide thin films in environments relevant to reverse osmosis (RO) membrane operation. The elastic modulus of the films was determined using atomic force microscopy (AFM) in dry, hydrated, and chlorinated states. Surface roughness characteristics were also obtained given their potential influence on AFM modulus measurements. The much smoother MLD films demonstrated a statistically higher modulus in all states as compared to their IP counterparts. The MLD films maintained a modulus ∼3X and ∼5X greater than that of IP films after hydration and chlorination, respectively. Such differences in behavior may be due to the higher density and correspondingly lower void content of the MLD films. Results from this study provide a rationale for future development of MLD for fabrication of polyamide films for incorporation in RO membranes.

High-temperature reverse osmosis and molecular separation with robust polyamide-ceramic membranes

Polyamide thin-film composite (TFC) membranes are widely used for reverse osmosis (RO), but most commercial RO membranes have a limited operating temperature of <45 °C. This has constrained the broader applications of RO in industries, where process and water feeds with high temperature >50 °C are common. In this study, robust polyamide-ceramic TFC membranes were developed for high-temperature RO (HT-RO). RO-type polyamide thin-film was successfully synthesized on the inner surface of ceramic tubular membranes via interfacial polymerization. The polyamide-ceramic membranes exhibited excellent thermal stability, maintaining high NaCl rejection (>98 %) and steady water permeability (∼5 LMH/bar) during HT-RO at 70 °C. The molecular weight cut-off (MWCO) of the membranes increased slightly from 90 to 140 Da at 70 °C, and the surface charge played an important role in maintaining the high salt rejection. Long-term stability tests showed that polyamide thin-films may undergo thermal hydrolysis at 80 °C. It was also found that polymeric substrates of flat-sheet RO membranes may experience serious compaction at high temperature, which could subsequently affect the performance and stability of the polyamide layer. The ceramic substrates provide strong support at high temperature, and the highly stable polyamide-ceramic membranes demonstrated huge potential for RO applications under more challenging conditions.

Influence of polar solvent in formation and organic solvent separation performance of novel fluorine-containing polyamide membranes

Polyamide thin film composite (PA-TFC) membranes have shown great potential in organic solvent separations. However, the intrinsic polar feature of the amide group limits their permeability to specific solvents, such as nonpolar solvents. In this study, we used a fluorine-containing monomer [4,4′-oxybis(3-(trifluoromethyl)aniline), OTFA] to conduct interfacial polymerization (IP) with trimesoyl chloride, resulting in the fabrication of novel PA-TFC membranes with permeability to both polar and nonpolar solvents. Interestingly, by simply adjusting the composition of OTFA solvents [DMF and DMF/water (1:1, v: v)], we obtained two PA-TFC membranes (OTFA-D and OTFA-DH, respectively) featuring completely different structures and surface properties, including PA layer thickness, water contact angle, surface element composition, surface charge, and polarity. Due to their distinct structures and surface features, the two membranes exhibited different performances in organic solvent nanofiltration (OSN). The OTFA-DH membrane showed higher permeability to polar solvents (e.g., methanol), while the OTFA-D membrane was more permeable to nonpolar solvents (e.g., toluene). The mechanism on the formation of the two PA layers was clarified by combining the experimental results with the molecular dynamics simulations. The significantly different interfacial properties and monomer diffusion during IP led to the substantial differences in the formation of the PA network. This work provides a strategy to fabricate tailored PA-TFC membranes for various OSN scenarios by simply adjusting the solvent compositions.

Enhancing ion separation efficiency: Janus charged nanofiltration membrane fabricated via polyethyleneimine-manipulated interfacial polymerization

This research introduces highly efficient nanofiltration (NF) membranes designed for the effective rejection of both divalent cations and anions, a critical feature for advanced water treatment technologies. We have devised a simple yet adaptable approach for fabricating Janus polyamide (PA) thin-films characterized by dual charges, which exhibit pronounced selectivity towards both mono-/divalent anions and cations. Leveraging a straightforward interfacial polymerization (IP) process, we integrated high molecular weight polyethyleneimine (PEI) within the PA matrix. This strategy ensured the preferential formation of a dense, negatively charged upper layer dominated by piperazine (PIP), while cationic macromolecular PEI facilitated the emergence of a loose and positively charged lower layer, thus giving rise to a distinctively charged and structurally heterogeneous PA thin-film. Furthermore, the strategic inclusion of PEI inhibits the diffusion of the PIP, thereby promoting the development of nano-wrinkled structures. This structural innovation not only enhances pure water permeance (16.0 L m−2 h−1 bar−1) but also optimizes ion selectivity through the coordination of steric hindrance and Donnan effects. Consequently, the Janus charged NF membranes we developed exhibit exceptional selectivity for mono-/divalent ions, particularly demonstrating remarkable ion selectivity for Cl−/SO42− and Li+/Mg2+ of 102 and 24, respectively. Our findings introduce a pioneering avenue for fabricating NF membranes that proficiently separate mono-/divalent ions, promising significant advancements in water treatment and purification endeavors.

Improved performance of polyamide nanofiltration membrane embedded with zeolite beta

In this study, zeolite beta nanoparticles were incorporated into an interfacial polymerization procedure for the fabrication of thin film nanocomposites (TFNs). The successful introduction of zeolite beta into the polyamide (PA) selective layer was confirmed by surface attenuated total reflection infrared spectroscopy (ATR-FTIR), and x-ray photoelectron spectroscopy (XPS). The introduction of porous structured zeolite beta improved the water flux and rejection rate of the TFN membrane compared to the PA thin film composite (TFC) membrane. A quantitative performance coefficient is further proposed in this work, comprehensively considering the flux and rejection rate to evaluate the performance of TFNs. For five salt solutions, we found that the TFN0.3 membrane with 0.3 wt% of zeolite particles had a high coefficient of performance. With the help of zeolite particles, the TFN0.3 membrane achieved a high flux of 92.53 L/(m2·h) under an operating pressure of 5 bar. For ion separation from binary solutions, the TFN0.2 membrane with 0.2 wt% zeolite content was a better choice for a wide range of binary mixtures, which is because the addition of zeolite beta resulted in smaller pore sizes, the strongest zeta potential, and the thickest thickness (scanning electron microscope, SEM determined) of the TFN0.2 membrane. All these factors contribute to the selectivity of the TFN0.2 membrane. Our study provides an efficient and cost-effective method to simultaneously improve the permeability and rejection of nanofiltration membranes, facilitating the development of nanofiltration for water recovery.

Optimizing ionic conductivity and ion selectivity in zinc-polyiodide flow batteries with composite polyamide-porous separators

Owing to their superior theoretical energy capacity, zinc-polyiodide flow batteries (ZIFBs) are well-known energy storage devices. The practicality of ZIFBs depends on the development of cost-effective separators that can demonstrate both excellent ionic conductivity and selective ion permeability. Herein, an economical polymer blend comprising poly (ether sulfone) (PES) and sulfonated poly (ether ether ketone) (sPEEK) is fabricated via a phase inversion technique. Due to the formation of a sponge-like structure, the porous substrate indicates high ionic conductivity. Furthermore, the selected porous substrate is coated with a thin-film polyamide, synthesized from m-phenylenediamine (MPD) and 1,3,5-benzene tricarbonyl trichloride (TMC) via interfacial polymerization (IP). This polyamide layer can efficiently mitigate the undesired migration of triiodide ions, while maintaining high ionic conductivity. This innovative approach yields a composite separator having a deftly tunable structure. Using such a separator, ZIFBs can operate stably with high coulombic efficiency (CE) of 91 % over 100 cycles at a current density of 10 mAh cm−2. Overall, this study explores the trade-off between ionic conductivity and ion permeability. It is seen that by adjusting their morphology, the physical characteristics of the composite separators can be improved, ensuring stable and efficient operation of ZIFBs.

Evaluating Post-Treatment Effects on Electrospun Nanofiber as a Support for Polyamide Thin-Film Formation.

Poly(acrylonitrile-co-methyl acrylate) (PAN-co-MA) electrospun nanofiber (ENF) was used as the support for the formation of polyamide (PA) thin films. The ENF support layer was post-treated with heat-pressed treatment followed by NaOH hydrolysis to modify its support characteristics. The influence of heat-pressed conditions and NaOH hydrolysis on the support morphology and porosity, thin-film formation, surface chemistry, and membrane performances were investigated. This study revealed that applying heat-pressing followed by hydrolysis significantly enhances the physicochemical properties of the support material and aids in forming a uniform polyamide (PA) thin selective layer. Heat-pressing effectively densifies the support surface and reduces pore size, which is crucial for the even formation of the PA-selective layer. Additionally, the hydrolysis of the support increases its hydrophilicity and decreases pore size, leading to higher sodium chloride (NaCl) rejection rates and improved water permeance. When compared with membranes that underwent only heat-pressing, those treated with both heat-pressing and hydrolysis exhibited superior separation performance, with NaCl rejection rates rising from 83% to 98% while maintaining water permeance. Moreover, water permeance was further increased by 29% through n-hexane-rinsing post-interfacial polymerization. Thus, this simple yet effective combination of heat-pressing and hydrolysis presents a promising approach for developing high-performance thin-film nanocomposite (TFNC) membranes.

Acid and chlorine-resistant cations selective nanofiltration membranes derived from Hoffmann alkylation reaction

Conventional polyamide and polyester thin film composite membranes (TFCMs) are susceptible to harsh conditions, because the amide and ester bonds in them will degrade under extreme pH or chlorine oxidants. This work addressed this problem by preparing TFCMs through the Hoffmann alkylation reaction. Two monomers, i.e., 1,4,7,10-Tetraazacyclododecane (TAD) and 1,2,4,5-Tetrakis(bromomethyl)benzene (TBB), were designed and underwent interfacial alkylation on polyacrylonitrile substrate. The TAD-TBB TFCMs feature high positive charge, and show good repulsion (>90%) to divalent cations. Benefiting from the stability of “C-N-C” bonds in TAD-TBB network, both the permeance (13.7 L m−2 h−1 bar−1) and cation rejection (90.3%–91.4%) of the TAD-TBB TFCMs are stable after being immersed in 2 M HCl for 21 days. Meanwhile, the TAD-TBB TFCMs maintained good separation performance (permeance: 13.9 L m−2 h−1 bar−1, MgCl2 rejection: 90.5%–92.2%) after a total free chlorine exposure of 96000 ppm h (200 ppm for 480 h). This work reported the preparation of cation-selective membranes stable in harsh environments.

Covalent Organic Framework Membranes and Water Treatment.

Covalent organic frameworks (COFs) are an emerging class of highly porous crystalline organic polymers comprised entirely of organic linkers connected by strong covalent bonds. Due to their excellent physicochemical properties (e.g., ordered structure, porosity, and stability), COFs are considered ideal materials for developing state-of-the-art separation membranes. In fact, significant advances have been made in the last six years regarding the fabrication and functionalization of COF membranes. In particular, COFs have been utilized to obtain thin-film, composite, and mixed matrix membranes that could achieve effective rejection (mostly above 80%) of organic dyes and model organic foulants (e.g., humic acid). COF-based membranes, especially those prepared by embedding into polyamide thin-films, obtained adequate rejection of salts in desalination applications. However, the claims of ordered structure and separation mechanisms remain unclear and debatable. In this perspective, we analyze critically the design and exploitation of COFs for membrane fabrication and their performance in water treatment applications. In addition, technological challenges associated with COF properties, fabrication methods, and treatment efficacy are highlighted to redirect future research efforts in realizing highly selective separation membranes for scale-up and industrial applications.

A novel wholly-Tröger's Base-based polyamide nanofiltration membrane constructed for the separation application in strong acidic condition via acid-induced segregation

In this study, a new kind of wholly-Tröger's base-based polyamide (wTB-PA) thin film composite (TFC) nanofiltration (NF) membrane was successfully fabricated for the separation application in strong acidic condition via the acid-induced segregation (AIS) effect. Firstly, the self-synthesized Tröger's base diamine monomer — 2,8-diamino-4,10-dimethyl-6H,12H-5,11-methanodibenzo [1,5]-diazocine (TBDA) was added in the polyethersulfone (PES) casting solution to prepare the TBDA-based PES substrate by synchronously coupling the non-solvent-induced phase transformation (NIPs) and AIS, and then the TBDA molecules on the PES substrate surface further reacted with trimesoyl chloride (TMC) via interfacial polymerization (IP) to obtain the wTB-PA TFC NF membranes. Meanwhile, the acid-induced segregation effect of on the microstructure and separation performance of the wTB-PA TFC NF membrane were systematically investigated. As compared with the conventional poly(piperazine amide) NF membrane (MPIP-TMC), the wTB-PA NF membranes exhibited thinner, smoother but more hydrophobic surface as well as lower isoelectric point, and especially showed much higher tolerance to 20 wt% H2SO4 after soaking 63 days and favorable dye rejection (～99.9 %). Thereinto, the acid segregation agent of citric acid monohydrate (CA) endowed the wTB-PA TFC NF membrane with relatively optimal acid resistance and SO42−/Cl− separation selectivity (about 11.8) than glacial acetic acid (AC), nitric acid (HNO3) and hydrochloric acid (HCl). Moreover, this wTB-PA NF membrane based on CA-induced segregation had higher recovery of the positively charged dye of methyl orange (MO) (＞98.0 %) in acidic condition. Therefore, the wTB-PA TFC NF membranes have great potential for the separation application in the strong acidic condition in the future.

In-situ interfacial synthesis of metal-organic framework/polyamide thin-film nanocomposite membranes with elevated nanofiltration performances

Incorporation of nanomaterials in the thin film polyamide (PA) is instrumental to overcome the intrinsic trade-off between permeability and selectivity of polymeric nanofiltration (NF) membranes. However, the universal method of preparing thin film nanocomposite (TFN) NF membranes by directly combining the synthesized nanofillers into PA faces a stubborn issue of poor compatibility for filler-PA, which is adverse to membrane separation. Herein, an in-situ interfacial synthetic strategy was induced in interfacial polymerization (IP) process to prepare TFN membranes with metal-organic framework (MOF) in the PA selective layer. The metal ions and ligands constituting the MOF were dissolved individually in the aqueous and organic phases. MOF particles and the PA layer were simultaneously formed at the liquid-liquid interface. The increment of cross-linking degree confirmed the good compatibility between MOF and PA. Compared with the thin film composite (TFC) membrane, the acquired TFN-1 membrane exhibited 100 % enhancement of pure water permeance (from 10.0 to 20.6 L m−2 h−1 bar−1) due to the markedly reduced thin film thickness. Meanwhile, the rejection of rhodamine B (99.9 %) and Na2SO4 (96.5 %) for TFN membrane were higher than those of TFC membrane (97.2 % and 95.6 %), respectively. The TFN membrane exhibited long-term stability without deterioration. The in-situ interfacial synthesis of the MOF/PA layer provides a new avenue in TFN membrane fabrications.

A portable smartphone platform utilizing dual-sensing signals for visual determination of semicarbazide in food samples.

Semicarbazide (SEM) is a metabolite of antibiotic nitrofurazone and a food contaminant in food production, showing potential carcinogenic, mutagenic, teratogenic, and toxic effects on human health. It is urgent to develop a highly efficient and sensitive assay for visual detection of SEM. In this paper, a pyrrolopyrrole cyanine fluorescent probe (PPCy-1) was reported for visualization and quantitative analysis of SEM through a chromophore reaction sensing mechanism for the first time. The probe towards SEM exhibited a fast response (10 min), a low detection limit (0.18 μM), high selectivity, and distinct dual ratiometric fluorescence turn-on and colorimetric modes. Its practicability was further verified by detecting SEM in meat, water, and honey samples with satisfactory recovery values. More importantly, a smartphone-assisted portable testing platform was constructed based on a PPCy-1-immobilized test paper or a polyamide thin film with a color scanning APP for real-time and on-site detection of SEM. This work provides low-cost, convenient, and rapid assays for visual SEM detection, which have potential applications in food safety monitoring.

Ultrahigh-permeance polyamide thin-film composite membranes enabled by interfacial polymerization on a macro-porous substrate toward organic solvent nanofiltration

Organic solvent nanofiltration (OSN) membranes have become a powerful separation platform in a myriad of chemical and pharmaceutical fields owing to their superior merits in high separation efficiency and low energy consuming. Despite extensive progress in exploiting polyamide thin film composite (TFC) membranes for OSN, they are heavily limited by inferior solvent permeability, especially when using conventional low-porous polyimide as TFC substrate. Herein, we report a facile substrate engineering strategy to leverage macro-porous Nylon66 microfiltration membrane to replace the conventional low-porous polyimide substrates for fabricating TFC membranes by interfacial polymerization, enabling high and robust solvent permeability during OSN. Distinct from conventional polyimide, Nylon66 substrates take advantage of their high porosity, macro-porous size and excellent hydrophilicity to realize more monomers storage and uniform monomers distribution, allowing to create crumpled and defect-free polyamide layers. With this method, the polyamide TFC membranes show a 2.1-fold increase in ethanol permeance (up to 16.0 L h−1 m−2 bar−1) meanwhile possessing 98 % rejection of dye, surpassing the most reported TFC membranes. We also demonstrate that the TFC membranes exhibit excellent long-term stability in both polar and non-polar solvent, as well as hold huge promise in the precise separation of dye mixture, pharmaceutical ingredient, and catalyst.