Thin Polyamide Layer Research Articles

Effect of solution flow rate on the fabrication of outer surface selective layer hollow fiber membranes for dye rejection

Various industries, such as food, petrochemicals, and pharmaceuticals, have recognized the importance of separation technologies for large molecules such as dye. A thin polyamide layer is commonly used in thin film composite membranes for separation applications, but fabricating a polyamide selective layer on hollow fiber (HF) membranes remains challenging. This research focuses on producing polyamide-based HF membranes by circulating aqueous and organic solutions during interfacial polymerization. By varying the solution flow rate, the dye rejection performance was investigated concerning morphology, polyamide thickness, mechanical properties, and hydrophilicity. All generated membranes consistently rejected over 98 % of congo red dye, with the highest rejection rate for methyl orange reaching approximately 92 %. The most efficient membranes were produced with an aqueous solution flow rate of 180 ml/min and an organic solution flow rate of 220 ml/min. These membranes exhibited notable ethanol permeance, with rejection rates of 99.75 % for congo red and 91.68 % for methyl orange. Additionally, they show promise for application in reverse osmosis processes for salt removal.

Thin polyamide layer cross-linked graphene-oxide based ceramic membranes for efficient separation of the surfactant stabilized oil-in-water emulsions

Two-dimensional (2D) graphene oxide (GO) membranes (GOM) have great potential in separation applications. However, GOMs face two distinct challenges: low flux arising from their tight stacking and instability arising from re-exfoliation of GO sheets in solution. To address these challenges, herein, we report the functionalization of basal planes of GO layers with 2-[2-(3-Trimethoxysilylpropylamino)ethylamino]ethylamine (TSE), followed by transforming them into membranes through a two-step process. In the first step, the functionalized GO sheets were assembled onto the porous ceramic support. At this stage, the interlayer distance between GO sheets was modulated via TSE’s long hydrocarbon chain. Afterward, the free amines of TSE on functionalized GO membranes (fGOM) surface were cross-linked with trimesoyl chloride (TMC) to prepare a hydrophilic thin-layer on top of fGOM (TL-fGOM), further enhancing their stability. Further, TL-fGOMs were tested for oil-in-water-emulsion separation. The increased interlayer distance and the increased surface hydrophilic nature of TL-fGOM offered ultra-high water permeance, 4860 % higher compared to the non-functionalized GOM. Moreover, the separation efficiency of TL-fGOM improved from 37 % of that of ceramic membranes to 99.5 %. Additionally, they showed excellent anti-fouling properties. After exposing the membranes to 500 ppm emulsion for 10 hours in batches, the flux recovery ratio exceeded 90 %. The TL-fGOM in our work demonstrated outstanding performance in purifying oily emulsions containing diesel/toluene/heptane-in-water. All these results revealed that the appropriate functionalization of graphene oxide could assist in forming a thin layer of graphene oxide on the support membranes, offering high separation efficiency and fouling resistance. This approach can be extended further to utilize the graphene oxide membranes for practical applications.

Combined effect of polyelectrolyte assisted interfacial polymerization and tannic acid protective surface modification to boost organic solvent nanofiltration performance

Organic solvent nanofiltration (OSN) is an effective technology for separating solute with molecular weight of 200–1000 Da (Da) from organic solvents. However, as the core of this technology, most of OSN membranes exhibit a low solvent permeance. Herein, a highly permeable OSN membrane was prepared via a poly (sodium 4-styrenesulfonate) (PSSNa)-assisted interfacial polymerization reaction using ultra-low content of aqueous monomer solution, followed by a protective modification using tannic acid (TA) grafting onto the nascent polyamide surface, and a post chemical crosslinking treatment as well as an activation treatment. PSSNa manipulates the diffusion and distribution of the m-Phenylenediamine monomers, leading to a looser and thinner polyamide layer. TA molecules successfully reacted with the remaining acyl chloride groups on the nascent polyamide layer surface and formed ester, thus preventing the surface from subsequent crosslinking reaction and also making the selective layer looser, which is beneficial for solvent permeation. Moreover, the TA modification makes the surface more hydrophilic, thus further helps to improve the solvent permeance of OSN membrane. The optimal membrane possesses an excellent ethanol permeance of 71.5 L m−2 h−1 MPa−1, an increment of 41.6 % as compared with the baseline OSN membrane, while keeping a rejection of 98.2 % for rhodamine B (RDB). Meanwhile, the surface of optimal membrane is ultra-smooth, with an average roughness of 4.4 nm, which is much beneficial for antifouling. Moreover, the OSN membrane possesses a brilliant durability performance, with only a 1.5 % decrease of the RDB rejection after being immersed in N, N-Dimethylformamide (DMF) at room temperature for 115 d, and only a further 0.3 % decrease of the RDB rejection after being further immersed in DMF at 80 °C for another 11 d, indicating its superior solvent resistance, which makes it a promising candidate for treating organic solutions from pharmaceutical and textile industries.

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.

Preparation and performance of magnetic carbon nanotubes modified PVC substrate composite nanofiltration membranes

Polyamide (PA)/ferroferric oxide/oxidized multi-walled carbon nanotubes (Fe3O4/o-MWCNTs)/polyvinyl chloride (PVC) composite nanofiltration (NF) membranes were prepared by the interfacial polymerization (IP) process with the Fe3O4/o-MWCNTs/PVC porous membrane as the substrate membrane, which was prepared by the magnetic field assisted non-solvent induced phase separation method (NIPS) with the synthesized superparamagnetic Fe3O4/o-MWCNTs nanoparticles (NPs) as the additives of the functional intermediate layer integrated with the substrate. The effects of the magnetic carbon nanotubes modified PVC porous substrate membrane on the surface chargeability, PA layer thickness, mechanical properties, pressure resistance and permeability of the composite NF membranes were investigated, and the comprehensive performance of composite NF membranes was enhanced. The results indicated that the porosity and hydrophilicity of the Fe3O4/o-MWCNTs/PVC porous substrate membrane were improved by the migration of magnetic Fe3O4/o-MWCNTs NPs to the upper edge of the substrate membrane and uniform enrichment under magnetic field induction, which further affected the structure and properties of the PA/Fe3O4/o-MWCNTs/PVC composite NF membrane. The prepared NF membrane presented smaller roughness, thinner PA layer, larger pore size, with excellent mechanical properties and better pressure resistance. Meanwhile, the PA/Fe3O4/o-MWCNTs/PVC composite NF membrane presented excellent divalent salt rejection, with the rejection of MgSO4 and Na2SO4 maintaining more than 95.2% and 93.4%, respectively, while the permeation flux could reach 35.4 L·m−2·h−1. In summary, the modification of the substrate integrated with the functional intermediate layer had certain enlightening significance for the preparation of the NF membrane with excellent comprehensive performance.

Micelles regulated thin film nanocomposite membrane with enhanced nanofiltration performance

The desalination performance of thin film nanocomposite (TFN) membranes is significantly influenced by the nature of nanofillers and the structure of the polyamide (PA) layer. Herein, a micelles regulated interfacial polymerization (MRIP) strategy is reported for the preparation of TFN membranes with enhanced nanofiltration (NF) performance. Specially, stable and ultrafine micelles, synthesized from the poly(ethylene oxide)-b-poly(4-vinyl pyridine)-b-polystyrene (PEO-PVP-PS) triblock copolymers, were utilized as regulators in the aqueous phase during the interfacial polymerization (IP) process. TFN membranes were fabricated with varying concentrations of micelles to improve their properties and performances. The structure of the PA layer was further regulated by modulating the content of trimesoyl chloride (TMC), which significantly enhances the performance of the TFN membrane with micelles. Attributable to the homogeneously dispersed micelles and the modified PA layer, the optimized membrane denoted as TFN-2–0.3 exhibits an improved separation performance of 20.7 L m-2h−1 bar−1 and 99.3 % Na2SO4 rejection, demonstrating nearly twice the permeance and 2.7 % higher rejection than that of the original control membrane, respectively. The mechanism of this MRIP strategy was investigated through the diffusion experiments of piperazine (PIP) and interfacial tension tests. The incorporated micelles effectively lower the interfacial tension, promote the diffusion of PIP and accelerate the IP reaction, resulting in a denser and thinner PA layer. Collectively, these findings demonstrate that TFN membranes with micelles exhibit increased roughness, enhanced hydrophilicity, superior rejection to divalent salts, and better acid-base resistance, highlighting their potential applications in the design of TFN membranes.

Functionalizing the surface of polyetherimide (PEI)-based cross-linked separator by introducing the polyamide layer through interfacial polymerization and adding boric acid as electrolyte additive for boosted performance in lithium‑oxygen battery

Lithium‑oxygen battery is a very promising energy storage device for its ultrahigh specific capacity. However, due to the undecomposable insulating oxidation species accumulated on the cathode and the safety issues caused by dendrite penetration, the cycling performance of lithium‑oxygen battery is seriously restricted. Herein, through interfacial polymerization (IP) method, a polyetherimide (PEI)-based separator with dense polyamide thin layer was prepared. And the PEI-based separator is cross-linked with Polyethylene polyamines (PEPA) and undergoes 1,3,5-benzenetricarbonyl chloride (TMC) amidation. According to the SEM result, the obtained polyamide layer is well cross-linked with the PEI-based separator and at the same time it owns a dense micro-pore structure, which ensures a battery structure stability and a good electrochemical performance of the separator. Moreover, the increased IP layer amidated by TMC can not only greatly increase the ionic conductivity of the polyamide/polyetherimide (P/PEI) cross-linked separator to 1.0 mS cm−1, but also significantly decrease the interfacial impedance between the PEI and the electrode. With all these merits, the battery assembled with the representative P/PEI2 separator shows boosted cycling performance of over 90 cycles at a capacity of 1000 mAhg−1. Besides, the electrophilic boric acid was introduced to reduce the interaction between anions and cations, resulting in effectively promoted transport efficiency of lithium ions and the cycling life of the battery can be even prolonged to 108 cycles at a capacity of 1000 mAhg−1.

Low temperature regulated reverse interfacial polymerization for fabricating thin film composite membranes based on nanofibrous substrates

In this study, a novel thin film nanofibrous composite (TFNC) nanofiltration (NF) membranes comprised of polyacrylonitrile (PAN) nanofibrous supporting layer and polyamide (PA) compact separating layer was constructed by low-temperature-controlled reverse interfacial polymerization (LTIP-R) at − 5 °C. The strategy for lowering the temperature of organic phase solution played a crucial role in forming a dense and thin PA layer on the PAN nanofibrous substrate with submicron pores. The results revealed that the reduced evaporation rate of organic phase at low temperature was contributed to maintaining a complete and uniform interface for the following reverse IP process, effectively overcoming shortcomings of surface incompleteness and easy infiltration of PA barrier layer. Owing to the reduced thickness and the enhanced wholeness of the PA separating layer via LTIP-R, the optimized TFNC membranes exhibited NF performance with great rejection of divalent salt ions (98.2%) and an improved permeation (13.3 L‧m−2‧h−1‧bar−1). This work would provide an efficient and facile method to fabricate high performance NF membranes for practical applications.

Regulation of interfacial polymerization by organic base for high-permselective nanofiltration

In the synthesis of the polyamide nanofiltration (NF) membrane, the hydrogen chloride is a by-product generated at the organic interface from interfacial polymerization, which reduces the reactivity of amine monomers due to protonation. Herein, a strategy of addition of an organic base in the organic phase to neutralize the H+ was reported. The performances of the membranes produced using three organic bases with different chain lengths were explored. The results showed that the organic base neutralized the H+ and promoted the rate of interfacial condensation reaction, which facilitated the formation of a dense and thin polyamide layer. Moreover, compared to control membrane, the membrane modified by organic base exhibited higher water permeance without sacrificing salt rejection. Higher diffusion rate of HCl through PES substrate compared to NF membrane indicated that HCl diffusion was mainly affected by the resistance of polyamide layer. Molecular simulations demonstrated that triethylamine (TEA) has lower energy barrier of neutralization and higher reaction heat in comparison with tripropylamine and N, N-diisopropylethylamine. The TEA modified membrane thereby displayed a permeance up to 24.3 L h−1 m−2 bar−1 and Na2SO4 rejection of 98.8 %. This work provided a promising strategy for the regulation of interfacial polymerization in achieving high-permselective nanofiltration.

Design of thin-film nanocomposite membranes via synchronizing interfacial coordination and polymerization reactions for organic solvent nanofiltration

Thin-film nanocomposite (TFN) membranes have received immense research interest due to their high permeability and high selectivity in organic solvent nanofiltration (OSN). Herein, TFN membranes were fabricated by synchronizing interfacial coordination and polymerization reactions occurring at an ionic liquid/water interface. The one-pot interfacial reactions led to the simultaneous formation of Fe-MeIm nanofillers and polyamide thin layers with uniform dispersion and good compatibility. The resultant ternary membranes were denoted as Fe-MeIm/PA/PMIA, wherein the Fe-MeIm nanofillers were well-encapsulated in the ultrathin PA selective layer and both of them were located on top of the solvent-resistant PMIA substrate. The morphologies, microstructure, physicochemical properties, and OSN performance of the resultant TFN and traditional TFC membranes were systematically studied and compared. Moreover, the effects of the concentrations and ratios of reagents during the one-pot interfacial reactions were also elucidated. The optimal TFN membrane showed 5 times higher permeance than the TFC membrane without nanofillers while maintaining a high rejection for Congo red/ethanol separation. Moreover, it also showed good stability in various solvents and long-term stability and remarkably improved mechanical properties. This work provides a novel and time-saving fabrication strategy for TFN membranes for OSN application.

Innovative construction of nano-wrinkled polyamide membranes using covalent organic framework nanoflowers for efficient desalination and antibiotic removal

In recent years, the scientific community has identified the intriguing potential of polyamide (PA) nanofiltration (NF) membranes with nano-wrinkled structures, promising to transcend the longstanding permeability-selectivity trade-off inherent in conventional membranes. The present study advances this frontier by masterfully employing covalent organic framework (COF) nanoflowers, meticulously constructed on substrate surfaces using a sophisticated layer-by-layer self-assembly technique. This innovation mediates the interfacial polymerization (IP) process, integral to PA NF membrane fabrication. Through rigorous analysis employing scanning electron microscopy and atomic force microscopy, the derived PA membrane was found to exhibit a distinctive nano-wrinkled morphology. Remarkably, this novel structure yielded a pure water permeance nearly threefold that of control membranes with conventional nodular PA layers. This enhancement is attributed to a synergistic combination of factors that includes increased surface hydrophilicity, greater surface area, thinner PA layer, and an optimized water transport pathway. Furthermore, this membrane demonstrated an impressive 98.7 % Na2SO4 rejection rate, greater than 96.4 % rejections for four critical antibiotics, and commendable stability in flux with superior anti-fouling characteristics. These groundbreaking insights open new avenues for the development of high-performance nano-wrinkled PA membranes, with far-reaching implications for various environmental applications.

Thin film composite membrane with improved permeance for reverse osmosis and organic solvent reverse osmosis

Reverse osmosis (RO) is a widely used pressure-driven membrane process for desalination. Advancements in membrane materials have driven RO technologies' development and widespread application. Thin-film composite (TFC) membranes of a thin polyamide (PA) layer, porous substrate, and nonwoven fabric support are considered the gold standard in desalination technology. These membranes exhibited excellent separation performance and mechanical strength. Recently, TFC membranes with PA layers have been successfully employed in organic solvent reverse osmosis (OSRO) to differentiate organic liquids molecularly. Developing TFC membranes with improved solvent resistance and permeance is required to expand the applications of TFC membranes beyond solvent-solute systems. This study explored polyketone (PK) membranes as porous substrates in TFC membranes for general reverse osmosis processes. PK membranes offer excellent solvent resistance and are easier to prepare than other membranes. Furthermore, a surface modification approach was proposed to enhance the interfacial polymerization (IP) of the polyamide layer on both PK and polysulfone (PSf) substrates, resulting in improved TFC membranes with enhanced water permeance for RO and increased organic liquid permeance for OSRO while maintaining permselectivity. These findings highlight surface chemistry's significance in controlling crumpled PA layers' formation, ultimately improving the filtration efficiency for general RO applications. This study provides an example of the design of composite structures of TFC membranes for broader RO applications.

EMT-NH2 zeolite interlayer induces the formation of high-performance polyamide membrane

Conventional nanofiltration (NF) thin-film composite (TFC) membranes are strongly restricted by the trade-off between their water permeance and selectivity as well as the poor structural stability for desalination and wastewater treatment. Herein, we report an interlayer-based thin-film composite (i-TFC) NF membrane with high performance using amino-functionalized EMT zeolite (EMT-NH2) nanocrystals as the interlayer. By adjusting the distribution density of EMT-NH2 on the substrate, a thin and dense polyamide (PA) layer with heterogeneity multi-level morphology (nanosized nodules and nanoscale stripes) can be formed and regulated. The EMT-NH2 zeolite nanocrystals with numerous hydrophilic groups (hydroxy and amino groups) and internal cavities can provide an additional priority water channel, increase the amine monomer storage on the substrate, and slow down the diffusion of amine monomer, thereby leading to the construction of a dense PA layer with high performance. As a result, the i-TFC-15 membrane depicted a water permeability of 13.82 ± 0.47 L m-2h−1⋅bar−1 (2.5 times that of the controlled one), while maintaining an excellent retention ability for divalent salts (98.55% for Na2SO4, 98.42% for MgSO4 and 97.40% for MgCl2). Additionally, the rigid hydrophilic interlayer containing zeolite nanocrystals endowed the i-TFC-15 membrane with excellent pressure resistance (up to 2.4 MPa), long-term operating stability, and antifouling propensity (flux-recovery ratio, 90.1%). This work provides an approach for fabricating a novel high-performance NF membrane and deepens our understanding of the role of porous interlayer affecting the formation of the PA layer.

High performance forward osmosis membrane with ultrathin hydrophobic nanofibrous interlayer

The novel thin film composite (TFC) forward osmosis (FO) membrane with electrospinning nanofibers as support layer can alleviate internal concentration polarization (ICP). While the macropores of the nanofiber support layer cause defects in the polyamide (PA) layer. Therefore, hydrophobic polyvinylidene fluoride (PVDF) fine nanofibers were used as an interlayer to modulate the process of interfacial polymerization (IP) in this study. The results showed that the introduction of the interlayer improved the hydrophobicity of the support layer for achieving uniform, thin and defect-free selective polyamide (PA) layer. The water flux of TFC-PVDF was 58.26 LMH in the FO mode of 2 M NaCl, which was two times higher than that of the unmodified FO membrane. Lower reverse salt flux (4.91 gMH) and structural parameter (179.43 μm) alleviated the ICP. In addition, TFC-PVDF membrane showed good anti-fouling performance for SA (flux recovery ratio of 93.97%) due to high hydrophilicity, low zeta potential and low roughness. This study provides an easy and promising method to prepare defect-free PA selective layer on the macropores nanofiber support layer. The novel FO membrane shows high desalination performance and anti-fouling properties.

Nanofiltration membrane with asymmetric polyamide dual-layer through interfacial polymerization for enhanced separation performance

Thickness reduction of polyamide separation layer played an important role in permeability enhancement of thin film composite (TFC) nanofiltration membrane. However, the practical application of TFC nanofiltration membrane with ultrathin polyamide layer is still a great challenge. Herein, we proposed a strategy for preparing nanofiltration membrane with asymmetric polyamide dual-layer through interfacial polymerization. The top polyamide layer is thin, smooth and dense. The bottom polyamide layer is relatively thick, rough and porous. The thin and dense top polyamide layer enabled membrane with relatively high water permeability (18.5 ± 1 L m−2 h−1 bar−1) and Na2SO4 rejection (97.2 ± 0.8 %) performance. The thick and porous bottom polyamide layer guaranteed membrane stability. This study offers a promising strategy for polyamide composite membrane fabrication with enhanced separation performance.

Innovative role of polyvinylpyrrolidone in tailoring polyamide layer for high-performance nanofiltration membranes

While being the preferred choice in the desalination industry, polyamide (PA) nanofiltration (NF) membranes still suffer from the permeability-selectivity trade-off challenge. This study successfully fabricated a high-performing PA NF membrane by regulating the role of polyvinylpyrrolidone (PVP) in the PA layer, which is contrary to the traditional view of PVP as a simple pore-forming agent. The study demonstrated that PVP can partially persist in the polyethersulfone (PES) substrate and impact the interfacial polymerization (IP) process, resulting in a thinner PA layer with a higher cross-linking degree and a more uniform pore structure compared to a PA layer formed on a control substrate without PVP. Molecular dynamic simulations revealed that the van der Waals force between PVP and piperazine (PIP) slowed down the diffusion of PIP at the PVP-PES substrate surface, facilitating the formation of a PA layer with a uniform pore size distribution and reduced thickness. By adjusting the concentrations of PVP in the dope solution and PIP during interfacial polymerization, a PA membrane with pure water permeability of 30.2 ± 0.9 L·m−2·h−1·bar−1 and a Na2SO4 rejection rate of 97.7 ± 0.1 % was obtained. This study provides new insights and presents a novel approach to tailoring the PA layer structure of NF membranes.

In situ assembly of graphitic carbon nitride/polypyrrole in a thin-film nanocomposite membrane with highly enhanced permeability and durability

Although thin-film nanocomposite (TFN) membranes have been proposed as a competitive approach for improved reverse osmosis performance within the last decade, their intrinsically poor organic-inorganic interfacial compatibility and low durability still hinder further upscaling. In this study, a new in situ assembly strategy is proposed to solve this dilemma by using polypyrrole (PPy) to build a bridge between polyamide matrix and nanomaterial (graphitic carbon nitride, g-C3N4) and further fabricate g-C3N4/PPy-incorporated TFN membrane. The synthesized g-C3N4/PPy nanocomposites are hybridized into the interfacial polymerization process, which endows the TFN membrane with a smaller “ridge-valley”, higher hydrophilic and thinner polyamide layer. With 0.005 wt% of g-C3N4/PPy, the water permeability of TFN membrane is increased to 377 % (4.0 L·m−2·h−1·bar−1), while keeping a similar NaCl rejection (99.1 %) to pure polyamide membrane. Importantly, the resulting TFN membrane exhibits high chlorine resistance in acidic, neutral and alkaline environments. Moreover, the TFN membrane has superior antifouling performance for organic, inorganic and mixed organic-inorganic foulants, which is of vital importance for the long service life of TFN membranes. This study offers a facile avenue to solve the application needs of advanced TFN membranes for efficient desalination with stable high-quality water.

Polyamide/UiO-66-NH2 nanocomposite membranes by polyphenol interfacial engineering for molybdenum(VI) removal

Introducing porous nanomaterials into polyamide thin layer has been identified to be a desirable approach to improve separation performance of nanofiltration membrane. In this work, a novel sandwich-like thin-film nanocomposite membrane (TFNi) featuring an interlayer was prepared. The interlayer, composed of porous UiO-66-NH2 metal organic framework and adhesive tannic acid (TA), was formed between amphiphilic poly(vinylidene fluoride)-grafting-poly(acrylic acid) substrate and polyamide top layer by self-assembly and interfacial polymerization. TFNis were characterized by FT-IR, SEM, AFM, XRD, water contact angle, zeta potential, molecular weight cut off, flux and ion retention. Results showed that the introduction of interlayer could enhance efficiently membrane flux and ion removal. TFNi-3 membrane constructed by an optimized stepwise deposition, had a high permeate flux (65.4 L m−2 h−1), and good removal efficiencies towards single molybdenum(VI) (Mo(VI)) (98.1 %), single salt (30.8 % for NaCl, 96.5 % for Na2SO4) and mixed solutions (37.0 % for NaCl-Mo(VI), 93.6 % for Na2SO4-Mo(VI), 76.1 % for NaCl-Na2SO4-Mo(VI)). The adsorption experiment and density functional theory (DFT) calculations were also carried out. Amino and zirconium oxygen clusters in UiO-66-NH2 and polyphenol in TA were main adsorption sites. In addition, TFNi-3 had the favorable stability. Perhaps it has a potential application for desalination and Mo(VI) removal from wastewaters.

Preparation of thin-film nanocomposite membrane with alkali-treated nanozeolite to improve the dehydration performance of alcohol solution

BackgroundThin-film nanocomposite (TFN) membrane separates water from alcohols effectively. However, during fabrication of TFN membrane, the dispersion of inorganic nanoparticle in the solvent media limits its used. MethodsNanozeolite, a natural inorganic particle, was modified through alkaline treatment using NaOH or NaHCO3. Both alkaline indeed improved the dispersion of nanozeolite in trimesoyl chloride (TMC)/n-hexane solution. TFN membrane had been prepared through interfacial polymerization of diethylenetriamine (DETA) and TMC, forming a thin selective polyamide layer on top of hydrolyzed polyacrylonitrile (mPAN) support. Significant findingsThe pore size of the nanozeolite was also enlarged due to the etching by the alkaline. Nanozeolite modified with NaHCO3 was dispersed well in the membrane surface, thus increasing its membrane efficiency. At the optimum preparation condition, 0.2 wt% NZ-NaHCO3 treated using 1 M NaHCO3, the TFNNZ-NaHCO3 exhibited the highest flux of 1,869 g∙m2∙h−1 with 99% water concentration in permeate. Furthermore, the modified membrane had a stable performance for long-term, as well as at different operating temperature and alcohol concentration in the feed. Therefore, the right concentration and type of alkaline could improve the property of nanozeolite for preparing high pervaporation membrane.

Preparation of highly permeable and selective nanofiltration membranes with antifouling properties by introducing the capsaicin derivative into polyamide thin selective layer by bidirectional interfacial polymerization

A novel thin film composite (TFC) nanofiltration (NF) membrane was prepared by introducing the capsaicin derivative AMTHBA into polyamide (PA) layer by bidirectional interfacial polymerization. Ultrathin, smooth and defect-free PA layers can be prepared by bidirectional interface polymerization. Meanwhile, the surface properties of NF membranes were precisely regulated by adjusting the concentration of AMTHBA in an aqueous solution. As a result, the AMTHBA-PAR/PAF/PS membrane displayed superior permeance owing to its hydrophilic and negatively charged surface. The optimized NF membrane exhibited an ultrahigh permeance of 128.95 L m−2 h−1 (almost two-fold higher permeance than that of the nanofiltration membrane prepared by traditional interfacial polymerization), together with a steady efficiency above 98.43% for rejection of Na2SO4. In addition, the AMTHBA-PAR/PAF/PS membrane exhibited excellent antifouling performance and therefore has broad application prospects in the field of water treatment.