Monomer In Aqueous Solution Research Articles

Affecting the Electropolymerization of Aniline with Permanent Magnets

As portable electronics become more ubiquitous, the demand for different electrochemical energy storage (EES) systems grows. Conductive-polymer-based supercapacitors are an emerging type of EES device promising for their rapid charging and discharging, and among these, polyaniline (PANI) is favored for the ability to deposit it electrochemically from aqueous solutions of monomer. Despite this advantage, supercapacitors fabricated with PANI exhibit poor energy density and cyclability compared to other supercapacitors. In this work, it is shown how a permanent magnet can be applied to affect this electropolymerization, increasing the capacitance of the resultant polymer film by over 70% and increasing its cyclability more than ten-fold. The use of a permanent magnet allows enhancement of the process without the use of any chemical additives or additional energy input, such as from heating, excessive overpotentials, or mechanical stirring. The magnet influences the electropolymerization primarily through the magnetohydrodynamic (MHD) effect, but this work shows that the effect of the magnetic field exceeds that of mechanical stirring. Furthermore, evidence is presented that the influence from the magnet goes beyond forced convection from the MHD effect.

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.

Hollow fiber thin-film composite membrane regulated by macrocyclic polyamine molecules for high performance organic solvent nanofiltration

Organic solvent nanofiltration (OSN) technology has the potential to separate and purify organic solvents in high efficiency. The self-supporting structure and ease scaling-up merit of hollow fiber (HF) type membrane make it an attractive option for OSN application. Nevertheless, low solvent permeance is one of technical limitation in conventional HF OSN membranes due to their excessively dense separation layer and limited free volume. Herein, we propose a straightforward methodology to fabricate HF thin-film composite (TFC) OSN membranes having exceptional solvent permeance and solute rejection. This methodology is conducted through the incorporation of macrocyclic molecules, 1,4,7,10-tetraazacyclododecane (Cyclen), into the aqueous monomer solution of m-Phenylenediamine (MPD) during the interfacial polymerization to modulate the separation layer. In this way, the average pore size of the separation layer could be precisely enlarged and narrowed on a sub-nanometer scale. Consequently, the Cyclen-modulated HF TFC OSN membrane exhibits excellent separation performance, with a pure methanol permeance of 76.7 L m−2 h−1 MPa−1 and a pure ethanol permeance of 26.5 L m−2 h−1 MPa−1, which is nearly 60 % increase compared with the baseline TFC membrane, while the Rhodamine B (RDB) rejection only shows a neglectable decrease from 99.7 % to 99.6 % at optimal fabrication conditions. Furthermore, the optimal membrane exhibits remarkable solvent resistance, withstanding a 35 d immersion in N, N-dimethylformamide (DMF) at room temperature without a significant decline in RDB rejection. Additionally, the optimal membrane shows higher than 99 % rejection for Rifampicin (823 Da), which is considerable potential for applications in the separation and recovery of pharmaceuticals. In summary, incorporating macrocyclic polyamine Cyclen into the polyamide layer is a viable method for regulating the physical structure and strengthening the performance of HF OSN membrane.

Hydrogen bond‐reinforced double‐network hydrogels with enhanced mechanical strength: Preparation, characterization and swelling behavior

AbstractRecently, double network (DN) gels with dynamic non‐covalent interaction such as hydrogen bonds has drawn much attention as an innovative material having both high water content and high mechanical strength. Research efforts have identified DN gels as a promising class of materials due to their unique network architecture. These gels comprise two interpenetrating networks formed by different types of polymer. Herein, we report a tough DN hydrogel with high mechanical strength and high swelling ability. The DN gel is synthesized via a two‐step network formation. The first network gel was synthesized via frontal polymerization. Then, the first gel is immersed in an aqueous solution of a second monomer and carrying out a second polymerization in the presence of first network. The spectroscopic analysis and thermal behavior with differential scanning calorimeter measurements corroborated the existence of hydrogen bonds. The mechanical test and microscopic morphology were further explored to explain the strength and high imbibing characteristics. We expect that this facile strategy may explore a dynamic and tunable hydrogel to expand its potential applications in biomedical field.

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.

Ternary-coordination-regulated polyamide nanofiltration membranes for Li+/Mg2+ separation

Thin-film composite (TFC) membranes prepared by the interfacial polymerization (IP) of amines and trimesoyl chloride (TMC) have been widely utilized for Li+/Mg2+ separation from salt-lake brine. The relatively high lithium rejection hinders the achievement of high lithium extraction efficiency. In this study, a polyphenol-metal-assisted method was designed to regulate the structure of polyethylenimine (PEI)-based polyamide nanofiltration (NF) membranes. Tannic acid (TA) was first deposited onto the substrate, followed by the impregnation of the Cu2+ ions-incorporated aqueous PEI monomer solution to establish ternary interactions among PEI, TA, and Cu2+ ions. Based on the synergistic effect of ternary interactions, the resultant PA-TA-Cu membrane possesses ultrathin thickness (≈11 nm), high positive charge, and relatively loose structure. It exhibited a high MgCl2 rejection (95.9 %) and a low LiCl rejection (17.1 %), with a pure water permanence of 4.87 L m−2 h−1 bar−1. Furthermore, the NF membrane exhibits a high Li+/Mg2+ separation factor (26.5) and excellent long-term stability. This study provides an efficient strategy for fabricating an excellent NF membrane for lithium extraction from salt-lake brines.

New insights into pure zwitterionic hydrogels with high strength and high toughness.

Zwitterionic hydrogels are electrically neutral materials with both cationic and anionic groups that impart excellent anti-fouling properties and ion channel orientations. However, pure zwitterionic hydrogels generally exhibit low strength and toughness. In this study, it has been discovered that polymerizable zwitterionic monomers in aqueous solution exhibit a unique liquid-liquid phase separation phenomenon at a high monomer concentration of ≥50 wt%, resulting in pure and commercial zwitterionic hydrogels with high compressive strength (6.5 MPa) and high toughness (2.12 kJ m-2). This phase separation and the corresponding aggregations might be caused by strong dipole-dipole interactions among residual zwitterionic monomers under the lack of free-water condition. The synergistic effect of liquid-liquid phase separation and polymer entanglement enhances the mechanical strength, toughness, self-recovery, and anti-freezing properties of pure polyzwitterionic hydrogels. Moreover, the high fracture energy of highly elongated yet tough polyzwitterionic hydrogels facilitates the development of high crack propagation resistance, which supports an expanded role in tissue engineering, soft flexible devices, and electronics applications with improved durability. A wide range of applications for the proposed polyzwitterionic hydrogels is demonstrated by the development and testing of a strain sensor and a triboelectric nanogenerator device. Our findings provide novel insights into the network structure of pure polyzwitterionic hydrogels.

Development of hydrogen bonding stabilized conjugated carbonaceous polyaryl organic solvent nanofiltration membranes for molecular sieving

This study focuses on a green approach used for the fabrication of a thin film composite organic solvent nanofiltration membrane using aqueous solutions of a pyrrole monomer and iron chloride.

Unveiling the impact of monomer reactivity on the morphology and functionality of thin-film composite membranes

This study delves into the impact of monomer selection and reaction pH on the morphology and performance of thin-film composite (TFC) membranes. The research provides an understanding of how polyamide (PA), polyester amide (PEA), and polyester (PE) membranes can be tailored for specific applications, employing piperazine (PIP) and glucose as monomers in aqueous solution alongside trimesoyl chloride (TMC) as a monomer in an organic solution. PEA-based membranes containing glucose demonstrated several notable improvements, including a reduced contact angle of 60 degrees, a smoother surface, and a more negative zeta potential. These enhancements underscore their increased hydrophilicity, decreased susceptibility to fouling, and heightened surface charge. Controlling pH during fabrication significantly changed the membrane surface charge, hydrophilicity, water flux, and rejection rate. At pH 11, the PA membrane excelled in rejection performance (99.5% Na2SO4, 32% NaCl, and 97.8% methyl orange) with a trade-off in lower water flux (56 LMH). Conversely, the PE membrane achieved the highest water flux (173 LMH) but lower rejection (58% Na2SO4, 10% NaCl, and 97% methyl orange). The PEA membrane offered notable water flux (82.5 LMH) and high rejection for methyl orange (99.3%) and Na2SO4 (99.2%). Increasing the pH reduced permeation rates but enhanced rejection, especially for NaCl. The PE and PEA membranes exhibited remarkable antifouling properties, boasting a flux recovery ratio compared to the PA membrane. This study highlights the pivotal role of monomer selection and pH control in TFC membrane performance, offering prospects for innovative design and optimization in water treatment membrane technology.

One-Pot Formation of Pairing Proto-RNA Nucleotides and Their Supramolecular Assemblies.

Most contemporary theories for the chemical origins of life include the prebiotic synthesis of informational polymers, including strong interpretations of the RNA World hypothesis. Existing challenges to the prebiotic emergence of RNA have encouraged exploration of the possibility that RNA was preceded by an ancestral informational polymer, or proto-RNA, that formed more easily on the early Earth. We have proposed that the proto-nucleobases of proto-RNA would have readily formed glycosides with ribose and that these proto-nucleosides would have formed base pairs as monomers in aqueous solution, two properties not exhibited by the extant nucleosides or nucleotides. Here we demonstrate that putative proto-nucleotides of the model proto-nucleobases barbituric acid and melamine can be formed in the same one-pot reaction with ribose-5-phosphate. Additionally, the proto-nucleotides formed in these reactions spontaneously form assemblies that are consistent with the presence of Watson-Crick-like base pairs. Together, these results provide further support for the possibility that heterocycles closely related to the extant bases of RNA facilitated the prebiotic emergence of RNA-like molecules, which were eventually replaced by RNA over the course of chemical and biological evolution.

Poly(bis(2,2′-bipyridine) hydroxy Copper(II) iodide modified glassy carbon electrode for electrochemical determination of chloroquine in pharmaceuticals and biological samples

A new electrochemical sensor, poly(bis(2,2′-bipyridine)hydroxycopper(II) iodide modified glassy carbon electrode (poly([Cu(Bip)2OH]I)/GCE), was prepared by electropolymerization of bis(2,2′-bipyridine)chlorocopper(II) iodide ([Cu(Bip)2Cl]I) on glassy carbon electrode (GCE) for voltammetric determination of chloroquine (CQ). The synthesized complex (bis(2,2′-bipyridine)chlorocopper(II) iodide) was characterized using UV–Vis, CHN elemental analysis, atomic absorption spectroscopy (AAS), electrolytic conductivity, melting point and Fourier transform infrared spectroscopy (FT-IR) were used to characterize and confirm the synthesis of the desired complex (bis(2,2′-bipyridine)chlorocopper(II) iodide). The Uv-Vis, FTIR and electrochemical data of the synthesized polymer supports the replacement of chloro ligand by hydroxyl ligand during electropolymerization of the monomer in aqueous solution. The fabricated electrode (poly([Cu(Bip)2OH]I)/GCE) was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The voltammetric behavior of CQ was examined using CV and square wave voltammetry (SWV). Compared to the bare GCE, poly(Bip)/GCE, and Cu/GCE, the current signal of CQ was significantly enhanced at poly([Cu(Bip)2OH]I)/GCE, which demonstrates excellent electrocatalytic behavior of poly([Cu(Bip)2OH]I)/GCE towards electrochemical oxidation of CQ. Under the optimum experimental conditions, the SWV current signal of poly([Cu(Bip)2OH]I)/GCE offered linearity on the concentration range of CQ between 0.5 and 250 μM with LOD and LOQ values of 4.22 ×10−2 and 1.4 × 10−1 μM, respectively. In the presence of possible interfering substances including glucose, paracetamol, adenine and guanine, the voltammetric determination of CQ was also considered, and their interventions were found to be insignificant, which evidenced the selectivity of the introduced electrode. The analytical application of the established sensor was successfully applied in the determination of CQ in pharmaceuticals, milk, serum, and urine samples. The detected amount of CQ in the tablet samples was in the range between 100.5 and 110.2% with RSD of 1.5 and 1.87%, respectively. The spiked recovery results in pharmaceuticals, milk, serum, and urine biological samples were in the range of 100.5 to 110.2%, 97.13 to 98.12, 103.7 to 103.6% and 95.50 to 97.05%, respectively. These results confirm that the developed method exhibits high applicability for electrochemical determination of CQ in various real samples.

The Effect of Mixed Ligands on the Polymerization Rate of SET-LRP in Aqueous Solution

Abstract The mixed-ligand effect is investigated in single electron transfer-living radical polymerization (SET-LRP) of OEOMA in aqueous solution for the first time. Mediated by equimolar tris(2-aminoethyl)amine (TREN) and tris(dimethylaminoethyl)amine (Me6-TREN), SET-LRP exhibits the highest polymerization rate while maintaining living characteristics. The higher concentration of self-assembled micellar particles formed by amphiphilic initiator and monomer in aqueous solution under the influence of mixed ligands may be considered as one of factors for the mixed-ligand effect.

Janus membranes with simultaneous flux enhancement and fouling/wetting resistance prepared by a modified interfacial polymerization process for membrane distillation

Conventional membrane distillation (MD) membranes are hydrophobic and challenged by severe membrane fouling and wetting. Current surface modification strategies for anti-fouling and anti-wetting purposes, usually complex and time-consuming, often compromise the MD flux. Herein, we propose a modified interfacial polymerization (mIP) approach to fabricate Janus membranes with rapid and robust MD performance. In the mIP process, a dry hydrophobic substrate is first immersed in an oil-phase monomer solution and then in contact with an aqueous monomer solution to trigger the mIP reaction. The as-fabricated Janus membrane (e.g., IP2@PTFE) comprised an ultrathin, underwater oleophobic, and defect-free polyamide (PA) layer and a porous polytetrafluoroethylene (PTFE) substrate. Compared with the unmodified PTFE membrane, the vacuum MD flux of the IP2@PTFE membrane held a 177.4 % increase when tackling a NaCl solution (3.5 wt%) at 60 °C. When the NaCl solution contained sodium dodecyl sulfate (SDS) surfactant or/and mineral oil, the IP2@PTFE membrane exhibited fouling and wetting resistance simultaneously; conversely, severe oil fouling and quick SDS-induced wetting occurred on the pristine PTFE membrane. The mIP process does not require any pretreatment of the hydrophobic substrate, so it is facile and scalable. We believe that this study will facilitate the design of robust MD membranes.

Synthesis and molecular dynamics simulation of amphoteric hydrophobically associating polymer

To address the practical issues of poor temperature and salt tolerance of polymers, a new amphoteric monomer (E)-N-(docos-13-enoyl)-N-methylglycine named CQ was developed. The polymer CQMP was synthesized by acrylamide (AM) and CQ as an associative monomer and sodium p-styrene sulfonate (SSS) as a functional monomer in aqueous solution. The structure of the products was confirmed by FTIR, 1H NMR and TGA, while the micro-morphology of the polymer was observed by SEM. Taking HAPAM as a control, the properties of polymer in aqueous solution were studied as a function of salinity, shear rate, temperature, and polymer concentration. The oil displacement performance was also evaluated in detail. Additionally, the surface tension (SFT) and interfacial tension (IFT) of CQMP solution were measured. The critical micelle concentration (CMC) values of CQMP in aqueous solution and in NaCl solution are 2.13 g·L-1 and 1.79 g·L-1,respectively. The copolymer can reduce the interfacial tension between water and crude oil from Changqing Oilfield, with an IFT value of about 15.96 mN·m−1. The results indicate that the critical association concentration (CAC) is approximately 600 mg·L-1, and the polymer exhibits good salt tolerance and oil flooding performance. Furthermore, molecular dynamics simulation demonstrated that CQ can enhance intermolecular interactions while maintaining the same hydrophobic chain content, thereby reinforcing the polymer’s resistance temperature and salt. The laboratory flooding experiment showed that the enhance oil recovery of CQMP with 0.5 PV 3000 mg·L-1 was 12.23 % greater than that of HAPAM, which is promising for multiple applications in complex oil fields.

Thin film nanocomposite polyamide membrane doped with amino-functionalized graphene quantum dots for organic solvent nanofiltration

Thin film nanocomposite (TFN) organic solvent nanofiltration (OSN) membrane with improved separation performance was fabricated via interfacial polymerization reaction between amine-functionalized graphene quantum dots (af-GQDs) doped aqueous monomer solution of m-phenylenediamine (MPD) and n-hexane solution containing trimesoyl chloride (TMC) monomer. We emphasize the employment of extra-low content for both af-GQDs and MPD, so that we could maximize the function of these nanomaterials and eliminate their aggregation at the same time. The af-GQDs nanomaterials could regulate the interfacial polymerization process and could be strongly anchored in the polyamide film via covalent bonding, hence could prevent their loss while providing more channels for faster solvent penetration. As a result, the optimized OSN membrane, TFN-50, shows a super-smooth surface, with a surface roughness as low as 4.3 ± 0.2 nm, and excellent pure solvent permeances which reach 135.8, 112.7, and 69.8 L m−2 h−1 MPa−1 for methanol, DMF and ethanol, respectively, as well as a very high Rhodamine B (RDB, 479 Da) rejection of up to 99.2%, and an ethanol permeance of 61.4 L m−2 h−1 MPa−1. Furthermore, the TFN-50 OSN membrane still shows excellent filtration performance after being submerged in DMF for 336 h or continuous crossflow filtration with Rose bengal (RB, 1017 Da)/DMF solution for 136 h, demonstrating its excellent solvent resistance.

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

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

Cellulose nanocrystal addition in thin film nanocomposite membranes: Which monomer solution is preferred?

AbstractCellulose nanocrystals (CNCs) are biodegradable nanoparticles with a high aspect ratio and abundant surface hydroxyl groups resulting in negatively charged hydrophilic surfaces that make them an ideal candidate to be incorporated in thin‐film nanocomposite (TFN) membranes. In this study, we modified the CNCs via acetylation (ACNCs) to reduce their hydrophilicity and via reaction with L‐cysteine (CysCNCs) to impart them with functionality that promoted their interaction with the trimesoyl chloride organic monomer used in the preparation of the poly(amide) layer of the TFN membranes. These modifications allowed us to question in which monomer solution the nanoparticles should be dispersed. Addition of the unmodified CNCs in either the aqueous or organic monomer solution showed little difference in membrane performance. However, the addition of either the ACNCs or the CysCNCs to the organic monomer solution led to a significant increase in membrane performance in reverse osmosis (RO) and nanofiltration (NF) systems compared to their addition to the aqueous monomer solution. In addition, the CysCNCs exhibited performance very near the upper‐bound line for RO and NF.

Growth of single-crystal imine-linked covalent organic frameworks using amphiphilic amino-acid derivatives in water

A core feature of covalent organic frameworks (COFs) is crystallinity, but current crystallization processes rely substantially on trial and error, chemical intuition and large-scale screening, which typically require harsh conditions and low levels of supersaturation, hampering the controlled synthesis of single-crystal COFs, particularly on large scales. Here we report a strategy to produce single-crystal imine-linked COFs in aqueous solutions under ambient conditions using amphiphilic amino-acid derivatives with long hydrophobic chains. We propose that these amphiphilic molecules self-assemble into micelles that serve as dynamic barriers to separate monomers in aqueous solution (nodes) and hydrophobic compartments of the micelles (linkers), thereby regulating the polymerization and crystallization processes. Disordered polyimines were obtained in the micelle, which were then converted into crystals in a step-by-step fashion. Five different three-dimensional COFs and a two-dimensional COF were obtained as single crystals on the gram scale, with yields of 92% and above.

Silicification-interlayered nanofiber substrates regulated crumpled ultrathin polyamide nanofilms for highly enhanced nanofiltration

Thin-film nanofiber composite (TFNC) membranes have shown great potentials for highly efficient nanofiltration. However, it remains a challenge to construct defect-free ultrathin polyamide nanofilms with designed crumpled structures on polymeric nanofiber substrates via traditional interfacial polymerization (IP) to realize high permeability and selectivity synchronously. Herein, a novel strategy is reported to regulate the polyamide nanofilm by a silicification-interlayered nanofiber substrate with hydrophilic and rugged surface. The silica interlayer could enrich piperazine (PIP) monomers in aqueous solutions and control the releasing towards the interfacial reaction zone, enabling the homogeneous IP reaction and the reduced thickness of PA nanofilms. The silicified nanofiber substrate can also serve as a templating support to crumple the PA nanofilms and thus increase their effective infiltrating area. Furthermore, deep insight has been taken into the intermolecular interactions in the IP system and the fundamental mechanism of the silicification-interlayered nanofiber substrate regulating the IP process via density function theory (DFT) and dissipative particle dynamics (DPD) simulations. The membrane morphologies were observed by SEM and AFM, and chemical structures of membrane surfaces were characterized by FTIR/ATR, XPS and XRD in detail. The hydrophilicity and charged properties of different membrane surfaces were analyzed by water contact angle and Zeta potential tests, respectively. As a result, an ultrathin crumpled PA nanofilm is generated on top of the nanofiber substrate as selective layer, enabling the composite membrane with enhanced water permeability of 19.6 L m−2 h−1 bar−1 (approximately two folds higher than that of the pristine PA membranes) and high Na2SO4 rejection of 96.5%. Meanwhile, the prepared membranes reveal good structural stability not only under different operation pressures but also during long-term filtration processes. This work is believed to provide a facile approach to engineer advanced TFNC membranes with high-efficiency nanofiltration performance.

Improving nanofiltration performance using modified cellulose nanocrystal-based TFN membranes

Heavy metal ions are one of the principal contaminants in industrial wastewater. Their removal in nanofiltration processes using thin-film nanocomposite (TFN) membranes is a promising treatment method. l-cysteine functionalized cellulose nanocrystals (CysCNCs) and acetylated CNCs (ACNCs) were synthesized via an iodine-catalyzed method. The successful modification of CNCs was confirmed using ATR-FTIR and 13C NMR spectroscopy. The modified CNCs were used in the synthesis of TFN membranes. Prior to interfacial polymerization, the CNCs were dispersed into the organic monomer solution (trimesoyl chloride in n-hexane) rather than in the aqueous monomer solution (piperazine), contrary to conventional practice.Membrane performance was assessed for thin film composite (TFC) and CNC, ACNC and CysCNC-TFN membranes. A simultaneous increase in water permeability/salt and heavy metal rejection of ACNC-TFNs and CysCNC-TFNs was observed. In heavy metal removal tests, the CysCNC-TFN0.2 membranes exhibited the highest water permeability (16 L/m2 h bar) compared to the ACNC-TFN0.1 membranes (14.5 L/m2 h bar), the CNC-TFN0.1 membranes (11.5 L/m2 h bar), and the TFC membranes (6 L/m2 h bar). The heavy metal rejections ranged from 89.2 to 98.4% for the copper ions and 87.0–95.2% for the lead ions, in the same order as for the water permeability results. Therefore, the water permeability/selectivity trade-off was overcome. The TFN membrane performance improvements were mainly attributed to both the nanoparticle functionality and their uniform distribution in the polyamide layer via their dispersion in the organic monomer solution.