Boosted Intracavity Aperture in Macrocyclic Amines Enabling Finely Regulated Microporous Membranes.

Finely tuning the pore structure of traditional nanofiltration (NF) membranes is challenging but highly effective for achieving efficient separations. Herein, we propose a concept of using macrocyclic amines (1,4,7-triazacyclononane, 3A; 1,4,7,10-tetraazacyclododecane, 4A1; and 1,4,8,11-tetraazacyclotetradecane, 4A2) with different intra-annular apertures to finely modulate the pore structure of microporous membranes via interfacial polymerization (IP). The boost in the intracavity size of the building blocks results in heightened steric hindrance of these amine monomers, leading to a controlled increase in membrane pore size, as demonstrated by both film characterizations and multiscale simulations. In conjunction with the increased intracavity size, the water permeability follows an augmented trend of 3A-TMC, 4A1-TMC, and 4A2-TMC (TMC: trimesoyl chloride) while exhibiting increased molecular weight cut-offs due to larger free-volume elements and stronger pore interconnectivity. Our proposed macrocyclic amine design strategy provides a guideline for finely regulated microporous membranes with high potential in NF-related applications.

Sodium-Ion Traps in a Two-Dimensional Confined Channel for Effective Water and Ion Selective Transport.

Nanoconfined interlayer channels in two-dimensional (2D) laminates are promising for the construction of novel permselective membranes. Controlling the interlayer spacing and modifying the interlayer chemical microenvironment are effective for high-efficiency separation. However, manipulating ion-diffusion energy barriers in confined channels is challenging, and their role in selective water-ion transport is unclear. This study engineered sodium-ion traps (SITs) in confined graphene oxide (GO) interlayer channels by incorporating N-phenylaza-15-crown-5 (NPCE) to regulate the ion-diffusion energy barriers. Partial reduction of GO enhanced membrane stability and enabled precise adjustment of interlayer spacing, while the addition of NPCE further constricted the free space and entrapped sodium ions by increasing their transport energy barriers. The optimized membrane with NPCE-dominated SITs achieved mono/monovalent-ion efficient sieving (K+/Na+ ≈ 10.2, and Li+/Na+ ≈ 6.7) and rejection of Na2SO4 (∼99.0%) and NaCl (∼90.0%), while maintaining stable performance for >1500 h. The findings provide new insights into manipulating transport energy barriers and modifying other 2D material laminates.

Self-Aggregation Control of Porphyrin for Enhanced Selective Covalent Organic Network Membranes.

Covalent organic networks (CONs) are considered ideal for precise molecular separation compared with traditional polymer membranes because their pores have a sharp molecular weight cut-off and a robust structure. However, challenges remain with regard to tuning pores as a prerequisite for facile membrane fabrication to a defect-free layer. Herein, a highly conjugated amino-porphyrin is used and exploited its tunable stacking behavior to fabricate porphyrin-based polyamide CONs with ordered structures through interfacial polymerization with acyl chlorides. Controlling the self-aggregation behavior of the porphyrin and the conformation of the acyl chlorides can create different covalent networks. Acid-triggered porphyrin protonation offsets stacking to reduce the pore in the network from mesopore to micropore, enabling selective molecule transport. Furthermore, different acyl chloride ligands are used to control the interlayer bonding in CONs. Accordingly, the tailored pore diameters (0.48-0.78 nm) are confirmed by the molecule rejections with performance stability over 25 days of operation, as well as under various conditions. This study leverages porphyrin chemistry and interfacial polymerization to fabricate a defect-free CON layer with a significantly lower molecular weight cut-off (< 330 Da) than previously reported porphyrin-based membranes (>800 Da). This will pave the way for the development of ideal topological membranes.

Side-Chain-Dependent Functional Intercalations in Graphene Oxide Membranes for Selective Water and Ion Transport.

Subnanometer interlayer space in graphene oxide (GO) laminates is desirable for use as permselective membrane nanochannels. Although the facile modification of the local structure of GO enables various nanochannel functionalizations, precisely controlling nanochannel space is still a challenge, and the roles of confined nanochannel chemistry in selective water/ion separation have not been clearly defined. In this study, macrocyclic molecules with consistent basal plane but varying side groups were used to conjunct with GO for modified nanochannels in laminates. We demonstrated the side-group dependence of both the angstrom-precision tunability for channel free space and the energy barrier setting for ion transport, which challenges the permeability-selectivity trade-off with a slightly decreased permeance from 1.1 to 0.9 L m-2 h-1 bar-1 but an increased salt rejection from 85% to 95%. This study provides insights into the functional-group-dependent intercalation modifications of GO laminates for understanding laminate structural control and nanochannel design.

Toxicokinetics and toxic effects of a Chinese PFOS alternative F-53B in adult zebrafish.

6:2 chlorinated polyfluorinated ether sulfonate (F-53B), a Chinese PFOS alternative, has recently been identified in river water, sewage sludge, wildlife and humans, causing great concerns about its potential toxic effects. Here, we report the first investigation of the toxicokinetics and oxidative stress of F-53B in adult zebrafish. Adult male and female zebrafish were exposed to 10 and 100 µg/L of F-53B for 7 days followed by a 5-d depuration period to examine bioaccumulation, distribution, and depuration of F-53B in fish. The results showed that F-53B was readily accumulated in fish tissues with log BCF values of 2.36-3.65, but was eliminated slowly (t1/2 = 152.4-358.5 h). F-53B accumulation was greater in males than in females and the concentration in tissues decreased in the following order: gonad ≈ liver ≫ gill ≫ brain in females and liver ≈ gill ≫ gonad ≫ brain in males, showing sex- and tissue- specific accumulation of F-53B in fish. After chronic exposure to F-53B for 28 days, a significant dose-dependent increase in histopathological changes in the liver were mainly manifested by vacuolation. Furthermore, F-53B also significantly reduced the enzyme activity (or content) of most of the measured oxidative stress-related markers (e.g., SOD, CAT and MDA) except for an increase in GSH-Px activity, indicating that oxidative stress was induced in zebrafish after treatment with F-53B. The results of this study provide important information on the toxicokinetics and toxic effects of F-53B, which will contribute to the ecological risk assessments of F-53B released into surface waters.

Parameterization of a mesoscopic model for the self-assembly of linear sodium alkyl sulfates.

A systematic approach to develop mesoscopic models for a series of linear anionic surfactants (CH3(CH2)n - 1OSO3Na, n = 6, 9, 12, 15) by dissipative particle dynamics (DPD) simulations is presented in this work. The four surfactants are represented by coarse-grained models composed of the same head group and different numbers of identical tail beads. The transferability of the DPD model over different surfactant systems is carefully checked by adjusting the repulsive interaction parameters and the rigidity of surfactant molecules, in order to reproduce key equilibrium properties of the aqueous micellar solutions observed experimentally, including critical micelle concentration (CMC) and average micelle aggregation number (Nag). We find that the chain length is a good index to optimize the parameters and evaluate the transferability of the DPD model. Our models qualitatively reproduce the essential properties of these surfactant analogues with a set of best-fit parameters. It is observed that the logarithm of the CMC value decreases linearly with the surfactant chain length, in agreement with Klevens' rule. With the best-fit and transferable set of parameters, we have been able to calculate the free energy contribution to micelle formation per methylene unit of -1.7 kJ/mol, very close to the experimentally reported value.

Practical Osmotic Agent for High-Degree Pharmaceutical Pre-Concentration by Organic Solvent Forward Osmosis.

Pre-concentration can reduce the total production costs in the pharmaceutical industry. Organic solvent forward osmosis (OSFO) is a suitable pre-concentration method because of its nonthermal nature, low capital cost, and potential for achieving high-degree concentrations. In a previous study, we first demonstrated a high-degree OSFO concentration. Sucrose octaacetate (SoA) in MeOH was concentrated to 52 wt% using polyethylene glycol (PEG)-400 as the osmotic agent, but the concentrated solution had a concentration of 17% PEG-400 because of the reverse solute flux. This result does not meet the typical purity standards required for pharmaceutical production, indicating the need to determine a suitable osmotic agent that can be used for practical purposes. This study proposes a practical osmotic agent for OSFO pre-concentration. First, osmotic agents were screened from a practical perspective. Polypropylene glycol (PPG)-400 was selected, owing to its low toxicity, good solubility, and low viscosity. Subsequently, the OSFO concentration was demonstrated using PPG-400 as the osmotic agent. SoA in MeOH was concentrated from 9.4 wt% to 48 wt%. The final feed solution contained only 0.04 wt% PPG-400. This result is the first demonstration of successful pharmaceutical pre-concentration using OSFO that satisfies the typical purity requirement in pharmaceutical production.

Energy-efficient trehalose-based polyester nanofiltration membranes for zero-discharge textile wastewater treatment.

Recovery of water, salts, and hazardous dye from complex saline textile wastewater faces obstacles in separating dissolved ionic substances and recovering organic components during desalination. This study realized the simultaneous fractionation, desalination, and dye removal/recovery treatment of textile wastewater by using trehalose (Tre) as an aqueous monomer to prepare polyester loose nanofiltration (LNF) membrane with fine control microstructure via interfacial polymerization. Outperforming the NF270 commercial membrane, the Tre-1.05/TMC optimized membrane achieves zero-discharge textile wastewater treatment, cutting energy consumption by 295% and reducing water consumption by 42.8%. This efficiency surge results from remarkable water permeability (130.83 L m-2 h-1 bar-1) and impressive dye desalination (NaCl/ Direct Red 23 separation factor of 275) of the Tre-1.05/TMC membrane. For a deeper comprehension of filtration performance, the sieving mechanism of polyester LNF membranes was systematically elucidated. This strategic approach offers significant prospects for energy conservation, carbon emission mitigation, and enhanced feasibility of membrane-based wastewater treatment systems.

One-Step Phase Separation and Mineralization Fabrication of Membranes for Oily Wastewater Treatment.

Oily wastewater threatens the environment and the human health. Membrane technology offers a simple and efficient alternative to separating oil and water. However, complex membrane modifications are usually employed to optimize the separation performance. In this research, we develop an extremely simple one-step method to in situ calcium carbonate (CaCO3) nanoparticles onto a porous polyketone (PK) membrane via a nonsolvent induced phase separation (NIPS)-mineralization strategy. We utilized the unique chemical property of PK, which allows it to dissolve in a resorcinol aqueous solution. PK was mixed with tannic acid (TA) and calcium chloride (CaCl2) in a resorcinol aqueous solution to fabricate a casting solution. The activated membrane was cast and immersed into a sodium carbonate (Na2CO3) aqueous solution for taking the one-step NIPS-mineralization process. This proposed NIPS-mineralization mechanism comes to two conclusions: (i) the resulting membrane with comprehensive oleophobic properties and enhanced permeation flux for applications of oil/water separation with ultralow fouling and (ii) simplified the procedure to optimize the membrane performance using regular NIPS steps. The current work explores a one-step NIPS-mineralization technique that offers a novel approach to preparing membranes with highly efficient oil/water separation performance.

Fabrication of polydopamine/rGO Membranes for Effective Radionuclide Removal.

In this work, a novel polydopamine/reduced graphene oxide (PDA/rGO) nanofiltration membrane was prepared to efficiently and stably remove radioactive strontium ions under an alkaline environment. Through the incorporation of PDA and thermal reduction treatment, not only has the interlayer spacing of graphene oxide (GO) nanosheets been appropriately regulated but also an improved antiswelling property has been achieved. The dosage of GO, reaction time with PDA, mass ratio of PDA to GO, and thermal treatment temperature have been optimized to achieve a high-performance PDA/rGO membrane. The resultant PDA/rGO composite membrane has exhibited excellent long-term stability at pH 11 and maintains a steady strontium rejection of over 90%. Moreover, the separation mechanism of the PDA/rGO membrane has been systematically investigated and determined to be a synergistic effect of charge repulsion and size exclusion. Results have indicated that PDA/rGO could be considered as a promising candidate for the separation of Sr2+ ions from nuclear industry wastewater.

Thin continuous membrane coating with high surface energy for comprehensive antifouling seawater distillation.

Membrane distillation (MD) has prominent advantages such as treating high-salinity wastewater with a low-grade thermal energy, high salt rejection, and zero discharge. However, organic fouling and mineral scaling are two major challenges for hydrophobic MD membranes when used for practical applications. Commonly, improving organic fouling- and mineral scaling-resistance require oppositely enhanced wetting properties of membrane, thus is difficult to simultaneously realize dual resistance with one membrane. Here, we proposed to use underwater thermodynamically stable high-surface-energy coating to modify the hydrophobic membrane with Janus structures comprising different surface energy. The underlayered structure meets the hydrophobicity requirements of the MD membrane, while the coating layer realizes dual resistance to organic and inorganic foulants. Theoretical analysis and experimental proof reveal that the membrane with the high-surface-energy coating layer outperforms the pristine one with approximately 10 times of longevity. This strategy provides a new way for the use of high-surface-energy materials in versatilely fouling-resistant MD process.

Hybrid osmotically assisted reverse osmosis and reverse osmosis (OARO-RO) process for minimal liquid discharge of high strength nitrogenous wastewater and enrichment of ammoniacal nitrogen.

Ammoniacal nitrogen (NH4N) is a ubiquitous nitrogen pollutant found in wastewater, which could cause eutrophication and severe environmental stress. It is therefore necessary to manage NH4N by enrichment and recovery for potential reuse, as well as to regulate the amount of environmental discharge. Hybridization of membrane-based processes is an attractive option for further enhancing water and nutrient reclamation from waste streams; thus, in this present work, a hybrid osmotically assisted reverse osmosis (OARO) and reverse osmosis (RO) process was demonstrated for subsequent ammoniacal nitrogen enrichment and wastewater discharge management. Using a commercially-available cellulose triacetate membrane module, model and real wastewater containing approximately 4,000ppm NH4N were effectively dewatered and enriched to a final NH4N content of 40,300ppm. This corresponds to enrichment of around 10 times and approximately 90% pure water recovery. The effective combination of both processes resulted in high efficiency, as well as economical and energy-saving benefits, as shown by the process performance and our preliminary techno-economic analysis. The specific energy consumption of the hybrid process projected to operate at a capacity of 2,000 m3h-1 was determined to be 8.8kWh m-3, or 0.56kWh kg-1 NH4Cl removed/recovered for an initial feed solution containing around 15,300ppm NH4Cl. Hybrid OARO and RO operation was able to achieve satisfactory enrichment by the OARO process and obtaining clean water by the RO process. The hybrid OARO-RO process has shown great potential as a suitable end-stage membrane-based process for wastewater dewatering and NH4N enrichment and recovery toward a circular economy and environmental management, as well as clean water recovery.

When self-assembly meets interfacial polymerization.

Interfacial polymerization (IP) and self-assembly are two thermodynamically different processes involving an interface in their systems. When the two systems are incorporated, the interface will exhibit extraordinary characteristics and generate structural and morphological transformation. In this work, an ultrapermeable polyamide (PA) reverse osmosis (RO) membrane with crumpled surface morphology and enlarged free volume was fabricated via IP reaction with the introduction of self-assembled surfactant micellar system. The mechanisms of the formation of crumpled nanostructures were elucidated via multiscale simulations. The electrostatic interactions among m-phenylenediamine (MPD) molecules, surfactant monolayer and micelles, lead to disruption of the monolayer at the interface, which in turn shapes the initial pattern formation of the PA layer. The interfacial instability brought about by these molecular interactions promotes the formation of crumpled PA layer with larger effective surface area, facilitating the enhanced water transport. This work provides valuable insights into the mechanisms of the IP process and is fundamental for exploring high-performance desalination membranes.

Covalent Organic Framework-Mediated Thin-Film Composite Polyamide Membranes toward Precise Ion Sieving.

Covalent organic frameworks (COFs) have evinced a potential solution that promises for fast and efficient molecular separation due to the presence of orderly arranged pores and regulable pore apertures. Herein, the synthesized COF (TPB-DMTP-COF) with the pore aperture matching the pore size of the nanofiltration (NF) membrane was utilized to modulate the physicochemical characters of the polyamide (PA) membranes. It is demonstrated that COFs with superior polymer affinity and hydrophilicity not only circumvent the nonselective interfacial cavities but also improve the hydrophilicity of the resultant thin-film nanocomposite (TFN) membranes. Furthermore, the predeposited COF layer is able to slow down the diffusion rate toward the reaction boundary through hydrogen bonding, which is consistent with the results of molecular dynamic (MD) and dissipative particle dynamic (DPD) simulations. In this context, COF-modulated TFN membranes show a roughened and thickened surface with bubble-shaped structures in contrast to the nodular structure of original polyamide membranes. Combined with the introduced in-plane pores of COFs, the resultant TFN membranes display a significantly elevated water permeance of 35.7 L m2 h-1 bar-1, almost 4-fold that of unmodified polyamide membranes. Furthermore, the selectivity coefficient of Cl-/SO42- for COF-modulated TFN membranes achieves a high value of 84 mainly related to the enhanced charge density, far exceeding the traditional NF membranes. This work is considered to provide a guideline of exploring hydrophilic COFs as an interlayer for constructing highly permeable membranes with precise ion-sieving ability.

Nanofiber Based Organic Solvent Anion Exchange Membranes for Selective Separation of Monovalent anions.

Present anion exchange membranes are generally constructed by simple and positively charged polymers with insufficient organic solvent resistance, and exhibit a low selectivity in the separation of anions. Here, dissolving poly(paraphenylene terephthalamide) nanofibers into small nanofibers and performing a reaction with quaternary ammonium groups in the one-dimensional small nanofibers, high-performance anion exchange membranes were successfully fabricated. By increasing the 2,3-epoxypropyl trimethylammonium chloride content, the synthesized amide nanofiber quaternary ammonium membranes (ANF#QA) exhibited a higher anion exchange capacity (as high as 1.75 mmol·g-1) and achieved a high electrochemical performance. In electrodialysis, the ANF#QA-10 membrane showed an exceptional Cl- selectivity in dilute and concentrated cells. Due to the dense structure and presence of carboxyl groups on the nanofibers, the ANF#QA membranes exhibited a selective separation of monovalent anions. After 48 h of immersion in aqueous acetone solutions, the final ANF#QA-10 membrane exhibited high desalination and concentration efficiency as the initial membrane. This work highlights the promising use of positive charges on small nanofibers, and proposes the design of a special anion exchange membrane, which can be used for electrodialysis in organic solvent solutions, and to selectively separate monovalent anions.