Ion Permeability Research Articles

Study on the Mechanical Performance, Durability, and Microscopic Mechanism of Cement Mortar Modified by a Composite of Graphene Oxide and Nano-Calcium Carbonate

Nano-calcium carbonate (NC) is a novel ultrafine solid powder material that possesses quantum size effects, small size effects, surface effects, and macroscopic quantum effects that ordinary calcium carbonate lacks. As a nanomaterial with superior properties, graphene oxide (GO) has been studied extensively in the field of construction. In microscopic characterization, the reaction between NC and tricalcium aluminate (C3A) formed a new hydration product, hydrated calcium aluminum carbonate (C3A·CaCO3·11H2O), which enhanced the arrangement of hydration products and optimized the distribution of pore size in the mortar. Regarding the mechanical properties, the addition of GO and NC significantly enhanced the early-age mechanical performance of the mortar. In terms of durability, the incorporation of GO and NC significantly improved the water permeability, chloride ion permeability, and resistance to sulfate attack of the cement mortar. In this study, it was found that adding 1 wt% NC and 0.02 wt% GO not only improves the mechanical and durability properties but also promotes the hydration reaction according to the microstructure analysis. With the help of NC, compared with other studies, the amount of GO is reduced, while the cost is reduced, and the application of GO in the field of cement-based materials is promoted.

A soluble highly-sulfonated polybenzimidazole with high molecular weight as membrane for vanadium flow battery with enhanced performance and long-term stability

A series of novel sulfonated polybenzimidazole (SPBI) membranes containing flexible double ether segments, having high ion exchange capacity (IEC), good solubility as well as high molecular weight, are designed for vanadium flow batteries (VFBs). The bis-ether structure of self-synthesized sulfonic acid monomer, 4,4'-((2-sulfo-1,4-phenylene)bis(oxy))dibenzoic acid, improves the solubility of produced SPBI and the microphase separation structure of prepared membrane by disrupting the regularity of the backbone through a non-planar structure and attenuating the interchain stacking effect of the polymer backbone. Such a highly reactive bis-ether monomer also leads to high molecular weights (2.37−2.82 dL g−1). The copolymerization using another sulfonic acid monomer, Monosodium-5-Sulfoisophthalate monomer, leads to a high IEC of up to 2.08 mmol g−1. As a result, the SPBI membrane shows a low area resistance of 0.21 Ω cm2 and a low vanadium ion permeability of 3.36 × 10−9 cm2 s−1. The VFB cell employing SPBI membrane achieves a very high energy efficiency exceeding 82 % at 200 mA cm−2. In addition, an ultra-long lifetime of over 3400 cycles is accomplished.

Enhancement of Compressive Strength and Durability of Sulfate-Attacked Concrete

This experimental study is carried out in order to improve the properties of sulfate-attacked concrete. The concrete specimens were immersed in 15% Na2SO4 solution before being protected with a concrete repairing agent (CRA). The effects of sulfate corrosion time, the curing time after being attacked, and the concrete repairing agent on concrete were investigated. The experimental results indicate that the properties slightly increased after being attacked by sulfate for 60 days than for 30 days. However, they decreased after being attacked by sulfate for 90 days. CRA could effectively improve the properties of sulfate-attacked concrete. After being re-cured for 7 days, the properties of the sulfate-attacked concrete were significantly improved in comparison with those of the specimens taken out from the sulfate solution immediately. When the specimens were attacked for three months, the compressive strength of specimens coated with CRA was increased by 6.1%, 6.4%, and 6.4% compared to that of the specimens without CRA after being cured for 7 to 56 days, respectively. The carbonation depth of concrete specimens with CRA was reduced by 4.6%, 8.3%, and 4.9%, respectively. However, the chloride ion permeation coefficient of concrete with CRA decreased by 20.3%, 28.5%, and 28.7%, respectively, for the concrete immersed in sulfate for one month.

Electronic Polarization Leads to a Drier Dewetted State for Hydrophobic Gating in the Big Potassium Channel.

In the hydrophobic gating mechanism proposed for some ion channels, ion permeation is not blocked by the physical dimension of the channel pore but by its dewetted state which constitutes the energetic bottleneck. A major source of uncertainty in the mechanism is that the dewetted state was not observed in experiments and only probed in simulations using nonpolarizable force fields, which do not accurately represent the properties of confined water. Here we analyze hydration of the central cavity in the pore-gate domain of the Big Potassium channel using molecular dynamics and grand canonical Monte Carlo simulations with enhanced sampling techniques. Including polarization leads to a much drier dewetted state and a higher barrier for the transition to the wet state, suggesting more effective hydrophobic gating. The simulations also identify two backbone carbonyls at the bottom of the selectivity filter as good candidates for characterizing the dewetted state using infrared spectroscopies.

High-efficiency dysprosium-ion extraction enabled by a biomimetic nanofluidic channel

Biological ion channels exhibit high selectivity and permeability of ions because of their asymmetrical pore structures and surface chemistries. Here, we demonstrate a biomimetic nanofluidic channel (BNC) with an asymmetrical structure and glycyl-L-proline (GLP) -functionalization for ultrafast, selective, and unidirectional Dy3+ extraction over other lanthanide (Ln3+) ions with very similar electronic configurations. The selective extraction mainly depends on the amplified chemical affinity differences between the Ln3+ ions and GLPs in nanoconfinement. In particular, the conductivities of Ln3+ ions across the BNC even reach up to two orders of magnitude higher than in a bulk solution, and a high Dy3+/Nd3+ selectivity of approximately 60 could be achieved. The designed BNC can effectively extract Dy3+ ions with ultralow concentrations and thereby purify Nd3+ ions to an ultimate content of 99.8 wt.%, which contribute to the recycling of rare earth resources and environmental protection. Theoretical simulations reveal that the BNC preferentially binds to Dy3+ ion due to its highest affinity among Ln3+ ions in nanoconfinement, which attributes to the coupling of ion radius and coordination matching. These findings suggest that BNC-based ion selectivity system provides alternative routes to achieving highly efficient lanthanide separation.

Ab Initio Molecular Dynamics Investigation on the Permeation of Sodium and Chloride Ions Through Nanopores in Graphene and Hexagonal Boron Nitride Membranes.

Nanoporous membranes promise energy-efficient water desalination. Hexagonal boron nitride (h-BN), like graphene, exhibits outstanding physical and chemical properties, making it a promising candidate for water treatment. We employed Car-Parrinello molecular dynamics simulations to establish an accurate modeling of Na+ and Cl- permeation through hydrogen passivated nanopores in graphene and h-BN membranes. We demonstrate that ion separation works well for the h-BN system by imposing a barrier of 0.13 eV and 0.24 eV for Na+ and Cl- permeation, respectively. In contrast, for permeation of the graphene nanopore, the Cl- ion faces a minimum of energy of 0.68 eV in the nanopore plane and is prone toward blockade of the nanopore, while the Na+ ion experiences a slight minimum of 0.03 eV. Overall, the desalination performance of h-BN nanopores surpasses that of their graphene counterparts.

TMAO Impairs Mouse Aortic Vasodilation by Inhibiting TRPV4 Channels in Endothelial Cells.

Trimethylamine oxide (TMAO) is an intestinal flora metabolite associated with risk of cardiovascular diseases. Transient receptor potential vanilloid 4 (TRPV4) is a Ca2+-permeable ion channel that is essential for vasodilation and endothelial function. Currently, there are few studies on the effect of TMAO on TRPV4 channels. In the present study, Ca2+ imaging of vascular tissue showed that TMAO inhibited TRPV4-mediated Ca2+ influx into aortic endothelial cells in a dose-dependent manner. Furthermore, a whole-cell patch clamp assay showed that TMAO blocked TRPV4-mediated cation currents. Notably, results of aortic vascular tension measurement showed that TMAO impaired endothelium-dependent vasodilation in mouse aortic vessels through the TRPV4-NO pathway. Our results indicated that TMAO inhibited Ca2+ entry in endothelial cells and impaired vasodilation through the TRPV4-NO pathway in mice. These results provide scientific evidence for novel pathogenic mechanisms underlying the role of TMAO in cardiovascular disease.

Analysis of Ion Transport Properties of Glycine max HKT Transporters and Identifying a Regulation of GmHKT1;1 by the Non-Functional GmHKT1;4.

High-affinity potassium transporters (HKTs) play an important role in plants responding to salt stress, but the transport properties of the soybean HKT transporters at the molecular level are still unclear. Here, using Xenopus oocyte as a heterologous expression system and two-electrode voltage-clamp technique, we identified four HKT transporters, GmHKT1;1, GmHKT1;2, GmHKT1;3 and GmHKT1;4, all of which belong to type I subfamily, but have distinct ion transport properties. While GmHKT1;1, GmHKT1;2 and GmHKT1;3 function as Na+ transporters, GmHKT1;1 is less selective against K+ than the two other transporters. Astonishingly, GmHKT1;4, which lacks transmembrane segments and has no ion permeability, is significantly expressed, and its gene expression pattern is different from the other three GmHKTs under salt stress. Interestingly, GmHKT1;4 reduced the Na+/K+ currents mediated by GmHKT1;1. Further study showed that the transport ability of GmHKT1;1 regulated by GmHKT1;4 was related to the structural differences in the first intracellular domain and the fourth repeat domain. Overall, we have identified one unique GmHKT member, GmHKT1;4, which modulates the Na+ and K+ transport ability of GmHKT1;1 via direct interaction. Thus, we have revealed a new type of HKT interaction model for altering their ion transport properties.

Spontaneous Transition between Multiple Conductance States and Rectifying Behaviors in an Artificial Single‐Molecule Funnel

It has long been an aspirational goal to create artificial channel structures that replicate the feat achieved by ion channel proteins. Biological ion channels occasionally demonstrate multiple conductance states (known as subconductance), remaining a challenging property to achieve in artificial channel molecules. We report a funnel‐shaped single‐molecule channel constructed by an electron‐deficient macrocycle and two electron‐deficient aromatic imide arms. Planar lipid bilayer measurements reveal distinct current recordings, including a closed state, two conducting states, and spontaneous transitions between the three states, resembling the events seen in biological ion channels. The transitions result from conformational changes induced by chloride transport in the channel molecule. Both opening states show a non‐linear and rectifying I‐V relationship, indicating voltage‐dependent transport due to the asymmetrical channel structure. This work could enhance our understanding of ion permeation and channel opening mechanism.

Unipolar Ionic Diode Nanofluidic Membranes Enabled by Stepped Mesochannels for Enhanced Salinity Gradient Energy Harvesting.

Developing ionic diode membranes featuring asymmetric structures is in high demand for salinity gradient energy harvesting. These membranes offer benefits in mitigating ion concentration polarization, thereby promoting ion permeability. However, most reported works focus on the role of heterogeneous charge-based bipolar ionic diode membranes for ion concentration polarization suppression, with comparatively less attention given to maintaining ion selectivity. Herein, unipolar ionic diode nanofluidic mesoporous silica membranes featuring stepped mesochannels were developed via a micellar sequential oriented interfacial self-assembly strategy as a salinity gradient energy harvester. Due to the asymmetric mesochannels and unipolar structure (both sides carry negative charge), the ionic diode membranes exhibit a strong rectification ratio of ∼15.91 to facilitate unidirectional ion transport while maintaining excellent cation selectivity (cation transfer number of ∼0.85). Besides, the vertically aligned mesochannels significantly reduce ion transport resistance, generating a high ionic flux. Consequently, the unipolar ionic diode nanofluidic membranes demonstrate a power output of 5.88 W/m2 between artificial sea and river water. The unipolar feature gives notable enhancements of 296% and 144% in power output compared to the symmetric membrane and bipolar ionic diode membrane, respectively. This work opens up new routes for designing ionic diode membranes for salinity gradient energy harvesting.

Enhancing chloride ion permeability resistance of recycled aggregate concrete through internal curing with glazed hollow beads

This study explores the effects of glazed hollow beads (GHB) dosage and additional water amount on the capillary negative pressure, mechanical properties, initial resistivity, and electric flux in conditions where recycled aggregate concrete (RAC) is subject to cracking. The chloride ion (Cl-) diffusion coefficient for RAC cured internally was evaluated using the resistivity method, which also looked at the relationship between the diffusion coefficient, GHB dosage, and additional water amount. This analysis advances our understanding of the functional mechanisms of pre-soaked GHB in RAC. The research reveals that incorporating pre-soaked GHB enhances RAC in two primary ways. Firstly, pre-soaked GHB acts as an internal curing agent that stimulates the formation of hydration products, thereby filling internal voids and mitigating micro-crack development. Secondly, it functions as an adsorbent. The differential in relative humidity and internal pressure between the unsaturated GHB and the cement stone matrix promotes the sequestration of corrosive agents in cracked RAC. Additionally, an internal curing impact factor has been introduced, forming the basis of a new model to calculate the Cl- diffusion coefficient that accounts for both GHB dosage and additional water intake. The established quantitative relationships between resistivity, electric flux, and Cl- diffusion coefficient in GHB-treated RAC (GHB-RAC) provide a methodological framework for quickly evaluating the durability of GHB-RAC against Cl- intrusion in practical engineering contexts.

Effects of interlayer spacing and applied pressure on the lanthanide transport in MoS2-based two-dimensional channels

ABSTRACT Rare-earth elements (REEs) are critical to modern industry but difficult to separate due to their subtle and monotonic changes in physicochemical properties. MoS2-based two-dimensional (2D) materials offer novel opportunities for enhancing REE separation, exhibiting a distinct volcano-shaped transport performance distribution that peaks at Sm3+. However, the specific contributions of thermodynamic and kinetic factors to ion transport within 2D confinement remain unclear. In this study, we conducted a series of non-equilibrium all-atom molecular dynamics (MD) simulations to explore the effects of interlayer spacing and external pressure on the transport of lanthanide ions in Å-scale acetate functionalized 2D MoS2 (MoS2-COOH) channels. We examined ion entry and permeation rates, water flux, dehydration, and binding modes. The simulation results reveal that the transport trends of lanthanide ions are jointly driven by the dehydration degree and the relative-binding strengths of ions to water and to the acetate within the 2D channels. Notably, the dehydration pattern of lanthanide ions during permeation is closely linked to kinetic factors. Overall, this study provides a detailed atomistic understanding of the mechanisms underlying lanthanide ion transport under confinement. These findings point to the significant potential for tuning confinement and chemical functionalization within Å-scale channels for more efficient REE separation.

Long-Term Performance Evaluation and Fouling Characterization of a Full-Scale Brackish Water Reverse Osmosis Desalination Plant

Water scarcity in Tunisia’s semi-arid regions necessitates advanced brackish water desalination solutions. This study evaluates the long-term performance and fouling characteristics of the largest brackish water reverse osmosis desalination plant in southern Tunisia over a period of 5026 days. The plant employs two-stage spiral-wound membrane elements to treat groundwater with a salinity of 3.2 g L−1. The pre-treatment process includes oxidation, sand filtration, and cartridge filtration, along with polyphosphonate antiscalant dosing. Membrane performance was assessed through the analysis of operational data, standardization of permeate flow (Qps) and salt passage (SPs), and the calculation of water (A), solute (B), and ionic (Bj) permeability coefficients. Over the operational period, there was an increase in operating pressure, pressure drop, and permeate conductivity, accompanied by a gradual increase in SPs as well as in the solute B and ionic Bj permeability coefficients. The average B increased by 82%, reflecting a decrease in solute rejection over time. Additionally, the ionic permeability coefficients for both SO42− and Cl− ions increased, with Cl− showing an 88% increase and SO42− showing an 87% increase. The produced water’s salinity increased by 67%, indicating a significant loss of membrane performance. To identify the cause of these problems, membrane characterization was analyzed using visual inspection, X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR). The characterization revealed the complex nature of the foulants, with a predominant presence of calcium sulfate, along with minor quantities of calcite, dolomite, and silica. The extent of CaSO4 deposition suggests poor antiscaling efficiency, highlighting the critical importance of selecting an effective antiscalant to mitigate membrane fouling.

Ion-Selective Transport Promotion Enabled by Angstrom-Scale Nanochannels in Dendrimer-Assembled Polyamide Nanofilm for Efficient Electrodialysis.

The ion permeability and selectivity of membranes are crucial in nanofluidic behavior, impacting industries ranging from traditional to advanced manufacturing. Herein, we demonstrate the engineering of ion-conductive membranes featuring angstrom-scale ion-transport channels by introducing ionic polyamidoamine (PAMAM) dendrimers for ion separation. The exterior quaternary ammonium-rich structure contributes to significant electrostatic charge exclusion due to enhanced local charge density; the interior protoplasmic channels of PAMAM dendrimer are assembled to provide additional degrees of free volume. This facilitates the monovalent ion transfer while maintaining continuity and efficient ion screening. The dendrimer-assembled hybrid membrane achieves high monovalent ion permeance of 2.81 mol m-2 h-1 (K+), reaching excellent mono/multivalent selectivity up to 20.1 (K+/Mg2+) and surpassing the permselectivities of state-of-the-art membranes. Both experimental results and simulating calculations suggest that the impressive ion selectivity arises from the significant disparity in transport energy barrier between mono/multivalent ions, induced by the "exterior-interior" synergistic effects of bifunctional membrane channels.

Influence of combined substitution of slag and fly ash in improving the pore structure and corrosion resistance of foam concrete mixtures used for reinforced concrete applications

Foam concretes (FCs) have been used for several light-weight applications demanding low strength; however, their use for reinforced concrete (RC) applications is limited since high macrovoid amounts result in weaker matrices. The high w/c and overlapping of macrovoids have been identified as critical factors constituting a permeable microstructure in FC systems. Since corrosion performance is a critical aspect in the design of RC members and that the durability parameters of concrete, such as its porosity, pore size distribution, and permeability, also play a vital role in restricting the diffusion of chloride ions, particularly in the cover region of members, it is imperative to determine these properties and thoroughly understand the material behaviour or characteristics. In the current study, five FC mixtures (GF0 to GF4) were produced using ground granulated blast furnace slag (GGBS) and fly ash (FA) as a replacements for cement and sand, respectively, at different dosages, considering both economic and environmental aspects. The principal objective of the study is to determine the pore and permeability related properties of produced FCs, assess their corrosion performance, and ascertain their suitability for RC applications by comparing their performance with that of conventional M25-grade concrete. Also, the influence of the combined effect of GGBS and FA addition and the individual effect of FA addition were assessed. The research findings showed that FCs had a higher water absorption capacity and porosity compared to M25 concrete. In addition, the inclusion of GGBS and FA resulted in a decrease in water absorption by 8%–19% and a decrease in porosity by 23%–36% compared to the control FC mixture. The Mercury Intrusion Porosimetry (MIP) results indicated a substantial enhancement in gel pores, threshold, and critical pore diameter, while the size of the larger capillary pore decreased by 90%–95% when GGBS and FA were added compared to the control FC mixture. The scanning electron microscopy (SEM) analysis and binary images from the image analysis revealed the presence of uniformly distributed and distinct macrovoids formed by foam. These macrovoids were predominantly found within the size range of 7.1μm – 100 µm. The addition of GGBS and FA particles to FC mixes resulted in a significant improvement in the chloride ion permeation (CIP) class, reducing it from 'High' to 'Very Low' compared to M25 concrete. The Accelerated Corrosion Test (ACT) results obtained from FCs demonstrated a significant increase in cracking time ranging from 30% to 323%, as well as a notable decrease in mass loss ranging from 56% to 85% when compared to M25 concrete. The Fourier transform infrared (FTIR) and energy dispersive spectroscopy (EDS) analysis results revealed the presence of corrosion products, including feroxyhyte, akageneite, and Friedel's salt crystal, in both FCs and M25 concrete, indicating the occurrence of corrosion by the chloride ions present in the NaCl solution outside the specimen. Overall, the porosity, CIP, and corrosion resistance of FC with GGBS and FA are superior to those of the M25 concrete, making it suitable for use in RC applications.

Janus graphene oxide membrane with rational allocation of functional regions as unidirectional ion valve system

Membrane-based ion sieving is critical to green desalination processes such as sustainable ionic resource extraction. Two-dimensional (2D) graphene oxide (GO) membranes exhibit unique ionic transport properties owning to the supernormal enhancement of channel effects induced by diverse functional regions under nanoconfinement. However, the discrete and random distribution of the hydrophilic/hydrophobic and positively/negatively charged regions restricts the GO membrane to give full play to its potential in selective ions separation. Herein, a novel strategy is proposed to engineer the asymmetric three-tier architecture of a Janus GO membrane with rational allocation of functional regions. The wise series connection of ① surface positively charged hydrophilic layer of PEI, ② intermediate negatively charged hydrophilic layer of GO and ③ bottom hydrophobic porous layer of rGO along the cross-membrane direction established internal gradients of structure, wetting and charge, resulting in reinforced exclusion of retained divalent ions and reduced stagnation of targeted monovalent ions. Based on the continuous anisotropic gradients, the Janus GO membrane was endowed with the unique capability to act as a unidirectional ion valve system, showcasing impressive permeation performance of monovalent ions permeation rate of 0.244 mol m−2 h−1 with monovalent/divalent ions selectivity of 66.1, and remarkable nanofiltration performance of divalent salt rejections of >96.5 % with monovalent/divalent ions separation factor up to 70.9. The implications of this work will revolutionize the regulation and functionalization of 2D nanofluidic channels for selective ions transport, which is highly desirable for a wide range of green desalination applications.

Selectivity filter mutations shift ion permeation mechanism in potassium channels.

Potassium (K+) channels combine high conductance with high ion selectivity. To explain this efficiency, two molecular mechanisms have been proposed. The "direct knock-on" mechanism is defined by water-free K+ permeation and formation of direct ion-ion contacts in the highly conserved selectivity filter (SF). The "soft knock-on" mechanism involves co-permeation of water and separation of K+ by water molecules. With the aim to distinguish between these mechanisms, crystal structures of the KcsA channel with mutations in two SF residues-G77 and T75-were published, where the arrangements of K+ ions and water display canonical soft knock-on configurations. These data were interpreted as evidence of the soft knock-on mechanism in wild-type channels. Here, we test this interpretation using molecular dynamics simulations of KcsA and its mutants. We show that while a strictly water-free direct knock-on permeation is observed in the wild type, conformational changes induced by these mutations lead to distinct ion permeation mechanisms, characterized by co-permeation of K+ and water. These mechanisms are characterized by reduced conductance and impaired potassium selectivity, supporting the importance of full dehydration of potassium ions for the hallmark high conductance and selectivity of K+ channels. In general, we present a case where mutations introduced at the critical points of the permeation pathway in an ion channel drastically change its permeation mechanism in a nonintuitive manner.

Ion-selective supramolecular membrane with pH-regulated smart nanochannels for lithium extraction

Tunable gating ion-conducting membranes with high water permeability and precise ion selectivity remain urgently demanded in smart nanofiltration for efficient lithium extraction. Herein, inspired by the filtration function of protein channels, we report a smart and high-performance supramolecular membrane constructed via coordination between quaternary ammonium ligands (m-phenylenediamine/polyethyleneimine) and metal ion center (Cu2+). The pore architecture of the supramolecular membrane is dynamic and can be switched by applying pH stimulus, where coordinated interchain expands when exposed to acidic operating conditions and induces concomitantly reinforced electrostatic exclusion due to enhanced local charge density. The tunable gating regularity enables operando modulation of precise ionic separation in situ. The resulting membrane exhibits significantly enhanced water permeance (19.8 L m−2 h−1·bar−1) and simultaneously promoted Li+/Mg2+ selectivity (RMg2+ = 96.4 %), surpassing typical trade-off between permeability and selectivity at pH 3 condition. This study demonstrates the amazing capability of environmental-responsive regulation of membrane pore-channel structure, and provides inspiration for engineering advanced supramolecular membranes for lithium extraction and beyond.

Influence of interface agent and form on the bonding performance and impermeability of ordinary concrete repaired with alkali-activated slag cementitious material

Alkali-activated slag cementitious materials (AASCMs) exhibit fast hardening, early strength development, high strength, and low carbon content, making them suitable for repairing damaged concrete. However, the bonding performance of the repaired interface and the impermeability of the repaired specimens require further evaluation. Accordingly, this study performed splitting tensile, water penetration, chloride ion penetration, and microanalysis tests on ordinary concrete specimens repaired with AASCMs. The results demonstrated that epoxy resin and cement mortar improved the interfacial bonding strength, water permeability, and chloride ion permeability of the alkali-activated slag cementitious material-Portland cement (AASCM-PC) specimens. The rectangular mortise joint and S-shaped interface improved the interfacial bonding strength and water permeability of the AASCM-PC specimens but slightly reduced their chloride ion permeability. Compared with ordinary concrete, AASCM has fewer harmful voids and denser microstructure, improving the impermeability of the repaired specimens.

Angstrom‐scale channels with versatile ion‐membrane interactions enabling precise ion separation via electrodialysis

AbstractIn nature, efficient and selective ion transport is facilitated by ion‐conductive channels in cell membranes; these channels reveal an architectural design with specialized functionality. Drawing inspiration from this, mechanistic insights into the angstrom‐scale‐channel membrane composed of ionic‐crosslinked polybenzimidazole and sulfonated poly(ether ether ketone), exhibiting functional differentiation and efficient ion‐sieving properties are presented. Nanochannels allow for strong hydrogen‐bonding interactions with hydrated ions of higher polarity, while rendering significant electrostatic charge effects that impede the transition of multivalent ions by compressing effective passageways. Both hydrogen bonding and electrostatic interactions synergistically result in high selectivity for monovalent ions over multivalent ions because the latter requires overcoming higher energy barriers for transport compared with the former, thereby causing varying extents of ion dehydration within the nanochannels. The resulting membrane achieves a high monovalent ion permeation rate of 1.35 mol m−2 h−1 with a high mono/multivalent ion selectivity of 56.5 for K+/Mg2+ and 286 for K+/Al3+.