Precise Separation Research Articles

Comparative Study of Gas and Liquid Chromatography Methods for the Determination of Underivatised Neutral and Acidic Cannabinoids and Cholesterol.

The aim of our study was to develop a gas chromatographic method coupled with mass spectrometry (GC-MS) for the determination of underivatised neutral (CBDs-N) and acidic (CBDs-A) cannabinoids (CBDs) and cholesterol (Chol). Emphasis was also placed on comparing our original GC-MS method with the currently developed C18-high-performance liquid chromatography with photodiode detection (C18-HPLC-DAD). A combination of a long GC column, shallow temperature column programme, and mass-spectrometry was employed to avoid issues arising from the overlap between CBDs and Chol and background fluctuations. The pre-column procedure for CBDs and Chol in egg yolks consisted of hexane extractions, whereas the pre-column procedure for CBDs in non-animal samples involved methanol and hexane extractions. CBDs-A underwent decarboxylation to CBDs during GC-MS analyses, and pre-column extraction of the processed sample with NaOH solution allowed for CBD-A removal. No losses of CBDs-N were observed in the samples extracted with NaOH solution. GC-MS analyses of the samples before and after extraction with NaOH solution enabled the quantification of CBDs-A and CBDs-N. CBDs-A did not undergo decarboxylation to CBDs-N during C18-HPLC-DAD runs. The use of the C18-HPLC-DAD method allowed simultaneous determination of CBDs-N and CBDs-A. In comparison to the C18-HPLC-DAD method, our GC-MS technique offered improved sensitivity, precision, specificity, and satisfactory separation of underivatised CBDs and Chol from biological materials of endogenous species, especially in hemp and hen egg yolk. The scientific novelty of the present study is the application of the GC-MS method for quantifying underivatised CBDs-A, CBDs-N, and Chol in the samples of interest.

Confined-Coordination Induced Intergrowth of Metal-Organic Frameworks into Precise Molecular Sieving Membranes.

Metal-organic framework (MOF) membranes with rich functionality and tunable pore system are promising for precise molecular separation; however, it remains a challenge to develop defect-free high-connectivity MOF membrane with high water stability owing to uncontrollable nucleation and growth rate during fabrication process. Herein, we report on a confined-coordination induced intergrowth strategy to fabricate lattice-defect-free Zr-MOF membrane towards precise molecular separation. The confined-coordination space properties (size and shape) and environment (water or DMF) were regulated to slow down the coordination reaction rate via controlling the counter-diffusion of MOF precursors (metal cluster and ligand), thereby inter-growing MOF crystals into integrated membrane. The resulting Zr-MOF membrane with angstrom-sized lattice apertures exhibits excellent separation performance both for gas separation and water desalination process. It was achieved H2 permeance of ~1200 GPU and H2/CO2 selectivity of ~67; water permeance of ~8 L ⋅ m-2 ⋅ h-1 ⋅ bar-1 and MgCl2 rejection of ~95 %, which are one to two orders of magnitude higher than those of state-of-the-art membranes. The molecular transport mechanism related to size-sieving effect and transition energy barrier differential of molecules and ions was revealed by density functional theory calculations. Our work provides a facile approach and fundamental insights towards developing precise molecular sieving membranes.

Confined‐Coordination Induced Intergrowth of Metal–Organic Frameworks into Precise Molecular Sieving Membranes

AbstractMetal–organic framework (MOF) membranes with rich functionality and tunable pore system are promising for precise molecular separation; however, it remains a challenge to develop defect‐free high‐connectivity MOF membrane with high water stability owing to uncontrollable nucleation and growth rate during fabrication process. Herein, we report on a confined‐coordination induced intergrowth strategy to fabricate lattice‐defect‐free Zr‐MOF membrane towards precise molecular separation. The confined‐coordination space properties (size and shape) and environment (water or DMF) were regulated to slow down the coordination reaction rate via controlling the counter‐diffusion of MOF precursors (metal cluster and ligand), thereby inter‐growing MOF crystals into integrated membrane. The resulting Zr‐MOF membrane with angstrom‐sized lattice apertures exhibits excellent separation performance both for gas separation and water desalination process. It was achieved H2 permeance of ~1200 GPU and H2/CO2 selectivity of ~67; water permeance of ~8 L ⋅ m−2 ⋅ h−1 ⋅ bar−1 and MgCl2 rejection of ~95 %, which are one to two orders of magnitude higher than those of state‐of‐the‐art membranes. The molecular transport mechanism related to size‐sieving effect and transition energy barrier differential of molecules and ions was revealed by density functional theory calculations. Our work provides a facile approach and fundamental insights towards developing precise molecular sieving membranes.

Advanced high-resolution chromatographic strategies for efficient isolation of natural products from complex biological matrices: from metabolite profiling to pure chemical entities

AbstractThe isolation of pure compounds from extracts represents a key step common to all investigations of natural product (NP) research. Isolation methods have gone through a remarkable evolution. Current approaches combine powerful metabolite profiling methods for compounds annotation with omics mining results and/or bioassay for bioactive NPs/biomarkers priorisation. Targeted isolation of prioritized NPs is performed using high-resolution chromatographic methods that closely match those used for analytical profiling. Considerable progress has been made by the introduction of innovative stationary phases providing remarkable selectivity for efficient NPs isolation. Today, efficient separation conditions determined at the analytical scale using high- or ultra-high-performance liquid chromatography can be optimized via HPLC modelling software and efficiently transferred to the semi-preparative scale by chromatographic calculation. This ensures similar selectivity at both the analytical and preparative scales and provides a precise separation prediction. High-resolution conditions at the preparative scale can notably be granted using optimized sample preparation and dry load sample introduction. Monitoring by ultraviolet, mass spectrometry, and or universal systems such as evaporative light scattering detectors and nuclear magnetic resonance allows to precisely guide the isolation or trigger the collection of specific NPs with different structural scaffolds. Such approaches can be applied at different scales depending on the amounts of NPs to be isolated. This review will showcase recent research to highlight both the potential and constraints of using these cutting-edge technologies for the isolation of plant and microorganism metabolites. Several strategies involving their application will be examined and critically discussed. Graphical abstract

How to transform microporous organic polymers for membrane-based separation: A review

Microporous organic polymers (MOPs) are ideal candidates for designing highly efficient and precise molecular sieving separation membranes due to their exceptional porosity, rigid pore structure, pore size designability, and ease of functionalization. These materials encompass COFs, POCs, PAFs, PIMs, CMPs, and HCPs. However, the path to utilizing MOPs as separation membrane applications has encountered obstacles. Several studies have been conducted to fully exploit the exceptional properties of these polymers. The better application of MOPs materials should be considered in terms of material design and synthesis, membrane formation, and membrane task-specific applications. This review objectively reclassifies MOPs materials based on the latest research and material ordering and provides a systematic summary of MOPs material synthesis and design, MOPs-based membrane fabrication difficulties, and current novel MOPs-based membrane design. Additionally, it introduces in detail the preparation of different types of MOPs-based membranes. The applications of MOPs-based membranes in separation applications are also thoroughly summarized. Finally, this review summarizes the challenges of current MOPs-based membrane development, proposes future opportunities and potential applications in the separation and purification field.

A novel approach for disentangling packed peaks in the energy spectrum of γ detector arrays through γ-γ coincidence analysis

A novel approach has been proposed to effectively separate cascaded and closely packed full energy peaks in the energy spectrum of γ detector arrays. By conducting a sequence of γ-γ coincidence analyses on the energy spectrum, it is feasible to obtain a spectrum that represents the product of these packed peaks. We have designated the newly obtained spectrum as the “product spectrum”. The energy spectrum and the newly obtained product spectrum can be simultaneously fitted, enabling a more precise fitting and separation of the closely packed peaks. This method has been mathematically proven, and validated through the use of Monte Carlo simulation. The systematic errors of this method are also taken into consideration.

H2O-balance-regulated cation–anion competitive coordination for selective elements extraction from spent lithium-ion batteries

Key resources necessary for lithium-ion batteries (LIBs) will deplete rapidly if recycling is not considered given the significant demand for LIBs. However, the current recovery method from spent LIBs is hindered by low efficiency, high energy consumption, and severe environmental issues, which curtail the sustainability of recycling industry. Here, we propose a new strategy for selective elements extraction from LiCoO2 based on H2O-balance-regulated cation–anion competitive coordination. The lithium can be preferentially precipitated in deep eutectic solvents (DES) with an appropriate amount of H2O. Such a preferential lithium behaviors contributes to the subsequent precise separation of transition metal elements by further adjusting the water content, thus enabling the recovery of all element and direct regeneration of DES for further spent LIB recycling. The developed DES-based technology can achieve the ultrahigh leaching efficiency of 99.99% for Li and Co with an acceptable recovery efficiency of Li and Co (≥91.23%) and a desirable purity of recycled Li2C2O4 and CoC2O4·2H2O (≥98.43%). These Li and Co performances are still maintained at this level even after three-time regeneration of DES. This methodology can also be extended to other recycling chemistries of spent LIBs and lay the theoretical foundation for the recovery of valuable metals from spent battery materials using DESs with a simple process, low energy consumption, and waste-free recycling.

Building ordered graphene membranes by intermediate layer assisted stacking method for promoted desalination

Laminar separation membranes stacked by graphene and its derivatives hold the merit of controlled mass transfer behaviors. However, precise ion separation is challenged by the disordered assembly of nanosheets on macroporous substrates with complicated surface properties. Herein, we prepare ultrathin ordered graphene membranes by an intermediate layer assisted stacking method. Nanoporous covalent organic framework (COF) nanosheets are first vacuum-filtered on macroporous substrates, followed by deposition and thermal reduction of graphene oxide nanosheets to deliver ultrathin reduced graphene oxide (rGO) layers. The COF-decorated substrates provide a hydrophilic surface with reduced pores and roughness, facilitating the formation of ultrathin rGO layers with ordered stacking patterns and reduced microporous defects. Consequently, the obtained rGO/COF composite membranes can reject ∼90% of Na2SO4, ∼50% of NaCl, and >98% of various organic dyes, which are higher than pure rGO membranes. Meanwhile, the rGO/COF composite membranes can maintain good stability in solutions with different pH values and salt concentrations, and can be long-term operated for at least 10 days. This work is expected to deepen the understanding of the structure of laminar membranes and provides new perspectives to design ordered laminar membranes.

Antifouling and smart covalent organic framework composite nanofiltration membranes with light-gated molecular transport

Covalent organic framework (COF) holds great promise in affording precise and fast molecular separation. Inspired by the light-gated channels in cell membranes, we developed artificial light-gated molecular channel composite membranes by vacuum filtration COF with azobenzene (AZO) functional groups. The simple stimuli response could remotely adjust the membranes separation performance. The cis membranes with off state under ultraviolet (UV) light have higher dye rejection than trans membranes with on-state channels. The permeance of composite membranes increased from 19.56 to ∼ 42.30 L h−1 m−2 bar−1, dye (Rose Bengal (RB)) rejection increased from 94.40 % to 99.12 % after 10 min of 365 nm UV irradiation. In addition, the composite nanofiltration membranes exhibited good antifouling performance due to hydrophilic and highly smooth surface. By controlling the trans-to-cis AZO isomerization via UV /visible (Vis) light, the solvent permeance and dye rejection can be dynamically tuned due to the adjustable pore size.

Ultrafast self-transportation and efficient separation of organic droplets on semi-conical asymmetric structure

Manipulating oil droplets in an aqueous solution is highly desirable for organic multiphase liquid separation. Despite substantial works in the realm of organic multiphase liquid manipulation and separation, the ultrafast transportation and efficient and precise separation of these liquids, especially those with varied surface tensions, encounters significant challenges due to little driving forces. To address this issue, a semi-conical structure with pine-needlelike features and incorporated wedge-shaped grooves is fabricated, which could support the ultrafast transport and separation of organic droplets. For pre-wetted superhydrophobic surfaces, organic liquids with lower surface tension can be transported at a speed of 305.6 mm/s. The Laplace pressure difference caused by the conical structure determines the direction of transport of organic liquids, and the capillary force caused by flat wedge-shaped grooves increases the transport speed of organic droplets on the surface. Based on the characteristics of “differential” transportation and directional transportation, the separation of mixed organic liquids is realized. This biomimetic design concept will pave a path for microfluidics, liquid manipulation, and the separation of various organic liquids.

Novel 3D reciprocal space visualization of strain relaxation in InSb on GaAs substrates

This study introduces the reciprocal space polar visualization (RSPV) method, a novel approach for visualizing x-ray diffraction-based reciprocal space data. RSPV allows for the precise separation of tilt and strain, facilitating their individual analysis. InSb was grown by molecular beam epitaxy on two (001) GaAs substrates—one with no misorientation (sample A) and one with 2° surface misorientation from the (001) planes (sample B). There is a substantial lattice mismatch with the substrate, and this results in the generation of defects within the InSb layer during growth. To demonstrate RSPV’s effectiveness, a comprehensive comparison of surface morphology, dislocation density, strain, and tilt was conducted. RSPV revealed previously unobserved features of the 004 InSb Bragg peak, partially explained by the presence of threading dislocations and oriented abrupt steps. Surface morphologies examined by an atomic force microscope revealed that sample B had significantly lower root mean square roughness. Independent estimates of threading dislocation density (TDD) using x-ray diffraction (XRD) and electron channelling contrast imaging confirmed that sample B exhibited a significantly lower TDD than sample A. XRD methods further revealed unequal amounts of α- and β-type threading dislocations in both samples, contributing to an anisotropic Bragg peak. RSPV is shown to be a robust method for exploring 3D reciprocal space in any crystal, demonstrating that growing InSb on misoriented GaAs produced a higher-quality crystal compared to an on-orientation substrate.

Nanochannel Stability of Chemically Converted Graphene Oxide Membranes.

Chemically converted graphene oxide laminate membranes, which exhibit stable interlayered nanochannels in aqueous environments, are receiving increasing attention owing to their potential for selective water and ion permeation. However, how the molecular properties of conversion agents influence the stabilization of nanochannels and how effectively nanochannels are stabilized have rarely been studied. In this study, mono-, di-, and tri-saccharide molecules of glucose (Glu), maltose (Glu2), and maltotriose (Glu3) are utilized, respectively, to chemically modify graphene oxide (GO). The aim is to create nanochannels with different levels of stability and investigate how these functional conversion agents affect the separation performance. The effects of the property differences between different conversion agents on nanochannel stabilization are demonstrated. An agent with efficient chemical reduction of GO and limited intercalation in the resulting nanochannel ensures satisfactory nanochannel stability during desalination. The stabilized membrane nanochannel exhibits a permeance of 0.69 L m-2 h-1 bar-1 and excellent Na2SO4 rejection of 96.42%. Furthermore, this optimized membrane nanochannel demonstrates enhanced stability under varying external conditions compared to the original GO. This study provides useful information for the design of chemical conversion agents for GO nanochannel stabilization and the development of nanochannel membranes for precise separation.

Sheathless and high-throughput separation of multi-target particles combining inertia and deterministic lateral displacement (DLD) in a microchannel

Precisely separation of multicomponent particle mixtures has great potential to clinical diagnosis. Herein, we propose a novel two-stage separation platform combining deterministic lateral displacement (DLD) with inertia which can achieve high-throughput, sheathless, and precise multi-target particle separation. The first-stage inertial unit, consisting of contraction–expansion arrays, was used for both separating the large particles and prefocusing the remaining particles. The second-stage DLD unit was then used to further separate medium and small particles. In particular, the inertial unit can also replace sheath flow in the DLD unit to prefocus and limit the entry position of the particle flow. Moreover, flow matching of the two-stage connection region has ensured that the input flow of the second stage meets the conditions for effective separation of the DLD unit. The structure parameters and input conditions of each unit were optimized based on the evaluation of separation performance by numerical simulation and particle experiment. The results show that continuous and rapid separation of 5 μm, 10 μm and 20 μm particles can be achieved with high efficiency (96.3 %, 94.7 % and 100 %) and high purity (98.65 %, 92.65 % and 85.5 %) based on the superposition of inertia and DLD units. Our two-stage separation platform is capable of high throughput operation while maintaining separation accuracy, which has strong practical significance in biological, clinical and point-of-care applications.

Heterostructure engineered membranes based on two-dimensional bimetallic MOF for enhanced remediation of dye contaminated wastewater

As a heterogeneous Fenton-like catalyst, two-dimensional (2D) bimetallic MOF can be readily engineered into lamellar membranes which integrate precise separation and Fenton-like degradation to enhance the elimination of organic contaminants from wastewater by rational design of interlayer spacing and constituent units. In this work, a 2D FeNi-MOF is assembled with ultrathin graphitic carbon nitride (g-C3N4) spacers into heterostructure membranes for enhanced remediation of dye contaminated wastewater by synergistic promotion of membrane separation and Fenton-like processes. For the establishment of heterostructure, FeNi-MOF and g-C3N4 nanosheets are alternately arranged by the coordination bonds between bimetallic nodes and pyridinic N to create orderly laminar nanochannels. On the one hand, the heterostructure provides abundant water passages and fixes the membrane interlayer distance to 1.0–1.2 nm with the permeation flux of 47.8–110.1 L·m2·h−1·bar−1. On the other hand, the heterostructure can act as the Fenton-like mediator to expedite the cycle efficiency of Fe(III)/Fe(II) and Ni(II)/Ni(III). The synergistic promotion mechanism of membrane separation and Fenton-like processes is elaborated by simulating the molecular transport peculiarity through membrane nanochannels and the electron transfer efficiency between dual active centers. The contaminant molecules are trapped within the membrane by specific or non-specific channel-guest interaction with heterostructure nanochannels while the steadily generated radicals attack and degrade the confined contaminants, reaching the dye removal rate of approximately 99.0%. Anchoring between adjacent layers and bimetallic cycle reaction in confined fluid confer the stability and recyclability to the heterostructure membrane under wide-range pH and pressures, which are promising for the sustainable treatment of dye contaminated wastewater.

Multi-layer encoder–decoder time-domain single channel speech separation

With the emergence of more advanced separation networks, significant progress has been made in time-domain speech separation methods. These methods typically use a temporal encoder–decoder structure to encode speech feature sequences, thereby accomplishing the separation task. However, due to the limitation of traditional encoder–decoder structure, the separation performance decreases sharply when the encoded sequence is short, and when encoded sequence is sufficiently long, the separation performance improves, but which leads to an increase in computational complexity and training cost. Therefore, this paper compresses and reconstructs the speech feature sequence through a multi-layer convolution structure, and proposes a multi-layer encoder–decoder time-domain speech separation model (MLED). In this model, our encoder–decoder structure can compress speech sequence to a short length while ensuring the separation performance does not decrease. And combined with our multi-scale temporal attention (MSTA) separation network, MLED achieves efficient and precise separation of short encoded sequences. Therefore, compared to previous advanced time-domain separation methods, our experiments show that MLED achieves competitive separation performance with smaller model size, lower computational complexity, and training cost.

Band separation and electric field prediction in square Bravais-Moiré photonic crystals

In this study, we address three key challenges in photonic crystals: modeling of isolated flat bands, electric field prediction, and band separation in dispersion relations. Using twisted square Bravais lattices at specific angles, we create Bravais-Moiré photonic crystals exhibiting unique characteristics. These include band pairing and parallelism in certain Brillouin zones, enabling predictable electric field behavior and identification of isolated, flat band pairs within extensive band gaps. We apply advanced Shape theory-based classification methods for precise band separation, offering significant contributions to photonics research and light manipulation applications.

АНАЛИЗ ПРОЧНОСТНЫХ ХАРАКТЕРИСТИК И ВАРИАТИВНОГО ИСПОЛНЕНИЯ ЭЛЕМЕНТОВ ГИДРОЦИКЛОНА ДЛЯ СОВЕРШЕНСТВОВАНИЯ ЕГО КОНСТРУКЦИИ

Promising directions for improving the efficiency of pyrite cinder separation for their further use in the production of Portland cement are considered. The object of the study is a digital model of a modified hydrocyclone with a separation area in the working area, which allows for precise separation of particles. The purpose of the study is to identify the appropriate design parameters of a modified hydrocyclone during strength calculations and variable execution of its model. Computer modeling of hydrodynamic processes during the creation of new equipment allows for an analysis of its operability, strength calculations and variable design of the device at the design stage, which is currently relevant. The changes in the efficiency of particle separation in a modified hydrocyclone depending on the varying geometric parameters in the working area of the apparatus are considered. The influence of the thickness of the sheets of the parts of the separation area has been studied and important aspects affecting the operating conditions of the device have been identified. Optimization of the geometry of the holes in the separating area of the hydrocyclone is proposed in order to capture more particles of the required fraction (size 60 microns or less). The resulting modified hydrocyclone design based on HCC-360-10 has significant application potential in various industries, including ore dressing, cement, petroleum, chemical industry and energy. The use of such a design can lead to a significant reduction in energy consumption, increased productivity and improved product quality. A method for static calculation of the strength of the separation region of a modified hydrocyclone using the finite element method in a CAD/CAE system is presented.

Precise Spectral Overlap-Based Donor-Acceptor Pair for a Sensitive Traffic Light-Typed Bimodal Multiplexed Lateral Flow Immunoassay.

Bimodal-type multiplexed immunoassays with complementary mode-based correlation analysis are gaining increasing attention for enhancing the practicability of the lateral flow immunoassay (LFIA). Nonetheless, the restriction in visually indistinguishable multitargets induced by a single fluorescent color and difficulty in single acceptor ineffectual fluorescence quenching due to the various spectra of multiple different donors impede the further execution of colorimetric-fluorescence bimodal-type multiplexed LFIAs. Herein, the precise spectral overlap-based donor-acceptor pair construction strategy is proposed by regulating the size of the nanocore, coating it with an appropriate nanoshell, and selecting a suitable fluorescence donor with distinct colors. By in situ coating Prussian blue nanoparticles (PBNPs) on AuNPs with a tunable size and absorption spectrum, the resultant APNPs demonstrate efficient fluorescence quenching ability, higher colloidal stability, remarkable colorimetric intensity, and an enhanced antibody coupling efficiency, all of which facilitate highly sensitive bimodal-type LFIA analysis. Following integration with competitive-type immunoreaction, this precise spectral overlap-supported spatial separation traffic light-typed colorimetric-fluorescence dual-response assay (coined as the STCFD assay) with the limits of detection of 0.013 and 0.152 ng mL-1 for ractopamine and clenbuterol, respectively, was proposed. This work illustrates the superiority of the rational design of a precise spectral overlap-based donor-acceptor pair, hinting at the enormous potential of the STCFD assay in the point-of-care field.

Analyzing the Phytochemistry and Bioactive Compounds of Abutilon indicum for antidiabetic activity Using TLC, HPTLC, GC-MS in Aqueous, Ethanol, and Chloroform Solvents for Pharmacognosy Determinations

In this systematic investigation of Abutilon indicum extracts for antidiabetic activity, using TLC and HPTLC were employed to analyze bioactive compounds. The ethanolic extract (EA) exhibited specific RF values: 0.16 for catechin, 0.57 for gallic acid, and 0.70 for quercetin, with Abutilon indicum (EA) containing the highest percentages—48.87% catechin, 27.45% gallic acid, and 7.25% quercetin. The robustly developed and validated HPTLC process, applied to ethanolic extracts, demonstrated clear bands and sharp peaks, ensuring precise separation of bioactive compounds. Similar methodologies were employed for chloroform extract (CA) and aqueous extract (AA), revealing RF values of 0.10, 0.36, and 0.54 for CA, and 0.087, 0.36, and 0.53 for AA, corresponding to catechin, gallic acid, and quercetin, respectively. Fingerprinting analysis confirmed the simultaneous presence of these compounds, highlighting the method's utility for quality control. Statistical analysis supported the reliability and cost-effective suitability of HPTLC for quantitative analysis in assessing herbal material and formulations. GC-MS exploration of Abutilon indicum extracts revealed over 20 compounds in each, including flavonoids, alkaloids, and terpenoids in the ethanolic extract, and phytosterols, alkaloids, and terpenoids in the chloroform extract. The aqueous extract displayed a diverse phytochemical composition, affirming medicinal potential. These results collectively endorse Abutilon indicum's versatility and therapeutic potential in herbal medicine and pharmaceutical formulations. Keywords Pharmacognosy, Bioactive Compounds, Analytical Study, Abutilon indicum etc

Polyamide Membranes with Tunable Surface Charge Induced by Dipole-Dipole Interaction for Selective Ion Separation.

Nanofiltration (NF) has the potential to achieve precise ion-ion separation at the subnanometer scale, which is necessary for resource recovery and a circular water economy. Fabricating NF membranes for selective ion separation is highly desirable but represents a substantial technical challenge. Dipole-dipole interaction is a mechanism of intermolecular attractions between polar molecules with a dipole moment due to uneven charge distribution, but such an interaction has not been leveraged to tune membrane structure and selectivity. Herein, we propose a novel strategy to achieve tunable surface charge of polyamide membrane by introducing polar solvent with a large dipole moment during interfacial polymerization, in which the dipole-dipole interaction with acyl chloride groups of trimesoyl chloride (TMC) can successfully intervene in the amidation reaction to alter the density of surface carboxyl groups in the polyamide selective layer. As a result, the prepared positively charged (PEI-TMC)-NH2 and negatively charged (PEI-TMC)-COOH composite membranes, which show similarly high water permeance, demonstrate highly selective separations of cations and anions in engineering applications, respectively. Our findings, for the first time, confirm that solvent-induced dipole-dipole interactions are able to alter the charge type and density of polyamide membranes and achieve tunable surface charge for selective and efficient ion separation.