High Separation Research Articles

Efficient Methane Purification Using a Robust and Recoverable Hydrogen‐Bonded Organic Framework

Efficient separation and purification of methane is a key step in promoting its wide application as an environmentally friendly energy carrier and an important chemical raw material. Development of single solid adsorbents simultaneously combining robust structure, high separation capacity, and easy performance recovery is highly desired but quite a challenge for realizing methane depuration. In the present study, we report an ultramicroporous hydrogen‐bonded organic framework compound constructed from a tetracyano bithiophene‐functionalized ligand. Similar to the acting principle of enzymes, multisite supramolecular interactions endow the material with not only extraordinary chemical stability in wide pH range including 12 M HCl and 20 M NaOH solutions but also highly selective recognition of acetylene and carbon dioxide over methane. The packing densities and adsorption selectivities toward acetylene and carbon dioxide are the highest reported for the hydrogen‐bonded organic framework materials. Dynamic breakthrough experiments demonstrate its highly efficient methane purification ability from binary and even ternary mixed gases, with not only methane productivities up to 2.34 mol kg‐1 but also moderate regeneration energy. Furthermore, the title compound can be easily regenerated in almost quantitative yield via simple rato‐evaporation of its dichloromethane solution once its activity is attenuated or lost.

Efficient Methane Purification Using a Robust and Recoverable Hydrogen-Bonded Organic Framework.

Efficient separation and purification of methane is a key step in promoting its wide application as an environmentally friendly energy carrier and an important chemical raw material. Development of single solid adsorbents simultaneously combining robust structure, high separation capacity, and easy performance recovery is highly desired but quite a challenge for realizing methane depuration. In the present study, we report an ultramicroporous hydrogen-bonded organic framework compound constructed from a tetracyano bithiophene-functionalized ligand. Similar to the acting principle of enzymes, multisite supramolecular interactions endow the material with not only extraordinary chemical stability in wide pH range including 12 M HCl and 20 M NaOH solutions but also highly selective recognition of acetylene and carbon dioxide over methane. The packing densities and adsorption selectivities toward acetylene and carbon dioxide are the highest reported for the hydrogen-bonded organic framework materials. Dynamic breakthrough experiments demonstrate its highly efficient methane purification ability from binary and even ternary mixed gases, with not only methane productivities up to 2.34 mol kg-1 but also moderate regeneration energy. Furthermore, the title compound can be easily regenerated in almost quantitative yield via simple rato-evaporation of its dichloromethane solution once its activity is attenuated or lost.

Magnetic Capture of Functionalized Nanoscale Zerovalent Iron for Soil Remediation: A Feasibility Study on Transport Control.

Nanoscale zerovalent iron (nZVI) has been proposed as a promising nanomaterial for soil remediation. However, injecting nZVI into contaminated sites to target and treat pollutant sources may pose potential environmental risks due to its colloidal stability and mobility in the environment. In this regard, this study assessed the feasibility of implementing magnetic capture of surface-functionalized nZVI in soil environments under the influence of the convective flow current. Here, functionalized nZVI particles were prepared by introducing carboxymethyl cellulose (CMC) as a stabilizing agent during the synthesis of nZVI by using the liquid-phase reduction method. The functionalized nZVI particles were then injected into a two-dimensional flow column containing a sand matrix with a high gradient magnetic trap (HGMT) embedded within the system. Particle transports in both the absence and presence of a magnetic field were recorded by using a digital camera, and the breakthrough curves were generated from the data collected spectrophotometrically. The results showed that the relative breakthrough concentration of nZVI decreased from 0.92 to nearly zero, with a delayed breakthrough time as the applied magnetic field strength increased from zero (no magnetic field) to 0.093 T, demonstrating a 100% capture efficiency. It was found that the magnetic capture for the nZVI particles was contributed by two mechanisms: (1) low gradient magnetic separation (LGMS), driven by the penetrating magnetic field from the permanent magnets, and (2) high gradient magnetic separation (HGMS), which occurred near the wire surfaces within the HGMT section magnetized by the permanent magnets. Findings in this work have proven the feasibility of magnetic separation as a control strategy for nanoparticle applications in environmental remediation.

Advanced Adaptive Protein Membrane with Super-High Flux and Precise Molecular Sieving of Dyes from Salts.

Precise separation of small organic molecules and electrolyte salts is critical for various industrial processes, necessitating advanced membranes with uniform pores. Proteins, as one typical nature polymer having the exactly same structure and molecular weight, offer a promising material for making such membranes. Here, hemoglobin (BHb) and lysozyme (Lyz) are utilized to fabricate precise nanofiltration membranes through amyloid-like co-assembly, triggered by Tris(2-carboxyethyl) phosphine. Molecular dynamics simulations reveal that BHb intercalates between Lyz molecules, enhancing tight assembly and reducing defects. The Lyz/BHb membrane exhibits a high void volume of 27.2% and achieves an exceptional permeance of 335 Lm-2h-1bar-1. Amazingly, the Lyz/BHb membrane achieves ultra-selective molecular sieving of dyes and salts with an unparalleled high separation factor of 1.25 × 103 for the NaCl/Brilliant blue. The unique adaptive separation layer is formed by anchoring dye molecules into the larger pores and thus narrowing down the pore size distribution and enhancing electrostatic repulsion, endowing the membrane with a distinctive molecular sieving of dyes and salts. This study offers valuable insights to finely tailor the pore structure of the membrane by co-assembly of proteins and to significantly enhance the membrane perm-selectivity by creating an adaptive protein separation layer with a unique molecular sieving property.

Self-assembled layer-by-layer deposition of ultrathin graphene membranes for high performance gas separation

Self-assembled layer-by-layer deposition of ultrathin graphene membranes for high performance gas separation

Efficient and Symmetric Temperature Control in Capillary Electrophoresis I: Tying Cooling Capillaries Around Analytical Capillaries.

The heat generated by the Joule effect during capillary electrophoresis (CE) runs creates radial temperature gradients in the separation medium. These temperature gradients cause zone dispersion in addition to molecular diffusion. This severely limits the field strengths that can be applied during the runs, especially when solutions with high ionic conductivity are used. This greatly increases run times, especially when high separation efficiencies are sought. In this work, the author proposes tying cooling capillaries (fused silica microtubes) along the external surface of the analytical capillary, allowing the circulation of coolants to efficiently and symmetrically control temperature in CE. The author deduced, step-by-step, the three master equations that serve as guidelines to produce a good match and tightly secure cooling capillaries along the outer surface of analytical capillaries. Additionally, an automated capillary tying machine was developed and demonstrated. Sets were produced with: four, five, and six cooling capillaries tied around one analytical capillary. The outer diameters of the capillaries used (one analytical and cooling) and the values of the remaining voids left between the first and last cooling capillary are in good agreement with the predictions of the three master equations deduced in this work. To the author's knowledge, this is the first time that cooling capillaries were tied around analytical capillaries to produce an efficient and symmetric cooling system for CE and toroidal capillaryelectrophoresis.

Molecular Dynamics Analysis of Li+/Mg2+ Transport Mechanism in COF Membranes with Flexible Oxygen-Containing Side Chains

Lithium is currently used in a wide range of portable electronic devices. With the rapid growth of the electric vehicle sector, lithium has become an essential resource. In this work, the influence of different lengths and types of oxygen-containing side chain in COF membranes on the Li+/Mg2+ separation performance were explored via molecular dynamic simulations. The transport mechanism was elucidated through analysis of the interaction mechanism, density distribution map, potential of mean force (PMF), and dehydration number of ions during their passage through the membranes. Simulation results indicate that COF-4EO membrane shows high separation performance for Li+/Mg2+ mixture, the flexible side chain of EO provides a jumping site for Li+ ions, and the transport energy barrier in the membrane for Li+ ions is low, which enhances the screening effect into the pore. Moreover, Mg2+ ions are more difficult to dehydrate water from their hydration layer and then enter into the membrane. This work would give some insight for designing of COF membranes with well ion separation performance.

Untwisting Strategy of MOF Nanosheets in Ultrathin Film Membrane for High Molecular Separation Performance.

Oriented 2D metal-organic framework (MOF) membranes hold considerable promise for industrial separation processes. Nevertheless, the lattice misalignment caused by the twisted stacking of 2D nanosheets reduces the in-plane pore size and exerts a significant impact on the membrane separation performance. Precisely regulating the stacking pattern of oriented 2D MOF membranes remains a significant challenge. Here, a scalable scrape-coating technique supplemented by a vapor untwisting strategy is proposed to directly construct non-twisted and ultrathin Zr-BTB membranes (Zr-BTB-M) on polyvinylidene fluoride (PVDF) substrates. The Zr-BTB nanosheets are induced to undergo lattice reorganization during the coating process, resulting in highly overlapped lattices and the largest in-plane pore channels. The exceptional butyl acetate selective adsorption capacity of non-twisted Zr-BTB, combined with its provision of highly ordered vertical penetrating pathways, significantly enhances molecular transport. After facile polydimethylsiloxane (PDMS) coating, the pervaporation separation index of the PDMS/Zr-BTB-M/PVDF membrane is found to be 9.74 times higher than that of conventional PDMS/PVDF membranes, paving the way for innovative, high-efficiency, energy-saving membrane separation technologies.

Facile Fabrication of Binary-Structured Fibrous Membranes with Antifouling and Flame-Retardant Properties for Durable Water/Oil Separation.

Membrane fouling from dispersed droplets during water/oil separation undermines performance and limits long-term use. Additionally, there is an urgent need for flame-retardant fibrous membranes capable of purifying high-temperature polluted oils. Inspired by the binary structure of taro leaves, this study introduces a novel fibrous membrane with both antifouling and flame-retardant properties for water/oil treatment. Eco-friendly cellulose acetate (CA) and multifunctional thermoplastic polyurethane (TPU) were used to construct a microfiber-based substrate membrane via electrospinning. A TPU/ammonium polyphosphate (APP) nanofiber layer with a beads-on-string structure was then electrosprayed onto the substrate as a functional layer. This binary-structured composite membrane leverages the adhesive properties of TPU within both the base microfibers and the functional nanofibers, enhancing stability and structural integrity. The functional layer's re-entrant structure effectively prevents dispersed droplets from adhering under the continuous phase, enabling efficient separation performance in both oil-in-water and water-in-oil emulsions. The membrane demonstrated strong antifouling properties and excellent recyclability, maintaining stable flux and a consistently high separation efficiency (>99.6%) across multiple cycles. Additionally, its flame-retardant properties allowed the membrane to self-extinguish when removed from direct flame. This study presents a novel strategy for fabricating multifunctional separation membranes, with detailed analysis of the underlying mechanisms.

Research Progress in Tritium Processing Technologies: A Review

Recent advancements in tritium separation technologies have significantly improved efficiency, particularly through the integration of vapor phase catalytic exchange (VPCE), liquid phase catalytic exchange (LPCE), and combined electrolysis catalytic exchange (CECE) methods. Combining these techniques overcomes individual limitations, enhancing separation efficiency and reducing energy consumption. The CECE process, which integrates electrolysis with catalytic exchange, offers high separation factors, making it effective for high-concentration tritiated water treatment. Solid polymer electrolyte (SPE) technology has also gained prominence for its higher efficiency, smaller equipment size, and longer lifespan compared to traditional alkaline electrolysis. While electrolysis offers high separation factors, its high energy demand limits its cost-effectiveness for large-scale operations. As a result, electrolysis is often combined with other methods like CECE to optimize both energy consumption and separation efficiency. Future research will focus on improving the energy efficiency of electrolysis for large-scale, low-cost tritiated water treatment.

Exceptional anti-fouling, self-cleaning and high-flux ZIF-8@polyacrylonitrile based nanofiber composite membrane via in situ growth of seaweed-like ZnIn2S4 for efficient separation of emulsified oily wastewater.

The membrane separation technique encounters the problems of low permeability and weak anti-fouling ability during the large-scale treatment of emulsified oily wastewater. To address this issue, the high-flux and photocatalytic self-cleaning polyacrylonitrile (PAN)-based nanofiber composite membrane (ZnIn2S4/ZIF-8@PAN) was constructed via the electrospinning of PAN@ZIF-8 nanofiber membrane with rivet-like structure and in situ growth of highly porous seaweed-like ZnIn2S4 in the hydrothermal process. The intrinsic hydrophilicity, porous and hierarchical structure of ZnIn2S4 effectively regulated the transport channel, superhydrophilic/underwater superoleophobic feature (WCA: ∼ 0 °, UOCA: up to 155.9 °), and ultra-low oil adhesion behavior of composite membrane, thus achieving superior separation flux of diverse surfactant-stabilized O/W emulsions (up to 5062.7 ± 189.4 L·m-2·h-1) and separation efficiency of 99.11 ± 0.18 %. As evidenced by the results of Hermia model and dynamic oil adhesion experiment, the ZnIn2S4/ZIF-8@PAN composite membrane displayed exceptional oil resistance and anti-fouling ability under harsh conditions, retaining its high separation efficiency (separation flux: 4408.1 L·m-2·h-1, rejection rate: 99.03 %) for O/W emulsions after 10 consecutive separation cycles. Furthermore, we discovered that the composite membrane offered favorable self-cleaning performance towards photocatalytic degradation of various organic dyes under exposure to visible light, with degradation efficiency up to 96.88 % within 120 minutes. The DFT calculation, EIS impedance, and free radical inhibition experiments demonstrated that the well-matched band structure and intimate contact interface between ZIF-8 and ZnIn2S4 facilitated the efficient transfer and separation of photo-induced charge carriers. Such PAN multifunctional composite membrane has great potential in the field of complex oily wastewater treatment.

Genomic clustering tendency of transcription factors reflects phase-separated transcriptional condensates at super-enhancers.

Many transcription factors (TFs) have been shown to bind to super-enhancers, forming transcriptional condensates to activate transcription in various cellular systems. However, the genomic and epigenomic determinants of phase-separated transcriptional condensate formation remain poorly understood. Questions regardingwhich TFs tend to associate with transcriptional condensates and what factors influence their association are largely unanswered. Here we systematically analyzed 571 DNA sequence motifs across the human genome and 6650 TF binding profiles across different cell types to identify the molecular features contributing to the formation of transcriptional condensates. We found that the genomic distributions of sequence motifs for different TFs exhibit distinct clustering tendencies. Notably, TF motifs with a high genomic clustering tendency are significantly associated with super-enhancers. TF binding profiles showing a high genomic clustering tendency are further enriched at cell-type-specific super-enhancers. TFs with a high binding clustering tendency also possess high liquid-liquid phase separation abilities. Compared to nonclustered TF binding, densely clustered TF binding sites are more enriched at cell-type-specific super-enhancers with higher chromatin accessibility, elevated chromatin interactionand stronger association with cancer outcomes. Our results indicate that the clustered genomic binding patterns and the phase separation properties of TFs collectively contribute to the formation of transcriptional condensates.

Capillary Electrophoresis-Mass Spectrometry for Top-Down Proteomics.

Mass spectrometry (MS)-based top-down proteomics (TDP) characterizes proteoforms in cells, tissues, and biological fluids (e.g., human plasma) to better our understanding of protein function and to discover new protein biomarkers for disease diagnosis and therapeutic development. Separations of proteoforms with high peak capacity are needed due to the high complexity of biological samples. Capillary electrophoresis (CE)-MS has been recognized as a powerful analytical tool for protein analysis since the 1980s owing to its high separation efficiency and sensitivity of CE-MS for proteoforms. Here, we review benefits of CE-MS for advancing TDP, challenges and solutions of the method, and the main research areas in which CE-MS-based TDP can make significant contributions. We provide a brief perspective of CE-MS-based TDP moving forward.

Multi-Vortex Regulation in a Simple Semicircular Microchannel with Ordered Micro-Obstacles for High-Throughput Buffer Exchange.

Microfluidics is an emerging technology for buffer exchange in bioprocessing applications. However, achieving buffer exchange with simplicity of operation and high throughput in a straightforward channel design remains a challenge. This study presents a novel semicircular microchannel design that allows for the deterministic regulation of helical and Dean vortices through geometric confinement. By incorporating micro-obstacles into semicircular microchannels with large dimensions (900 μm wide and 100 μm high), we observe a substantial enhancement in secondary flows, leading to a unique fluid distribution across a wide range of flow rates. This design enables a high particle separation efficiency (>96.27%) coupled with a low fluorescein purity (<4.46%) at a high throughput of 3 × 106 particles/min. The proposed methodology, characterized by ease of production (simple semicircular microchannels with large dimensions), user-friendly operation (uniform flow rates in both sheath and sample inlets), and efficient buffer exchange capabilities (typically 3 mL min-1), demonstrates significant potential for advancing microfluidic systems in biological and biomedical research.

Advances and Applications of Capillary Electrophoresis Mass Spectrometry in Food Analysis: Strategies for Online and Offline Preconcentration.

Advancements in food technology have increased the need for thorough analysis to ensure food safety, quality, and compliance with regulatory requirements. Capillary electrophoresis-mass spectrometry (CE-MS) has emerged as a powerful tool in food analysis due to its high separation efficiency, low sample consumption, and ability to handle complex matrices. However, challenges such as the use of volatile running buffers and maintaining the stability of the electrical circuit connecting the CE and MS systems have been addressed through advancements in interface designs, such as sheathless systems and optimized sheath-liquid compositions. Online and offline preconcentration techniques have significantly enhanced CE-MS sensitivity (up to 1000-fold) through stacking methods such as large volume sample stacking (LVSS) and dynamic pH junction stacking. Meanwhile, offline sample preparation techniques, such as solid-phase extraction (SPE) and liquid-based methods, are essential for removing matrix interferences and preconcentrating targeted analytes. This review explores both online and offline preconcentration methods and emphasizes the importance of CE-MS in helping researchers develop effective strategies for selecting the best preconcentration methods for food analysis.

Anion‐π Interactions on Functionalized Porous Aromatic Cages for Gold Recovery from Complex Aqueous with High Capacity

High capacity, selective recovery and separation of precious metals from complex aqueous solutions is essential but remains a challenge in practical applications. Here, we prepared a thiophene‐modified aromatic porous organic cage (T‐PAC) with high stability for precise recognition and recovery of gold. T‐PAC exhibits an outstanding gold uptake capacity of up to 2260 mg/g with fast adsorption kinetics and high adsorption selectivity. It's also used to selectively recover gold from a variety of complex aqueous solutions in a stable and efficient manner. The theoretical calculations and dedicated experiments suggest that anion‐π interactions between the [AuCl4]‐ and TFP fractions on T‐PAC cooperated with S/N boning and redox effects play the decisive role in the highly efficient gold recovery performance.

Parameter Pool-Assisted Centrifugation Sorter for Multiscale Higher-Order DNA Nanomaterials.

Higher-order DNA nanomaterials have emerged as programmable tools for probing biological processes, constructing metamaterials, and manipulating mechanically active nanodevices with the multifunctionality and high-performance attributes. However, their utility is limited by intricate mixtures formed during hierarchical multistage assembly, as standard techniques like gel electrophoresis lack the resolution and applicability needed for precise characterization and enrichment. Thus, it is urgent to develop a sorter that provides high separation resolution, broad scope, and bioactive functionality. Here, we present a versatile and scalable sorting pipeline based on a centrifugation parameter pool capable of distinguishing DNA nanomaterials across multiple scales. By tuning parameters, we achieved high-throughput classification of nanostructures, spanning from DNA tile-based constructs to DNA origami-based assemblies (∼50 MDa, 75,000 bp), surpassing conventional methods. Furthermore, we optimized the separation resolution to less than 78 kDa (∼120 bp) at a large scale by sorting DNA tetrahedron structures using this systematic parameter pool-assisted centrifugation strategy. This sorter maintains the integrity and functionality of bioactive materials, facilitating a seamless transition from assembly to application, allowing for integration with proteins and other components to achieve the fabrication of complex functional materials and programmable molecular machines across interdisciplinary fields within the nanotechnology community.

Determination of Saccharides in Cottonseed Processing Waste Liquid and By-Products by High Performance Liquid Chromatography with Evaporative Light Scattering Detection (HPLC-ELSD)

A method utilizing high-performance liquid chromatography with evaporative light scattering detection (HPLC-ELSD) has been developed and validated for the simultaneous determination of raffinose, glucose, sucrose, and stachyose in waste liquid from cottonseed processing and in byproducts including cottonseed meal. The separation was performed using a carbohydrate ES column (250 × 4.6 mm, 5 μm) and isocratic elution with acetonitrile and water (70:30, v/v). The temperature of the column oven was maintained at 35 °C. The drift tube temperature for evaporative light scattering detection (ELSD) was operated 40 °C, while the nitrogen flow was set to 1.5 L·min−1. The saccharides were separated by HPLC-ELSD within 20 min. The coefficients of determination (R 2 = 0.9986–0.9999) indicate that there was a linear relationship between saccharides and the response. The limits of detection were 0.004–0.023 mg·mL−1 and the quantification range was from 0.013 to 0.080 mg·mL−1. The intraday and interday precision were from 0.05 to 0.55% and 0.20 to 0.58%, respectively. The recovery was from 102.75 ± 2.03% to 106.76 ± 2.09% and the relative standard deviations were 1.87 to 1.98%. The method exhibited good stability in determining four saccharides in cottonseed processing waste liquid and the resultant byproduct cottonseed meal. This method exhibits high separation efficiency and sensitivity, excellent precision, and simplicity, which allows determination of the high value-added product, raffinose, in cottonseed processing waste liquid and meal.

Improving high gradient magnetic separation performance by a fine-coarse feeding strategy

Improving high gradient magnetic separation performance by a fine-coarse feeding strategy

A Novel S-scheme Heterojunction based on BiPO4/CdPSe3 for Effective Photocatalytic Degradation of Organic Pollutants

As a sustainable technology that can be utilized for degrading organic pollutants, photocatalysis becomes more and more important in the environment pollution control. One crucial factor that influences the degradation process is the design of photocatalyst. In this study, we utilized a simple hydrothermal method, liquid exfoliation and mechanical mixture to synthesize a novel S-scheme heterojunction based on BiPO4/CdPSe3. It was found that the optimal molar ratio BiPO4: CdPSe3= 2: 1 (noted as B2C) gave rise to an efficient removal of rhodamine B up to 97.5% after 30min dark reaction and 60min light exposure. This composite also possesses the degradation capacity for other antibiotics and inorganic pollutant. The capture experiments showed that superoxide radicals played the dominant role in the degradation process. Besides, hydroxyl radicals and holes were also important active species. The high photocatalytic degradation performance of B2C could be attributed to the increased specific surface area with more active sites, enhanced light absorption in the visible region, and, more importantly, the special S-scheme heterostructure for high photogenerated charge carrier separation, synergistically improved the photocatalyst degradation efficiency. This work provides a new perspective for designing high-efficient photocatalysts applicable in multiple organic and inorganic pollutants degradation.