Separation Performance Research Articles

Preparation of a 6FDA-DAM/ODA Mixed Matrix Membrane Doped with MOFs and Its Application in Gas Separation.

Mixed matrix membranes (MMMs) can significantly improve gas separation performance, but the type and state of the filler in the membrane matrix are key indicators for the development of MMMs. Therefore, in this work, 6FDA-DAM/ODA (1:1), metal-organic frameworks (MOFs) with different particle sizes (UiO-66 and UiO-66-NH2) were synthesized, and then MOFs were doped into 6FDA-DAM/ODA to prepare MMMs. The effects of the dopant materials and their particle sizes on the gas separation performance of the membranes were investigated by testing the permeability of the MMMs to H2, CO2, CH4, and N2. When the dopant material was UIO-66, the permeability and selectivity of MMMs for each gas were significantly improved compared with that of the original membrane; when the dopant material was 300 nm UIO-66-NH2 with a loading of 10 wt %, the permeability performance and the CO2/CH4 selectivity increased from 44.1 to 57.2 compared with that of the original membrane. The permeation performance for CO2, N2, and H2 and the selectivity for CO2/N2, H2/N2, and H2/CH4 were also significantly improved. In terms of comprehensive separation performance, doping 300 nm UiO-66-NH2 was better than doping 70 and 400 nm UiO-66-NH2 and also showed excellent performance in 50:50 (vol/vol) CO2/CH4 binary mixed gas separation. This work provides an idea for the fabrication of MMMs for high-performance gas separation.

Sex Differences in Early/Unplanned Separation Among US Service Members With a History of Mild Traumatic Brain Injury.

To investigate the incidence of early/unplanned (E/U) separations following mild traumatic brain injury (mTBI) and assess whether sex impacts the hazard of separation. Military Health System (MHS). Active duty service members (N=75,730) with an initial mTBI diagnosis in military records between January 2011 and January 2018. Retrospective cohort study of electronic health records in the MHS. Cause-specific Cox proportional hazards models were used with sex at birth as the primary predictor. Early/unplanned (E/U) separation, defined as military separation attributed to disability, misconduct, poor performance, death, or other medical circumstances, within 2 years following the initial mTBI. Incidence of E/U separation within 2 years following mTBI was 13.7% (11.0% in women and 14.2% in men). Disability and misconduct separations were most common. Female service members had lower adjusted hazards for any E/U separation (Hazard Ratio [HR]=0.65; 95% Confidence Interval [CI]: 0.61,0.69), disability separation (HR=0.71; 95% CI: 0.65, 0.78), misconduct separation (HR=0.40; 95% CI: 0.36, 0.45), and poor performance separation (HR=0.84; 95% CI: 0.72, 0.99), compared to males, but had higher adjusted hazards for separations due to other medical circumstances (HR=1.24; 95% CI: 1.04, 1.48). Male and female service members had different hazards of E/U separation following mTBI. Separating early may increase the risk of adverse health and socioeconomic outcomes, so additional research is needed on why these separations occur and why they may be impacting men and women differently.

Optimization of the Matrix in a Transverse-Field High-Gradient Magnetic Separator for an Improved Ilmenite Separation

Transverse-field high-gradient magnetic separators (HGMSs) are an important complement to longitudinal-field HGMSs in mineral processing due to their several advantages. However, the processing capacity of the transverse-field HGMS is smaller than that of the longitudinal-field HGMS. Consequently, research on the optimization of the matrix box for improving the processing capacity is essential. This work investigates the optimization of the matrix box for the SSS® HGMS to enhance the ilmenite separation efficiency and processing capacity. The results show that the matrix’s influence on separation performance is primarily influenced by the diameter of the rod matrix, the filling ratio, the depth of the matrix in the direction of slurry flow, and the ore unloading efficiency. Ilmenite pre-concentration tests are carried out using a test sample ore from Panzhihua, China. Pilot-scale validation research is carried out. The test results indicate that the depth of the matrix box should not be considerably thick, as an excessive number of layers increases the capture zone, but simultaneously reduces the unloading efficiency. The depth of the matrix box should neither be considerably thick nor particularly thin, as this would result in low processing capacity. Meanwhile, the segmented multi-layer matrix box should be used to balance the capturing and unloading performance. Finally, an optimal double-layer matrix ring is applied to the industrial transverse-field HGMS, and its inner and outer rings are equipped with matrix boxes with ϕ3 mm and ϕ2 mm rods, respectively, which improves its pre-concentrate efficiency and processing capacity. The concentrate indexes of the transverse-field HGMS is achieved with a TiO2 grade of 18.01% and a recovery of 87.28%, which is better than the separation indexes of the longitudinal-field HGMS.

Functional flexible adsorbents and their potential utility.

Physisorbents are poised to address global challenges such as CO2 capture, mitigation of water scarcity and energy-efficient commodity gas storage and separation. Rigid physisorbents, i.e. those adsorbents that retain their structures upon gas or vapour exposure, are well studied in this context. Conversely, cooperatively flexible physisorbents undergo long-range structural transformations stimulated by guest exposure. Discovered serendipitously, flexible adsorbents have generally been regarded as scientific curiosities, which has contributed to misconceptions about their potential utility. Recently, increased scientific interest and insight into the properties of flexible adsorbents has afforded materials whose performance suggests that flexible adsorbents can compete with rigid adsorbents for both storage and separation applications. With respect to gas storage, adsorbents that undergo guest-induced phase transformations between low and high porosity phases in the right pressure range can offer improved working capacity and heat management, as exemplified by studies on adsorbed natural gas storage. For gas and vapour separations, the very nature of flexible adsorbents means that they can undergo induced fit mechanisms of guest binding, i.e. the adsorbent can adapt to a specific adsorbate. Such flexible adsorbents have set several new benchmarks for certain hydrocarbon separations in terms of selectivity and separation performance. This Feature Article reviews progress made by us and others towards the crystal engineering (design and control) of flexible adsorbents and addresses several of the myths that have emerged since their initial discovery, particularly with respect to those performance parameters of relevance to natural gas storage, water harvesting and hydrocarbon gas/vapour separation.

Optimizing the quality of acoustophoretic separation by the in-flow mobility-ratio method

Achieving good acoustic particle or cell separation performance requires skilled operators, who must carefully fine-tune the input parameters (actuation voltages, flow rates, and flow split ratios). Often the fine-tuning is done by time-consuming parameter sweeps, which are tedious and expensive. Here, we present a straightforward model-based approach to determining input parameters that yield optimal separation performance. The optimal parameters are a function of the device performance, the material properties of the separation species (compressibility, density, size), and the properties of the buffer (compressibility and density). The device performance is assessed by a calibration step, while the material properties are combined into the mobility ratio and measured by the in-flow mobility-ratio method, which is introduced in this work. The optimal separation settings are validated by separating green fluorescent 7.8-μm particles from red fluorescent 4.9-μm particles. Published by the American Physical Society 2025

Novel Collector of a Dodecylpyridinium Chloride Ionic Liquid in the Reverse Flotation Separation of Muscovite from Apatite.

Reverse flotation separation of muscovite from apatite using a dodecylpyridinium chloride (DPDC) ionic liquid as the collector was studied in this work. The microflotation results depicted that DPDC had a strong collecting for muscovite but had a slight collecting for apatite when using phosphoric acid as a depressant for apatite in a weakly acidic pH value pulp, artificial mixture mineral flotation showed that reverse flotation separation of muscovite from apatite can be effectively achieved in the reagent scheme of phosphoric acid/DPDC, and DPDC had a better separation performance in the muscovite/apatite system than DDA. The adsorption measurements indicated that the adsorption amount of DPDC on the apatite surface was less than that of DPDC on the muscovite surface, and the zeta potential results confirmed that a strong interaction occurred between DPDC and the muscovite surface, while an extremely weak interaction occurred between DPDC and the apatite surface in the presence of phosphoric acid at pH ∼ 5.5. XPS analysis indicated that a hydrogen bond occurred between DPDC and the muscovite surface. Thus, it was inferred that DPDC could be used as an appreciation collector for the reverse flotation of muscovite from apatite.

Pulsatile Ion Transport in Nanofiltration Membranes Coupled with Electrically Tunable Pore and Hydroxyl Electrostatic Interactions.

Pulsatile ion transport facilitates the adjusted transfer of substances, meeting the requirements for the gradient and timed separation of multiple components in membrane processes. Responsive nanofiltration membranes are thus currently receiving widespread attention but face limitations due to their narrow performance adjustment range. Herein, hydroxyl functional groups were introduced into electrically responsive nanofiltration membranes to broaden the adjustment range of separation performance through a combination of pore size sieving and functional group interactions, resulting in a greater change in rejection and flux compared to the original membrane. Membrane pore size is regulated by polypyrrole volume changes and becomes more variable when the cation's hydration radius is smaller. Although the hydroxyl group did not affect the charge transfer or volume change capacity of polypyrrole, it enhanced ion-pore interactions during ion transport, which was particularly pronounced in smaller nanochannels. The size effect of functional group interactions more strongly enhances the transmembrane energy barrier in the reduced state compared with the oxidized state, ultimately resulting in greater modulation of performance. This coupling strategy provides insights into the design of responsive membranes, offering the potential to achieve gradient separation of various solutes.

Superhydrophobic and Self-Healing Porous Organic Macrocycle Crystals for Methane Purification under Humid Conditions.

Purifying methane from natural gas using adsorbents not only requires the adsorbents to possess excellent separation performance but also to overcome additional daunting challenges such as humidity interference and durability requirements for sustainable use. Herein, porous organic crystals of a new macrocycle (CaC9) with superhydrophobic and self-healing features are prepared and employed for the purification of methane (>99.99% purity) from ternary methane/ethane/propane mixtures under 97% relative humidity. The high selectivity for methane and water-resistance are attributed to the unique chemical structure of CaC9, possessing an intrinsic 4.2 Å pore along with a pore environment modified with saturated alkyl chains. Besides, CaC9 crystals exhibit a self-healing capacity to realize in situ reconstruction of porosity within 15 min. The transformation of CaC9 crystals from a nonporous state to a porous state can be easily achieved upon treatment with n-hexane vapor, thereby presenting a novel solution to enhance the sustainable separation processes of porous materials. This work introduces a novel molecular-level porous adsorbent for natural gas separation, providing a valuable impetus for designing novel adsorbents with unexpected functions.

Enhanced Separation and Anti-biofouling Performance of Polysulfone Ultrafiltration Membrane Surface-Grafted with Phytic Acid/Silver Ion Complex Aggregates

Enhanced Separation and Anti-biofouling Performance of Polysulfone Ultrafiltration Membrane Surface-Grafted with Phytic Acid/Silver Ion Complex Aggregates

Multiparametric Study of Water–Gas Shift and Hydrogen Separation Performance in Membrane Reactors Fed with Biomass-Derived Syngas

A multiparametric study was conducted on a hydrogen (H2) production rig designed to process 0.25 Nm3·h−1 of syngas. The rig consists of two Pd-Ag membrane permeator units and two Pd-Ag membrane reactor units for the water–gas shift (WGS) reaction, enabling a detailed and comprehensive analysis of its performance. The aim was to find the optimal conditions to maximize hydrogen production by WGS and its separation in a pure stream by varying the temperature, pressure, and steam-to-CO ratio (S/CO). Two syngas mixtures obtained from an updraft gasifier using different gasification agents (air–steam and oxy–steam) were used to investigate the effect of gas composition. The performance of the rig was investigated under nine combinations of temperature, pressure, and S/CO in the respective ranges of 300–350 °C, 2–8 bar, and 1.1–2 mol·mol−1, as planned with the help of design of experiment (DOE) software. The three parameters positively affected performance, both in terms of capacity to separate a pure stream of H2, reported as moles permeated per unit of surface area and time, and in producing new H2 from WGS, reported as moles of H2 produced per volume of catalyst unit and time. The highest yields were obtained using syngas from oxy–steam gasification, which had the highest H2 concentration and was free of N2.

Titanium Dioxide (TiO2) Incorporation into Poly(ether sulfone) (PES) Hollow Fiber Membranes (HFMs) Improves Biocompatibility and Separation Performance for Bioartificial Kidney (BAK) and Hemodialysis Applications.

Hemodialysis and bioartificial kidney (BAK), which mimic both physical and biological functions, can significantly impact chronic kidney disease (CKD) patients. Here we report on Hollow fiber membranes (HFMs) with enhanced separation of uremic toxins along with enhanced hemocompatibility and biocompatibility that also promote the growth of kidney cells. The improvement arises from the addition of titanium dioxide (0.1, 0.5, 2%) into poly(ether sulfone) (PES) HFMs during fiber spinning, resulting in enhanced growth and proliferation of HEK293 cells, which were able to form spheroids as evidenced by the confocal images. MTT cell viability assay, cell proliferation assay by cell count, live dead assay by flow cytometry, and reactive oxygen species (ROS) study showed metabolically active viable cells, a higher number of cells, and a low ROS level in TiO2 PES HFMs. The ultrafiltration coefficients of HFMs were high, with the highest (152.86 ± 5.01 mL/(m2·h·mmHg)) being for 2% TiO2 PES (2TiP), showing the enhanced separation performance and better hemocompatibility (<5% hemolysis limit), and the lowest being for 2TiP (0.057%), with a low value of complement activation and lowest SC5b-9 marker level (10.71 ng/mL). HFMs also showed enhanced separation of toxins such as urea, creatinine, lysozyme, and indoxyl sulfate, proving their capability to remove water-soluble, middle molecular weight and protein-bound toxins. Therefore, the TiO2-incorporated membranes developed here have promise for hemodialysis and BAK applications.

Dehydration-enhanced Ion Recognition of Triazine Covalent Organic Frameworks for High-resolution Li+/Mg2+ Separation.

The precise and rapid extraction of lithium from salt-lake brines is critical to meeting the global demand for lithium resources. However, it remains a major challenge to design ion-transport membranes with accurate recognition and fast transport path for the target ion. Here, we report a triazine covalent organic framework (COF) membrane with high resolution for Li+ and Mg2+ that enables fast Li+ transport while almost completely inhibiting Mg2+ permeation. The remarkably high rejection of Mg2+ by the COF membrane is achieved via imposed ion dehydration and the construction of the energy well. The proper hydrophilic environment of the COF channel promotes the dissociation of Li+ from the negatively charged functional groups, allowing Li+ for hopping transport supported by the sulfonate side-chains to shorten the diffusion path of Li+. Under high-salinity electrodialysis conditions, the COF membrane demonstrates robust Li+/Mg2+ separation performance (No Mg2+ were detected in the collected solution), achieving efficient lithium recovery and high product purity (Li2CO3: 99.3%). This membrane design strategy enables high energy efficiency and powerful lithium extraction in the electrodialysis lithium extraction process, and can be generalized to other energy and separation related membranes.

Synthesis of a fluorophilic magnetic microporous organic network for selective enrichment of fipronil and ethiprole in milk and egg samples.

Considering the widespreadly use, large consumption, and serious environmental and health threats of phenylpyrazole insecticides (PPIs), development of a selective and sensitive method for accurate detection of their residuals in food samples is of great significance and challenging. Herein, depending on the hydrophobic and F-containing characteristics of PPIs, a novel fluorinated magnetic microporous organic network (FMMON) was designed and prepared for efficient and selective magnetic solid-phase extraction (MSPE) of two typical PPIs (fipronil and ethiprole) from milk and egg samples before the HPLC-UV determination. FMMON owned large specific surface area, multiple interaction sites, excellent magnetic separation performance and stability and exhibited good extraction and selectivity for fipronil and ethiprole through the specific F-F, hydrogen bonding, hydrophobic, and π-π interactions. Under optimal extraction conditions, the established FMMON-MSPE-HPLC-UV method provided wide linear ranges (0.1-1000 µg L-1), low limits of detection (0.03-0.05 µg L-1), large enrichment factors (96.2-99.7), low adsorbent consumption (4 mg), and short extraction time (6 min) for fipronil and ethiprole. This work revealed the bright future of fluorinated MONs in sample pretreatment of fluorinated contaminants in complex substrates.

Tuning Fluorination of Carbon Molecular Sieve Membranes with Enhanced Reverse-Selective Hydrogen Separation From Helium.

Membrane technology has been explored for separating helium from hydrogen in natural gas reservoirs, a process that remains extremely challenging due to the sub-Ångstrom size difference between H2 and He molecules. Reverse-selective H2/He separation membranes offer multiple advantages over conventional helium-selective membranes, which, however, suffer from low H2/He selectivity. To address this hurdle, a novel approach is proposed to tune the ultra-micropores of carbon molecular sieves (CMS) membranes through fluorination of the polymer precursor. By incorporating -CF3 units into the backbone of Tröger's base polymers, the microporosity of CMS is tailored and reverse-selective H2/He CMS membranes are deployed with remarkable separation performance, surpassing most reported membranes. These CMS membranes exhibit a H2 permeability of 1505.2 Barrer with a notable H2/He selectivity of 3.8. Barometric sorption tests reveal preferential sorption of H2 over He in the fluorinated CMS membranes, which also demonstrate a significantly higher H2/He diffusion selectivity compared to unfluorinated samples. Material studio calculations indicate that the "slim" hydrogen molecule penetrates ultra-micropores more readily than the spherical He molecule, thus achieving reverse H2/He selectivity. This design approach offers a promising pathway for developing molecularly sieving membranes to tackle the challenging helium separation from natural gas.

Numerical simulations on the separation performance of two-stage mini hydrocyclones connected in series

ABSTRACT Conventional hydrocyclones (CHCs) exhibit limited effectiveness in separating fine oil droplets from produced fluids, constraining overall oil-water separation efficiency. Mini hydrocyclones (MHCs) with smaller main diameter can further enhance the separation efficiency of fine oil droplets. This study constructs a two-stage series separation system using two individual MHCs. Simulations were conducted to investigate the effects of split ratio, water content, and oil droplet size on the separation performance. The adaptability of the series system to these parameters was thereby obtained. Results indicate the optimal separation efficiency is achieved when the total split ratio of the series system is 48%. The two-stage series system has better adaptability to the water content, and the separation efficiency keeps more than 97% when the water content is 86–98%, while the separation efficiency is lower than 92% when the water content is 86% in a single-stage MHC. When the inlet oil concentration exceeds 10%, for oil droplet sizes less than 0.15 mm, the two-stage series system outperforms single-stage MHCs operating independently.

Atomically Fine-Tuning Organic-Inorganic Carbon Molecular Sieve Membranes for Hydrogen Production.

Polymeric membranes with great processability are attractive for the H2/CO2 separation required for hydrogen production from renewable biomass with carbon capture for utilization and sequestration. However, it remains elusive to engineer polymer architectures to obtain desired sub-3.3 Å ultramicropores to efficiently sieve H2 from CO2. Herein, we demonstrate a scalable way of carbonizing polybenzimidazole (PBI) at low temperatures, followed by vapor phase infiltration (VPI) to atomically narrow ultramicropores throughout the films, forming hybrid organic-inorganic carbon molecular sieves (CMSs). One VPI cycle (100 s) for the PBI carbonized at 500 °C remarkably increases H2/CO2 selectivity from 9.6 to 83 at 100 °C, surpassing Robeson's upper bound. The CMS demonstrates a stable H2/CO2 separation performance when challenged with simulated syngas streams and can be fabricated into thin-film composite membranes, outperforming state-of-the-art membranes. The scalable approach can be ubiquitous to molecularly fine-tune ultramicropores of leading polymeric membranes to further improve their size-sieving ability and thus separation efficiency.

One-Step Ethylene Purification from Ternary Mixture through Adaptive Recognition Sites.

One-step adsorptive purification of ethylene (C2H4) from ternary mixture comprising of acetylene (C2H2), ethylene (C2H4) and carbon dioxide (CO2) is a great challenge in the chemical industry. Herein, a microporous metal-organic framework (FJI-H38) has been reported, whichpossesses a high density of electronegative O/N binding sites and appropriate pore size. Notably, at 0.01 bar and 298 K FJI-H38 shows excellent trapping capability for C2H2 (1.64 mmol/g) and CO2 (2.33 mmol/g), while the uptake of C2H4 is only 0.41 mmol/g, which endows FJI-H38 high C2H2/C2H4 selectivity and top-level CO2/C2H4 simultaneously. Polymer-grade C2H4 (≥99.95%) with record-high productivity can be successfully obtained from ternary C2H2/CO2/C2H4 mixture in one step under various conditions. Even at 318 K, the separation performance has no obvious decrease. Such excellent separation performance is due to the adaptive recognition of C2H2 and CO2 by FJI-H38 through the synergistic effect of appropriate pore size and the match of electrostatic potentials, where C2H2 and CO2 can be stabilized by the O/N and aromatic ring sites.

Preparation of halloysite nanotube-based monolithic column for small molecules and protein analysis.

s: This study aimed to prepare a new separation medium, silane coupling agent KH570- modified halloysite nanotube (MPS-HNT) monolithic column, with excellent separation performance for small molecular compounds and macromolecular proteins. This was prepared using the principle of redox polymerization with modified HNTs as monomers. The optimal monomer proportion was obtained by optimizing the ratio of monomer, cross-linker, and pore-forming agent, which was evaluated using scanning electron microscopy, nitrogen adsorption, and mercury intrusion. The monolithic column exhibited a relatively homogeneous pore structure and good separation performance and permeability. As a high-performance liquid chromatography stationary phase, six small aromatic molecules were successfully separated in 6min with a theoretical plate count of 35, 640 plates m-1 for benzene. Twenty-one peaks were separated from the fermentation mattress extract containing lipopeptide antibiotics on the MPS-HNT column. The separated chromatographic peaks further identified three lipopeptide antibiotics using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis. Twelve chromatographic peaks were isolated from chicken egg whites, and the eighth peak was identified as the lysozyme. The methodological validation of the lysozyme in chicken egg white showed that the linear correlation coefficient was 0.9996. The intraday and inter-day relative standard deviations were 3.1-4.0% and 1.9-3.4%, respectively. The spike recovery rate of lysozyme was 94.20-103.31%. The overall column displayed good stability: the relative standard deviations of the peak area of six aromatic compounds and retention time were<3.28%.

One‐Step Ethylene Purification from Ternary Mixture through Adaptive Recognition Sites

One‐step adsorptive purification of ethylene (C2H4) from ternary mixture comprising of acetylene (C2H2), ethylene (C2H4) and carbon dioxide (CO2) is a great challenge in the chemical industry. Herein, a microporous metal‐organic framework (FJI‐H38) has been reported, which possesses a high density of electronegative O/N binding sites and appropriate pore size. Notably, at 0.01 bar and 298 K FJI‐H38 shows excellent trapping capability for C2H2 (1.64 mmol/g) and CO2 (2.33 mmol/g), while the uptake of C2H4 is only 0.41 mmol/g, which endows FJI‐H38 high C2H2/C2H4 selectivity and top‐level CO2/C2H4 simultaneously. Polymer‐grade C2H4 (≥99.95%) with record‐high productivity can be successfully obtained from ternary C2H2/CO2/C2H4 mixture in one step under various conditions. Even at 318 K, the separation performance has no obvious decrease. Such excellent separation performance is due to the adaptive recognition of C2H2 and CO2 by FJI‐H38 through the synergistic effect of appropriate pore size and the match of electrostatic potentials, where C2H2 and CO2 can be stabilized by the O/N and aromatic ring sites.

Foldable, Stretchable, Superelastic, and Tunable Wettability Aramid Nanofiber Aerogels for Efficient Thermal Insulation and Oil-Water Separation.

Aerogels hold great potential in thermal insulation, catalytic supports, adsorption, and separation, due to their low density, high porosity, and low thermal conductivity. However, their inherent mechanical fragility and limited control functionality pose substantial challenges that hinder their practical use. In this study, a strategy is developed for the fabrication of cross-linked aramid nanofiber aerogels (cANFAs) by combining internanofiber surface cross-linking with ice-templating techniques. This approach enables the production of cANFAs with an ultralow density of 6.3 mg/cm3 while exhibiting robust mechanical properties, including exceptional mechanical resilience, withstanding 90% compression in air and 80% compression underwater for 100 cycles, and high stretchability with a tensile strain of 34%. The cANFAs demonstrate remarkable thermal insulation properties, with low thermal conductivities of 0.03816 W/(m·K) at room temperature and 0.03518 W/(m·K) at -40 °C. Additionally, the cANFAs exhibit tunable wettability, being hydrophilic and oleophilic in air while becoming superhydrophobic underwater, which enables efficient gravity-driven oil-water separation performance. This study presents a promising route to create robust and functional aramid nanofiber aerogels for practical applications across various fields.