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Separations
Volume 12
Issue 4
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Separations, Volume 12, Issue 4 (April 2025) – 30 articles

Cover Story (view full-size image): This study addresses nitrate contamination in soil by the application of environmentally friendly adsorbents from bamboo powder and oyster shells. The porous structure of bamboo powder was chemically modified with magnesium chloride to enhance its binding to nitrate ions. Nano-sized oyster shells, composed of calcium carbonate, can also increase adsorption potential. Adsorption capacity was assessed using the isotherm models of Langmuir, Freundlich, and Dubin–Radushkevich. The estimations of the adsorption capacity of these Mg-loaded bamboo (399 mg/L) and nano-sized oyster shells (354 mg/L) demonstrate their efficiency in nitrate removal, thus promoting the recycling of waste for the protection of the environment. View this paper
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12 pages, 3159 KiB  
Article
Effects of Lubricants and the Additives on the Foaming of Desulfurization Solvent
by Jiandong Zhang, Changchun Li, Yang Yang, Xiaolong Xu and Hui Sun
Separations 2025, 12(4), 102; https://doi.org/10.3390/separations12040102 - 21 Apr 2025
Viewed by 145
Abstract
Understanding the effects of industrial lubricating oil and additives on desulfurization solution foaming is very important to both engineers and academic researchers. In this study, the influences of lubricating oil and its additive components on the foaming performance of desulfurization solution were examined, [...] Read more.
Understanding the effects of industrial lubricating oil and additives on desulfurization solution foaming is very important to both engineers and academic researchers. In this study, the influences of lubricating oil and its additive components on the foaming performance of desulfurization solution were examined, and the empirical model was established to predict the foam height of desulfurization solution containing contaminants. It is established that the additives of dodecenyl succinic acid and zinc dialkyl dithiophosphate have more significant influence on the foaming performance of desulfurization solution than the lubricant base oil. In addition, the effect can be enlarged at lower temperatures. The prediction model of the foaming performance of desulfurization solution was established, and the prediction deviation of the foam height was no more than 7%. The predicted foam height increases with increasing apparent air velocity, solution surface tension, and viscosity, and decreases with increasing solution density and average bubble radius. Additionally, the foam height and defoaming time of the contaminated industrial solution were largely reduced by employing an adsorption purification process using activated carbon as an adsorbent. The present study highlights the quantitative relationship between contaminant contents and foam height, as well as defoaming time. Full article
(This article belongs to the Section Purification Technology)
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16 pages, 4992 KiB  
Article
Degradation of Acid Orange II by FeOCl/Biochar-Catalyzed Heterogeneous Fenton Oxidation
by Jiren Yuan, Dongao Xie, Dan Li and Feigao Xu
Separations 2025, 12(4), 101; https://doi.org/10.3390/separations12040101 - 21 Apr 2025
Viewed by 160
Abstract
In recent years, the rapid development of industry has led to the discharge of large quantities of pollutants, including harmful dyes, into water sources, thereby posing potential threats to human health and the environment. FeOCl and biochar have their own shortcomings as a [...] Read more.
In recent years, the rapid development of industry has led to the discharge of large quantities of pollutants, including harmful dyes, into water sources, thereby posing potential threats to human health and the environment. FeOCl and biochar have their own shortcomings as a mediator in the heterogeneous Fenton process. To make both materials useful, FeOCl supported on bamboo biochar (FeOCl/BC) was prepared by calcination using FeCl3·6H2O and bamboo powder as raw materials, and the composite’s catalytic activities were explored with acid orange II (AO-II) as the target pollutant. The degradation efficiency of FeOCl/BC composites on AO-II was determined by testing the mass ratio of FeOCl and BC, initial pH, temperature, H2O2 concentration, catalyst addition, addition of coexisting inorganic anions, and natural organic matter. The addition of biochar to FeOCl increased the activation of H2O2 to generate •OH for the removal of AO-II and accelerated the cycle of Fe3+/Fe2+. The removal rate of AO-II by the Fe1C0.2 composite was 97.1% when the mass ratio of FeOCl and BC was 1:0.2 (Fe1C0.2), which was higher than that of the pure components (FeOCl or BC) at pH = 6.1. Moreover, after five reuses, the Fe1C0.2 composite still showed high degradation activity for AO-II, with 83.3% degradation and low activity loss. The capture experiments on the active material showed that the removal of AO-II by the Fe1C0.2 composite was mainly dominated by •OH; however, •O2− and h+ played minor roles. The synthesized Fe1C0.2 composite could be applied for organic contaminants such as AO-II with high removal efficiency. Full article
(This article belongs to the Special Issue Advances in Photocatalysis for Environmental Pollutant Removal)
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18 pages, 3306 KiB  
Article
Synthesis of Geopolymer-Based Fenton-like Catalytic Tubular Membrane for Dye Wastewater Treatment
by Pei Xiao, Qing Yang, Xingfa Deng, Kunyu Chu and Xuemin Cui
Separations 2025, 12(4), 99; https://doi.org/10.3390/separations12040099 - 17 Apr 2025
Viewed by 178
Abstract
Membrane technology is widely used in various aspects of wastewater treatment; however, single membrane technology has a series of disadvantages, such as high selectivity, poor recycling performance, and susceptibility to contamination. In this study, a treatment method combining an advanced oxidation process and [...] Read more.
Membrane technology is widely used in various aspects of wastewater treatment; however, single membrane technology has a series of disadvantages, such as high selectivity, poor recycling performance, and susceptibility to contamination. In this study, a treatment method combining an advanced oxidation process and membrane separation technology was proposed, and a geopolymer-based Fenton-like catalytic tubular membrane (GFM) was prepared by using H2O2 as a blowing agent by the direct foaming method. It was shown that the optimum conditions for the preparation of the membrane were a water glass modulus of 1.8 M, the addition of foaming agent of 1 mL, and a thickness of the membrane of 6.5 mm, with a flux of 6942 L·m−2·h−1. Due to the characteristics of the tubular membrane, the possibility of adding hydrogen peroxide directly inside the membrane allows an optimal Fenton-like removal, which is better than outside the membrane, thus reducing the consumption of hydrogen peroxide. The tubular membrane has a multi-stage porous structure, high flux, and a high specific surface area (68.74 m2/g). The GFM/H2O2 Fenton-like system formed is capable of almost completely degrading all kinds of synthetic dyes under various stringent conditions, and the XRD, FTIR, and TG analyses and cycling tests showed that the GFM has excellent stability and a significant advantage in terms of reusability. Full article
(This article belongs to the Special Issue Application of Composite Materials in Wastewater Treatment)
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28 pages, 19278 KiB  
Article
Synthesis and Application of Poly(N-isopropylacrylamide-co-methacrylic Acid) Hydrogels as Sorbent Materials for Wastewater Treatment
by Aleksandar Zdravković, Vesna Nikolić, Snežana Ilić-Stojanović, Sanja Stojanović, Ana Dinić, Maja Urošević, Ivana Gajić and Ljubiša Nikolić
Separations 2025, 12(4), 100; https://doi.org/10.3390/separations12040100 - 17 Apr 2025
Viewed by 208
Abstract
N-isopropylacrylamide and methacrylic acid were copolymerized by a free radical polymerized mechanism. The obtained hydrogel poly(N-isopropylacrylamide-co-methacrylic acid) hydrogels, poly(NIPAM-co-MAA), were utilized as sorbent material for removal Cr(VI), Mn(II), and Pb(II) ions from simulated aqueous solutions. Hydrogel [...] Read more.
N-isopropylacrylamide and methacrylic acid were copolymerized by a free radical polymerized mechanism. The obtained hydrogel poly(N-isopropylacrylamide-co-methacrylic acid) hydrogels, poly(NIPAM-co-MAA), were utilized as sorbent material for removal Cr(VI), Mn(II), and Pb(II) ions from simulated aqueous solutions. Hydrogel structures before and after heavy metal sorption are characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The swelling results indicate that poly(NIPAM-co-MAA) hydrogels are pH- and temperature-sensitive and have high swelling reversibility through three swelling/contraction cycles. The studied parameters of heavy metal sorption include the effect of pH, the initial concentration of heavy metal, the effect of temperature, and the desorption of metal ions. The maximum sorption capacities of poly(NIPAM-co-MAA) hydrogels were determined at pH 4.5 and 25 °C, and they are, for Cr(VI), Mn(II), and Pb(II) ions, 289.35 mg/g, 190.59 mg/g, and 349.71 mg/g, respectively. The pseudo-second-order model and the Langmuir adsorption isotherm best describe the sorption of heavy metal ions onto hydrogels. The removal of heavy metals is an exothermic reaction, and the interaction mechanism between the metal and the hydrogel is primarily physical in nature. Results of three sorption/desorption cycles show a good desorption ratio and sorption capacity of poly(NIPAM-co-MAA) hydrogels. Full article
(This article belongs to the Special Issue New and Modified Polymers for Detection and Removal of Pollutants from Water and Air)
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13 pages, 4706 KiB  
Article
Preparation of Lithium Carbonate from Manganese-Containing Desorption Solution from Salt Lakes via an Organophosphoric Acid Extraction System
by Shaolei Xie, Yuze Zhang, Xiaowu Peng, Yong Niu, Hailong Lu, Fugen Song, Dong Shi and Lijuan Li
Separations 2025, 12(4), 98; https://doi.org/10.3390/separations12040098 - 15 Apr 2025
Viewed by 161
Abstract
Adsorption is a popular method for the recovery of low-grade lithium. It is a low-cost and highly efficient way to treat solutions with low lithium concentrations. The impurity content determines the industrial application. This study investigated a novel strategy to remove divalent cations [...] Read more.
Adsorption is a popular method for the recovery of low-grade lithium. It is a low-cost and highly efficient way to treat solutions with low lithium concentrations. The impurity content determines the industrial application. This study investigated a novel strategy to remove divalent cations from a desorption solution containing Mg2+, Ca2+, and Mn2+, generated by a manganese absorbent using an organophosphoric acid, followed by precipitation of lithium carbonate from the concentrated raffinate by evaporation. Di(2-ethylhexyl)phosphoric acid (P204) was selected as the preferred extractant. The saponification method and degree of saponification were determined, and the extraction parameters (pH, extractant concentration, and phase ratio) were investigated. A three-stage countercurrent extraction process was tested. Removal efficiencies of Mg2+, Ca2+, and Mn2+ from the manganese-containing desorption solution exceeded 99%, leaving <1.0 mg/L divalent cations in the raffinate. The raffinate was evaporated and concentrated to >23 g/L lithium. The total concentration of divalent cations in the lithium-rich solution was approximately 10.0 mg/L. Further conversion with sodium carbonate was carried out to prepare a battery-grade lithium carbonate product with a purity of 99.83%. The present work may provide a novel means of lithium recovery from a manganese-containing desorption solution. Full article
(This article belongs to the Special Issue Green and Efficient Separation and Extraction of Salt Lake Resources)
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26 pages, 12159 KiB  
Review
Research Progress on the Development and Application of Cyclodextrin-Based Chromatographic Stationary Phases
by Wenlanqi Du, Jia Jia, Yinghong Zhao, Ailing Ning and Rongfu Huang
Separations 2025, 12(4), 97; https://doi.org/10.3390/separations12040097 - 14 Apr 2025
Viewed by 210
Abstract
This review systematically summarizes the novel preparation methods of cyclodextrin-based chromatographic stationary phases and their applications for chiral recognition in separation techniques such as capillary gas chromatography and high-performance liquid chromatography. Aiming at the current situation that enantiomers of chiral compounds present significant [...] Read more.
This review systematically summarizes the novel preparation methods of cyclodextrin-based chromatographic stationary phases and their applications for chiral recognition in separation techniques such as capillary gas chromatography and high-performance liquid chromatography. Aiming at the current situation that enantiomers of chiral compounds present significant differences at the pharmacological, pharmacodynamic, and toxicological levels, the core value of chromatographic chiral separation technology in the field of drug discovery and development is emphasized. By analyzing the unique cavity structure and excellent stereoselective properties of cyclodextrins, the mechanism of their action as a chromatographic stationary phase was elaborated. Combined with the typical applications of different derivatized cyclodextrin stationary phases in drug analysis, environmental testing, and biological samples, the value and potential of cyclodextrin stationary phases in stereoisomer separation are systematically demonstrated. Full article
(This article belongs to the Topic Advances in Chromatographic Separation)
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12 pages, 3852 KiB  
Article
Screening and Isolating Acetylcholinesterase Inhibitors from Olea europaea L. Fruit Using Ultrafiltration–Liquid Chromatography Coupled with High-Speed Counter-Current Chromatography
by Xingcui Wang, Yingshan Zhang, Jules Muhire, Duolong Di, Xinyi Huang and Dong Pei
Separations 2025, 12(4), 96; https://doi.org/10.3390/separations12040096 - 12 Apr 2025
Viewed by 171
Abstract
Alzheimer’s disease (AD) is a progressive neurodegenerative condition and one of the most prevalent types of dementia in older adults. Currently, the primary drugs used to treat AD are acetylcholinesterase (AChE) inhibitors. The development of natural substances has become a research hotspot due [...] Read more.
Alzheimer’s disease (AD) is a progressive neurodegenerative condition and one of the most prevalent types of dementia in older adults. Currently, the primary drugs used to treat AD are acetylcholinesterase (AChE) inhibitors. The development of natural substances has become a research hotspot due to the high number of adverse effects of synthetic drugs. In this study, a new assay based on ultrafiltration–liquid chromatography–high-speed counter-current chromatography (UF-HPLC-HSCCC) was developed for the rapid screening and identification of AChE inhibitors from Olea europaea L. fruit. In this research, we screened and isolated two AChE inhibitors from O. europaea fruit extracts, identified by EI-MS and NMR as secologanoside and oleuroside-11-methyl ester. These compounds were identified for the first time from O. europaea and found to possess AChE inhibitory activity using an in vitro AChE inhibition assay and molecular docking. The IC50 values of the two compounds were 0.76 ± 0.04 mM and 1.08 ± 0.05 mM. The results demonstrated that secologanoside showed better AChE inhibition activity than oleuroside-11-methyl ester, suggesting that this compound is a promising AChE inhibitor. At the same time, the results showed that the combination of UF-HPLC- HSCCC provides a powerful tool for screening and isolating AChE inhibitors in complex samples. Full article
(This article belongs to the Topic Counter-Current Chromatography in Natural Products Isolation)
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23 pages, 527 KiB  
Review
New Trends in the Methodologies of Determination of Benzodiazepine Residues in Biological Samples
by Israel S. Ibarra, Isaí Vázquez-Garrido, Gabriela Islas and Juan F. Flores-Aguilar
Separations 2025, 12(4), 95; https://doi.org/10.3390/separations12040095 - 11 Apr 2025
Viewed by 259
Abstract
The benzodiazepines are essential drugs used in medicine for anxiolytic, sedative, and hypnotic effects. According to the World Health Organization, the benzodiazepines are the most prescribed hypnotic drugs in the last decade (2010 at time), and their inappropriate use can damage the environment [...] Read more.
The benzodiazepines are essential drugs used in medicine for anxiolytic, sedative, and hypnotic effects. According to the World Health Organization, the benzodiazepines are the most prescribed hypnotic drugs in the last decade (2010 at time), and their inappropriate use can damage the environment and human health. The availability of efficient analytical methods is crucial for the determination of these drugs in a complex matrix such as biological samples in clinical settings. In the last decade, several methods have been developed and have been applied to the detection and determination of benzodiazepines or their derivates. The present manuscript reviews selective and sensitive methodologies based on chromatographic, electrophoretic, and electrochemical systems for the determination of benzodiazepines in biological samples, covering the time of the last years and providing detailed information on sample pretreatment and instrumental conditions. Full article
(This article belongs to the Section Bioanalysis/Clinical Analysis)
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11 pages, 4115 KiB  
Article
Porous Composite Polymers Composed of Polyethyleneimine and Cyclodextrins: Synthesis and Application as Adsorbents for an Organic Compound
by Naofumi Naga, Yuma Miyazaki and Tamaki Nakano
Separations 2025, 12(4), 94; https://doi.org/10.3390/separations12040094 - 10 Apr 2025
Viewed by 209
Abstract
Polyethyleneimine-based porous composites have been prepared by ring-opening polymerization of 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] (3AZ), a tri-aziridine compound, in water, in the presence of cyclodextrins (CDs), i.e., α-CD, γ-CD, methyl-β-cyclodextrin (Me-β-CD), monoacetyl-β-cyclodextrin (Ac-β-CD), and hydroxypropyl-β-cyclodextrin (HP-β-CD). The corresponding 3AZ-CD porous polymer composites were successfully obtained in [...] Read more.
Polyethyleneimine-based porous composites have been prepared by ring-opening polymerization of 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] (3AZ), a tri-aziridine compound, in water, in the presence of cyclodextrins (CDs), i.e., α-CD, γ-CD, methyl-β-cyclodextrin (Me-β-CD), monoacetyl-β-cyclodextrin (Ac-β-CD), and hydroxypropyl-β-cyclodextrin (HP-β-CD). The corresponding 3AZ-CD porous polymer composites were successfully obtained in most cases under a wide range of CD concentrations, 5–20 wt%, and reaction temperatures, 20–60 °C. The reaction system in the presence of Ac-β-CD preferentially yielded gels. The polymer composites were composed of connected particles with sizes of the order of 10−9 m. The particle sizes decreased with an increase in the CD concentration. Young’s moduli of the 3AZ-CD porous polymer composites tended to increase with an increase in bulk density. The 3AZ-CD porous polymer composites with Me-β-CD and HP-β-CD effectively adsorbed phenolphthalein in the solution. The adsorption value increased with increasing the CD content and rose to more than 600 mg/g of porous polymer composite. Full article
(This article belongs to the Special Issue Application of Advanced Materials and Technologies in the Separation and Adsorption)
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14 pages, 3324 KiB  
Article
Comparison of CuCl/NaY and CuCl/AC Process Performance Using a Vacuum Pressure Swing Adsorption Simulation
by Congli Li, Xuling Guo, Lei Tang, Jiahui Yang and Qi Shi
Separations 2025, 12(4), 93; https://doi.org/10.3390/separations12040093 - 10 Apr 2025
Viewed by 237
Abstract
A five-bed, seven-step vacuum pressure swing adsorption (VPSA) system was computationally modeled to assess carbon monoxide (CO) separation from CO/N2 mixed gas (30/70, v/v). Two adsorbents with distinct isotherm characteristics (steep-slope CuCl/NaY and flat-slope CuCl/AC) were comparatively evaluated for [...] Read more.
A five-bed, seven-step vacuum pressure swing adsorption (VPSA) system was computationally modeled to assess carbon monoxide (CO) separation from CO/N2 mixed gas (30/70, v/v). Two adsorbents with distinct isotherm characteristics (steep-slope CuCl/NaY and flat-slope CuCl/AC) were comparatively evaluated for their process performance, focusing on CO purity, recovery, productivity, and energy consumption. The simulation results demonstrate that under industrial-grade specifications requiring both adsorbents to achieve CO purity > 97% and recovery > 83%, CuCl/AC achieves a 3.9-fold higher productivity (27.238 vs. 7.016 mol kg−1 h−1) than CuCl/NaY while maintaining a comparable energy consumption. This performance disparity stems from CuCl/AC’s enhanced bed layer CO desorption amount during a cyclic VPSA operation, which enhances feed gas throughput per unit adsorbent mass. This study demonstrates that CuCl/AC, with its flat-slope adsorption isotherm and high desorption amount, can serve as a promising adsorbent for achieving high-purity CO with a significantly enhanced productivity via the VPSA process. Full article
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17 pages, 2349 KiB  
Article
Sustainable Soil Volatilome: Discrimination of Land Uses Through GC-MS-Identified Volatile Organic Compounds
by Emoke Dalma Kovacs, Teodor Rusu and Melinda Haydee Kovacs
Separations 2025, 12(4), 92; https://doi.org/10.3390/separations12040092 - 8 Apr 2025
Viewed by 258
Abstract
This study investigates soil volatilomics as an innovative approach to assessing the impact of land use on soil quality. This research addresses the critical need for sensitive diagnostic tools to distinguish subtle biochemical variations in soils influenced by different land use management practices. [...] Read more.
This study investigates soil volatilomics as an innovative approach to assessing the impact of land use on soil quality. This research addresses the critical need for sensitive diagnostic tools to distinguish subtle biochemical variations in soils influenced by different land use management practices. Soil samples were collected along a land use transect in Cluj County. Their volatile organic compounds were extracted by headspace solid-phase microextraction (HS–SPME) followed by a gas chromatography–mass spectrometry (GC–MS) analysis. A multivariate statistical method was used to differentiate the volatilome profile. Among the 106 detected compounds, oxygenated species dominated across all land uses, with the highest concentrations in forest soils (77%), followed by grasslands (71%) and agricultural soils (65%). Principal component analysis revealed distinct clustering patterns, with the first two components explaining 72.8% of the total variance (PC1: 41.7%, PC2: 31.1%). Supervised PLS-DA modeling demonstrated robust land use discrimination, achieving AUC values of 0.868 for agricultural versus forest comparisons and 0.810 for both forest versus grassland and grassland versus agricultural comparisons. The volatilome diversity analysis indicated that grasslands contained the highest number of distinct compounds (64), closely followed by forest soils (63), while agricultural soils showed reduced diversity (51). These key findings revealed distinct volatile signatures, with forest soils exhibiting the highest complexity and agricultural soils demonstrating a more homogeneous profile, whereas grassland soils presented high internal variability. These results underscore the potential of soil volatilome profiling as a sensitive indicator of the effects of land use on soil biochemical processes and support the utility of soil volatilomics in sustainable land management and ecosystem monitoring. Full article
(This article belongs to the Special Issue Chromatographic Methods for Environment, Biota and Food Contaminants Analysis)
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16 pages, 2875 KiB  
Article
Extraction and Characterization of TiO2 Pigments from Commercial Paints for Environmental Studies
by Allan Philippe, Sylvester Ndoli-Kessie, Christian Fricke, Jean-Michel Guigner, Benjamin Heider and Eliana Di Lodovico
Separations 2025, 12(4), 91; https://doi.org/10.3390/separations12040091 - 8 Apr 2025
Viewed by 243
Abstract
TiO2 nanoparticles are found as pigments in coatings and paints and are, therefore, released into the environment through runoff. To assess their environmental impact, comprehensive fate and ecotoxicity studies necessitate particles closely resembling those released into the environment. In response, we developed [...] Read more.
TiO2 nanoparticles are found as pigments in coatings and paints and are, therefore, released into the environment through runoff. To assess their environmental impact, comprehensive fate and ecotoxicity studies necessitate particles closely resembling those released into the environment. In response, we developed a method designed to isolate TiO2 particles from commercial paints. Using six contrasting paints alongside a pure TiO2 pigment, we evaluated two extraction methods in terms of recovery, purification rate, and preservation of both inorganic and organic particle coatings. The paints and extracts were characterized using cryogenic-TEM, ICP-OES, thermogravimetry, and infrared spectroscopy. In contrast to the alkaline-based extraction method, the extraction with acetic acid facilitated the retention of both inorganic and organic coatings and ensured good removal of organic polymers. Recovery rates exceeded 70% for all paints and extraction methods, yet the complete removal of SiO2, when present, was not achieved. CaCO3 removal was effective with both extraction methods. Our developed extraction method enables the isolation of TiO2-particles similar to those aged within paints. However, we recommend using silicate-free paints when SiO2 interference is of concern for the study design. Furthermore, this method could be interesting for pigment recycling, offering a gentler alternative to existing techniques which compromise particle coatings. Full article
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18 pages, 15324 KiB  
Article
Migration and Enrichment of Rare Earth Elements in the Flotation Process of Rare Earth-Bearing Collophanite
by Jiawei Lin, Jue Kou, Xiaojin Wen and Hongda Xu
Separations 2025, 12(4), 90; https://doi.org/10.3390/separations12040090 - 7 Apr 2025
Viewed by 208
Abstract
Rare earth elements (REEs) are important strategic resources, widely used in various technological fields, especially heavy rare earth elements (HREEs). China has extensive rare earth deposits, with diverse mineral types and a complete range of rare earth elements, characterized by a “heavy south, [...] Read more.
Rare earth elements (REEs) are important strategic resources, widely used in various technological fields, especially heavy rare earth elements (HREEs). China has extensive rare earth deposits, with diverse mineral types and a complete range of rare earth elements, characterized by a “heavy south, light north” resource distribution pattern. The rare earth-bearing collophane in the Zhijin area of Guizhou is a typical marine sedimentary phosphorite deposit with large reserves and a high heavy rare earth content. This study investigates the rare earth-bearing collophane in the Zhijin area using X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) to analyze its mineral composition and occurrence characteristics. In terms of flotation, a reverse flotation process for magnesium removal was adopted. By optimizing the flotation parameters, including grinding fineness, collector dosage, pH regulator dosage, and depressant dosage, the optimal flotation conditions were determined. A further mineralogical analysis was conducted on both the flotation concentrate and tailings. The results show that the main minerals in the rare earth-bearing collophane of Zhijin are fluorapatite and dolomite, with dolomite as the primary gangue mineral, and rare earth elements are mainly hosted in fluorapatite. The optimal flotation conditions were achieved when the grinding fineness was −74 μm with an 83% passing rate, XF-1 was used as the collector at a dosage of 300 g/t, sulfuric acid (H2SO4) as the pH regulator at 6 kg/t, and phosphoric acid (H3PO4) as the depressant at 3 kg/t. By employing an optimal reagent regime and implementing a reverse flotation process consisting of one roughing and one scavenging stage, a phosphate concentrate was obtained with a P2O5 grade of 31.61% and an REO content of 0.161%. The P2O5 recovery reached 84.22%, while the REO recovery was 78.65%. Compared to the raw ore, the P2O5 grade increased by 11.52 percentage points, and the REO content improved by 0.051 percentage points. Mineralogical analysis of the flotation concentrate and tailings revealed that dolomite was effectively removed by reverse flotation, while rare earth elements were successfully enriched in the phosphate concentrate. In conclusion, this study provides an efficient flotation separation process for rare earth-bearing collophane and dolomite, while also offering technical support for the efficient recovery of rare earth resources. This research has significant theoretical and practical implications. Full article
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27 pages, 5960 KiB  
Review
Advances in Enrichment and Purification Technology of Ammonium Perrhenate
by Hailong Jing, Qidong Zhang, Zhifang Hu, Hongling Jiang, Bowen Gao, Tingan Zhang and Yanxi Yin
Separations 2025, 12(4), 89; https://doi.org/10.3390/separations12040089 - 6 Apr 2025
Viewed by 322
Abstract
Rhenium metal is extensively utilized in the aerospace industry for the manufacturing of various superalloys due to its unique properties, and plays an indispensable role in the field of high technology. Rhenium resources are primarily associated with copper, molybdenum, and other metal ores. [...] Read more.
Rhenium metal is extensively utilized in the aerospace industry for the manufacturing of various superalloys due to its unique properties, and plays an indispensable role in the field of high technology. Rhenium resources are primarily associated with copper, molybdenum, and other metal ores. Ammonium perrhenate is predominantly derived from copper and molybdenum ore roasting flue gas scrubbers containing various impurities in the rhenium-containing contaminated acid. The complex composition of the contaminated acid renders the enrichment and purification of ammonium perrhenate more challenging, necessitating further research and development of the technology. This paper reviews the research progress in ammonium perrhenate enrichment and purification technology, encompassing chemical precipitation, adsorption, extraction, ion exchange, extraction chromatography, and recrystallization. It analyses the advantages and limitations of various methods, with the aim of providing a reference for future developments in ammonium perrhenate enrichment and purification technology. Furthermore, the paper presents a prospective view on the development of ammonium perrhenate enrichment and purification technology, focusing on the objective of obtaining more selective purification materials and more efficient purification techniques for ammonium perrhenate. Full article
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26 pages, 4510 KiB  
Review
Application of Lignin-Derived Carbon Materials in Adsorption and Separation
by Xiaorui Dong, Yunlei Zhang, Shouyan Shao, Hao Li and Xingchen Yan
Separations 2025, 12(4), 88; https://doi.org/10.3390/separations12040088 - 4 Apr 2025
Viewed by 412
Abstract
In the context of sustainable human development and the depletion of petroleum resources, lignin has received widespread attention as a carbon-rich, low-cost, and renewable resource. Owing to their distinctive physical and chemical properties, carbon materials are extensively applied in the fields of adsorption [...] Read more.
In the context of sustainable human development and the depletion of petroleum resources, lignin has received widespread attention as a carbon-rich, low-cost, and renewable resource. Owing to their distinctive physical and chemical properties, carbon materials are extensively applied in the fields of adsorption and separation. The conversion of lignin into diverse multifunctional carbon materials, such as porous carbon, activated carbon, carbon fibers, carbon foams, and carbon aerogels, has emerged as a pivotal strategy for the high-value utilization of lignin. In this paper, representative examples of various lignin-based carbon materials utilized in the field of adsorption and separation over the past decade are reviewed and categorized according to the type of carbon materials, and their preparation methods and adsorption effects are described. Full article
(This article belongs to the Special Issue Separation Technology for Resource Utilization and Recovery)
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14 pages, 3193 KiB  
Article
Enhancing SO3 and Fine Particle Co-Removal in Low-Low Temperature Electrostatic Precipitation via Turbulent Agglomeration
by Zongkang Sun, Danping Pan, Lingxiao Zhan and Linjun Yang
Separations 2025, 12(4), 87; https://doi.org/10.3390/separations12040087 - 3 Apr 2025
Viewed by 180
Abstract
Fine particulate matter (PM) and sulfur trioxide (SO3) from coal-fired flue gas pose significant environmental and health risks. While low-low temperature electrostatic precipitators (LLT-ESPs) enhance PM and SO3 removal by cooling flue gas below the acid dew point, their efficiency [...] Read more.
Fine particulate matter (PM) and sulfur trioxide (SO3) from coal-fired flue gas pose significant environmental and health risks. While low-low temperature electrostatic precipitators (LLT-ESPs) enhance PM and SO3 removal by cooling flue gas below the acid dew point, their efficiency is limited by incomplete agglomeration. This study proposes integrating turbulent agglomeration technology into LLT-ESP systems to improve collision and adhesion between droplets and particles. Experiments were conducted under three conditions: flue gas containing SO3 alone, fly ash alone, and their mixture. Particle size distributions, mass concentrations, and removal efficiencies were analyzed using ELPI+ and PM samplers. Results showed that turbulent agglomeration reduced the number concentration of sulfuric acid droplets by 21.4% from 1.59 × 107 cm−3 to 1.25 × 107 cm−3 (SO3-only case) and fine fly ash particles by 19.5% from 5.79 × 106 cm−3 to 4.66 × 106 cm−3 (fly-ash-only case). Although LLT-ESP combined with turbulent agglomeration has a certain removal effect in the case of individual pollutants, the overall effect is not unsatisfactory, especially for SO3, whose mass-based removal efficiency was merely 16.2%. The value of the fly-ash-only case was 92.1%. Synergistic effects in the coexistence scenario (fly ash and SO3) significantly enhanced agglomeration, increasing SO3 and PM removal efficiencies to 82.9% and 97.6%, respectively, compared to 69.7% and 90.1% without turbulent agglomeration. The mechanism behind the efficiency improvement involved droplet–particle collisions, sulfate deposition, and improved particle charging. This work demonstrates that turbulent agglomeration optimizes multi-pollutant control in LLT-ESP systems, offering a feasible strategy for achieving ultra-low emissions in coal-fired power plants. Full article
(This article belongs to the Special Issue Application of Advanced Materials and Technologies in the Separation and Adsorption)
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14 pages, 2508 KiB  
Article
Selective Adsorption of VOCs/Water Vapor on Activated Carbon: The Role of Adsorbent and VOC Molecular Polarity
by Wenlin Hang, Jiaxing Sun, Ronghang Zhao, Heng Chen and Jinjin Li
Separations 2025, 12(4), 86; https://doi.org/10.3390/separations12040086 - 2 Apr 2025
Viewed by 262
Abstract
The presence of abundant water vapor in industrial organic waste gases greatly reduces the selective adsorption of volatile organic pollutants (VOCs). The polarity of the adsorbent and VOC molecules plays an important role in the adsorption process, especially in the presence of water [...] Read more.
The presence of abundant water vapor in industrial organic waste gases greatly reduces the selective adsorption of volatile organic pollutants (VOCs). The polarity of the adsorbent and VOC molecules plays an important role in the adsorption process, especially in the presence of water vapor. In this paper, commercial coconut shell activated carbon (CSC) was modified by a thermal reduction treatment to obtain heat-treated coconut shell activated carbon (HCSC). CSC and HCSC exhibited similar pore structure characteristics but differed significantly in surface oxygen content (10.97% and 7.55%, respectively). Dynamic adsorption breakthrough experiments were conducted to determine the dynamic adsorption capacities of toluene on both adsorbents under varying relative humidity levels. HCSC demonstrated superior toluene/water vapor adsorption selectivity. Further analyses of toluene adsorption kinetics, activation energy, and water vapor adsorption isotherms revealed that the lower surface oxygen functional group content of HCSC resulted in a weaker surface polarity, facilitating the adsorption of weakly polar toluene. This was attributed to stronger toluene–HCSC interactions and weaker water–HCSC interactions. The dynamic adsorption capacities of three VOCs with varying polarities were also tested on HCSC. The observed VOC/water vapor adsorption selectivity had the following order: toluene > n-heptane > 1,2-dichloroethane. Grand Canonical Monte Carlo (GCMC) simulations were employed to quantify the relationship between the adsorption selectivity of eight VOCs with varying polarities and their molecular polarity. The results indicated a decrease in adsorption selectivity with increasing VOC polarity. A mechanistic analysis suggests that more polar VOCs prefer to adsorb polar oxygen-containing functional groups, competing with water molecules for adsorption sites. Under high humidity, hydrogen bonding leads to the formation of water clusters, exacerbating this competition. This research holds significant implications for the efficient selective adsorption of VOCs with varying polarities in humid industrial conditions. Full article
(This article belongs to the Special Issue Application of Advanced Materials and Technologies in the Separation and Adsorption)
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15 pages, 2464 KiB  
Article
Determination, Mobility and Risk Assessment of Pesticides in Ginseng Wine Using Dispersive Liquid–Liquid Micro Extraction Combined with GC-MS/MS and LC-MS/MS
by Xuanwei Xu, Dan Zhao, Min Zhang, Xinxin Meng, Ying Chen, Xu Leng, Shuang Liang and Yueru Li
Separations 2025, 12(4), 85; https://doi.org/10.3390/separations12040085 - 2 Apr 2025
Viewed by 240
Abstract
The simultaneous determination of 166 pesticides using dispersive liquid–liquid micro extraction combined with gas chromatography–tandem mass spectrometry and ultra-high performance liquid chromatography–tandem mass spectrometry (DLLME–GC-MS/MS+LC-MS/MS) is presented here. In this work, DLLME was extended to complex residues in the ginseng wine matrix. This [...] Read more.
The simultaneous determination of 166 pesticides using dispersive liquid–liquid micro extraction combined with gas chromatography–tandem mass spectrometry and ultra-high performance liquid chromatography–tandem mass spectrometry (DLLME–GC-MS/MS+LC-MS/MS) is presented here. In this work, DLLME was extended to complex residues in the ginseng wine matrix. This study first focused on the selection of an appropriate solvent that enabled the dissolution of analytes from ginseng wine. The matrix-matched calibration curves showed good linearity in the range of 2–100 µg L−1 for all pesticides, with coefficients of determination of 0.977–1. The mean recoveries were in the range of 3–124%, with 133 pesticides in the range of 60–130%, and the relative standard deviations (RSDs) were between 0.4% and 31.4%. The limits of detection (LOD) and limits of quantitation (LOQ) were within the ranges of 0.14–140 and 0.5–470 ng L−1, respectively. Therefore, this analytical method contributes to residue analyses of 133 pesticides for the routine laboratory testing of ginseng wine. Research was also carried out by soaking the pesticide-positive samples in ginseng wine to monitor the migration and degradation of pesticides. The results showed that, the migration rates of thifluzamidewaslower than 60%, cyprodinil was 73.7, while azoxystrobin, pyrimethanil, carbendazim, dimethomorph, difenoconazole, pyraclostrobin, propiconazole, quintozene, pentachloroaniline, tebuconazole and phoximwere between 75% and 95%. Quintozene was more easily degraded into pentachloroaniline in the wine. Full article
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15 pages, 2500 KiB  
Article
Adsorption and Desorption Characteristics of Simiao Yong’an Decoction on Macroporous Adsorption Resins
by Wei Jiao, Erhu Liu, Yao Luo, Yanxin Niu and Yongxue Guo
Separations 2025, 12(4), 84; https://doi.org/10.3390/separations12040084 - 31 Mar 2025
Viewed by 157
Abstract
In this study, to identify an appropriate macroporous resin for the purification of the crude extract derived from Simiao Yong’an Decoction (SMYAD), five distinct resins were evaluated based on their adsorption and desorption performance. Through this comparative analysis, D101 macroporous adsorption resin was [...] Read more.
In this study, to identify an appropriate macroporous resin for the purification of the crude extract derived from Simiao Yong’an Decoction (SMYAD), five distinct resins were evaluated based on their adsorption and desorption performance. Through this comparative analysis, D101 macroporous adsorption resin was determined to be the most suitable candidate. Investigations into the adsorption mechanism revealed that the process followed pseudo-second-order kinetics and was well described by the Langmuir isotherm model. Thermodynamic analysis further indicated the spontaneous and exothermic nature of the adsorption process. Through systematic optimization, the ideal purification parameters for SMYAD were established as follows: sample loading volume—6 bed volumes (BV), eluent concentration—90% ethanol (v/v), and eluent volume—3 BV, with both adsorption and desorption flow rates maintained at 3 BV/h. Finally, the purification effect was evaluated by fingerprint and similarity analysis. Under the optimal purification process, the content of the five index components was as follows: harpagide (4.26 mg/g), chlorogenic acid (38.37 mg/g), ferulic acid (4.78 mg/g), liquiritin (7.42 mg/g), and harpagoside (10.25 mg/g). The yield of the five components ranged from 70.74% to 86.26%. In conclusion, this approach demonstrates rapid processing capabilities and high efficiency, offering valuable methodological insights for the isolation and purification of complex traditional Chinese medicine formulations using macroporous adsorption resins. Full article
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16 pages, 5058 KiB  
Article
Titanium Meets Carbon: Enhanced Reusable Filters for Oil–Water Separation and Environmental Remediation
by Amir-Hadi Boroumand, Kayla Laguana, Eric Dudley, Pilar Cuadros-Arias, Adrian Rubio, Zachary Shin, Jack Webster and Mingheng Li
Separations 2025, 12(4), 83; https://doi.org/10.3390/separations12040083 - 30 Mar 2025
Viewed by 726
Abstract
To mitigate the environmental effects of oil spills, a novel hydrophilic–oleophobic mixed-coated filter was developed for efficient oil–water separation and surface oil recovery. The coating consisted of titanium dioxide nanoparticles (TiO2) and ultra-fine carbon black powder, deposited onto a 304 stainless-steel [...] Read more.
To mitigate the environmental effects of oil spills, a novel hydrophilic–oleophobic mixed-coated filter was developed for efficient oil–water separation and surface oil recovery. The coating consisted of titanium dioxide nanoparticles (TiO2) and ultra-fine carbon black powder, deposited onto a 304 stainless-steel mesh substrate via spray deposition, followed by high-temperature sintering. This process induced a phase transition in TiO2 from anatase to rutile, and formed a TiC khamrabaevite. The filter’s performance was evaluated using contact angle measurements and filtration tests with a motor oil–water mixture, while SEM, EDS, and XRD analyses characterized its morphology and coating structure. Contact angle testing confirmed that carbon modification significantly enhanced the oleophobicity of the TiO2 filter, and SEM imaging demonstrated higher substrate coating adhesion, enabling multiple reuse cycles. These findings highlight the potential of TiO2 carbon composite coatings in improving oil spill remediation technologies by offering a reusable and efficient filtration system. Full article
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23 pages, 11856 KiB  
Review
Microplastics in the Environment: A Review Linking Pathways to Sustainable Separation Techniques
by Lin Zeng, Long Li, Jueyan Xiao, Penghui Zhou, Xiaoxiang Han, Bohao Shen and Li Dai
Separations 2025, 12(4), 82; https://doi.org/10.3390/separations12040082 - 30 Mar 2025
Viewed by 517
Abstract
Since the mid-20th century, the quantity of microplastics (MPs) has increased significantly, becoming a persistent environmental pollutant widely distributed in global water bodies, soils, and the atmosphere. While plastic materials have brought significant convenience to daily life, the MPs resulting from their degradation [...] Read more.
Since the mid-20th century, the quantity of microplastics (MPs) has increased significantly, becoming a persistent environmental pollutant widely distributed in global water bodies, soils, and the atmosphere. While plastic materials have brought significant convenience to daily life, the MPs resulting from their degradation pose increasing threats to ecosystems and human health. This comprehensive review examines the sources, migration pathways, and ecological impacts of MPs, and critically evaluates the current separation techniques from physical, chemical, and biological perspectives. In particular, numerical simulations of the hydrocyclone separation technique reveal its unique flow characteristics, including turbulent velocity gradients and axial pressure differences, with a separation efficiency of up to 93%. This technique offers advantages such as high efficiency, low energy consumption, and environmental friendliness. In response to the growing microplastic pollution issue, this review emphasizes that the development of future microplastic separation techniques should prioritize separation efficiency, sustainability, and environmental compatibility. Continued research in this field will provide theoretical support for optimizing microplastic pollution control technologies and contribute to achieving environmental protection and sustainable development goals. Full article
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20 pages, 7637 KiB  
Article
HPLC Fingerprint Analysis with the Antioxidant Potential of Polygonatum sibiricum Combined with the Chemometric Calculations
by Li-Wen Zhang, Jin Wang, Ye Ge, Zhe-Lin Kuang and Ying-Qing Zhang
Separations 2025, 12(4), 81; https://doi.org/10.3390/separations12040081 - 29 Mar 2025
Viewed by 230
Abstract
Polygonatum sibiricum (P. sibiricum) is a significantly health-promoting plant unique in medicine and food. Currently, research on the bioactive components of P. sibiricum primarily focuses on polysaccharides. According to the Chinese Pharmacopoeia, the polysaccharide content in P. sibiricum must be [...] Read more.
Polygonatum sibiricum (P. sibiricum) is a significantly health-promoting plant unique in medicine and food. Currently, research on the bioactive components of P. sibiricum primarily focuses on polysaccharides. According to the Chinese Pharmacopoeia, the polysaccharide content in P. sibiricum must be at least 7.0%, which is the only criterion used for determining its content. In contrast, this study aims to thoroughly investigate and clarify the various components that contribute to the therapeutic and functional properties of P. sibiricum. We seek to broaden the focus beyond polysaccharides to identify other potentially significant bioactive substances. We established High-Performance Liquid Chromatograph (HPLC) fingerprints for wine-processed P. sibiricum from various regions and identified 17 common peaks. The antioxidant activities of these components were assessed using ABTS and DPPH methods. The spectrum–effect relationship was elucidated through partial least squares regression and grey relational analysis. The results revealed that the antioxidant active components in wine-processed P. sibiricum include 5-hydroxymethylfurfural, p-hydroxycinnamic acid, myricetin, caffeic acid, vanillic acid, and adenosine. This research not only clarifies the antioxidant material basis of wine-processed P. sibiricum but also establishes a scientific foundation for enhanced quality control in future applications. Full article
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17 pages, 3160 KiB  
Article
Prediction and Interpretative Analysis of Bed Expansion Ratio in Pulsed Fluidized Beds
by Yanjiao Li, Heng Jiang, Kun Hong and Liang Dong
Separations 2025, 12(4), 80; https://doi.org/10.3390/separations12040080 - 28 Mar 2025
Viewed by 170
Abstract
The bed expansion height serves as a macroscopic representation of the efficiency with which vibrational energy is transmitted within pulsed fluidized beds. Due to its complex nonlinear characteristics, further research is needed to explore the fluidization mechanisms in pulsed fluidized beds and identify [...] Read more.
The bed expansion height serves as a macroscopic representation of the efficiency with which vibrational energy is transmitted within pulsed fluidized beds. Due to its complex nonlinear characteristics, further research is needed to explore the fluidization mechanisms in pulsed fluidized beds and identify effective predictive models for expansion ratios. This work evaluates and analyzes the predictive capabilities of models established based on theoretical learning, as well as three machine learning methods. Additionally, dimensionless numbers are introduced to facilitate dimensionality reduction. Among these methods, the extreme gradient boosting model demonstrated exceptional performance, achieving an R2 value of 0.9907 on the training set and reaching 0.9300 on the testing set. Furthermore, an interpretability analysis of the extreme gradient boosting model was conducted using Shapley additive explanations, revealing that f/fn is the most significant factor influencing the bed expansion ratio, while H0/D has a relatively minor effect. These findings provide a basis for effectively predicting bed expansion ratios and facilitate further scale-up studies in pulsed fluidized beds. Full article
(This article belongs to the Special Issue Research Progress of Gas–Solid Fluidized Dry Separation)
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27 pages, 7256 KiB  
Article
Determination of the Phytochemical Profile and Antioxidant Activity of Some Alcoholic Extracts of Levisticum officinale with Pharmaceutical and Cosmetic Applications
by Alaa Sahlabgi, Dumitru Lupuliasa, Iuliana Stoicescu, Lavinia Lia Vlaia, Monica Licu, Antoanela Popescu, Alexandru Scafa-Udriște, Răzvan Ene, Lucian Hîncu, Carmen Elena Lupu and Magdalena Mititelu
Separations 2025, 12(4), 79; https://doi.org/10.3390/separations12040079 - 28 Mar 2025
Viewed by 570
Abstract
Levisticum officinale (lovage) is an aromatic and medicinal plant traditionally used for its antioxidant, anti-inflammatory and antimicrobial properties. The aim of this study was to evaluate the phytochemical composition and antioxidant activity of hydroalcoholic extracts obtained from leaves, roots and the whole plant, [...] Read more.
Levisticum officinale (lovage) is an aromatic and medicinal plant traditionally used for its antioxidant, anti-inflammatory and antimicrobial properties. The aim of this study was to evaluate the phytochemical composition and antioxidant activity of hydroalcoholic extracts obtained from leaves, roots and the whole plant, as well as to develop hydrogels with pharmaceutical potential. The hydroalcoholic extracts (70% ethanol) were characterized by spectrophotometric and HPLC-DAD methods to determine the total content of phenolic compounds, phenolic acids, flavonoids and condensed tannins. The antioxidant activity was evaluated by DPPH and ABTS methods. The extracts were included in 2% carbopol-based hydrogels and tested for stability and antioxidant efficacy. The hydroalcoholic extract of the leaves showed the highest content of total phenolic compounds (20.84 ± 2.18 mg GAE/g), total flavones (11.39 ± 2.48 mg QE/g) and condensed tannins (1.98 ± 1.55 mg CE/g), and was also the richest in quercetin (3.32 ± 1.25 mg/g), kaempferol (1.84 ± 1.63 mg/g), luteolin (2.12 ± 1.19 mg/g), rutin (4.38 ± 1.84 mg/g) and apigenin (1.91 ± 1.44 mg/g). The root extract had the highest content of phenolic acids, including ferulic acid (3.86 ± 1.37 mg/g), vanillic acid (2.53 ± 1.76 mg/g) and caffeic acid (3.28 ± 1.28 mg/g). The antioxidant activity was highest in the leaves extract, with values of 276.2 ± 3.4 µmol TE/g (ABTS) and 246.4 ± 3.6 µmol TE/g (DPPH). The whole-plant extracts showed intermediate values, offering a balance between flavonoids and phenolic acids. Hydrogels formulated with 5% extracts demonstrated stability and sustained antioxidant activity over time. Leaf extracts, due to their high flavonoid content, are recommended for formulations with antioxidant and photoprotective effects, while root extracts are suitable for anti-inflammatory and antimicrobial applications. Hydrogels obtained based on 2% carbopol represent a promising delivery system for dermato-cosmetic and pharmaceutical applications because they exhibited significant antioxidant action. Full article
(This article belongs to the Special Issue Isolation and Identification of Biologically Active Natural Compounds)
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14 pages, 2671 KiB  
Article
Ion Transport Mechanism in the Sub-Nano Channels of Edge-Capping Modified Transition Metal Carbides/Nitride Membranes
by Yinan Li, Xiangmin Xu, Xiaofeng Fang and Fang Li
Separations 2025, 12(4), 78; https://doi.org/10.3390/separations12040078 - 28 Mar 2025
Viewed by 246
Abstract
Edge-capping modified MXene membranes with new channels created by lateral nanosheets are of great research significance. After introducing tripolyphosphate (STPP) to Ti edges of Ti3C2Tx nanosheets and fabricating the STPP-MXene membranes edge-capping method, this research investigated the performance [...] Read more.
Edge-capping modified MXene membranes with new channels created by lateral nanosheets are of great research significance. After introducing tripolyphosphate (STPP) to Ti edges of Ti3C2Tx nanosheets and fabricating the STPP-MXene membranes edge-capping method, this research investigated the performance optimization mechanism of STPP-modified MXene membranes in terms of salt permeability (NaCl, Na2SO4, MgCl2, and MgSO4) and transmembrane energy barriers (Esalt) through the concentration gradient permeation test. Experimental results demonstrated an approximately 1.86-fold enhancement in salt flux (Js) compared to the MXene membranes. The solution–diffusion model was also introduced to evaluate the salt solubility (Ks) and diffusivity (Ds) during permeation. Furthermore, analysis of transmembrane energy barriers revealed that STPP modification induced significantly larger reductions in activation energy for magnesium salts (MgSO4: 55.1%; MgCl2: 47.4%) compared to sodium salts (NaCl: 30.5%; Na2SO4: 30.9%). This phenomenon indicated the weakened electrostatic interactions between high-valent Mg2+ and the modified lateral membrane Ti edges, whereas the limited charge density of Na+ resulted in relatively modest optimization. The results highlight the contribution of STPP capping on the edges of adjacent lateral nanosheets. Therefore, the modification increased the transportation rate of cations across the MXene membrane by more than twice, thus advancing the application of 2D MXene membranes in resource recovery. Full article
(This article belongs to the Special Issue Membrane Separation Process for Water Treatment)
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17 pages, 6945 KiB  
Article
Separation and Identification of Non-Volatile Sour and Bitter Substances in Amomum villosum L. by Ultra-Performance Liquid Chromatography/Quadrupole Time-of-Flight Mass Spectrometry and Electronic Tongue Analysis, as Well as Their In Vitro Anti-Tumor Activity
by Yang Chen, Ziwei Liao, Weiqin Li, Zhe Wang, Wan Tang, Qiang Yang and Jian Xu
Separations 2025, 12(4), 77; https://doi.org/10.3390/separations12040077 - 28 Mar 2025
Viewed by 245
Abstract
Amomum villosum L. is a perennial herbaceous belonging to the ginger family. Due to its unique aroma, it is widely used in alcoholic beverages and food processing. Unfortunately, issues with bitterness and sourness occur, which affect the taste and quality of processed products. [...] Read more.
Amomum villosum L. is a perennial herbaceous belonging to the ginger family. Due to its unique aroma, it is widely used in alcoholic beverages and food processing. Unfortunately, issues with bitterness and sourness occur, which affect the taste and quality of processed products. In this study, the non-volatile sour and bitter substances in Amomum villosum L. were systematically isolated, purified, and characterized through a combination of chromatographic separation techniques and ultra-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS). The results indicate that three sour compounds (DL-malic acid, protocatechuic acid, and p-hydroxybenzoic acid) and one bitter compound (catechin) were identified for the first time in Amomum villosum L. The in vitro anti-tumor activity was screened and determined using Cell Counting Kit-8 (CCK-8) assays, a 5-Ethynyl-2′-deoxyuridine (EdU) staining experiment, and scratch assays. The results reveal that the bitter substance of catechin (25–100 μg/mL) exhibited significant inhibitory effects, which inhibited the proliferation and migration of human non-small cell lung cancer A549 cells through dose-dependent mechanisms. This investigation also reveals the influence of different traditional extraction solvents on the degree of bitterness and sourness in Amomum villosum extracts, providing a theoretical basis for improving the quality and pharmacological utilization of Amomum villosum extracts. Full article
(This article belongs to the Collection Recent Trends in the Separation of Natural Products and Pharmaceuticals)
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15 pages, 3252 KiB  
Article
Adsorption of Nitrate Ions Using Magnesium-Loaded Bamboo Powder and Nano-Sized Crushed Oyster Shells
by Harada Hiroyuki, Nur Maisarah Mohamad Sarbani, Aoyagi Misturu and Jun Nishimoto
Separations 2025, 12(4), 76; https://doi.org/10.3390/separations12040076 - 27 Mar 2025
Viewed by 214
Abstract
Excess nitrate ions should be avoided in agriculture as they are absorbed by plants and ingested by humans, which can have serious effects on soil and groundwater. In this study, environmentally friendly bamboo flour and nano-sized oyster shells were used as adsorbents. The [...] Read more.
Excess nitrate ions should be avoided in agriculture as they are absorbed by plants and ingested by humans, which can have serious effects on soil and groundwater. In this study, environmentally friendly bamboo flour and nano-sized oyster shells were used as adsorbents. The equilibrium time for nitrate adsorption was found to be short, less than five minutes, and the treatment temperature had little effect on adsorption. The adsorption capacity and adsorption mechanism were investigated using experiments and adsorption isotherms. Bamboo powder treated with magnesium chloride (Mg bamboo), crushed oyster shell (oyster shell), and hydrogel induced with sodium alginate (hydrogel) were used. The maximum adsorption of nitrate ions on the magnesium-treated bamboo flour was estimated to be 399 mg NO3−/g by the Dubin–Radushakevich equation (correlation coefficient 0.84), with the Langmuir (correlation coefficient 0.91) and Freundlich (correlation coefficient 0.91) equations also fitting relatively well. The D-R equation (correlation coefficient 0.938) and Freundlich equation (correlation coefficient 0.943) also fitted oyster shells relatively well. The maximum adsorption was estimated at 354 mg NO3−/g. In oyster shell treatments where phosphate and nitrate ions were present, it was observed that both substances were adsorbed simultaneously. For the hydrogels, only the D-R equation (correlation coefficient 0.944) and the Freundlich isotherm were applicable. The maximum adsorption was estimated at 156 mg/g. Full article
(This article belongs to the Special Issue Application of Advanced Materials and Technologies in the Separation and Adsorption)
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17 pages, 2125 KiB  
Article
Competitive Adsorption Behavior of CO2 and CH4 in Coal Under Varying Pressures and Temperatures
by Yijin Zhu, Haijian Li, Jiahong Liu, Caiwen Zhou and Yunpeng Zhao
Separations 2025, 12(4), 75; https://doi.org/10.3390/separations12040075 - 27 Mar 2025
Viewed by 217
Abstract
The CO2 injection technology for replacing CH4 to enhance coalbed methane (CBM) recovery (CO2-ECBM) offers dual benefits, i.e., reducing CO2 emissions through sequestration and increasing CBM recovery, thereby leading to economic gains. However, there is no clear consensus [...] Read more.
The CO2 injection technology for replacing CH4 to enhance coalbed methane (CBM) recovery (CO2-ECBM) offers dual benefits, i.e., reducing CO2 emissions through sequestration and increasing CBM recovery, thereby leading to economic gains. However, there is no clear consensus on how temperature and pressure affect the competitive adsorption characteristics of CO2 and CH4 mixed gases in coal. Therefore, the competitive adsorption behavior of CO2 and CH4 mixed gases at various pressures and temperatures were investigated using the breakthrough curve method. Anthracite was selected for the adsorption experiment conducted under three gas injection pressure levels (0.1 MPa, 0.5 MPa, and 1 MPa) and at three temperature levels (20 °C, 40 °C, and 60 °C). This study showed that, when the temperature remained constant and the pressure ranged from 0.1 to 1 MPa, the adsorption rates of CO2 and CH4 increased as pressure rose. Additionally, the selectivity coefficient for CO2/CH4 decreased with an increase in pressure, suggesting that higher pressures within this range are not conducive to the replacement efficiency of CH4 by CO2. As the temperature increased from 20 to 60 °C under constant pressure conditions, both the selectivity coefficients for CO2/CH4 and the adsorption rates of CO2 and CH4 exhibited a downward trend. These findings imply that, within this temperature range, a reduced temperature improves the ability of CO2 to efficiently displace CH4. Moreover, CO2 exhibits a higher isosteric heat of adsorption compared to CH4. Full article
(This article belongs to the Topic Carbon Capture Science and Technology (CCST), 2nd Edition)
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12 pages, 921 KiB  
Article
Novel Triterpenes and Bioactive Compounds Isolated from Smilax canariensis Brouss. ex Willd
by Jesús G. Díaz, Samuel Vega, Daniel Ganosa, Pedro Pérez de Paz and David Díaz Diaz
Separations 2025, 12(4), 74; https://doi.org/10.3390/separations12040074 - 25 Mar 2025
Viewed by 250
Abstract
The aerial parts of Smilax canariensis Brouss. ex Willd., an endemic plant species of the Canary Islands and Madeira, were chemically investigated, resulting in the isolation of multiple known and novel compounds. These include known flavonol glycosides: quercetin-3-O-rutinoside, rutin (7 [...] Read more.
The aerial parts of Smilax canariensis Brouss. ex Willd., an endemic plant species of the Canary Islands and Madeira, were chemically investigated, resulting in the isolation of multiple known and novel compounds. These include known flavonol glycosides: quercetin-3-O-rutinoside, rutin (7), quercetin-3-O-rutinoside decaacetate (7a), kaempferol-3-O-rutinoside nonaacetate, nicotiflorin acetate (8), 2-O-p-coumaroylglycerol triacetate (10), and trans-resveratrol (9). Additionally, a new sterol, 24,24-dimethy-5α-cholesta-7,25-dien-3-one (1), and two novel dammarane-type triterpenes, 24-hydroxy-24-methyl-dammara-20,25-dien-3-one (2) and 3-acetyl-25-methyl-dammara-20,24-diene (3), were identified. In addition, stigmasterol, sitosterol, and stigmast-4-en-3-one (4) were obtained. The structural elucidation of these compounds was achieved via 1D and 2D NMR spectroscopy, mass spectrometry, and comparison with literature data. This study provides the first phytochemical profile of S. canariensis and highlights its potential as a source of bioactive compounds for pharmacological applications. Full article
(This article belongs to the Section Analysis of Natural Products and Pharmaceuticals)
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17 pages, 2543 KiB  
Article
Extraction of Anthocyanins from Black Bean Peel Based on Deep Eutectic Solvents and the Determination of Their Antioxidant Properties and Stability
by Shuangshuang Xia, Rong Fan, Haiyu Wu, Ziwei Guo, Pan Gao, Lai Wei, Min Wang and Lin Han
Separations 2025, 12(4), 73; https://doi.org/10.3390/separations12040073 - 25 Mar 2025
Viewed by 233
Abstract
To explore anthocyanins in black bean peel, the conditions of ultrasound-assisted deep eutectic solvents (DESs) were screened and optimized using the method of response surface optimization. After that, the purification of the anthocyanins was performed before investigating their antioxidant activity and stability. The [...] Read more.
To explore anthocyanins in black bean peel, the conditions of ultrasound-assisted deep eutectic solvents (DESs) were screened and optimized using the method of response surface optimization. After that, the purification of the anthocyanins was performed before investigating their antioxidant activity and stability. The results showed that the choline chloride–citric acid system was more suitable for the extraction of anthocyanins from black bean peel, and the maximum amount of 61.00 ± 2.73 mg C3GE/100 g DW anthocyanins was obtained with the following optimized conditions: extraction time, 40 min; ultrasonic power, 60 KHz; material–liquid ratio, 1:20 g/mL; and ultrasonic temperature, 50 °C. The purity of the anthocyanins increased to 193.62 mg C3GE/100 g after purification with AB-8 resin, which also significantly improved the ability to screen DPPH and ABTS radicals. The anthocyanins from black bean peel were sensitive to light, temperature, pH, and additives. Full article
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