Separations

14 pages, 680 KiB

Open AccessArticle

Ultrasound-Assisted Extraction of Phenolic Compounds and Flavonoids from Banana Inflorescence and Characterization of Its Fibrous Residue

by Fábio Dias Bertoco Júnior, Érica Marusa Pergo Coelho, Mirian Cristina Feiten and Beatriz Cervejeira Bolanho Barros

Separations 2025, 12(5), 109; https://doi.org/10.3390/separations12050109 - 25 Apr 2025

Abstract

The banana inflorescence (BI) is a rich source of antioxidants and dietary fiber, making it a valuable by-product of banana harvesting. This study aimed to maximize the ultrasound-assisted extraction (UAE) of antioxidant compounds from BI and analyze the residue’s composition and functional properties. [...] Read more.

The banana inflorescence (BI) is a rich source of antioxidants and dietary fiber, making it a valuable by-product of banana harvesting. This study aimed to maximize the ultrasound-assisted extraction (UAE) of antioxidant compounds from BI and analyze the residue’s composition and functional properties. The Box–Behnken Design was applied to test different ultrasound powers, temperatures, and sample-to-solvent ratios on the total phenolic content (TPC) and total flavonoid content (TFC). The UAE conducted at 350 W, 55 °C, 1:30 (g/mL) ratio for 30 min resulted in the highest TPC (1637.12 mg/100 g) and TFC (22.97 mg/100 g). Isovanillin, caffeine, naringin, sinapaldehyde, nicotinic acid, quinic acid, malic acid, and fumaric acids were reported for the first time for BI. The extract obtained by UAE showed a higher content of these compounds and higher antioxidant activity than that obtained through conventional extraction (orbital shaking). The residue obtained after UAE presented dietary fiber as the main component (71.91 g/100 g) and a higher oil absorption index (5.78 g/g) than untreated BI. Therefore, BI is a source of bioactive compounds, and both the extract and residue can be used in the pharmaceutical, food, and cosmetic industries, enabling the productive sector to move closer to the circular economy. Full article

(This article belongs to the Special Issue Application of Sustainable Separation Techniques in Food Processing)

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14 pages, 1759 KiB

Open AccessArticle

Electrochemical Precipitation of Struvite from Wastewater: A Sustainable Approach for Nitrogen Recovery

by Rúbia Mores, Anildo Cunha Junior, Fabiane Goldschmidt Antes, Marco Di Luccio, Carolina E. Demaman Oro, Marcus V. Tres, Clarice Steffens, Juliana Steffens, Airton Kunz and Rogério Marcos Dallago

Separations 2025, 12(5), 108; https://doi.org/10.3390/separations12050108 - 25 Apr 2025

Abstract

This study evaluates the feasibility of nitrogen recovery from wastewater via electrochemical methods as an alternative nutrient source for agricultural applications. Ammonium nitrogen (NH₄⁺-N) and phosphate (PO₄³⁻-P) contamination poses significant environmental risks and challenges water resource management [...] Read more.

This study evaluates the feasibility of nitrogen recovery from wastewater via electrochemical methods as an alternative nutrient source for agricultural applications. Ammonium nitrogen (NH₄⁺-N) and phosphate (PO₄³⁻-P) contamination poses significant environmental risks and challenges water resource management globally. The electrochemical precipitation of struvite (MgNH₄PO₄·6H₂O) offers a promising solution for nutrient recovery, with potential applications as a slow-release fertilizer. Experimental results demonstrate that increased current density (from 2.5 to 7.5 mA/cm²) and reduced electrode distance (1 cm) significantly enhance NH₄⁺ and PO₄³⁻ consumption and struvite precipitation. Increasing the amperage from 2.5 to 7.5 mA·cm⁻² at a 1 cm electrode distance raised the ammoniacal nitrogen incorporation from 1.59 to 5.34 g/100 g, signifying greater struvite production. The Mg and P concentrations were 15.44 and 12.60 g/100 g, respectively, for this higher amperage, although lower than the concentrations seen with 2.5 mA·cm⁻² (22.16 and 14.52 g/100 g). The majority of Mg (60%) and P (93.6%) were, however, incorporated within struvite. Additionally, this study reveals that Mg is primarily incorporated as struvite when using higher current densities, while lower current densities yield greater Mg incorporation in non-struvite forms, such as magnesium carbonate. Findings suggest that optimizing current density and electrode distance can improve nitrogen and phosphorus recovery efficiencies, making electrochemical struvite production a viable, sustainable approach for nutrient recycling. This method not only reduces dependence on synthetic fertilizers but also supports sustainable agricultural practices by transforming wastewater contaminants into valuable resources. Full article

(This article belongs to the Special Issue Application of Sustainable Separation Techniques in Food Processing)

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17 pages, 3618 KiB

Open AccessArticle

Polymer-Coated Nickel Nanoparticles for CO₂ Capture in Seawater

by Abhishek, Abhishek Ratanpara, Adib Mahmoodi Nasrabadi and Myeongsub Kim

Separations 2025, 12(5), 107; https://doi.org/10.3390/separations12050107 - 24 Apr 2025

Abstract

Carbon capture and storage (CCS) technologies are employed to mitigate global warming by removing carbon from the atmosphere. To enhance carbon capture efficiency, nanoparticles have gained considerable attention as catalysts due to their large surface area, tunable properties, regeneration, and enhanced reactivity. However, [...] Read more.

Carbon capture and storage (CCS) technologies are employed to mitigate global warming by removing carbon from the atmosphere. To enhance carbon capture efficiency, nanoparticles have gained considerable attention as catalysts due to their large surface area, tunable properties, regeneration, and enhanced reactivity. However, it poses some challenges, such as nanoparticle aggregation and reduced effectiveness in sustainable solvents like seawater. To address these limitations and promote an environmentally sustainable method for carbon capture, this study evaluates the CO₂ capture efficiency of seawater using nickel nanoparticles (NiNPs) coated with polyvinylpyrrolidone (PVP) as a catalyst. We examined the time-dependent size variations of CO₂ bubbles in a flow-focusing microchannel using high-speed bubble-based microfluidics, directly associated with transitory CO₂ dissolution into the surrounding solution. We hypothesized that smaller polymer-coated NiNPs, due to their higher surface-to-volume ratio, can enhance CO₂ solubility and capture rates under identical environmental conditions. To verify this, polymer-coated NiNPs of three different sizes—5 nm, 10 nm, and 20 nm—were synthesized and tested. The experiments revealed that 5 nm NiNPs achieved a CO₂ dissolution rate of 77%, in contrast to 71% for 10 nm and 43% for 20 nm particles. These findings validate the hypothesis, demonstrating that smaller nanoparticles facilitate more effective CO₂ capture using equivalent material quantities, thereby potentially improving the overall efficiency of CO₂ reduction. This innovative approach contributes to advancing NiNP-based catalysts for saltwater-based CO₂ capture. 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, 2586 KiB

Open AccessArticle

Enhanced Selective Separation of Pu(IV) and U(VI) Using Novel Diethylene Glycolamide Ligand

by Xiaoyun Guo, Junli Wang, Yao Liu, Haojun Zhao, Hui Wang, Wentao Wang, Baole Li and Taihong Yan

Separations 2025, 12(5), 106; https://doi.org/10.3390/separations12050106 - 23 Apr 2025

Abstract

Developing a new efficient separation ligand based on the “CHON” principle to address the limitations of phosphorus containing extractants in nuclear fuel reprocessing can help further simplify the process flow and reduce the amount of secondary waste. Building upon this critical need, a [...] Read more.

Developing a new efficient separation ligand based on the “CHON” principle to address the limitations of phosphorus containing extractants in nuclear fuel reprocessing can help further simplify the process flow and reduce the amount of secondary waste. Building upon this critical need, a novel ligand was developed through a strategic application of the Hard and Soft Acids and Bases (HSAB) theory, integrating a soft donor nitrogen atom into the linear architecture of bis-diglycolamide. This groundbreaking ligand, named N,N′-bis[2-(2-(N,N-dioctylcarbamoyl)ethoxy)ethylacetamido]-N″-diethylenetriamine (TOMDEA-BisDGA), has demonstrated remarkable potential in the extraction of Pu(IV). The study unveils that the ligand demonstrates remarkable selectivity and separation efficiency towards Pu(IV) ions while maintaining an exceptionally low extraction capacity for U(VI) across a wide acidity spectrum of 0.1~6 mol/L. To explain the structure properties of complex formed by the ligand and Pu(IV), a systematic analysis was performed, including slope analysis, proton nuclear magnetic resonance (NMR) titration, and Fourier-transform infrared (FT-IR) spectroscopy. This study explores the coordination and separation behavior of diglycolamide ligands with actinide. This work is expected to provide important information and theoretical bases upon which advanced design and optimization of ligands for high-performance processes for the separation of plutonium might be carried out. Such findings will contribute to the understanding of actinide chemistry and further the design of improved separation methods for nuclear applications. Full article

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6 pages, 761 KiB

Open AccessTechnical Note

Optimizing Liquid Electron Ionization Interface to Boost LC-MS Instrumental Efficiency

by Tommaso Grazioso, Genny Grasselli, Adriana Arigò, Giorgio Famiglini and Achille Cappiello

Separations 2025, 12(5), 105; https://doi.org/10.3390/separations12050105 - 23 Apr 2025

Abstract

Liquid Electron Ionization (LEI) is a powerful and robust interface for the qualitative and quantitative analysis of medium-low-molecular-weight compounds, including numerous environmental pollutants and toxicological substances. Although the robustness and performance of this interface have already been demonstrated, research on its optimization can [...] Read more.

Liquid Electron Ionization (LEI) is a powerful and robust interface for the qualitative and quantitative analysis of medium-low-molecular-weight compounds, including numerous environmental pollutants and toxicological substances. Although the robustness and performance of this interface have already been demonstrated, research on its optimization can still improve instrumental performance in terms of detectability. In this study, different setups of the interface’s vaporization micro-channel (VMC) made using different capillaries and various sizes were tested to evaluate the correspondent instrumental performance. The results show that a new combination of capillaries in the interface set up significantly improves instrumental detectability, reaching LOD values almost five times lower than those of the previous setup. Full article

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13 pages, 2822 KiB

Open AccessArticle

A Two-Dimensional Thiotitanate Ion Exchanger with High Cs⁺ Removal Performance

by Chang Wei, Shaoqing Jia, Yingying Zhao, Jiating Liu, Haiyan Sun, Meiling Feng and Xiaoying Huang

Separations 2025, 12(5), 104; https://doi.org/10.3390/separations12050104 - 22 Apr 2025

Abstract

¹³⁷Cs is a persistent β/γ-emitter (t_1/2 = 30.1 years) generated from ²³⁵U and ²³⁹Pu fission. It is a critical challenge to efficiently capture ¹³⁷Cs⁺ for nuclear waste management due to its high solubility, [...] Read more.

¹³⁷Cs is a persistent β/γ-emitter (t_1/2 = 30.1 years) generated from ²³⁵U and ²³⁹Pu fission. It is a critical challenge to efficiently capture ¹³⁷Cs⁺ for nuclear waste management due to its high solubility, environmental mobility, and propensity for biological accumulation. Herein, we prepare a two-dimensional (2D) thiotitanate Rb_0.32TiS₂·0.75H₂O (denoted Rb-TiS₂) using a special molten salt synthesis method, “Mg + RbCl”. Rb-TiS₂ can selectively capture Cs⁺ from aqueous solutions. Its structure features a flexible anionic thiotitanate layer with Rb⁺ as counter ions located at the interlayer spaces. As an ion exchanger, it possesses high adsorption capacity (q_m^Cs = 232.70 mg·g⁻¹), rapid kinetics (the removal rate R > 72% within 10 min), and a wide pH tolerance range (pH = 4–12) for Cs⁺ adsorption. Through a single-crystal X-ray structural analysis, we elucidated the mechanism of Cs⁺ capture, revealing the ion exchange pathways between Cs⁺ and Rb⁺ in Rb-TiS₂. This work not only provides an important reference for the synthesis of transition metal sulfides with alkali metal cations but also proves the application prospect of transition metal sulfides in radionuclide remediation. Full article

(This article belongs to the Special Issue Separation Technology for Metal Extraction and Removal)

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19 pages, 3171 KiB

Open AccessArticle

Nonylphenol Removal from Water and Wastewater with Alginate-Activated Carbon Beads

by Angelica A. Chacon, Elizabeth Noriega Landa, Sheng Yin, Ahsan Habib, Kiana L. Holbrook, Luis R. Duran Bojorquez, Sabur Badmos, Dino Villagrán and Wen-Yee Lee

Separations 2025, 12(5), 103; https://doi.org/10.3390/separations12050103 - 22 Apr 2025

Abstract

In this study, eco-friendly and sustainable alginate-activated carbon (Alg-C)-based beads were synthesized and characterized for the adsorption of nonylphenols (NPs) from aqueous environments under various conditions. The surface characterization, functional groups, and adsorption behavior were analyzed using multiple analytical techniques. The effect of [...] Read more.

In this study, eco-friendly and sustainable alginate-activated carbon (Alg-C)-based beads were synthesized and characterized for the adsorption of nonylphenols (NPs) from aqueous environments under various conditions. The surface characterization, functional groups, and adsorption behavior were analyzed using multiple analytical techniques. The effect of key parameters, including dosage, pH, temperature, and reusability, were evaluated. Isotherm and kinetic studies revealed that the adsorption process followed a pseudo-second-order kinetic model and aligned with the Freundlich isotherm, indicating a heterogeneous surface. The beads exhibited a high removal efficiency of 97% over five reuse cycles in a 50 mL solution of 10 mg L⁻¹ NPs under static conditions, demonstrating their recyclability. Thermodynamic analysis suggested potential electrostatic interactions, supported by positive Gibbs free energy values. The highest removal performance was achieved within 90 min, with adsorption capacities from 0.10 to 0.39 mg g⁻¹. Additionally, the performance of Alg-C beads remained stable across different pH levels, highlighting their robustness. When tested with wastewater samples, Alg-C beads maintained high removal efficiency, with no significant matrix effects observed. These results underscore Alg-C beads as a promising and sustainable solution for the elimination of NPs from contaminated water sources. Full article

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12 pages, 3159 KiB

Open AccessArticle

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

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

Open AccessArticle

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

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 Fe₁C_0.2 composite was 97.1% when the mass ratio of FeOCl and BC was 1:0.2 (Fe₁C_0.2), which was higher than that of the pure components (FeOCl or BC) at pH = 6.1. Moreover, after five reuses, the Fe₁C_0.2 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 Fe₁C_0.2 composite was mainly dominated by •OH; however, •O₂⁻ and h⁺ played minor roles. The synthesized Fe₁C_0.2 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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28 pages, 19278 KiB

Open AccessArticle

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

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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18 pages, 3306 KiB

Open AccessArticle

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

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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13 pages, 4706 KiB

Open AccessArticle

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

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

Open AccessReview

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

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

Open AccessArticle

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

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

Open AccessReview

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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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