Separations

16 pages, 1616 KiB

Open AccessArticle

Comparison of Extraction Techniques for Wide Screening of 230 Pesticides in Water

by Caterina Cacciatori, Jackie Myers, Giulio Mariani, Hung Vu, Bernd Manfred Gawlik and Vincent Pettigrove

Separations 2025, 12(6), 158; https://doi.org/10.3390/separations12060158 - 9 Jun 2025

Abstract

In this study, weekly grab samples extracted by solid-phase extraction (SPE) and stir bar sorptive extraction (SBSE) were compared for the analysis of 230 pesticides in surface waters. Samples were collected from three different locations around Melbourne, Australia. Analysis was performed using Gas [...] Read more.

In this study, weekly grab samples extracted by solid-phase extraction (SPE) and stir bar sorptive extraction (SBSE) were compared for the analysis of 230 pesticides in surface waters. Samples were collected from three different locations around Melbourne, Australia. Analysis was performed using Gas Chromatography Quadrupole Time of Flight High Resolution Mass Spectrometry (GC-QToF-HRMS). The two extraction techniques were compared, among others, for their limits of detection, recovery, extraction, and quantification efficiency of pesticides, as well as spatial and temporal differences in detected compounds. The target compounds screened were pesticides belonging mainly to the categories of fungicides, insecticides, and herbicides. Although SBSE extracted more pesticides at two out of three sites, SPE extracted total concentrations up to four times higher than SBSE over all sampling sites. The log K_OW of detected pesticides only partially explained the differences in detection, with SBSE performing better in the absorption of hydrophobic compounds. In addition, matrix effects, in particular turbidity, appeared to hinder extraction of contaminants, especially for SBSE. Spatially, SBSE detected 10 pesticides more than SPE at two locations, while the opposite was true at the third location, where turbidity was higher. The types of pesticides detected varied slightly between techniques and locations. The study highlights the complementarity of SBSE and SPE for monitoring pesticides in natural environments. SBSE is an easy-to-use technique and allows for extraction of a higher number of pesticides at trace level, but it might not be the preferred option for highly turbid waters. SPE requires more tedious and complex sample processing but allows for a more accurate quantification of a broader range of pesticides. Full article

(This article belongs to the Special Issue New Techniques for Extraction and Removal of Pesticide Residues)

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22 pages, 4495 KiB

Open AccessArticle

The Application of

S_{n}^{2 -}

in Autotrophic Denitrification Process for Advanced Nitrogen Removal in Wastewater Treatment

by Yingxue Sun, Xiaolei Zhang, Chenli Ye, Ziying He, Hongjie Wang and Ji Li

Separations 2025, 12(6), 157; https://doi.org/10.3390/separations12060157 - 8 Jun 2025

Abstract

This study presents a cost-effective and feasible technique for the deep denitrification of wastewater, based on sulfur autotrophic denitrification mediated by polysulfides (

S_{n}^{2 -}

). Various polysulfides were used as electron donors in an aerobic/anoxic sequencing batch reactor (SBR) to [...] Read more.

This study presents a cost-effective and feasible technique for the deep denitrification of wastewater, based on sulfur autotrophic denitrification mediated by polysulfides (

S_{n}^{2 -}

). Various polysulfides were used as electron donors in an aerobic/anoxic sequencing batch reactor (SBR) to simulate nitrification and denitrification processes. The performance of different polysulfide species and their respective dosages were evaluated to determine the optimal conditions for nitrogen removal. Under optimal nitrogen removal conditions with a dosing of 19.2 mg S/L from Na₂S₃, the system was operated continuously for 38 days, with low sludge production during the process. During stable operation, the system achieved an average removal of 7.3 mg/L of

N O_{3}^{-} - N

, corresponding to a removal efficiency of 23.1%. No significant accumulation of

N O_{2}^{-} - N

was observed in the effluent, and the average utilization efficiency of Na₂S₃ reached 83.7%. Continuous dosing of Na₂S₃ promoted the enrichment of sulfur autotrophic denitrification-related microorganisms within the system. Full article

(This article belongs to the Topic Sustainable Technologies for Water Purification)

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26 pages, 948 KiB

Open AccessReview

Antimony Recovery from Industrial Residues—Emphasis on Leaching: A Review

by Marinela Panayotova, Serhii Pysmennyi and Vladko Panayotov

Separations 2025, 12(6), 156; https://doi.org/10.3390/separations12060156 - 8 Jun 2025

Abstract

Antimony (Sb) is a metalloid widely used in different areas—from the cutting-edge renewable energy technologies to “classical” lead acid batteries. Its availability in primary sources is limited, and these sources are geographically unevenly distributed worldwide. Antimony use will increase in the future. That [...] Read more.

Antimony (Sb) is a metalloid widely used in different areas—from the cutting-edge renewable energy technologies to “classical” lead acid batteries. Its availability in primary sources is limited, and these sources are geographically unevenly distributed worldwide. Antimony use will increase in the future. That is why Sb is included in the critical raw material lists of the European Union and the USA. In order to mitigate the future Sb shortage, Sb recovery from industrial residues is worth considering. This paper presents the availability of Sb in nonferrous metals extraction waste and the applicability of the hydrometallurgical route for Sb recovery from such sources. Leaching is emphasized. The use of acidic and alkaline leaching methods, their recent modifications, and the effect of different process parameters (reagents’ type, solid-to-liquid ratio, temperature, and the addition of oxidizing reagents) are highlighted. The use of new leaching systems, such as deep eutectic solvents and non-aqueous solutions, is presented. Initial attempts to apply bioleaching are described. Finally, some proposals for future investigations are given. Full article

(This article belongs to the Special Issue Solid Waste Recycling and Strategic Metal Extraction)

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21 pages, 1368 KiB

Open AccessArticle

Green Extraction Combined with Chemometric Approach: Profiling Phytochemicals and Antioxidant Properties of Ten Species of the Lamiaceae Family

by Branislava Teofilović, Emilia Gligorić, Martina Ninić, Saša Vukmirović, Žarko Gagić, Nebojša Mandić-Kovačević, Biljana Tubić, Đorđe Đukanović and Nevena Grujić-Letić

Separations 2025, 12(6), 155; https://doi.org/10.3390/separations12060155 - 8 Jun 2025

Abstract

The pharmacological potential of Lamiaceae plants is primarily linked to their high content of phenolic acids and flavonoids, known for strong antioxidant properties. This study investigated the antioxidant activity of ten widely used Lamiaceae herbs—oregano, lavender, basil, savory, garden thyme, wild thyme, sage, [...] Read more.

The pharmacological potential of Lamiaceae plants is primarily linked to their high content of phenolic acids and flavonoids, known for strong antioxidant properties. This study investigated the antioxidant activity of ten widely used Lamiaceae herbs—oregano, lavender, basil, savory, garden thyme, wild thyme, sage, rosemary, lemon balm, and mint—prepared as traditional infusions and microwave-assisted extracts. The antioxidant capacity was evaluated using spectrophotometric assays, and total phenolics and flavonoids were quantified via spectrophotometry and HPLC. Chemometric analysis (PCA) was applied to explore correlations among antioxidant parameters. The results demonstrated excellent antioxidant activity across all samples. The IC50 for DPPH radicals was in the range from 3.73(0.13) to 8.03(0.17) μg/mL and that for ABTS radicals was from 2.89(0.12) to 8.55(0.34). The CUPRAC antioxidant assay delivered values in the range from 351.93(11.85) to 1129.68(44.46) μg TE/mg DE. The FRAP method produced values from 1.27(0.03) to 6.60(0.26) μmol Fe/mg DE. The presence of gallic acid was detected in all examined samples, with lemon balm and lavender exhibiting the highest concentrations across both applied extraction methods. Notably, lavender showed especially high levels of p-hydroxybenzoic acid and chlorogenic acid. Microwave-assisted extraction generally yielded higher levels of bioactive compounds compared to infusion. These findings highlight the potential of Lamiaceae herbal extracts, particularly those obtained through microwave-assisted extraction, as valuable sources of dietary antioxidants for everyday use. Full article

(This article belongs to the Special Issue Extraction and Characterization of Bioactive Compounds from Plant and Natural Sources)

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13 pages, 959 KiB

Open AccessArticle

Use of Mixed Micelles in Micellar Electrokinetic Chromatography Method for Determination of Dexamethasone, Prednisolone and Triamcinolone in Pharmaceutical Formulations

by Karen A. Escamilla-Lara, Israel S. Ibarra, Jorge Lopez-Tellez and Jose A. Rodriguez

Separations 2025, 12(6), 154; https://doi.org/10.3390/separations12060154 - 6 Jun 2025

Abstract

The unregulated consumption of corticosteroids causes significant adverse effects on human health. Therefore, it is important to develop methodologies that allow their analysis in pharmaceutical matrices with competitive analysis times and costs. The determination of corticosteroids by micellar electrokinetic chromatography (MEKC) using a [...] Read more.

The unregulated consumption of corticosteroids causes significant adverse effects on human health. Therefore, it is important to develop methodologies that allow their analysis in pharmaceutical matrices with competitive analysis times and costs. The determination of corticosteroids by micellar electrokinetic chromatography (MEKC) using a background electrolyte (BGE) composed of phosphate buffer and a micellar pseudo-stationary phase constituted by a mixture of surfactants is proposed as an alternative quantification technique. The variables involved in the BGE: phosphate concentration, surfactant (sodium dodecyl sulfate (SDS) or sodium lauryl ether sulfate (SLES)), sodium taurocholate (STC) and the pH value were optimized using a Taguchi L₉ (3⁴) experimental design. Employing the optimal BGE, the separation of the three corticosteroids is possible in a linear range of 1.05–10.0 mg L⁻¹, with limits of detection (LOD) of 0.28–0.35 mg L⁻¹. The relative standard deviation (RSD) values obtained for the repeatability (n = 3) and intermediate precision (n = 9) were less than 5.0%. Pharmaceutical formulations (ointments, injectable solution and ophthalmic solution) were analyzed using the proposed methodology (MEKC) and the official methodology (high-performance liquid chromatography, HPLC), and no significant differences were found between the corticosteroid contents obtained from both methods. Full article

(This article belongs to the Special Issue Development and Applications of Chromatographic Materials and Analytical Methods)

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11 pages, 2568 KiB

Open AccessArticle

Hydrothermal Conversion of Sn-Bearing Sludge into Fe/S Rods for Efficient Heavy Metal Removal in Wastewater

by Shengyao Ma, Wu Yang, Weilu Yang and Yu Chen

Separations 2025, 12(6), 153; https://doi.org/10.3390/separations12060153 - 6 Jun 2025

Abstract

Hydrothermal conversion is an effective strategy to transform heavy metals in electroplating sludge into catalytic materials and use them to treat electroplating wastewater. This study presents a one-step hydrothermal method for converting Sn-bearing sludge, containing 23.41% Sn, 52.12% Fe, and other impurities, into [...] Read more.

Hydrothermal conversion is an effective strategy to transform heavy metals in electroplating sludge into catalytic materials and use them to treat electroplating wastewater. This study presents a one-step hydrothermal method for converting Sn-bearing sludge, containing 23.41% Sn, 52.12% Fe, and other impurities, into Fe/S rods using a NaOH/Na₂S solution. The resulting Fe/S rods, with a diameter of 50–100 nm and length of 0.5–2.5 μm, showed excellent performance in wastewater treatment. In the presence of 50 mg/L EDTA, the Fe/S rods removed 22.9% of Ni, 30.2% of Cu, and 41.5% of Zn. When activated with PMS, the removal efficiencies increased significantly to 68.9%, 90.9%, and 91.6% for Ni, Cu, and Zn, respectively. The optimal rod dosage (1 g/L) achieved removal efficiencies of 94.2%, 78.5%, and 99.7% for Cu, Ni, and Zn, while increasing PMS dosage led to nearly 100% removal within 60 min. Additionally, the process allowed for the complete recycling of the alkaline solution, with regenerated rods showing similar performance to the original ones in wastewater treatment. This method offers an efficient and sustainable approach to sludge resource utilization and heavy metal removal from wastewater. Full article

(This article belongs to the Section Environmental Separations)

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20 pages, 15403 KiB

Open AccessArticle

Computational Study on the Separation of Pentane Isomers in Functionalized UiO-66 Metal-Organic Frameworks

by Néstor Ariel Pérez-Chávez, Matias Rafti and Alberto Gustavo Albesa

Separations 2025, 12(6), 152; https://doi.org/10.3390/separations12060152 - 4 Jun 2025

Abstract

The efficient separation of light hydrocarbons, particularly alkanes from their isomers (C₅–C₆), represents a significant and energy-intensive challenge for the petrochemical industry. Metal-Organic Frameworks (MOFs) offer promising solutions due to their exceptional porosity, surface area, and, crucially, their structural [...] Read more.

The efficient separation of light hydrocarbons, particularly alkanes from their isomers (C₅–C₆), represents a significant and energy-intensive challenge for the petrochemical industry. Metal-Organic Frameworks (MOFs) offer promising solutions due to their exceptional porosity, surface area, and, crucially, their structural and chemical tunability. This study employs advanced computational methods, including Grand Canonical Monte Carlo (GCMC) simulations and Molecular Dynamics (MD), to systematically investigate the adsorption and separation of pentane isomers (n-pentane, isopentane, and neopentane) in the UiO-66 MOF family. Specifically, the impact of organic linker functionalization with -H (parent), -NH₂, -CH₃, and -COOH groups on adsorption isotherms, isosteric heats, and competitive behavior in mixtures is evaluated. The analysis provides a molecular-level view of host-guest and guest-guest interactions, elucidating the recognition and selectivity mechanisms governing the separation of these C5 isomers and the potential for engineering MOF materials for this application. Full article

(This article belongs to the Special Issue Recent Advances in Gas Separation and Purification)

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14 pages, 1004 KiB

Open AccessArticle

Physicochemical and Phytochemical Determinations of Greek “Kollitsida’’ (Arctium lappa L.) from Different Regions and Evaluation of Its Antimicrobial Activity

by Dimitrios G. Lazaridis, Sokratis D. Giannoulis, Maria Simoni, Vassilios K. Karabagias, Nikolaos D. Andritsos, Vasileios Triantafyllidis and Ioannis K. Karabagias

Separations 2025, 12(6), 151; https://doi.org/10.3390/separations12060151 - 4 Jun 2025

Abstract

The present study aimed to investigate Greek Kollitsida root samples from different geographical regions based on physicochemical and antibacterial analyses. For this purpose, samples were treated with different solvents, deionized water (solvent A) and ethanol of grape origin (solvent B), to monitor if [...] Read more.

The present study aimed to investigate Greek Kollitsida root samples from different geographical regions based on physicochemical and antibacterial analyses. For this purpose, samples were treated with different solvents, deionized water (solvent A) and ethanol of grape origin (solvent B), to monitor if the physicochemical and phytochemical parameter values can be affected by the type of solvent. Results showed that the extraction solvent affected the physicochemical and phytochemical profile of Kollitsida. In addition, the aqueous and ethanolic extracts showed antibacterial activity against Salmonella typhimurium and Staphylococcus aureus, which was also affected by the geographical origin of Kollitsida samples. Finally, the application of multivariate analysis on the data obtained using deionized water or ethanol of grape origin as an extraction solvent for the analyses classified samples according to their geographical origin by 100%, using the cross-validation method of linear discriminant analysis. The study brings new knowledge regarding the physicochemical, phytochemical, and antibacterial profiles, along with the authenticity, of Greek Kollitsida. Full article

(This article belongs to the Special Issue Extraction and Characterization of Bioactive Compounds from Plant and Natural Sources)

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19 pages, 533 KiB

Open AccessReview

Extraction of Phenolic Compounds from Agro-Industrial By-Products Using Natural Deep Eutectic Solvents: A Review of Green and Advanced Techniques

by Fernanda de Sousa Bezerra and Maria Gabriela Bello Koblitz

Separations 2025, 12(6), 150; https://doi.org/10.3390/separations12060150 - 3 Jun 2025

Abstract

As sustainability gains prominence, the circular economy has encouraged the valorization of agri-food by-products, which are rich in phenolic compounds known for their antioxidant and anti-inflammatory properties. Conventional extraction methods commonly employ organic solvents, which contradict green chemistry principles. Natural deep eutectic solvents [...] Read more.

As sustainability gains prominence, the circular economy has encouraged the valorization of agri-food by-products, which are rich in phenolic compounds known for their antioxidant and anti-inflammatory properties. Conventional extraction methods commonly employ organic solvents, which contradict green chemistry principles. Natural deep eutectic solvents (NaDESs) have emerged as environmentally friendly alternatives for recovering bioactive compounds from food waste. This review investigated recent studies (2020–2024) on ultrasound (UAE), microwave (MAE), and pressurized liquid extraction (PLE) using NaDESs to extract phenolic compounds from agri-food by-products. A total of 116 publications were initially identified, of which 19 met the inclusion criteria. UAE combined with NaDESs proved effective, particularly for fruit and oilseed residues. MAE achieved good yields for phenolic acids and flavonoids but showed limitations on high temperatures. PLE, though less explored, demonstrated promising results when optimized for temperature, pressure, and NaDES composition. The combination of NaDESs with assisted extraction techniques enhanced yield, selectivity, and environmental performance compared to conventional approaches. These findings highlight a greener and more efficient strategy for phenolic recovery within a biorefinery framework. Ultimately, this approach contributes to the sustainable management and valorization of agri-food by-products, supporting circular economy principles and the development of cleaner extraction technologies for functional ingredients. Full article

(This article belongs to the Special Issue Green Extraction Processes to Recover Natural Bioactive Compounds from Food By-Products)

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19 pages, 3970 KiB

Open AccessArticle

Effect of Vortex Finder Wall Thickness on Internal Flow Field and Classification Performance in a Hydrocyclone

by Zaihai Wu, Peiyang Li, Zhitao Liang, Feng Li and Huanbo Yang

Separations 2025, 12(6), 149; https://doi.org/10.3390/separations12060149 - 3 Jun 2025

Abstract

The hydrocyclone generally exhibits limited separation efficiency and classification sharpness. As the discharge channel for fine particles, the vortex finder plays a critical role in influencing the classification performance through its structural parameters. However, the influence of vortex finder wall thickness on fly [...] Read more.

The hydrocyclone generally exhibits limited separation efficiency and classification sharpness. As the discharge channel for fine particles, the vortex finder plays a critical role in influencing the classification performance through its structural parameters. However, the influence of vortex finder wall thickness on fly ash classification within the hydrocyclone has not yet been reported. In this study, computational fluid dynamics (CFDs) were employed to investigate the variations in pressure field, velocity field, and separation efficiency with respect to changes in vortex finder wall thickness. The results indicate that the radial velocity increases with vortex finder wall thickness, which facilitates the rapid formation of a particle-size stratification, thereby reducing the number of misclassified particles. The cut size initially decreases and then increases as the wall thickness of the vortex finder increases. A minimum cut size of 17.2 µm was observed when the wall thickness reached 10 mm. The classification sharpness improves progressively with increasing wall thickness. At a wall thickness of 15 mm, the steepness index reaches 0.68. Experimental results demonstrate that a thick-walled vortex finder structure can significantly enhance the classification sharpness of the hydrocyclone. Specifically, the content of −19 µm particles in the underflow decreased by 32.17% when the vortex finder wall thickness increased from 5 mm to 15 mm. Meanwhile, the proportion of −19 µm particles in the overflow increased by 12.72%. Therefore, employing a thick-walled vortex finder structure can not only enhance the cut size precision but also effectively improve the classification performance of the hydrocyclone. Full article

(This article belongs to the Topic Advances in Separation Engineering)

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20 pages, 2180 KiB

Open AccessArticle

Effective Liquid–Liquid Extraction for the Recovery of Grape Pomace Polyphenols from Natural Deep Eutectic Solvents (NaDES)

by Alessandro Frontini, Giulio Tarentini, Carmine Negro, Andrea Luvisi, Massimiliano Apollonio and Luigi De Bellis

Separations 2025, 12(6), 148; https://doi.org/10.3390/separations12060148 - 2 Jun 2025

Abstract

Natural deep eutectic solvents (NaDESs) are emerging solvents for their yield when used for extraction of different molecules, including polyphenols. NaDESs are a cutting-edge technology that offers numerous advantages, including cheap cost, safety, effectiveness and environmental friendliness. However, due to NaDES’ high boiling [...] Read more.

Natural deep eutectic solvents (NaDESs) are emerging solvents for their yield when used for extraction of different molecules, including polyphenols. NaDESs are a cutting-edge technology that offers numerous advantages, including cheap cost, safety, effectiveness and environmental friendliness. However, due to NaDES’ high boiling point, the recovery and separation of compounds after the extraction is the bottleneck of the process. In this work, two affordable methods were tested for the recovery of phenolic compounds from three binary NaDESs (composed of choline chloride mixed separately with lactic acid, tartaric acid or glycerol as hydrogen bond donors): the antisolvent and the liquid–liquid extraction methods. The former was assessed by diluting the extracts with different aliquots of water, employed as antisolvent, which was ineffective. For the liquid–liquid extraction method, ethyl acetate (EtOAc), acetonitrile (ACN), 2-chlorobutane (2-CB) and 2-methyltetrahydrofuran (2-MeTHF) were compared. Except for ACN, all solvents were perfectly immiscible with the three NaDESs, forming biphasic systems that were analyzed by colorimetric assays and HPLC/MS. 2-MeTHF applied on a 10-fold water dilution of the NaDES extract reached recovery percentages higher than 90% for most of the non-anthocyanin phenols and good recovery (up to 80%) for some anthocyanins. 2-MeTHF appears to be the first known solvent capable of extracting anthocyanins from NaDESs. Finally, a two-step liquid–liquid extraction performed firstly with EtOAc and subsequently with 2-MeTHF is proposed for the separation of different phenolic fractions. Full article

(This article belongs to the Special Issue Novel Green Solvents for the Separation and Purification of Valuable Natural Ingredients)

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23 pages, 5238 KiB

Open AccessArticle

A Self-Consistent, High-Fidelity Adsorption Model for Chromatographic Process Predictions: Low-to-High Load Density and Charge Variants in a Preparative Cation Exchanger

by Gregor M. Essert, Marko Tesanovic, Sonja Berensmeier, Isabell Hagemann and Peter Schwan

Separations 2025, 12(6), 147; https://doi.org/10.3390/separations12060147 - 1 Jun 2025

Abstract

The development of ion exchange chromatography to polish biopharmaceuticals requires extensive experimental benchmarking. As part of the Design of Experiments (DoE), statistical models increased efficiency somewhat and are still state of the art; however, the capability to predict process conditions is limited due [...] Read more.

The development of ion exchange chromatography to polish biopharmaceuticals requires extensive experimental benchmarking. As part of the Design of Experiments (DoE), statistical models increased efficiency somewhat and are still state of the art; however, the capability to predict process conditions is limited due to their nature as interpolating models. Applying the DoE still requires numerous experiments and is constrained to the design space, posing a risk of missing the potential optimum. To make a leap in model-based process development, applying extrapolating models can tremendously extend the design space and also allow for process understanding and knowledge transfer. While existing chromatography modeling software explains experimental data, it often lacks predictive power for new conditions. In academic–industrial cooperation, we demonstrate a new high-fidelity model based on biophysics for developing ion-exchange chromatography in biomanufacturing, making it a general tool in rationalizing process development for the present demand of recombinant proteins and monoclonal antibodies and the emerging demand of new modalities. Using the new computational tool, we achieved predictability and attained high accuracy; with minimal experimental effort to calibrate the system, the mathematical model predicted sensitive process conditions, and even described product-related impurities, antibody charge variants. Thus, the computational tool can be deployed for process-by-design and material-by-design approaches. Full article

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18 pages, 3582 KiB

Open AccessArticle

Insights into the Adsorptive Separation of Ethylene/Ethane in LTA-Type Zeolites

by Xiaohui Zhao, Shixue Zhou, Magdy Abdelghany Elsayed, Zhongyuan Chen, Chunhui Jiang, Yongli Hu and Gumawa Windu Manggada

Separations 2025, 12(6), 146; https://doi.org/10.3390/separations12060146 - 1 Jun 2025

Abstract

Understanding the competitive adsorption mechanism is essential for the development of adsorptive separation of ethylene (C₂H₄) and ethane (C₂H₆). In this work, density functional theory calculations and molecular dynamics simulations were employed to investigate the [...] Read more.

Understanding the competitive adsorption mechanism is essential for the development of adsorptive separation of ethylene (C₂H₄) and ethane (C₂H₆). In this work, density functional theory calculations and molecular dynamics simulations were employed to investigate the adsorption of C₂H₄ and C₂H₆ in two LTA-type zeolites, ITQ-29 and 5A. The results show that the adsorption energies of the gas molecules in zeolite 5A are more negative than in ITQ-29, and the difference in adsorption energy between C₂H₄ and C₂H₆ in zeolite 5A is significantly larger than in ITQ-29, 13.3 versus 6.2 kJ/mol. Zeolite ITQ-29 demonstrates high C₂H₄/C₂H₆ ideal selectivity (43.5 at 5 ns) while exhibiting slow C₂H₄ uptake efficiency due to the small pore windows, hindering C₂H₄ diffusion (1.05 × 10⁻¹⁰ m²/s at 298 K). In contrast, zeolite 5A facilitates the faster diffusion of C₂H₄ molecules (3.25 × 10⁻⁹ m²/s at 298 K) and exhibits a modest C₂H₄/C₂H₆ selectivity of 1.11 at 5 ns in single-gas adsorption and 2.72 in equimolar binary mixture adsorption. To enhance C₂H₄/C₂H₆ selectivity, methyl phosphonic acid is introduced onto zeolite 5A to add a sieving layer that enables the C₂H₄ molecules to preferentially permeate, and the optimal coverage of methyl phosphonic acid is 50%, yielding a C₂H₄/C₂H₆ selectivity of 17.5 at 5 ns in mixture adsorption and preserving the C₂H₄ uptake efficiency. The insights into the competitive diffusion of molecules in the coating layer and inside the zeolites provide a theoretical basis for the rational design of high-performance adsorbents. Full article

(This article belongs to the Topic Oil, Gas and Water Separation Research)

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15 pages, 715 KiB

Open AccessArticle

Essential Oils as Nature’s Dual Powerhouses for Agroindustry and Medicine: Volatile Composition and Bioactivities—Antioxidant, Antimicrobial, and Cytotoxic

by Javier Rocha-Pimienta, Javier Espino, Sara Martillanes and Jonathan Delgado-Adámez

Separations 2025, 12(6), 145; https://doi.org/10.3390/separations12060145 - 1 Jun 2025

Abstract

Essential oils (EOs), which are complex mixtures of plant-derived volatile compounds, have been utilized for centuries in the medical, food, and pharmaceutical industries because of their diverse biological properties. In recent years, there has been growing interest in elucidating the bioactivities of essential [...] Read more.

Essential oils (EOs), which are complex mixtures of plant-derived volatile compounds, have been utilized for centuries in the medical, food, and pharmaceutical industries because of their diverse biological properties. In recent years, there has been growing interest in elucidating the bioactivities of essential oils and their underlying mechanisms of action. This study aimed to investigate the antioxidant, antimicrobial, and cytotoxic characteristics of Laurus nobilis, Eucalyptus camaldulensis, Rosmarinus officinalis, and Mentha suaveolens oils and relate them to their volatile compound content. The volatile compounds of the essential oils were characterized and quantified by gas chromatography, the antioxidant activity was quantified using the ABTS assay, the antibacterial activity was quantified using broth microdilution and agar diffusion techniques, and the MTT assay was used to establish the cytotoxic potential. This study revealed a significant antioxidant capacity, which correlated with the proportion of terpenes known for their antioxidant properties. The antioxidant potency was ranked in descending order: R. officinalis, M. suaveolens, E. camaldulensis, and L. nobilis. Antimicrobial testing demonstrated that all the examined essential oils were effective against the evaluated microbial species, including both Gram-positive (Listeria innocua) and Gram-negative (Escherichia coli) bacteria. Additionally, all the tested essential oils triggered cell death in the human epithelioid cervical carcinoma (HeLa) cell line. Collectively, this article highlights the promising therapeutic and alimentary potential of essential oils and underscores the need for further research to fully harness their benefits in industrial settings. Full article

(This article belongs to the Section Analysis of Natural Products and Pharmaceuticals)

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16 pages, 2258 KiB

Open AccessReview

Adsorption and Absorption Techniques for the Separation of Gaseous C2–C5 Olefins

by Fengxiang Guo, Chao Sun, Mo Xian and Huibin Zou

Separations 2025, 12(6), 144; https://doi.org/10.3390/separations12060144 - 1 Jun 2025

Abstract

Volatile C2–C5 olefins are important bulk chemicals in the polymer industry. Traditionally, C2–C5 olefins are produced from cracked petroleum resources using an energy-consuming and hazardous distillation method. Currently, volatile olefins can be produced from renewable biomass. To obtain polymer-grade volatile olefins from diversified [...] Read more.

Volatile C2–C5 olefins are important bulk chemicals in the polymer industry. Traditionally, C2–C5 olefins are produced from cracked petroleum resources using an energy-consuming and hazardous distillation method. Currently, volatile olefins can be produced from renewable biomass. To obtain polymer-grade volatile olefins from diversified resources, more sustainable and feasible separation techniques need to be developed. This review focuses on two updated separation techniques for C2–C5 olefins: (a) adsorption separation, which separates olefins through porous affinity, the pi complexation effect, and size-exclusion and gate-opening sieving, and (b) liquid absorption separation, which utilizes either organic solvents or ionic liquids for olefin separation. In this review, different separation techniques are compared in terms of their mechanisms and operation conditions in the separation of different types of C2–C5 olefins from variable resources, such as cracked ethylene/propylene/butylene/isoprene and bio-isoprene. Full article

(This article belongs to the Topic Advances in Separation Engineering)

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11 pages, 1644 KiB

Open AccessArticle

Analysis on the Main Components of Selenium-Enriched Premna microphylla Leaves and Processed Tofu

by Jianan Wang, Chunli Chen, Fangjie Mou, Bin Wang and Jingzhou Dong

Separations 2025, 12(6), 143; https://doi.org/10.3390/separations12060143 - 28 May 2025

Abstract

Premna microphylla is a medicinal plant species distributed in Southeast Asia and China. P. microphylla leaves have been widely used for processing edible gels called Chai tofu, which have many medicinal values, such as clearing heat and detoxifying. However, the main functional components [...] Read more.

Premna microphylla is a medicinal plant species distributed in Southeast Asia and China. P. microphylla leaves have been widely used for processing edible gels called Chai tofu, which have many medicinal values, such as clearing heat and detoxifying. However, the main functional components of P. microphylla leaves and Chai tofu are still unknown. In this study, selenium-enriched cultivation of P. microphylla was conducted, and the main compositions of pectins, flavonoids, total phenolics, carotenoids, chlorophylls, and proteins were separated and comparatively analyzed. The results are that kaempferol was the main composition of flavonoids, with the average contents of 5.19% DW (dried weight) in leaves and 3.83% DW in Chai tofu; the composition of the Chai tofu pectin included glucose, fructose, and mannose. Contents of phenolics, kaempferol, chlorophyll, and carotenoids were significantly increased by the selenium enrichment cultivation in a concentration-dependent manner (R² = 0.989, 0.994, 0.94, 0.948). Moreover, selenium enrichment produced selenized pectins with Se-O bonds. Selenium-enriched P. microphylla is an important plant source for functional foods. Related processing and extraction techniques deserve further research. Full article

(This article belongs to the Topic Advances in Analysis of Food and Beverages, 2nd Edition)

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13 pages, 1875 KiB

Open AccessArticle

Development and Validation of a Method for the Analysis of Multiple Pesticides in Fishery Products Using Gas Chromatography with Micro-Electron Capture Detection and Gas Chromatography–Tandem Mass Spectrometry

by Myungheon Kim, Mihyun Cho, Changkyo Seo, Jaebin Im, Changhyeon Park, Yoonmi Lee, Mi-Ra Jo, Yong-Sun Moon and Moo-Hyeog Im

Separations 2025, 12(6), 142; https://doi.org/10.3390/separations12060142 - 28 May 2025

Abstract

This study aims to develop a simultaneous analytical method for detecting 19 pesticides, including 4,4′-DDD, in fishery products using gas chromatography with micro-electron capture detection (GC-μECD) and gas chromatography–tandem mass spectrometry (GC-MS/MS). A new analytical method was developed to measure pesticide residues in [...] Read more.

This study aims to develop a simultaneous analytical method for detecting 19 pesticides, including 4,4′-DDD, in fishery products using gas chromatography with micro-electron capture detection (GC-μECD) and gas chromatography–tandem mass spectrometry (GC-MS/MS). A new analytical method was developed to measure pesticide residues in fishery products based on the modified Association of Official Analytical Chemists protocol combining quick, easy, cheap, effective, rugged, and safe (QuEChERS) and the Pesticide Analytical Manual for extraction and purification. Extraction was performed using acetonitrile containing 0.1% acetic acid, and purification was conducted with Florisil cartridges. The Florisil cartridges were more effective than QuEChERS in removing impurities and pigments during purification and also resulted in a reduced matrix effect. The validation followed Codex guidelines (CAC/GL 40). The limit of detection ranged from 2 to 3 ng/g, and the limit of quantification (LOQ) from 7 to 10 ng/g. Matrix-matched calibration curves exhibited linearity with coefficients of determination exceeding 0.99 for all target analytes. Accuracy was assessed based on recovery rates, while precision was evaluated using relative standard deviations (RSD) at three spiking levels (LOQ, 10×LOQ, and 50×LOQ). The recovery rates ranged from 62.6 to 119.1%, with RSDs of 0.4 to 19.5%, conforming to Codex guidelines. Full article

(This article belongs to the Special Issue Chemical and Contaminant Residue Analysis via Chromatography)

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14 pages, 1702 KiB

Open AccessArticle

The Development and Validation of a High-Performance Liquid Chromatographic Method for the Determination of Urinary Levels of Etoricoxib After Fabric Phase Sorptive Extraction

by Anastasia Korpeti, Natalia Manousi, Abuzar Kabir, Constantinos K. Zacharis and Erwin Rosenberg

Separations 2025, 12(6), 141; https://doi.org/10.3390/separations12060141 - 27 May 2025

Abstract

Herein, a simple and effective analytical method was developed to monitor etoricoxib concentrations in human urine samples. Etoricoxib is a nonsteroidal anti-inflammatory drug for pain and inflammation relief in conditions such as osteoarthritis and rheumatoid arthritis. To determine its concentration, fabric phase sorptive [...] Read more.

Herein, a simple and effective analytical method was developed to monitor etoricoxib concentrations in human urine samples. Etoricoxib is a nonsteroidal anti-inflammatory drug for pain and inflammation relief in conditions such as osteoarthritis and rheumatoid arthritis. To determine its concentration, fabric phase sorptive extraction (FPSE) was combined with high-performance liquid chromatography and diode array detection (HPLC-DAD). FPSE is a green sample preparation technique that utilizes sol–gel-coated fabric substrates as extraction devices, offering numerous benefits in bioanalysis. Initially, different materials were tested for their affinity towards etoricoxib. The most critical FPSE parameters (i.e., sample amount, stirring rate, and adsorption time) were optimized using a face-centered central composite design (FC-CCD), while the remaining ones were explored by means of the one-variable-at-a-time approach. Afterwards, the analytical method was validated in terms of its selectivity, linearity, sensitivity, accuracy, and precision, while the environmental sustainability and the practicality of the method were also examined. The limit of detection was 0.03 μg mL⁻¹, and the lower limit of quantification was 0.10 μg mL⁻¹. The relative standard deviation was less than 7.2% in all cases, showing good precision. The proposed approach was successfully used to monitor urinary etoricoxib concentrations in real samples obtained from a volunteer after oral drug administration. Full article

(This article belongs to the Section Chromatographic Separations)

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15 pages, 3216 KiB

Open AccessArticle

Multi-Template Molecularly Imprinted Polymers Coupled with a Solid-Phase Extraction System in the Selective Determination of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) in Environmental Water Samples

by David Aurelio-Soria, Giaan A. Alvarez-Romero, Maria E. Paez-Hernandez, I. Perez-Silva, Miriam Franco-Guzman, Gabriela Islas and Israel S. Ibarra

Separations 2025, 12(6), 140; https://doi.org/10.3390/separations12060140 - 25 May 2025

Abstract

A simple, fast, and low-cost pre-concentration methodology based on the application of multi-template molecularly imprinted polymers (mt-MIP) in a solid-phase extraction system coupled with capillary electrophoresis was developed for the determination of naproxen, diclofenac, and ibuprofen in environmental water samples. A systematic study [...] Read more.

A simple, fast, and low-cost pre-concentration methodology based on the application of multi-template molecularly imprinted polymers (mt-MIP) in a solid-phase extraction system coupled with capillary electrophoresis was developed for the determination of naproxen, diclofenac, and ibuprofen in environmental water samples. A systematic study of the mt-MIP composition was conducted using a second-order simplex lattice experiment design (fraction of the functional monomer methacrylic acid (MAA), the total moles of functional monomers, and the total moles of the cross-linker agent). The optimal mt-MIP, consisting of 0.025 mmol of each analyte, with 2.40 mmol of methacrylic acid (MAA) and 3.60 mmol of 4-vinylpyridine (4VP) and 23.00 mmol of the cross-linker agent (EGDMA), was coupled to an SPE system under the optimal conditions: pH = 3.5; 20 mg of mt-MIP; and an eluent (MeOH/NaOH [0.001]). This methodology provides limits of detection from 3.00 to 12.00 µg L⁻¹ for the studied NSAIDs. The methodology’s precision was evaluated in terms of inter- and intra-day repeatability, with %RSD < 10% in all cases. Finally, the proposed method can be successfully applied in the analysis of environmental water samples (bottle, tap, cistern, well, and river water samples), which demonstrates the developed method’s robustness. Full article

(This article belongs to the Section Materials in Separation Science)

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