Separations

15 pages, 732 KiB

Open AccessArticle

Assessment of Green Extraction Techniques in the Utilization of Oak Tree (Quercus robur) and Mugwort (Artemisia vulgaris) Biomass for the Production of Bioactive Extracts

by David Villanueva-Bermejo, Diego Martín Hernández, Elvis Judith Hernández, Susana Santoyo and Tiziana Fornari

Separations 2025, 12(1), 17; https://doi.org/10.3390/separations12010017 - 18 Jan 2025

Viewed by 342

Abstract

The aim of this study was to investigate the suitability of Pressurized Liquid Extraction (PLE) and Supercritical Fluid Extraction (SFE) for Quercus robur bark and Artemisia vulgaris extraction. PLE of Q. robur and A. vulgaris were carried out at different temperatures with water, [...] Read more.

The aim of this study was to investigate the suitability of Pressurized Liquid Extraction (PLE) and Supercritical Fluid Extraction (SFE) for Quercus robur bark and Artemisia vulgaris extraction. PLE of Q. robur and A. vulgaris were carried out at different temperatures with water, ethanol and several hydroalcoholic mixtures. SFE of A. vulgaris was performed at different pressures and ethanol concentrations. The anti-inflammatory activity of Q. robur extracts, the antibacterial activity of A. vulgaris extracts and the antioxidant activity of the extracts from both materials were determined. The highest phenolic compound content and antioxidant activity of Q. robur extracts were achieved with water at 100 °C (487.97 mg GAE/g and 3741 µg trolox/g). The highest values for A. vulgaris extracts were obtained with ethanol at 200 °C (149.16 mg/g and 437.13 µmol/g). The ethanolic extract at 150 °C from A. vulgaris had a noticeable anti-inflammatory activity (inhibition of TNF-α and IL-6 secretion near basal values and inhibition of IL-1β higher than 80% at 20 µg/mL). A. vulgaris extracts obtained by SFE exerted antibacterial activity against E. coli (IC₅₀ of 1388 µg/mL with neat SCCO₂ at 15 MPa) and S. aureus (1406 µg/mL using SCCO₂ with 10% ethanol). Full article

(This article belongs to the Special Issue Research Progress for Isolation of Plant Active Compounds)

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17 pages, 4657 KiB

Open AccessArticle

Adsorption and Recovery Studies of Cadmium and Lead Ions Using Biowaste Adsorbents from Aqueous Solution

by Liang Feng and Enju Wang

Separations 2025, 12(1), 16; https://doi.org/10.3390/separations12010016 - 17 Jan 2025

Viewed by 445

Abstract

The use of low-cost biowaste adsorbents for the removal of toxic metal ions from aqueous solutions offers significant environmental benefits. This research evaluated the adsorption and recovery of Cd²⁺ and Pb²⁺ ions in batch and column modes with luffa peels and [...] Read more.

The use of low-cost biowaste adsorbents for the removal of toxic metal ions from aqueous solutions offers significant environmental benefits. This research evaluated the adsorption and recovery of Cd²⁺ and Pb²⁺ ions in batch and column modes with luffa peels and chamomile flowers. The biosorbents were treated with 0.4 M nitric acid or with 0.4 M NaOH base. An FTIR analysis of the sorbents indicated that surface OH, C=O, CO and COO groups played a role in the adsorption process. L-type isotherms were obtained for Pb²⁺, fitting both the Langmuir and Freundlich models, with maximum adsorption capacities of 34.0 mg/g for luffa peels and 49.5 mg/g for chamomile flowers. Adsorption isotherms for Cd²⁺ ion fit better with the Freundlich model with smaller adsorption capacity than Pb²⁺. Base-treated sorbents have higher adsorption capacity. The adsorption kinetic for both ions are fast and followed a pseudo-second order chemosorption model. Fixed-bed column dynamic adsorption with luffa peels obtained a Thomas dynamic adsorption capacity of 32.9 mg/g for Pb²⁺ and 25.8 mg/g for Cd²⁺. The recovery efficiency was 87 to 90% over three adsorption–regeneration cycles. Full article

(This article belongs to the Section Environmental Separations)

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13 pages, 4180 KiB

Open AccessArticle

Enhanced Ciprofloxacin Ozonation Degradation by an Aqueous Zn-Cu-Ni Composite Silicate: Degradation Performance and Surface Mechanism

by Yue Liu, Rong Guo, Jie Li, Yizhen Cheng, Congmin Wang, Weiqiang Wang and Huifan Zheng

Separations 2025, 12(1), 15; https://doi.org/10.3390/separations12010015 - 15 Jan 2025

Viewed by 379

Abstract

This study investigates the environmental significance of ciprofloxacin as an emerging contaminant and the need for effective degradation methods. The chemical coprecipitation method was used in this study to prepare the Zn-Cu-Ni composite silicate, serving as a heterogeneous ozonation catalyst. The catalytic activity [...] Read more.

This study investigates the environmental significance of ciprofloxacin as an emerging contaminant and the need for effective degradation methods. The chemical coprecipitation method was used in this study to prepare the Zn-Cu-Ni composite silicate, serving as a heterogeneous ozonation catalyst. The catalytic activity was then evaluated by degrading ciprofloxacin (CIP). Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption–desorption, and Fourier transform infrared analysis (FTIR) were used to characterize the Zn-Cu-Ni composite silicate. The catalyst had a high surface area (308.137 m²/g), no regular morphology, and a particle size of 7.6 µm and contained Si-O-Si, Ni-O-Si, and Zn-O-Si. The results showed that the CIP degradation and mineralization rates (pH 7.0, CIP 3.0 mg/L, Ozone 1.5 mg/L) were significantly enhanced in the presence of the Zn-Cu-Ni composite silicate. The CIP and total organic carbon (TOC) removal rates were increased by 51.09% and 18.72%, respectively, under optimal conditions, compared with ozonation alone. The adsorption of Zn-Cu-Ni composite silicate, ozone oxidation, and ·OH oxidation synergistically promoted the efficient removal of CIP. This study provides valuable catalytic ozone technology for degradation of antibiotics in wastewater to reduce environmental pollution with potential practical applications. Full article

(This article belongs to the Special Issue Application of Composite Materials in Wastewater Treatment)

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22 pages, 3209 KiB

Open AccessReview

Microextraction-Based Techniques for the Determination of Beta-Blockers in Biological Fluids: A Review

by Styliani Nisyriou and Constantinos K. Zacharis

Separations 2025, 12(1), 14; https://doi.org/10.3390/separations12010014 - 12 Jan 2025

Viewed by 524

Abstract

Sample preparation is a critical step in the analytical process. Apart from the traditional sample cleanup approaches, microextraction-based techniques have attracted much attention in recent years and especially from researchers working in the analysis of beta-blockers. Developing sensitive and selective analytical methods is [...] Read more.

Sample preparation is a critical step in the analytical process. Apart from the traditional sample cleanup approaches, microextraction-based techniques have attracted much attention in recent years and especially from researchers working in the analysis of beta-blockers. Developing sensitive and selective analytical methods is essential for detecting these compounds in complex matrices. The present review aims to provide an overview of microextraction-based analytical techniques for the determination of beta-blockers in biological samples, covering a time frame of the last decade. Detailed information on materials/coatings and instrumental configurations are provided. Full article

(This article belongs to the Section Bioanalysis/Clinical Analysis)

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Graphical abstract

16 pages, 3550 KiB

Open AccessArticle

Phase Equilibrium of CO₂ Hydrate with Rubidium Chloride Aqueous Solution

by Ryonosuke Kasai, Leo Kamiya and Ryo Ohmura

Separations 2025, 12(1), 13; https://doi.org/10.3390/separations12010013 - 11 Jan 2025

Viewed by 688

Abstract

Salt lakes are a rich source of metals used in various fields. Rubidium is found in small amounts in salt lakes, but extraction technology on an industrial scale has not been developed completely. Clathrate hydrates are crystalline compounds formed by the encapsulation of [...] Read more.

Salt lakes are a rich source of metals used in various fields. Rubidium is found in small amounts in salt lakes, but extraction technology on an industrial scale has not been developed completely. Clathrate hydrates are crystalline compounds formed by the encapsulation of guest molecules in cage-like structures made of water molecules. One of the most important properties for engineering practices of hydrate-based technologies is the comprehension of the phase equilibrium conditions. Phase equilibrium conditions of CO₂ hydrate in rubidium chloride aqueous solution with mass fractions of 0.05, 0.10, 0.15 and 0.20 were experimentally investigated in the pressure range from 1.27 MPa to 3.53 MPa, and the temperature was from 268.7 K to 280.6 K. The measured equilibrium temperature in this study decreased roughly in proportion to the concentration of the RbCl solution from the pure water system. This depression is due to the lowering of the chemical potential of water in the liquid phase by the dissolution of RbCl. Experimental results compared with other salt solution + CO₂ hydrate systems showed that the equilibrium temperatures decreased to a similar degree for similar mole fractions. Full article

(This article belongs to the Special Issue Green and Efficient Separation and Extraction of Salt Lake Resources)

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12 pages, 2610 KiB

Open AccessArticle

Separation Process for Methanol–Methylal–Methyl Formate Multicomponent System in Polyformaldehyde Production Waste Liquid: Modeling and Techno-Economic Analysis

by Huajie Liu, Jun Fan, Weiping Liu, Yong Wang, Qiuhong Ai and Yonglin Li

Separations 2025, 12(1), 12; https://doi.org/10.3390/separations12010012 - 10 Jan 2025

Viewed by 353

Abstract

The vapor–liquid equilibrium (VLE) data of the ternary system methanol–methyl formate–methylal was measured at atmospheric pressure using a modified Rose equilibrium kettle with vapor–liquid double circulation method. The experiment data were correlated with the NRTL, UNIQUAC, and Wilson activity coefficient model equations. The [...] Read more.

The vapor–liquid equilibrium (VLE) data of the ternary system methanol–methyl formate–methylal was measured at atmospheric pressure using a modified Rose equilibrium kettle with vapor–liquid double circulation method. The experiment data were correlated with the NRTL, UNIQUAC, and Wilson activity coefficient model equations. The results shown that the root mean square deviation (RMSD) between the calculated and simulated values of the three models followed the order: UNIQUAC ≈ NRTL < Wilson, and except for the RMSD (T) in the range of 0.4–0.5, the others are less than 0.01. In addition, the NRTL model was selected to link with Aspen Plus software to simulate the separation process of polyformaldehyde (POM) waste liquid. The simulation results show that the methyl formate in POM waste stream can be purified by simple distillation, while the methylal separated from the POM waste liquid, which was affected by factors like the azeotropic behavior of binary components, necessitates a complex distillation process. Under optimal operating conditions, the recovery yield of methyl formate through direct distillation can reach 99.7%, with an economic benefit of 6960.1 CNY per ton of waste liquid. Although the economic benefit of the multi-component distillation reach 7281.2 CNY, the increase in the number of equipment and the complexity of the process have negative impacts. Full article

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30 pages, 2179 KiB

Open AccessReview

Advancements in Microextraction by Packed Sorbent: Insights into Sorbent Phases and Automation Strategies

by Rafael Oliveira Martins, João Victor Basolli Borsatto, Camila Will and Fernando Mauro Lanças

Separations 2025, 12(1), 11; https://doi.org/10.3390/separations12010011 - 8 Jan 2025

Viewed by 524

Abstract

Miniaturized solid-based approaches have added an eco-friendly dimension to analytical procedures, establishing themselves as promising strategies for a wide range of applications. Among these, microextraction by packed sorbent (MEPS) stands out due to its ability to facilitate efficient sample interaction with a densely [...] Read more.

Miniaturized solid-based approaches have added an eco-friendly dimension to analytical procedures, establishing themselves as promising strategies for a wide range of applications. Among these, microextraction by packed sorbent (MEPS) stands out due to its ability to facilitate efficient sample interaction with a densely packed sorb ent phase within the microextraction system. MEPS offers several advantages, including preconcentration capabilities and the use of minimal sample and solvent volumes, making it an appealing choice for modern analytical workflows. Since the extraction efficiency is largely dictated by the sorbent phase, recent advancements in sorbent design have garnered considerable attention in the field of sample preparation. Innovations in sorbent phases have not only enhanced the MEPS efficiency but also enabled the development of semi- and fully automated systems, paving the way for high-throughput methodologies. These advancements have elevated MEPS beyond traditional offline miniaturized sample preparation methods, offering new opportunities for streamlined and scalable analyses. Therefore, this study provides a comprehensive overview of novel sorbent phases used in MEPS, with a particular focus on both bio-based and synthetic materials. Furthermore, it explores the semi- and fully automated aspects of MEPS, highlighting current trends, technological advancements, and future directions in this rapidly evolving field. Full article

(This article belongs to the Special Issue Separation Techniques on a Miniaturized Scale)

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16 pages, 2116 KiB

Open AccessArticle

Adsorption of Sinapine from Rapeseed Protein Production Effluent to Cation Exchange Resins

by Fatima Zahra Kdah, Arnaud Aymes, Luna Beau, Armelle Ropars, Jean-Pol Frippiat and Romain Kapel

Separations 2025, 12(1), 10; https://doi.org/10.3390/separations12010010 - 7 Jan 2025

Viewed by 466

Abstract

Sinapine adsorption was studied on four weak cation exchanges at pHs ranging from 2 to 8. The best adsorption rate was observed with C106 resin at pH 4 (95.25%). The adsorption kinetics followed a pseudo-second-order model while the isotherm data better fitted the [...] Read more.

Sinapine adsorption was studied on four weak cation exchanges at pHs ranging from 2 to 8. The best adsorption rate was observed with C106 resin at pH 4 (95.25%). The adsorption kinetics followed a pseudo-second-order model while the isotherm data better fitted the Langmuir model. The ΔG°, ΔH°, and ΔS° values (−25.834 kJ·mol⁻¹, −24.428 kJ·mol⁻¹, and 0.004 kJ·mol⁻¹·K⁻¹) revealed that the adsorption process was spontaneous and exothermic. Acidified ethanol showed a better desorption rate (75.41%), while virtually no (3.32%) or low (31.14%) sinapine desorption was observed with 50% ethanol and 0.1 M HCl solution, respectively. This indicated that sinapine adsorption took place throughout both ionic and hydrophobic interactions. Very close sinapine adsorption performances were observed with an effluent of the patented rapeseed protein isolate process. Two-step desorption using 50% ethanol, then acidified ethanol, yielded a highly purified neutral sinapine-derivative phenol fraction (75.23%) in the first elution fraction and sinapine (98.85%) in the second one. Full article

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23 pages, 385 KiB

Open AccessArticle

Bioactive Properties of Pentacalia vaccinioides (Kunth) Cuatrec. (Asteraceae) Essential Oils: Evaluation of Antimicrobial and Antioxidant Activities

by Luis G. Sequeda-Castañeda, María A. Castellanos-Gómez and Carlos L. A. Céspedes-Acuña

Separations 2025, 12(1), 9; https://doi.org/10.3390/separations12010009 - 5 Jan 2025

Viewed by 592

Abstract

Essential oils (EOs) have unique properties, such as antibacterial, antioxidant, and antiviral activities, which are beneficial in various industries, including cosmetics, food, and pharmaceuticals. In this study, the antioxidant and antimicrobial activities of Pentacalia vaccinioides EOs obtained from leaves and flowers (fresh and [...] Read more.

Essential oils (EOs) have unique properties, such as antibacterial, antioxidant, and antiviral activities, which are beneficial in various industries, including cosmetics, food, and pharmaceuticals. In this study, the antioxidant and antimicrobial activities of Pentacalia vaccinioides EOs obtained from leaves and flowers (fresh and dried plant material) were evaluated using hydrodistillation (HD), steam distillation (SD), simultaneous distillation–extraction (SDE), and solid-phase microextraction (SPME) techniques. Antimicrobial activity (minimum inhibitory concentration, MIC) and antioxidant capacity (half-maximal inhibitory concentration, IC₅₀) were determined. The identification and quantification of the compounds present in the EOs were conducted by gas chromatography coupled to mass spectrometry (GC-MS). The main secondary metabolites identified in most samples obtained by different extraction techniques included phenol (~18%), 1S-α-pinene (~15%), β-phellandrene (~13%), β-pinene (~12%), 4-terpineol (~10%), γ-terpinene (~10%), trans-nerolidol (~8%), limonene (~8%), and β-thujene (~6%). EOs obtained by HD, SD, and SDE exhibited antioxidant activity, with IC₅₀ values between 621.7 and 696.6 µg/mL. Additionally, the EOs demonstrated bactericidal activity against Bacillus subtilis and Staphylococcus aureus, with MIC values of 5.0 and 45 µg/mL, respectively. Escherichia coli and Pseudomonas aeruginosa did not show antimicrobial susceptibility to EOs. This study constitutes the first evaluation of Pentacalia vaccinioides EOs, demonstrating their bioactive potential and the relevance of the extraction method. The findings highlight this species as a promising source of natural compounds for therapeutic and preservative applications, depending on the type of plant material and extraction technique used. Future research should investigate how microclimatic conditions and plant development affect the chemical composition and elucidate the molecular mechanisms behind the observed bioactivities to better understand their cellular actions. Furthermore, the evaluation of the applications of EOs and hydrolates in the pharmaceutical and food industries, along with the exploration of the bioactive potential of extraction-derived hydrolates, offers a promising avenue to maximize plant utility. Full article

(This article belongs to the Special Issue Essential Oils: Extraction, Chemical Composition, and Bioactivities)

17 pages, 2691 KiB

Open AccessArticle

Phytochemical Profile Screening and Selected Bioactivity of Myrtus communis Berries Extracts Obtained from Ultrasound-Assisted and Supercritical Fluid Extraction

by Ilir Mërtiri, Gigi Coman, Mihaela Cotârlet, Mihaela Turturică, Nicoleta Balan, Gabriela Râpeanu, Nicoleta Stănciuc and Liliana Mihalcea

Separations 2025, 12(1), 8; https://doi.org/10.3390/separations12010008 - 3 Jan 2025

Viewed by 563

Abstract

This research paper investigates the phytochemical profile, antioxidant activity, antidiabetic potential, and antibacterial activity of Myrtus communis berries. Two extraction methods were employed to obtain the extracts: solid–liquid ultrasound-assisted extraction (UAE) and supercritical fluid extraction (SFE). The extracts were characterized using spectrophotometric methods [...] Read more.

This research paper investigates the phytochemical profile, antioxidant activity, antidiabetic potential, and antibacterial activity of Myrtus communis berries. Two extraction methods were employed to obtain the extracts: solid–liquid ultrasound-assisted extraction (UAE) and supercritical fluid extraction (SFE). The extracts were characterized using spectrophotometric methods and Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC). The UAE extract exhibited higher total flavonoid and anthocyanin content, while the SFE extract prevailed in total phenolic content and antioxidant activity in the DPPH radical screening assay. RP-HPLC characterization identified and quantified several polyphenolic compounds. In the UAE extract, epigallocatechin was found in a concentration of 2656.24 ± 28.15 µg/g dry weight (DW). In the SFE extract, cafestol was the identified compound with the highest content at a level of 29.65 ± 0.03 µg/g DW. Both extracts contained several anthocyanin compounds, including cyanidin 3-O-glucoside chloride, cyanidin-3-O-rutinoside chloride, malvidin-3-O-glucoside chloride, pelargonidin 3-O-glucoside chloride, peonidin 3-O-glucoside chloride, and peonidin-3-O-rutinoside chloride. The antidiabetic potential was evaluated in vitro by measuring the inhibition of α-amylase from porcine pancreas (type I-A). The results highlighted the ability of myrtle berry extracts to inhibit α-amylase enzymatic activity, suggesting its potential as an alternative for controlling postprandial hyperglycemia. The UAE extract showed the lowest IC50 value among the two extracts, with an average of 8.37 ± 0.52 µg/mL DW. The antibacterial activity of the extracts was assessed in vitro against Bacillus spp., Escherichia coli, and Staphylococcus aureus using the disk diffusion method. Both myrtle berry extracts exhibited similar antibacterial activity against the tested bacterial strains. The results support further investigation of myrtle berries extracts as a potential ingredient in functional food formulation, particularly due to its antioxidant, antidiabetic, and antibacterial properties. Full article

(This article belongs to the Special Issue Green Extraction Techniques of Bioactive Compounds from Natural Sources)

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17 pages, 5169 KiB

Open AccessArticle

Research on the Flotation Mechanism of Microemulsion Collector Enhanced Removal of Dyeing Impurities from Phosphogypsum

by Xiaosheng Yu, Lijun Deng, Changpan Shen, Huiyong Li, Jingchao Li, Yijun Cao, Guoli Zhou and Guosheng Li

Separations 2025, 12(1), 7; https://doi.org/10.3390/separations12010007 - 31 Dec 2024

Viewed by 380

Abstract

Phosphogypsum is an industrial byproduct that is limited in its high-value application due to the presence of dyeing impurities (such as organic matter and carbon black). The flotation method has been verified to be effective in separating these dyeing impurities from gypsum. In [...] Read more.

Phosphogypsum is an industrial byproduct that is limited in its high-value application due to the presence of dyeing impurities (such as organic matter and carbon black). The flotation method has been verified to be effective in separating these dyeing impurities from gypsum. In this study, microemulsion was used as the collector method of dyeing impurities for their separation from gypsum. The results of flotation tests showed that the microemulsion collector exhibited excellent collection capability and selectivity under natural pH conditions (pH = 1.5). With a microemulsion collector consumption of 400 g/t, purified gypsum of 65.1% whiteness, 95.74% yield, and 97.01% recovery was obtained. The purified gypsum of 65.1% whiteness, 95.74% yield, 97.01 recovery obtained by a used microemulsion collector amount of 400 g/t was better than using the same dosage of kerosene collector. The dispersion behavior of the microemulsion collector was studied by low-temperature transmission electron microscopy. The microemulsion collector demonstrated superior dispersibility, as it forms nano-oil droplets with an average size of 176.83 nm in the pulp, resolving issues associated with poor dispersibility observed in traditional kerosene collectors. Additionally, the nano-oil droplets effectively adsorbed onto the surface of dyeing impurities through hydrogen bonding, enhancing their hydrophobicity. Therefore, the microemulsion collector holds great potential for application in flotation whitening processes involving phosphogypsum. Full article

(This article belongs to the Special Issue Separation and Extraction Technology in Mineral Processing)

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15 pages, 2061 KiB

Open AccessArticle

Kinetics of Supercritical CO₂ Extraction from Burrito (Aloysia polystachya) Leaves and Sucupira-Preta (Bowdichia virgilioides) Seeds

by Gabrielle Vaz Vieira, Michel Rubens dos Reis Souza, Carlos Toshiyuki Hiranobe, José Eduardo Goncalves, Cristiane Mengue Feniman Moritz, Otávio Akira Sakai, Leila Maria Sotocorno e Silva, Michael Jones da Silva, Erivaldo Antônio da Silva, Renivaldo José dos Santos, Edson Antônio da Silva, Lucio Cardozo-Filho and Leandro Ferreira-Pinto

Separations 2025, 12(1), 6; https://doi.org/10.3390/separations12010006 - 31 Dec 2024

Viewed by 489

Abstract

This study investigated the application of supercritical carbon dioxide (CO₂) for the extraction of essential oils from plant materials with anxiolytic potential, focusing on the leaves of burrito (Aloysia polystachya) and the seeds of sucupira-preta (Bowdichia virgilioides). [...] Read more.

This study investigated the application of supercritical carbon dioxide (CO₂) for the extraction of essential oils from plant materials with anxiolytic potential, focusing on the leaves of burrito (Aloysia polystachya) and the seeds of sucupira-preta (Bowdichia virgilioides). The supercritical extraction technique was chosen for its ability to produce high-purity extracts without residual solvents and to reduce the environmental impact. This study evaluated the influence of temperature (40 °C, 50 °C, and 60 °C) and pressure (22 MPa, 25 MPa, and 28 MPa) on extraction efficiency using a 2² factorial design with triplicates at the central point. The maximum yields were 1.2% for burrito leaves and 4.2% for sucupira-preta seeds. Despite their relatively low yields, the extracts contained a diverse range of chemical compounds, including fatty acids (oleic, linoleic, and palmitic acids), squalene, β-carotene, vitamin E, and other bioactive molecules with antioxidant, anti-inflammatory, and immunomodulatory properties. Statistical analysis demonstrated that pressure was the most influential factor affecting yield, whereas temperature played a secondary role. The Sovová kinetic model provided a good fit for the extraction curves, with determination coefficients (R²) above 0.95, thus validating the efficiency of the method. These results highlight the pharmaceutical potential of these extracts, particularly for therapeutic and anxiolytic purposes. Full article

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17 pages, 5353 KiB

Open AccessArticle

A Compact Instrument for Temperature-Programming-Assisted Capillary–Nanoliquid Chromatography

by Lincon Coutinho Marins, Alessandra Maffei Monteiro, Vivane Lopes Leal, Deyber Arley Vargas Medina, Edwin Martin Cardenas and Fernando Mauro Lanças

Separations 2025, 12(1), 5; https://doi.org/10.3390/separations12010005 - 30 Dec 2024

Viewed by 488

Abstract

The miniaturization of liquid chromatography (LC) columns to capillary and nanoscales allows temperature programming to be an effective alternative to solvent gradients for modulating eluotropic strength. This approach simplifies instrument design and operation, as a single pump can suffice to achieve efficient separations. [...] Read more.

The miniaturization of liquid chromatography (LC) columns to capillary and nanoscales allows temperature programming to be an effective alternative to solvent gradients for modulating eluotropic strength. This approach simplifies instrument design and operation, as a single pump can suffice to achieve efficient separations. This study presents the development and application of a compact, lab-built high-pressure system for temperature-programmed capillary and nanoLC separations. The instrument includes a high-pressure capillary–nanoflow syringe pump, a time-based nanoliter injection system, a programmable capillary column oven for controlled temperature gradients, and a UV-Vis detection system with a custom nanoliter-scale detection cell. Each system component was designed and built in-house, with rigorous calibration to ensure accuracy and operational reliability. Experimental data confirm the system’s capability to deliver precise, reproducible temperature, and flow rates. Functionality was validated through temperature-programmed separations on packed and open tubular capillary columns. The results demonstrated that the developed instrument offers enhanced separation efficiency and reduced analysis time compared to isothermal methods, underscoring its potential for advanced applications in miniaturized liquid chromatography. Full article

(This article belongs to the Special Issue Separation Techniques on a Miniaturized Scale)

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22 pages, 2361 KiB

Open AccessReview

Advances in Recycling Technologies of Critical Metals and Resources from Cathodes and Anodes in Spent Lithium-Ion Batteries

by Shuwen Wang, Yanrong Lai, Jingran Yang, Jiaxue Zhao, Yushan Zhang, Miaoling Chen, Jinfeng Tang, Junhua Xu and Minhua Su

Separations 2025, 12(1), 4; https://doi.org/10.3390/separations12010004 - 30 Dec 2024

Viewed by 584

Abstract

With the rapid economic development and the continuous growth in the demand for new energy vehicles and energy storage systems, a significant number of waste lithium-ion batteries are expected to enter the market in the future. Effectively managing the processing and recycling of [...] Read more.

With the rapid economic development and the continuous growth in the demand for new energy vehicles and energy storage systems, a significant number of waste lithium-ion batteries are expected to enter the market in the future. Effectively managing the processing and recycling of these batteries to minimize environmental pollution is a major challenge currently facing the lithium-ion battery industry. This paper analyzes and compares the recycling strategies for different components of lithium-ion batteries, providing a summary of the main types of batteries, existing technologies at various pre-treatment stages, and recycling techniques for valuable resources such as heavy metals and graphite. Currently, pyrometallurgy and hydrometallurgy processes have matured; however, their high energy consumption and pollution levels conflict with the principles of the current green economy. As a result, innovative technologies have emerged, aiming to reduce energy consumption while achieving high recovery rates and minimizing the environmental impact. Nevertheless, most of these technologies are currently limited to the laboratory scale and are not yet suitable for large-scale application. Full article

(This article belongs to the Section Purification Technology)

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12 pages, 1644 KiB

Open AccessArticle

CO₂/CH₄ and CO₂/CO Selective Pebax-1657 Based Composite Hollow Fiber Membranes Prepared by a Novel Dip-Coating Technique

by Dionysios S. Karousos, George V. Theodorakopoulos, Francesco Chiesa, Stéphan Barbe, Mirtat Bouroushian and Evangelos P. Favvas

Separations 2025, 12(1), 3; https://doi.org/10.3390/separations12010003 - 29 Dec 2024

Viewed by 560

Abstract

A novel and innovative method was developed to fabricate defect-free composite hollow fiber (HF) membranes using drop-casting under continuous flow. The synthesized Pebax-1657—based membranes were examined for gas separation processes, focusing on the separation of CO₂ from CH₄ and CO gases. [...] Read more.

A novel and innovative method was developed to fabricate defect-free composite hollow fiber (HF) membranes using drop-casting under continuous flow. The synthesized Pebax-1657—based membranes were examined for gas separation processes, focusing on the separation of CO₂ from CH₄ and CO gases. The separation performance of the membranes was rigorously assessed under realistic binary gas mixture conditions to evaluate their selectivity and performance. The effect of pressure on separation performance was systematically investigated, with transmembrane pressures up to 10 bar being applied at a temperature of 298 K. Remarkable CO₂/CH₄ selectivities of up to 110 and CO₂/CO selectivities of up to 48 were achieved, demonstrating the robustness and effectiveness of these composite HF membranes, suggesting their suitability for high-performance gas separation processes under varying operational conditions. Overall, this study introduces a novel approach for scaling up the fabrication of HF membranes and provides valuable insights into their application in CO₂ separation technologies, offering the potential for advancements in areas such as natural gas processing and carbon capture from CO-containing streams. Full article

(This article belongs to the Special Issue 10th Anniversary Special Issues: Membrane Separation Processes)

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21 pages, 5817 KiB

Open AccessArticle

Application of Magnetic Aquatic Plant Biochar for Efficient Removal of Antimony from Water: Adsorption Properties and Mechanism

by Luyi Nan, Yuting Zhang, Min Liu, Liangyuan Zhao, Yuxuan Zhu and Xun Zhang

Separations 2025, 12(1), 2; https://doi.org/10.3390/separations12010002 - 28 Dec 2024

Viewed by 612

Abstract

Antimony (Sb) pollution in natural water bodies can cause significant harm to aquatic ecosystems. Currently, the utilization of chemicals in water bodies presents disadvantages, such as the hardship in collecting dispersed flocs and the incomplete elimination of pollutants. In the present research, a [...] Read more.

Antimony (Sb) pollution in natural water bodies can cause significant harm to aquatic ecosystems. Currently, the utilization of chemicals in water bodies presents disadvantages, such as the hardship in collecting dispersed flocs and the incomplete elimination of pollutants. In the present research, a novel type of efficient adsorbent material for the magnetic recovery of Sb was proposed: the magnetic aquatic plant biochar. Its adsorption characteristics and mechanism were deeply investigated. The results demonstrated that, among the three types of aquatic plants, the magnetic biochar of Arundo donax magnetic biochar (LMBC) displayed the most superior adsorption effect on Sb. Under optimal adsorption conditions (pyrolysis temperature of 300 °C, dosage of 100 mg, pH of 8), the removal rate of Sb by LMBC exceeded 97%. The adsorption rate of Sb by LMBC was relatively rapid, and the kinetics of adsorption conformed to a pseudo-second-order kinetic model. The adsorption isotherm was consistent with the Langmuir and Freundlich models, and the maximum adsorption capacity of Sb reached 26.07 mg/g, suggesting that the adsorption process pertained to the adsorption of multi-molecular layers. The influence of coexisting ions on the adsorption effect of LMBC was insignificant. The SEM characterization results revealed that LMBC mainly consisted of the elements C and O. The BET characterization results demonstrated that the magnetization modification augmented the specific surface area by approximately 30 times to reach 89.14 m²/g, and the pore volume increased by twofold to 0.18 cm³/g, creating a favorable condition for Sb adsorption. The FTIR, XRD, and XPS results indicated that the surface of LMBC was rich in carboxyl and hydroxyl groups and was successfully loaded with Fe₂O₃ and Fe₃O₄. LMBC not only facilitates the resourceful utilization of aquatic plant waste but also effectively removes antimony (Sb) pollution through its magnetic properties. This dual functionality presents promising application prospects for the efficient adsorption and removal of Sb from water. Full article

(This article belongs to the Special Issue Adsorption of Emerging Water Pollutants by Advanced Materials)

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18 pages, 8445 KiB

Open AccessArticle

Irradiated Gao Miao Zi Bentonite for Uranium Retention: Performance and Mechanism

by Yushan Zhang, Gang Song, Yujie Mo, Shuwen Wang, Diyun Chen and Minhua Su

Separations 2025, 12(1), 1; https://doi.org/10.3390/separations12010001 - 26 Dec 2024

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Abstract

Bentonite has been considered as backfill material in the long-term deep geological disposal sites for radioactive waste. The performance of raw and irradiated bentonite based on the retention of radioactive nuclides, such as U(VI), is a critical factor for its application. Herein, the [...] Read more.

Bentonite has been considered as backfill material in the long-term deep geological disposal sites for radioactive waste. The performance of raw and irradiated bentonite based on the retention of radioactive nuclides, such as U(VI), is a critical factor for its application. Herein, the intrinsic features and adsorption behavior of Gao Miao Zi (GMZ) bentonite based on uranyl ions was investigated. In aqueous solutions, bentonite can achieve an adsorption rate of up to 100% for U(VI). The primary mechanism of U(VI) adsorption by GMZ bentonite is ion exchange, supplemented by surface complexation. Strong irradiation can introduce slight structural changes and framework fractures in bentonite, reducing its adsorption capacity for U(VI). This study provides an in-depth analysis of the adverse effects of high doses of radiation (100 kGy) on the microstructure and adsorption properties of bentonite, offering important insights for the safe storage of radioactive waste. Full article

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

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Separations, Volume 12, Issue 1 (January 2025) – 17 articles

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