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Volume 12
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Separations, Volume 12, Issue 1 (January 2025) – 8 articles

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17 pages, 2691 KiB  
Article
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 279
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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<p>Chromatograms of wild myrtle berries extracts. UAE extract: (<b>a</b>) 280 nm; 2—gallic acid; 5—epicatechin; 8—ferulic acid; 10—synapic acid; 1, 3, 4, 6, 7, 9, 11–17—unidentified compounds. (<b>b</b>) 520 nm; 2—gallic acid; 7—kuromanin chloride; 8—synapic acid; 10—naringin; 11—rutin trihydrate; 12—peonidin-3-<span class="html-italic">O</span>-rutinoside chloride; 15—quercetin; 1, 3–6, 9, 13, 14, 16—unidentified compounds. SFE extract: (<b>c</b>) 280 nm; 1—cafestol; 2—gallic acid; 7—ferulic acid; 16—quercetin; 3–6, 8–15—unidentified compounds. (<b>d</b>) 520 nm; 4—kuromanin chloride; 5—callistephin chloride; 9—oenin chloride; 1–3, 6–8, 10–17—unidentified compounds. (<b>e</b>) 450 nm: 8—zeaxanthin; 1–7, 9–11—unidentified compounds.</p> Full article ">Figure 2
<p>Antibacterial results of disk diffusion method against the tested bacterial strains. The samples codes represent the following: UAE—myrtle berries extract from ultrasound-assisted extraction; SFE—myrtle berries extract extract from supercritical fluid extraction; CC1—ciprofloxacin (positive control); CS—solubilization solvent (negative control).</p> Full article ">
17 pages, 5169 KiB  
Article
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 210
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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<p>SEM images of PG sample ((<b>a</b>) the microstructure of and (<b>b</b>) the elements mapping scanning of the PG raw ore.)</p> Full article ">Figure 2
<p>XRD pattern of the PG sample.</p> Full article ">Figure 3
<p>Flow chart of microemulsion preparation (<b>a</b>) and the reverse flotation tests (<b>b</b>).</p> Full article ">Figure 3 Cont.
<p>Flow chart of microemulsion preparation (<b>a</b>) and the reverse flotation tests (<b>b</b>).</p> Full article ">Figure 4
<p>TG-DTG pattern of the dyeing impurities.</p> Full article ">Figure 5
<p>Size distribution of oil droplets generated by the dispersion of the microemulsion (<b>a</b>) and kerosene (<b>b</b>).</p> Full article ">Figure 6
<p>Morphology of the microemulsion (<b>a</b>) and nano-oil droplets (<b>b</b>).</p> Full article ">Figure 7
<p>Flotation results at different dosages of kerosene (<b>a</b>) and microemulsion (<b>b</b>) collectors.</p> Full article ">Figure 8
<p>SEM images of raw PG (<b>a</b>) and gypsum concentrate (<b>b</b>).</p> Full article ">Figure 9
<p>Contact angles of gypsum (<b>a</b>) and dyeing impurities (<b>b</b>) before and after being treated with kerosene and microemulsion.</p> Full article ">Figure 10
<p>FT-IR results of gypsum and dyeing impurities treated by different collectors.</p> Full article ">Figure 11
<p>XPS results of dyeing impurities treated by different collectors.</p> Full article ">Figure 12
<p>Schematic diagram of the microemulsion collector enhancing flotation performance of PG.</p> Full article ">
15 pages, 2061 KiB  
Article
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 309
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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<p>A schematic of the experimental supercritical extraction unit: 1—CO<sub>2</sub> cylinder; 2—syringe pump; 3—thermostatic bath; 4—pressure indicator; 5—temperature controller/indicator; 6—extractor; 7—valve; 8—needle-type valve attached to an aluminum jacket for heating; 9—thermostatic bath; 10—aluminum structure.</p> Full article ">Figure 2
<p>Experimental kinetic extraction curves with supercritical CO<sub>2</sub> fitted using the Sovová model (<span class="html-fig-inline" id="separations-12-00006-i001"><img alt="Separations 12 00006 i001" src="/separations/separations-12-00006/article_deploy/html/images/separations-12-00006-i001.png"/></span>) of burrito leaves: 40 °C (■, 22 MPa; ▲, 28 MPa); 50 °C (<span class="html-fig-inline" id="separations-12-00006-i002"><img alt="Separations 12 00006 i002" src="/separations/separations-12-00006/article_deploy/html/images/separations-12-00006-i002.png"/></span>, 25 MPa); 60 °C (●, 22 MPa; ▼, 28 MPa) with a constant flow rate of 2.0 mL min<sup>−1</sup>.</p> Full article ">Figure 3
<p>Experimental kinetic extraction curves with supercritical CO<sub>2</sub> fitted using Sovová model (<span class="html-fig-inline" id="separations-12-00006-i001"><img alt="Separations 12 00006 i001" src="/separations/separations-12-00006/article_deploy/html/images/separations-12-00006-i001.png"/></span>) of sucupira-preta seeds: 40 °C (■, 22 MPa; ▲, 28 MPa); 50 °C (<span class="html-fig-inline" id="separations-12-00006-i002"><img alt="Separations 12 00006 i002" src="/separations/separations-12-00006/article_deploy/html/images/separations-12-00006-i002.png"/></span>, 25 MPa); 60 °C (●, 22 MPa; ▼, 28 MPa) with a constant flow rate of 2.0 mL min<sup>−1</sup>.</p> Full article ">Figure 4
<p>A response surface plot illustrating the extraction yield of oil from burrito leaves as a function of temperature and pressure, with a constant flow rate of 2.0 mL min<sup>−1</sup>.</p> Full article ">Figure 5
<p>A response surface plot showing the oil extraction yield from sucupira-preta seeds as influenced by temperature and pressure at a fixed flow rate of 2.0 mL min<sup>−1</sup>.</p> Full article ">Figure 6
<p>Pareto chart: analysis of linear effects of variables. (<b>A</b>) Burrito leaves and (<b>B</b>) sucupira-preta seeds.</p> Full article ">
17 pages, 5353 KiB  
Article
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 292
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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<p>Illustration of the mechanical architecture of the developed capillary–nanoflow high-pressure syringe pump, highlighting its main actuation components.</p> Full article ">Figure 2
<p>Photographs of the developed capillary–NanoLC temperature-programmable oven: (<b>a</b>) metal body of the oven; (<b>b</b>) Fiberfrax<sup>®</sup> thermal insulation fabric; (<b>c</b>) ceramic tube wrapped with resistive nickel–chromium heating wire; (<b>d</b>) cooling fan; (<b>e</b>) Celeron cooling duct; (<b>f</b>) servomotor controlling the cooling windows; (<b>g</b>) cooling windows; (<b>h</b>) fully assembled oven.</p> Full article ">Figure 3
<p>The assembly process of the capillary–NanoLC detection cell: (<b>a</b>) anodized aluminum blocks used for supporting the optical path length; (<b>b</b>) bending process of the capillary tube to form the optical path; (<b>c</b>) optical path length featuring 7.9 mm; (<b>d</b>) fully assembled detection cell, including the central metallic tube supporting the optical path length.</p> Full article ">Figure 4
<p>Measure vs. set flow rate: (<b>a</b>) in the 0–250 µL/min range; (<b>b</b>) in the 0–10 µL/min range; (<b>c</b>) in the 0–1.0 µL/min range.</p> Full article ">Figure 5
<p>Calibration of the injection volume: (<b>A</b>) a representative chromatogram of the mixture is used for calibration. The analysis used a fused silica capillary column (250 μm i.d., 15 cm length) packed with 3.0 μm C18 Pinnacle II (Restek) stationary phase. The mobile phase consisted of acetonitrile/water (48:62) acidified with 0.5% glacial acetic acid, delivered at a flow rate of 3 μL/min. Peak areas were calculated from chromatograms recorded at 240 nm; (<b>B</b>) relationship between the injection time and the injected volume, showing linearity in the 0–300 ms range and an exponential decrease in volume per unit time beyond this point; (<b>C</b>) correlation between the adjusted injection volume and the experimentally measured volume after calibration, demonstrating the accuracy of the system post-calibration.</p> Full article ">Figure 6
<p>Performance assessment of the developed temperature-programmable oven: (<b>a</b>) example of temperature control during an isothermal run at 60 °C; (<b>b</b>) correspondence between the temperature set by the user and the experimentally measured temperature; (<b>c</b>) relationship between the heating power required and the temperature ramp slope (°C/min); (<b>d</b>) an example of the oven’s operation during a run includes both isothermal and temperature gradient segments.</p> Full article ">Figure 7
<p>Chromatograms obtained using both the commercial microcell (Shimadzu) and the capillary cell developed in this work. The analysis was performed using a lab-made C-18 250 µm i.d ×150 mm packed column and a flow rate of 3.0 μL/min, with an injection volume of 60 nL. The elution order of the analytes was as follows: (1) naphthalene, (2) phenanthrene, and (3) anthracene. The concentration of each analyte was 30 mg/L.</p> Full article ">Figure 8
<p>Graphs showing variation as a function of the squared retention volume for the (<b>a</b>) lab-made and (<b>b</b>) commercial instruments.</p> Full article ">Figure 9
<p>Separation of PAHs (50 mg/mL) on a packed C18 capillary column (14 cm length, 250 µm i.d., 3.5 µm particle size) at a flow rate of 5.0 µL/min, using acetonitrile (70:30) as the mobile phase, under two conditions: (<b>a</b>) isothermal mode (no temperature programming) and (<b>b</b>) with temperature programming. Analytes: naphthalene (1), acenaphthylene (2), acenaphthene (3), fluorene (4), phenanthrene (5), anthracene (6), chrysene (7), and dibenzo(a,h)anthracene (8).</p> Full article ">Figure 10
<p>Separating alkylbenzene compounds using a WCOT column (5 m length, 50 μm i.d.): (<b>a</b>) without temperature programming and (<b>b</b>) with temperature programming. Peaks: uracil (1), Toluene (2), ethylbenzene (3), butylbenzene (4), pentylbenzene (5), and heptylbenzene (6).</p> Full article ">Figure 11
<p>Separating alkylbenzene compounds using a PLOT column (5 m length, 50 μm i.d.): (<b>a</b>) without temperature programming and (<b>b</b>) with temperature programming. Peaks: uracil (1), toluene (2), ethylbenzene (3), butylbenzene (4), pentylbenzene (5), and heptylbenzene (6).</p> Full article ">
22 pages, 2361 KiB  
Review
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 304
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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<p>(<b>a</b>) Applications of lithium-ion batteries; (<b>b</b>) The shape and components of some Li-ion battery configurations; (<b>c</b>) Flow-chart showing the typical recycling process; (<b>d</b>) Schematic diagram of the LIB working principle.</p> Full article ">Figure 2
<p>Schematic diagrams of pyrometallurgy, hydrometallurgy, and direct recovery processes [<a href="#B48-separations-12-00004" class="html-bibr">48</a>].</p> Full article ">Figure 3
<p>Characteristics of different pyrometallurgical technologies used to treat spent LIBs for the recovery of strategic metals.</p> Full article ">
12 pages, 1644 KiB  
Article
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 304
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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<p>Upscaled, according to a previous work [<a href="#B24-separations-12-00003" class="html-bibr">24</a>], HF coating device for underflow drop-casting.</p> Full article ">Figure 2
<p>SEM micrographs of the composite HF membrane: (<b>a</b>) cross-sectional view showing overall morphology; higher magnification images illustrating (<b>b</b>) the gutter layer; (<b>c</b>) the wall region with a sponge-like structure region; and (<b>d</b>) the separation layer thickness.</p> Full article ">Figure 3
<p>Separation factor (selectivity) and CO<sub>2</sub> permeance (GPU) as a function of pressure drop across the composite HF membrane for a gas mixture containing 10% <span class="html-italic">v</span>/<span class="html-italic">v</span> CO<sub>2</sub> in CH<sub>4</sub>. The temperature was maintained at 298 K.</p> Full article ">Figure 4
<p>Separation factor (selectivity) and CO<sub>2</sub> permeance (GPU) as a function of pressure drop across the composite HF membrane for a gas mixture containing 33% <span class="html-italic">v</span>/<span class="html-italic">v</span> CO<sub>2</sub> in CO. The temperature was maintained at 298 K.</p> Full article ">
21 pages, 5817 KiB  
Article
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 455
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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<p>The preparation process of the biochars and magnetic biochars.</p> Full article ">Figure 2
<p>Adsorption and desorption isothermal curves of LBC (<b>a</b>) and LMBC (<b>b</b>).</p> Full article ">Figure 3
<p>Scanning electron micrographs of LBC and LMBC before and after adsorption. (<b>a</b>) LBC-before adsorption; (<b>b</b>) LBC-after adsorption; (<b>c</b>) LMBC-before adsorption; (<b>d</b>) LMBC-after adsorption.</p> Full article ">Figure 4
<p>C, N, O, and Fe energy spectrum fluorescence of LBC and LMBC.</p> Full article ">Figure 5
<p>The FTlR results of LBC and LMBC before and after absorption.</p> Full article ">Figure 6
<p>XRD pattern of LBC and LMBC before and after adsorption.</p> Full article ">Figure 7
<p>XPS spectra of LMBC before and after adsorption. (<b>a</b>) Full spectrum; (<b>b</b>) C1s fine spectrum; (<b>c</b>) O1s fine spectrum; (<b>d</b>) Fe2p fine spectrum; and (<b>e</b>) Sb3d fine spectrum.</p> Full article ">Figure 7 Cont.
<p>XPS spectra of LMBC before and after adsorption. (<b>a</b>) Full spectrum; (<b>b</b>) C1s fine spectrum; (<b>c</b>) O1s fine spectrum; (<b>d</b>) Fe2p fine spectrum; and (<b>e</b>) Sb3d fine spectrum.</p> Full article ">Figure 8
<p>Magnetization curve of LMBC.</p> Full article ">Figure 9
<p>(<b>a</b>) Effect of biochar and magnetic biochar prepared by different aquatic plant species; (<b>b</b>) effect of biochar and magnetic biochar dosage; (<b>c</b>) effect of initial pH; and (<b>d</b>) effect of ionic strength. “****”: the number of asterisks denotes the level of statistical significance, with four asterisks indicating a <span class="html-italic">p</span>-value of less than 0.0001, signifying a highly significant difference between LBC and LMBC.</p> Full article ">Figure 10
<p>(<b>a</b>) Adsorption kinetics of LBC; (<b>b</b>) adsorption kinetics of LMBC; (<b>c</b>,<b>d</b>) adsorption isotherm of LBC; and (<b>e</b>,<b>f</b>) adsorption isotherm of LMBC (experimental conditions: 150 mL of 5 mg/L Sb solution with 100 mg LMBC at the initial pH of 8).</p> Full article ">Figure 11
<p>Schematic diagram of the mechanism of Sb adsorption and removal by LMBC.</p> Full article ">
18 pages, 8445 KiB  
Article
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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Full article ">Figure 1
<p>SEM images of (<b>a</b>) natural GMZ bentonite, (<b>b</b>) electron-beam-irradiated bentonite, and (<b>c</b>) gamma-irradiated bentonite, as well as (<b>d</b>) TEM image of natural GMZ bentonite and (<b>e</b>) TEM high-resolution image.</p> Full article ">Figure 2
<p>(<b>a</b>) The SEM elemental mapping images, (<b>b</b>) elemental composition, and (<b>c</b>) elemental content of the GMZ bentonite.</p> Full article ">Figure 3
<p>(<b>a</b>) XRD pattern, (<b>b</b>) FT-IR spectra, (<b>c</b>) N<sub>2</sub> adsorption-desorption isotherm, and (<b>d</b>) pore size distribution curve of GMZ bentonite before and after irradiation.</p> Full article ">Figure 4
<p>(<b>a</b>) Effect of the contact time and dosing amount on the uranium adsorption rate based on the adsorption of GMZ bentonite (uranium initial = 20 mg/L, pH = 5, T = room temperature); (<b>b</b>) effect of the initial uranium concentration on the absorption rate and adsorption capacity based on the adsorption of GMZ bentonite (dosage = 6 g/L, pH = 5, t = 30 min, and T = room temperature).</p> Full article ">Figure 5
<p>Effect of (<b>a</b>) pH (uranium initial = 20 mg/L, T = room temperature, m/V = 6 g/L); (<b>b</b>) ionic strength (uranium initial = 20 mg/L, T = room temperature, m/V = 6 g/L); (<b>c</b>) HA concentration (uranium initial = 20 mg/L, T = room temperature, m/V = 6 g/L, I = 0.1 M NaCl); (<b>d</b>) zeta potentials of bentonite as a function of pH (uranium initial = 20 mg/L, T = room temperature, m/V = 6 g/L).</p> Full article ">Figure 6
<p>(<b>a</b>) Kinetic model; (<b>b</b>) particle diffusion model; (<b>c</b>) isothermal model of GMZ bentonite for the adsorption of uranium.</p> Full article ">Figure 7
<p>(<b>a</b>) TEM, (<b>b</b>) TEM-EDS, (<b>c</b>) XRD, (<b>d</b>) FT-IR, and (<b>e</b>) XPS full-survey spectra, as well as the (<b>f</b>) U 4f XPS spectra of the GMZ bentonite before and after the absorption of U(VI).</p> Full article ">Figure 8
<p>The possible mechanism of uranium adsorption by GMZ bentonite.</p> Full article ">
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