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Separations
Volume 12
Issue 8
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Separations, Volume 12, Issue 8 (August 2025) – 36 articles

Cover Story (view full-size image): Extra virgin olive oil production generates a large quantity of phenolic-rich waste biomass in the form of olive leaves. Olive leaf extracts exhibit powerful antioxidant properties, making them a promising resource for the food industry. Despite their long history in traditional medicine, olive leaves’ potential remains untapped, partly because the content of phenolic compounds is influenced by many factors. This study investigates how the concentration of bioactive phenols in olive leaves varies according to cultivar, harvesting year, and the plant's phenological phase. In total, 25 phenolic derivatives were analyzed using HPLC-DAD-MS; the resulting data were processed with 3-way ANOVA, Genetic Algorithm with Linear Discriminant Analysis, and Random Forest, highlighting correlations between phenolic compounds and different sources of variability. View this paper
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19 pages, 4673 KiB  
Article
Effect of Iron–Carbon–Zeolite Substrate Configuration on Cadmium Removal in Vertical-Flow Constructed Wetlands
by Mengyi Li, Shiyu Chen, Jundan Chen, Naifu Zhou and Guanlong Yu
Separations 2025, 12(8), 223; https://doi.org/10.3390/separations12080223 - 21 Aug 2025
Abstract
The excessive emission of cadmium (Cd2+) poses a serious threat to the aquatic environment due to its high toxicity and bioaccumulation potential. This study constructed three types of vertical-subsurface-flow constructed wetlands configured with iron–carbon–zeolite composite substrates, including an iron–carbon–zeolite constructed wetland [...] Read more.
The excessive emission of cadmium (Cd2+) poses a serious threat to the aquatic environment due to its high toxicity and bioaccumulation potential. This study constructed three types of vertical-subsurface-flow constructed wetlands configured with iron–carbon–zeolite composite substrates, including an iron–carbon–zeolite constructed wetland (TF-CW), a zeolite–iron–carbon constructed wetland (FT-CW), and an iron–carbon–zeolite mixed constructed wetland (H-CW), to investigate the purification performance and mechanisms of constructed wetlands for cadmium-containing wastewater (0~6 mg/L). The results demonstrated that iron–carbon–zeolite composite substrates significantly enhanced Cd2+ removal efficiency (>99%) through synergistic redox-adsorption mechanisms, where the iron–carbon substrate layer dominated Fe-Cd co-precipitation, while the zeolite layer achieved short-term cadmium retention through ion-exchange adsorption. FT-CW exhibited superior NH4+-N removal efficiency (77.66%~92.23%) compared with TF-CW (71.45%~88.05%), while iron–carbon micro-electrolysis effectively inhibited NO3−-N accumulation (<0.1 mg/L). Under cadmium stress, Typha primarily accumulated cadmium through its root systems (>85%) and alleviated oxidative damage by dynamically regulating antioxidative enzyme activity, with the superoxide dismutase (SOD) peak occurring at 3 mg/L Cd2+ treatment. Microbial community analysis revealed that iron–carbon substrates promoted the relative abundance of Bacteroidota and Patescibacteria as well as the enrichment of Saccharimonadales, Thauera, and Rhodocyclaceae (genera), enhancing system stability. This study confirms that iron–carbon–zeolite CWs provide an efficient and sustainable technological pathway for heavy metal-contaminated water remediation through multidimensional mechanisms of “chemical immobilization–plant enrichment–microbial metabolism”. Full article
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15 pages, 4104 KiB  
Article
Enhanced Degradation of Different Tetracyclines by Nonthermal Plasma and Activated Persulfate: Insights into Synergistic Effects and Degradation Mechanism
by Amina Ouzar, Bimo Tri Goutomo, Kyung-Min Lee and Il-Kyu Kim
Separations 2025, 12(8), 222; https://doi.org/10.3390/separations12080222 - 19 Aug 2025
Viewed by 106
Abstract
The increasing presence of tetracycline antibiotics (TCs) in water sources poses significant environmental and public health risks, necessitating effective treatment technologies. This study investigates the degradation of three types of TCs in water—Tetracycline (TC), Oxytetracycline (OTC), and Chlortetracycline (CTC)—using nonthermal plasma (NTP) coupled [...] Read more.
The increasing presence of tetracycline antibiotics (TCs) in water sources poses significant environmental and public health risks, necessitating effective treatment technologies. This study investigates the degradation of three types of TCs in water—Tetracycline (TC), Oxytetracycline (OTC), and Chlortetracycline (CTC)—using nonthermal plasma (NTP) coupled with the persulfate (PS) process. The combined NTP/PS system was optimized for various operational parameters, including PS concentration, pH, and reaction time, to achieve maximum degradation and mineralization efficiency. The results showed that the NTP/PS system achieved over 90% degradation of all TCs under optimal conditions, outperforming plasma alone treatment. The degradation kinetics followed a pseudo-first-order model, indicating a rapid initial breakdown of TCs. The degradation mechanism was elucidated through the identification of intermediate byproducts using liquid chromatography-mass spectrometry (LC-MS/MS). Free radicals, such as sulfate (SO4•−) and hydroxyl (•OH) radicals, were identified as the primary reactive species responsible for TCs degradation. This study demonstrates the potential of the NTP/PS system as an efficient and sustainable solution for the removal of antibiotic contaminants from water. Further research on the scalability and application in real wastewater conditions is recommended. Full article
(This article belongs to the Section Environmental Separations)
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12 pages, 543 KiB  
Article
Microwave Extraction of Antioxidant Polysaccharides from Plantago depressa and Their Effects on SOD and GSH-Px in Drosophila melanogaster Model
by Chenqian Sun, Qian Liu, Xiaohua Yang, Lu Li, Yubin Wang, Keran Xu and Huafeng Zhang
Separations 2025, 12(8), 221; https://doi.org/10.3390/separations12080221 - 19 Aug 2025
Viewed by 129
Abstract
A microwave extraction method was developed to isolate antioxidant polysaccharides from Plantago depressa (psyllium), and the structure, free radical-scavenging ability, as well as in vivo antioxidant activity of psyllium polysaccharides were analyzed. The optimal condition for microwave extraction was as follows: duration of [...] Read more.
A microwave extraction method was developed to isolate antioxidant polysaccharides from Plantago depressa (psyllium), and the structure, free radical-scavenging ability, as well as in vivo antioxidant activity of psyllium polysaccharides were analyzed. The optimal condition for microwave extraction was as follows: duration of microwave radiation of 35 min, extraction temperature of 80 °C, and ratio of liquid to solid of 80:1 (mL/g). The yield of psyllium polysaccharides by microwave extraction was significantly higher than that by heating extraction (p < 0.05). The volumes of P. depressa samples notably increased after microwave extraction, which implied that microwave radiation might loosen the structure of cells and tissues of psyllium leaves and facilitate the exudation of target polysaccharides from leaf samples. The structure of polysaccharides was analyzed by infrared spectroscopy. The effective concentrations of psyllium polysaccharides scavenging DPPH• and ABTS•+ radicals by 50% (EC50) were 0.20 and 0.10 mg/mL, respectively. Moreover, P. depressa polysaccharides increased activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in Drosophila melanogaster. In conclusion, microwave extraction seems to be an efficient method to isolate bioactive polysaccharides from P. depressa, which were a potential source of natural antioxidants. Full article
(This article belongs to the Special Issue Separation and Purification of Functional Components of Foods and Herbs)
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20 pages, 1270 KiB  
Article
Comparative Carbon Footprint Analysis of Alumina-Based Multichannel and Hollow Fiber Ceramic Membranes for Microfiltration
by Hong Joo Lee, Jang-Hoon Ha, Jongman Lee and In-Hyuck Song
Separations 2025, 12(8), 220; https://doi.org/10.3390/separations12080220 - 18 Aug 2025
Viewed by 183
Abstract
This study aims to compare the carbon footprints associated with the fabrication of two types of alumina-based tubular ceramic membranes used in microfiltration (MF): a multichannel membrane produced by extrusion and dip-coating, and an asymmetric hollow fiber membrane fabricated via phase inversion. The [...] Read more.
This study aims to compare the carbon footprints associated with the fabrication of two types of alumina-based tubular ceramic membranes used in microfiltration (MF): a multichannel membrane produced by extrusion and dip-coating, and an asymmetric hollow fiber membrane fabricated via phase inversion. The multichannel process involves two sintering steps but uses no organic solvents, whereas the phase-inversion method simplifies production through single-step shaping and sintering but requires organic solvents that increase environmental burdens. Using a functional unit of 1 m2 effective membrane area, carbon emissions were quantified from raw material extraction to waste disposal. The results showed total emissions of 8.57 kg CO2-eq/m2 for the multichannel membrane and 10.67 kg CO2-eq/m2 for the hollow fiber membrane. Although the hollow fiber process consumed less energy, its extensive use of solvents, particularly NMP, led to significantly higher emissions. This study provides the first quantitative comparison of these two common ceramic membrane fabrication routes and underscores the importance of considering both energy use and solvent impacts when evaluating the environmental sustainability of membrane production. A sensitivity analysis further evaluated the influence of key parameters, including alumina emission factor, regional electricity carbon intensity, alumina recycling, and solvent substitution or NMP recycling. The analysis demonstrated that each factor could significantly influence the total carbon footprint and, under favorable conditions, narrow or even reverse the gap between the two fabrication routes. This study provides the first quantitative comparison of these two common ceramic membrane fabrication methods and highlights the importance of considering energy use, solvent impacts, and potential mitigation strategies when assessing the environmental sustainability of ceramic membrane production. Full article
(This article belongs to the Special Issue Design and Preparation of Sustainable Separation Membrane for Efficient Water Purification)
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19 pages, 2018 KiB  
Review
Stimulus-Responsive Membranes: A Mini Review on Principles, Preparation Methods, and Emerging Applications
by Yixin Wu, Ziyu Wang, Jian Zhou, Qilin Gu and Zhaoxiang Zhong
Separations 2025, 12(8), 219; https://doi.org/10.3390/separations12080219 - 18 Aug 2025
Viewed by 213
Abstract
Membrane separation technology can be operated in moderate conditions with low energy consumption and has been widely explored and increasingly applied in the water treatment, food, chemical, and pharmaceutical industries. As an upgraded counterpart, stimulus-responsive membranes can respond to external stimuli (such as [...] Read more.
Membrane separation technology can be operated in moderate conditions with low energy consumption and has been widely explored and increasingly applied in the water treatment, food, chemical, and pharmaceutical industries. As an upgraded counterpart, stimulus-responsive membranes can respond to external stimuli (such as light, temperature, pH, electric field, magnetic field, etc.) and actively modulate their own physical and chemical properties, thus showing self-adaptive ability and improved performance. This review provides a comprehensive overview of the recent advancements in the design principles, fabrication methods, and applications of these stimulus-responsive membranes. The challenges and future directions in this field are also prospectively discussed, highlighting the potential for further innovation and industrial applications of stimulus-responsive membranes. Full article
(This article belongs to the Special Issue Design and Preparation of Sustainable Separation Membrane for Efficient Water Purification)
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12 pages, 1561 KiB  
Article
Effect of Performance and Fouling Mechanisms of Thermo-Responsive Membranes on Treating Secondary Effluent Containing Added Sulfamethoxazole
by Lian Yang, Haoran Qiu, Yingjie Yang, Lijun Zhao, Ping Xiao, Guoliang Liu, Jiang Chang, Shaoxia Yang and Feng Xiao
Separations 2025, 12(8), 218; https://doi.org/10.3390/separations12080218 - 16 Aug 2025
Viewed by 137
Abstract
Wastewater treatment plants generally lack a specialized design for the efficient removal of sulfamethoxazole (SMX), a toxic and bio-resistant compound. In this study, secondary effluent from a Beijing wastewater reclamation treatment plant was spiked with SMX and used to investigate the filtration performance [...] Read more.
Wastewater treatment plants generally lack a specialized design for the efficient removal of sulfamethoxazole (SMX), a toxic and bio-resistant compound. In this study, secondary effluent from a Beijing wastewater reclamation treatment plant was spiked with SMX and used to investigate the filtration performance and fouling mechanisms of thermo-responsive membranes. Thermo-responsive materials were prepared using polyvinylidene fluoride, N-isopropylacrylamide (NIPAM), and graphene oxide through Ce (IV)-induced redox radical polymerization. The results showed that the removal of SMX and COD reached 42% and 92%, respectively, with a NIPAM dosage of 1 g, and the removal of UV254 reached its highest value at 57.9%. Additionally, the filtration flux was higher at a temperature of 35 °C with a NIPAM dosage of 1 g. The fluorescence intensity of the organic matter from the secondary effluent spiked with SMX and decreased after the thermo-responsive membranes were implemented, and filtration with the membrane containing 1 g of NIPAM achieved a lower intensity at a value of 3074.6, according to the analysis of three-dimensional fluorescence excitation–emission spectroscopy. According to the extended Derjaguin–Laudau–Verwey–Overbeek theory analysis, the interfacial free energies of the thermo-responsive membrane with a 1 g dose of NIPAM were higher than the others during filtration. Full article
(This article belongs to the Special Issue Application of Adsorption and Separation Technologies in Water Treatment)
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28 pages, 10833 KiB  
Article
Optimization and Component Identification of Ultrasound-Assisted Extraction of Polyphenols from Coriander (Coriandrum sativum L.) and Evaluation of Polyphenol Content Changes and Antioxidant Activity During Storage
by Heng Yuan, Chunzhi Xie, Yue Ma, Yaqi Miao, Xuehong Chen, Hao Gong and Jun Wang
Separations 2025, 12(8), 217; https://doi.org/10.3390/separations12080217 - 16 Aug 2025
Viewed by 241
Abstract
Coriander (Coriandrum sativum L.) has significant value in the food industry due to its unique flavor and health benefits. However, its polyphenol content and antioxidant activity have not been systematically analyzed during storage. This study optimized the extraction process of coriander polyphenols [...] Read more.
Coriander (Coriandrum sativum L.) has significant value in the food industry due to its unique flavor and health benefits. However, its polyphenol content and antioxidant activity have not been systematically analyzed during storage. This study optimized the extraction process of coriander polyphenols using ultrasound-assisted extraction combined with response surface methodology. The polyphenol composition was systematically identified, and changes in polyphenol content and antioxidant activity during storage were investigated. The optimal process conditions for extracting coriander polyphenols were determined as 40% ethanol concentration, 1:121 g/mL material-to-liquid ratio, 81 °C extraction temperature, and 10 min extraction time. This optimized protocol yielded 16.231 mg GAE/g, a 119.28% increase over conventional methods using the same raw material. Fifty polyphenolic compounds were identified using high-resolution mass spectrometry. The main types of polyphenols identified were quercetin, kaempferol, and hydroxycinnamic acid derivatives. Notably, 41 of these compounds were reported in coriander for the first time. In vitro tests revealed that coriander polyphenols exhibit potent antioxidant properties, with IC50 values of 73.43 μg/mL for DPPH and 82.15 μg/mL for ABTS. Furthermore, the polyphenol content and antioxidant capacity of coriander increased significantly during storage, with total phenolic content rising by 40.5%, DPPH activity by 32.5%, and ABTS activity by 56.5%. Key individual polyphenols showed differential changes: rutin continuously accumulated, while chlorogenic acid and ferulic acid exhibited an initial increase followed by a decrease. This study provides strong technical support for the use of coriander polyphenols in functional foods and medicines. Full article
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11 pages, 371 KiB  
Article
Phytochemical and Nutritional Profile of Apricot, Plum-Apricot, and Plum Stones
by Dasha Mihaylova, Galia Gentscheva, Nadezhda Petkova-Ognyanova, Anton Slavov and Aneta Popova
Separations 2025, 12(8), 216; https://doi.org/10.3390/separations12080216 - 15 Aug 2025
Viewed by 139
Abstract
Fruit stones constitute a significant portion of solid waste generated from the consumption and processing of fruits. This study demonstrated the potential of fruit stones as viable sources of nutritional compounds. The stones from three types of fruits—the “Modesto” apricot, the “Stendesto” plum-apricot, [...] Read more.
Fruit stones constitute a significant portion of solid waste generated from the consumption and processing of fruits. This study demonstrated the potential of fruit stones as viable sources of nutritional compounds. The stones from three types of fruits—the “Modesto” apricot, the “Stendesto” plum-apricot, and the “Stanley” plum—were assessed for their protein, carbohydrate, lipid, and mineral content. Additionally, their total phenolic content, total flavonoid content, and total anthocyanin content were also analyzed. The antioxidant activity, evaluated through four contemporary assays (DPPH, ABTS, FRAP, and CUPRAC), revealed the biological potential of these stones. Notably, the results pertaining to the hybrid plum-apricot variety “Stendesto” are absent from the existing literature, rendering them novel. The findings indicate that the stone of this hybrid has the lowest caloric value in kcal/100 g, including its fat content, when compared to the other studied stones. Therefore, fruit stones can be effectively utilized as innovative food ingredients, aligning with the need for proper waste management and their potential application across various industries. 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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13 pages, 3408 KiB  
Article
Efficient Separation of Lu from Yb Using Rext-P350@Resin: A Promising Route for No-Carrier-Added 177Lu Production
by Jiuquan Qi, Qianwen Chen, Chuanying Liu, Chengliang Xiao and Shuainan Ni
Separations 2025, 12(8), 215; https://doi.org/10.3390/separations12080215 - 15 Aug 2025
Viewed by 184
Abstract
Due to the nearly identical chemical properties of Lu and Yb, the production of no-carrier-added (NCA) 177Lu faces significant challenges in their separation. Achieving efficient and streamlined separation of Lu and Yb is crucial for the production of NCA 177Lu. This [...] Read more.
Due to the nearly identical chemical properties of Lu and Yb, the production of no-carrier-added (NCA) 177Lu faces significant challenges in their separation. Achieving efficient and streamlined separation of Lu and Yb is crucial for the production of NCA 177Lu. This study systematically investigated the separation performance of the commercial Rext-P350 extraction resin for Lu and Yb. Static adsorption experiments revealed that, at a solid–liquid ratio of 8 g/L, both Lu3+ and Yb3+ were nearly completely adsorbed, with saturation adsorption capacities of 25.8 mg/g and 21.5 mg/g, respectively. An increase in the nitric acid concentration in the aqueous phase significantly inhibited adsorption, but the separation factor for Lu3+/Yb3+ remained above 1.88. The adsorption kinetics followed a pseudo-second-order model (R2 > 0.99), with equilibrium reached within 15 min, demonstrating fast adsorption kinetics. Characterization by SEM, FT-IR, and XPS confirmed the chemical coordination between the resin and Lu3+/Yb3+. Dynamic chromatographic separation experiments showed that the Rext-P350 resin exhibited significantly better separation performance for Lu3+/Yb3+ compared to 2-ethylhexylphosphoric acid mono-2-ethylhexyl ester (P507) extraction resin. Leveraging the excellent performance of Rext-P350 resin, a two-stage continuous extraction chromatography process was designed, achieving efficient separation of 0.045 mg of Lu3+ from 200 mg of Yb3+ with a Lu3+ purity of 90.9% and a yield of 98.4%. This study provides a feasible separation technique for the purification of NCA 177Lu. Full article
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34 pages, 10947 KiB  
Article
Hydrophobic Natural Deep Eutectic Solvents for Extraction of Bioactive Compounds: Multiscale Characterization, Quantum Simulations, and Molecular Interaction Studies with Cry j 1 and Amb a 1 Allergens
by Tochukwu Oluwatosin Maduka, Qingyue Wang, Miho Suzuki, Christian Ebere Enyoh, Weiqian Wang and Md. Sohel Rana
Separations 2025, 12(8), 214; https://doi.org/10.3390/separations12080214 - 15 Aug 2025
Viewed by 370
Abstract
This study explores the synthesis, characterization, and extraction efficiency of hydrophobic natural deep eutectic solvents (NADESs), along with the allergen-modulating potential of extracted bioactive compounds. Six NADESs were synthesized using binary combinations of camphor, thymol, eugenol, and menthol (1:1 molar ratio) and characterized [...] Read more.
This study explores the synthesis, characterization, and extraction efficiency of hydrophobic natural deep eutectic solvents (NADESs), along with the allergen-modulating potential of extracted bioactive compounds. Six NADESs were synthesized using binary combinations of camphor, thymol, eugenol, and menthol (1:1 molar ratio) and characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis and differential thermal analysis (TGA/DTA), density functional theory (DFT), and molecular dynamics simulations (MD simulations). Bioactive compounds were extracted from Thujopsis dolabrata wood biomass via ultrasonic-assisted extraction and analyzed using gas chromatography–mass spectrometry (GC–MS). The total essential oil yield, estimated semiquantitatively by summing the peak areas of key terpenoid compounds, ranged from 1.91% to 7.90% across different NADES systems, indicating their varied extraction capacities. Molecular docking was performed to assess their allergen-modulating interactions with Amb a 1 and Cry j 1. All NADESs exhibited single-stage decomposition (110–125 °C) except camphor–menthol, which recrystallized. FTIR and simulations confirmed strong hydrogen bonding in eugenol-based NADESs, particularly menthol–eugenol. Extraction identified 47 bioactive compounds, with 4,5α-Epoxy-3-methoxy-17-methyl-7α-(4-phenyl-1,3-butadienyl)-6β,7β-(oxymethylene) morphinan as the most abundant (9.31–11.16%). It exhibited the highest binding affinity (Cry j 1: −8.60 kcal/mol, Amb a 1: −7.40 kcal/mol) and lowest inhibition concentration (Cry j 1: 0.49 µM, Amb a 1: 3.74 µM), suggesting strong allergen-modulating potential. Hydrophobic interactions and hydrogen bonding drove protein–ligand binding. These findings highlight NADESs as effective, sustainable solvents for extracting bioactive compounds with allergen-modulating potential. Full article
(This article belongs to the Special Issue Green Extraction of Natural Products for Application in Pharmaceuticals, Foods, Cosmetics and Agriculture)
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19 pages, 2448 KiB  
Article
Ultrafiltration of Water Has a Temporary Effect on Cell Numbers, but Profoundly Changes the Composition of Bacterial Populations—The ‘Reset’ Phenomenon
by Benjamin H. Meyer, Bernd Bendinger, Martin Hippelein and Andreas Nocker
Separations 2025, 12(8), 213; https://doi.org/10.3390/separations12080213 - 15 Aug 2025
Viewed by 368
Abstract
Ultrafiltration strips water of bacteria. The common misconception is that the filtrate is thus free of bacteria. This only applies, however, in the case that the filtrate compartment is sterile. In real-world applications, the filtrate is rapidly re-colonized, followed by regrowth. In extreme [...] Read more.
Ultrafiltration strips water of bacteria. The common misconception is that the filtrate is thus free of bacteria. This only applies, however, in the case that the filtrate compartment is sterile. In real-world applications, the filtrate is rapidly re-colonized, followed by regrowth. In extreme cases of low water usage, the cell numbers in the filtrate can even exceed those in the feed water, probably due to a combination of the microbial enrichment of the bulk water from surfaces, regrowth in the water body itself, and nutrient enrichment on the filter membrane. Regrowth is made possible because dissolved nutrients can freely pass through the membranes. This explains why the initial decrease in cell numbers in drinking water installation systems with ultrafiltration is often followed by an increase in the periphery of the plumbing system. The extent of actual regrowth hereby depends mostly on water usage behaviours. A shorter frequency of membrane wash cycles is beneficial for reducing cell numbers. Neither frequent wash cycles nor cleaning in place (CIP) in filtration units, however, seem to modulate the maximal regrowth potential. Although the effect of ultrafiltration on cell numbers is not sustainable, it causes profound changes in the bacterial communities, with highly distinct populations in the feed water and the filtrate. The microbiological “reset” is demonstrated using examples both from the fields of drinking water and water reuse. Overall, our results suggest that ultrafiltration has a profound impact on the microbiome, but the cell numbers in filtrates depend mostly on the water usage and operational conditions. Full article
(This article belongs to the Special Issue Sustainable Biological Removal and Separation Processes in Wastewater Treatment)
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24 pages, 15974 KiB  
Article
Enhancing Copper Leaching from Refractory Copper Oxide Ore Using Organic Cationic Surfactant
by Yang Li, Jue Kou, Chunbao Sun, Peilong Wang and Xiaoli Wang
Separations 2025, 12(8), 212; https://doi.org/10.3390/separations12080212 - 12 Aug 2025
Viewed by 285
Abstract
The copper oxide ore in Zambia exhibits complex mineralogical characteristics, with copper primarily occurring in mica. The local hydrometallurgical plant employs heating–agitation acid leaching, which is hindered by a low leaching rate and prolonged leaching period, resulting in high energy consumption. To enhance [...] Read more.
The copper oxide ore in Zambia exhibits complex mineralogical characteristics, with copper primarily occurring in mica. The local hydrometallurgical plant employs heating–agitation acid leaching, which is hindered by a low leaching rate and prolonged leaching period, resulting in high energy consumption. To enhance the copper leaching efficiency, a systematic study was conducted on the use of organic cationic surfactants to enhance the leaching of the copper oxide ore. The results indicated that the primary copper-bearing mineral in the raw ore is cupriferous biotite, which is the reason for the difficulty in leaching. Under optimal conditions: a sulfuric acid dosage of 45 kg/t, a CTAB dosage of 75 g/t, a leaching temperature of 65 °C, a liquid-to-solid ratio of 2:1, and a leaching time of 120 min, the copper leaching rate reached 78.32%. Compared to the optimal result of regular heating–agitation acid leaching, this approach increased the copper leaching rate by 3.06%, reduced the leaching time by 80 min, and lowered leaching energy consumption without destroying the structure of cupriferous biotite. Mechanistic studies show that organic cations in CTAB neutralize excess anions, thereby weakening the electrostatic Coulomb forces between the interlayer cations and the hexagonal structure. This increases the interlayer spacing of biotite, facilitating the entry of H+ from sulfuric acid into the interlayer. The H+ then reacts with the copper in the biotite, enhancing the copper leaching rate and reducing leaching time. Because CTAB has high degradability, it will not cause persistent pollution to the environment. The use of CTAB as a leaching aid can reduce the energy consumption of heating–agitation acid leaching and reduce the heating cost per ton of ore by USD 6.11–9.36. Full article
(This article belongs to the Special Issue Advances in Novel Beneficiation Technology of Critical Minerals)
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14 pages, 793 KiB  
Article
Chemometric Fingerprinting of Petroleum Hydrocarbons Within Oil Sands Tailings Using Comprehensive Two-Dimensional Gas Chromatography
by Mike Dereviankin, Lesley Warren and Gregory F. Slater
Separations 2025, 12(8), 211; https://doi.org/10.3390/separations12080211 - 12 Aug 2025
Viewed by 246
Abstract
Base Mine Lake (BML) is the first full-scale demonstration of water-capped tailing technology in a pit lake to reclaim lands impacted by surface mining in the Alberta Oil Sands Region (AOSR). Biogeochemical cycling and/or exchange near the fluid water interface (FWI) of the [...] Read more.
Base Mine Lake (BML) is the first full-scale demonstration of water-capped tailing technology in a pit lake to reclaim lands impacted by surface mining in the Alberta Oil Sands Region (AOSR). Biogeochemical cycling and/or exchange near the fluid water interface (FWI) of the organic-rich fluid fine tailings (FFT) can hinder the reclamation process. To monitor this activity, sedimentary depth profiles were collected from three platforms (P1 to P3) at BML. Seventy-four chromatographically well-resolved petroleum hydrocarbon (PHC) isomers were quantified at each depth interval using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC/TOFMS). The range of total concentrations of all isomers examined across the FFT was the highest at P1 (range = 3.6 × 100–5.5 × 103 ng/g TOC), second highest at P2 (range = 3.8 × 100–1.9 × 103 ng/g TOC), and lowest at P3 (range = 5.6 × 100–7.1 × 102 ng/g TOC). The elevated levels of the same isomers across platforms suggest a consistent source fingerprint. While the source fingerprint was mostly consistent across the platforms and depths, Principal Component Analysis (PCA) identified small differences between geospatial locations caused by variations in specific isomer concentrations. Hierarchical Clustering Analysis (HCA) identified the isomers responsible for the PCA separation, showing that the concentrations of low-molecular-weight n-alkanes (C11–C13) and drimane varied compared to the heavier PHCs with depth. These alkanes are the most biodegradable of the compounds identified in this study, and their variations may reflect biogeochemical cycling within the FFT. Combining these statistical tools provided deeper insight into how isomer concentrations vary with depth, helping to identify possible influences like changing inputs, biogeochemical cycling, and species exchange with the water column. Full article
(This article belongs to the Section Forensics/Toxins)
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12 pages, 1615 KiB  
Article
The Separation of Multiple Trace Impurities in Drugs Using an Improved Twin-Column Recycling Chromatography System
by Junwei Fu and Feng Wei
Separations 2025, 12(8), 210; https://doi.org/10.3390/separations12080210 - 11 Aug 2025
Viewed by 182
Abstract
The acquisition of high-purity impurities is pivotal for structural identification and an origin analysis, thereby laying a critical foundation for subsequent toxicological evaluation, quality standard development, and process optimization. This study investigated the feasibility of using a solvent gradient twin-column recycling chromatography technique [...] Read more.
The acquisition of high-purity impurities is pivotal for structural identification and an origin analysis, thereby laying a critical foundation for subsequent toxicological evaluation, quality standard development, and process optimization. This study investigated the feasibility of using a solvent gradient twin-column recycling chromatography technique for the separation and purification of multiple trace impurities in iohexol. In this approach, a modifier with a weaker elution strength than the mobile phase is introduced between two chromatographic columns to form a step gradient solvent system. This gradient slows down the leading edge of the elution band relative to the rear edge, inducing a band compression effect that counteracts band broadening and enhances the chromatographic resolution. By optimizing parameters such as the mobile phase composition, elution mode, and modifier flow rate, three trace impurities were successfully separated and purified from iohexol. Their respective purities were improved from initial concentrations of 0.36%, 0.35%, and 0.15% to 97.82%, 91.56%, and 81.56%, respectively. Leveraging the band compression effect on the target components, the impurities were simultaneously purified and concentrated. These results demonstrate that the proposed method is highly effective for the rapid isolation and preparation of trace pharmaceutical impurities. Full article
(This article belongs to the Section Chromatographic Separations)
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22 pages, 2597 KiB  
Article
Valorization of the Bioactive Potential of Juniperus communis L. Berry Extracts Using a Box–Behnken Design and Characterization of Kernel Oil Compounds
by Theofania Tsitsirigka, Dimitrios Kalompatsios, Vassilis Athanasiadis, Eleni Bozinou, Athanassios I. Sfougaris and Stavros I. Lalas
Separations 2025, 12(8), 209; https://doi.org/10.3390/separations12080209 - 11 Aug 2025
Viewed by 244
Abstract
This study presents a comprehensive valorization of Juniperus communis L., a plant known for its culinary and therapeutic applications. Juniper berries are rich in antioxidant compounds such as polyphenols and ascorbic acid, while their kernels contain volatile terpenes with notable pharmaceutical properties. We [...] Read more.
This study presents a comprehensive valorization of Juniperus communis L., a plant known for its culinary and therapeutic applications. Juniper berries are rich in antioxidant compounds such as polyphenols and ascorbic acid, while their kernels contain volatile terpenes with notable pharmaceutical properties. We optimized extraction parameters through stirring extraction (1:20 g/mL solid-to-solvent ratio, 55% v/v aqueous ethanol, 80 °C, 30 min) and response surface methodology via a Box–Behnken design. The optimal conditions—55% v/v aqueous ethanol at 80 °C for 30 min—yielded a high polyphenol content of 55.11 ± 1.54 mg GAE/g of defatted dry weight. Antioxidant capacity was confirmed through ferric-reducing and radical-scavenging assays, and 11 individual polyphenols (totaling 5.41 ± 0.27 mg/g) were quantified using a validated HPLC-DAD method. Additionally, this study identified several bioactive compounds in juniper berry raw kernel oil, which exhibited a high oleic acid content (58.75 ± 2.76%)—a nutritionally valuable fatty acid contributing to the oil’s strong radical-scavenging activity (399.83 ± 34.18 µmol Trolox equivalents/kg oil). GC–MS analysis revealed 58 volatile compounds, underscoring the terpene-rich profile of the oil and its influence on antioxidant potential and aroma. These findings underscore the dual valorization of juniper berry fruit and kernel for both medicinal and food industries. The aromatic kernel oil and polyphenol-rich extracts offer natural alternatives to synthetic antioxidants, with added benefits of flavor enhancement and promotion of health. Full article
(This article belongs to the Special Issue Advances in the Analysis of Bioactive Plant Extracts: Separation Techniques and Their Applications)
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10 pages, 2339 KiB  
Article
Molluscicidal Activity of the Crude Extract and Fractions of Myrsine parvifolia
by Keyla Nunes Farias Gomes, Leonardo da Silva Rangel, João Claudio Vitoria Ático Leite, Gabriel Rocha Caldas, Arthur Luiz Corrêa, Marcelo Guerra Santos, Leandro Machado Rocha, José Augusto Albuquerque dos Santos and Robson Xavier Faria
Separations 2025, 12(8), 208; https://doi.org/10.3390/separations12080208 - 11 Aug 2025
Viewed by 199
Abstract
As the second most common infectious parasitic disease in the world, schistosomiasis is present in Brazil, mainly in the Northeast and Southeast regions. Currently, the recommended form of prevention is controlling this disease’s intermediate host, mollusks of the Biomphalaria genus, using the chemical [...] Read more.
As the second most common infectious parasitic disease in the world, schistosomiasis is present in Brazil, mainly in the Northeast and Southeast regions. Currently, the recommended form of prevention is controlling this disease’s intermediate host, mollusks of the Biomphalaria genus, using the chemical molluscicide Bayluscide WP 70®. This synthetic molluscicide is expensive, has low selectivity for Biomphalaria glabrata species, and is toxic to the environment. In this context, the use of natural products such as molluscicides represents a sustainable control method. The objective of this study was to evaluate the molluscicidal effects of a crude ethanolic extract of the leaves and stems and fractions of the species Myrsine parvifolia on the mollusk Biomphalaria glabrata. Methods: The methodology was adapted from standards defined by the World Health Organization (WHO), where the molluscicidal activity of Myrsine parvifolia was investigated as an alternative for the population control of Biomphalaria glabrata and That’s right. environmental toxicity was evaluated using the Physella sp. The results revealed that the stem ethanolic crude extract exhibited activity after 24 h of exposure, with an LC50 of 207.4 mg/L and an LC90 of 256.2 mg/L. Conclusions: Myrsine parvifolia can be used as a sustainable biological alternative for the population control of Biomphalaria glabrata snails, especially for poor populations and inaccessible regions. Full article
(This article belongs to the Special Issue Advanced Research on Extraction and Analysis of Plant Extracts)
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18 pages, 3921 KiB  
Article
Ion-Exchange Membrane Permselectivity: Experimental Evaluation of Concentration Dependence, Ionic Species Selectivity, and Temperature Response
by Junyi Lv, Xiaojing Zhu, Xi Wu and Hongfei Guan
Separations 2025, 12(8), 207; https://doi.org/10.3390/separations12080207 - 9 Aug 2025
Viewed by 178
Abstract
Ion-exchange membranes (IEMs) are widely used in reverse-electrodialysis (RED) technology, which can collect the salinity gradient energy between concentrated and diluted solutions and convert it into electromotive force (EMF) to drive power generation and hydrogen production. Recent studies have indicated that the permselectivity [...] Read more.
Ion-exchange membranes (IEMs) are widely used in reverse-electrodialysis (RED) technology, which can collect the salinity gradient energy between concentrated and diluted solutions and convert it into electromotive force (EMF) to drive power generation and hydrogen production. Recent studies have indicated that the permselectivity of IEMs is vital to determining the performance of an RED stack. In this study, the influences of solution concentration, ion species, and solution temperature on the permselectivity of IEMs were experimentally investigated. The results demonstrate that the permselectivity of IEMs decreases with increasing concentrations of KAc, LiCl, and LiBr solutions for both concentrated solutions (3–5 M) and dilute solutions (0.02–0.2 M). Further, through comparing the LiBr and KBr solutions as well as the LiCl, KCl, and NH4Cl solutions, respectively, K+ demonstrates a higher permselectivity than Li+, and both of which are smaller than NH4+ under the same cation and concentration conditions. Moreover, another test was conducted using three potassium salt solutions with different anions, and the experimental permselectivity order is Ac− > Br− > Cl−. A slight increase in solution temperature enhances the permselectivity of IEMs due to the increase in ionic mobility. However, an excessive temperature is detrimental to membrane stability and thus reduces permselectivity. It can be seen that ions with low hydration energy, a small hydration radius, and high mobility show a higher permselectivity. Full article
(This article belongs to the Section Purification Technology)
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21 pages, 3287 KiB  
Article
Experimental and Quantum Mechanical Studies of Efficient Re(VII)/Mo(VI) Separation by a Magnetic Amino-Functionalized Polymer
by Bojana Marković, Goran Janjić, Antonije Onjia, Tamara Tadić, Plamen Stefanov and Aleksandra Nastasović
Separations 2025, 12(8), 206; https://doi.org/10.3390/separations12080206 - 7 Aug 2025
Viewed by 261
Abstract
A previously synthesized and functionalized magnetic glycidyl methacrylate-based nanocomposite, mPGMT-deta, was tested as a sorbent for Re(VII) oxoanions in Mo(VI)-containing solutions. The effect of pH on the removal efficiency and the separation factor was examined in the range of 2 to 9. A [...] Read more.
A previously synthesized and functionalized magnetic glycidyl methacrylate-based nanocomposite, mPGMT-deta, was tested as a sorbent for Re(VII) oxoanions in Mo(VI)-containing solutions. The effect of pH on the removal efficiency and the separation factor was examined in the range of 2 to 9. A maximum separation factor (βRe/Mo) of 8.85 was observed at pH 6. The nature of rhenium oxoanions binding to the active sites of mPGMT-deta was analyzed using density functional theory (DFT). The calculations indicated that the formation of MoO42−//hedetaH22+ adduct is electrostatically favored at pH 6, while the inclusion of solvation effects makes the formation of ReO4−//hedetaH22+ adduct thermodynamically more favorable. Solvation played a dominant role in determining the selectivity of oxoanion sorption to the nanocomposite. The adsorption isotherm, kinetics, and thermodynamics of Re(VII) onto mPGMT-deta were determined. The equilibrium data were best-fitted using the Langmuir adsorption model (R2 = 0.999), with a maximum sorption capacity for Re(VII) of 0.43 mmol/g. The uptake kinetics of the sorption process obeyed the pseudo-second-order model, with the influence of diffusion and external mass transfer. Based on the thermodynamic parameters, Re(VII) sorption was spontaneous and endothermic. Full article
(This article belongs to the Special Issue New and Modified Polymers for Detection and Removal of Pollutants from Water and Air)
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18 pages, 4475 KiB  
Article
Preparation of EDTA-2Na-Fe3O4-Activated Carbon Composite and Its Adsorption Performance for Typical Heavy Metals
by Yannan Lv, Shenrui Han, Wenqing Wen, Xinzhu Bai, Qiao Sun, Li Chen, Haonan Zhang, Fansong Mu and Meng Luo
Separations 2025, 12(8), 205; https://doi.org/10.3390/separations12080205 - 6 Aug 2025
Viewed by 229
Abstract
This study developed a new magnetic adsorbent from waste coconut shells using high-temperature carbonization, EDTA-2Na chelation, and Fe3O4 magnetic loading. Response surface methodology optimized the preparation conditions to a mass ratio of activated carbon: EDTA-2Na:Fe3O4 = 2:0.6:0.2. [...] Read more.
This study developed a new magnetic adsorbent from waste coconut shells using high-temperature carbonization, EDTA-2Na chelation, and Fe3O4 magnetic loading. Response surface methodology optimized the preparation conditions to a mass ratio of activated carbon: EDTA-2Na:Fe3O4 = 2:0.6:0.2. Characterization (SEM, XRD, FT-IR, and EDS) showed that EDTA-2Na increased the surface carboxyl and amino group density, while Fe3O4 loading (Fe concentration 6.83%) provided superior magnetic separation performance. The optimal adsorption conditions of Cu2+ by EDTA-2Na-Fe3O4-activated carbon composite material are as follows: when pH = 5.0 and the initial concentration is 180 mg/L, the equilibrium adsorption capacity reaches 174.96 mg/g, and the removal rate reaches 97.2%. The optimal adsorption conditions for Pb2+ are as follows: when pH = 6.0 and the initial concentration is 160 mg/L, the equilibrium adsorption capacity reaches 157.60 mg/g, and the removal rate reaches 98.5%. The optimal adsorption conditions for Cd2+ are pH = 8.0 and an initial concentration of 20 mg/L. The equilibrium adsorption capacity reaches 18.76 mg/g, and the removal rate reaches 93.8%. The adsorption followed the pseudo-second-order kinetics (R2 > 0.95) and Langmuir/Freundlich isotherm models, indicating chemisorption dominance. Desorption experiments using 0.1 mol/L HCl and EDTA-2Na achieved efficient desorption (>85%), and the material retained over 80% of its adsorption capacity after five cycles. This cost-effective and sustainable adsorbent offers a promising solution for heavy metal wastewater treatment. Full article
(This article belongs to the Special Issue Application of Advanced Materials and Technologies in the Separation and Adsorption)
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20 pages, 462 KiB  
Article
Chromatographic and Chemometric Characterization of the Two Wild Edible Mushrooms Fistulina hepatica and Clitocybe nuda: Insights into Nutritional, Phenolic, and Antioxidant Profiles
by Ana Saldanha, Mikel Añibarro-Ortega, Adriana K. Molina, José Pinela, Maria Inês Dias and Carla Pereira
Separations 2025, 12(8), 204; https://doi.org/10.3390/separations12080204 - 2 Aug 2025
Viewed by 347
Abstract
Fistulina hepatica (Schaeff.) With. and Clitocybe nuda (Bull.) H.E. Bigelow & A.H. Sm. are wild edible mushrooms with nutritional and functional potential that remain insufficiently characterized. This study provides the first comparative assessment of their nutritional profiles, phenolic composition, and antioxidant activity, using [...] Read more.
Fistulina hepatica (Schaeff.) With. and Clitocybe nuda (Bull.) H.E. Bigelow & A.H. Sm. are wild edible mushrooms with nutritional and functional potential that remain insufficiently characterized. This study provides the first comparative assessment of their nutritional profiles, phenolic composition, and antioxidant activity, using specimens collected from Montesinho Natural Park (Portugal). Proximate composition, organic and phenolic acids, free sugars, and fatty acids were analyzed by chromatographic methods, and antioxidant capacity was assessed through OxHLIA and TBARS assays. F. hepatica showed higher carbohydrates (9.3 ± 0.2 g/100 g fw) and estimated energy values (43 ± 1 kcal/100 g fw), increased phenolic acids content (2.7 ± 0.1 mg/g extract), and the exclusive presence of p-coumaric and cinnamic acids, along with OxHLIA activity (IC50 = 126 ± 5 µg/mL at Δt = 60 min). C. nuda displayed higher protein (2.5 ± 0.1 g/100 g dw) and quinic acid contents (4.13 ± 0.02 mg/g extract), a PUFA-rich profile, and greater TBARS inhibition (EC50 = 303 ± 17 µg/mL). These findings highlight distinct and complementary bioactive traits, supporting their valorization as natural functional ingredients. Their compositional features offer promising applications in sustainable food systems and nutraceutical development, encouraging further investigations into safety, bioaccessibility, and formulation strategies. Notably, F. hepatica is best consumed at a young developmental stage, as its sensory properties tend to decline with maturity. Full article
(This article belongs to the Special Issue Advanced Separation Methods for Safety Assessment and Valorization of By-Products)
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23 pages, 2888 KiB  
Review
Machine Learning in Flocculant Research and Application: Toward Smart and Sustainable Water Treatment
by Caichang Ding, Ling Shen, Qiyang Liang and Lixin Li
Separations 2025, 12(8), 203; https://doi.org/10.3390/separations12080203 - 1 Aug 2025
Viewed by 398
Abstract
Flocculants are indispensable in water and wastewater treatment, enabling the aggregation and removal of suspended particles, colloids, and emulsions. However, the conventional development and application of flocculants rely heavily on empirical methods, which are time-consuming, resource-intensive, and environmentally problematic due to issues such [...] Read more.
Flocculants are indispensable in water and wastewater treatment, enabling the aggregation and removal of suspended particles, colloids, and emulsions. However, the conventional development and application of flocculants rely heavily on empirical methods, which are time-consuming, resource-intensive, and environmentally problematic due to issues such as sludge production and chemical residues. Recent advances in machine learning (ML) have opened transformative avenues for the design, optimization, and intelligent application of flocculants. This review systematically examines the integration of ML into flocculant research, covering algorithmic approaches, data-driven structure–property modeling, high-throughput formulation screening, and smart process control. ML models—including random forests, neural networks, and Gaussian processes—have successfully predicted flocculation performance, guided synthesis optimization, and enabled real-time dosing control. Applications extend to both synthetic and bioflocculants, with ML facilitating strain engineering, fermentation yield prediction, and polymer degradability assessments. Furthermore, the convergence of ML with IoT, digital twins, and life cycle assessment tools has accelerated the transition toward sustainable, adaptive, and low-impact treatment technologies. Despite its potential, challenges remain in data standardization, model interpretability, and real-world implementation. This review concludes by outlining strategic pathways for future research, including the development of open datasets, hybrid physics–ML frameworks, and interdisciplinary collaborations. By leveraging ML, the next generation of flocculant systems can be more effective, environmentally benign, and intelligently controlled, contributing to global water sustainability goals. Full article
(This article belongs to the Section Environmental Separations)
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17 pages, 3206 KiB  
Article
Inverse Punicines: Isomers of Punicine and Their Application in LiAlO2, Melilite and CaSiO3 Separation
by Maximilian H. Fischer, Ali Zgheib, Iliass El Hraoui, Alena Schnickmann, Thomas Schirmer, Gunnar Jeschke and Andreas Schmidt
Separations 2025, 12(8), 202; https://doi.org/10.3390/separations12080202 - 30 Jul 2025
Viewed by 233
Abstract
The transition to sustainable energy systems demands efficient recycling methods for critical raw materials like lithium. In this study, we present a new class of pH- and light-switchable flotation collectors based on isomeric derivatives of the natural product Punicine, termed inverse Punicines. [...] Read more.
The transition to sustainable energy systems demands efficient recycling methods for critical raw materials like lithium. In this study, we present a new class of pH- and light-switchable flotation collectors based on isomeric derivatives of the natural product Punicine, termed inverse Punicines. These amphoteric molecules were synthesized via a straightforward four-step route and structurally tuned for hydrophobization by alkylation. Their performance as collectors was evaluated in microflotation experiments of lithium aluminate (LiAlO2) and silicate matrix minerals such as melilite and calcium silicate. Characterization techniques including ultraviolet-visible (UV-Vis), nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectroscopy as well as contact angle, zeta potential (ζ potential) and microflotation experiments revealed strong pH- and structure-dependent interactions with mineral surfaces. Notably, N-alkylated inverse Punicine derivatives showed high flotation yields for LiAlO2 at pH of 11, with a derivative possessing a dodecyl group attached to the nitrogen as collector achieving up to 86% recovery (collector conc. 0.06 mmol/L). Preliminary separation tests showed Li upgrading from 5.27% to 6.95%. Radical formation and light-response behavior were confirmed by ESR and flotation tests under different illumination conditions. These results demonstrate the potential of inverse Punicines as tunable, sustainable flotation reagents for advanced lithium recycling from complex slag systems. Full article
(This article belongs to the Special Issue Application of Green Flotation Technology in Mineral Processing)
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17 pages, 2627 KiB  
Article
Cuscohygrine and Hygrine as Biomarkers for Coca Leaf Chewing: Analytical Challenges in GC-MS Detection and Implications for the Differentiation of Cocaine Use in Forensic Toxicology
by Nélida C. Rubio, Iván Alvarez-Freire, Pamela Cabarcos-Fernández, María J. Tabernero-Duque, Inés Sánchez-Sellero, Antonio Moreda-Piñeiro, Pilar Bermejo-Barrera and Ana M. Bermejo-Barrera
Separations 2025, 12(8), 201; https://doi.org/10.3390/separations12080201 - 30 Jul 2025
Viewed by 291
Abstract
Cuscohygrine (CUS) and hygrine (HYG) are pyrrolidine alkaloids proposed as biomarkers of coca leaf consumption, a culturally accepted practice in some Latin American countries. Differentiating legal coca use from illicit cocaine consumption holds forensic importance. While LC-MS/MS is preferred, GC-MS remains widely used [...] Read more.
Cuscohygrine (CUS) and hygrine (HYG) are pyrrolidine alkaloids proposed as biomarkers of coca leaf consumption, a culturally accepted practice in some Latin American countries. Differentiating legal coca use from illicit cocaine consumption holds forensic importance. While LC-MS/MS is preferred, GC-MS remains widely used in Latin American toxicology labs due to accessibility. This study critically evaluates the analytical limitations of GC-MS for detecting CUS and HYG in biological matrices. Key parameters—injector temperature (180–290 °C), injection mode (split/splitless), solvent, liner condition, and matrix—were systematically studied. GC-MS showed significant limitations: low-abundance, non-specific fragments (m/z 42, 84, 98, 140) failed to meet the identification criteria in SIM mode. Thermal degradation of CUS to HYG and CUS-d6 to HYG-d3 was observed, especially with splitless injection and aged liners. Matrix effects produced signal enhancement ranging from +29% to +316%, meaning that analyte responses in biological samples were significantly higher than in neat standards, likely due to reduced degradation or adsorption. Although deuterated internal standards (CUS-d6) partially corrected signal variability and matrix enhancement, these corrections were not sufficient to overcome the fundamental limitations of GC-MS, including poor ion specificity and compound instability. These findings support the need for LC-MS/MS-based approaches for reliable alkaloid detection and question the suitability of GC-MS for CUS analysis in forensic toxicology contexts. Full article
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11 pages, 1070 KiB  
Article
Directed Message-Passing Neural Networks for Gas Chromatography
by Daniel Struk, Rizky Ilhamsyah, Jean-Marie D. Dimandja and Peter J. Hesketh
Separations 2025, 12(8), 200; https://doi.org/10.3390/separations12080200 - 30 Jul 2025
Viewed by 291
Abstract
In this paper, the directed message-passing neural network architecture is used to predict several quantities of interest in gas chromatography: retention times, Clarke-Glew 3-point thermodynamic parameters for simulation, and retention indices. The retention index model was trained with 48,803 training samples and reached [...] Read more.
In this paper, the directed message-passing neural network architecture is used to predict several quantities of interest in gas chromatography: retention times, Clarke-Glew 3-point thermodynamic parameters for simulation, and retention indices. The retention index model was trained with 48,803 training samples and reached 1.9–2.6% accuracy, whereas the thermodynamic parameters and retention time were trained by using 230 training data samples yielding 17% accuracy. Furthermore, the accuracy as a function of the number of training samples is investigated, showing the necessity of large, accurate datasets for training deep learning-based models. Lastly, several uses of such a model for the identification of compounds and the optimization of GC parameters are discussed. Full article
(This article belongs to the Special Issue State of the Art and Challenges in the Analysis of Volatile Organic Compounds)
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17 pages, 3944 KiB  
Article
Functionalized Magnetic Nanoparticles as Recyclable Draw Solutes for Forward Osmosis: A Sustainable Approach to Produced Water Reclamation
by Sunith B. Madduri and Raghava R. Kommalapati
Separations 2025, 12(8), 199; https://doi.org/10.3390/separations12080199 - 29 Jul 2025
Viewed by 451
Abstract
Magnetic nanoparticles (MNPs), especially iron oxide (Fe3O4), display distinctive superparamagnetic characteristics and elevated surface-area-to-volume ratios, facilitating improved physicochemical interactions with solutes and pollutants. These characteristics make MNPs strong contenders for use in water treatment applications. This research investigates the [...] Read more.
Magnetic nanoparticles (MNPs), especially iron oxide (Fe3O4), display distinctive superparamagnetic characteristics and elevated surface-area-to-volume ratios, facilitating improved physicochemical interactions with solutes and pollutants. These characteristics make MNPs strong contenders for use in water treatment applications. This research investigates the application of iron oxide MNPs synthesized via co-precipitation as innovative draw solutes in forward osmosis (FO) for treating synthetic produced water (SPW). The FO membrane underwent surface modification with sulfobetaine methacrylate (SBMA), a zwitterionic polymer, to increase hydrophilicity, minimize fouling, and elevate water flux. The SBMA functional groups aid in electrostatic repulsion of organic and inorganic contaminants, simultaneously encouraging robust hydration layers that improve water permeability. This adjustment is vital for sustaining consistent flux performance while functioning with MNP-based draw solutions. Material analysis through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) verified the MNPs’ thermal stability, consistent morphology, and modified surface chemistry. The FO experiments showed a distinct relationship between MNP concentration and osmotic efficiency. At an MNP dosage of 10 g/L, the peak real-time flux was observed at around 3.5–4.0 L/m2·h. After magnetic regeneration, 7.8 g of retrieved MNPs generated a steady flow of ~2.8 L/m2·h, whereas a subsequent regeneration (4.06 g) resulted in ~1.5 L/m2·h, demonstrating partial preservation of osmotic driving capability. Post-FO draw solutions, after filtration, exhibited total dissolved solids (TDS) measurements that varied from 2.5 mg/L (0 g/L MNP) to 227.1 mg/L (10 g/L MNP), further validating the effective dispersion and solute contribution of MNPs. The TDS of regenerated MNP solutions stayed similar to that of their fresh versions, indicating minimal loss of solute activity during the recycling process. The combined synergistic application of SBMA-modified FO membranes and regenerable MNP draw solutes showcases an effective and sustainable method for treating produced water, providing excellent water recovery, consistent operational stability, and opportunities for cyclic reuse. Full article
(This article belongs to the Section Purification Technology)
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14 pages, 1663 KiB  
Article
Carbon Dioxide Absorption by Polyethylene Glycol Dimethyl Ether Modified by 2-methylimidazole
by Yan Wu, Zicheng Wang, Hui Yu, Bin Ding, Ke Fei, Xueli Ma, Baoshen Xu, Yonghu Zhang, Xiaoning Fu, Bowen Ding and Nan Li
Separations 2025, 12(8), 198; https://doi.org/10.3390/separations12080198 - 28 Jul 2025
Viewed by 312
Abstract
Developing and utilizing capture and storage technologies for CO2 has become a critical research topic due to the significant greenhouse effect caused by excessive CO2 emissions. A conventional physical absorption process for CO2 capture is polyethylene glycol dimethyl ether (NHD); [...] Read more.
Developing and utilizing capture and storage technologies for CO2 has become a critical research topic due to the significant greenhouse effect caused by excessive CO2 emissions. A conventional physical absorption process for CO2 capture is polyethylene glycol dimethyl ether (NHD); however, its limited application range is caused by its poor absorption of CO2 at low pressures. In this work, the CO2 absorption of NHD was enhanced by combining NHD with a novel chemical absorbent 2-methylimidazole (2-mIm)-ethylene glycol (EG) solution to improve CO2 absorption. Viscosity and CO2 solubility were examined in various compositions. The CO2 solubility in the mixed solution was found to be at maximum when the mass fractions of NHD, 2-mIm, and EG were 20%, 40%, and 40%, respectively. In comparison to pure NHD, the solubility of CO2 in this mixed solution at 30 °C and 0.5 MPa increased by 161.2%, and the desorption heat was less than 30 kJ/mol. The complex solution exhibits high selectivity and favorable regeneration performance in the short term. However, it is more sensitive to moisture content. The results of this study can provide important data to support the construction of new low-energy solvent systems and the development of novel CO2 capture processes. Full article
(This article belongs to the Section Separation Engineering)
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19 pages, 2475 KiB  
Article
Efficient Extraction of 1,2-Dichloroethane from Wastewater Using Hydrophobic Deep Eutectic Solvents: A Green Approach
by Irfan Wazeer, Abdullah Omair, Lahssen El Blidi, Salim Mokraoui, Emad Ali and Mohamed K. Hadj-Kali
Separations 2025, 12(8), 197; https://doi.org/10.3390/separations12080197 - 27 Jul 2025
Viewed by 351
Abstract
This study provides a thorough examination of the utilization of hydrophobic deep eutectic solvents (HDESs) for the extraction of 1,2-dichloroethane (1,2-DCA) from effluent, with an emphasis on a sustainable and environmentally friendly approach. The extraction efficacy of six HDES systems was initially evaluated, [...] Read more.
This study provides a thorough examination of the utilization of hydrophobic deep eutectic solvents (HDESs) for the extraction of 1,2-dichloroethane (1,2-DCA) from effluent, with an emphasis on a sustainable and environmentally friendly approach. The extraction efficacy of six HDES systems was initially evaluated, and the combinations of thymol/camphor (Thy/Cam) and menthol/thymol (Men/Thy) exhibited superior performance. Subsequently, these two HDESs were chosen for a comprehensive parametric analysis. The impact of contact time demonstrated that extraction equilibrium was reached at 15 min for both systems, thereby achieving a balance between high efficiency and time efficiency. Next, the impact of the HDES-to-water mass ratio was investigated. A 1:1 ratio was determined to be the most effective, as it minimized solvent consumption and provided high efficiency. An additional examination of the molar ratios of the HDES components revealed that the 1:1 ratio exhibited the most effective extraction performance. This was due to the fact that imbalances in the solvent mixture resulted in diminished efficiency as a result of disrupted molecular interactions. The extraction efficiency was significantly influenced by the initial concentration of 1,2-DCA, with higher concentrations resulting in superior results as a result of the increased mass transfer driving forces. In general, the Men/Thy and Thy/Cam systems have shown noteworthy stability and efficiency under different conditions, which makes them highly suitable for large-scale applications. Full article
(This article belongs to the Special Issue Green Separation and Purification Technology)
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27 pages, 1893 KiB  
Article
Separating 2-Propanol and Water: A Comparative Study of Extractive Distillation, Salting-Out, and Extraction
by Aleksandra Sander, Marko Rogošić, Leonarda Frljak, Daniela Vasiljević, Iva Blažević and Jelena Parlov Vuković
Separations 2025, 12(8), 196; https://doi.org/10.3390/separations12080196 - 26 Jul 2025
Viewed by 510
Abstract
Separating azeotropes is an important, difficult, and expensive task, in particular for the 2-propanol–water mixture. The literature on the problem is rich in modeling studies but often lacking even the simplest experimental confirmation. In this paper, extractive distillation, liquid–liquid equilibrium-based extraction, and salting-out [...] Read more.
Separating azeotropes is an important, difficult, and expensive task, in particular for the 2-propanol–water mixture. The literature on the problem is rich in modeling studies but often lacking even the simplest experimental confirmation. In this paper, extractive distillation, liquid–liquid equilibrium-based extraction, and salting-out were experimentally tested for the desired separation. Among the four tested extractive distillation entrainers, none was able—in the investigated experimental setup—to push the system over the azeotropic composition threshold. Four novel hydrophobic deep eutectic extraction media were tested for the desired separation, and those based on menthol or thymol with decanoic acid were found most promising. Among 16 tested salting-out agents, 5 of them produced two-liquid phases, and only 4 hydrophilic inorganic salts promoted 2-propanol separation, with sodium carbonate being the most promising candidate. The purity of the products was tested with FTIR and 1H-NMR. The experimental findings were compared with COSMO-RS model predictions, with moderate success. Full article
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23 pages, 1784 KiB  
Article
Study on the Adsorption Characteristics of Spirulina Dry Powder Biomass for Rare Earth Element Praseodymium(III): Adsorption Isotherms, Kinetics, and Thermodynamics Analysis
by Zhenxiang Hu, Caixia Zhang and Qing Shu
Separations 2025, 12(8), 195; https://doi.org/10.3390/separations12080195 - 25 Jul 2025
Viewed by 408
Abstract
Aimed at developing an economical and efficient biosorbent for the adsorption and separation of rare earth ions, this study employed Spirulina dry powder biomass as a biosorbent to investigate its removal performance for Pr3+ in aqueous solutions. Experimental results demonstrated that under [...] Read more.
Aimed at developing an economical and efficient biosorbent for the adsorption and separation of rare earth ions, this study employed Spirulina dry powder biomass as a biosorbent to investigate its removal performance for Pr3+ in aqueous solutions. Experimental results demonstrated that under optimized conditions (pH = 5, adsorbent dosage = 2.0 g/L, initial Pr3+ concentration = 100 mg/L, and adsorption time = 60 min), the removal efficiency of Pr3+ reached 79.0%. FT-IR and XPS characterization confirmed the participation of various functional groups on the Spirulina surface in the adsorption process. When 0.1 mol/L HNO3 was used as the desorption agent, the desorption rate of Pr3+ from Spirulina reached 91.7%, demonstrating excellent regeneration performance. At different temperatures (298–318 K), the adsorption data were fitted using Langmuir, Freundlich, Dubinin–Radushkevich, and Redlich–Peterson models. Among them, the Langmuir model (R2 ranged from 0.993 to 0.999) provided the best fit, and the adsorption capacity of Spirulina for Pr3+ was in the range of 51.10 to 55.31 mg/g. Kinetic studies revealed that the pseudo-second-order model (R2 = 0.999) best described the adsorption process, with a rate constant of 0.054 g/(mg·min) (R2 was 0.999) at an initial Pr3+ concentration of 300 mg/L, indicating chemisorption-controlled behavior. Thermodynamic parameter analysis showed that within the experimental temperature range, ΔG0 < 0 and ΔS0 > 0, confirming that the adsorption process was spontaneous and endothermic. This study provides a novel technical approach for the green recovery of rare earth elements and highlights the potential of Spirulina biomass in rare earth resource recycling. Full article
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14 pages, 4700 KiB  
Article
Pilot-Scale Phycocyanin Extraction by the Green Two-Step Ultrasound-Based UltraBlu Process
by Rosaria Lauceri, Melissa Pignataro, Antonio Giorgi, Antonio Idà and Lyudmila Kamburska
Separations 2025, 12(8), 194; https://doi.org/10.3390/separations12080194 - 25 Jul 2025
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Abstract
Phycocyanin is a natural, non-toxic, blue pigment-protein with many commercial applications. Its exploitation in various biotechnological sectors strongly depends on its purity grade (P). Phycocyanin is largely used in food industry where a low purity grade is required, while its widespread use in [...] Read more.
Phycocyanin is a natural, non-toxic, blue pigment-protein with many commercial applications. Its exploitation in various biotechnological sectors strongly depends on its purity grade (P). Phycocyanin is largely used in food industry where a low purity grade is required, while its widespread use in sectors requiring a higher purity is hampered by the cost of large-scale industrial production. Industry, in fact, needs simple, easily scalable and cost-effective procedures to ensure sustainable production of high-quality pigment. In this work we applied the innovative two-step ultrasound-based process UltraBlu to the pilot-scale production of phycocyanin. A total of 50 L of biomass suspension of commercial Spirulina were processed in batch mode. The pigment extract was obtained in one day, including the biomass harvesting. Food/cosmetic grade (P = 1.41–1.76) and a good yield (Y = 59.2–76.1%) were achieved. The initial results obtained suggest that UltraBlu can be an effective scalable process suitable to produce phycocyanin also on an industrial scale. Full article
(This article belongs to the Special Issue Application of Sustainable Separation Techniques in Food Processing)
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