Separations

20 pages, 641 KiB

Open AccessReview

Nanoplastics: From Separations to Analysis—Challenges and Limitations

by Justyna Ośko, Kornelia Kadac-Czapska, Katarzyna Jażdżewska, Natalia Nowak, Piotr Kowalczyk and Małgorzata Grembecka

Separations 2025, 12(7), 185; https://doi.org/10.3390/separations12070185 (registering DOI) - 15 Jul 2025

Abstract

The issue of nanoplastics (NPs) in the environment, following that of microplastics (MPs), is receiving increasing attention in the scientific community. Due to their size, these particles require the development and application of new methods for both quantitative and qualitative determination. Consequently, techniques [...] Read more.

The issue of nanoplastics (NPs) in the environment, following that of microplastics (MPs), is receiving increasing attention in the scientific community. Due to their size, these particles require the development and application of new methods for both quantitative and qualitative determination. Consequently, techniques commonly used for analyzing MPs may prove ineffective in the context of NPs. Isolating NPs from samples with complex matrices poses a significant challenge that directly affects analytical outcomes. This paper aims to discuss the main challenges encountered during the analysis of NPs in environmental samples. Various methods for the visualization and identification of NPs are examined, with a focus on microscopic, spectroscopic, and thermal techniques. The advantages and limitations of analytical approaches reported in the literature are summarized, offering guidance for the future development and standardization of methods used to determine NPs in environmental contexts. Full article

13 pages, 1819 KiB

Open AccessArticle

Numerical Investigation of 2D Ordered Pillar Array Columns: An Algorithm of Unit-Cell Automatic Generation and the Corresponding CFD Simulation

by Qihao Jiang, Stefano Rocca, Kareem Shaikhuzzaman and Simone Dimartino

Separations 2025, 12(7), 184; https://doi.org/10.3390/separations12070184 (registering DOI) - 15 Jul 2025

Abstract

This paper presents a numerical investigation into the generation of 2D ordered pillar array columns for liquid chromatography columns, focusing on the development of an algorithm for the automatic creation of unit-cell morphologies and their subsequent computational fluid dynamics (CFD) simulation. The algorithm [...] Read more.

This paper presents a numerical investigation into the generation of 2D ordered pillar array columns for liquid chromatography columns, focusing on the development of an algorithm for the automatic creation of unit-cell morphologies and their subsequent computational fluid dynamics (CFD) simulation. The algorithm is developed to incorporate functional and operational constraints, which ensure that the generated structures are permeable and suitable for chromatographic separations. The functional constraints include the principal pathway and no dry void constraints, while the operational constraints involve symmetry and porosity thresholds. The algorithm’s efficacy is demonstrated with a reduction rate of 97.8% for order 5 matrices. CFD simulations of the generated morphologies reveal that the homogeneity of the fluid velocity profile within the unit cell is a key determinant of separation performance, suggesting that refining the resolution of discrete unit cells could enhance separation efficiency. Future work will explore the inclusion of more complex morphologies and the impact of particle shape and size on separation efficiency. Full article

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16 pages, 1369 KiB

Open AccessArticle

Optimized Ethyl Chloroformate Derivatization Using a Box–Behnken Design for Gas Chromatography–Mass Spectrometry Quantification of Gallic Acid in Wine

by Sofia Botta, Roberta Piacentini, Chiara Cappelletti, Alessio Incocciati, Alberto Boffi, Alessandra Bonamore and Alberto Macone

Separations 2025, 12(7), 183; https://doi.org/10.3390/separations12070183 - 9 Jul 2025

Viewed by 126

Abstract

Gallic acid, a major phenolic compound in wine, significantly influences its sensory profile and health-related properties, making its accurate measurement essential for both enological and nutritional studies. In this context, a derivatization protocol for gallic acid using ethyl chloroformate (ECF) was developed and [...] Read more.

Gallic acid, a major phenolic compound in wine, significantly influences its sensory profile and health-related properties, making its accurate measurement essential for both enological and nutritional studies. In this context, a derivatization protocol for gallic acid using ethyl chloroformate (ECF) was developed and optimized for GC-MS analysis, with experimental conditions refined through a Box–Behnken Design (BBD). The BBD systematically investigated the effects of three critical reagent volumes: ethyl chloroformate, pyridine, and ethanol. This approach elucidated complex interactions and quadratic effects, leading to a predictive second-order polynomial model and identifying the optimal derivatization conditions for maximum yield (137 µL of ethyl chloroformate, 51 µL of pyridine, and 161 µL of ethanol per 150 µL of wine). The BBD-optimized GC-MS method was validated and successfully applied to quantify gallic acid in diverse commercial wine samples (white, red, conventional, natural). A key finding was the method’s wide dynamic range, enabling accurate quantification from 5 up to over 600 µg/mL without sample dilution. This work represents, to our knowledge, the first application of a BBD for optimizing the ethyl chloroformate derivatization of gallic acid, providing a robust, efficient, and widely applicable analytical tool for routine quality control and enological research. Full article

(This article belongs to the Special Issue Innovative Analytical Strategies Based on Mass Spectrometry in Food Analysis)

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22 pages, 1203 KiB

Open AccessReview

Impact of Use of Ultrasound-Assisted Extraction on the Quality of Brazil Nut Oil (Bertholletia excelsa HBK)

by Orquidea Vasconcelos dos Santos, Sara Camila Vidal Freires, Helen Cristina de Oliveira Palheta and Paulo Henrique de Melo Ferreira

Separations 2025, 12(7), 182; https://doi.org/10.3390/separations12070182 - 8 Jul 2025

Viewed by 243

Abstract

The quality of materials extracted from plant sources, such as oilseeds, is significantly affected by the extraction techniques employed. Thermo-photosensitive bioactive compounds are especially susceptible, often resulting in a loss of functional properties during conventional processing. In this context, studies involving unconventional or [...] Read more.

The quality of materials extracted from plant sources, such as oilseeds, is significantly affected by the extraction techniques employed. Thermo-photosensitive bioactive compounds are especially susceptible, often resulting in a loss of functional properties during conventional processing. In this context, studies involving unconventional or “innovative” extraction methods have emerged as a strategic approach to preserve the quality of the extracted material (whether by-product or biomass) by aligning with the core principles of green chemistry and the expansion of sustainable production chains. This approach promotes both raw material integrity and the protection of human and environmental health. These efforts contribute to a virtuous cycle of technological innovation and environmentally sound practices. This review focuses on how ultrasound-assisted extraction affects the quality of plant-derived materials, particularly Brazil nut oil. The article compiles data published over the last five years (2020–2025), following the PRISMA methodology. Recent studies highlight the synergistic potential of ultrasound as a green technology for isolating Brazil nut oil, offering enhanced nutritional and functional properties. This aligns with the growing demand for healthier food products obtained through sustainable industrial processes and presents opportunities for diverse applications across several industry sectors. Full article

(This article belongs to the Special Issue Extraction and Characterization of Food Components)

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12 pages, 2841 KiB

Open AccessArticle

Extraction of Rubidium and Cesium Ions by Adsorption–Flotation Separation in Titanosilicate-Hexadecyltrimethylammonium Bromide System

by Dezhen Fang, Haining Liu, Xiushen Ye, Yanping Wang and Wenjie Han

Separations 2025, 12(7), 181; https://doi.org/10.3390/separations12070181 - 7 Jul 2025

Viewed by 207

Abstract

This study centers on the adsorption–flotation coupling extraction of rubidium (Rb⁺) and cesium (Cs⁺) within a titanium silicate (CTS)–cetyltrimethylammonium bromide (CTAB) system, systematically investigating the impacts of pH, aeration rate, CTAB concentration, and flotation time on the extraction efficiency [...] Read more.

This study centers on the adsorption–flotation coupling extraction of rubidium (Rb⁺) and cesium (Cs⁺) within a titanium silicate (CTS)–cetyltrimethylammonium bromide (CTAB) system, systematically investigating the impacts of pH, aeration rate, CTAB concentration, and flotation time on the extraction efficiency of these elements. Single-factor experiments revealed that the optimal flotation efficiency was achieved when the pH ranged from 6 to 10, the aeration rate was set at 1000 r/min, the CTAB concentration was 0.2 mmol/L, and the flotation duration was 18 min. Under these conditions, the adsorption capacities for Rb⁺ and Cs⁺ were recorded as 128.32 mg/g and 185.47 mg/g, respectively. Employing the response surface optimization method to analyze the interactive effects of these four factors, we found that their order of significance was as follows: pH > aeration rate > CTAB concentration > flotation time. The optimized parameters were determined as pH 8.64, bubble formation rate 1121 r/min, CTAB concentration 0.26 mmol/L, and flotation time 18.47 min. Under these refined conditions, the flotation efficiency for both CTS–Rb and CTS–Cs surpassed any single-factor experiment scenario, with the flotation efficiencies for Rb⁺ and Cs⁺ reaching 95.05% and 94.82%, respectively. This methodology effectively extracts Rb⁺ and Cs⁺ from low-concentration liquid systems, while addressing the challenges of solid–liquid separation for powdered adsorption materials. It holds significant theoretical and practical reference value for enhancing the separation processes of low-grade valuable components and boosting overall separation performance. Full article

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

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26 pages, 7085 KiB

Open AccessReview

Advances in Electrolytic Manganese Residue: Harmless Treatment and Comprehensive Utilization

by Weijian Yu, Xiaoya Li, Wenting Xu, Qingjun Guan, Fujia Zhou, Jiani Zhang, Li Wang, Yanxiu Wang and Honghu Tang

Separations 2025, 12(7), 180; https://doi.org/10.3390/separations12070180 - 7 Jul 2025

Viewed by 236

Abstract

Electrolytic manganese residue (EMR) is a byproduct of electrolytic manganese production, rich in soluble pollutants such as manganese and ammonia nitrogen. Traditional stockpiling methods result in contaminant leaching and water pollution, threatening ecosystems. Meanwhile, EMR has significant resource-recovery potential. This paper systematically reviews [...] Read more.

Electrolytic manganese residue (EMR) is a byproduct of electrolytic manganese production, rich in soluble pollutants such as manganese and ammonia nitrogen. Traditional stockpiling methods result in contaminant leaching and water pollution, threatening ecosystems. Meanwhile, EMR has significant resource-recovery potential. This paper systematically reviews the harmless process and resource technology of EMR, efficiency bottlenecks, and the current status of industrial applications. The mechanisms of chemical leaching, precipitation, solidification, roasting, electrochemistry, and microorganisms were analyzed. Among these, electrochemical purification stands out for its efficiency and environmental benefits, positioning it as a promising option for broad industrial use. The mechanisms of chemical leaching, precipitation, solidification, roasting, electrochemistry, and microorganisms were analyzed, revealing the complementarity between building materials and chemical materials (microcrystalline glass) in scale and high-value-added production. But the lack of impurity separation accuracy and market standards restricts its promotion. Finally, it proposes future directions for EMR resource utilization based on practical and economic considerations. Full article

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

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14 pages, 4623 KiB

Open AccessArticle

Effective Removal of Microplastics Using a Process of Ozonation Followed by Flocculation with Aluminum Sulfate and Polyacrylamide

by Jie Wang, Meiyi Hu, Ziyi Zhang and Shaoping Tong

Separations 2025, 12(7), 179; https://doi.org/10.3390/separations12070179 - 7 Jul 2025

Viewed by 258

Abstract

The widespread use of plastics in our daily life has caused many health problems. Conventional water treatment processes have low efficiency in the removal of microplastics from water. In this work, we investigated the efficiency of ozonation pretreatment followed by flocculation to remove [...] Read more.

The widespread use of plastics in our daily life has caused many health problems. Conventional water treatment processes have low efficiency in the removal of microplastics from water. In this work, we investigated the efficiency of ozonation pretreatment followed by flocculation to remove microplastics from water. After the ozonation pretreatment, it was found that microplastic removal could be significantly enhanced by flocculation from 40% to 91%. The characterization results show that the ozonation-pretreated microplastics had rougher surfaces and larger amounts of surface hydroxyl groups and carbonyls, which might be responsible for their increased removal. However, there was still a small amount of microplastics that had not been removed. They floated on the surface of the solution and could not be effectively oxidized by ozone, thus not changing their surface properties. This further confirms the importance of hydroxyl groups. Full article

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12 pages, 23410 KiB

Open AccessArticle

Recycling and Separation of Valuable Metals from Spent Cathode Sheets by Single-Step Electrochemical Strategy

by Neng Wei, Yaqun He, Guangwen Zhang, Jiahao Li and Fengbin Zhang

Separations 2025, 12(7), 178; https://doi.org/10.3390/separations12070178 - 5 Jul 2025

Viewed by 177

Abstract

The conventional spent lithium-ion batteries (LIBs) recycling method suffers from complex processes and excessive chemical consumption. Hence, this study proposes an electrochemical strategy for achieving reductant-free leaching of high-valence transition metals and efficient separation of valuable components from spent cathode sheets (CSs). An [...] Read more.

The conventional spent lithium-ion batteries (LIBs) recycling method suffers from complex processes and excessive chemical consumption. Hence, this study proposes an electrochemical strategy for achieving reductant-free leaching of high-valence transition metals and efficient separation of valuable components from spent cathode sheets (CSs). An innovatively designed sandwich-structured electrochemical reactor achieved efficient reductive dissolution of cathode materials (CMs) while maintaining the structural integrity of aluminum (Al) foils in a dilute sulfuric acid system. Optimized current enabled leaching efficiencies exceeding 93% for lithium (Li), cobalt (Co), manganese (Mn), and nickel (Ni), with 88% metallic Al foil recovery via cathodic protection. Multi-scale characterization systematically elucidated metal valence evolution and interfacial reaction mechanisms, validating the technology’s tripartite innovation: simultaneous high metal extraction efficiency, high value-added Al foil recovery, and organic removal through single-step electrochemical treatment. The process synergized the dissolution of CM particles and hydrogen bubble-induced physical liberation to achieve clean separation of polyvinylidene difluoride (PVDF) and carbon black (CB) layers from Al foil substrates. This method eliminates crushing pretreatment, high-temperature reduction, and any other reductant consumption, establishing an environmentally friendly and efficient method of comprehensive recycling of battery materials. Full article

(This article belongs to the Special Issue Innovative Separation Techniques for Sustainable Recycling of Solid Waste)

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15 pages, 1995 KiB

Open AccessArticle

Thermodynamic Characteristics of the Ion-Exchange Process Involving REMs of the Light Group

by Olga V. Cheremisina, Maria A. Ponomareva, Yulia A. Mashukova, Nina A. Nasonova and Maria D. Burtseva

Separations 2025, 12(7), 177; https://doi.org/10.3390/separations12070177 - 4 Jul 2025

Viewed by 172

Abstract

Rare earth metals (REMs) are vital for high-tech industries, but their extraction from secondary sources is challenging due to environmental and technical constraints. This study investigates the ion-exchange extraction of light REMs (neodymium, praseodymium, and samarium) from sulfuric and phosphoric acid solutions, modeling [...] Read more.

Rare earth metals (REMs) are vital for high-tech industries, but their extraction from secondary sources is challenging due to environmental and technical constraints. This study investigates the ion-exchange extraction of light REMs (neodymium, praseodymium, and samarium) from sulfuric and phosphoric acid solutions, modeling industrial leachates from apatite concentrates and phosphogypsum. The study considers the use of anion- and cation-exchange resins with different functional groups for efficient and environmentally safe REM separation. Experimental sorption isotherms were obtained under static conditions at 298 K and analyzed using a thermodynamic model based on the linearization of the mass action equation. Equilibrium constants and Gibbs energy were calculated, which reveals the spontaneity of the processes. Cation-exchange resins demonstrated high selectivity towards individual REMs, while anion-exchange resins were suitable for group extraction. Infrared spectral analysis confirmed the presence of sulfate and phosphate complexes in the resin matrix, clarifying the ion-exchange mechanisms. Thermal effect measurements indicated exothermic sorption on anion-exchange resins with negative entropy and endothermic sorption on cation-exchange resins with positive entropy. The findings highlight the potential of ion-exchange resins for selective and sustainable REM recovery, offering a safer alternative to liquid extraction and enabling the valorization of industrial wastes like phosphogypsum for resource recovery. Full article

(This article belongs to the Special Issue Recent Advances in Rare Earth Separation and Extraction)

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18 pages, 605 KiB

Open AccessArticle

Validation of a Method for the Determination of Artificial Sweeteners and Caffeine in Soft Drinks: The Impact of Regression Function Selection on Quantification Limits Considering Trueness and Precision

by Natàlia Hernández and Juan M. Sanchez

Separations 2025, 12(7), 176; https://doi.org/10.3390/separations12070176 - 2 Jul 2025

Viewed by 141

Abstract

Background: Method quantification limits are typically determined by measuring variability at blank level only, without accounting for the uncertainties associated with the parameters of the calibration function applied. Methods: A method for the determination of artificial sweeteners and caffeine in soft drinks was [...] Read more.

Background: Method quantification limits are typically determined by measuring variability at blank level only, without accounting for the uncertainties associated with the parameters of the calibration function applied. Methods: A method for the determination of artificial sweeteners and caffeine in soft drinks was validated. The effect of chosen regression function on quantification limits was assessed, considering both trueness and precision. Results: The validated method exhibited heteroscedasticity for all analytes, which is common in experimental methods. A linear response was observed within the working range for sweeteners, while a quadratic regression was required for caffeine. Due to the heteroscedasticity nature of the responses, weighted regressions were necessary to obtain the lowest method quantification limits, allowing for accurate (i.e., unbiased and precise) estimates at the lower end of the calibration range. Under weighted conditions, the regression equations obtained, with an upper range set at 600 mg·L⁻¹, were as follows: y = 3.9 + 58.9x for acesulfame K; y = 0.8 + 185.1x for saccharin; y = 3.5 + 43.3x for aspartame, and y = −7 + 159x − 0.242x² for caffeine. The method quantification limits determined using weighted regressions were 2 mg·L⁻¹ for each analyte, whereas these limits increased to 20 mg·L⁻¹ when non-weighted regressions were applied. Conclusions: The choice of regression function for transforming instrumental signals into analyte concentrations significantly affects the determination of quantification limits, owing to the inherent heteroscedasticity of analytical and bioanalytical calibrations. Weighted regressions are essential for producing accurate estimates at lower concentration levels. Applying weighted regression in the context of heteroscedastic calibrations can lead to quantification limits that are more than 10 times lower than unweighted approaches. Full article

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13 pages, 988 KiB

Open AccessArticle

Extraction, Isolation, and Purification of Furanocoumarins from Invasive Heracleum sosnowskyi

by Vida Vickackaite, Karina Pilaityte and Vilius Poskus

Separations 2025, 12(7), 175; https://doi.org/10.3390/separations12070175 - 1 Jul 2025

Viewed by 259

Abstract

Heracleum sosnowskyi Manden. (Sosnowsky’s hogweed), originally introduced to Central and Eastern Europe as a fodder crop, has become a highly invasive species due to its ecological adaptability, high reproductive capacity, and efficient seed dispersal. Despite its negative impact on native flora and its [...] Read more.

Heracleum sosnowskyi Manden. (Sosnowsky’s hogweed), originally introduced to Central and Eastern Europe as a fodder crop, has become a highly invasive species due to its ecological adaptability, high reproductive capacity, and efficient seed dispersal. Despite its negative impact on native flora and its health risks to humans and animals, the species also represents a valuable source of biologically active compounds. In this study, we demonstrate that the leaves of H. sosnowskyi contain substantial amounts of furanocoumarins—phototoxic compounds with notable therapeutic potential, particularly as natural photosensitizers in anticancer therapies. To extract furanocoumarins from H. sosnowskyi, microwave-assisted extraction (MAE) was employed, with optimization of key parameters including extraction solvent (hexane), temperature (70 °C), extraction time (10 min), and solvent-to-solid ratio (20:1). Four major compounds—angelicin (2.3 mg/g), psoralen (0.15 mg/g), methoxsalen (0.76 mg/g), and bergapten (3.14 mg/g)—were identified and quantified using gas chromatography–mass spectrometry and gas chromatography with flame ionization detection. To purify the extract and selectively isolate the target compounds, a solid-phase extraction method was developed using a Strata Eco-Screen sorbent and stepwise elution with a hexane–acetone mixture. As a result, pure angelicin, pure methoxsalen, and various mixtures of the furanocoumarins were obtained. These findings highlight the potential of H. sosnowskyi as a sustainable source of furanocoumarins for pharmaceutical applications. Full article

(This article belongs to the Special Issue Sample Preparation and Chromatographic Analysis of Environmental Samples)

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15 pages, 2034 KiB

Open AccessArticle

Heterogeneous Interactions During Bubble–Oil Droplet Contact in Water

by Tao Yang, Hao Xiao, Chunyu Jiang, Ming Ma, Guangwen Zhang, Chun Wang, Yi Zheng and Xiangdi Zhao

Separations 2025, 12(7), 174; https://doi.org/10.3390/separations12070174 - 29 Jun 2025

Viewed by 345

Abstract

Oily wastewater is extensively generated during the petroleum extraction and refining processes, as crude oil production water and from the effluent systems in petrochemical enterprises. The discharge standards for such wastewater are stringent, with the Oslo–Paris Convention stipulating that the oil content must [...] Read more.

Oily wastewater is extensively generated during the petroleum extraction and refining processes, as crude oil production water and from the effluent systems in petrochemical enterprises. The discharge standards for such wastewater are stringent, with the Oslo–Paris Convention stipulating that the oil content must be below 30 mg/L for permissible discharge. Flotation, a conventional oil–water separation method, relies on the collision and adhesion of rising bubbles with oil droplets in water to form low-density aggregates that float to the surface for separation. The collision and adhesion mechanisms between bubbles and oil droplets are fundamental to this process. However, systematic studies on their interactions remain scarce. This study employs the extended Derjaguin–Landau–Verwey–Overbeek theory to analyze the three mechanical interactions during the collision–adhesion process theoretically and investigates the heterogeneous interaction dynamics experimentally. Furthermore, given the diverse liquid-phase environments of oily wastewater, the effects of salinity, pH, and surfactant concentration are decoupled and individually explored to clarify their underlying mechanisms. Finally, a solution is proposed to enhance the flotation efficiency fundamentally. This work systematically elucidates the influence of liquid-phase environments on the adhesion behavior for the first time through the unification of theoretical and experimental approaches. The findings provide critical insights for advancing flotation theory and guiding the development of novel coagulants. Full article

(This article belongs to the Section Separation Engineering)

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13 pages, 1017 KiB

Open AccessArticle

Separation of Exhaust Gas Pollutants from Urea Prilling Process with Gasified Biochar for Slow-Release Fertilizer: Adsorption Characteristics, Process Improvement, and Economic Assessment

by Tong Lou, Bingtao Zhao, Zixuan Zhang, Mengqi Wang, Yanli Mao, Baoming Chen, Xinwei Guo, Tuo Zhou and Fengcui Li

Separations 2025, 12(7), 173; https://doi.org/10.3390/separations12070173 - 29 Jun 2025

Viewed by 310

Abstract

To address severe ammonia gas and dust pollution coupled with resource waste in exhaust gases from urea prilling towers, a production process for gasified biochar-based slow-release fertilizer is proposed to achieve resource recovery of exhaust pollutants. Through phosphoric acid impregnation modification applied to [...] Read more.

To address severe ammonia gas and dust pollution coupled with resource waste in exhaust gases from urea prilling towers, a production process for gasified biochar-based slow-release fertilizer is proposed to achieve resource recovery of exhaust pollutants. Through phosphoric acid impregnation modification applied to gasified biochar, its ammonia gas adsorption capacity was significantly enhanced, with saturated adsorption capacity increasing from 0.61 mg/g (unmodified) to 32 mg/g. Coupled with the tower-top bag filter, the modified biochar combines with ammonia gas and urea dust in exhaust gases, subsequently forming biochar-based slow-release fertilizer through dehydration and granulation processes. Material balance analysis demonstrates that a single 400,000-ton/year urea prilling tower achieves a daily fertilizer production capacity of 55 tons, with 18% active ingredient content. The nitrogen content can be upgraded to national standards through urea supplementation. Economic analysis demonstrates a total capital investment of USD1.2 million, with an annual net profit of USD0.88 million and a static payback period of 1.36 years. This process not only achieves ammonia gas emission reduction but also converts waste biochar into high-value fertilizer. It displays dual advantages of environmental benefits and economic feasibility and provides an innovative solution for resource utilization of the exhaust gases from the urea prilling process. Full article

(This article belongs to the Section Environmental Separations)

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22 pages, 4877 KiB

Open AccessArticle

Sponge-like Modified White-Rot Fungi Adsorbent for Rapid Removal of Pb(II) and Cd(II) from Solution: Selective Performance and Mechanistic Insights

by Chunxiao Wang, Zhirong Chen, Nana Wang, Jianqiao Wang, Runshen He, Yu Chen, Haerfosai Nuhu, Hang Chen, Zhixuan Lin, Minqi Fan and Mingdong Chang

Separations 2025, 12(7), 172; https://doi.org/10.3390/separations12070172 - 28 Jun 2025

Viewed by 317

Abstract

Heavy metal pollution, especially from Pb(II) and Cd(II), poses significant risks due to its persistence and bioaccumulation potential. Traditional removal methods face challenges like high costs and secondary pollution. This study developed a novel three-dimensional porous adsorbent XBS, derived from xanthate-modified Phanerochaete sordida [...] Read more.

Heavy metal pollution, especially from Pb(II) and Cd(II), poses significant risks due to its persistence and bioaccumulation potential. Traditional removal methods face challenges like high costs and secondary pollution. This study developed a novel three-dimensional porous adsorbent XBS, derived from xanthate-modified Phanerochaete sordida YK-624 (a white-rot fungus), for the rapid and efficient removal of Pb(II) and Cd(II) from wastewater. Characterization showed that XBS has a sponge-like structure with abundant functional groups, significantly enhancing its adsorption capacity and kinetics. XBS achieved 96% Pb(II) and 32% Cd(II) removal within 1 min at a 0.25 g/L dose, reaching over 95% of the maximum adsorption capacity within 30 min for Pb(II) and 240 min for Cd(II). The maximum capacities were 224.72 mg/g for Pb(II) and 82.99 mg/g for Cd(II). Kinetic and thermodynamic analyses indicated a chemisorption-driven process, which was both endothermic and spontaneous. XBS exhibited high selectivity for Pb(II) over Cd(II) and other metals (Tl(I), Cu(II)), attributed to stronger covalent interactions with sulfur- and nitrogen-containing groups. Mechanistic analyses (XRD, FTIR, and XPS) revealed that removal occurs via ion exchange, complexation, and precipitation, forming stable compounds like PbS/CdS and PbCO₃/CdCO₃. Given its cost-effectiveness, scalability, and high efficiency, XBS represents a promising adsorbent for heavy metal remediation, particularly in Pb(II)-contaminated wastewater treatment applications. Full article

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13 pages, 1434 KiB

Open AccessArticle

Simultaneous Determination of 23 Trans Fatty Acids in Common Edible Oils by Gas Chromatography-Mass Spectrometry

by Yanping Cao, Xia Li, Kun Wang, Xianpeng Wu, Jie Zhang and Fengen Wang

Separations 2025, 12(7), 171; https://doi.org/10.3390/separations12070171 - 28 Jun 2025

Viewed by 256

Abstract

Trans fatty acids (TFAs) pose significant health risks, including cardiovascular disease and metabolic disorders. However, the lack of high-resolution, high-sensitivity, and high-throughput quantitative methods for TFA analysis has led to fragmented data on TFA content in edible oils, which constrains research on the [...] Read more.

Trans fatty acids (TFAs) pose significant health risks, including cardiovascular disease and metabolic disorders. However, the lack of high-resolution, high-sensitivity, and high-throughput quantitative methods for TFA analysis has led to fragmented data on TFA content in edible oils, which constrains research on the quality assessment of edible oils. In this study, we developed a high-resolution and high-sensitivity gas chromatography-mass spectrometry method to simultaneously determine 23 TFA isomers. The method validation demonstrated good sensitivity, linearity, accuracy, and precision. Based on the proposed method, we analyzed 170 samples of 11 common edible oils, establishing a comprehensive TFA profile for each type. Ruminant fats (beef tallow, mutton tallow, butter) had high TFA levels (0.8–4.8 g/100 g), dominated by vaccenic acid (C18:1 t11) and conjugated linoleic acid, while vegetable oils (soybean, corn, peanut and sesame oil) exhibited lower concentrations (0.5–2.2 g/100 g), especially monounsaturated TFAs. Particularly, soybean oil was rich in C18:3 isomers, while shortening presented the closest similarity to sesame oil. Cluster analysis distinguished oils by TFA composition, highlighting low-TFA clusters (sunflower oil, pork lard, cream). In conclusion, the high-resolution, high-sensitivity, and high-throughput TFA quantification method developed in this study provides technical support for establishing characteristic TFA profiles in edible oils, while offering data support to further quality assessment. Full article

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15 pages, 2912 KiB

Open AccessArticle

Profiling the Differential Distribution of Ginsenosides Across Ginseng Tissues Using High-Resolution Mass Spectrometry

by Hang Xu, Zheng Li, Chong Liu, Yukun Wang, Siwei Qiao and Hao Zhang

Separations 2025, 12(7), 170; https://doi.org/10.3390/separations12070170 - 26 Jun 2025

Viewed by 293

Abstract

This study investigates the compositional characteristics and quantitative differences of ginsenosides across various ginseng tissues, with a particular focus on the specific accumulation patterns of malonyl ginsenosides. Five tissue samples—ginseng fruit (F), leaf (L), taproot (TR), lateral root (LR), and fibrous root (FR)—were [...] Read more.

This study investigates the compositional characteristics and quantitative differences of ginsenosides across various ginseng tissues, with a particular focus on the specific accumulation patterns of malonyl ginsenosides. Five tissue samples—ginseng fruit (F), leaf (L), taproot (TR), lateral root (LR), and fibrous root (FR)—were analyzed using Orbitrap Fusion high-resolution liquid chromatography–mass spectrometry. A total of 413 ginsenosides, including 33 standards, were identified, encompassing 172 protopanaxadiol (PPD)-type, 188 protopanaxatriol (PPT)-type, 14 oleanolic acid (OA)-type, and 12 ocotillol (OT)-type ginsenosides, of which 160 were malonyl ginsenosides. Statistical analysis revealed significant variations in the relative content per unit mass of malonyl ginsenosides across tissues, with the highest levels in fibrous roots, followed by fruits, lateral roots, leaves, and taproots. Distinct tissue-specific differences in malonyl ginsenoside types and quantities were observed: fruits exhibited 51 malonyl ginsenosides with significantly higher levels, compared to 8, 14, and 17 in lateral roots, fibrous roots, and leaves, whereas TR showed no significant enrichment. This study elucidates the diversity and unique distribution of malonyl ginsenosides in ginseng roots, leaves, and fruits, providing a valuable basis for the targeted selection of tissues with high malonyl ginsenoside content and the development of functional food and medicinal products. Full article

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20 pages, 4330 KiB

Open AccessArticle

Extraction of Terpenoids from Pine Needle Biomass Using Dimethyl Ether

by Gary S. Groenewold, Christopher Orme, Caleb Stetson, Rebecca M. Brown, Lynn M. Wendt and Aaron D. Wilson

Separations 2025, 12(7), 169; https://doi.org/10.3390/separations12070169 - 26 Jun 2025

Viewed by 343

Abstract

Pine needles are an industrial feedstock for extracts used in a variety of applications, but conventional extraction methods often result in a degradation of the terpenoid compounds that naturally occur in loblolly pine (Pinus taeda). Separation of these compounds from pine [...] Read more.

Pine needles are an industrial feedstock for extracts used in a variety of applications, but conventional extraction methods often result in a degradation of the terpenoid compounds that naturally occur in loblolly pine (Pinus taeda). Separation of these compounds from pine biomass is an energy-intensive operation, typically requiring a significant input of thermal energy. An alternative separation approach with potential energy savings is extraction with a condensable gas, namely, dimethyl ether. Biomass materials are exposed to liquid dimethyl ether under pressure, which mobilizes the organics. The extract is then separated from the insoluble pine matter, and dimethyl ether is volatilized away from the separated organic species. A variety of terpene derivatives were extracted from pine needle biomass using this approach, including monoterpenes, sesquiterpenes, and related oxygenates, which were identified using two-dimensional gas chromatography/mass spectrometry. Additionally, the dimethyl ether-treated needles resemble needles subjected to low-temperature drying, whereas needles treated with a high-temperature drying method appear to have shrunken structures. The results suggest that dimethyl ether extraction has significant potential for separating valuable organics from complex matrices without the application of thermal energy during treatment. Full article

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

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Open AccessArticle

Content Determination and Impurity Profiling of Compound Glycyrrhizin Tablets by Ion-Pair High-Performance Liquid Chromatography, Coupled with Corona-Charged Aerosol Detector

by Limin Zuo, Wenling Su, Yongsheng Gu, Xiaodan Qiu, Ting Zhao, Xiaofang Lian, Huiyi Liu, Qingying Jia, Ruifang Zheng and Guangzhi Shan

Separations 2025, 12(7), 168; https://doi.org/10.3390/separations12070168 - 25 Jun 2025

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Abstract

Compound Glycyrrhizin tablets (CGTs) are a combination of glycyrrhizin, glycine and methionine. Glycine and methionine have relatively high polarity and lack chromophore; therefore, it is difficult to simultaneously determine the various components using traditional reversed-phase chromatography and ultraviolet detectors. In addition, it is [...] Read more.

Compound Glycyrrhizin tablets (CGTs) are a combination of glycyrrhizin, glycine and methionine. Glycine and methionine have relatively high polarity and lack chromophore; therefore, it is difficult to simultaneously determine the various components using traditional reversed-phase chromatography and ultraviolet detectors. In addition, it is even more challenging to obtain a comprehensive and systematic impurity profiling for the CGTs. In this study, an ion-pair high-performance liquid chromatography (HPLC)–charged aerosol detection (CAD) method was established to determine the content of glycyrrhizin, glycine and methionine. The impurities of CGTs were also identified using mass spectrometry. By optimizing the content of trifluoroacetic acid (TFA) in the mobile phase and optimizing the CAD parameter settings, the developed method was verified in accordance with the guidelines outlined in ICH Q2 (R2). The results indicated that the method demonstrated high accuracy and sensitivity. Glycine, methionine and glycyrrhizin all showed a good linear relationship within the labeled range of 50–200%, and the average recoveries of the three components were 97.62–100.6%. The impurity detection was quantified via the principal component control method. The limit of detection (LOD) method showed an equivalent to 0.05% of the glycyrrhizin in CGTs, approximately 12.5 ng. The ion-pair HPLC–CAD method developed in this study simultaneously determined the content of the main component and the impurities of CGTs, without necessitating derivatization. This has provided a research basis for further improving the quality standards of CGTs. Full article

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Separations, Volume 12, Issue 7 (July 2025) – 18 articles

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