Separations

19 pages, 2985 KB

Open AccessArticle

Adsorption of Platinum from Alkaline Glycine–Cyanide Solutions Using Activated Carbon: Leachates, Water, and Waste Treatment Applications

by Caroline Rubina Acuna, Elsayed A. Oraby, G. A. Bezuidenhout, Chau Chun Beh and Jacques J. Eksteen

Separations 2025, 12(10), 284; https://doi.org/10.3390/separations12100284 - 13 Oct 2025

Abstract

Platinum’s unique properties, such as its high resistance to corrosion and high temperatures, are driving an increased use in modern technologies and advanced chemistry. However, the World Platinum Investment Council has projected, for the third consecutive year, a global deficit of platinum for [...] Read more.

Platinum’s unique properties, such as its high resistance to corrosion and high temperatures, are driving an increased use in modern technologies and advanced chemistry. However, the World Platinum Investment Council has projected, for the third consecutive year, a global deficit of platinum for 2025 and a negative forecast until 2029, highlighting the need for the development of new metallurgical methodologies to recover platinum but also to recycle product containing it. The use of alkaline amino acid (glycine) promises a highly selective and more environmentally friendly recovery methodology. Over the Platinum Group Metals, recovery studies have been performed only on palladium, but no published literature over platinum was found. This study investigated the feasibility of platinum adsorption from alkaline glycine solutions under various operational conditions using activated carbon. Results are demonstrating that platinum can be successfully recovered under the effects tested: 92.37–97.93% (carbon dosage), 70.00–95.72% (temperature), 94.08–97.39% (pH), 95.16–96.23% (platinum concentration), 95.72–96.53% (glycine concentration), and 95.72–97.12% (cyanide concentration). The scientific significance of this study lies in the confirmation for the potential use of a more environmentally friendly approach to recover platinum as opposed to the current cyanide and acidic chloride system. Full article

(This article belongs to the Special Issue Applications of Adsorbent Materials in Water and Wastewater Treatment)

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28 pages, 1877 KB

Open AccessReview

Functionalized Carbon-Based Materials for Uranium Extraction: A Review

by Maqbool Hussain, Liang Zhao, Xusheng Zhang, Chen Yang, Yi Cui, Zhisheng Yu and Jianzhong Zheng

Separations 2025, 12(10), 283; https://doi.org/10.3390/separations12100283 - 13 Oct 2025

Abstract

The development of effective materials for uranium extraction from seawater is vital for advancing sustainable energy solutions. However, the efficient recovery of uranium from seawater presents significant challenges due to its extremely low concentration, the presence of competing ions, and the complex marine [...] Read more.

The development of effective materials for uranium extraction from seawater is vital for advancing sustainable energy solutions. However, the efficient recovery of uranium from seawater presents significant challenges due to its extremely low concentration, the presence of competing ions, and the complex marine environment. To address these issues, various materials such as inorganic and organic sorbents, chelating resins, nanostructured sorbents, and composite materials have been explored. More recently, the functionalization of carbon-based materials for enhanced adsorption properties has attracted much interest because of their high specific surface area, excellent chemical and thermal stability, and tunable porosity. These materials include activated carbon, graphene oxide, biochar, carbon cloths, carbon nanotubes, and carbon aerogels. The enhancement of carbonaceous materials is typically achieved through surface functionalization with chelating groups and the synthesis of composite materials that integrate other high-performance sorbents. This review aims to summarize the work of these functionalized carbon materials, focusing on their adsorption capacity, selectivity, and durability for uranium adsorption. This is followed by a discussion on the binding mechanisms of uranium with major chelating functional groups grafted on carbonaceous sorbents. Finally, an outlook for future research is suggested. We hope that this review will be helpful to researchers engaged in related studies. Full article

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20 pages, 1440 KB

Open AccessArticle

Phenolic Compounds in Plant-Based Milk Alternatives from the Greek Market

by Velisaria-Eleni Gerogianni, Christiana Mantzourani, Maria A. Theodoropoulou, Antonia Chiou and Maroula G. Kokotou

Separations 2025, 12(10), 282; https://doi.org/10.3390/separations12100282 - 11 Oct 2025

Abstract

Plant-based milk alternatives (PBMAs) are plant-based fluid products that are marketed as substitutes for regular milk. The nutrient composition of PBMA products can vary widely, depending on the plant source, processing methods, potential additives, etc., and in recent years, considerable research effort has [...] Read more.

Plant-based milk alternatives (PBMAs) are plant-based fluid products that are marketed as substitutes for regular milk. The nutrient composition of PBMA products can vary widely, depending on the plant source, processing methods, potential additives, etc., and in recent years, considerable research effort has been devoted to the exploration of the nutritional content of PBMAs, which are increasingly consumed worldwide. In the present study, an established UHPLC–Orbitrap MS method was employed for the extensive characterization of phenolic compounds in PBMAs available in the Greek market. Twenty-eight PBMAs were studied, including a variety of almond-, soy-, coconut-, oat-, walnut-, and rice-based products. In almond-based milk products, low total concentrations and a broad distribution across compound classes were observed, with trans-chlorogenic acid and neochlorogenic acid being the most abundant constituents, whereas coconut-based milk samples were generally not rich in phenolic compounds. In soy-based milk samples, the presence of isoflavones including daidzein, genistein, and glycitein was uniquely detected, while oat-based products were the samples richer in phenolic content, in particular for hydroxycinnamic acids, such as trans-chlorogenic acid and neochlorogenic acid. In addition, a suspect screening approach, using Exactive Plus Orbitrap, enabled the exploration and semi-quantification of three avenanthramides (A, B, C) in the studied oat-based milk samples and six isoflavonoids, namely daidzein and genistein derivatives, in soy-based milk. Such compounds are known for their antioxidant and anti-inflammatory properties, and their occurrence in PBMAs highlights the potential health-promoting effects of these dairy alternatives. Full article

(This article belongs to the Special Issue Extraction, Purification and Functional Substances of Natural Products and Plants)

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12 pages, 2700 KB

Open AccessArticle

Study on the Emission Characteristics of Fine Particulate Matter in the White Mud Desulfurization Process

by Changqing Wang, Yongchao Feng, Xin Wang, Rongliang Xie, Guanglei Li, Li Yu and Lingxiao Zhan

Separations 2025, 12(10), 281; https://doi.org/10.3390/separations12100281 - 11 Oct 2025

Abstract

White mud is a promising desulfurizing agent, but the risk of fine particulate emissions exists during its application. This study investigated the fine particulate emissions in the white mud desulfurization process and analyzed the effects of process parameters, including gas-to-liquid ratio, empty tower [...] Read more.

White mud is a promising desulfurizing agent, but the risk of fine particulate emissions exists during its application. This study investigated the fine particulate emissions in the white mud desulfurization process and analyzed the effects of process parameters, including gas-to-liquid ratio, empty tower gas velocity, and slurry concentration, on particulate emissions. The results showed that white mud desulfurization achieved effective SO₂ removal, with a removal efficiency ranging from 93.5% to 95.8%. However, the emission of fine particulates was found to be a significant environmental concern. At a slurry concentration of 15%, the fine particulate number concentration was found to be 5.9 × 10⁶ particles/cm³, with a mass concentration of approximately 43.2 mg/m³. The study further revealed that increasing the empty tower gas velocity from 2.5 m/s to 4.5 m/s also significantly increased particulate emissions. Similarly, increasing the gas-to-liquid ratio from 10 L/m³ to 15 L/m³ led to a 25.5% increase in the fine particulate number concentration. These changes were attributed to the increased atomization of fine droplets and the enhanced gas–liquid relative movement, which facilitated the entrainment of more fine particulates into the flue gas. While improving the slurry concentration led to better desulfurization efficiency, these adjustments also resulted in higher fine particulate emissions. Therefore, optimizing process parameters to balance desulfurization efficiency and fine particulate emission control was crucial for practical applications. Full article

(This article belongs to the Special Issue Application of Advanced Materials and Technologies in the Separation and Adsorption)

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18 pages, 1969 KB

Open AccessReview

Artemisia frigida Willd.: Advances in Traditional Uses, Phytochemical Constituents, Extraction and Separation Methods, and Pharmacological Activities

by Wei Tian, Mengjie Zhang, Tongcun Zhang, Xianglong Li, Haiying Zhang and Xiumei Li

Separations 2025, 12(10), 280; https://doi.org/10.3390/separations12100280 - 11 Oct 2025

Abstract

Artemisia frigida Willd. (A. frigida), a traditional medicinal herb widely distributed in northern China, Mongolia, and Siberia, has garnered increasing scientific interest due to its diverse phytochemical profile and extensive pharmacological potential. Modern studies have identified a wide range of bioactive [...] Read more.

Artemisia frigida Willd. (A. frigida), a traditional medicinal herb widely distributed in northern China, Mongolia, and Siberia, has garnered increasing scientific interest due to its diverse phytochemical profile and extensive pharmacological potential. Modern studies have identified a wide range of bioactive compounds in A. frigida, including flavonoids, sesquiterpene lactones and phenolic acids. These compounds exhibit various biological activities, such as antioxidant, anti-inflammatory, anticancer, and antimicrobial effects. This review systematically summarizes the research progress on the chemical constituents of A. frigida and their extraction and separation methods, including solvent extraction, ultrasonic-assisted extraction, macroporous resin adsorption, and chromatography-based techniques. By integrating traditional knowledge with modern pharmacological evidence, this review provides a scientific foundation for the further development and utilization of A. frigida in functional food, pharmaceuticals, and ethnomedicine. Full article

(This article belongs to the Special Issue Extraction, Purification and Functional Substances of Natural Products and Plants)

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11 pages, 1808 KB

Open AccessArticle

Ultrasound-Assisted Extraction Optimization and Flash Chromatography Fractionation of Punicalagin from Pomegranate Peel (Punica granatum L.)

by Erick M. Raya-Morquecho, Pedro Aguilar-Zarate, Leonardo Sepúlveda, Mariela R. Michel, Anna Iliná, Cristóbal N. Aguilar and Juan A. Ascacio-Valdés

Separations 2025, 12(10), 279; https://doi.org/10.3390/separations12100279 - 11 Oct 2025

Abstract

Background: Pomegranate peel (Punica granatum L.) is a rich source of phenols, particularly ellagitannins, highlighting punicalagin, a bioactive compound with recognized antioxidant potential. However, efficient recovery and purification methods are required to enable its application in food and health-related products. This study [...] Read more.

Background: Pomegranate peel (Punica granatum L.) is a rich source of phenols, particularly ellagitannins, highlighting punicalagin, a bioactive compound with recognized antioxidant potential. However, efficient recovery and purification methods are required to enable its application in food and health-related products. This study aimed to obtain a partially purified fraction of punicalagin from pomegranate peel using optimized extraction and purification strategies. Methods: A Taguchi L9 (3)³ experimental design was employed to optimize ultrasound-assisted extraction, evaluating extraction time (10, 20, 30 min), ethanol concentration (20, 40, 80%), and solid-to-solvent ratio (1:12, 1:14, 1:16). Total polyphenol content was quantified using the Folin–Ciocalteu method. Extracts obtained under optimized conditions were concentrated by rotary evaporation and subjected to semipurification using flash chromatography with Amberlite XAD-16 resin. Subsequently, the fractions were lyophilized and analyzed by HPLC/ESI/MS. Results: The Statistica software determined the optimal conditions for polyphenol extraction (20 min, 40% ethanol, 1:12), with the signal-to-noise (S/N) ratio reaching 88.43 ± 0.66, surpassing the predicted value of 77.42. Flash chromatography yielded four fractions, and HPLC/ESI/MS analysis revealed the presence of ellagitannins in all of them, with fraction number 2 showing the highest relative abundance of punicalagin (89.25%). Conclusions: The combination of ultrasound-assisted extraction and flash chromatography proved effective for obtaining punicalagin-rich fractions from pomegranate peel, supporting its potential for nutraceutical applications. Full article

(This article belongs to the Special Issue Novel Separation Methods for the Analysis of Active and Toxic Components in Food: Second Edition)

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14 pages, 2341 KB

Open AccessArticle

Application of Bio-Based Activated Carbon from Cocoa Husk Waste for High-Efficiency Adsorption in Water Treatment

by Daniela Angelova, Vesislava Toteva and Georgi Georgiev

Separations 2025, 12(10), 278; https://doi.org/10.3390/separations12100278 - 10 Oct 2025

Abstract

This research presents the study of utilizing the cocoa husk biomass waste to obtain active carbon through carbonization method, followed by chemical–thermal activation. The activated carbon (CH) was characterized using BET, SEM–EDX, XPS, and Raman techniques. The obtained material showed a high specific [...] Read more.

This research presents the study of utilizing the cocoa husk biomass waste to obtain active carbon through carbonization method, followed by chemical–thermal activation. The activated carbon (CH) was characterized using BET, SEM–EDX, XPS, and Raman techniques. The obtained material showed a high specific surface area of 1661 m²·g⁻¹, and XPS confirmed the presence of oxygen-containing surface functionalities. The adsorption of reactive dye Drimaren Red K-7B by CH was studied to assess the impact of the initial concentration in water solution, temperature, and contact time. The adsorbent achieved over 90% removal within three minutes at 40 °C. The experimental data for the adsorption of Drimaren Red K-7B using CH showed a good fit with the Dubinin–Radushkevich isotherm and a pseudo-second-order kinetic model. This research offers a promising approach for advancing the circular economy through the obtaining of eco-friendly adsorbents derived from biomass waste, exhibiting high initial adsorption efficiency and rapid uptake kinetics towards reactive dye. Full article

(This article belongs to the Special Issue Application of Adsorption and Separation Technologies in Water Treatment)

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22 pages, 3537 KB

Open AccessArticle

Enhanced Treatment of Swine Farm Wastewater Using an O₃/Fe²⁺/H₂O₂ Process: Optimization and Performance Evaluation via Response Surface Methodology

by Hang Yu, Kexin Tang, Jingqi Li, Linxi Dong, Zuo Tong How, Dongming Wu and Rui Qin

Separations 2025, 12(10), 277; https://doi.org/10.3390/separations12100277 - 10 Oct 2025

Abstract

Biologically treated swine farm wastewater still contains high levels of refractory organics, humic substances and antibiotic residues, posing environmental risks and limiting opportunities for water reuse. Wastewater treatment by ozonation alone suffers from low mass transfer efficiency and selective oxidation. To overcome these [...] Read more.

Biologically treated swine farm wastewater still contains high levels of refractory organics, humic substances and antibiotic residues, posing environmental risks and limiting opportunities for water reuse. Wastewater treatment by ozonation alone suffers from low mass transfer efficiency and selective oxidation. To overcome these limitations, a catalytic ozonation process (O₃/Fe²⁺/H₂O₂) was applied and optimized using Response Surface Methodology (RSM) based on single-factor experiments and Central Composite Design (CCD) for advanced swine farm wastewater treatment. The optimal conditions ([O₃] = 25.0 mg/L, [Fe²⁺] = 25.9 mg/L, [H₂O₂] = 41.1 mg/L) achieved a COD removal of 44.3%, which was 86.8% higher than that of ozonation alone, and increased TOC removal to 29.5%, indicating effective mineralization. Biodegradability (BOD₅/COD) of swine farm wastewater effluent increased from 0.01 to 0.34 after the catalytic ozonation treatment. Humic-like and fulvic-like substances were removed by 93.7% and 95.4%, respectively, and antibiotic degradation was significantly accelerated and enhanced. The synergistic process improved ozone utilization efficiency by 33.1% and removed 53.95% of total phosphorus through Fe³⁺-mediated coprecipitation. These findings demonstrate that with catalytic ozone decomposition and production of hydroxyl radicals, the O₃/Fe²⁺/H₂O₂ system effectively integrates enhanced ozone utilization efficiency, radical synergy, and simultaneous pollutant removal, providing a cost-effective and technically feasible strategy for advanced swine farm wastewater treatment and safe reuse. Full article

(This article belongs to the Special Issue Advanced Treatment Technologies for Emerging Contaminant Control and Resource Utilization)

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18 pages, 2990 KB

Open AccessArticle

CoFeNi-Layered Double Hydroxide Combined Activation of PMS and Ozone for the Degradation of Rhodamine B in Water

by Xiaohan Zhu, Liang Song and Jia Miao

Separations 2025, 12(10), 276; https://doi.org/10.3390/separations12100276 - 9 Oct 2025

Abstract

The development of efficient and sustainable advanced oxidation processes (AOPs) for organic pollutant removal is of great significance for water purification. In this study, a CoFeNi-layered double hydroxide (CoFeNi-LDH) catalyst was synthesized and applied for the simultaneous activation of peroxymonosulfate (PMS) and ozone [...] Read more.

The development of efficient and sustainable advanced oxidation processes (AOPs) for organic pollutant removal is of great significance for water purification. In this study, a CoFeNi-layered double hydroxide (CoFeNi-LDH) catalyst was synthesized and applied for the simultaneous activation of peroxymonosulfate (PMS) and ozone to degrade rhodamine B (RhB) in aqueous solution. The CoFeNi-LDH/PMS/ozone system achieved a remarkable RhB removal efficiency of 95.2 ± 1.2% within 8 min under neutral pH conditions. Systematic parametric studies revealed that synergistic interactions among CoFeNi-LDH, PMS, and ozone contributed to the generation of reactive oxygen species (ROS), primarily sulfate radicals (SO₄^•−) and singlet oxygen (¹O₂), as confirmed by EPR and quenching experiments. Density functional theory (DFT) calculations demonstrated that ozone enhanced PMS adsorption and activation at CoFeNi catalytic sites. The catalyst exhibited robust magnetic recyclability and structural stability after repeated use. This work highlights a synergistic catalytic strategy for PMS/ozone activation, offering an effective and environmentally friendly platform for dye wastewater remediation. Full article

(This article belongs to the Special Issue Photocatalytic Oxidation and Advanced Oxidation Processes for Sustainable Water Treatment)

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10 pages, 937 KB

Open AccessArticle

Investigation of Ethanol and Isopropanol as Greener Alternatives to Acetonitrile in the RP-HPLC Purification of Histone Tail Peptides Bearing Acylation-Type Post-Translational Modifications

by Yordan Hayat and Zeynep Kanlidere

Separations 2025, 12(10), 275; https://doi.org/10.3390/separations12100275 - 9 Oct 2025

Abstract

Background: Histone post-translational modifications (PTMs) play a pivotal role in the regulation of chromatin structure and gene expression, making them key targets in structural and epigenetic research. Synthetic histone peptides bearing specific PTMs are essential tools for elucidating the molecular mechanisms of histone [...] Read more.

Background: Histone post-translational modifications (PTMs) play a pivotal role in the regulation of chromatin structure and gene expression, making them key targets in structural and epigenetic research. Synthetic histone peptides bearing specific PTMs are essential tools for elucidating the molecular mechanisms of histone function and protein–histone interactions. Methods: We synthesized histone H4 tail peptides containing site-specific lysine modifications using solid-phase peptide synthesis (SPPS). The correct synthesis of the peptides was confirmed by their molecular weights using a mass spectrometer. Results: An improved high-performance liquid chromatography (HPLC) method was developed to efficiently separate peptides with one modification difference. In alignment with green chemistry principles, we evaluated ethanol and isopropanol as an alternative organic solvent to acetonitrile in the mobile phase. The optimized HPLC method using acetonitrile enabled effective resolution of closely related peptide species, providing peptides suitable for downstream applications requiring high purities such as structural biology. Conclusions: This study presents a strategy for the purification of histone PTM peptides, emphasizing both analytical performance and sustainability. Further investigation must be undergone to develop high-precision purification using green chemicals. Full article

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20 pages, 6043 KB

Open AccessArticle

Process Design and Optimisation Analysis for the Production of Ultra-High-Purity Phosphine

by Jingang Wang, Yu Liu, Jinyu Guo, Shuyue Zhou, Yawei Du and Xuejiao Tang

Separations 2025, 12(10), 274; https://doi.org/10.3390/separations12100274 - 9 Oct 2025

Abstract

With the increasing demand to scale the chip industry, attention is turning to the vital role that phosphanes and silanes play in semiconductor manufacturing processes such as chemical vapor deposition, plasma etching, and impurity doping. High-performance semiconductors often require a supply of ultra-pure [...] Read more.

With the increasing demand to scale the chip industry, attention is turning to the vital role that phosphanes and silanes play in semiconductor manufacturing processes such as chemical vapor deposition, plasma etching, and impurity doping. High-performance semiconductors often require a supply of ultra-pure gaseous phosphine (≥99.999%) to ensure the formation of defect-free thin-film structures with high integrity and strong functionality. In recent years, research on high-purity PH₃ synthesis methods has mainly focused on two pathways: the acidic route with fewer side reactions, high by-product economics, and higher exergy of high-purity PH₃, and the alkaline alternative with greater potential for practical application through lower reaction temperatures and a simpler reaction process. This paper presents the first comparative study and analysis on the preparation of ultra-high-purity PH₃ and its process energy consumption. Using Aspen and its related software, the energy consumption and cost issues are discussed, and the process heat exchange network is established and optimised. By combining Aspen Plus V14 with MATLAB 2023, an artificial neural network (ANN) prediction model is established, and the parameters of the distillation section equipment are optimised through the NSGA-II model to solve problems such as low product yield and large equipment exergy loss. After optimisation, it can be found that in terms of energy consumption and cost indicators, the acidic process has greater advantages in large-scale production of high-purity PH₃. The total energy consumption of the acidic process is 1.6 × 10⁸ kJ/h, which is only one-third that of the alkaline process, while the cost of the heat exchange equipment is approximately three-quarters that of the alkaline process. Through dual-objective optimisation, the exergy loss of the acidic distillation part can be reduced by 1714.1 kW, and the economic cost can be reduced by USD 3673. Therefore, from the perspective of energy usage and equipment manufacturing, the comprehensive analysis of the acidic process has more advantages than that of the alkaline process. Full article

(This article belongs to the Special Issue New Approaches to Phosphorus Pollutant Control and Phosphorus Recovery)

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16 pages, 2595 KB

Open AccessArticle

Vapor Liquid Equilibrium Measurement and Distillation Simulation for Azeotropic Distillation Separation of H₂O/EM Azeotrope

by Chunli Li, Jinxin Zhang, Jiqing Rao, Kaile Shi, Yuze Sun, Wen Liu and Jiapeng Liu

Separations 2025, 12(10), 273; https://doi.org/10.3390/separations12100273 - 8 Oct 2025

Abstract

Since H₂O and Ethylene Glycol Monomethyl Ether (EM) form a minimum-boiling azeotrope, 1-pentanol, 1-hexanol, and 1-heptanol are selected as entrainers to separate the azeotropic mixture (H₂O/EM) using azeotropic distillation. The binary vapor liquid equilibrium (VLE) data were determined at [...] Read more.

Since H₂O and Ethylene Glycol Monomethyl Ether (EM) form a minimum-boiling azeotrope, 1-pentanol, 1-hexanol, and 1-heptanol are selected as entrainers to separate the azeotropic mixture (H₂O/EM) using azeotropic distillation. The binary vapor liquid equilibrium (VLE) data were determined at 101.3 kPa, including H₂O/EM, EM/1-pentanol, EM/1-hexanol, EM/1-heptanol, H₂O/1-pentanol, H₂O/1-hexanol and H₂O/1-heptanol. Meanwhile, the Herington area test was used to validate the thermodynamic consistency of the experimental binary data. The VLE data for the experimental binary system were analyzed using the NRTL, UNIQUAC, and Wilson activity coefficient models, showing excellent agreement between predictions and measurements. Finally, molecular simulations were employed to calculate interaction energies between components, providing insights into the VLE behavior. The azeotropic distillation process was simulated using Aspen Plus to evaluate the separation performance and determine the optimal operating parameters. Therefore, this study provides guidance and a foundational basis for the separation of H₂O/EM systems at 101.3 kPa. Full article

(This article belongs to the Special Issue Green Separation and Purification Technology)

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12 pages, 3054 KB

Open AccessArticle

The Influence of Y₂O₃ Nanoparticles on the Permeation Properties of Polyethersulfone Membranes

by Andreea Liliana Lazăr, Adrian Cîrciumaru, Gina Genoveva Istrate, Eliza Dănăilă and Ștefan Baltă

Separations 2025, 12(10), 272; https://doi.org/10.3390/separations12100272 - 7 Oct 2025

Abstract

Y₂O₃ nanoparticles were used in a polyethersulfone (PES) as additives to increase the permeation properties of the polymeric membranes. Membranes were manufactured by diffusion-induced phase inversion in N-methyl-pyrrolidone (NMP) using a different concentration of nanoparticles. Y₂O₃ is [...] Read more.

Y₂O₃ nanoparticles were used in a polyethersulfone (PES) as additives to increase the permeation properties of the polymeric membranes. Membranes were manufactured by diffusion-induced phase inversion in N-methyl-pyrrolidone (NMP) using a different concentration of nanoparticles. Y₂O₃ is used in polymeric membranes to enhance their functional properties, especially in wastewater treatment processes. Incorporating Y₂O₃ nanoparticles into the polymer matrix improves the membrane’s hydrophilicity, permeability, and mechanical strength. Additionally, Y₂O₃ provides better properties and reduces fouling. Recent studies highlight its potential as a modifying agent for advanced composite membranes. This paper investigated challenges in the synthesis of Y₂O₃-enhanced membranes and links synthesis with performance. It was observed that the composite membranes have better permeation properties by adding a small amount of Y₂O₃. For membranes at 21 wt.% PES permeability increase from 107 to 112 L/m²·h/bar. Fouling performance increases by adding nanoparticles, relative flux decreases by 30% for membranes without nanoparticles and by 10% for membranes with nanoparticles, both at a concentration of 25% PES. Rejection increases for membranes at 21%Pes from 21% for membranes without nanoparticles to 39% for membranes with nanoparticles. The influence of Y₂O₃ nanoparticles on the membranes’ performance was determined by filtration experiments to establish the permeability, fouling, retention, and the water flux; by contact angle to establish the surface hydrophilicity; and by SEM to investigate the membranes’ structures. Full article

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16 pages, 1878 KB

Open AccessArticle

Nitrous Oxide Emission from a Single-Stage Oxygen-Limited Mainstream Anammox Reactor Treating Moderate C/N Ratio Sewage

by Da Di, Xiwei Cao and Xin Zhou

Separations 2025, 12(10), 271; https://doi.org/10.3390/separations12100271 - 7 Oct 2025

Abstract

Nitrous oxide (N₂O), a potent greenhouse gas, is an important environmental concern associated with biological nitrogen removal in wastewater treatment plants. Anaerobic ammonium oxidation (anammox), recognized as an advanced carbon-neutral nitrogen removal technology, requires a continuous supply of nitrite, which also [...] Read more.

Nitrous oxide (N₂O), a potent greenhouse gas, is an important environmental concern associated with biological nitrogen removal in wastewater treatment plants. Anaerobic ammonium oxidation (anammox), recognized as an advanced carbon-neutral nitrogen removal technology, requires a continuous supply of nitrite, which also serves as a key precursor for N₂O generation. However, the regulation of the carbon-to-nitrogen (C/N) ratio to minimize N₂O emission in mainstream anammox systems remains insufficiently understood. In this study, we evaluated the long-term nitrogen removal performance and N₂O emission potential of an oxygen-limited anammox biofilm reactor treating synthetic municipal wastewater with a typical C/N range of 4.0–6.0. Experimental results demonstrated that the highest nitrogen removal efficiency (95.3%), achieved through coupled anammox and denitrification, and the lowest N₂O emission factor (0.73%) occurred at a C/N ratio of 5.0. As the C/N ratio increased from 4.0 to 5.0, N₂O emissions decreased progressively, but rose slightly when the ratio was further increased to 6.0. High-throughput sequencing revealed that microbial community composition and the abundance of key functional taxa were significantly influenced by the C/N ratio. At a C/N ratio of 5.0, proliferation of anammox bacteria and the disappearance of Acinetobacter populations appeared to contribute to the significant reduction in N₂O emission. Furthermore, gene annotation analysis indicated higher abundances of anammox-associated genes (hzs, hdh) and N₂O reductase gene (nosZ) at this ratio compared with others. Overall, this study identifies a C/N-dependent strategy for mitigating N₂O emissions in mainstream anammox systems and provides new insights into advancing carbon-neutral wastewater treatment. Full article

(This article belongs to the Special Issue Sustainable Biological Removal and Separation Processes in Wastewater Treatment)

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17 pages, 3863 KB

Open AccessArticle

Adsorption of Cr(III) by IRA-900 Resin in Sodium Phosphite and Sulfuric Acid System

by Tingjie Xu, Dahuan Gan, Guowang Wei, Yingjie Yang, Qiankun Wei and Chunlin He

Separations 2025, 12(10), 270; https://doi.org/10.3390/separations12100270 - 5 Oct 2025

Abstract

Chromium (Cr), a toxic heavy metal, poses significant environmental and health risks when industrial effluents containing Cr are discharged untreated. Addressing this challenge, this study developed a selective chromium removal strategy using IRA-900 resin in a sulfuric acid system with sodium phosphite (NaH [...] Read more.

Chromium (Cr), a toxic heavy metal, poses significant environmental and health risks when industrial effluents containing Cr are discharged untreated. Addressing this challenge, this study developed a selective chromium removal strategy using IRA-900 resin in a sulfuric acid system with sodium phosphite (NaH₂PO₃) as a complexing agent. In the NaH₂PO₃-H₂SO₄ system, IRA-900 resin exhibited exceptional selectivity for Cr³⁺ with minimal co-adsorption of competing ions. The adsorption process followed the Langmuir isotherm model (R² > 0.99), indicating monolayer chemisorption dominated by homogeneous active sites, and achieved a maximum capacity of 103.56 mg·g⁻¹. Characterization via XPS, FT-IR, and SEM-EDS revealed a two-step mechanism: Cr³⁺ reacts with H₂PO₃⁻ to form an anionic complex, and then the complex undergoes electrostatic interaction and ion exchange with chloride ions (Cl⁻) on the quaternary ammonium groups of the resin. The chromium-loaded resin demonstrated remarkable structural stability, resisting Cr³⁺ desorption under conventional elution conditions. This property provides a novel pathway for chromium solidification in industrial wastewater, effectively minimizing secondary pollution risks. This work advances the design of ligand-assisted ion-exchange systems for targeted heavy metal removal, offering both high selectivity and environmental compatibility in wastewater treatment. Full article

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

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23 pages, 6833 KB

Open AccessArticle

Ultrasound-Assisted Deep Eutectic Solvent Extraction of Flavonoids from Cercis chinensis Seeds: Optimization, Kinetics and Antioxidant Activity

by Penghua Shu, Shuxian Fan, Simin Liu, Yu Meng, Na Wang, Shoujie Guo, Hao Yin, Di Hu, Xinfeng Fan, Si Chen, Jiaqi He, Tingting Guo, Wenhao Zou, Lin Zhang, Xialan Wei and Jihong Huang

Separations 2025, 12(10), 269; https://doi.org/10.3390/separations12100269 - 2 Oct 2025

Abstract

This study establishes an efficient and eco-friendly ultrasound-assisted extraction (UAE) method for total flavonoids present in Cercis chinensis seeds using natural deep eutectic solvents (NADES). Among nine NADES formulations screened, choline chloride–levulinic acid (ChCl–Lev, 1:2) demonstrated optimal performance, yielding 112.1 mg/g total flavonoids. [...] Read more.

This study establishes an efficient and eco-friendly ultrasound-assisted extraction (UAE) method for total flavonoids present in Cercis chinensis seeds using natural deep eutectic solvents (NADES). Among nine NADES formulations screened, choline chloride–levulinic acid (ChCl–Lev, 1:2) demonstrated optimal performance, yielding 112.1 mg/g total flavonoids. Through Response Surface Methodology (RSM), the ultrasound-assisted extraction (UAE) parameters were explored. Under the optimized conditions (water content of 30%, time of 28 min, temperature of 60 °C, and solvent-to-solid ratio of 1:25 g/mL), the total flavonoid yield reached 128.5 mg/g, representing a 195% improvement compared to conventional ethanol extraction. The recyclability of NADES was successfully achieved via AB-8 macroporous resin, retaining 80.89% efficiency after three cycles. Extraction kinetics, modeled using Fick’s second law, confirmed that the rate constant (k) increased with temperature, highlighting temperature-dependent diffusivity as a key driver of efficiency. The extracted flavonoids exhibited potent antioxidant activity, with IC₅₀ values of 0.86 mg/mL (ABTS•⁺) and 0.69 mg/mL (PTIO•). This work presents a sustainable NADES-UAE platform for flavonoid recovery and offers comprehensive mechanistic and practical insights for green extraction of plant bioactives. Full article

(This article belongs to the Special Issue Extraction, Purification and Functional Substances of Natural Products and Plants)

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14 pages, 264 KB

Open AccessArticle

Variations in Quantitative Composition of Phenolic Compounds in Flowers, Leaves, and Fruits of Mespilus germanica L. During Harvesting Period

by Jelena Nikolić, Vesna Stankov Jovanović, Jovana Pavlović, Milica D. Nikolić, Ana Barjaktarević, Ksenija Obradović and Milan Mitić

Separations 2025, 12(10), 268; https://doi.org/10.3390/separations12100268 - 1 Oct 2025

Abstract

The medlar (Mespilus germanica) is a deciduous tree that belongs to the Rosaceae family. This plant has been valued throughout history for its culinary uses and medicinal applications. Medlar fruit contains a high amount of vitamin C, carbohydrates, and pectin, making [...] Read more.

The medlar (Mespilus germanica) is a deciduous tree that belongs to the Rosaceae family. This plant has been valued throughout history for its culinary uses and medicinal applications. Medlar fruit contains a high amount of vitamin C, carbohydrates, and pectin, making it a valuable remedy for treating scurvy. In folk medicine, medlar is used to treat constipation and other digestive issues. This study investigates the quantitative composition and seasonal variation in phenolic compounds in flowers, leaves, and fruits of Mespilus germanica L. using high performance liquid chromatography, as well as total phenolic content and antioxidant activity. The predominant class of phenolics in flowers were flavonols, with 52.5% of the total phenolic content. On the other hand, dominant phenolics in fruits were flavan-3-ols, with procyanidin B2 and epicatechin being most abundant, whereas in leaves, hydroxycinnamic acids were the most prevalent phenolic compounds. Seasonal variations were noted for analyzed compounds in various plant parts. This study highlights significant changes in the phenolic profile of M. germanica during various harvesting periods and suggests that both fruits and leaves are rich sources of bioactive compounds. However, its nutraceutical potential might depend on harvesting time. Full article

(This article belongs to the Special Issue Application of Chromatography in Bioactive Compound Analysis)

20 pages, 3112 KB

Open AccessArticle

Porous Imprinted Microspheres with Covalent Organic Framework-Based, Precisely Designed Sites for the Specific Adsorption of Flavonoids

by Jinyu Li, Xuan Zhang, Jincheng Xu, Xi Feng and Shucheng Liu

Separations 2025, 12(10), 267; https://doi.org/10.3390/separations12100267 - 1 Oct 2025

Abstract

The application of microsphere molecularly imprinted materials for the targeted extraction and purification of flavonoids derived from agricultural waste has emerged as a prominent area of investigation. An innovative boronate affinity imprinted microsphere (MC-CD@BA-MIP) was successfully synthesized using the Pickering emulsion interfacial assembly [...] Read more.

The application of microsphere molecularly imprinted materials for the targeted extraction and purification of flavonoids derived from agricultural waste has emerged as a prominent area of investigation. An innovative boronate affinity imprinted microsphere (MC-CD@BA-MIP) was successfully synthesized using the Pickering emulsion interfacial assembly strategy for the selective separation of naringin (NRG). The double-bond functionalized covalent organic framework (COF)-based microspheres were synthesized through Schiff–base reaction and secondary interfacial emulsion polymerization. Then, the synthetic mono-(6-mercapto-6-deoxy)-β-cyclodextrin (SH-β-CD) was grafted onto the surface of the microspheres (MC) using click chemistry. The 1-allylpyridine-3-boronic acid (APBA) as a functional monomer was grafted onto the initiator (ABIB) through atom transfer radical polymerization (ATRP). Ultimately, the synthesized boronic acid-imprinted ABIB-BA-MIPs were immobilized onto the COFs microsphere surface through host–guest interactions. As expected, under neutral conditions, the MC-CD@BA-MIPs still exhibited a significant adsorption capacity (38.78 μmol g⁻¹ at 308 K) for NRG. The regenerated MC-CD@BA-MIPs maintained 92.56% of their initial adsorption capacity through six consecutive cycles. Full article

(This article belongs to the Special Issue Recognition Materials and Separation Applications)

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33 pages, 1525 KB

Open AccessArticle

Mineral Extraction from Mixed Brine Solutions

by M. A. Salman, M. Ahmed, H. Al-Sairfi and Y. Al-Foudari

Separations 2025, 12(10), 266; https://doi.org/10.3390/separations12100266 - 1 Oct 2025

Abstract

Sulfate minerals (SMs), such as BaSO₄, SrSO₄, and CaSO₄, precipitate when incompatible solutions from the oil industry, such as seawater (SW) and high-salinity brine solutions (HSBSs), are mixed during the oil production process. To investigate the potentiality [...] Read more.

Sulfate minerals (SMs), such as BaSO₄, SrSO₄, and CaSO₄, precipitate when incompatible solutions from the oil industry, such as seawater (SW) and high-salinity brine solutions (HSBSs), are mixed during the oil production process. To investigate the potentiality to extract SM by mixing three different brine solutions, such as HSBS-1, -2, and -3, with SW, at different temperatures and pressures, a practical simple model was used to predict the saturation index (SI), the quantity of precipitated minerals (Y), and the induction time (t_ind) required for precipitation. From the results, it was found that CaSO₄ hemihydrate and SrSO₄ yield lower amounts of precipitate. BaSO₄ precipitation ranges from 20 to 60 mg/L and 1500 mg/L of CaSO₄ anhydrous under ambient conditions. These findings suggest that recovering low-solubility minerals is technically feasible and environmentally preferable to direct disposal. Full article

(This article belongs to the Topic Separation Techniques and Circular Economy)

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