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Intensified Roasting at Low-Temperature and Alkaline Leaching to Efficiently Remove Harmful Elements for Green Utilization of Secondary Aluminum Dross
Analysis of the Characteristic Chromatogram and Quantitative Determination of 25 Marker Compounds in the Traditional Chinese Medicine Preparation Qili Qiangxin Capsules by HPLC-DAD-ESI-MS/MS
Advancing Iron Recovery from Red Mud: Green Pathways, Synergistic Valorization, and High-Value Total Component Utilization
Experimental Evaluation of Hydrocarbon Class-Based Evaporative Emissions from Ethanol-Blended Gasoline Using HS-SPME–GC–MS
Innovating Slow Sand Filtration: Exploring the Regeneration of a Traditional Technology for the 21st Century

Journal Description

Separations

Separations - formerly Chromatography - is an international, peer-reviewed, open access journal on separation and purification science and technology in all areas of chemical, biological, physical science, and separation performance, published monthly online by MDPI. The Central European Group of Separation Sciences (CEGSS) is affiliated with Separations and its members receive discounts on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), CAPlus / SciFinder, and other databases.
Journal Rank: JCR - Q2 (Chemistry, Analytical) / CiteScore - Q2 (Analytical Chemistry)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 15.1 days after submission; acceptance to publication is undertaken in 2.8 days (median values for papers published in this journal in the first half of 2026).
Recognition of Reviewers: Reviewers whose reports are timely and of high quality receive an APC discount voucher for a future publication in an MDPI journal. Become a reviewer.
Companion journal: Purification.
Journal Cluster of Analysis and Sensing Technologies: Analytica, Biosensors, Chemosensors, Purification, Separations and Spectroscopy Journal.

Impact Factor: 3.5 (2025); 5-Year Impact Factor: 3.3 (2025)

Imprint Information Journal Flyer Open Access ISSN: 2297-8739

Latest Articles

18 pages, 1823 KB

Open AccessArticle

Studies on the Phytochemical Variability of Xanthine Alkaloids from the Leaves of Ilex guayusa Loes. in the Amazon Region of Ecuador

by Christian Larenas, Jonathan Chauca, Edison Osorio, Marjourie Yanez and Paco Noriega

Separations 2026, 13(9), 267; https://doi.org/10.3390/separations13090267 (registering DOI) - 18 Sep 2026

Ilex guayusa Loes., known as guayusa, is a plant that has been used for generations by the indigenous peoples of the Ecuadorian Amazon for its medicinal properties, notably its stimulating effects. This bioactivity is primarily due to the presence of xanthine alkaloids such [...] Read more.

Ilex guayusa Loes., known as guayusa, is a plant that has been used for generations by the indigenous peoples of the Ecuadorian Amazon for its medicinal properties, notably its stimulating effects. This bioactivity is primarily due to the presence of xanthine alkaloids such as caffeine, theobromine, and theophylline. In this study, the concentration of each alkaloid was determined in thirty populations throughout the Amazon region, with data ranging from 2065.0 mg/100 g to 364.8 mg/100 g for caffeine; 225.8 mg/100 g and 74.6 mg/100 g for theobromine; and 4.9 mg/100 g and 1.5 mg/100 g for theophylline. A statistical analysis was conducted on twenty-four guayusa populations by integrating alkaloid concentrations with altitude, climatic, and soil variables. Caffeine showed high variability among populations and was only weakly associated with elevation, whereas theobromine and theophylline were determined primarily by climatic and soil factors. These results indicate that methylxanthine accumulation in Ilex guayusa is driven by the combined influence of climatic and edaphic conditions rather than by a single environmental factor. Full article

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

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14 pages, 16130 KB

Open AccessArticle

Identifying Accessible Ag⁺ Sites as the Key Active Sites Governing Xenon Capture in Ag-Exchanged FAU Zeolite

by Yuqiang Sheng, Yongzhen Zhang, Shujiang Liu, Zhanying Chen, Di Liu and Shilian Wang

Separations 2026, 13(9), 266; https://doi.org/10.3390/separations13090266 - 17 Sep 2026

To address the challenge of identifying the true structure–performance relationship governing xenon adsorption in silver-exchanged zeolites, a series of Ag/13X adsorbents with tunable silver loadings were synthesized via liquid-phase ion exchange. The unique FAU-type topology of 13X zeolite, composed of spacious supercages interconnected [...] Read more.

To address the challenge of identifying the true structure–performance relationship governing xenon adsorption in silver-exchanged zeolites, a series of Ag/13X adsorbents with tunable silver loadings were synthesized via liquid-phase ion exchange. The unique FAU-type topology of 13X zeolite, composed of spacious supercages interconnected by large 12-membered-ring windows, enables high silver dispersion while minimizing diffusion limitations. This unique structural advantage makes Ag/13X an ideal model system for investigating the intrinsic role of silver active sites in Xe adsorption. We identify a pronounced volcano-shaped dependence of Xe adsorption on silver loading, establishing that total silver content is not the governing factor for Xe capture. Combined structural characterization and spectroscopic analyses reveal that increasing silver loading continuously alters silver speciation from highly dispersed Ag⁺ ions toward more aggregated silver species, which may reduce the fraction of accessible Ag⁺-related adsorption sites and simultaneously modify the local electronic environment of silver species. At an optimal AgNO₃ exchange concentration of 0.5 M, the predominance of well-dispersed Ag⁺ species maximizes accessible active-site density and leads to the highest Xe uptake. Charge-corrected GCMC simulations provide molecular-level validation by showing that these accessible Ag⁺ sites reinforce Xe adsorption through stronger ion-induced dipole interactions. Consequently, this work identifies the density of accessible Ag⁺ sites as an important descriptor for Xe capture, offering a design guideline for engineering high-efficiency noble-gas adsorbents. Full article

(This article belongs to the Special Issue Functional Materials in Adsorption and Separation)

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13 pages, 3015 KB

Open AccessArticle

Structural Modification of Naringenin via γ-Irradiation, Chiral Separation, and Evaluation of Anti-Inflammatory Activity

by Montaha Mt. Miratun, Ah-Reum Han, Chang Hyun Jin, Euna Choi, Ha-Yeon Song, Trung Huy Ngo, Kyu Joon Lee, Hyukjae Choi, Joo-Won Nam and Eui-Baek Byun

Separations 2026, 13(9), 265; https://doi.org/10.3390/separations13090265 - 16 Sep 2026

Naringenin is a flavanone recognized for its diverse pharmacological properties, including anti-inflammatory and anticancer effects. This study aimed to produce novel structures with enhanced biological activity by subjecting (±)-naringenin (1) to γ-irradiation. Compound 1 in an ethanol solution was irradiated at [...] Read more.

Naringenin is a flavanone recognized for its diverse pharmacological properties, including anti-inflammatory and anticancer effects. This study aimed to produce novel structures with enhanced biological activity by subjecting (±)-naringenin (1) to γ-irradiation. Compound 1 in an ethanol solution was irradiated at doses of 30, 50, 70, and 100 kGy, among which the 100 kGy dose yielded the highest concentration of radiolysis products. These radiolysis products were further processed through multi-step semi-preparative HPLC utilizing a chiral column, yielding compounds 2–5. These compounds were identified as apigenin (2) and three stereoisomers of 2-(1-hydroxyethyl)-naringenin (2,3-dihydro-5,7-dihydroxy-2-(1-hydroxyethyl)-2-phenyl-4H-1-benzopyran-4-one; 3–5) via high-resolution electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. The absolute stereochemistry of compounds 3–5 was determined to be (2S,11S)-, (2S,11R)-, and (2R,11S)-configurations, respectively, by comparing experimental electronic circular dichroism data and specific optical rotations. Evaluation of nitric oxide inhibition in lipopolysaccharide-stimulated RAW 264.7 cells revealed that compound 2 exhibited greater activity to the parent compound 1, whereas derivatives 3‒5 were inactive. These findings indicate that γ-irradiation is an effective strategy for structural modification and enhancing the bioactivity in flavonoids. Full article

(This article belongs to the Special Issue Advanced Purification Technologies for Bioactive Natural Products)

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18 pages, 1478 KB

Open AccessArticle

Extractability of C-Phycocyanin from Limnospira platensis and Its Antioxidant Capacity Using Spark Discharge Plasma

by Jan Kuhnholz, Albert Beyer, Martina Balazinski, Anja Noke and Katja Zocher

Separations 2026, 13(9), 264; https://doi.org/10.3390/separations13090264 - 16 Sep 2026

Phycocyanin as water-soluble, accessory pigment is commonly extracted from Limnospira platensis (L. platensis). The pigment is often used as natural food colourant and is a potential antioxidant. Usually, the pigment is extracted with several freeze–thawing cycles with subsequent purification steps. The [...] Read more.

Phycocyanin as water-soluble, accessory pigment is commonly extracted from Limnospira platensis (L. platensis). The pigment is often used as natural food colourant and is a potential antioxidant. Usually, the pigment is extracted with several freeze–thawing cycles with subsequent purification steps. The cell disintegration with physical plasma (here spark discharges) is already described for microalgae and was tested for the extraction of phycocyanin from L. platensis. Moreover, calcium chloride was examined as a non-toxic and inexpensive precipitator in the purification step. Samples were treated with water as solvent alone or precipitated with calcium chloride. Also, samples were divided for immediate analysis after extraction and 24 h incubation after the respective cell wall rupture method with subsequent analysis. The extracts were tested for C-phycocyanin (C-PC) concentration, content, selectivity, and radical scavenging activity. Spark discharges were administered with 4 Hz, 100 ns high-voltage pulses of 35 kV, resulting in a pulse energy of ca. 0.2 J/pulse. For freeze–thawing, a maximum yield of 2.75 mg/mL was obtained, for spark discharges, max. 0.24 mg/mL. However, despite a lower concentration, a remarkable purity was found for plasma-treated samples. In addition, radical scavenging activity was not influenced by the spark discharge exposure. Full article

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

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23 pages, 28757 KB

Open AccessArticle

RGB-D Semantic-Guided 3D Geometric Estimation for Intelligent Coal Gangue Separation

by Zhiyuan Sun, Zhongjun Zhou, Tianyang Sun, Shiyu Wang and Kaile Xiao

Separations 2026, 13(9), 263; https://doi.org/10.3390/separations13090263 - 15 Sep 2026

Coal and gangue separation is crucial for clean and efficient coal utilization. However, practical sorting environments are highly unstructured, where irregular fragments exhibit random distribution, varying orientations, and occlusion. Conventional 2D vision methods cannot provide the 3D geometric information required for intelligent sorting, [...] Read more.

Coal and gangue separation is crucial for clean and efficient coal utilization. However, practical sorting environments are highly unstructured, where irregular fragments exhibit random distribution, varying orientations, and occlusion. Conventional 2D vision methods cannot provide the 3D geometric information required for intelligent sorting, while model-based 6D pose estimation is unsuitable for coal gangue fragments due to their irregular morphology and lack of predefined models. This study proposes an RGB-D cascaded fusion framework for partial point cloud-based 3D geometric estimation. The framework follows a detection–segmentation–reconstruction pipeline, where object detection provides semantic priors, zero-shot segmentation generates pixel-level masks, and the masks guide depth extraction and local point cloud reconstruction. Based on the reconstructed point clouds, task-oriented geometric parameters, including centroid position, oriented bounding box dimensions, visible volume, and principal orientation, are estimated for intelligent separation. Experiments on a dedicated RGB-D coal and gangue dataset demonstrate that the proposed method achieves a centroid localization error of 14.22 mm, dimension error of 9.34%, and volume error of 11.3%. Compared with detection-box-based depth reconstruction, the proposed semantic-guided strategy significantly improves geometric estimation accuracy. The proposed framework provides reliable 3D perception for intelligent coal gangue separation and robotic sorting. Full article

(This article belongs to the Special Issue Efficient Separation of Coal and Mineral Resources)

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30 pages, 8331 KB

Open AccessArticle

Peanut Husk as an Efficient Biosorbent for Methylene Blue Removal from Wastewater: Kinetic, Isotherm, and Exploratory Artificial Neural Network Analysis

by Yu-Ting Huang and Ming-Cheng Shih

Separations 2026, 13(9), 262; https://doi.org/10.3390/separations13090262 - 15 Sep 2026

This study explores the adsorption performance of clean peanut husk (CPH) as a sustainable and low-cost biosorbent for removing methylene blue (MB) from aqueous solutions. Batch experiments investigated the effects of dye concentration, biosorbent dosage, pH, particle size, and temperature. FT-IR analysis confirmed [...] Read more.

This study explores the adsorption performance of clean peanut husk (CPH) as a sustainable and low-cost biosorbent for removing methylene blue (MB) from aqueous solutions. Batch experiments investigated the effects of dye concentration, biosorbent dosage, pH, particle size, and temperature. FT-IR analysis confirmed the involvement of hydroxyl, carbonyl, and aromatic groups, with spectral changes indicating both physical and chemical adsorption mechanisms. Adsorption capacity increased with initial dye concentration and decreased with larger particle size or excessive adsorbent dosage. The process was highly pH-sensitive, favoring adsorption under neutral to alkaline conditions, while temperature had minimal influence, a finding compatible with a physisorption-dominated contribution to the overall process. Kinetic data were best described by the pseudo-second-order model, and equilibrium behavior was best described by the Langmuir isotherm; however, these mathematical fits are interpreted here as indicative of, rather than definitive proof of, the specific molecular mechanism, and the overall adsorption process is best described as involving a combination of physisorption and chemisorption contributions. The separation factor (RL) values indicated favorable adsorption. Furthermore, an exploratory artificial neural network (ANN) analysis, based on a limited dataset of 39 experimental observations, achieved a high goodness-of-fit (R² = 0.99) in describing the nonlinear relationships between each individual operational parameter and the adsorption capacity; given the small sample size and limited validation strategy employed, these results should be regarded as a preliminary demonstration of feasibility rather than evidence of robust predictive generalization. The findings support the potential of CPH as an efficient biosorbent for dye-contaminated wastewater. Full article

(This article belongs to the Special Issue Adsorption/Degradation for Environmental Pollutants)

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21 pages, 11145 KB

Open AccessArticle

A Dynamic Relationship-Aware Approach to Flotation Concentrate Grade Prediction Using DGraFormer

by Lingyu Zhao, Fuming Qu, Hui Chen, Zhengyu Liu, Yaming Ji and Xiaoming Liu

Separations 2026, 13(9), 261; https://doi.org/10.3390/separations13090261 - 14 Sep 2026

Accurate prediction of flotation concentrate grade is essential for maintaining product quality and supporting timely process adjustment. However, mechanistic prediction remains difficult because industrial flotation involves nonlinear multivariable interactions and partially observed operating states. Recent advances in machine learning have increased interest in [...] Read more.

Accurate prediction of flotation concentrate grade is essential for maintaining product quality and supporting timely process adjustment. However, mechanistic prediction remains difficult because industrial flotation involves nonlinear multivariable interactions and partially observed operating states. Recent advances in machine learning have increased interest in data-driven methods, with encouraging results. Although recent studies have incorporated temporal dependencies into flotation-grade prediction, explicitly modeling the condition-dependent evolution of multivariate process–quality relationships under changing plant conditions remains challenging. In this study, industrial flotation records were systematically analyzed from a data-driven perspective to identify challenges affecting concentrate-grade prediction. Statistical analyses showed that variable–grade relationships are condition-dependent and vary across operating periods, indicating that measured variables only partially characterize evolving flotation states and that fixed input–output mappings may be inadequate. Accordingly, a DGraFormer-based model was developed to capture evolving inter-variable dependencies and multi-scale temporal patterns. For one-hour-ahead forecasting, the model achieved an RMSE of 0.7587 and an

R^{2}

of 0.5423 for iron concentrate grade, and an RMSE of 0.6917 and an

R^{2}

of 0.6384 for silica concentrate grade, outperforming the evaluated machine-learning and deep-learning baselines overall. These results underscore the importance of dynamic multivariate modeling for accurate concentrate-grade forecasting. Full article

(This article belongs to the Special Issue Mineral Flotation Separation and Resource Utilization)

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15 pages, 430 KB

Open AccessArticle

Comparative Volatile Profiles and Biological Activities of Methanol and Ethyl Acetate Extracts of Two Endemic Origanum Species from Türkiye

by Ahmet Ozan Cengiz, Yavuz Bülent Köse, Bilge Nur Mutlu, Derya Osmaniye and Betül Demirci

Separations 2026, 13(9), 260; https://doi.org/10.3390/separations13090260 - 14 Sep 2026

Origanum saccatum P.H. Davis and O. solymicum P.H. Davis are two endemic species of section Amaracus distributed in Türkiye and characterized by close morphological and genetic relationships. Although their volatile and non-volatile compounds and several biological activities have previously been investigated, the antimicrobial [...] Read more.

Origanum saccatum P.H. Davis and O. solymicum P.H. Davis are two endemic species of section Amaracus distributed in Türkiye and characterized by close morphological and genetic relationships. Although their volatile and non-volatile compounds and several biological activities have previously been investigated, the antimicrobial and cytotoxic activities of methanol and ethyl acetate extracts of both species have not been systematically compared within a common experimental framework. In this study, the volatile profiles of the two species were compared, while the antimicrobial and cytotoxic activities of their methanol and ethyl acetate extracts were evaluated comparatively. Essential oils were obtained by hydrodistillation and analyzed by GC-FID/GC-MS. Antimicrobial activity was determined by the broth microdilution method, and cytotoxicity was evaluated against A549, MCF-7, and NIH/3T3 cells using the MTT assay. Both essential oils showed a p-cymene-rich profile, although substantial differences were observed in the proportions of γ-terpinene (3.1–24.4%), thymol (4.0–18.2%), borneol (0.6–15.6%), linalool (0.1–10.4%), and carvacrol (0.1–3.4%). The ethyl acetate extracts showed generally lower MIC values (125–250 µg/mL) than the corresponding methanol extracts (500–1000 µg/mL) against the most responsive microorganisms. Ethyl acetate extracts also showed the strongest cytotoxic activity with IC₅₀ values of 6.74–14.49 µg/mL, although the response varied depending on species and cell line. The O. saccatum ethyl acetate extract showed the highest selectivity toward MCF-7 among the tested extracts, with a selectivity index of 3.176. To the best of our knowledge, this is the first report of the cytotoxicity of these two species against A549 and MCF-7 cells. The findings provide a comparative assessment of their volatile profiles and solvent-dependent biological properties. Full article

(This article belongs to the Topic Research on Natural Products of Medical Plants)

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14 pages, 8056 KB

Open AccessArticle

Comparative Investigation of Natural Mineral-Supported Li/Al-LDHs Adsorbents for Lithium Recovery from High Mg/Li Ratio Brines

by Ping Liu, Chuntao Zhang, Jun Guo, Fangyuan Yu and Xu Ma

Separations 2026, 13(9), 259; https://doi.org/10.3390/separations13090259 - 13 Sep 2026

Lithium recovery from salt lake brines with high Mg/Li ratios remains highly challenging due to the comparable physicochemical properties of Mg²⁺ and Li⁺, while lithium–aluminum-layered double hydroxides (Li/Al-LDHs) have emerged as promising lithium-selective adsorbents. However, their practical application is hindered [...] Read more.

Lithium recovery from salt lake brines with high Mg/Li ratios remains highly challenging due to the comparable physicochemical properties of Mg²⁺ and Li⁺, while lithium–aluminum-layered double hydroxides (Li/Al-LDHs) have emerged as promising lithium-selective adsorbents. However, their practical application is hindered by particle aggregation, limited structural stability, and insufficient processability under continuous-flow conditions. Herein, a mineral-directed synthesis strategy was developed to construct natural mineral-supported Li/Al-LDHs composite adsorbents using three abundant clay minerals, chlorite, montmorillonite, and illite, as structural substrates. The mineral crystal structures were demonstrated to regulate the nucleation, growth behavior, and dispersion of Li/Al-LDH nanosheets, resulting in distinct hierarchical architectures and lithium adsorption performances. Comprehensive structural characterization revealed the successful integration of Li/Al-LDH phases with different mineral matrices while preserving the intrinsic layered structures of both components. The results demonstrated that different mineral substrates significantly influenced the crystal growth, dispersion, and interfacial structure of Li/Al-LDHs. Among the prepared composites, montmorillonite @Li/Al-LDHs exhibited the optimal lithium adsorption performance, achieving a lithium adsorption capacity of 6.0 mg·g⁻¹ and a remarkable Li⁺/Mg²⁺ separation factor of 73.5 in a brine with a high Mg/Li ratio of 61.25. Furthermore, the optimized adsorbent maintained 81.7% of its initial adsorption capacity after 100 adsorption–desorption cycles and demonstrated stable lithium recovery performance under continuous-flow conditions. This work establishes the relationship between natural mineral crystal structures and Li/Al-LDH adsorption behaviors, providing new insights into the rational design of economical, scalable, and environmentally friendly lithium adsorbents for sustainable recovery of lithium resources from Mg-rich brines. Full article

(This article belongs to the Special Issue Emerging New Technologies in Fundamental and Industrial Crystallization)

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25 pages, 1316 KB

Open AccessReview

Formed Activated Alumina for Adsorptive Water Separation from Compressed Air: A Critical Review of Material–Bed–Cycle Evidence and Failure Diagnosis

by Qiaoling Tu, Zengming Qu, Zihuan Wang, Yihang Tian, Gang Tian and Xiaoming Peng

Separations 2026, 13(9), 258; https://doi.org/10.3390/separations13090258 - 13 Sep 2026

Water-vapor removal from compressed air is governed by the product pressure dew point (PDP), dynamic bed utilization, hydraulic loss, regeneration demand, and cyclic reliability, yet activated-alumina studies are often interpreted from powder Brunauer–Emmett–Teller (BET) area or equilibrium uptake alone. This critical narrative review [...] Read more.

Water-vapor removal from compressed air is governed by the product pressure dew point (PDP), dynamic bed utilization, hydraulic loss, regeneration demand, and cyclic reliability, yet activated-alumina studies are often interpreted from powder Brunauer–Emmett–Teller (BET) area or equilibrium uptake alone. This critical narrative review evaluates where evidence can and cannot be transferred across material, formed-particle, packed-bed, cycle, and field scales. It distinguishes equilibrium capacity, static test capacity, dynamic breakthrough capacity, and usable cycle capacity; conditionally compares desiccants and regeneration modes; and links PDP-defined breakthrough, mass-transfer-zone (MTZ)/length-of-unused-bed (LUB) measures, non-spherical-particle pressure drop, thermal waves, and regeneration endpoints. The available evidence supports several directional conclusions but not universal design values: alkali modification can increase uptake despite lower surface area; forming and binder chemistry alter accessible pores and strength; wall effects and particle geometry require measured hydrodynamic validation; and reported regeneration savings of approximately 27–40% are architecture-specific relative results rather than matched absolute energy benchmarks. A baseline-normalized diagnostic framework separates reversible regeneration faults and feed contamination from material aging and particle/bed degradation. The review identifies the central evidence gap as the absence of matched datasets reporting formed-body properties, adiabatic breakthrough, segmented pressure drop, regeneration energy, and long-cycle failure for the same material. It concludes with a standards-coverage map, a transparent screening sensitivity analysis, and a prioritized validation agenda. Full article

(This article belongs to the Section Separation Engineering)

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43 pages, 5065 KB

Open AccessReview

Biochar-Based Sorbents for the Extraction of Emerging Organic Contaminants from Environmental Matrices: A Review

by Eliézer Quadro Oreste, Krystopher Borges Krammer, Antunielle Schneider Arias, Rodrigo Gamarra Navarrete, Janaína Oliveira Gonçalves, Jean Lucas de Oliveira Arias, Karina Lotz Soares, Daiane Dias, Ednei Gilberto Primel, Anelise Christ-Ribeiro and Sergiane Caldas Barbosa

Separations 2026, 13(9), 257; https://doi.org/10.3390/separations13090257 - 11 Sep 2026

The increasing occurrence of emerging organic contaminants (EOCs) in environmental matrices has intensified the demand for sensitive, selective, and sustainable analytical methods. Sample preparation plays a pivotal role, particularly for trace-level determination in complex matrices. Biochar is a promising sorbent for sample preparation [...] Read more.

The increasing occurrence of emerging organic contaminants (EOCs) in environmental matrices has intensified the demand for sensitive, selective, and sustainable analytical methods. Sample preparation plays a pivotal role, particularly for trace-level determination in complex matrices. Biochar is a promising sorbent for sample preparation because of its porous structure, tunable surface chemistry, low cost, and potential to be produced from renewable biomass waste. This review examines the use of biochar-based sorbents to extract EOCs from environmental matrices since 2020, with special emphasis on the relationships among precursor biomass, production conditions, surface chemistry, sorption mechanisms, and extraction performance. Agricultural waste was the predominant biomass class, while solid-phase extraction (SPE), magnetic solid-phase extraction (MSPE), and solid-phase microextraction (SPME) were the most frequently reported approaches. Biochar-based extraction has been applied to a wide range of EOCs, with pesticides being the most investigated analyte class. The authors discuss how pyrolysis conditions, activation, surface chemistry, and other parameters affect analyte retention and desorption. The authors compare different extraction approaches in terms of extraction efficiency, precision, and other analytical parameters. Finally, the authors discuss current limitations and research opportunities to guide the development of biochar-based sorbents as sustainable materials for sample preparation and environmental monitoring. Full article

(This article belongs to the Special Issue Separation Techniques in Environmental Analysis)

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22 pages, 1173 KB

Open AccessArticle

Comparative Characterization of Phenolic Compounds, Fatty Acid Profile, and Antioxidant Activity of Pecan (Carya illinoinensis) Oil Obtained Using Conventional and Green Extraction Methods

by Elsa Uribe, Jéssica López, Camila Cortés and Débora Cerdá-Bernad

Separations 2026, 13(9), 256; https://doi.org/10.3390/separations13090256 - 11 Sep 2026

Pecan oil is a valuable source of unsaturated fatty acids and bioactive compounds whose recovery and stability may be influenced by the extraction process. This study compared Soxhlet extraction (SE), ultrasound-assisted extraction (UAE), and supercritical CO₂ extraction (sCO₂) in terms [...] Read more.

Pecan oil is a valuable source of unsaturated fatty acids and bioactive compounds whose recovery and stability may be influenced by the extraction process. This study compared Soxhlet extraction (SE), ultrasound-assisted extraction (UAE), and supercritical CO₂ extraction (sCO₂) in terms of extraction yield, fatty acid profile, physicochemical properties, total phenolic content (TPC), antioxidant activity, and oxidative stability. SE achieved the highest extraction yield (69.21%), followed by sCO₂ (52.89%) and UAE (48.68%). The fatty acid profile was relatively stable among extraction methods, although differences were observed in the relative proportions of oleic and linolenic acids. UAE produced oil with the highest TPC (32.55 µg GAE/g oil), whereas sCO₂ showed the highest initial antioxidant activity (2681 µmol TE/100 g oil). After 12 days, UAE oil exhibited the lowest peroxide value (10.49 meq O₂/kg) and the highest TPC retention, whereas sCO₂ oil showed the greatest peroxide accumulation (28.16 meq O₂/kg) and the largest decrease in TPC. These results demonstrate that extraction conditions differently affect oil recovery, antioxidant-related properties, and oxidative stability. Under the conditions evaluated, UAE showed particular advantages in preserving TPC and limiting primary oxidation during accelerated storage, despite its lower extraction yield. Full article

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

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20 pages, 7383 KB

Open AccessArticle

Treatment of Licorice Wastewater via Coagulation–Flocculation and Ozonation Combination: ANN-GA Modeling and Optimization

by Babak Rouhi Broujeni and Ayoub Karimi-Jashni

Separations 2026, 13(9), 255; https://doi.org/10.3390/separations13090255 - 10 Sep 2026

This study aimed to remove licorice (Glycyrrhiza glabra) extract from pharmaceutical wastewater using a combination of treatment processes. An Artificial Neural Network (ANN) was coupled with a Genetic Algorithm (GA) to optimize the treatment parameters. Alum, polyaluminum chloride (PAC), and ferric chloride (FC), [...] Read more.

This study aimed to remove licorice (Glycyrrhiza glabra) extract from pharmaceutical wastewater using a combination of treatment processes. An Artificial Neural Network (ANN) was coupled with a Genetic Algorithm (GA) to optimize the treatment parameters. Alum, polyaluminum chloride (PAC), and ferric chloride (FC), were first screened for chemical oxygen demand (COD) and color removal, after which alum was selected as the most effective coagulant for further experiments. The optimal ANN structure was identified based on three criteria: mean absolute percentage error, normalized root mean squared error, and correlation coefficient (R). The variables analyzed included pH (7–12), coagulant dose (200–1000 mg L⁻¹), and oxidation time (6–60 min). ANOVA results revealed that coagulant type was the most statistically significant factor influencing both COD and color removal (p < 0.01), while pH and dose had relatively lower effects unless paired optimally. Results demonstrated a removal efficiency of approximately 98% under optimal conditions (pH = 10, coagulant dose = 610 mg L⁻¹, and ozonation time = 53 min), with a remaining COD of 190 mg L⁻¹. Overall, the combined coagulation–flocculation and ozonation process demonstrated high effectiveness for the treatment of licorice-based pharmaceutical wastewater. Full article

(This article belongs to the Topic Sustainable Water Purification Technologies for Multiple Applications, 2nd Edition)

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14 pages, 2132 KB

Open AccessArticle

Evaluation of UV-Vis Spectrophotometric Applicability for Residual Guar Gum in Bauxite Slurry Systems: Interference, Boundaries, and Sedimentation Validation

by Shanmei Li, Mingxuan Li, Jianping Meng and Ligang Yu

Separations 2026, 13(9), 254; https://doi.org/10.3390/separations13090254 - 9 Sep 2026

Rapid and accurate quantification of residual guar gum in bauxite slurry flocculation is a critical bottleneck for closed-loop control of flocculant dosage. In this study, we systematically compared the anti-interference performance of the two UV-Vis spectrophotometer approaches, the single-wavelength absorbance method (A₂₆₃ [...] Read more.

Rapid and accurate quantification of residual guar gum in bauxite slurry flocculation is a critical bottleneck for closed-loop control of flocculant dosage. In this study, we systematically compared the anti-interference performance of the two UV-Vis spectrophotometer approaches, the single-wavelength absorbance method (A₂₆₃) and the peak-trough difference method (ΔA), in complex slurry matrices. Our results revealed that the two methods respond differently to pH and salt concentration variations, leading to the proposal of a dual-mode synergistic detection strategy. The A₂₆₃ method provides quantification under the specific conditions tested within the ranges of pH 3.0–8.0 and CaCl₂ concentration below 4.5 mmol/L. Beyond these boundaries, deviations from the Beer-Lambert law occurred, attributable to conformational transitions or salting-out aggregation of the polymer chains. In contrast, the ΔA method partially mitigated background drift through differential calculation and exhibited a more stable signal trend than A₂₆₃ across the tested ranges (pH 2.0–11.0, CaCl₂ 0–18 mmol/L), suggesting its potential utility as a semi-quantitative indicator in challenging matrices. However, its quantitative precision was constrained by small absolute signal values and systematic dependence on pH and salt conditions. Based on these findings, we propose a synergistic strategy-preferring the A₂₆₃ method under routine conditions while recommending the ΔA method for high-salinity or wide-pH scenarios- and accordingly define the preliminary applicability boundaries based on signal response observations at a single concentration. Flocculation–sedimentation tests confirmed that the method successfully determined the optimum dosage (5.0 g/kg dry slurry), at which the residual concentration in the supernatant correlated negatively with the sedimentation rate (R² > 0.95). The supernatant matrix after sedimentation (pH ≈ 7.1, low ionic strength) fell exactly within the safe window. This work provides a methodological reference for spectrophotometric quantification of trace organics in turbid, saline, and pH-variable slurry systems, and lays an analytical foundation for intelligent dosage control in bauxite slurry dewatering. Full article

(This article belongs to the Section Purification Technology)

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22 pages, 50567 KB

Open AccessArticle

Chamber-to-Field Development and Validation of Integrated Filtration–Adsorption Air Cleaners for Particle and VOC Control in Shipboard Cabins

by Fanxuan Xia, Tao Yu, Bin Kong, Zhiyuan Wang, Ran Wang, Jiyi Mi, Ruijie Xie, Hanxiao Wang, Zhiwei Li, Zhuo Chen and Ziquan Yin

Separations 2026, 13(9), 253; https://doi.org/10.3390/separations13090253 - 9 Sep 2026

Shipboard cabins can contain both oil mist-dominated particulate matter and volatile organic compounds (VOCs), creating a need for compact air-cleaning systems capable of simultaneous particle and gas-phase removal. This study developed an integrated filtration–adsorption air cleaner through a performance-oriented route combining a low-resistance [...] Read more.

Shipboard cabins can contain both oil mist-dominated particulate matter and volatile organic compounds (VOCs), creating a need for compact air-cleaning systems capable of simultaneous particle and gas-phase removal. This study developed an integrated filtration–adsorption air cleaner through a performance-oriented route combining a low-resistance gradient filter with an activated-carbon packed bed. The gradient filter maintained PM_2.5 single-pass removal efficiencies above 99.99% across airflow rates of 150–650 m³/h and under inlet concentrations up to approximately 11 mg/m³, while maintaining relatively low airflow resistance. Three activated carbons were also systematically compared based on particle morphology, packed-bed characteristics, pore structure, and dynamic adsorption performance. JZT-07 showed the most favorable overall characteristics and achieved breakthrough capacities of 132, 167, and 159 mg/g for benzene, toluene, and n-heptane, respectively. The selected filtration and adsorption modules were integrated into accommodation- and machinery-cabin air cleaners and evaluated under standard-chamber and shipboard conditions. During treated voyages, average PM₁₀ and TVOC concentrations decreased by 75.3% and 66.4% in the accommodation cabin and by 65.8% and 69.6% in the machinery cabin, respectively. These results demonstrate a practical development route from component optimization to device integration and field validation for simultaneous particulate and VOC control in confined ship environments. Full article

(This article belongs to the Special Issue Development of Novel Porous Adsorbent Materials for Pollutant Removal)

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Open AccessArticle

Adsorptive Removal of Sunscreen-Derived Benzophenone-3 Using Iron-Impregnated Biochar Fabricated with Chlorella pyrenoidosa Biomass

by Yibin Wang, Kai Wang, Jianbu Wang, Zongxing Wang, Xiaofei Yin, Ning Du and Aimin Zhang

Separations 2026, 13(9), 252; https://doi.org/10.3390/separations13090252 - 9 Sep 2026

Benzophenone-3 (BP-3), an organic UV filter extensively applied in sunscreens, cosmetics and daily plastic products, is classified as a typical emerging endocrine-disrupting micropollutant. This compound is highly susceptible to bioaccumulation in aquatic organisms, triggers coral bleaching, and incurs oxidative damage to algae, fish [...] Read more.

Benzophenone-3 (BP-3), an organic UV filter extensively applied in sunscreens, cosmetics and daily plastic products, is classified as a typical emerging endocrine-disrupting micropollutant. This compound is highly susceptible to bioaccumulation in aquatic organisms, triggers coral bleaching, and incurs oxidative damage to algae, fish and invertebrates. Conventional wastewater treatment processes cannot efficiently eliminate BP-3 from aqueous media, thereby imposing severe ecological risks on freshwater and marine ecosystems. In this study, iron-impregnated biochar (Fe-BC) was synthesized via an impregnation–pyrolysis route using powder of cultivated Chlorella pyrenoidosa (green microalga) as raw feedstock. Batch adsorption experiments revealed that iron impregnation remarkably enhanced the removal efficiency of BP-3. The maximum Langmuir saturated adsorption capacity of Fe-BC reached 91.7 mg/g, considerably exceeding the value of 51.5 mg/g for pristine biochar. Kinetic data exhibited favorable fitting with the pseudo-first-order kinetic model, demonstrating that Fe-BC rapidly captures BP-3 and achieves adsorption equilibrium within 120 min. Solution pH exerted a prominent influence on adsorption performance: the material maintained high BP-3 adsorption capacity at pH 7–10, whereas adsorption capacity declined drastically under strongly acidic (pH < 5) and extreme alkaline conditions (pH > 10.5). Fourier-transform infrared spectroscopy (FTIR) validated the successful loading of iron species onto the biochar surface, as well as the binding of BP-3 onto Fe-BC. Combined with pH-controlled experimental results, hydrogen bonding, hydrophobic interactions, and pore-filling effects are inferred as the dominant adsorption mechanisms for BP-3 removal. Furthermore, Fe-BC retained favorable BP-3 removal performance in simulated seawater matrices, endowing it with preliminary potential for wastewater treatment in coastal zones and tourist scenic areas. This work offers basic laboratory insights into BP-3 adsorption, while further verification concerning environmental low-concentration conditions, authentic water matrices, material reusability and stability is essential for its practical application. Full article

(This article belongs to the Special Issue Biological Removal of Emerging Contaminants: Toxicological Effects and Process Mechanisms)

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21 pages, 13483 KB

Open AccessArticle

The Study of Short-Circuit Flow in Gas Cyclones Based on Numerical Simulation

by Yingli Li, Meixi Cui, Xu Ding, Ying Yang, Di Zhang, Jianfei Song and Yaodong Wei

Separations 2026, 13(9), 251; https://doi.org/10.3390/separations13090251 - 3 Sep 2026

Short-circuit flow severely degrades cyclone separation, yet its influence zone has not been clearly defined. In this work, the Reynolds stress model (RSM) was adopted to perform numerical simulations for a 300 mm PV-type cyclone separator, and the simulation results were validated against [...] Read more.

Short-circuit flow severely degrades cyclone separation, yet its influence zone has not been clearly defined. In this work, the Reynolds stress model (RSM) was adopted to perform numerical simulations for a 300 mm PV-type cyclone separator, and the simulation results were validated against published tangential-velocity experimental data. The radial velocity along the extension lines of the vortex finder’s inner wall was analyzed to define the short-circuit flow influence zone, and a sector-resolved intensity index was proposed to quantify its circumferential non-uniformity. The results show that the lower boundary of the influence zone is a circumferentially varying curved surface rather than a horizontal plane. Among the four sectors, the 180–270° sector exhibits the greatest penetration depth (55 mm) and the highest inward radial velocity (−15.45 m/s). The proposed index indicates that Sector III contributes 38.7% of the total short-circuit flow intensity, and the dimensionless index is 0.127 for the present case. Within the influence zone, the inward radial velocity peaks at Z = 12 mm and approaches zero by Z = 53 mm, while the tangential velocity increases from 4.22 to 57.13 m/s, indicating Rankine vortex development. The short-circuit flow is governed by the coupled effects of inlet jet squeezing, vortex-core displacement, and the interaction between upward and downward flows. The proposed influence-zone definition and intensity index provide a quantitative framework for describing short-circuit flow and may be useful for evaluating cyclone design and short-circuit-flow suppression strategies. Full article

(This article belongs to the Special Issue Multiphase Flow Separation Process)

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13 pages, 2254 KB

Open AccessReview

Gallium Extraction Using Surface-Functionalized Carbon-Based Materials: A Mini-Review

by Maqbool Hussain, Liang Zhao, Xusheng Zhang, Hongyu Chen, Yi Cui, Hongxun Zhang, Ruyin Liu and Jianzhong Zheng

Separations 2026, 13(9), 250; https://doi.org/10.3390/separations13090250 - 1 Sep 2026

Gallium is a critical metal for high-tech industries, with its global demand surging in recent years. Currently, approximately 90% of primary gallium is extracted from Bayer liquor. Chelating resins such as amidoxime sorbents are widely adopted commercial materials for this purpose. However, gallium [...] Read more.

Gallium is a critical metal for high-tech industries, with its global demand surging in recent years. Currently, approximately 90% of primary gallium is extracted from Bayer liquor. Chelating resins such as amidoxime sorbents are widely adopted commercial materials for this purpose. However, gallium recovery from such highly caustic media remains a formidable challenge, as gallium is present at low concentrations while aluminate ions are hundreds of times more abundant, and the medium is rich in competing vanadate ions and humic substances. These interfering components impede both adsorption and desorption cycles, leading to a progressive decline in resin performance and a subsequent increase in operational costs. In recent years, functionalized carbon-based materials have gained significant traction. This growing interest is motivated by the carbon-based materials’ exceptional chemical resilience across both acidic and alkaline environments, tunable surface chemistry, and facile re-functionalization. This mini-review synthesizes recent progress in functionalized carbon-based materials for gallium recovery, with a particular emphasis on their adsorption performance and mechanistic insights. At the end of the paper, major challenges and research gaps are identified, and future research directions are proposed. Full article

(This article belongs to the Special Issue Advanced Separation and Extraction of Diverse Metals from Industrial Secondary Resources)

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12 pages, 931 KB

Open AccessFeature PaperArticle

Highly Sensitive LC-MS/MS Method for Determination of Hymexazol Residues in Sugar Beet

by Yujian Wang, Zhengang Liang, Haimin Huang, Zhenfeng Lin and Qingqi Liu

Separations 2026, 13(9), 249; https://doi.org/10.3390/separations13090249 - 31 Aug 2026

This study developed a detection method for hymexazol residues in sugar beet, targeting its low molecular weight, high polarity, and lack of chromophores. The method optimized mass spectrometry conditions, liquid chromatography parameters, and extraction/purification protocols to address the matrix characteristics of sugar beet. [...] Read more.

This study developed a detection method for hymexazol residues in sugar beet, targeting its low molecular weight, high polarity, and lack of chromophores. The method optimized mass spectrometry conditions, liquid chromatography parameters, and extraction/purification protocols to address the matrix characteristics of sugar beet. Specifically, the sample pretreatment involved extraction with acetonitrile, followed by purification using GCB, silica, and C18 sorbents to minimize matrix interference. Sensitivity was enhanced by reducing flow rate and spray voltage. The method demonstrated high performance and was applied to analyze real samples. The LOD and LOQ were theoretically determined to be 1.22 and 3.80 μg/kg, respectively, using the blank standard deviation method. At the spiked levels of 5.0, 10, and 50 μg/kg, the intraday and interday recoveries were 80.2–97.9% and 78.1–101.7%, with corresponding RSDs of 4.8–6.4% and 4.6–8.8%, respectively. These results could meet the requirements for pesticide residue analysis and regulatory monitoring. Full article

(This article belongs to the Topic Application of Chromatography-Mass Spectrometry and Related Techniques, 3rd Edition)

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20 pages, 1216 KB

Open AccessArticle

Optimization and Validation of a QuEChERS-HPLC-DAD Method for the Simultaneous Determination of Benzoic Acid, Sorbic Acid, and Eight Parabens in Diverse Food Matrices

by Duong Huu Huy and Le Thi Ngoc Hanh

Separations 2026, 13(9), 248; https://doi.org/10.3390/separations13090248 - 31 Aug 2026

A simple and efficient QuEChERS-HPLC-DAD method was developed and validated for the simultaneous determination of benzoic acid, sorbic acid, and eight parabens in diverse food matrices. The sample preparation procedure was systematically optimized by evaluating the extraction solvent composition, salting-out conditions, and dispersive [...] Read more.

A simple and efficient QuEChERS-HPLC-DAD method was developed and validated for the simultaneous determination of benzoic acid, sorbic acid, and eight parabens in diverse food matrices. The sample preparation procedure was systematically optimized by evaluating the extraction solvent composition, salting-out conditions, and dispersive solid-phase extraction clean-up to achieve satisfactory recoveries while minimizing matrix interferences. Chromatographic separation was accomplished using isocratic elution on a C18 column with dual-wavelength ultraviolet detection, enabling the simultaneous determination of both authorized preservatives and non-authorized parabens within a single analytical run. The validated method exhibited excellent linearity (R² > 0.996), low to moderate matrix effects (within ±20%), satisfactory recoveries (79–112%), and good precision (RSD < 7.3%), meeting the performance criteria for routine residue analysis. The applicability of the method was demonstrated by analyzing commercial food samples from six food categories. Benzoic acid and sorbic acid were the most frequently detected preservatives, whereas only methylparaben and propylparaben were identified among the investigated parabens. No non-authorized parabens were detected in the analyzed samples. Owing to its simplicity and reliability, the proposed QuEChERS-HPLC-DAD method represents a practical analytical approach for routine multi-matrix monitoring of food preservatives in quality control and food safety laboratories. Full article

(This article belongs to the Section Analysis of Food and Beverages)

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