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Volume 12
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Separations, Volume 12, Issue 8 (August 2025) – 25 articles

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24 pages, 15974 KiB  
Article
Enhancing Copper Leaching from Refractory Copper Oxide Ore Using Organic Cationic Surfactant
by Yang Li, Jue Kou, Chunbao Sun, Peilong Wang and Xiaoli Wang
Separations 2025, 12(8), 212; https://doi.org/10.3390/separations12080212 - 12 Aug 2025
Abstract
The copper oxide ore in Zambia exhibits complex mineralogical characteristics, with copper primarily occurring in mica. The local hydrometallurgical plant employs heating–agitation acid leaching, which is hindered by a low leaching rate and prolonged leaching period, resulting in high energy consumption. To enhance [...] Read more.
The copper oxide ore in Zambia exhibits complex mineralogical characteristics, with copper primarily occurring in mica. The local hydrometallurgical plant employs heating–agitation acid leaching, which is hindered by a low leaching rate and prolonged leaching period, resulting in high energy consumption. To enhance the copper leaching efficiency, a systematic study was conducted on the use of organic cationic surfactants to enhance the leaching of the copper oxide ore. The results indicated that the primary copper-bearing mineral in the raw ore is cupriferous biotite, which is the reason for the difficulty in leaching. Under optimal conditions: a sulfuric acid dosage of 45 kg/t, a CTAB dosage of 75 g/t, a leaching temperature of 65 °C, a liquid-to-solid ratio of 2:1, and a leaching time of 120 min, the copper leaching rate reached 78.32%. Compared to the optimal result of regular heating–agitation acid leaching, this approach increased the copper leaching rate by 3.06%, reduced the leaching time by 80 min, and lowered leaching energy consumption without destroying the structure of cupriferous biotite. Mechanistic studies show that organic cations in CTAB neutralize excess anions, thereby weakening the electrostatic Coulomb forces between the interlayer cations and the hexagonal structure. This increases the interlayer spacing of biotite, facilitating the entry of H+ from sulfuric acid into the interlayer. The H+ then reacts with the copper in the biotite, enhancing the copper leaching rate and reducing leaching time. Because CTAB has high degradability, it will not cause persistent pollution to the environment. The use of CTAB as a leaching aid can reduce the energy consumption of heating–agitation acid leaching and reduce the heating cost per ton of ore by USD 6.11–9.36. Full article
(This article belongs to the Special Issue Advances in Novel Beneficiation Technology of Critical Minerals)
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14 pages, 793 KiB  
Article
Chemometric Fingerprinting of Petroleum Hydrocarbons Within Oil Sands Tailings Using Comprehensive Two-Dimensional Gas Chromatography
by Mike Dereviankin, Lesley Warren and Gregory F. Slater
Separations 2025, 12(8), 211; https://doi.org/10.3390/separations12080211 - 12 Aug 2025
Viewed by 52
Abstract
Base Mine Lake (BML) is the first full-scale demonstration of water-capped tailing technology in a pit lake to reclaim lands impacted by surface mining in the Alberta Oil Sands Region (AOSR). Biogeochemical cycling and/or exchange near the fluid water interface (FWI) of the [...] Read more.
Base Mine Lake (BML) is the first full-scale demonstration of water-capped tailing technology in a pit lake to reclaim lands impacted by surface mining in the Alberta Oil Sands Region (AOSR). Biogeochemical cycling and/or exchange near the fluid water interface (FWI) of the organic-rich fluid fine tailings (FFT) can hinder the reclamation process. To monitor this activity, sedimentary depth profiles were collected from three platforms (P1 to P3) at BML. Seventy-four chromatographically well-resolved petroleum hydrocarbon (PHC) isomers were quantified at each depth interval using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC/TOFMS). The range of total concentrations of all isomers examined across the FFT was the highest at P1 (range = 3.6 × 100–5.5 × 103 ng/g TOC), second highest at P2 (range = 3.8 × 100–1.9 × 103 ng/g TOC), and lowest at P3 (range = 5.6 × 100–7.1 × 102 ng/g TOC). The elevated levels of the same isomers across platforms suggest a consistent source fingerprint. While the source fingerprint was mostly consistent across the platforms and depths, Principal Component Analysis (PCA) identified small differences between geospatial locations caused by variations in specific isomer concentrations. Hierarchical Clustering Analysis (HCA) identified the isomers responsible for the PCA separation, showing that the concentrations of low-molecular-weight n-alkanes (C11–C13) and drimane varied compared to the heavier PHCs with depth. These alkanes are the most biodegradable of the compounds identified in this study, and their variations may reflect biogeochemical cycling within the FFT. Combining these statistical tools provided deeper insight into how isomer concentrations vary with depth, helping to identify possible influences like changing inputs, biogeochemical cycling, and species exchange with the water column. Full article
(This article belongs to the Section Forensics/Toxins)
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12 pages, 1615 KiB  
Article
The Separation of Multiple Trace Impurities in Drugs Using an Improved Twin-Column Recycling Chromatography System
by Junwei Fu and Feng Wei
Separations 2025, 12(8), 210; https://doi.org/10.3390/separations12080210 - 11 Aug 2025
Viewed by 110
Abstract
The acquisition of high-purity impurities is pivotal for structural identification and an origin analysis, thereby laying a critical foundation for subsequent toxicological evaluation, quality standard development, and process optimization. This study investigated the feasibility of using a solvent gradient twin-column recycling chromatography technique [...] Read more.
The acquisition of high-purity impurities is pivotal for structural identification and an origin analysis, thereby laying a critical foundation for subsequent toxicological evaluation, quality standard development, and process optimization. This study investigated the feasibility of using a solvent gradient twin-column recycling chromatography technique for the separation and purification of multiple trace impurities in iohexol. In this approach, a modifier with a weaker elution strength than the mobile phase is introduced between two chromatographic columns to form a step gradient solvent system. This gradient slows down the leading edge of the elution band relative to the rear edge, inducing a band compression effect that counteracts band broadening and enhances the chromatographic resolution. By optimizing parameters such as the mobile phase composition, elution mode, and modifier flow rate, three trace impurities were successfully separated and purified from iohexol. Their respective purities were improved from initial concentrations of 0.36%, 0.35%, and 0.15% to 97.82%, 91.56%, and 81.56%, respectively. Leveraging the band compression effect on the target components, the impurities were simultaneously purified and concentrated. These results demonstrate that the proposed method is highly effective for the rapid isolation and preparation of trace pharmaceutical impurities. Full article
(This article belongs to the Section Chromatographic Separations)
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22 pages, 2597 KiB  
Article
Valorization of the Bioactive Potential of Juniperus communis L. Berry Extracts Using a Box–Behnken Design and Characterization of Kernel Oil Compounds
by Theofania Tsitsirigka, Dimitrios Kalompatsios, Vassilis Athanasiadis, Eleni Bozinou, Athanassios I. Sfougaris and Stavros I. Lalas
Separations 2025, 12(8), 209; https://doi.org/10.3390/separations12080209 - 11 Aug 2025
Viewed by 132
Abstract
This study presents a comprehensive valorization of Juniperus communis L., a plant known for its culinary and therapeutic applications. Juniper berries are rich in antioxidant compounds such as polyphenols and ascorbic acid, while their kernels contain volatile terpenes with notable pharmaceutical properties. We [...] Read more.
This study presents a comprehensive valorization of Juniperus communis L., a plant known for its culinary and therapeutic applications. Juniper berries are rich in antioxidant compounds such as polyphenols and ascorbic acid, while their kernels contain volatile terpenes with notable pharmaceutical properties. We optimized extraction parameters through stirring extraction (1:20 g/mL solid-to-solvent ratio, 55% v/v aqueous ethanol, 80 °C, 30 min) and response surface methodology via a Box–Behnken design. The optimal conditions—55% v/v aqueous ethanol at 80 °C for 30 min—yielded a high polyphenol content of 55.11 ± 1.54 mg GAE/g of defatted dry weight. Antioxidant capacity was confirmed through ferric-reducing and radical-scavenging assays, and 11 individual polyphenols (totaling 5.41 ± 0.27 mg/g) were quantified using a validated HPLC-DAD method. Additionally, this study identified several bioactive compounds in juniper berry raw kernel oil, which exhibited a high oleic acid content (58.75 ± 2.76%)—a nutritionally valuable fatty acid contributing to the oil’s strong radical-scavenging activity (399.83 ± 34.18 µmol Trolox equivalents/kg oil). GC–MS analysis revealed 58 volatile compounds, underscoring the terpene-rich profile of the oil and its influence on antioxidant potential and aroma. These findings underscore the dual valorization of juniper berry fruit and kernel for both medicinal and food industries. The aromatic kernel oil and polyphenol-rich extracts offer natural alternatives to synthetic antioxidants, with added benefits of flavor enhancement and promotion of health. Full article
(This article belongs to the Special Issue Advances in the Analysis of Bioactive Plant Extracts: Separation Techniques and Their Applications)
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10 pages, 2339 KiB  
Article
Molluscicidal Activity of the Crude Extract and Fractions of Myrsine parvifolia
by Keyla Nunes Farias Gomes, Leonardo da Silva Rangel, João Claudio Vitoria Ático Leite, Gabriel Rocha Caldas, Arthur Luiz Corrêa, Marcelo Guerra Santos, Leandro Machado Rocha, José Augusto Albuquerque dos Santos and Robson Xavier Faria
Separations 2025, 12(8), 208; https://doi.org/10.3390/separations12080208 - 11 Aug 2025
Viewed by 116
Abstract
As the second most common infectious parasitic disease in the world, schistosomiasis is present in Brazil, mainly in the Northeast and Southeast regions. Currently, the recommended form of prevention is controlling this disease’s intermediate host, mollusks of the Biomphalaria genus, using the chemical [...] Read more.
As the second most common infectious parasitic disease in the world, schistosomiasis is present in Brazil, mainly in the Northeast and Southeast regions. Currently, the recommended form of prevention is controlling this disease’s intermediate host, mollusks of the Biomphalaria genus, using the chemical molluscicide Bayluscide WP 70®. This synthetic molluscicide is expensive, has low selectivity for Biomphalaria glabrata species, and is toxic to the environment. In this context, the use of natural products such as molluscicides represents a sustainable control method. The objective of this study was to evaluate the molluscicidal effects of a crude ethanolic extract of the leaves and stems and fractions of the species Myrsine parvifolia on the mollusk Biomphalaria glabrata. Methods: The methodology was adapted from standards defined by the World Health Organization (WHO), where the molluscicidal activity of Myrsine parvifolia was investigated as an alternative for the population control of Biomphalaria glabrata and That’s right. environmental toxicity was evaluated using the Physella sp. The results revealed that the stem ethanolic crude extract exhibited activity after 24 h of exposure, with an LC50 of 207.4 mg/L and an LC90 of 256.2 mg/L. Conclusions: Myrsine parvifolia can be used as a sustainable biological alternative for the population control of Biomphalaria glabrata snails, especially for poor populations and inaccessible regions. Full article
(This article belongs to the Special Issue Advanced Research on Extraction and Analysis of Plant Extracts)
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18 pages, 3921 KiB  
Article
Ion-Exchange Membrane Permselectivity: Experimental Evaluation of Concentration Dependence, Ionic Species Selectivity, and Temperature Response
by Junyi Lv, Xiaojing Zhu, Xi Wu and Hongfei Guan
Separations 2025, 12(8), 207; https://doi.org/10.3390/separations12080207 - 9 Aug 2025
Viewed by 78
Abstract
Ion-exchange membranes (IEMs) are widely used in reverse-electrodialysis (RED) technology, which can collect the salinity gradient energy between concentrated and diluted solutions and convert it into electromotive force (EMF) to drive power generation and hydrogen production. Recent studies have indicated that the permselectivity [...] Read more.
Ion-exchange membranes (IEMs) are widely used in reverse-electrodialysis (RED) technology, which can collect the salinity gradient energy between concentrated and diluted solutions and convert it into electromotive force (EMF) to drive power generation and hydrogen production. Recent studies have indicated that the permselectivity of IEMs is vital to determining the performance of an RED stack. In this study, the influences of solution concentration, ion species, and solution temperature on the permselectivity of IEMs were experimentally investigated. The results demonstrate that the permselectivity of IEMs decreases with increasing concentrations of KAc, LiCl, and LiBr solutions for both concentrated solutions (3–5 M) and dilute solutions (0.02–0.2 M). Further, through comparing the LiBr and KBr solutions as well as the LiCl, KCl, and NH4Cl solutions, respectively, K+ demonstrates a higher permselectivity than Li+, and both of which are smaller than NH4+ under the same cation and concentration conditions. Moreover, another test was conducted using three potassium salt solutions with different anions, and the experimental permselectivity order is Ac− > Br− > Cl−. A slight increase in solution temperature enhances the permselectivity of IEMs due to the increase in ionic mobility. However, an excessive temperature is detrimental to membrane stability and thus reduces permselectivity. It can be seen that ions with low hydration energy, a small hydration radius, and high mobility show a higher permselectivity. Full article
(This article belongs to the Section Purification Technology)
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21 pages, 3287 KiB  
Article
Experimental and Quantum Mechanical Studies of Efficient Re(VII)/Mo(VI) Separation by a Magnetic Amino-Functionalized Polymer
by Bojana Marković, Goran Janjić, Antonije Onjia, Tamara Tadić, Plamen Stefanov and Aleksandra Nastasović
Separations 2025, 12(8), 206; https://doi.org/10.3390/separations12080206 - 7 Aug 2025
Viewed by 223
Abstract
A previously synthesized and functionalized magnetic glycidyl methacrylate-based nanocomposite, mPGMT-deta, was tested as a sorbent for Re(VII) oxoanions in Mo(VI)-containing solutions. The effect of pH on the removal efficiency and the separation factor was examined in the range of 2 to 9. A [...] Read more.
A previously synthesized and functionalized magnetic glycidyl methacrylate-based nanocomposite, mPGMT-deta, was tested as a sorbent for Re(VII) oxoanions in Mo(VI)-containing solutions. The effect of pH on the removal efficiency and the separation factor was examined in the range of 2 to 9. A maximum separation factor (βRe/Mo) of 8.85 was observed at pH 6. The nature of rhenium oxoanions binding to the active sites of mPGMT-deta was analyzed using density functional theory (DFT). The calculations indicated that the formation of MoO42−//hedetaH22+ adduct is electrostatically favored at pH 6, while the inclusion of solvation effects makes the formation of ReO4−//hedetaH22+ adduct thermodynamically more favorable. Solvation played a dominant role in determining the selectivity of oxoanion sorption to the nanocomposite. The adsorption isotherm, kinetics, and thermodynamics of Re(VII) onto mPGMT-deta were determined. The equilibrium data were best-fitted using the Langmuir adsorption model (R2 = 0.999), with a maximum sorption capacity for Re(VII) of 0.43 mmol/g. The uptake kinetics of the sorption process obeyed the pseudo-second-order model, with the influence of diffusion and external mass transfer. Based on the thermodynamic parameters, Re(VII) sorption was spontaneous and endothermic. Full article
(This article belongs to the Special Issue New and Modified Polymers for Detection and Removal of Pollutants from Water and Air)
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18 pages, 4475 KiB  
Article
Preparation of EDTA-2Na-Fe3O4-Activated Carbon Composite and Its Adsorption Performance for Typical Heavy Metals
by Yannan Lv, Shenrui Han, Wenqing Wen, Xinzhu Bai, Qiao Sun, Li Chen, Haonan Zhang, Fansong Mu and Meng Luo
Separations 2025, 12(8), 205; https://doi.org/10.3390/separations12080205 - 6 Aug 2025
Viewed by 174
Abstract
This study developed a new magnetic adsorbent from waste coconut shells using high-temperature carbonization, EDTA-2Na chelation, and Fe3O4 magnetic loading. Response surface methodology optimized the preparation conditions to a mass ratio of activated carbon: EDTA-2Na:Fe3O4 = 2:0.6:0.2. [...] Read more.
This study developed a new magnetic adsorbent from waste coconut shells using high-temperature carbonization, EDTA-2Na chelation, and Fe3O4 magnetic loading. Response surface methodology optimized the preparation conditions to a mass ratio of activated carbon: EDTA-2Na:Fe3O4 = 2:0.6:0.2. Characterization (SEM, XRD, FT-IR, and EDS) showed that EDTA-2Na increased the surface carboxyl and amino group density, while Fe3O4 loading (Fe concentration 6.83%) provided superior magnetic separation performance. The optimal adsorption conditions of Cu2+ by EDTA-2Na-Fe3O4-activated carbon composite material are as follows: when pH = 5.0 and the initial concentration is 180 mg/L, the equilibrium adsorption capacity reaches 174.96 mg/g, and the removal rate reaches 97.2%. The optimal adsorption conditions for Pb2+ are as follows: when pH = 6.0 and the initial concentration is 160 mg/L, the equilibrium adsorption capacity reaches 157.60 mg/g, and the removal rate reaches 98.5%. The optimal adsorption conditions for Cd2+ are pH = 8.0 and an initial concentration of 20 mg/L. The equilibrium adsorption capacity reaches 18.76 mg/g, and the removal rate reaches 93.8%. The adsorption followed the pseudo-second-order kinetics (R2 > 0.95) and Langmuir/Freundlich isotherm models, indicating chemisorption dominance. Desorption experiments using 0.1 mol/L HCl and EDTA-2Na achieved efficient desorption (>85%), and the material retained over 80% of its adsorption capacity after five cycles. This cost-effective and sustainable adsorbent offers a promising solution for heavy metal wastewater treatment. Full article
(This article belongs to the Special Issue Application of Advanced Materials and Technologies in the Separation and Adsorption)
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20 pages, 462 KiB  
Article
Chromatographic and Chemometric Characterization of the Two Wild Edible Mushrooms Fistulina hepatica and Clitocybe nuda: Insights into Nutritional, Phenolic, and Antioxidant Profiles
by Ana Saldanha, Mikel Añibarro-Ortega, Adriana K. Molina, José Pinela, Maria Inês Dias and Carla Pereira
Separations 2025, 12(8), 204; https://doi.org/10.3390/separations12080204 - 2 Aug 2025
Viewed by 322
Abstract
Fistulina hepatica (Schaeff.) With. and Clitocybe nuda (Bull.) H.E. Bigelow & A.H. Sm. are wild edible mushrooms with nutritional and functional potential that remain insufficiently characterized. This study provides the first comparative assessment of their nutritional profiles, phenolic composition, and antioxidant activity, using [...] Read more.
Fistulina hepatica (Schaeff.) With. and Clitocybe nuda (Bull.) H.E. Bigelow & A.H. Sm. are wild edible mushrooms with nutritional and functional potential that remain insufficiently characterized. This study provides the first comparative assessment of their nutritional profiles, phenolic composition, and antioxidant activity, using specimens collected from Montesinho Natural Park (Portugal). Proximate composition, organic and phenolic acids, free sugars, and fatty acids were analyzed by chromatographic methods, and antioxidant capacity was assessed through OxHLIA and TBARS assays. F. hepatica showed higher carbohydrates (9.3 ± 0.2 g/100 g fw) and estimated energy values (43 ± 1 kcal/100 g fw), increased phenolic acids content (2.7 ± 0.1 mg/g extract), and the exclusive presence of p-coumaric and cinnamic acids, along with OxHLIA activity (IC50 = 126 ± 5 µg/mL at Δt = 60 min). C. nuda displayed higher protein (2.5 ± 0.1 g/100 g dw) and quinic acid contents (4.13 ± 0.02 mg/g extract), a PUFA-rich profile, and greater TBARS inhibition (EC50 = 303 ± 17 µg/mL). These findings highlight distinct and complementary bioactive traits, supporting their valorization as natural functional ingredients. Their compositional features offer promising applications in sustainable food systems and nutraceutical development, encouraging further investigations into safety, bioaccessibility, and formulation strategies. Notably, F. hepatica is best consumed at a young developmental stage, as its sensory properties tend to decline with maturity. Full article
(This article belongs to the Special Issue Advanced Separation Methods for Safety Assessment and Valorization of By-Products)
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23 pages, 2888 KiB  
Review
Machine Learning in Flocculant Research and Application: Toward Smart and Sustainable Water Treatment
by Caichang Ding, Ling Shen, Qiyang Liang and Lixin Li
Separations 2025, 12(8), 203; https://doi.org/10.3390/separations12080203 - 1 Aug 2025
Viewed by 306
Abstract
Flocculants are indispensable in water and wastewater treatment, enabling the aggregation and removal of suspended particles, colloids, and emulsions. However, the conventional development and application of flocculants rely heavily on empirical methods, which are time-consuming, resource-intensive, and environmentally problematic due to issues such [...] Read more.
Flocculants are indispensable in water and wastewater treatment, enabling the aggregation and removal of suspended particles, colloids, and emulsions. However, the conventional development and application of flocculants rely heavily on empirical methods, which are time-consuming, resource-intensive, and environmentally problematic due to issues such as sludge production and chemical residues. Recent advances in machine learning (ML) have opened transformative avenues for the design, optimization, and intelligent application of flocculants. This review systematically examines the integration of ML into flocculant research, covering algorithmic approaches, data-driven structure–property modeling, high-throughput formulation screening, and smart process control. ML models—including random forests, neural networks, and Gaussian processes—have successfully predicted flocculation performance, guided synthesis optimization, and enabled real-time dosing control. Applications extend to both synthetic and bioflocculants, with ML facilitating strain engineering, fermentation yield prediction, and polymer degradability assessments. Furthermore, the convergence of ML with IoT, digital twins, and life cycle assessment tools has accelerated the transition toward sustainable, adaptive, and low-impact treatment technologies. Despite its potential, challenges remain in data standardization, model interpretability, and real-world implementation. This review concludes by outlining strategic pathways for future research, including the development of open datasets, hybrid physics–ML frameworks, and interdisciplinary collaborations. By leveraging ML, the next generation of flocculant systems can be more effective, environmentally benign, and intelligently controlled, contributing to global water sustainability goals. Full article
(This article belongs to the Section Environmental Separations)
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17 pages, 3206 KiB  
Article
Inverse Punicines: Isomers of Punicine and Their Application in LiAlO2, Melilite and CaSiO3 Separation
by Maximilian H. Fischer, Ali Zgheib, Iliass El Hraoui, Alena Schnickmann, Thomas Schirmer, Gunnar Jeschke and Andreas Schmidt
Separations 2025, 12(8), 202; https://doi.org/10.3390/separations12080202 - 30 Jul 2025
Viewed by 192
Abstract
The transition to sustainable energy systems demands efficient recycling methods for critical raw materials like lithium. In this study, we present a new class of pH- and light-switchable flotation collectors based on isomeric derivatives of the natural product Punicine, termed inverse Punicines. [...] Read more.
The transition to sustainable energy systems demands efficient recycling methods for critical raw materials like lithium. In this study, we present a new class of pH- and light-switchable flotation collectors based on isomeric derivatives of the natural product Punicine, termed inverse Punicines. These amphoteric molecules were synthesized via a straightforward four-step route and structurally tuned for hydrophobization by alkylation. Their performance as collectors was evaluated in microflotation experiments of lithium aluminate (LiAlO2) and silicate matrix minerals such as melilite and calcium silicate. Characterization techniques including ultraviolet-visible (UV-Vis), nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectroscopy as well as contact angle, zeta potential (ζ potential) and microflotation experiments revealed strong pH- and structure-dependent interactions with mineral surfaces. Notably, N-alkylated inverse Punicine derivatives showed high flotation yields for LiAlO2 at pH of 11, with a derivative possessing a dodecyl group attached to the nitrogen as collector achieving up to 86% recovery (collector conc. 0.06 mmol/L). Preliminary separation tests showed Li upgrading from 5.27% to 6.95%. Radical formation and light-response behavior were confirmed by ESR and flotation tests under different illumination conditions. These results demonstrate the potential of inverse Punicines as tunable, sustainable flotation reagents for advanced lithium recycling from complex slag systems. Full article
(This article belongs to the Special Issue Application of Green Flotation Technology in Mineral Processing)
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17 pages, 2627 KiB  
Article
Cuscohygrine and Hygrine as Biomarkers for Coca Leaf Chewing: Analytical Challenges in GC-MS Detection and Implications for the Differentiation of Cocaine Use in Forensic Toxicology
by Nélida C. Rubio, Iván Alvarez-Freire, Pamela Cabarcos-Fernández, María J. Tabernero-Duque, Inés Sánchez-Sellero, Antonio Moreda-Piñeiro, Pilar Bermejo-Barrera and Ana M. Bermejo-Barrera
Separations 2025, 12(8), 201; https://doi.org/10.3390/separations12080201 - 30 Jul 2025
Viewed by 238
Abstract
Cuscohygrine (CUS) and hygrine (HYG) are pyrrolidine alkaloids proposed as biomarkers of coca leaf consumption, a culturally accepted practice in some Latin American countries. Differentiating legal coca use from illicit cocaine consumption holds forensic importance. While LC-MS/MS is preferred, GC-MS remains widely used [...] Read more.
Cuscohygrine (CUS) and hygrine (HYG) are pyrrolidine alkaloids proposed as biomarkers of coca leaf consumption, a culturally accepted practice in some Latin American countries. Differentiating legal coca use from illicit cocaine consumption holds forensic importance. While LC-MS/MS is preferred, GC-MS remains widely used in Latin American toxicology labs due to accessibility. This study critically evaluates the analytical limitations of GC-MS for detecting CUS and HYG in biological matrices. Key parameters—injector temperature (180–290 °C), injection mode (split/splitless), solvent, liner condition, and matrix—were systematically studied. GC-MS showed significant limitations: low-abundance, non-specific fragments (m/z 42, 84, 98, 140) failed to meet the identification criteria in SIM mode. Thermal degradation of CUS to HYG and CUS-d6 to HYG-d3 was observed, especially with splitless injection and aged liners. Matrix effects produced signal enhancement ranging from +29% to +316%, meaning that analyte responses in biological samples were significantly higher than in neat standards, likely due to reduced degradation or adsorption. Although deuterated internal standards (CUS-d6) partially corrected signal variability and matrix enhancement, these corrections were not sufficient to overcome the fundamental limitations of GC-MS, including poor ion specificity and compound instability. These findings support the need for LC-MS/MS-based approaches for reliable alkaloid detection and question the suitability of GC-MS for CUS analysis in forensic toxicology contexts. Full article
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11 pages, 1070 KiB  
Article
Directed Message-Passing Neural Networks for Gas Chromatography
by Daniel Struk, Rizky Ilhamsyah, Jean-Marie D. Dimandja and Peter J. Hesketh
Separations 2025, 12(8), 200; https://doi.org/10.3390/separations12080200 - 30 Jul 2025
Viewed by 265
Abstract
In this paper, the directed message-passing neural network architecture is used to predict several quantities of interest in gas chromatography: retention times, Clarke-Glew 3-point thermodynamic parameters for simulation, and retention indices. The retention index model was trained with 48,803 training samples and reached [...] Read more.
In this paper, the directed message-passing neural network architecture is used to predict several quantities of interest in gas chromatography: retention times, Clarke-Glew 3-point thermodynamic parameters for simulation, and retention indices. The retention index model was trained with 48,803 training samples and reached 1.9–2.6% accuracy, whereas the thermodynamic parameters and retention time were trained by using 230 training data samples yielding 17% accuracy. Furthermore, the accuracy as a function of the number of training samples is investigated, showing the necessity of large, accurate datasets for training deep learning-based models. Lastly, several uses of such a model for the identification of compounds and the optimization of GC parameters are discussed. Full article
(This article belongs to the Special Issue State of the Art and Challenges in the Analysis of Volatile Organic Compounds)
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17 pages, 3944 KiB  
Article
Functionalized Magnetic Nanoparticles as Recyclable Draw Solutes for Forward Osmosis: A Sustainable Approach to Produced Water Reclamation
by Sunith B. Madduri and Raghava R. Kommalapati
Separations 2025, 12(8), 199; https://doi.org/10.3390/separations12080199 - 29 Jul 2025
Viewed by 380
Abstract
Magnetic nanoparticles (MNPs), especially iron oxide (Fe3O4), display distinctive superparamagnetic characteristics and elevated surface-area-to-volume ratios, facilitating improved physicochemical interactions with solutes and pollutants. These characteristics make MNPs strong contenders for use in water treatment applications. This research investigates the [...] Read more.
Magnetic nanoparticles (MNPs), especially iron oxide (Fe3O4), display distinctive superparamagnetic characteristics and elevated surface-area-to-volume ratios, facilitating improved physicochemical interactions with solutes and pollutants. These characteristics make MNPs strong contenders for use in water treatment applications. This research investigates the application of iron oxide MNPs synthesized via co-precipitation as innovative draw solutes in forward osmosis (FO) for treating synthetic produced water (SPW). The FO membrane underwent surface modification with sulfobetaine methacrylate (SBMA), a zwitterionic polymer, to increase hydrophilicity, minimize fouling, and elevate water flux. The SBMA functional groups aid in electrostatic repulsion of organic and inorganic contaminants, simultaneously encouraging robust hydration layers that improve water permeability. This adjustment is vital for sustaining consistent flux performance while functioning with MNP-based draw solutions. Material analysis through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) verified the MNPs’ thermal stability, consistent morphology, and modified surface chemistry. The FO experiments showed a distinct relationship between MNP concentration and osmotic efficiency. At an MNP dosage of 10 g/L, the peak real-time flux was observed at around 3.5–4.0 L/m2·h. After magnetic regeneration, 7.8 g of retrieved MNPs generated a steady flow of ~2.8 L/m2·h, whereas a subsequent regeneration (4.06 g) resulted in ~1.5 L/m2·h, demonstrating partial preservation of osmotic driving capability. Post-FO draw solutions, after filtration, exhibited total dissolved solids (TDS) measurements that varied from 2.5 mg/L (0 g/L MNP) to 227.1 mg/L (10 g/L MNP), further validating the effective dispersion and solute contribution of MNPs. The TDS of regenerated MNP solutions stayed similar to that of their fresh versions, indicating minimal loss of solute activity during the recycling process. The combined synergistic application of SBMA-modified FO membranes and regenerable MNP draw solutes showcases an effective and sustainable method for treating produced water, providing excellent water recovery, consistent operational stability, and opportunities for cyclic reuse. Full article
(This article belongs to the Section Purification Technology)
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14 pages, 1663 KiB  
Article
Carbon Dioxide Absorption by Polyethylene Glycol Dimethyl Ether Modified by 2-methylimidazole
by Yan Wu, Zicheng Wang, Hui Yu, Bin Ding, Ke Fei, Xueli Ma, Baoshen Xu, Yonghu Zhang, Xiaoning Fu, Bowen Ding and Nan Li
Separations 2025, 12(8), 198; https://doi.org/10.3390/separations12080198 - 28 Jul 2025
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Abstract
Developing and utilizing capture and storage technologies for CO2 has become a critical research topic due to the significant greenhouse effect caused by excessive CO2 emissions. A conventional physical absorption process for CO2 capture is polyethylene glycol dimethyl ether (NHD); [...] Read more.
Developing and utilizing capture and storage technologies for CO2 has become a critical research topic due to the significant greenhouse effect caused by excessive CO2 emissions. A conventional physical absorption process for CO2 capture is polyethylene glycol dimethyl ether (NHD); however, its limited application range is caused by its poor absorption of CO2 at low pressures. In this work, the CO2 absorption of NHD was enhanced by combining NHD with a novel chemical absorbent 2-methylimidazole (2-mIm)-ethylene glycol (EG) solution to improve CO2 absorption. Viscosity and CO2 solubility were examined in various compositions. The CO2 solubility in the mixed solution was found to be at maximum when the mass fractions of NHD, 2-mIm, and EG were 20%, 40%, and 40%, respectively. In comparison to pure NHD, the solubility of CO2 in this mixed solution at 30 °C and 0.5 MPa increased by 161.2%, and the desorption heat was less than 30 kJ/mol. The complex solution exhibits high selectivity and favorable regeneration performance in the short term. However, it is more sensitive to moisture content. The results of this study can provide important data to support the construction of new low-energy solvent systems and the development of novel CO2 capture processes. Full article
(This article belongs to the Section Separation Engineering)
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19 pages, 2475 KiB  
Article
Efficient Extraction of 1,2-Dichloroethane from Wastewater Using Hydrophobic Deep Eutectic Solvents: A Green Approach
by Irfan Wazeer, Abdullah Omair, Lahssen El Blidi, Salim Mokraoui, Emad Ali and Mohamed K. Hadj-Kali
Separations 2025, 12(8), 197; https://doi.org/10.3390/separations12080197 - 27 Jul 2025
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Abstract
This study provides a thorough examination of the utilization of hydrophobic deep eutectic solvents (HDESs) for the extraction of 1,2-dichloroethane (1,2-DCA) from effluent, with an emphasis on a sustainable and environmentally friendly approach. The extraction efficacy of six HDES systems was initially evaluated, [...] Read more.
This study provides a thorough examination of the utilization of hydrophobic deep eutectic solvents (HDESs) for the extraction of 1,2-dichloroethane (1,2-DCA) from effluent, with an emphasis on a sustainable and environmentally friendly approach. The extraction efficacy of six HDES systems was initially evaluated, and the combinations of thymol/camphor (Thy/Cam) and menthol/thymol (Men/Thy) exhibited superior performance. Subsequently, these two HDESs were chosen for a comprehensive parametric analysis. The impact of contact time demonstrated that extraction equilibrium was reached at 15 min for both systems, thereby achieving a balance between high efficiency and time efficiency. Next, the impact of the HDES-to-water mass ratio was investigated. A 1:1 ratio was determined to be the most effective, as it minimized solvent consumption and provided high efficiency. An additional examination of the molar ratios of the HDES components revealed that the 1:1 ratio exhibited the most effective extraction performance. This was due to the fact that imbalances in the solvent mixture resulted in diminished efficiency as a result of disrupted molecular interactions. The extraction efficiency was significantly influenced by the initial concentration of 1,2-DCA, with higher concentrations resulting in superior results as a result of the increased mass transfer driving forces. In general, the Men/Thy and Thy/Cam systems have shown noteworthy stability and efficiency under different conditions, which makes them highly suitable for large-scale applications. Full article
(This article belongs to the Special Issue Green Separation and Purification Technology)
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27 pages, 1893 KiB  
Article
Separating 2-Propanol and Water: A Comparative Study of Extractive Distillation, Salting-Out, and Extraction
by Aleksandra Sander, Marko Rogošić, Leonarda Frljak, Daniela Vasiljević, Iva Blažević and Jelena Parlov Vuković
Separations 2025, 12(8), 196; https://doi.org/10.3390/separations12080196 - 26 Jul 2025
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Abstract
Separating azeotropes is an important, difficult, and expensive task, in particular for the 2-propanol–water mixture. The literature on the problem is rich in modeling studies but often lacking even the simplest experimental confirmation. In this paper, extractive distillation, liquid–liquid equilibrium-based extraction, and salting-out [...] Read more.
Separating azeotropes is an important, difficult, and expensive task, in particular for the 2-propanol–water mixture. The literature on the problem is rich in modeling studies but often lacking even the simplest experimental confirmation. In this paper, extractive distillation, liquid–liquid equilibrium-based extraction, and salting-out were experimentally tested for the desired separation. Among the four tested extractive distillation entrainers, none was able—in the investigated experimental setup—to push the system over the azeotropic composition threshold. Four novel hydrophobic deep eutectic extraction media were tested for the desired separation, and those based on menthol or thymol with decanoic acid were found most promising. Among 16 tested salting-out agents, 5 of them produced two-liquid phases, and only 4 hydrophilic inorganic salts promoted 2-propanol separation, with sodium carbonate being the most promising candidate. The purity of the products was tested with FTIR and 1H-NMR. The experimental findings were compared with COSMO-RS model predictions, with moderate success. Full article
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23 pages, 1784 KiB  
Article
Study on the Adsorption Characteristics of Spirulina Dry Powder Biomass for Rare Earth Element Praseodymium(III): Adsorption Isotherms, Kinetics, and Thermodynamics Analysis
by Zhenxiang Hu, Caixia Zhang and Qing Shu
Separations 2025, 12(8), 195; https://doi.org/10.3390/separations12080195 - 25 Jul 2025
Viewed by 382
Abstract
Aimed at developing an economical and efficient biosorbent for the adsorption and separation of rare earth ions, this study employed Spirulina dry powder biomass as a biosorbent to investigate its removal performance for Pr3+ in aqueous solutions. Experimental results demonstrated that under [...] Read more.
Aimed at developing an economical and efficient biosorbent for the adsorption and separation of rare earth ions, this study employed Spirulina dry powder biomass as a biosorbent to investigate its removal performance for Pr3+ in aqueous solutions. Experimental results demonstrated that under optimized conditions (pH = 5, adsorbent dosage = 2.0 g/L, initial Pr3+ concentration = 100 mg/L, and adsorption time = 60 min), the removal efficiency of Pr3+ reached 79.0%. FT-IR and XPS characterization confirmed the participation of various functional groups on the Spirulina surface in the adsorption process. When 0.1 mol/L HNO3 was used as the desorption agent, the desorption rate of Pr3+ from Spirulina reached 91.7%, demonstrating excellent regeneration performance. At different temperatures (298–318 K), the adsorption data were fitted using Langmuir, Freundlich, Dubinin–Radushkevich, and Redlich–Peterson models. Among them, the Langmuir model (R2 ranged from 0.993 to 0.999) provided the best fit, and the adsorption capacity of Spirulina for Pr3+ was in the range of 51.10 to 55.31 mg/g. Kinetic studies revealed that the pseudo-second-order model (R2 = 0.999) best described the adsorption process, with a rate constant of 0.054 g/(mg·min) (R2 was 0.999) at an initial Pr3+ concentration of 300 mg/L, indicating chemisorption-controlled behavior. Thermodynamic parameter analysis showed that within the experimental temperature range, ΔG0 < 0 and ΔS0 > 0, confirming that the adsorption process was spontaneous and endothermic. This study provides a novel technical approach for the green recovery of rare earth elements and highlights the potential of Spirulina biomass in rare earth resource recycling. Full article
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14 pages, 4700 KiB  
Article
Pilot-Scale Phycocyanin Extraction by the Green Two-Step Ultrasound-Based UltraBlu Process
by Rosaria Lauceri, Melissa Pignataro, Antonio Giorgi, Antonio Idà and Lyudmila Kamburska
Separations 2025, 12(8), 194; https://doi.org/10.3390/separations12080194 - 25 Jul 2025
Viewed by 209
Abstract
Phycocyanin is a natural, non-toxic, blue pigment-protein with many commercial applications. Its exploitation in various biotechnological sectors strongly depends on its purity grade (P). Phycocyanin is largely used in food industry where a low purity grade is required, while its widespread use in [...] Read more.
Phycocyanin is a natural, non-toxic, blue pigment-protein with many commercial applications. Its exploitation in various biotechnological sectors strongly depends on its purity grade (P). Phycocyanin is largely used in food industry where a low purity grade is required, while its widespread use in sectors requiring a higher purity is hampered by the cost of large-scale industrial production. Industry, in fact, needs simple, easily scalable and cost-effective procedures to ensure sustainable production of high-quality pigment. In this work we applied the innovative two-step ultrasound-based process UltraBlu to the pilot-scale production of phycocyanin. A total of 50 L of biomass suspension of commercial Spirulina were processed in batch mode. The pigment extract was obtained in one day, including the biomass harvesting. Food/cosmetic grade (P = 1.41–1.76) and a good yield (Y = 59.2–76.1%) were achieved. The initial results obtained suggest that UltraBlu can be an effective scalable process suitable to produce phycocyanin also on an industrial scale. Full article
(This article belongs to the Special Issue Application of Sustainable Separation Techniques in Food Processing)
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14 pages, 4274 KiB  
Article
The Role of Freezing Temperature in Modulating Chitosan Gel Structure and Evaporation Performance for Seawater Desalination
by Jiaonan Cai, Yong Bai and Fang Li
Separations 2025, 12(8), 193; https://doi.org/10.3390/separations12080193 - 24 Jul 2025
Viewed by 312
Abstract
Interfacial solar evaporation has emerged as a promising strategy for freshwater production, where 3D evaporators offer distinct advantages in heat management and salt rejection. Freeze–thaw cycling is a widely adopted fabrication method for 3D hydrogel evaporators, yet the impact of preparation conditions (e.g., [...] Read more.
Interfacial solar evaporation has emerged as a promising strategy for freshwater production, where 3D evaporators offer distinct advantages in heat management and salt rejection. Freeze–thaw cycling is a widely adopted fabrication method for 3D hydrogel evaporators, yet the impact of preparation conditions (e.g., freezing temperature) on their evaporation performance remains poorly understood, hindering rational optimization of fabrication protocols. Herein, we report the fabrication of chitosan-based hydrogel evaporators via freeze–thaw cycles at different freezing temperatures (−20 °C, −40 °C, and −80 °C), leveraging its low cost and environmental friendliness. Characterizations of crosslinking density and microstructure reveal a direct correlation between freezing temperature and network porosity, which significantly influences evaporation rate, photothermal conversion efficiency, and anti-salt performance. It is noteworthy that the chitosan hydrogel prepared at −80 °C demonstrates an excellent evaporation rate in high-salinity environments and exhibits superior salt resistance during continuous evaporation testing. Long-term cyclic experiments indicate that there was an average evaporation rate of 3.76 kg m−2 h−1 over 10 cycles, with only a 2.5% decrease observed in the 10th cycle. This work not only elucidates the structure–property relationship of freeze–thaw fabricated hydrogels but also provides a strategic guideline for tailoring evaporator architectures to different salinity conditions, bridging the gap between material design and practical seawater desalination. Full article
(This article belongs to the Collection Feature Paper Collection in Section 'Materials in Separation Science')
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21 pages, 727 KiB  
Article
Seasonal and Cultivar-Dependent Phenolic Dynamics in Tuscan Olive Leaves: A Two-Year Study by HPLC-DAD-MS for Food By-Product Valorization
by Tommaso Ugolini, Lorenzo Cecchi, Graziano Sani, Irene Digiglio, Barbara Adinolfi, Leonardo Ciaccheri, Bruno Zanoni, Fabrizio Melani and Nadia Mulinacci
Separations 2025, 12(8), 192; https://doi.org/10.3390/separations12080192 - 24 Jul 2025
Viewed by 218
Abstract
Olive tree leaf is a phenol-rich, high-potential-value biomass that can be used to formulate food additives and supplements. Leaf phenolic content varies depending on numerous factors, like cultivar, geographical origin, year, and season of harvest. The aim of this research was to evaluate [...] Read more.
Olive tree leaf is a phenol-rich, high-potential-value biomass that can be used to formulate food additives and supplements. Leaf phenolic content varies depending on numerous factors, like cultivar, geographical origin, year, and season of harvest. The aim of this research was to evaluate the variations in phenolic profile of four major Tuscan cultivars (Frantoio, Leccio del Corno, Leccino, and Moraiolo) over four different phenological phases and across two years. All 96 olive leaf samples were harvested from trees grown in the same orchard located in Florence. After drying, their phenolic profile was characterized using HPLC-DAD-MS, and the obtained data were processed by ANOVA, GA-LDA, and RF methods. A total of 25 phenolic derivatives were analyzed, with total contents ranging 16,674.0–50,594.3 mg/kg and oleuropein (4570.0–27,547.7 mg/kg) being the predominant compound regardless of cultivar, year, and season of harvest. Oleuropein and hydroxytyrosol glucoside showed inverse proportionality and similar behavior across years in all cultivars, and therefore were highlighted as main phenolic compounds correlated with the seasonal variability in studied cultivars. Interesting behavior was also pointed out for apigenin rutinoside. Application of GA-LDA and RF methods allowed pointing out the excellent performance of leaf phenols in discriminating samples based on cultivar, harvest year, and harvesting season. Full article
(This article belongs to the Special Issue Extraction and Isolation of Nutraceuticals from Plant Foods)
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11 pages, 1292 KiB  
Article
Flotation Behaviours of Ilmenite and Associated Solution Chemistry Properties Using Saturated Fatty Acids as the Collector
by Jihua Zhai, Hao He, Pan Chen, Lin Song, Xiaohai Yao and Hongxian Zhang
Separations 2025, 12(8), 191; https://doi.org/10.3390/separations12080191 - 24 Jul 2025
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Abstract
A series of homologous saturated fatty acids were introduced and evaluated as collectors for ilmenite flotation using a combination of micro-flotation tests and surface tension measurements. The results showed that ilmenite exhibited good flotation behaviour when decanoic and dodecanoic acids were used as [...] Read more.
A series of homologous saturated fatty acids were introduced and evaluated as collectors for ilmenite flotation using a combination of micro-flotation tests and surface tension measurements. The results showed that ilmenite exhibited good flotation behaviour when decanoic and dodecanoic acids were used as collectors; however, saturated fatty acids with shorter or longer carbon chains were not suitable for ilmenite flotation (caused either by poor collection ability or limited solubility in water). The optimum flotation pH range was also dependent on the carbon chain length of saturated fatty acids, and the solution surface tension did not always match well with the ilmenite flotation behaviour when using a series of saturated fatty acids as the collector. The associated solution chemistry properties under series saturated fatty acid flotation systems were discussed, and the adsorption mechanism of decanoic acid onto the ilmenite surface was also investigated via FTIR, zeta potential, and contact angle measurements. Full article
(This article belongs to the Section Separation Engineering)
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15 pages, 2406 KiB  
Article
Adsorption Performance and Mechanism of Gallium from Sulfuric Acid Leach Liquor of High-Alumina Fly Ash
by Wenfen Wu, Chaolu Wen, Shaopeng Li, Zhenhua Sun, Xinjuan Hou, Huiquan Li and Zhibin Ma
Separations 2025, 12(8), 190; https://doi.org/10.3390/separations12080190 - 23 Jul 2025
Viewed by 249
Abstract
High-alumina fly ash may potentially be a valuable source of Ga with a concentration of Ga at 80 mg/kg. Direct adsorption and enrichment of Ga from sulfuric acid leach liquor of high-alumina fly ash is developed in this study. The H-type chelating resin [...] Read more.
High-alumina fly ash may potentially be a valuable source of Ga with a concentration of Ga at 80 mg/kg. Direct adsorption and enrichment of Ga from sulfuric acid leach liquor of high-alumina fly ash is developed in this study. The H-type chelating resin with two carboxy groups exhibited the best adsorption capacity for Ga. The maximum adsorption capacity for Ga was 55 mg/g resin with an adsorption time of 24 h, an initial Ga concentration of 500 mg/L, an adsorption temperature of 55 °C, and an initial acid concentration of 0.1 mol/L. The adsorption process of Ga was in good fit with the Langmuir isotherm and pseudo-second-order reaction kinetics model. The chemical adsorption rate was controlled by an internal diffusion mechanism. The resin had a high selectivity for Ga3+ with a Kd over 3600 compared with Fe2+, Al3+, K+, Ca2+, and Mg2+. The adsorption mechanism was found to be the ion exchange reaction between Ga and H of carboxy and hydroxyl groups. The concentration of Ga in sulfuric acid leach liquor from high-alumina fly ash achieved enrichment from 200 mg/L to 2 g/L. It is an attractive medium for large-scale Ga extraction from high-alumina fly ash. Full article
(This article belongs to the Special Issue Application of Separation Technology in Comprehensive Utilization of Solid Waste)
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25 pages, 2545 KiB  
Article
Kinetic, Isotherm, and Thermodynamic Modeling of Methylene Blue Adsorption Using Natural Rice Husk: A Sustainable Approach
by Yu-Ting Huang and Ming-Cheng Shih
Separations 2025, 12(8), 189; https://doi.org/10.3390/separations12080189 - 22 Jul 2025
Viewed by 360
Abstract
The discharge of synthetic dyes in industrial wastewaters poses a serious environmental threat as they are difficult to degrade naturally and are harmful to aquatic organisms. This study aimed to evaluate the feasibility of using clean untreated rice husk (CRH) as a sustainable [...] Read more.
The discharge of synthetic dyes in industrial wastewaters poses a serious environmental threat as they are difficult to degrade naturally and are harmful to aquatic organisms. This study aimed to evaluate the feasibility of using clean untreated rice husk (CRH) as a sustainable and low-cost adsorbent for the removal of methylene blue (MB) from synthetic wastewater. This approach effectively avoids the energy-intensive grinding process by directly using whole unprocessed rice husk, highlighting its potential as a sustainable and cost-effective alternative to activated carbon. A series of batch adsorption experiments were conducted to evaluate the effects of key operating parameters such as initial dye concentration, contact time, pH, ionic strength, and temperature on the adsorption performance. Adsorption kinetics, isotherm models, and thermodynamic analysis were applied to elucidate the adsorption mechanism and behavior. The results showed that the maximum adsorption capacity of CRH for MB was 5.72 mg/g. The adsorption capacity was stable and efficient between pH 4 and 10, and reached the highest value at pH 12. The presence of sodium ions (Na+) and calcium ions (Ca2+) inhibited the adsorption efficiency, with calcium ions having a more significant effect. Kinetic analysis confirmed that the adsorption process mainly followed a pseudo-second-order model, suggesting the involvement of a chemisorption mechanism; notably, in the presence of ions, the Elovich model provided better predictions of the data. Thermodynamic evaluation showed that the adsorption was endothermic (ΔH° > 0) and spontaneous (ΔG° < 0), accompanied by an increase in the disorder of the solid–liquid interface (ΔS° > 0). The calculated activation energy (Ea) was 17.42 kJ/mol, further supporting the involvement of chemisorption. The equilibrium adsorption data were well matched to the Langmuir model at high concentrations (monolayer adsorption), while they were accurately described by the Freundlich model at lower concentrations (surface heterogeneity). The dimensionless separation factor (RL) confirmed that the adsorption process was favorable at all initial MB concentrations. The results of this study provide insights into the application of agricultural waste in environmental remediation and highlight the potential of untreated whole rice husk as a sustainable and economically viable alternative to activated carbon, which can help promote resource recovery and pollution control. Full article
(This article belongs to the Section Environmental Separations)
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14 pages, 1840 KiB  
Article
Volatilomic Fingerprint of Tomatoes by HS-SPME/GC-MS as a Suitable Analytical Platform for Authenticity Assessment Purposes
by Gonçalo Jasmins, Tânia Azevedo, José S. Câmara and Rosa Perestrelo
Separations 2025, 12(8), 188; https://doi.org/10.3390/separations12080188 - 22 Jul 2025
Viewed by 233
Abstract
Tomatoes are globally esteemed not only for their nutritional value but also for their complex and appealing aroma, a key determinant of consumer preference. The present study aimed to comprehensively characterise the volatilomic fingerprints of three tomato species—Solanum lycopersicum L., S. lycopersicum [...] Read more.
Tomatoes are globally esteemed not only for their nutritional value but also for their complex and appealing aroma, a key determinant of consumer preference. The present study aimed to comprehensively characterise the volatilomic fingerprints of three tomato species—Solanum lycopersicum L., S. lycopersicum var. cerasiforme, and S. betaceum—encompassing six distinct varieties, through the application of headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME/GC-MS). A total of 55 volatile organic compounds (VOCs) spanning multiple chemical classes were identified, of which only 28 were ubiquitously present across all varieties examined. Carbonyl compounds constituted the predominant chemical family, with hexanal and (E)-2-hexenal emerging as putative key contributors to the characteristic green and fresh olfactory notes. Notably, esters were found to dominate the unique volatile fingerprint of cherry tomatoes, particularly methyl 2-hydroxybenzoate, while Kumato and Roma varieties exhibited elevated levels of furanic compounds. Multivariate statistical analyses, including principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), demonstrated clear varietal discrimination and identified potential aroma-associated biomarkers such as phenylethyl alcohol, 3-methyl-1-butanol, hexanal, (E)-2-octenal, (E)-2-nonenal, and heptanal. Collectively, these findings underscore the utility of volatilomic fingerprint as a robust tool for varietal identification and quality control within the food industry. Full article
(This article belongs to the Special Issue Chromatography/Mass Spectrometry for the Determination of Food Authenticity and Food Analysis)
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