Separations

24 pages, 1470 KB

Open AccessReview

Recent Trends in Solid-Phase Microextraction for the Monitoring of Drugs of Abuse in Wastewater

by Pedro Dinis, Eugenia Gallardo and Cláudia Margalho

Separations 2025, 12(9), 256; https://doi.org/10.3390/separations12090256 - 22 Sep 2025

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Wastewater analysis plays a central role in monitoring patterns of drug use within specific populations. It provides objective and real-time estimates of consumption, with minimal ethical concerns. In the current European context, drugs of abuse continue to be detected in wastewater, with varying [...] Read more.

Wastewater analysis plays a central role in monitoring patterns of drug use within specific populations. It provides objective and real-time estimates of consumption, with minimal ethical concerns. In the current European context, drugs of abuse continue to be detected in wastewater, with varying incidences across countries. Their monitoring enables the prioritisation of public health and legal interventions by healthcare professionals and drug monitoring agencies. Therefore, the development and implementation of efficient methodologies for monitoring drugs of abuse in wastewater samples is of critical importance. This systematic review aims to explore the use of miniaturised sample extraction techniques based on solid-phase microextraction for the determination of drugs of abuse in wastewater. In fact, the extraction procedure must be fast, effective, and selective in order to retain the analytes of interest. Miniaturised techniques have thus emerged as promising alternatives to conventional methods. Magnetic solid-phase extraction (MSPE) and molecularly imprinted polymers (MIPs) represent the most widely applied solid-phase microextraction techniques in recent years for the analysis of drugs of abuse in wastewater. Looking ahead, future perspectives include the development of eco-friendly workflows, automated and time-efficient techniques, increasingly selective sorbents, and robust analytical methods. Full article

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

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15 pages, 3145 KB

Open AccessArticle

Economic, Environmental, and Safety Multi-Objective Optimization Design for Separation of Tetrahydrofuran/Methanol/Water Mixture

by Mengdie Gao, Qiyu Zhang, Zhehao Jin, Yishan Liu and Yiyang Dai

Separations 2025, 12(9), 255; https://doi.org/10.3390/separations12090255 - 21 Sep 2025

Viewed by 478

Abstract

Tetrahydrofuran (THF) and methanol (MeOH) are widely used as organic solvents in chemical, pharmaceutical, and other industrial fields. The wastewater from producing 1,4-butanediol contains THF, MeOH, and water ternary azeotropic mixture. In this study, to protect the environment and improve economic feasibility, THF [...] Read more.

Tetrahydrofuran (THF) and methanol (MeOH) are widely used as organic solvents in chemical, pharmaceutical, and other industrial fields. The wastewater from producing 1,4-butanediol contains THF, MeOH, and water ternary azeotropic mixture. In this study, to protect the environment and improve economic feasibility, THF and MeOH from the wastewater must be recovered. Triple-column extractive distillation (TED), pressure-swing azeotropic distillation (PSAD) and reactive extractive dividing-wall column (REDWC) are introduced to separate this ternary system, and the NSGA-III algorithm is introduced to optimize the processes, taking the total annual cost (TAC), CO₂ emissions, and process route index (PRI) as objective functions. The results indicate that in comparison with TED process, TAC of PSAD and REDWC is reduced by 29.92% and 24.25%, respectively, and CO₂ emissions decreased by 18.01% and 25.13%, while PRI increased by 150.25% and 100.50%. This study can provide an insight for the design of ternary azeotropic system separation. Full article

(This article belongs to the Special Issue Novel Solvents and Methods in Distillation Process)

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26 pages, 3508 KB

Open AccessArticle

Optimization of Organic Micropollutant Adsorption onto Granular Activated Carbon Using Response Surface Methodology

by Nora Samghouli, Najoua Labjar, Meryem Bensemlali, Hamid Nasrellah and Souad El Hajjaji

Separations 2025, 12(9), 254; https://doi.org/10.3390/separations12090254 - 21 Sep 2025

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Abstract

Water pollution from pharmaceutical and textile industries urgently requires effective treatment solutions due to environmental and health risks. Effective treatment methods are desperately needed for water pollution from the textile and pharmaceutical industries because of the dangers to the environment and human health. [...] Read more.

Water pollution from pharmaceutical and textile industries urgently requires effective treatment solutions due to environmental and health risks. Effective treatment methods are desperately needed for water pollution from the textile and pharmaceutical industries because of the dangers to the environment and human health. To treat these micropollutants, the optimized granular activated carbon (OGAC) produced from olive fruit stones was utilized as an adsorbent in this study. The central composite design (CCD) of response surface methodology (RSM) was statistically used to optimize the operating factors for rhodamine B (RhB) and thiamphenicol (THI) removal efficiency on the optimized granular activated carbon. This study evaluated the influence of factors such as the solution’s pH, initial RhB and THI concentration, and OGAC dose, along with their interactions to model outcomes and determined optimal adsorption conditions on OGAC. The adsorption kinetic data will be analyzed using the intra-particle diffusion, pseudo-second-order, and pseudo-first-order models. Equilibrium data will be analyzed using the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherms. The adsorption thermodynamics of the various systems under investigation will also be examined. Finally, a study on OGAC regeneration has been conducted. Results showed that THI and RhB removal is primarily influenced by pH, initial pollutant concentration, and dose. RSM indicated the optimal adsorption parameters for THI and RhB on OGAC as pH = 5.7, an initial concentration of C₀ = 2.5 mg/L, and a dose of 6 g/L. The kinetic study revealed that THI and RhB retention on OGAC generally follows a pseudo-second-order kinetic model, indicating chemisorption as the primary mechanism controlling adsorption. The adsorption isotherm data analysis showed that chemisorption has a significant role in the THI and RhB adsorption process on OGAC. Furthermore, thermodynamic parameters suggest that THI adsorption on OGAC is exothermic, while RhB adsorption is endothermic. Activated carbon regeneration tests demonstrated its cost-effectiveness, and activated carbon was successfully regenerated over three cycles, achieving efficiencies of 62.39% for RhB and 59.6% for THI. These results demonstrate that the studied OGAC is an effective adsorbent for THI and RhB removal. Full article

(This article belongs to the Special Issue Adsorption Methods for Environmental Purification)

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26 pages, 13045 KB

Open AccessArticle

Carp Scales Modified with Cerium Oxide Nanoparticles as a New Bio-Adsorbent for Arsenic and Chromium Separation from Water

by Zoran Bajić, Uroš Z. Veličković, Veljko Djokić, Mihael Bučko, Jovica Bogdanov, Krstimir Pantić and Aleksandar D. Marinković

Separations 2025, 12(9), 253; https://doi.org/10.3390/separations12090253 - 19 Sep 2025

Viewed by 370

Abstract

Different treatments of fish scales from carps (Cyprinus carpio) (FS)—mechanical milling, modified with cerium dioxide (CeO₂) nanoparticles and controlled carbonization of FS and modification with CeO₂—were applied to obtain FS, FS-CeO₂ and CFS-CeO₂ bio-adsorbents. The [...] Read more.

Different treatments of fish scales from carps (Cyprinus carpio) (FS)—mechanical milling, modified with cerium dioxide (CeO₂) nanoparticles and controlled carbonization of FS and modification with CeO₂—were applied to obtain FS, FS-CeO₂ and CFS-CeO₂ bio-adsorbents. The synthesized adsorbents were used for As(V) and Cr(VI) oxyanion separation from water. Porosity and the amount of CeO₂ nanoparticles deposition were controlled using different experimental conditions. Response surface methodology (RSM) was used to select optimal parameters for adsorbent synthesis to obtain the highest adsorption capacity. The structural and surface characteristics of the synthesized adsorbents were examined using FTIR, XRD and SEM techniques. The efficiency of pollutant removal was analyzed in terms of varying experimental conditions: the mass of adsorbent, pH, temperature and contact time. RSM was also used to optimize adsorption and desorption processes. The adsorption data, obtained at 25, 35 and 45 °C, were processed using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm and Van’t Hoff thermodynamic models. The FS-CeO₂ bio-adsorbent showed good adsorption capacities of 92.61 and 65.50 mg g⁻¹ for As(V) and Cr(VI) ion removal, respectively, obtained by using the Langmuir model. Thermodynamic parameters proved that adsorption was a viable, spontaneous and endothermic process. The results from kinetic modeling indicated that both adsorbate and surface functional group concentration determine overall kinetic law with the highest participation of intra-particle diffusion resistance to pollutant transport. Exceptional adsorption and desorption performances of FS-CeO₂ in conjunction with the bio-based origin of synthesized adsorbents offer valuable alternatives for the remediation of polluted water. Full article

(This article belongs to the Section Materials in Separation Science)

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20 pages, 2946 KB

Open AccessArticle

Iron Recovery from Turkish and Romanian Bauxite Residues Through Magnetic Separation: Effect of Hydrothermal Processing and Separation Conditions

by Panagiotis Angelopoulos, Paschalis Oustadakis, Nikolaos Kountouris, Michail Samouhos, Georgios Anastassakis and Maria Taxiarchou

Separations 2025, 12(9), 252; https://doi.org/10.3390/separations12090252 - 17 Sep 2025

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Abstract

This study investigates the potential of two low-iron-grade bauxite residue (BR) samples, containing up to 27.4 wt.% Fe and originating from alumina plants in Romania and Turkey, for the recovery of iron concentrate via wet magnetic separation. The methodology involved the hydrothermal reduction [...] Read more.

This study investigates the potential of two low-iron-grade bauxite residue (BR) samples, containing up to 27.4 wt.% Fe and originating from alumina plants in Romania and Turkey, for the recovery of iron concentrate via wet magnetic separation. The methodology involved the hydrothermal reduction of the residues, aiming to transform the hematite/goethite (Fe³⁺) phases into magnetite (Fe²⁺/Fe³⁺) and enhance their magnetic susceptibility. The effect of hydrothermal treatment, magnetic induction value (up to 1600 Gs), and slurry dispersion on iron recovery and iron grade were investigated. An optimum magnetic fraction was obtained, containing 44.4 wt.% elemental iron (Fe_elem) and achieving 98% iron recovery. These results demonstrate a significant improvement compared to the magnetic fraction derived from the respective non-reduced sample, which showed a maximum of 29.7 wt.% Fe grade and 59.7% recovery. Furthermore, silicon and sodium are primarily distributed in the non-ferrous fraction. The application of sonication to enhance slurry dispersion during magnetic separation did not have a positive impact on the process. In addition to iron recovery, an aspect of considerable potential is the reutilization of the Al-rich liquor generated during hydrothermal treatment of the BR. Its reintroduction into the Bayer process circuit could contribute to improved material utilization and enhanced overall process efficiency. Full article

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

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12 pages, 1446 KB

Open AccessArticle

Investigation on Li Recovery from Greek Coal Fly Ash Under a Circular Economy Framework: An Experimental Study

by Despina Pentari, Pagona Makri, Panagiotis Xanthopoulos and Despina Vamvuka

Separations 2025, 12(9), 251; https://doi.org/10.3390/separations12090251 - 15 Sep 2025

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Abstract

Lithium is classified as a critical element and is widely used in a variety of high-tech applications. Within the framework of a circular economy, demand is rising for technologies capable of recovering high-tech metals from waste materials and industrial byproducts. Coal fly ash [...] Read more.

Lithium is classified as a critical element and is widely used in a variety of high-tech applications. Within the framework of a circular economy, demand is rising for technologies capable of recovering high-tech metals from waste materials and industrial byproducts. Coal fly ash (CFA) has attracted significant attention as a promising secondary resource for this purpose. Effective recovery requires the assessment of both metal enrichment levels and the underlying binding and leaching characteristics. The present study aims to contribute to advancing lithium recovery technology using coal fly ash as a secondary resource, thereby promoting waste valorization. Fourteen samples of coal fly ash from different power plants were collected and their mineralogy was studied by X-ray powder diffraction (XRD), their major constituents were analyzed by X-ray fluorescence spectroscopy (XRF), and their Li content was determined by inductively coupled plasma mass spectrometry (ICP-MS). Leaching experiments were conducted for selected samples using mineral acids (HCl and HF) and citric acid. Lithium concentrations in the analyzed samples ranged from 80 to 256 mg/kg, indicating enrichment relative to both global ash averages (enrichment factor > 1) and the Earth’s crust (enrichment factor > 2). Li in the samples, could be mainly associated with the amorphous fraction present in the samples. Leaching behavior across the samples follows a consistent trend, with hydrofluoric acid exhibiting the highest lithium extraction efficiency—reaching up to 79.9%. Full article

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19 pages, 4832 KB

Open AccessArticle

A Focus on the Emission of Volatile Organic Compounds (VOCs) from Raw Materials Potentially Used in Human Odor Sampling

by Elsa Boudard, Nabil Moumane, José Dugay, Jérôme Vial, Michel Sablier and Didier Thiébaut

Separations 2025, 12(9), 250; https://doi.org/10.3390/separations12090250 - 11 Sep 2025

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Abstract

The present study provided an exhaustive examination of VOC emissions originating from 13 different raw materials susceptible to being used in the sampling of the human volatilome and encompassing both polymeric and non-polymeric compositions. To achieve this aim, thermodesorption coupled with comprehensive two-dimensional [...] Read more.

The present study provided an exhaustive examination of VOC emissions originating from 13 different raw materials susceptible to being used in the sampling of the human volatilome and encompassing both polymeric and non-polymeric compositions. To achieve this aim, thermodesorption coupled with comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (TD-GC×GC/ToFMS) was employed. For each material, we report the total number of detected peaks, total volatile organic compound (TVOC) concentration, distribution of VOC emissions across different chemical families, minimum and maximum individual concentrations, as well as hypotheses regarding the origins of some specific VOCs depending on the material considered. The findings from this investigation revealed that materials, such as silicone and polyurethane, could emit an extensive array of VOCs, with up to 2000 chromatographic peaks detected, and emissions of total volatile organic compounds (TVOCs) reaching levels of 5.4 µg·g⁻¹ and 9.8 µg·g⁻¹, respectively. In the case of polyamide, some VOCs could be related to potential reagents involved in its synthesis. While highlighting materials that should be used with caution depending on the topic and target analytes, this study identified materials that exhibited minimal VOC emissions, such as polytetrafluoroethylene, aluminum, and stainless steel, after an adequate conditioning step. The selected analytical technique, TD-GC×GC/ToFMS, proved its relevance to identify and characterize semi-quantitatively VOC emissions coming from those materials. Such information was essential within the frame of the development of a body odor sampling system, our primary objective. Full article

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

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19 pages, 13378 KB

Open AccessEditor’s ChoiceArticle

Semi-Pilot Scale Extraction of Pinocembrin and Galangin from Populus alba L. × berolinensis K. Koch via Enzymatic Pretreatment and Ultrasonication

by Ru Zhao, Xiaoli Li, Yazhou Bao, Wenjun Xu, Chen Xu, Rongrong Wang, Tianlan Xia, Tingli Liu and Ailing Ben

Separations 2025, 12(9), 249; https://doi.org/10.3390/separations12090249 - 11 Sep 2025

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Abstract

In this investigation, pinocembrin and galangin were efficiently extracted from the male inflorescence of Populus alba L. × berolinensis K. Koch through an enzymatic pretreatment–ultrasonic-assisted strategy (EP-UAS), and the feasibility of their pilot-scale application was validated. The optimal parameters (ethanol volume fraction, cellulase [...] Read more.

In this investigation, pinocembrin and galangin were efficiently extracted from the male inflorescence of Populus alba L. × berolinensis K. Koch through an enzymatic pretreatment–ultrasonic-assisted strategy (EP-UAS), and the feasibility of their pilot-scale application was validated. The optimal parameters (ethanol volume fraction, cellulase dosage, incubation temperature, incubation time, pH, liquid‒solid ratio, ultrasonic irradiation power during incubation, duty cycle, ultrasonic irradiation power and time during extraction) affecting pinocembrin and galangin yields were systematically explored. The Box–Behnken design (BBD) results provided optimal parameters for the EP-UAS process. Under the optimal conditions, the actual yields of pinocembrin and galangin were 2158.33 ± 0.13 μg/g and 1257.96 ± 0.06 μg/g, respectively. Stability, recovery and reproducibility were determined under the above optimized conditions to evaluate the proposed EP-UAS method. Moreover, laboratory-scale experimental results revealed that the conditions selected via single-factor and response surface experiments were also applicable to pilot-scale production, facilitating industrialization. Full article

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

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21 pages, 5003 KB

Open AccessArticle

Synthesis and CO₂ Capture Properties of Co- and Nd-Modified ZIF-8 Materials Loaded onto Electrospun Polyacrylonitrile Fibers

by Daniela Vargas-Romero, Oscar Ovalle-Encinia, Elizabeth Rojas-García, Ana Marisela Maubert-Franco, Mónica Corea, Lucía Téllez-Jurado and José Ortiz-Landeros

Separations 2025, 12(9), 248; https://doi.org/10.3390/separations12090248 - 10 Sep 2025

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Abstract

Zeolitic imidazolate framework (ZIF)-8 materials exhibiting zinc metal centers partially replaced by cobalt or neodymium were successfully synthesized via a convenient coprecipitation method. The resulting materials were structurally and microstructurally characterized by SEM, XRD, FT-IR, and TGA, among other techniques. Subsequently, ZIF-8 nanoparticles [...] Read more.

Zeolitic imidazolate framework (ZIF)-8 materials exhibiting zinc metal centers partially replaced by cobalt or neodymium were successfully synthesized via a convenient coprecipitation method. The resulting materials were structurally and microstructurally characterized by SEM, XRD, FT-IR, and TGA, among other techniques. Subsequently, ZIF-8 nanoparticles were integrated into polyacrylonitrile fibers (PAN) via the electrospinning technique, followed by a secondary growth step to increase the ZIF-8 loading on the fiber’s surface. Furthermore, the characterization and evaluation of the materials’ CO₂ adsorption properties at low pressures revealed their volumetric CO₂ uptake capacities. The samples containing ZIF-8 powders modified with Co cations exhibited the best CO₂ capture performances of 26.48 and 8.08 cm³·g⁻¹ (at STP) for the unsupported and PAN-anchored materials, respectively. The strategy of seeding followed by secondary growth to anchor ZIF-8 onto PAN fibers is proposed as a novel and practical approach for adsorbent processing. Full article

(This article belongs to the Special Issue Recent Advances in Gas Separation and Purification)

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14 pages, 4696 KB

Open AccessEditor’s ChoiceArticle

Efficient Photocatalytic Reduction of Cr(VI) on N-Doped Sludge/Cellulose-Derived Porous Carbon Using Synergistic Experimental–Deep Learning Approach

by Na Huang, Shengwen Chen and Wanhe Du

Separations 2025, 12(9), 247; https://doi.org/10.3390/separations12090247 - 9 Sep 2025

Viewed by 497

Abstract

The photocatalytic reduction of hexavalent chromium (Cr(VI)) in wastewater represents a critical environmental challenge, given its high toxicity and mobility in wastewater. Conventional optimization methods relying on repetitive batch experiments with excessive reagent consumption. Herein, we proposed a synergistic experimental–deep learning approach to [...] Read more.

The photocatalytic reduction of hexavalent chromium (Cr(VI)) in wastewater represents a critical environmental challenge, given its high toxicity and mobility in wastewater. Conventional optimization methods relying on repetitive batch experiments with excessive reagent consumption. Herein, we proposed a synergistic experimental–deep learning approach to realize efficient photocatalytic reduction of Cr(VI). Sludge and cellulose precursors were used to prepare N-doped porous carbon through a green fabrication method at low temperature. After optimizing the composition and experimental factors, the removal efficiency of Cr(VI) could reach 92.7% after visible light irradiation in an acidic environment. The high efficiency originated from the coupled adsorption and photocatalytic mechanism. Innovatively, after comparing three algorithms, TCN and Transformer were employed to predict the desirable removal efficiency with <5% prediction error under different reaction conditions. This work highlights the novel experimental–deep learning method for heavy metal remediation using N-doped waste-derived porous carbon. Full article

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22 pages, 3041 KB

Open AccessArticle

Biosorption of Manganese Using Moringa oleifera Seed Pods: A Sustainable Approach to Water Treatment

by Laura Adriane de Moraes Pinto, Fernanda de Oliveira Tavares, Rosangela Bergamasco, Marcelo Fernandes Vieira and Angélica Marquetotti Salcedo Vieira

Separations 2025, 12(9), 246; https://doi.org/10.3390/separations12090246 - 9 Sep 2025

Viewed by 643

Abstract

Manganese (Mn) has emerged as a contaminant of concern due to its occurrence at concentrations exceeding regulatory limits in various environmental matrices, driven by both anthropogenic activities and natural geochemical processes. Although Mn is an essential micronutrient, excessive exposure poses risks to human [...] Read more.

Manganese (Mn) has emerged as a contaminant of concern due to its occurrence at concentrations exceeding regulatory limits in various environmental matrices, driven by both anthropogenic activities and natural geochemical processes. Although Mn is an essential micronutrient, excessive exposure poses risks to human health and ecosystems. This study investigates the potential application of Moringa oleifera seed pods, an agro-industrial byproduct, as low-cost biosorbents for Mn ion removal from aqueous solutions. Biosorbents were prepared from raw seed pods and chemically modified using NaOH and HCl. Surface characterization was performed using SEM, EDS, and FTIR techniques. Kinetic analysis indicated that Mn ion adsorption by all biosorbents followed a pseudo-second-order model, with equilibrium reached within 30 min. Among the tested materials, the alkali-treated biosorbent exhibited the highest removal efficiency (94%) under optimal conditions (288 K, pH 6.0, 60 min). Equilibrium data fitted both Langmuir and the Freundlich isotherms, with a maximum adsorption capacity of 7.64 mg g⁻¹ for alkali-treated pods and 6.00 mg g⁻¹ for the unmodified pods. Thermodynamic analysis revealed negative Gibbs free energy values, confirming the spontaneous nature of the biosorption process. Enthalpy values below 40 kJ mol⁻¹ (Pod_NA: 11.88 kJ mol⁻¹; Pod_AC: 1.08 kJ mol⁻¹; Pod_BA: 8.94 kJ mol⁻¹) suggest that physisorption is the predominant mechanism. These findings demonstrate the viability of Moringa oleifera pods as effective biosorbents for Mn ion remediation, supporting the valorization of agricultural waste within sustainable water treatment strategies. Full article

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

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22 pages, 7600 KB

Open AccessEditor’s ChoiceArticle

Experimental Study on Spatiotemporal Evolution Mechanisms of Roll Waves and Their Impact on Particle Separation Behavior in Spiral Concentrators

by Jian Wang, Huizhong Liu, Qihua Zou and Jun Hu

Separations 2025, 12(9), 245; https://doi.org/10.3390/separations12090245 - 8 Sep 2025

Cited by 1 | Viewed by 704

Abstract

Spiral concentrators are gravity and centrifugal force-based devices designed for mineral concentration. During processing operations, dynamic variations in the slurry’s liquid film thickness can induce hydrodynamic instability, generating roll waves on the free surface that compromise particle separation efficiency. To ensure operational stability [...] Read more.

Spiral concentrators are gravity and centrifugal force-based devices designed for mineral concentration. During processing operations, dynamic variations in the slurry’s liquid film thickness can induce hydrodynamic instability, generating roll waves on the free surface that compromise particle separation efficiency. To ensure operational stability and efficacy, this study establishes a theoretical shallow-water flow model for slurry dynamics in spiral concentrators based on hydraulic principles. Through L₂₇(3¹³) orthogonal experiments and real-time ultrasonic film thickness monitoring, the influence of key parameters on roll wave evolution is quantified. Results indicate that roll waves follow an “instability-development-dissipation” sequence. The pitch-to-diameter ratio (P/D) exerts a highly significant effect on roll wave intensity, while particle properties (density and size) exhibit moderate significance. In contrast, feed flow rate and solid concentration show negligible impacts. Roll waves amplify fluid turbulence, triggering stochastic migration of particles (especially low-density grains), which increases the standard deviation of zonal recovery rates (ZRR) and degrades separation precision. This work provides critical insights into particle behavior under roll wave conditions and offers a theoretical foundation for optimizing spiral concentrator design and process control. Full article

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22 pages, 10187 KB

Open AccessArticle

Box–Behnken-Assisted Optimization of High-Performance Liquid Chromatography Method for Enhanced Sugar Determination in Wild Sunflower Nectar

by Nada Grahovac, Milica Aleksić, Lato Pezo, Ana Đurović, Zorica Stojanović, Jelena Jocković and Sandra Cvejić

Separations 2025, 12(9), 244; https://doi.org/10.3390/separations12090244 - 7 Sep 2025

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Abstract

Sunflower (Helianthus annuus L.) is a cross-pollinated species that relies on pollinators, attracted by itsnectar composition. Nectar consists primarily of sugars (up to 70%), with sucrose, glucose, and fructose being dominant, while minor components such as mannose, arabinose, xylose, and sugar alcohols [...] Read more.

Sunflower (Helianthus annuus L.) is a cross-pollinated species that relies on pollinators, attracted by itsnectar composition. Nectar consists primarily of sugars (up to 70%), with sucrose, glucose, and fructose being dominant, while minor components such as mannose, arabinose, xylose, and sugar alcohols (e.g., mannitol and inositol) occur in lower concentrations and vary with biotic and abiotic factors. This study developed a robust high-performance liquid chromatography method with refractive index detection (HPLC-RID) for the simultaneous quantification of eight sugars (D-ribose, xylose, arabinose, fructose, mannose, glucose, sucrose, and maltose) and two sugar alcohols (mannitol, meso-inositol) in wild sunflower nectar. A Box–Behnken design (BBD), coupled with response surface methodology (RSM), was used to systematically optimize column temperature (20–23 °C), acetonitrile concentration (80–85%), and flow rate (0.7–1 mL/min), while achieving baseline separation of critical sugar pairs, including the previously co-eluting glucose/mannitol and glucose/mannose. Satisfactory resolution (Rs > 1 for all analytes) was achieved under optimized separation conditions comprising a column temperature of 20 °C, 82.5% acetonitrile, and a flow rate of 0.766 mL/min. The RSM efficiently evaluated factor interactions to maximize chromatographic performance, resulting in an optimized protocol that provides a cost-effective and environmentally friendly alternative to conventional sugar analysis methods. Method validation confirmed satisfactory linearity across relevant concentration ranges (50–500 mg/L for most sugars; 50–5500 mg/L for fructose and glucose), with correlation coefficients (R) between 0.985 and 0.999. The limits of detection (LOD) and quantification (LOQ) for the analyzed sugars and sugar alcohols ranged from 4.04 to 19.46 mg/L and from 13.46 to 194.61 mg/L, respectively. Glucose exhibited the highest sensitivity showing LOD of 4.04 and LOQ of 13.46 mg/L, whereas mannose was identified as the least sensitive analyte, with LOD of 19.46 mg/L and LOQ of 194.61 mg/L. The described method represents a reliable tool for sugar and sugar alcohol analysis in sunflower nectar and can be extended to other plant and food matrices with suitable sample preparation. Full article

(This article belongs to the Special Issue Innovative Sustainable Methods for Food Component Extraction)

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21 pages, 3693 KB

Open AccessEditor’s ChoiceArticle

Electrochemistry–Mass Spectrometry for Generation and Identification of Metabolites of Selected Drugs from Different Therapeutic Groups in Comparison with In Vitro and In Vivo Approaches

by Małgorzata Szultka-Młyńska

Separations 2025, 12(9), 243; https://doi.org/10.3390/separations12090243 - 5 Sep 2025

Viewed by 530

Abstract

The metabolism of antibiotics, antidepressants, and cardiovascular drugs has been investigated widely over the last few decades. The aim of this study was to develop an efficient analytical protocol based on the combination of electrochemistry (EC) and mass spectrometry for the identification of [...] Read more.

The metabolism of antibiotics, antidepressants, and cardiovascular drugs has been investigated widely over the last few decades. The aim of this study was to develop an efficient analytical protocol based on the combination of electrochemistry (EC) and mass spectrometry for the identification of electrochemical products (potential pharmacologically active metabolites) of selected drugs (enalapril, metronidazole, midazolam, propranolol, venlafaxine). The electrochemical mimicry of the oxidative phase I and II metabolism was achieved in a thin-layer cell equipped with different working electrodes (magic diamond (MD), glassy carbon (GC), gold (Au), platinum (Pt)). The structures of the electrochemically generated metabolites were elucidated based on accurate mass ion data and tandem mass spectrometry (MS/MS) experiments. The in silico prediction of the main sites of selected drugs’ metabolism was performed using Biotransformer 3.0, GLORYx, and Xenosite software. Moreover, incubation with liver microsomes (LMs) was performed to examine the proposed metabolic pathways of target compounds. The data from in vitro experiments agreed with the data from electrochemical oxidation, which predicted some potential metabolites found in the real samples from patients. For enzymatic incubation, N-dealkylation, O-demethylation, and hydroxylation were the metabolic pathways involved mainly in their metabolism. Their in vitro phase II metabolites were identified as glucuronic acid conjugates. Finally, different in vivo phase I and II metabolites were identified for the studied drugs, including metabolic pathways for in vivo phase I N-demethylation, N-dealkylation, O-demethylation, and hydroxylation, while the metabolic pathways for in vivo phase II metabolites were identified as glucuronic acid conjugates. Full article

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

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12 pages, 2001 KB

Open AccessArticle

Study on the Performance of BiOCl Photocatalyst for Degradation of Tetracycline Hydrochloride

by Fang Li, Yuxi Cheng, Peiyuan Li and Guanlong Yu

Separations 2025, 12(9), 242; https://doi.org/10.3390/separations12090242 - 5 Sep 2025

Viewed by 464

Abstract

Tetracycline hydrochloride (TC-HCl) is widely used in the prevention and treatment of human/animal bacterial infection due to its good antibacterial activity. However, because of its high hydrophilicity and low volatility, TC-HCl can enter the natural water body through various ways and exist in [...] Read more.

Tetracycline hydrochloride (TC-HCl) is widely used in the prevention and treatment of human/animal bacterial infection due to its good antibacterial activity. However, because of its high hydrophilicity and low volatility, TC-HCl can enter the natural water body through various ways and exist in it statically for a long time, which then causes environmental toxicity and even threatens human health. Photocatalysis, which can use free, clean and sustainable solar energy to provide power, achieves the conversion of solar energy to chemical energy and is a promising green technology for solving global environmental and energy challenges. BiOCl has suitable valence/conduction potential and good stability and hierarchical structure, which contributes to smooth transfer of surface charge. BiOCl photocatalyst materials with deionized water, anhydrous ethanol (EtOH), and ethylene glycol (EG) as solvents were prepared by using different viscosity solutions as reaction media. The characterization results showed that the type of solvent is what mainly affected the morphology and absorption intensity of the photocatalyst. BiOCl prepared with EG as solvent has the best photocatalytic degradation performance of TC-HCl, and the removal rate can reach 76% after 60 min of visible light irradiation. Its strong light response intensity and unique spherical structure contribute to the enhancement of photocatalytic activity. Full article

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20 pages, 1405 KB

Open AccessArticle

A New Affinity Gel Synthesized for Phenylalanine Ammonia Lyase Isolated from Red Clover (Trifolium pratense L.) Leaf and an Investigation into Its Kinetic Properties

by Yavuz Selim Toksöz, Çiğdem Bilen and Emine Karakuş

Separations 2025, 12(9), 241; https://doi.org/10.3390/separations12090241 - 5 Sep 2025

Viewed by 475

Abstract

Phenylalanine ammonia lyase (PAL) was first purified using affinity chromatography from the leaves of red-flowered clover, a highly antioxidant source. The characterization results of the PAL enzyme were determined, including the concentration of its activity buffer solution, pH, and temperature, which were 0.1 [...] Read more.

Phenylalanine ammonia lyase (PAL) was first purified using affinity chromatography from the leaves of red-flowered clover, a highly antioxidant source. The characterization results of the PAL enzyme were determined, including the concentration of its activity buffer solution, pH, and temperature, which were 0.1 M, 7, and 25 °C, respectively. The V_max and K_M values of the enzyme were calculated to be 0.97 EU and 0.68 mM, respectively. L-phenylalanine was used as the substrate. All kinetic studies were performed spectrophotometrically with a wavelength of 283 nm. Sepharose-4B–L-tyrosine–4-aminocinnamic acid (S-4B-TACA) was also synthesized for the first time and used as an affinity gel. The activity of the PAL extract was measured as 267.9 (millienzyme unit) mU per mL. The yield % and purification fold in the purification step of affinity chromatography were determined to be 3.8% and 19.4, respectively. The experimental results indicate that the PAL enzyme was successfully purified using affinity chromatography. The purity of the enzyme was controlled via SDS-PAGE analysis, which indicated that PAL gave a clear, single band at the line of 45 kDa, while the PAL homogenate gave two bands at around 35 and 45 kDa. Enzyme stabilization was also investigated using PAL stored at 4 °C, which retained completely protected activity for the first 3 weeks. The synthesis of the S-4B-TACA affinity gel, the purification of PAL from red clover leaves using affinity chromatography, and its characterization and statistical analysis have not been previously investigated or reported in the literature. Full article

(This article belongs to the Section Chromatographic Separations)

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13 pages, 846 KB

Open AccessArticle

Simultaneous Determination of Polycyclic Aromatic Hydrocarbons and Anthraquinone in Yerba Mate by Modified MSPD Method and GC-MS

by Dylan M. Hoffmann, José D. da Silva, Igor F. de Souza, Gabriel A. B. Prates, Vagner A. Dutra, Osmar D. Prestes and Renato Zanella

Separations 2025, 12(9), 240; https://doi.org/10.3390/separations12090240 - 4 Sep 2025

Viewed by 900

Abstract

Yerba mate (Ilex paraguariensis) is widely consumed in South America and is valued for its bioactive compounds, such as polyphenols and methylxanthines. However, during traditional processing, mainly in the fire-based scorch and drying steps, polycyclic aromatic hydrocarbons (PAHs) and anthraquinone (AQ), [...] Read more.

Yerba mate (Ilex paraguariensis) is widely consumed in South America and is valued for its bioactive compounds, such as polyphenols and methylxanthines. However, during traditional processing, mainly in the fire-based scorch and drying steps, polycyclic aromatic hydrocarbons (PAHs) and anthraquinone (AQ), substances with carcinogenic potential, may be formed. This study aimed to develop and validate an analytical method based on the balls-in-tube matrix solid-phase dispersion technique (BiT-MSPD) and analysis by gas chromatography with mass spectrometry (GC-MS) for the simultaneous determination of 16 priority PAHs and AQ in yerba mate. Parameters such as sorbent type, solvent, sample-to-sorbent ratio, and extraction time were optimized. The method showed good linearity (r² > 0.99), detection limits between 1.8 and 3.6 µg·kg⁻¹, recoveries ranging from 70 to 120%, and acceptable precision (RSD ≤ 20%). The method was applied to 31 yerba mate samples, including 20 commercial samples and 11 collected at different stages of processing. Most commercial samples showed detectable levels of PAHs, with some exceeding the limits established by the European Union. AQ was detected in 40% of the samples, with some values above the permitted limit of 20 µg·kg⁻¹. The results confirm that scorch (sapeco) and drying contribute to contaminant formation, highlighting the need to modernize industrial processing practices. The proposed method proved to be effective, rapid, and sustainable, representing a promising tool for the quality control and food safety monitoring of yerba mate. Full article

(This article belongs to the Topic Advances in Analysis of Food and Beverages, 2nd Edition)

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18 pages, 1972 KB

Open AccessArticle

Characterization of Pyrolysis Oils Using a Combination of GC×GC/TOFMS and GC/HRMS Analysis: The Impact of Data Processing Parameters

by Xiangdong Chen, Carlos Rincon, Benoît Gadenne, José Dugay, Michel Sablier and Jérôme Vial

Separations 2025, 12(9), 239; https://doi.org/10.3390/separations12090239 - 4 Sep 2025

Viewed by 651

Abstract

Human population growth and increasing transportation demands have led to rising global tire consumption and associated waste. In response, various material and energy recovery strategies, such as pyrolysis, have been developed to produce high-value-added products such as pyrolysis oils, which can be reused [...] Read more.

Human population growth and increasing transportation demands have led to rising global tire consumption and associated waste. In response, various material and energy recovery strategies, such as pyrolysis, have been developed to produce high-value-added products such as pyrolysis oils, which can be reused as materials or fuels. However, these oils often contain heteroatom-containing compounds (e.g., nitrogen, oxygen, sulfur) that can hinder their valorization and must therefore be identified and removed. To characterize heteroatomic compounds present in distillation fractions of pyrolysis oils, GC×GC/TOFMS and GC/HRMS were employed. For non-target analysis, data processing parameters were optimized using a Central Composite Design (CCD). The most influential parameters for GC×GC/TOFMS were the minimum number of mass-to-charge ratio (m/z) signals kept in the deconvoluted spectra (minimum stick count) and peak signal-to-noise ratio (S/N), while for GC/HRMS, optimization focused on the m/z S/N threshold, peak S/N, and total ion current (TIC). Under optimal conditions, 129 and 92 heteroatomic compounds were identified via GC×GC/TOFMS and GC/HRMS, respectively, within a single distillation fraction, with 57 compounds identified using both techniques. Notably, GC×GC/TOFMS exclusively identified 72 compounds, while there were only 5 unique to GC/HRMS. These results highlight the effectiveness of GC×GC/TOFMS in characterizing heteroatomic compounds in complex mixtures, while also underlining the complementary value of GC/HRMS. 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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23 pages, 1137 KB

Open AccessReview

Challenges Associated with Membrane Separation of Polypeptides and Relevant Solution Strategies

by Yu Yang, Lei Duan and Hao Wu

Separations 2025, 12(9), 238; https://doi.org/10.3390/separations12090238 - 4 Sep 2025

Viewed by 863

Abstract

Polypeptides exhibit significant health-promoting effects through diverse biological activities, including antihypertensive, antidiabetic, anti-cancer, antimicrobial, and antioxidant properties. Membrane technology offers an efficient separation approach for polypeptides due to its high efficiency, low energy consumption, operational simplicity, and environmental sustainability. This review briefly described [...] Read more.

Polypeptides exhibit significant health-promoting effects through diverse biological activities, including antihypertensive, antidiabetic, anti-cancer, antimicrobial, and antioxidant properties. Membrane technology offers an efficient separation approach for polypeptides due to its high efficiency, low energy consumption, operational simplicity, and environmental sustainability. This review briefly described the advancements in membrane separation of polypeptides and highlighted the major implementation challenges, such as membrane fouling, peptide adsorption losses, and compromised separation efficiency caused by peptide aggregation. Contributing factors for each issue based on the progress and reports of relevant research were analyzed. And solutions and strategies were also summarized as feed pretreatment, operational parameter optimization, aggregate elimination, and membrane surface modification. These approaches could reduce product loss and enhance peptide yield during purification. This review can provide reference for the research on efficient membrane separation of polypeptide products. Full article

(This article belongs to the Section Separation Engineering)

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24 pages, 1936 KB

Open AccessReview

Artificial Intelligence in Chemical Dosing for Wastewater Purification and Treatment: Current Trends and Future Perspectives

by Jie Jin, Ming Liu, Boyu Chen, Xuanbei Wu, Ling Yao, Yan Wang, Xia Xiong, Luoyu Wei, Jiang Li, Qifeng Tan, Dingrui Fan, Yibo Du, Yunhui Lei and Nuan Yang

Separations 2025, 12(9), 237; https://doi.org/10.3390/separations12090237 - 3 Sep 2025

Viewed by 1239

Abstract

Recent concerns regarding artificial intelligent (AI) technologies have spurred studies into improving wastewater treatment efficiency and identifying low-carbon processes. Treating one cubic meter of wastewater necessarily consumes a certain amount of chemicals and energy. Approximately 20% of the total chemical consumption is attributed [...] Read more.

Recent concerns regarding artificial intelligent (AI) technologies have spurred studies into improving wastewater treatment efficiency and identifying low-carbon processes. Treating one cubic meter of wastewater necessarily consumes a certain amount of chemicals and energy. Approximately 20% of the total chemical consumption is attributed to phosphorus and nitrogen removal, with the exact proportion varying based on treatment quality and facility size. To promote sustainability in wastewater treatment plants (WWTPs), there has been a shift from traditional control systems to AI-based strategies. Research in this area has demonstrated notable improvements in wastewater treatment efficiency. This review provides an extensive overview of the literature published over the past decades, aiming to advance the ongoing discourse on enhancing both the efficiency and sustainability of chemical dosing systems in WWTPs. It focuses on AI-based approaches utilizing algorithms such as neural networks and fuzzy logic. The review encompasses AI-based wastewater treatment processes: parameter analysis/forecasting, model development, and process optimization. Moreover, it summarizes six promising areas of AI-based chemical dosing, including acid–base regents, coagulants/flocculants, disinfectants/disinfection by-products (DBPs) management, external carbon sources, phosphorus removal regents, and adsorbents. Finally, the study concludes that significant challenges remain in deploying AI models beyond simulated environments to real-world applications. Full article

(This article belongs to the Special Issue Sustainable and Intelligent Process Control of Pollutant Separation and Purification)

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17 pages, 592 KB

Open AccessReview

Exploring the Influence of Extraction Methods, Solvents, and Temperature on Total Phenolic Recovery and Antioxidant Capacity in Olive Leaf Extracts: A Systematic Review with Quantitative Synthesis

by María Castillo-Correa, Cristina Montalbán-Hernández, María D. Navarro-Hortal, Diego Peña-Guzmán, Alberto Badillo-Carrasco, Alfonso Varela-López, Daniel Hinojosa-Nogueira and Jose M. Romero Márquez

Separations 2025, 12(9), 236; https://doi.org/10.3390/separations12090236 - 3 Sep 2025

Viewed by 949

Abstract

Background: Olive leaves are a rich source of bioactive phenolic compounds, but extraction yields vary depending on methodological choices. The aim was to identify optimal parameters for maximizing recovery and preserving antioxidant activity. Methods: Fourteen studies (149 samples) were included, following predefined eligibility [...] Read more.

Background: Olive leaves are a rich source of bioactive phenolic compounds, but extraction yields vary depending on methodological choices. The aim was to identify optimal parameters for maximizing recovery and preserving antioxidant activity. Methods: Fourteen studies (149 samples) were included, following predefined eligibility criteria and PRISMA guidelines for systematic review. Data on TPC, TFC, and antioxidant assays (DPPH, FRAP, ABTS) were extracted and analyzed according to extraction method, solvent type, and processing conditions. Results: Soxhlet extraction and shaking achieved the highest TPC and antioxidant capacity, whereas ultrasound-assisted and high-voltage electrical discharge extractions showed lower averages unless intensity or duration was increased. Solvent polarity was critical: ≥75% aqueous methanol provided the highest TPC and FRAP, while ≥75% ethanol yielded the greatest TFC and ABTS activity. Pure water consistently gave the lowest yields. Extractions at >50 °C increased TPC up to fivefold compared to room temperature but did not proportionally improve radical-scavenging capacity. Most phenolic compounds were recovered within ≤1 h under optimized, heated, or assisted conditions, with longer times offering no significant advantage. Conclusions: Optimizing solvent composition, temperature, and extraction time is essential for maximizing yield and maintaining antioxidant quality in olive leaf extracts, and standardized protocols are needed to enable direct comparisons across studies. Full article

(This article belongs to the Special Issue Extraction and Characterization of Bioactive Compounds from Plant and Natural Sources)

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15 pages, 2024 KB

Open AccessArticle

Ionic Speciation and Coordination Mechanisms of Vanadium, Iron, and Aluminum in the Oxalic Acid Leachate of Shale

by Qing Xiong, Zishuai Liu, Qianwen Li, Huiyang Lin, Xuekun Tang and Xianping Luo

Separations 2025, 12(9), 235; https://doi.org/10.3390/separations12090235 - 1 Sep 2025

Viewed by 651

Abstract

The oxalic acid leachate of vanadium-bearing shale (OALS) is a complex system in which the ion states and coordination mechanisms of the primary metallic elements—vanadium, iron, and aluminum—are not fully understood. This study investigated the ionic speciation and coordination mechanisms of vanadium, iron, [...] Read more.

The oxalic acid leachate of vanadium-bearing shale (OALS) is a complex system in which the ion states and coordination mechanisms of the primary metallic elements—vanadium, iron, and aluminum—are not fully understood. This study investigated the ionic speciation and coordination mechanisms of vanadium, iron, and aluminum in OALS. The results indicate that vanadium predominantly existed as VO(C₂O₄)₂²⁻ anions, iron as Fe(C₂O₄)₂⁻ and Fe(C₂O₄)₃³⁻ anions, and aluminum as Al(C₂O₄)₂⁻ and Al(C₂O₄)₃³⁻ anions. The coordination reaction processes and equations of various oxalate complexes were examined. Regardless of whether the molar ratio was 1:1 or 1:2, the iron–oxalate complex exhibited the lowest reaction Gibbs free energy (ΔG), with values of −5343.69 and −1470.72 kJ/mol, respectively. The aluminum–oxalate complex followed, with ΔG values of −5169.23 and −1318.87 kJ/mol, respectively. The vanadium–oxalate complex displayed the highest reaction ΔG, at −2760.65 and −714.12 kJ/mol, respectively. Therefore, the coordination mechanism of vanadium, iron, and aluminum with oxalate ions in OALS is such that iron coordinated with oxalate first, followed by aluminum, and finally vanadium. The research results have important guiding significance for the purification, enrichment, and coordination mechanisms of complex solutions. Full article

(This article belongs to the Special Issue Efficient Extraction, Separation and Purification of Critical Metal Resources)

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16 pages, 2198 KB

Open AccessArticle

Fly Ash-Derived Mesoporous Silica–Alumina Aerogel via an Optimized Water-Acid Leaching Process for Effective Methylene Blue Removal

by Ke Sun, Yike Liu, Zhiming Zhang, Jiayu Xu, Jiajing Yu, Jiankuan Zhang, Lianzheng Gui, Zhuo Chen and Sha Liang

Separations 2025, 12(9), 234; https://doi.org/10.3390/separations12090234 - 1 Sep 2025

Viewed by 596

Abstract

Adsorption is a common method for solving the contamination of methylene blue (MB) in dyeing wastewater. Aerogel adsorbents with high porosity and specific surface areas have attracted increasing attention. However, the high costs of raw materials for aerogel preparation restrict their large-scale production [...] Read more.

Adsorption is a common method for solving the contamination of methylene blue (MB) in dyeing wastewater. Aerogel adsorbents with high porosity and specific surface areas have attracted increasing attention. However, the high costs of raw materials for aerogel preparation restrict their large-scale production and application. Fly ash (FA), a by-product of coal-fired power plants, is rich in silica and aluminum elements and has the potential to prepare aerogel adsorbents. This study proposed a modified recycling route for FA to synthesize silica–alumina composite aerogel with high specific surface area. FA was pretreated by three steps of alkali fusion, water leaching and acid leaching to obtain a solution rich in silicon and aluminum elements, with a total leaching efficiency of 96.92% and 91.36% for silicon and aluminum, respectively, under optimized alkaline fusion conditions of FA:NaOH mass ratio of 1:1.2, calcination time of 2 h, and calcination temperature of 550 °C. Silica–alumina aerogel with a specific surface area of 661.3 m²/g was then synthesized from the leaching solution through a sol–gel method, exhibiting well-developed mesopores and achieving an adsorption capacity of 52.22 mg/g for MB. The adsorption kinetics and isotherms of MB adsorption by FA-derived silica–alumina composite aerogel was investigated. FTIR characterization confirmed that the adsorption of MB by FA-derived aerogel was mainly physical adsorption. This study provides a new approach for the resource utilization of FA, and the high-specific-surface-area FA-derived aerogel holds potential as an alternative adsorbent for the removal of dyes in wastewater. Full article

(This article belongs to the Special Issue Engineering the Loop: Advancing Wastewater Treatment and Sludge Valorization Through Innovative Separation Materials)

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29 pages, 2543 KB

Open AccessArticle

Synergistic Extraction of Samarium(III) from Water via Emulsion Liquid Membrane Using a Low-Concentration D2EHPA–TOPO System: Operational Parameters and Salt Effects

by Ahlem Taamallah and Oualid Hamdaoui

Separations 2025, 12(9), 233; https://doi.org/10.3390/separations12090233 - 1 Sep 2025

Cited by 1 | Viewed by 550

Abstract

The synergistic effect of using D2EHPA and TOPO together to enhance the extraction of samarium(III) from aqueous media via emulsion liquid membrane (ELM) technology was explored. D2EHPA in binary mixtures with TBP and in ternary mixtures with TOPO and TBP was also tested. [...] Read more.

The synergistic effect of using D2EHPA and TOPO together to enhance the extraction of samarium(III) from aqueous media via emulsion liquid membrane (ELM) technology was explored. D2EHPA in binary mixtures with TBP and in ternary mixtures with TOPO and TBP was also tested. Among the tested extractants, a binary mixture of 0.1% (w/w) D2EHPA and 0.025% (w/w) TOPO achieved 100% samarium(III) extraction at a low loading. This mixture outperformed D2EHPA-TBP and other systems because D2EHPA strongly binds to Sm(III) ions, while TOPO increases the solubility and transport efficiency of metal complexes. Additionally, process factors that optimize performance and minimize emulsion breakage were examined. Key insights for successfully implementing the process include the following: 5 min emulsification with 0.75% Span 80 in kerosene at pH 6.7 (natural), 250 rpm stirring, a 1:1 internal/membrane phase volume ratio, a 20:200 treatment ratio, and a 0.2 N HNO₃ stripping agent. These insights produced stable, fine droplets, enabling complete recovery and rapid carrier regeneration without emulsion breakdown. Extraction kinetics accelerate with temperature up to 35 °C but declined above this limit due to emulsion rupture. The activation energy was calculated to be 33.13 kJ/mol using pseudo-first-order rate constants. This suggests that the process is diffusion-controlled rather than chemically controlled. Performance decreases with Sm(III) feed concentrations greater than 200 mg/L and in high-salt matrices (Na₂SO₄ > NaCl > KNO₃). Integrating these parameters yields a scalable, low-loading ELM framework capable of achieving complete Sm(III) separation with minimal breakage. Full article

(This article belongs to the Section Separation Engineering)

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15 pages, 4128 KB

Open AccessArticle

Centrifugal Filtration Devices to Separate Peptides/Proteins as a Characterization Tool: Good Specificity but Poor Quantification

by Marion Sicot, Claire Gazaille, Zeynep Güneş Tepe, Léna Guyon, Nolwenn Lautram, Patrick Saulnier, Joël Eyer, Elise Lepeltier and Guillaume Bastiat

Separations 2025, 12(9), 232; https://doi.org/10.3390/separations12090232 - 30 Aug 2025

Viewed by 631

Abstract

Centrifugal filtration devices are increasingly being used to separate (bio)molecules thanks to their molar masses. This is partly due to their ease of use, with sample preparation requiring no complicated protocol and often being able to be run as is. Nevertheless, several limitations [...] Read more.

Centrifugal filtration devices are increasingly being used to separate (bio)molecules thanks to their molar masses. This is partly due to their ease of use, with sample preparation requiring no complicated protocol and often being able to be run as is. Nevertheless, several limitations have been highlighted in the literature, such as proteins’ selectivity according to their molar masses, clogging problems and some post-separation quantification issues. We wanted to test the real potential of the centrifugal filtration devices as a characterization tool, by verifying their specificity using a library of peptides and proteins. The impact of the peptide charge on separation performance as well as the impact of biological material concentration and centrifugation rate were evaluated using three membranes with different cut-offs. A good specificity was confirmed: biological materials that have molar masses which are below the membrane cut-off can pass almost completely through the membrane, while those with molar masses above the membrane cut-off are almost fully retained. The findings proved more problematic when protein mixtures were analyzed: despite still having good specificity, biological materials with molar masses below the membrane cut-off only partially crossed the membranes, due to clogging effects, making quantification of the initial mixture incorrect. It is therefore essential to be very careful when working with centrifugal filtration devices, as their use requires precise and relevant controls, without necessarily being able to optimize the separation of mixtures. Thus, this remains far from an easy and ready-to-use system. Full article

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17 pages, 1788 KB

Open AccessArticle

Novel Microwave-Assisted Cloud Point Extraction Prior to Gas Chromatography–Mass Spectrometry for the Extraction of Organochlorine and Organophosphorus Pesticides from Fruit Juices

by Asya Hristozova and Kiril Simitchiev

Separations 2025, 12(9), 231; https://doi.org/10.3390/separations12090231 - 29 Aug 2025

Viewed by 464

Abstract

The current research aims to develop a simple, sensitive, and green analytical method for the group extraction/monitoring of 19 organochlorine and organophosphorus pesticides from fruit juices using microwave radiation to assist a cloud point extraction (MW-CPE) in combination with re-extraction in hexane and [...] Read more.

The current research aims to develop a simple, sensitive, and green analytical method for the group extraction/monitoring of 19 organochlorine and organophosphorus pesticides from fruit juices using microwave radiation to assist a cloud point extraction (MW-CPE) in combination with re-extraction in hexane and GC-MS/MS detection. The main experimental factors affecting the CPE and re-extraction have been optimized. The matrix-matched calibration was performed, and the limit of quantification (LOQ) for all studied pesticides at optimized conditions ranged between 5 and 47 ng L⁻¹. When applying only 0.25 mL of hexane for re-extraction, the proposed method shows good accuracy and precision. The “greenness” of the developed MW-CPE-GC-MS/MS method was assessed using the AGREE prep software. The method has been successfully implemented in pesticide analysis in commercially available fruit juices (lemon concentrate and red apple juice). The recovery values obtained for most analytes were within the range of 71% and 114% and RSD below 20% (exept Heptahlor, Aldrin, o,p-DDD, p,p-DDD and o,p-DDT, p,p-DDT). The developed method combines a preconcentration with a sample clean-up step due to the extraction of the pigments into the non-polar micelles during the extraction step, and deposition in the intermediate layer of MgSO₄ during the re-extraction step. Full article

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

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22 pages, 9645 KB

Open AccessReview

Research Progress on the Application of Ionic Rare Earth Tailings in Silicate Materials

by Xue Wang, Wen Ni, Jiajie Li and Siqi Zhang

Separations 2025, 12(9), 230; https://doi.org/10.3390/separations12090230 - 29 Aug 2025

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Abstract

With the continuous expansion of rare earth resource development, the large-scale accumulation of ionic rare earth tailings (IRETs) has exerted pressure on both environmental and resource management. Due to their inherent low reactivity, unstable composition, and potential environmental risks, their widespread engineering application [...] Read more.

With the continuous expansion of rare earth resource development, the large-scale accumulation of ionic rare earth tailings (IRETs) has exerted pressure on both environmental and resource management. Due to their inherent low reactivity, unstable composition, and potential environmental risks, their widespread engineering application faces many challenges. To achieve the resource utilization of this solid waste, scholars in recent years have conducted extensive research on their application in silicate materials. This study systematically reviews the existing research. Given that the trace rare earth oxides in IRETs exhibit excellent mineralization effects and that IRETs contain a significant amount of clay minerals, IRETs can be feasibly applied in the production of silicate materials, including clinker, tiles, ceramics, glass-ceramics, and geopolymers. The research findings aim to provide technical support and practical guidance for the large-scale resource utilization of IRETs, promoting their application in silicate material production. This study identifies the common issues found in the research and provides recommendations for the high-value and large-scale resource utilization of IRETs in the future. Full article

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

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14 pages, 2613 KB

Open AccessArticle

Synergistic Enhancement of Sludge Deep Dewatering via Tea Waste and Sludge-Derived Biochars Coupled with Polyaluminum Chloride

by Qiang-Ying Zhang, Geng Xu, Hui-Yun Qi, Xuan-Xin Chen, Hou-Feng Wang and Xiao-Mei Cui

Separations 2025, 12(9), 229; https://doi.org/10.3390/separations12090229 - 27 Aug 2025

Viewed by 572

Abstract

Although coagulation can enhance sludge dewatering performance, it often leads to dense flocs, hindered water release, and secondary pollution of the sludge cake. In this study, three types of biochar-based skeleton materials, tea waste-derived biochar (TB), PAC sludge-derived biochar (PB), and their mixture [...] Read more.

Although coagulation can enhance sludge dewatering performance, it often leads to dense flocs, hindered water release, and secondary pollution of the sludge cake. In this study, three types of biochar-based skeleton materials, tea waste-derived biochar (TB), PAC sludge-derived biochar (PB), and their mixture (MB), were employed in combination with polyaluminum chloride (PAC) to improve sludge permeability and water release capacity. The results showed that PAC alone reduced the water content (Wc) and capillary suction time (CST) of raw sludge (RS) from 79.07% and 97.45 s to 69.45% and 42.30 s, respectively. In contrast, biochar–PAC composite conditioning achieved further enhancement. Among them, the TBP group (10% DS TB + 4% DS PAC) exhibited the best performance, with Wc and CST reduced to 58.73% and 55.65 s, reaching the threshold for deep dewatering (Wc < 60%). Low-field nuclear magnetic resonance (LF-NMR) analysis revealed an enhanced transformation from bound to free water, improving water mobility. Zeta potential and particle size analysis indicated that biochar promoted electrostatic neutralization and adsorption bridging. Rheological and EPS measurements demonstrated significant reductions in yield stress and apparent viscosity, alongside the enhanced release of proteins and polysaccharides into soluble EPS (S-EPS). Scanning electron microscopy and pore structure analysis further confirmed that biochar formed a stable porous skeleton (pore diameter up to 1.365 μm), improving sludge cake permeability. In summary, biochar synergizes with PAC through a “skeleton support–charge neutralization–adsorption bridging” mechanism, reconstructing sludge microstructure and significantly improving deep dewatering performance. Full article

(This article belongs to the Special Issue Current Status and Prospects of Environmentally Friendly Sludge Dewatering, Solidification and Stabilization Technology)

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24 pages, 2106 KB

Open AccessArticle

Synergistic Recovery of Dysprosium(III) from Water via an Emulsion Liquid Membrane at Low Concentrations of Cyanex 272–D2EHPA: Impact of Process Factors and Water Sources

by Ahlem Taamallah and Oualid Hamdaoui

Separations 2025, 12(9), 228; https://doi.org/10.3390/separations12090228 - 25 Aug 2025

Cited by 1 | Viewed by 489

Abstract

This study reports an investigation of the synergistic extraction of dysprosium (Dy(III)) from aqueous media using a low-concentration, binary carrier mixture of Cyanex 272 and D2EHPA within an emulsion liquid membrane (ELM). Within the tested formulations, the one containing 0.42% (w/ [...] Read more.

This study reports an investigation of the synergistic extraction of dysprosium (Dy(III)) from aqueous media using a low-concentration, binary carrier mixture of Cyanex 272 and D2EHPA within an emulsion liquid membrane (ELM). Within the tested formulations, the one containing 0.42% (w/w) Cyanex 272 and 0.28% (w/w) D2EHPA yielded the best results. The impact of process factors that maximize recovery efficiency and minimize emulsion breakdown was also examined. A Span 80 loading of 0.75% (w/w) achieved 97.5% extraction with minimal breakage (less than 2.1%). An external phase pH of 5.8 achieves an optimal balance of high-throughput Dy(III) recovery and membrane stability; 0.2 N HNO₃ as the stripping phase strikes the optimal balance, providing strong initial uptake with minimal emulsion degradation. As the initial Dy(III) loading increases, extraction efficiency decreases. Increasing the temperature from 15 to 45 °C accelerates mass transfer, achieving near-complete extraction in under 15 min. However, above 45 °C, emulsion breakage spikes, causing a collapse in efficiency. Similarly, increasing NaCl levels suppresses Dy(III) uptake and promotes coalescence. This reduces recovery from seawater to just over 70%. Nevertheless, the balanced mineral content of Zamzam water preserves emulsion integrity and enables 100% extraction. The activation energy was found to be 26.16 kJ/mol, suggesting that mass transfer, rather than the chemical reaction at the interface, controls the process. The results of this study highlight the synergistic efficiency advantage of the ELM system at lower carrier concentrations, even in complex water sources. Full article

(This article belongs to the Section Separation Engineering)

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11 pages, 1817 KB

Open AccessArticle

Highly Efficient Extraction of Phenolic Compounds from Coal Tar Using Alcohol Amine Aqueous Solutions via Synergistic Extraction

by Yonglin Li, Bing Peng, Yeping Yang, Qiuhong Ai, Jiayi Zhou, Yong Wang, Huajie Liu and Weiwei Yan

Separations 2025, 12(9), 227; https://doi.org/10.3390/separations12090227 - 25 Aug 2025

Viewed by 512

Abstract

This study utilizes aqueous solutions of organic amines as extractants to remove phenolic compounds from coal tar. It elucidates the extraction mechanism between phenolic compounds and organic amines, and conducts a comprehensive investigation into the extraction performance of various monomeric organic amine aqueous [...] Read more.

This study utilizes aqueous solutions of organic amines as extractants to remove phenolic compounds from coal tar. It elucidates the extraction mechanism between phenolic compounds and organic amines, and conducts a comprehensive investigation into the extraction performance of various monomeric organic amine aqueous solutions and their composite solutions for phenolic compounds in model oils or light coal tar. The experimental results showed that monoethanolamine (MEA), characterized by a higher reaction equilibrium constant, exhibits superior extraction performance for phenolic compounds in light coal tar compared to diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), and diethylaminoethanol (DEAE) when used at the same mass concentration of extractant. The addition of a specific concentration of DEA or TEA to a 20 wt%–25 wt% MEA solution significantly reduces the entrainment of neutral oil impurities during the extraction process and enhances the precipitation of phenolic compounds during the acidification phase. Under the optimal process parameters, the composite aqueous solution, comprising 25 wt% MEA, 5 wt% DEA, and 5 wt% TEA, demonstrated a 35.1 wt% increase in the acidification yield of phenolic compounds, Y_a,P, a 20.8 wt% increase in the total yield of phenolic compounds, Y_P, and a 46.0% significant decrease in neutral oil entrainment compared to the solution with a 30% MEA aqueous solution. Full article

(This article belongs to the Section Purification Technology)

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