Separations

21 pages, 13811 KiB

Open AccessArticle

Experimental Study on Brine Storage for Overwintering by Using Salinity-Gradient Solar Pond in Zabuye Salt Lake, Tibet

by Qian Wu, Yunsheng Wang, Jintao Zhang, Ke Zhang, Juntao Li, Zhikui He, Lingzhong Bu, Jiangjiang Yu and Zhen Nie

Separations 2025, 12(2), 54; https://doi.org/10.3390/separations12020054 - 19 Feb 2025

Viewed by 261

Abstract

Known as the “white oil”, lithium is a key raw material to support strategic emerging industries and future industrial development. Zabuye Salt Lake is the only one in Tibet, China that has so far realized the industrialization of lithium extraction from the salt [...] Read more.

Known as the “white oil”, lithium is a key raw material to support strategic emerging industries and future industrial development. Zabuye Salt Lake is the only one in Tibet, China that has so far realized the industrialization of lithium extraction from the salt lake brine. The green and low-cost lithium extraction technology by using the salinity-gradient solar pond (SGSP) adopted has always been paid much attention by lithium-related practitioners and researchers. In order to improve the lithium yield and grade of a single crystallization pond, the cross-year brine mixing method can be used to increase the initial temperature and CO₃²⁻ concentration of the raw brine for making the SGSP. The premise is to ensure that the summer brine with low Li⁺ and high CO₃²⁻ prepared in the previous year could be stored safely for overwintering with a minimal change in brine composition, for use in brine mixing in February and March of the next year, which can be realized by using the SGSP. In this paper, two experiments of brine storage for overwintering were carried out in the Zabuye mining area, Tibet in 2020 and 2021 by using the large-scale SGSP with an area of nearly 4000 m². The results show that during the operation of the SGSP in winter, the brine temperature in the lower convective zone (LCZ) can still rise to more than 20 °C and remain relatively stable, indicating that the coverage of surface ice layer not only has an effect of heat preservation and insulation on the SGSP, but also plays a positive role in the thermal storage capacity of the SGSP. The vertical distributions of brine temperature, density and salinity in the pond showed the ideal gradient curves increasing from top to bottom, and the concentrations of Li⁺ and CO₃²⁻ in the brine only decreased slightly. The structure of the salinity-gradient layer tended to stabilize faster when the brine filling depth was larger, but the boundary between the upper convective zone (UCZ) and the non-convective zone (NCZ) was relatively blurred. It is completely feasible to store the brine for overwintering by using the SGSP in the Zabuye mining area, and the experimental results could be directly scalable to larger industrial applications. It can not only provide high-quality raw brine for cross-year brine mixing, but also reduce the pressure of brine production, and a small amount of lithium mixed salt collected is helpful to increase the output of a single crystallization pond. Additionally, the potential challenges of maintaining the SGSP system during extreme winter conditions are described, and effective measures and suggestions are proposed to make the technology feasible in diverse climates. Full article

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

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13 pages, 3040 KiB

Open AccessArticle

Development and Application of a UPLC–MRM–MS Method for Quantifying Trimethylamine, Trimethylamine-N-Oxide, and Related Metabolites in Individuals with and Without Metabolic Syndrome

by Mohammed E. Hefni and Cornelia M. Witthöft

Separations 2025, 12(2), 53; https://doi.org/10.3390/separations12020053 - 18 Feb 2025

Viewed by 225

Abstract

Trimethylamine-N-oxide (TMAO) is associated with various chronic diseases. TMAO is a downstream oxidative metabolite of trimethylamine (TMA) that is generated by the gut microbiota from dietary choline, carnitine, and betaine. Current analytical methods predominantly target TMAO only, due to the challenge of efficiently [...] Read more.

Trimethylamine-N-oxide (TMAO) is associated with various chronic diseases. TMAO is a downstream oxidative metabolite of trimethylamine (TMA) that is generated by the gut microbiota from dietary choline, carnitine, and betaine. Current analytical methods predominantly target TMAO only, due to the challenge of efficiently extracting and quantifying TMA. The present study demonstrates a simple and rapid UPLC–MRM–MS method for concurrent quantification of TMAO, TMA, and related precursors (choline, betaine, and various carnitines) following a methanol extraction from plasma and derivatization using iodoacetonitrile (IACN). Pure methanol resulted in a higher extractability of TMA (up to two-fold) compared to both pure acetonitrile and various methanol/acetonitrile mixtures. The quantification method showed high linearity within the tested range of 0.0625–100 μmol/L (determination coefficient > 0.999) and an intra- (n = 3) and inter-day (n = 9) precision of 2–8% along with an average recovery of above 94% for all metabolites (TMAO, TMA, choline, betaine, L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine). The method’s applicability was confirmed through a comparison of TMAO and its precursor concentrations in plasma samples of overnight-fasted subjects with (n = 12) and without (n = 21) metabolic syndrome. Full article

(This article belongs to the Topic Chromatography–Mass Spectrometry Analysis in Biomedical Research and Clinical Laboratory)

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43 pages, 8193 KiB

Open AccessReview

From Waste to Wealth: A Circular Economy Approach to the Sustainable Recovery of Rare Earth Elements and Battery Metals from Mine Tailings

by Mohammed Omar Sahed Chowdhury and Deniz Talan

Separations 2025, 12(2), 52; https://doi.org/10.3390/separations12020052 - 14 Feb 2025

Viewed by 454

Abstract

The increasing global demand for critical minerals, driven by rapid population growth and the widespread adoption of low-carbon technologies, electric vehicles, and clean energy systems, highlights the urgent need for sustainable resource management. Mine tailings, traditionally considered waste, are now being recognized as [...] Read more.

The increasing global demand for critical minerals, driven by rapid population growth and the widespread adoption of low-carbon technologies, electric vehicles, and clean energy systems, highlights the urgent need for sustainable resource management. Mine tailings, traditionally considered waste, are now being recognized as valuable secondary sources for mineral recovery. This paper compiles a comprehensive review of the four short- and mid-term critical minerals (lithium, cobalt, nickel, and rare earth elements) and provides insights regarding their recovery with a focus on the latest technological advancements. By exploring key innovations in separation processes, the review demonstrates how these technologies are addressing supply chain bottlenecks while simultaneously reducing the environmental footprint of mining operations. The paper also advocates for a holistic approach to mine waste management, integrating mineral recovery with environmental remediation. It emphasizes the dual benefits of recovering valuable resources while purifying contaminated water and mitigating pollution risks. The proposed circular economy model suggests a sustainable blueprint for managing mine tailings, emphasizing resource reuse, waste reduction, and economic viability. Full article

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23 pages, 3216 KiB

Open AccessReview

A Review of Hydrogel Application in Wastewater Purification

by Lilyan Alsaka, Lina Alsaka, Ali Altaee, Syed Javaid Zaidi, John Zhou and Tayma Kazwini

Separations 2025, 12(2), 51; https://doi.org/10.3390/separations12020051 - 13 Feb 2025

Viewed by 470

Abstract

Hydrogels have garnered considerable interest in water purification owing to their distinctive physicochemical characteristics, including high porosity, modifiable surface chemistry, and superior water retention capacity. This paper provides a thorough examination of the use of hydrogels in wastewater treatment. It encompasses their categorization [...] Read more.

Hydrogels have garnered considerable interest in water purification owing to their distinctive physicochemical characteristics, including high porosity, modifiable surface chemistry, and superior water retention capacity. This paper provides a thorough examination of the use of hydrogels in wastewater treatment. It encompasses their categorization and separation procedures, including size exclusion, adsorption, electrostatic interactions, and non-sieving processes. Furthermore, it examines how functional groups improve the efficiency of pollutant removal. The review examines hydrogel composites and their filtering processes, measuring their efficacy in adsorption and evaluating the benefits and limits of hydrogels, especially regarding regeneration capacities. It explores hydration processes in hydrogels, emphasizing the fundamental mechanisms and measuring methods involved. Future research must prioritize optimizing hydrogel design to enhance mechanical strength and reusability, investigate innovative functionalization techniques to address emergent contaminants, and establish scalable manufacturing methods for extensive industrial use. Full article

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

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16 pages, 8670 KiB

Open AccessArticle

Research on the Flow Field Characteristics of the Industrial Elliptical Cyclone Separator

by Yongli Zhang, Kangshuo Li, Kaixuan Zhang, Guangfei Zhu, Zhanpeng Sun and Jianfang Shi

Separations 2025, 12(2), 50; https://doi.org/10.3390/separations12020050 - 13 Feb 2025

Viewed by 312

Abstract

A new type of elliptical cyclone separator has been proposed recently, but the flow field characteristics within the industrial device still need to be further investigated. In this paper, the characteristics of the flow field and particle motion inside the circular cyclone and [...] Read more.

A new type of elliptical cyclone separator has been proposed recently, but the flow field characteristics within the industrial device still need to be further investigated. In this paper, the characteristics of the flow field and particle motion inside the circular cyclone and the elliptical cyclone (with a long-to-short axis ratio of 1.2), with the equivalent hydraulic diameter of 300 mm, are comparatively analyzed using CFD methods. The results show that there is a significant change in the flow field distribution of the elliptical cyclone compared to the conventional circular cyclone. The static pressure gradient of the elliptical cyclone is anisotropic in the radial direction. The overall tangential velocity value is reduced, which reduces friction loss and makes the pressure drop of the elliptical cyclone significantly lower. More importantly, an acceleration/deceleration phenomenon of the airflow velocity occurs in the elliptical separator along the horizontal circumference, that is, the flow field is transformed into a circumferential fluctuating cyclonic field. This phenomenon induces an additional inertial separation effect that compensates for the unfavorable effects caused by the reduced centrifugal strength. Due to the coupling of centrifugal force and additional inertia effect, the residence time of small particles with a diameter of 1 micron in the elliptical cyclone is shorter, which helps to reduce the backmixing of particles and improves the separation efficiency of the elliptical cyclone. This study reveals the unique flow field characteristics of industrial elliptical cyclones, which is helpful to further understand the particle separation mechanism in the circumferential wave swirl field. Full article

(This article belongs to the Section Separation Engineering)

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15 pages, 4260 KiB

Open AccessArticle

Exploring the Photocatalytic Efficiency of Heterostructured TiO₂ Nanobelts for Emerging Liquid Contaminants in Different Water Matrices

by Humaira Asghar, Daphne Hermosilla, Antonio Gascó, Valter Maurino and Muhammad Ahsan Iqbal

Separations 2025, 12(2), 49; https://doi.org/10.3390/separations12020049 - 13 Feb 2025

Viewed by 346

Abstract

This study reports the development of shape-controlled TiO₂ (B)/anatase heterostructures for the degradation of emerging environmental pollutants, including phenol, methomyl (insecticides), and diclofenac sodium (drug), under UV-visible-light irradiation in ultrapure water and alkaline stormwater. TiO₂ nanobelts were synthesized via a surfactant-free [...] Read more.

This study reports the development of shape-controlled TiO₂ (B)/anatase heterostructures for the degradation of emerging environmental pollutants, including phenol, methomyl (insecticides), and diclofenac sodium (drug), under UV-visible-light irradiation in ultrapure water and alkaline stormwater. TiO₂ nanobelts were synthesized via a surfactant-free hydrothermal method, yielding structures with widths ranging from 40 to 80 nm and lengths extending up to several micrometers. The synthesized nanobelts were calcined at 400 °C, 600 °C, and 800 °C to form a TiO₂ (B)/anatase heterostructure. For comparison, calcination at 900 °C was also performed, resulting in the formation of pure anatase. The samples calcined at 800 °C (~92% anatase, ~8% nanobelts) exhibited enhanced photocatalytic efficiency, achieving significant total organic carbon (TOC) removal and complete mineralization in both water matrices. These findings contribute to a cost-effective method for developing efficient TiO₂ (B)/anatase heterostructures to avoid rapid charge carrier recombination, with strong potential for advanced wastewater treatment. Full article

(This article belongs to the Special Issue New Directions in Nanostructured Hybrid Materials for Selective Separations and Catalysis)

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20 pages, 6936 KiB

Open AccessArticle

Numerical Simulation and Optimization Design of Demister Based on a Separation Model Considering Re-Entrainment Influence

by Lei Zhang, Zongliang Qiao, Shasha Liu, Fei Feng and Youfei Tang

Separations 2025, 12(2), 48; https://doi.org/10.3390/separations12020048 - 13 Feb 2025

Viewed by 286

Abstract

In this paper, the separation characteristics of mist remover in a wet flue gas desulfurization system are numerically simulated, and the separation mechanism in the channel of mist remover is analyzed considering the influence of droplets on wall recombination, diffusion, and splash. Considering [...] Read more.

In this paper, the separation characteristics of mist remover in a wet flue gas desulfurization system are numerically simulated, and the separation mechanism in the channel of mist remover is analyzed considering the influence of droplets on wall recombination, diffusion, and splash. Considering the influence of re-entrainment, a gas–liquid separation model was established to reflect the coupling effect of air flow, droplets, and liquid film in the process of defogging. A computational model based on the energy loss coefficient κ was established, and the numerical simulation of flue gas flow in a single channel of a baffle demister was carried out using the computational fluid dynamics method. The effects of plate distance, plate angle, droplet diameter, and flue gas velocity on the separation efficiency were simulated and analyzed. Based on the response surface method, the model for separation characteristics and structure optimization design of the demister is established, and the influence level of each factor is analyzed. Full article

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10 pages, 1639 KiB

Open AccessArticle

Detection of Honey Adulteration by Liquid Chromatography—High-Resolution Mass Spectrometry: Results from an EU Coordinated Action

by Viviana Paiano, Andreas Breidbach, Carolin Lörchner, Tereza Ždiniaková, Olivier De Rudder, Alain Maquet, Lourdes Alvarellos and Franz Ulberth

Separations 2025, 12(2), 47; https://doi.org/10.3390/separations12020047 - 13 Feb 2025

Viewed by 476

Abstract

Honey, a sweet and nutritious food produced by honeybees, is extensively consumed by humans due to its potential health benefits. Unfortunately, the adulteration of honey with inexpensive sugar syrups is a prevalent issue. Verifying the authenticity of honey is crucial for maintaining its [...] Read more.

Honey, a sweet and nutritious food produced by honeybees, is extensively consumed by humans due to its potential health benefits. Unfortunately, the adulteration of honey with inexpensive sugar syrups is a prevalent issue. Verifying the authenticity of honey is crucial for maintaining its quality and safety standards. The aim of this study was to identify the illicit addition of sugar syrups to honey imported into the European Union (EU). The European Commission’s Joint Research Centre (JRC) has employed different analytical approaches to detect several markers of adulteration in honey; however, this paper mainly focuses on the use of Liquid Chromatography–High-Resolution Mass Spectrometry (LC-HRMS). Two qualitative methods were developed to detect mannose (Man), difructose anhydride III (DFA III), 2-acetylfuran-3-glucopyranoside (AFGP), and oligo-/polysaccharides with degrees of polymerization (DPs) of 6 to 11. Out of the 320 honey samples provided by the authorities of the participating EU Member States, 147 (46%) were suspicious for non-compliance with the EU Honey Directive 2001/110/EC, mostly due to the presence of mannose and oligo-/polysaccharides. As a result, the development and standardization of sophisticated and universally recognized testing procedures will increase the capability of official control laboratories to detect honey adulteration and will serve as a powerful preventive measure against fraudulent practices in the global honey market. 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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14 pages, 2617 KiB

Open AccessArticle

Headspace Determination of Acetone and Aromatic Hydrocarbons in Soil Using a Homebuilt, Inexpensive Gas Chromatograph with Photoionization Detection

by Cameron Shane, Carly M. Kennell, Michael J. Geyer, Thomas N. Loegel and Neil D. Danielson

Separations 2025, 12(2), 46; https://doi.org/10.3390/separations12020046 - 12 Feb 2025

Viewed by 339

Abstract

We have designed, built, and characterized an inexpensive gas chromatograph with photoionization detection using readily commercially available components. These include a home carbonation CO₂ cylinder for the carrier gas, headspace sampling using a low pressure six port valve, a standard 30 m [...] Read more.

We have designed, built, and characterized an inexpensive gas chromatograph with photoionization detection using readily commercially available components. These include a home carbonation CO₂ cylinder for the carrier gas, headspace sampling using a low pressure six port valve, a standard 30 m wide-bore capillary column, a consumer convection oven including added insulation with a thermocouple, and a photoionization sensor enclosed in a flow cell. The chromatography retention time reproducibility is good due to temperature control within 0.5 °C. The headspace linearity response using a 0.5 mL injection of benzene was from 10 to 250 ppm, with the limit of detection estimated at 4 ppm. The application of this instrument to the headspace monitoring of four soil samples spiked with a commercial adhesive cleaner containing acetone, ethyl benzene, and xylenes was possible. The interaction of acetone with the two different potting soil samples, likely due to their high organic content, was persistent for at least 30 min, even above an ambient temperature (60 °C). A comparison of linear plots of the signal versus volatilization time over the first 20 min showed substantially larger slopes for the two yard soil samples, indicating the rapid volatilization of acetone from these lower organic content soils, as compared to the two potting soil samples. This GC-PID instrument can be considered portable because it can be easily taken apart, transported, and reassembled. One viable option for the extension of the applications of this instrument is to provide hands-on teaching of GC. Full article

(This article belongs to the Section Chromatographic Separations)

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12 pages, 1415 KiB

Open AccessArticle

Recycling of Multilayer Flexible Packaging Waste Through Delamination with Recoverable Switchable Hydrophilicity Solvents

by Roberta Mastroddi, Chiara Samorì, Martina Vagnoni, Chiara Gualandi, Paola Galletti and Emilio Tagliavini

Separations 2025, 12(2), 45; https://doi.org/10.3390/separations12020045 - 11 Feb 2025

Viewed by 837

Abstract

Multilayer flexible packaging wastes (MFPWs) consist of complex materials composed of multiple plastic films, which are often laminated with aluminum foil, and they constitute a large portion of packaging waste. The use of several polymeric layers is essential to achieve the desired technical [...] Read more.

Multilayer flexible packaging wastes (MFPWs) consist of complex materials composed of multiple plastic films, which are often laminated with aluminum foil, and they constitute a large portion of packaging waste. The use of several polymeric layers is essential to achieve the desired technical and mechanical performance of the packaging; however, this makes layer separation and recycling challenging. Currently, this type of waste is predominantly incinerated or landfilled; non-industrial recycling processes have recently been developed, but they mostly rely on traditional solvent-based treatments, which can be problematic. We present a versatile process for recycling MFPWs using switchable hydrophilicity solvents (SHSs). By treating waste with SHSs through a temperature-controlled process, we efficiently recovered the polymeric layers as sorted transparent films, effectively removing all additives while preserving the original properties of the polymers. Aluminum was recovered as well. N,N-dimethylcyclohexylamine was the best solvent for the delamination of the 26 different packaging materials tested, containing polypropylene, polyethylene, polyethylene terephthalate, and aluminum. The main advantage of this method is the straightforward recovery of the different components that can be efficiently delaminated and easily removed from the solvent, even from highly variable input material. Moreover, by exploiting the CO₂-triggered switchable behavior of the solvent, its purification and recovery can be achieved, maintaining its delamination efficacy over several cycles. Full article

(This article belongs to the Special Issue Novel Solvents and Methods for Extraction of Chemicals)

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15 pages, 6707 KiB

Open AccessArticle

Chiral Separation and Determination of Enantiomer Elution Order of Novel Ketamine Derivatives Using CE-UV and HPLC-UV-ORD

by Elisabeth Seibert, Eva-Maria Hubner and Martin G. Schmid

Separations 2025, 12(2), 44; https://doi.org/10.3390/separations12020044 - 11 Feb 2025

Viewed by 518

Abstract

Besides the well-known hallucinogenic ketamine, various novel ketamine derivatives are available on the illicit drug market, sold as designer drugs. Minor chemical changes to the parent compound aim to circumvent existing narcotic drug laws while mimicking the effects of the original substance. Ketamine [...] Read more.

Besides the well-known hallucinogenic ketamine, various novel ketamine derivatives are available on the illicit drug market, sold as designer drugs. Minor chemical changes to the parent compound aim to circumvent existing narcotic drug laws while mimicking the effects of the original substance. Ketamine and some of its derivatives possess a chiral centre and therefore exist as two enantiomers. While differences in the effects of S- and R-ketamine are well studied, this is not the case for ketamine derivatives. Therefore, the development and adaptation of suitable enantioseparation methods for those compounds is important to face the problems of the constantly changing drug market. In this study, different chiral separation methods for capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) were tested on 11 ketamine derivatives. Some of them were enantioseparated for the first time due to their novelty. All compounds were at least partially separated on both instruments. HPLC separations were conducted using four different polysaccharide-based chiral stationary phases. Furthermore, an optical rotation detector coupled to the HPLC enabled the determination of the enantiomer elution order. In CE analysis, enantioseparation was achieved using 2% (w/v) acetyl-β-cyclodextrin or carboxymethyl- β-cyclodextrin in 10 mM di-sodium hydrogen phosphate as the background electrolyte in capillary electrophoresis. Full article

(This article belongs to the Section Chromatographic Separations)

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13 pages, 9286 KiB

Open AccessArticle

Investigations into Effects of Inclined Channels on the Forced Foam Drainage

by Yumeng Deng, Miao Jin, Lisha Dong, Jiakun Tan and Chao Ni

Separations 2025, 12(2), 43; https://doi.org/10.3390/separations12020043 - 8 Feb 2025

Viewed by 247

Abstract

Gangue particle entrainment during flotation remains a significant challenge in mineral processing. Previous studies have shown that incorporating inclined plates into the froth zone can reduce the recovery of fine gangue particles. However, the effects of inclined channels on froth drainage have not [...] Read more.

Gangue particle entrainment during flotation remains a significant challenge in mineral processing. Previous studies have shown that incorporating inclined plates into the froth zone can reduce the recovery of fine gangue particles. However, the effects of inclined channels on froth drainage have not been fully investigated. This study employed a custom-designed forced drainage system to systematically examine the impact of inclined channels on foam drainage and the underlying mechanisms. Results revealed that, at an SDS solution injection flow rate of 36 mL/min and an inclined channel angle of 30°, the foam drainage velocity in the inclined channel was significantly higher than that in the vertical channel for both two-phase and three-phase foams. This advantage became more pronounced as the SDS injection flow rate increased. A new drainage pathway formed between the inclined wall and the foam, facilitating faster liquid flow than within the foam structure. This mechanism was identified as the primary factor enhancing foam drainage velocity in inclined channels. These findings demonstrate that inclined channels can effectively improve foam drainage efficiency compared to vertical channels, providing valuable insights for optimizing froth zone structure. Full article

(This article belongs to the Special Issue Separation and Recovery Technology for Mineral Flotation and Solid Waste)

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20 pages, 6626 KiB

Open AccessArticle

In Situ N-Doped Low-Corrosion Porous Carbon Derived from Biomass for Efficient CH₄/N₂ Separation

by Huihui Wang, Yuqiong Zhao, He Lian, Qi Wang, Zhihong Shang and Guojie Zhang

Separations 2025, 12(2), 42; https://doi.org/10.3390/separations12020042 - 8 Feb 2025

Viewed by 284

Abstract

The separation of CH₄ and N₂ is essential for the effective use of low-concentration coalbed methane (CBM). In this study, a series of nitrogen-doped porous carbons were synthesized using an in situ nitrogen doping method combined with K₂CO₃ [...] Read more.

The separation of CH₄ and N₂ is essential for the effective use of low-concentration coalbed methane (CBM). In this study, a series of nitrogen-doped porous carbons were synthesized using an in situ nitrogen doping method combined with K₂CO₃ activation. The study systematically examined how changes in the physical structure and surface properties of the porous carbons affected their CH₄/N₂ separation performance. The results revealed that in situ nitrogen doping not only effectively adjusts the pore structure and alters the reaction of K₂CO₃ on the carbon matrix, but also introduces nitrogen and oxygen functional groups that significantly enhance the adsorption capabilities of the materials. In particular, sample S₃Y₆−800 demonstrated the highest methane adsorption capacity of 2.23 mmol/g at 273 K and 1 bar, outperforming most other porous carbons. This exceptional performance is attributed to the introduction of N-5, N-6, C-O, and COOH functional groups, as well as a narrower pore-size distribution (0.5–0.7 nm) and the formation of carbon nanotube structures. The introduction of heteroatoms also provides additional adsorption sites for the porous carbon, thus improving its methane adsorption capacity. Furthermore, dynamic breakthrough experiments confirmed that all samples effectively separated methane and nitrogen. The Toth model accurately described the CH₄ adsorption behavior on S₃Y₆−800 at 298 K, suggesting that the adsorption process follows a sub-monolayer coverage mechanism within the microporous regions. This study provides a mild and environmentally friendly preparation method of porous carbons for CH₄/N₂ separation. Full article

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

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19 pages, 2910 KiB

Open AccessReview

Techniques and Methods for Fatty Acid Analysis in Lipidomics: Exploring Pinus cembroides Kernels as a Sustainable Food Resource

by Luis Ricardo León-Herrera, Luis Miguel Contreras-Medina, Ana Angélica Feregrino-Pérez, Christopher Cedillo, Genaro Martín Soto-Zarazúa, Miguel Angel Ramos-López, Samuel Tejeda, Eduardo Amador-Enríquez and Enrique Montoya-Morado

Separations 2025, 12(2), 41; https://doi.org/10.3390/separations12020041 - 6 Feb 2025

Viewed by 486

Abstract

The large-scale conversion of forests to agriculture has caused biodiversity loss, climate change, and disrupted dietary fatty acid balances, with adverse public health effects. Wild edibles like pine nuts, especially Pinus cembroides, provide sustainable solutions by supporting ecosystems and offering economic value. [...] Read more.

The large-scale conversion of forests to agriculture has caused biodiversity loss, climate change, and disrupted dietary fatty acid balances, with adverse public health effects. Wild edibles like pine nuts, especially Pinus cembroides, provide sustainable solutions by supporting ecosystems and offering economic value. However, variability in seed quality limits market potential, and lipidomic studies on P. cembroides remain sparse. This paper underscores the ecological, social, and nutritional value of P. cembroides while advocating for advanced research to enhance its use as a non-timber forest resource in Mexico’s communal areas. It explores various analytical techniques, such as nuclear magnetic resonances (NMR), chromatography coupled with mass spectrometry (HPLC-MS, GC-MS) and GC coupled with flame ionization detector (GC-FID), highlighting extraction methods like derivatization, purification, and thin-layer chromatography. Likewise, some considerations are addressed for the treatment of data obtained in the detection of fatty acids from bioformatics and the evaluation of the data through statistical methods and artificial intelligence and deep learning. These approaches aim to improve fatty acid profiling and seed quality assessments, fostering the species economic viability and supporting sustainable livelihoods in rural communities, encouraging researchers across the country to explore the fatty acid composition of different P. cembroides populations can drive valuable insights into its nutritional and ecological significance. Such efforts can enhance understanding of regional variations, promote sustainable use, and elevate the specie’s economic and scientific value. Full article

(This article belongs to the Special Issue Extraction and Analysis of Chemical Composition from Natural Products and Metabolites)

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15 pages, 5808 KiB

Open AccessArticle

Synthesis of Zeolitic Imidazolate Framework-8 from Waste Electrodes via Ball Milling for Efficient Uranium Removal

by Minhua Su, Jinyao Zhu, Ruoning Wu, Jiaqi Pan, Jingran Yang, Jiaxue Zhao, Diyun Chen, Changzhong Liao, Kaimin Shih and Shengshou Ma

Separations 2025, 12(2), 40; https://doi.org/10.3390/separations12020040 - 6 Feb 2025

Viewed by 353

Abstract

Developing a cost-effective approach for the remediation of wastewater containing uranyl [U(VI)] ions is essentially important to ecosystems and human health. In this study, a Zn-based ZIF-8 framework was fabricated from wasted batteries through an environmentally friendly ball milling process featuring a distinct [...] Read more.

Developing a cost-effective approach for the remediation of wastewater containing uranyl [U(VI)] ions is essentially important to ecosystems and human health. In this study, a Zn-based ZIF-8 framework was fabricated from wasted batteries through an environmentally friendly ball milling process featuring a distinct microstructure compared to those synthesized from commercial Zn(II) sources. The as-obtained Zn-based ZIF-8 framework can effectively remove U(VI) ions from water, and a high removal efficiency of up to 99% is achieved across different process parameters, including initial dosage, pH values, and the presence of interfering ions. The superior U(VI) removal performance is attributed to the synergistic effect of microstructural features (e.g., crystallite size, specific surface area and pore diameter) and chemical interaction within the framework of Zn-based ZIF-8, resulting in the formation of the U···N chelates. This study integrates waste upcycling and hazardous U(VI) removal in an environmentally sound way, thereby promoting a circular economy. Full article

(This article belongs to the Section Environmental Separations)

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11 pages, 1947 KiB

Open AccessArticle

Exploring Chicken Feathers as a Cost-Effective Adsorbent for Aqueous Dye Removal

by Marcela Caovilla, Carolina E. Demaman Oro, Rúbia Mores, Luciana D. Venquiaruto, Marcelo L. Mignoni, Marco Di Luccio, Helen Treichel, Rogério Marcos Dallago and Marcus V. Tres

Separations 2025, 12(2), 39; https://doi.org/10.3390/separations12020039 - 6 Feb 2025

Viewed by 344

Abstract

This study explored the use of chicken feathers, a low-cost and abundant agricultural byproduct, as a sorbent for the removal of reactive yellow dye from aqueous solutions. The dual potential of feathers as both adsorbents and sorbents, attributed to their keratin-rich structure, was [...] Read more.

This study explored the use of chicken feathers, a low-cost and abundant agricultural byproduct, as a sorbent for the removal of reactive yellow dye from aqueous solutions. The dual potential of feathers as both adsorbents and sorbents, attributed to their keratin-rich structure, was utilized to investigate their effectiveness in dye removal. Feathers, activated with 1.0 mol/L HCl, exhibited a maximum adsorption capacity at 70 °C and pH 5.5, as determined from Langmuir isotherm modeling. A 2² central composite rotatable design revealed that temperature and pH significantly influence the adsorption efficiency, with higher temperatures favoring the process. Kinetic studies demonstrated pseudo-first-order behavior, with rapid initial adsorption reaching equilibrium within 120 min. Thermodynamic analysis confirmed the endothermic nature of the process (ΔH° = 28.04 kJ mol⁻¹), a positive entropy change (ΔS° = 66.62 J/mol·K), and a reduction in Gibbs free energy (ΔG°) with increasing temperature, suggesting enhanced feasibility at elevated temperatures. This research highlights the potential of utilizing poultry industry residues as sustainable and efficient sorbents for environmental remediation, contributing to waste valorization and eco-friendly wastewater treatment solutions. Full article

(This article belongs to the Special Issue Application of Sustainable Separation Techniques in Food Processing)

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13 pages, 3427 KiB

Open AccessArticle

Preparation, Characterization, and Mechanism of SMS Titanium–Manganese Nanocomposite for Antimony Removal from Water

by Yannan Lv, Wenqing Wen, Shenrui Han, Kaixin Li, Ziyu Fu, Fansong Mu and Meng Luo

Separations 2025, 12(2), 38; https://doi.org/10.3390/separations12020038 - 6 Feb 2025

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Abstract

This study investigates the synthesis of SMS-Ti-Mn (SMS-Ti-Mn stands for spent mushroom substrate activated carbon-Ti-Mn) nanocomposites and their application in removing the heavy metal antimony from water. In the process of antimony mining and smelting, the concentration of antimony in the waste residue [...] Read more.

This study investigates the synthesis of SMS-Ti-Mn (SMS-Ti-Mn stands for spent mushroom substrate activated carbon-Ti-Mn) nanocomposites and their application in removing the heavy metal antimony from water. In the process of antimony mining and smelting, the concentration of antimony in the waste residue can still reach as high as 80.5 mg/L. In addition, the soil in the electronic waste dismantling area is severely contaminated with antimony. In short, antimony enters the environment in various ways from mining, smelting, and manufacturing to the final waste process and continuously migrates in different environmental media, increasing the environmental exposure risk of antimony pollution. Single-factor experiments and response surface methodology were employed to determine the optimal conditions, including the adsorption time, pH, and solid–liquid ratio. Material characterization was performed to understand the role of nano-metals, and adsorption kinetics were analyzed using the quasi-first-order kinetic model. The research results revealed that the optimal conditions for antimony removal were an adsorption time of 40 min, a pH of 4, and a solid–liquid ratio of 2:1 (mg/mL). Under these conditions, the nanocomposites showed an adsorption capacity of 10.502 mg/g, which was 5.8 times higher than that of iron coagulants, 11 times higher than that of manganese-modified activated carbon, and 1.7 times higher than that of iron–manganese sludge adsorbents. Characterization revealed enhanced functional groups (carbonyl, Ti=O, Mn=O), contributing to improved adsorption. Kinetic analysis indicated physical adsorption as the dominant mechanism, and the regression model accurately predicted the adsorption capacity. SMS-Ti-Mn nanocomposites offer a promising strategy for treating antimony-contaminated water, with strong potential for practical applications in water treatment. They can decompose naturally after use, reduce secondary pollution, and promote ecological balance. Secondly, agricultural waste treated with heavy metal removal can be used as a fertilizer and soil amendment to improve soil quality and promote sustainable agricultural development. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Wastewater Treatment and Purification)

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12 pages, 1237 KiB

Open AccessArticle

Systematic Isolation and Characterization of Regenerated Hemicellulose and Lignin from Soybean Feedstocks Using Ionic Liquids

by Victor Essel and Douglas E. Raynie

Separations 2025, 12(2), 37; https://doi.org/10.3390/separations12020037 - 4 Feb 2025

Viewed by 526

Abstract

The use of ionic liquids in biomass pretreatment for ethanol production has seen increased attention in recent years. In this work, 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-allyl-3-methylimidazolium chloride ([Amim]Cl), and 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) were used to regenerate and recover significant amount of hemicellulose and lignin [...] Read more.

The use of ionic liquids in biomass pretreatment for ethanol production has seen increased attention in recent years. In this work, 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-allyl-3-methylimidazolium chloride ([Amim]Cl), and 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) were used to regenerate and recover significant amount of hemicellulose and lignin from soybean meal, flakes, and hulls. The regenerated lignin and hemicellulose were characterized using Fourier-transform infrared (FTIR) spectroscopy and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). For all three ionic liquids, the amount of regenerated hemicellulose and lignin ranged from approximately 6 to 12% and 8 to 19%, respectively. Lignin characteristic bands 1738.8, 1652.6, 1516.4, 1455.2, and 1174.9 cm⁻¹ were identified in the FTIR spectrum. The regenerated hemicellulose showed the characteristic bands 1658.31, 1434.14, 1167.98, and 865.20 cm⁻¹. The Py-GC/MS analysis of the regenerated lignin showed the characteristic grass lignin pyrolyzates phenol, 2-methoxyphenol, 4-methylphenol, 2-benzaldehyde, 2-methoxy-4-vinylphenol, phenol-2,6-dimethoxy, and ethylvanillin. Full article

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18 pages, 3696 KiB

Open AccessArticle

Investigation of Impurities in Peptide Pools

by Gaby Bosc-Bierne and Michael G. Weller

Separations 2025, 12(2), 36; https://doi.org/10.3390/separations12020036 - 2 Feb 2025

Viewed by 754

Abstract

Peptide pools are important research tools in different biomedical fields. They consist of a complex mixture of defined peptides, which places high demands on the production and quality control of these products. Previously it has been shown that the combination of UHPLC with [...] Read more.

Peptide pools are important research tools in different biomedical fields. They consist of a complex mixture of defined peptides, which places high demands on the production and quality control of these products. Previously it has been shown that the combination of UHPLC with high-resolution mass-spectrometry (HRMS) is a fast and powerful method to confirm the relative concentration and the structural identity of all peptides expected to be in the pool. In this work, the additional information contained in the UV chromatograms and mass spectra is used to search for impurities due to synthesis by-products and degradation during storage and transportation and to identify possible analytical artifacts. It was shown that most impurities are only present in trace amounts and can be considered uncritical for most applications. The most frequent and perhaps unexpected impurities were homo- and heterodimers caused by the free cysteines contained in these peptide pools. Furthermore, pyroglutamate and aspartimide formation, deamidation, methionine oxidation, and amino acid deletions could be found. This list is not intended to be comprehensive, but rather a brief guide to quickly identify impurities and, in the long term, to suggest possible changes in the composition of the peptide pools to avoid such impurities by design or by special precautions. Full article

(This article belongs to the Special Issue Peptide Synthesis, Separation and Purification)

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22 pages, 2745 KiB

Open AccessArticle

Critical Insights into Untargeted GC-HRMS Analysis: Exploring Volatile Organic Compounds in Italian Ambient Air

by Marina Cerasa, Catia Balducci, Benedetta Giannelli Moneta, Serena Santoro, Mattia Perilli and Vladimir Nikiforov

Separations 2025, 12(2), 35; https://doi.org/10.3390/separations12020035 - 2 Feb 2025

Viewed by 459

Abstract

This study critically examines the workflow for untargeted analysis of volatile organic compounds (VOCs) in ambient air, from sampling strategies to data interpretation by using GC-HRMS. While untargeted approaches are well-established in liquid chromatography (LC) due to advanced-deconvolution tools and extensive metabolomic libraries, [...] Read more.

This study critically examines the workflow for untargeted analysis of volatile organic compounds (VOCs) in ambient air, from sampling strategies to data interpretation by using GC-HRMS. While untargeted approaches are well-established in liquid chromatography (LC) due to advanced-deconvolution tools and extensive metabolomic libraries, their application in gas chromatography (GC) remains less developed, particularly for VOCs. The high structural isomerism of VOCs and the relative novelty of GC-based untargeted methodologies present unique challenges, including limited software tools and reference libraries. Air samples from suburban and rural sites in central Italy were analyzed to explore chemical diversity and address methodological gaps. This study evaluates critical decisions, such as sampling strategies, extraction techniques, and data-processing workflows, highlighting the limitations of automated deconvolution tools and the need for manual validation. Results revealed distinct source contributions, with suburban areas showing higher levels of anthropogenic compounds and rural areas dominated by biogenic emissions. This work underscores the potential of GC-HRMS untargeted analysis to advance environmental chemistry, while addressing key pitfalls and providing practical recommendations for reliable application. By bridging methodological gaps, it offers a roadmap for future studies aiming to integrate untargeted and targeted approaches in air quality research. Full article

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18 pages, 6241 KiB

Open AccessArticle

Optimizing Quercetin Extraction from Taraxacum mongolicum Using Ionic Liquid–Enzyme Systems and Network Pharmacology Analysis

by Jingwei Hao, Yifan Sun, Nan Dong, Yingying Pei, Xiangkun Zhou, Yi Zhou and Heming Liu

Separations 2025, 12(2), 34; https://doi.org/10.3390/separations12020034 - 28 Jan 2025

Viewed by 571

Abstract

Quercetin in Taraxacum mongolicum was extracted by ultrasound-assisted extraction in synergy with an ionic liquid–enzyme complex system, and the antioxidant function of quercetin was investigated based on network pharmacology. From 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium bromide, and 1-butyl-3-methylimidazolium tetrafluoroborate, the first [...] Read more.

Quercetin in Taraxacum mongolicum was extracted by ultrasound-assisted extraction in synergy with an ionic liquid–enzyme complex system, and the antioxidant function of quercetin was investigated based on network pharmacology. From 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium bromide, and 1-butyl-3-methylimidazolium tetrafluoroborate, the first step was to choose the appropriate ionic liquid. Subsequently, a response surface methodology and single-factor experiment were used to optimize the extraction process. The quercetin and the key targets for antioxidants were obtained from a public database. Antioxidant activity was assessed by measuring the scavenging rate of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and hydroxyl radicals(•OH). The approach revealed that the optimal extraction process was the liquid–solid ratio of 31.62:1 mL/g, enzymatic temperature of 55 °C, and the amount of cellulase added was 14.79% of the dry weight of dandelion. Under this condition, the yield of quercetin was 0.24 ± 0.011 mg/g, which was 1.3 times higher than that of the conventional reflux extraction method of 0.185 ± 0.015 mg/g. Pharmacological findings showed 57 cross-targets of quercetin with antioxidants. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that antioxidant function may be related to chemical carcinogenesis-reactive oxygen species, and the Phosphoinositide 3-kinase/protein kinase B signaling pathway. Quercetin has strong DPPH and •OH radical scavenging activity. The development and use of industrial dandelion are supported by this sustainable and effective method of extracting quercetin from dandelion. Full article

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20 pages, 1194 KiB

Open AccessReview

Research Progress in Tritium Processing Technologies: A Review

by Ziqian Zhao, Yandong Sun, Qi Chen, Tianchi Li, Fang Liu, Taihong Yan and Weifang Zheng

Separations 2025, 12(2), 33; https://doi.org/10.3390/separations12020033 - 27 Jan 2025

Viewed by 458

Abstract

Recent advancements in tritium separation technologies have significantly improved efficiency, particularly through the integration of vapor phase catalytic exchange (VPCE), liquid phase catalytic exchange (LPCE), and combined electrolysis catalytic exchange (CECE) methods. Combining these techniques overcomes individual limitations, enhancing separation efficiency and reducing [...] Read more.

Recent advancements in tritium separation technologies have significantly improved efficiency, particularly through the integration of vapor phase catalytic exchange (VPCE), liquid phase catalytic exchange (LPCE), and combined electrolysis catalytic exchange (CECE) methods. Combining these techniques overcomes individual limitations, enhancing separation efficiency and reducing energy consumption. The CECE process, which integrates electrolysis with catalytic exchange, offers high separation factors, making it effective for high-concentration tritiated water treatment. Solid polymer electrolyte (SPE) technology has also gained prominence for its higher efficiency, smaller equipment size, and longer lifespan compared to traditional alkaline electrolysis. While electrolysis offers high separation factors, its high energy demand limits its cost-effectiveness for large-scale operations. As a result, electrolysis is often combined with other methods like CECE to optimize both energy consumption and separation efficiency. Future research will focus on improving the energy efficiency of electrolysis for large-scale, low-cost tritiated water treatment. Full article

(This article belongs to the Special Issue Research on New Technology and Equipment of Multiphase Flow Separation)

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29 pages, 5477 KiB

Open AccessReview

Production of Algae-Derived Biochar and Its Application in Pollutants Adsorption—A Mini Review

by Luyang Li, Jinfeng Wang, Weiming Sun, Xinhong Peng and Xinhua Qi

Separations 2025, 12(2), 32; https://doi.org/10.3390/separations12020032 - 27 Jan 2025

Viewed by 1286

Abstract

Developing algae cultivation for food, chemicals, and bio-energy generates a significant amount of algal waste/residue after utilization. Meanwhile, harmful algal blooms caused by abnormal proliferation of various algae produce a large amount of algal biomass, posing serious harm to human health, the environment [...] Read more.

Developing algae cultivation for food, chemicals, and bio-energy generates a significant amount of algal waste/residue after utilization. Meanwhile, harmful algal blooms caused by abnormal proliferation of various algae produce a large amount of algal biomass, posing serious harm to human health, the environment and the economy. Converting algae body to biochar is a crucial method with which to take advantage of this resource. Biochar usually has a large specific surface area, developed pore structure, high cation exchange capacity and rich surface functional groups. With the advantage of stable physical/chemical properties and easy modification techniques, biochar posited as an ideal adsorption material. From the perspective of algal biomass utilization, this paper reviews the preparation and modification methods, structural characteristics, physicochemical properties and environmental implications of algal biochar. The adsorption effect and mechanisms of algal biochar on nutrients, heavy metals, and organic matter in water are introduced. In light of the current research status, the challenges faced in practical application of algae-derived biochar adsorption materials are pointed out, and a research direction for preparation and application is also developed, with a view to providing a reference for the further utilization of algae-derived biochar. Full article

(This article belongs to the Section Environmental Separations)

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13 pages, 44994 KiB

Open AccessArticle

Tuning the Inlet Flow Pattern of Cyclones for Boosted Particle Rotation Behaviors with High Purification Performances of Oily Sludge

by Rui Ye, Wan Zheng and Bi Shi

Separations 2025, 12(2), 31; https://doi.org/10.3390/separations12020031 - 26 Jan 2025

Viewed by 385

Abstract

Cyclone separation is a widely utilized separation technique, which enables the self-rotation behaviors of particles in the internal flow field, in order to realize high-performance separation of mixtures. Oily sludges are solid wastes generated by the shale gas industry, which need to be [...] Read more.

Cyclone separation is a widely utilized separation technique, which enables the self-rotation behaviors of particles in the internal flow field, in order to realize high-performance separation of mixtures. Oily sludges are solid wastes generated by the shale gas industry, which need to be properly treated for environmental protection. In the present investigation, we demonstrated that tuning the inlet flow pattern of the cyclone from linear flow to vortex flow is an effective approach to boost the rotation speed of oily sludge particles for obtaining significantly improved separation effects. Numerical simulations were carried out to investigate the influences of inlet flow pattern on the rotation behaviors of particles, which manifested in the rotation speed of particles being evidently increased up to 4500 rad/s when the inlet flow was tuned from a unidirectional pattern into vortex pattern. The effective rotation zone’s area was also found to increase significantly, with the area of the effective rotation zone enlarged by up to 400%. Further separation experiments on oily sludge were carried out using a cyclone equipped with a worm shell that generated vortex inlet flow with rotating blades. Separation results confirmed that the oily sludge was successfully purified by the cyclone equipped with a worm shell, which provided an extremely high oil removal percentage of 99.9%, showing a 49.1% enhancement in oil removal capability over the individual cyclone separation. Our investigations demonstrated an effective method for realizing oily sludge treatment and oil resource recovery by conventional cyclone separation. Full article

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23 pages, 3236 KiB

Open AccessTechnical Note

Techno-Economic and Feasibility Assessment of Membrane-Based Wastewater Treatment and Reuse in the Automotive Industry

by Sara Carvalho, Mário Eusébio and Svetlozar Velizarov

Separations 2025, 12(2), 30; https://doi.org/10.3390/separations12020030 - 26 Jan 2025

Viewed by 375

Abstract

The gradual increase in water scarcity due to depletion and/or inadequate use of water resources has affected the automotive sector. In this context, possibilities for water reuse in the pre-treatment tunnel in an automotive painting process were studied and compared with the primary [...] Read more.

The gradual increase in water scarcity due to depletion and/or inadequate use of water resources has affected the automotive sector. In this context, possibilities for water reuse in the pre-treatment tunnel in an automotive painting process were studied and compared with the primary goal of finding the most appropriate and economically viable water recovery solutions, considering a circular economy metric approach. To this end, an experimental campaign of aqueous effluent characterization, with determinations of most relevant chemical and physical parameters, was conducted in a company in the automotive industry sector. To reduce alkalinity and remove surfactants from the effluent of the washing phase, a cation exchange on a weak-acid-based resin was proposed along with a microfiltration membrane system with a recovery efficiency of 88%. The inclusion of subsequent ultrafiltration and reverse osmosis steps proved to be the most suitable for removing salts and biocides from the water of the cooling towers, treating approximately 68% of the water. The techno-economic feasibility was comprehensively evaluated according to the type of treatment used. A cost of EUR 245 thousand was estimated for the treatment of water from the degreasing washing phase (EUR 1.06 per manufactured car), and a cost of EUR 582 thousand was estimated for the treatment of the cooling towers’ water (EUR 2.52 per car). The estimated water income after the treatment systems’ implementation was estimated to be equal to EUR 0.07 per car for the washing stage and EUR 0.13 per car for the cooling towers. Ultimately, this study clearly demonstrated the beneficial contribution of using membrane treatment in the automotive sector’s environmental policy, leading to water reuse and much lower effluent discharge according to the principles of the circular economy. Full article

(This article belongs to the Special Issue Membranes Used in Water Purification)

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20 pages, 3734 KiB

Open AccessArticle

Strengthened Effect of Surface-Active Ionic Liquids on Curcumin Solubility and Extraction Performance of Curcuminoids

by Dan Li, Yuxin Qin, Jingxing Li, Subhan Mahmood, Jianqin Shi, Yu Cao and Shun Yao

Separations 2025, 12(2), 29; https://doi.org/10.3390/separations12020029 - 26 Jan 2025

Viewed by 303

Abstract

As a kind of bioactive component in the rhizome of natural plant Curcuma longa L. (turmeric), curcumin is almost insoluble in water at neutral and acidic pH, which limits its further utilization and development. At the same time, traditional extraction and separation processes [...] Read more.

As a kind of bioactive component in the rhizome of natural plant Curcuma longa L. (turmeric), curcumin is almost insoluble in water at neutral and acidic pH, which limits its further utilization and development. At the same time, traditional extraction and separation processes typically require the use of a large number of organic solvents. Ionic liquids (ILs) are organic molten salts with melting points below 100 °C. When an ionic liquid exists in a liquid state at or near room temperature, it is referred to as a room-temperature ionic liquid (RTIL). They have a temperature range, good physical and chemical stability, and good structural designability. They have a strong solubilization enhancement effect for many organic compounds. This study first explored the molecular forms of curcumin in ionic liquid aqueous solutions and the intermolecular interactions between curcumin and ionic liquids using spectral analysis and computational chemistry methods; furthermore, using an ionic liquid aqueous solution as an extraction agent, curcumin-like substances (curcuminoids) were extracted from turmeric powders under ultrasound assisted conditions, revealing the relationship between the structure of the ionic liquid and the extraction efficiency. After that, a kinetic study was conducted for the extraction of curcuminoids from turmeric powders, using second-order kinetics fitting to obtain the rate constant and initial extraction rate during the extraction process. Finally, the comparison with a ComplexGAPI tool and antioxidant experiment was performed on the extraction by using ionic liquids and traditional solvent. The full results can provide reference for the design of IL extractants and their application for natural products. Full article

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

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16 pages, 14086 KiB

Open AccessArticle

Effect of Washing Process on the Release of Microplastics from Polyester Fabrics

by Tanja Pušić, Nino Dimitrov, Ana Šaravanja, Ivona Vidić Štrac and Tihana Dekanić

Separations 2025, 12(2), 28; https://doi.org/10.3390/separations12020028 - 26 Jan 2025

Viewed by 371

Abstract

Microplastics (MP), consisting of particles under 5 mm in size, and fibrous microplastics (FMPs), which originate from textiles and are shed during the washing process, are acknowledged as a new and expanding category of pollutants. This study aimed to conduct an analytical evaluation [...] Read more.

Microplastics (MP), consisting of particles under 5 mm in size, and fibrous microplastics (FMPs), which originate from textiles and are shed during the washing process, are acknowledged as a new and expanding category of pollutants. This study aimed to conduct an analytical evaluation of the defragmentation process of polyester fabrics featuring a prominent tri-color pile surface. The evaluation involved washing the fabrics with detergent and water and employing various methods to assess the fabric, wastewater, and filter cake both prior to, and following, cryogenization. The specificity of a pile polyester fabric provided a baseline for evaluating the detergent and water system. Subjecting the polyester fabric to five cycles of washing in a detergent solution and water resulted in a measurable loss of mass. The pristine polyester fabric was analyzed microscopically and by FTIR, while the fabrics before and after washing were subjected to gravimetric analysis. The physico–chemical characteristics of the wastewater, such as the conductivity, turbidity, and chemical oxygen demand, were impacted by the composition of the washing bath. The application of pyrolysis, combined with gas chromatography and mass spectrometry (Py-GC/MS), on the filter cake demonstrated the value of using blank samples. The results indicated that both the detergent and the water significantly affected the release of FMPs during the washing process. Polyester fabric sample 1, which was washed in a detergent solution for five cycles, exhibited a mass loss of 1619 mg kg⁻¹. In contrast, sample 2, consisting of a polyester fabric washed solely in water, showed a mass loss of 1707 mg kg⁻¹ over the same number of cycles. Full article

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13 pages, 3850 KiB

Open AccessArticle

Electromigration Separation of Lithium Isotopes with the Benzo-12-Crown-4-Ether (B12C4) System

by Zhiyu Zhao, Lianjing Mao, Tianyu Zheng, Xiao Li, Chunsen Ye, Pengrui Zhang, Huifang Li, Wei Sun and Jinhe Sun

Separations 2025, 12(2), 27; https://doi.org/10.3390/separations12020027 - 26 Jan 2025

Viewed by 362

Abstract

Enriched lithium isotopes (⁶Li and ⁷Li) are essential in the nuclear energy industry, where ⁶Li is bombarded with neutrons to produce tritium for fusion reactions, while ⁷Li is used as a core coolant and pH regulator. Separation of [...] Read more.

Enriched lithium isotopes (⁶Li and ⁷Li) are essential in the nuclear energy industry, where ⁶Li is bombarded with neutrons to produce tritium for fusion reactions, while ⁷Li is used as a core coolant and pH regulator. Separation of ⁶Li and ⁷Li by electromigration is a promising method for producing enriched lithium isotopes that fulfill industrial needs. In this work, based on a previously proposed biphasic system electromigration routine, a three-stage system of ‘LiCl aqueous solution (anolyte)|B12C4-[EMIm][NTf₂] organic solution|NH₄Cl aqueous solution (catholyte)’ was constructed and the rules of lithium isotope separation and lithium-ion migration investigated. It was shown that the isotope enrichment effect of the catholyte was greatly affected by the experimental conditions, while that of the organic solution was less affected. As the B12C4 concentration increased, enhancement of ⁷Li enrichment in the catholyte and ⁶Li enrichment in the organic solution was observed, and α(C/O) and α(O/A) reached 0.975 and 1.018 at B12C4 of 0.5 mol/L. With the increase in current, migration time, and LiCl concentration, the isotope that was enriched in the catholyte trended from ⁷Li to ⁶Li (about 6 mA, 12 h or LiCl of 5 mol/L). Taking lithium-ion transport efficiency and lithium isotope separation effect into consideration together, a current of at least 6 mA, duration of at least 12 h, LiCl concentration of at least 1 mol/L and B12C4 concentration of 0.2 mol/L are suggested for the electromigration process. The work provides an important reference for system construction and experimental design of a biphasic electromigration separation method, which is expected to be an industrial alternative because of its environmental protection and high efficiency. Full article

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

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13 pages, 873 KiB

Open AccessArticle

HILIC-DAD Method for Simultaneous Determination of Acid and Basic Drugs: Application to the Quantitation of Ibuprofen, Atenolol, and Salbutamol in Urine After Solid-Phase Extraction

by Noelia Rosales-Conrado, Laura Pedrera-Cajas, Elvira Soliño-Rodríguez and María Eugenia León-González

Separations 2025, 12(2), 26; https://doi.org/10.3390/separations12020026 - 26 Jan 2025

Viewed by 552

Abstract

A simple method has been developed for the simultaneous analysis of ibuprofen (acid drug), and salbutamol and atenolol (basic drugs) in urine samples at concentrations of 0.40 µg·mL⁻¹. Simultaneous chromatographic separation has been possible using hydrophilic interaction liquid chromatography (Kinetex HILIC [...] Read more.

A simple method has been developed for the simultaneous analysis of ibuprofen (acid drug), and salbutamol and atenolol (basic drugs) in urine samples at concentrations of 0.40 µg·mL⁻¹. Simultaneous chromatographic separation has been possible using hydrophilic interaction liquid chromatography (Kinetex HILIC^® column (2.1 mm × 150 mm, 2.6 μm particle size diameter and 100 Å pore size) combined with gradient elution by employing a mixture of acetonitrile–acetate buffer 5 mM at pH 6 (from 95:5 to 75:25 (v/v)) as the mobile phase. Detection was performed at 227 and 275 nm. The simultaneous preconcentration and cleaning of the sample has been possible by solid-phase extraction using the HLB ExtraBond^® polymeric-type sorbent (which is a pyrrolidone-modified divinylbenzene polystyrene type). It has provided recoveries between (63 ± 9)% for salbutamol, (74 ± 8)% for ibuprofen, and (96 ± 9)% for atenolol in 10 mL of synthetic urine containing 4.0 μg of each of the drugs analyzed. The detection limits were 0.025 µg·mL⁻¹ for ibuprofen, µg·mL⁻¹ for salbutamol, and 0.007 µg·mL⁻¹ for atenolol. The detection limits obtained allow the evaluation of the free forms of ibuprofen, atenolol, and salbutamol at the excreted concentration levels at the therapeutic doses usually administered. The coefficients of variation between days were in the range 4.5–10.9%. Full article

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17 pages, 2312 KiB

Open AccessArticle

Green Chemistry Method for Analyzing Bisphenol A in Milk

by Angela M. Encerrado Manriquez and Wen-Yee Lee

Separations 2025, 12(2), 25; https://doi.org/10.3390/separations12020025 - 25 Jan 2025

Viewed by 417

Abstract

A simple, fast, green, and sensitive method for determining Bisphenol A (BPA) levels in commercial milk was developed using a solventless sample preparation technique known as stir bar sorptive extraction, coupled with thermal desorption–gas chromatography/mass spectrometry. BPA was selected due to its ubiquitous [...] Read more.

A simple, fast, green, and sensitive method for determining Bisphenol A (BPA) levels in commercial milk was developed using a solventless sample preparation technique known as stir bar sorptive extraction, coupled with thermal desorption–gas chromatography/mass spectrometry. BPA was selected due to its ubiquitous presence in the environment and its classification as an endocrine-disrupting chemical of concern (i.e., its ability to mimic hormone functions). Studies have reported that BPA can leach into various food sources, including milk, a dietary staple for infants. It is critical to have an effective and efficient process for monitoring the presence of BPA in milk to protect children’s health. Current detection methods for BPA in milk are lengthy and tedious and tend to require the use of organic solvents for the extraction of BPA. This optimized “green” method provides an effective alternative for BPA detection in a challenging matrix, e.g., milk. Factors such as pH (1.5, 6, and 13), temperature (70–80 °C), and sonication (1 h, 2 h, and 3 h) were studied with a BPA-spiked whole milk sample (final concentration of 8 ppb) to optimize the extraction efficiency without the use of solvents. The developed methodology improves BPA recovery from whole milk by over 50%, with a detection limit in the parts per trillion range (45 ng/L). The sample preparation developed in this report rendered a more sensitive option for analyzing BPA in milk, with a limit of detection in the parts per trillion range (compared to low ppb) even though the recovery performance is not as good as in reported studies (54% vs. >85%); nonetheless, it provides a green alternative for future studies assessing BPA exposure through dairy products. Full article

(This article belongs to the Special Issue Chromatographic Methods for Environment, Biota and Food Contaminants Analysis)

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Separations, Volume 12, Issue 2 (February 2025) – 37 articles

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