Separations

19 pages, 3282 KiB

Open AccessArticle

The Effect of Plasma Pretreatment on the Flotation of Lithium Aluminate and Gehlenite Using Light-Switchable Collectors

by Ali Zgheib, Maximilian Hans Fischer, Stéphanie Mireille Tsanang, Iliass El Hraoui, Shukang Zhang, Annett Wollmann, Alfred P. Weber, Ursula E. A. Fittschen, Thomas Schirmer and Andreas Schmidt

Separations 2024, 11(12), 362; https://doi.org/10.3390/separations11120362 - 23 Dec 2024

Viewed by 428

Abstract

The pyridinium phenolate punicine is a switchable molecule from Punica granatum. Depending on the pH, punicine exists as a cation, neutral molecule, anion, or dianion. In addition, punicine reacts to light, under the influence of which it forms radical species. We report [...] Read more.

The pyridinium phenolate punicine is a switchable molecule from Punica granatum. Depending on the pH, punicine exists as a cation, neutral molecule, anion, or dianion. In addition, punicine reacts to light, under the influence of which it forms radical species. We report on three punicine derivatives that possess an adamantyl, 2-methylnonyl, or heptadecyl substituent and on their performance in the flotation of lithium aluminate, an engineered artificial mineral (EnAM) for the recycling of lithium, e.g., from lithium-ion batteries. By optimizing the parameters: pH and light conditions (daylight, darkness), recovery rates of 92% of LiAlO₂ are achieved. In all cases, the flotation of the gangue material gehlenite (Ca₂Al[AlSiO₇]) is suppressed. IR, the contact angle, zeta potential measurements, TG-MS, and PXRD confirm that the punicines interact with the surface of LiAlO₂, which is covered by LiAl₂(OH)₇ after contact to water, resulting in a hydrophobization of the particle. The plasma pretreatment of the lithium aluminate has a significant influence on the flotation results and increases the recovery rates of lithium aluminate in blank tests by 58%. The oxidative plasma leads to a partial dehydratisation of the LiAl₂(OH)₇ and thus to a hydrophobization of the particles, while a reductive plasma causes a more hydrophilic particle surface. Full article

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

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18 pages, 2967 KiB

Open AccessArticle

Modified Biochar Adsorption Combined with Alkaline Solution Absorption for Sulfur-Containing Odor Gases Removal from Domestic Waste Transfer Stations

by Wei Wei, Ningjie Wang and Xiaolei Zhang

Separations 2024, 11(12), 361; https://doi.org/10.3390/separations11120361 - 23 Dec 2024

Viewed by 469

Abstract

Odor emission has become a major issue in waste transfer stations. Hydrogen sulfide, methyl mercaptan (MM), and dimethyl disulfide (DMDS) are the main odorous gases. They have a low odor threshold and are difficult to remove. In this study, pine bark biochar was [...] Read more.

Odor emission has become a major issue in waste transfer stations. Hydrogen sulfide, methyl mercaptan (MM), and dimethyl disulfide (DMDS) are the main odorous gases. They have a low odor threshold and are difficult to remove. In this study, pine bark biochar was produced and modified with metal ions, including Ni²⁺, Ti²⁺, Mn²⁺, Zn²⁺, Mg²⁺, and Cu²⁺. It was then used for the removal of hydrogen sulfide, methyl mercaptan, and dimethyl disulfide. Among all modifications, the Cu²⁺ modified biochar showed the best sorption capacity, and the maximum sorption amounts were 20.50 mg/g for H₂S, 36.50 mg/g for MM, and 57.98 mg/g for DMDS. To understand the adsorption, BET, SEM, and XPS of the original and modified biochar were performed. This illustrated that modification with Cu²⁺ increased the surface area and porosity, thus enhancing the adsorption capacity. In the alkaline absorption study, it was found that the removal of the three odor gases increased with the pH increase. Based on the results, a combined process called absorption–adsorption was established to treat the odor gas generated in a local waste transfer station. Thirty-one gas components were detected in the odor gas of the waste transfer station. The process proceeded for 30 days, and these gas components were not found in the effluent during treatment. Regarding H₂S, MM, and DMDS, they were not detected even after 90 days. This indicates the high adsorption capacity of the modified biochar toward the three odor gases. In addition, the process is simple and easy to operate. This suggests that it is suitable for treating odor in places where there is no technician, and the odor needs efficient treatment. The study provides a feasible alternative for domestic waste transfer stations to control the odor problem. Full article

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

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22 pages, 5851 KiB

Open AccessArticle

Ion Activity Coefficient of Sodium Halides in Anion-Exchange Polymers: Empirical Model Based on Manning’s Counterion Condensation Theory

by Guiming Liu and Dandan Gao

Separations 2024, 11(12), 360; https://doi.org/10.3390/separations11120360 - 23 Dec 2024

Viewed by 456

Abstract

The theory of electrolyte solution provides a precise description of the thermodynamic state and non-ideality of electrolyte solutions, allowing for the accurate prediction of the crystallization separation process of Salt Lake brine. Analogously, we attempt to describe the non-ideality of ions in ion-exchange [...] Read more.

The theory of electrolyte solution provides a precise description of the thermodynamic state and non-ideality of electrolyte solutions, allowing for the accurate prediction of the crystallization separation process of Salt Lake brine. Analogously, we attempt to describe the non-ideality of ions in ion-exchange polymers based on Manning’s Counterion Condensation Theory, which was originally used to describe the thermodynamics of polyelectrolyte solutions, has amply proven the potential to extend to ion-exchange polymers. In this article, equilibrium solvent and solute concentrations in aminated cross-linked polystyrene AEM were determined experimentally as a function of external NaCl concentration, and ion activity coefficients in the membranes were obtained via a thermodynamic treatment. With the recombination and empirical parameters added to Manning’s model, the ion activity coefficient of NaCl and NaBr in the aminated cross-linked polystyrene AEM can be accurately described in concentration ranges of 0.01 mol·kg⁻¹~3 mol·kg⁻¹. Compared with the original model, the Coefficient of Determination between the improved model and the experimental data was increased from 0.65 to 0.95. The Residual Sum of Squares is reduced by about one order of magnitude, significantly improving the Manning model’s adaptability when applied to AEM. 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, 3767 KiB

Open AccessArticle

Unveiling the Floral Scent Dynamics of Calamondin (Citrus × microcarpa) Across Developmental Stages

by Yiwei Chen, Zhiqing Liang, Shiyu Chen, Fulong Yan, Jingjuan He, Yiwei Zhou and Ting Gao

Separations 2024, 11(12), 359; https://doi.org/10.3390/separations11120359 - 23 Dec 2024

Viewed by 378

Abstract

The calamondin (Citrus × microcarpa) is highly valued for its ornamental appeal and rich aromatic compounds, making it suitable for therapeutic gardens and widely applicable in the cosmetics, food, pharmaceutical, and perfume industries. Despite its importance, there is a lack of [...] Read more.

The calamondin (Citrus × microcarpa) is highly valued for its ornamental appeal and rich aromatic compounds, making it suitable for therapeutic gardens and widely applicable in the cosmetics, food, pharmaceutical, and perfume industries. Despite its importance, there is a lack of research on its floral volatiles. This study utilized headspace solid-phase microextraction gas chromatography–mass spectrometry (HS–SPME–GC–MS) to detect the volatile organic compounds (VOCs) of calamondin at different floral developmental stages: bud (BS), half-open (HS), full bloom (FS), and senescence (SS). Multivariate statistical analysis was employed to elucidate the aromatic characteristics. The results identified 67 VOCs across the four stages, including forty-eight terpenoids, six esters, five aromatics, four aldehydes, one olefin, one alcohol, and two others. Thirty-three VOCs were common across all stages, while BS, HS, FS, and SS had three, three, four, and nine unique VOCs, respectively. The total VOC content increased initially and then decreased as the flowers developed, with terpenoids being the predominant compounds, accounting for over 90% of the total emissions at all stages. Principal component analysis and hierarchical cluster analysis confirmed significant differences in VOC profiles at different stages. Partial least squares discriminant analysis identified five VOCs with variable importance in projection (VIP) values greater than one, including limonene, linalool, β-pinene, germacrene D, and β-ocimene, indicating their varying emission levels across stages. These findings enhance our understanding of the VOC characteristics of calamondin flowers and provide a scientific basis for further ornamental and industrial applications. Full article

(This article belongs to the Special Issue Research Progress for Isolation of Plant Active Compounds)

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22 pages, 6794 KiB

Open AccessArticle

Metal Sulfide Nanoparticles as Sphalerite Surface Activators to Improve Zinc Recovery Through Flotation Process

by Delia Monserrat Ávila-Márquez, Alien Blanco-Flores, Helen Paola Toledo-Jaldin, Maribel González Torres, Alfredo Rafael Vilchis-Nestor, Iván Alejandro Reyes Domínguez and Ramiro de Aquino García

Separations 2024, 11(12), 358; https://doi.org/10.3390/separations11120358 - 22 Dec 2024

Viewed by 624

Abstract

CuS nanoparticles (Np) were synthesized and deposited on synthetic sphalerite (S_P) using two different methods. Two nanoparticle products were obtained on the surface of S_P, Np1 and Np2, resulting in two active materials (Np1-S [...] Read more.

CuS nanoparticles (Np) were synthesized and deposited on synthetic sphalerite (S_P) using two different methods. Two nanoparticle products were obtained on the surface of S_P, Np1 and Np2, resulting in two active materials (Np1-S_P and Np2-S_P) with specific characteristics. Nanoparticles and active materials were characterized by TEM, XRD, SEM, and XPS. The collectors PAX and SIPX were adsorbed on Np1-S_P and Np2-S_P to determine the adsorption capacity. Method 1 provides a higher quantity of nanoparticles on S_P, which allows for the adsorption of a higher amount of SIPX. Method 1 was used to deposit nanoparticles on two natural sphalerites (S_N) with different iron contents. S_N, unlike S_P, can be used to test nanoparticle activation results in microflotation experiments. S_N was activated with nanoparticles (Np1-S_N) and using the traditional method (Cu-S_N). The recovery of 75% of zinc using the microflotation process suggests that the hydrophobicity of Np1-S_N is higher than that of Cu-S_N. Nanoparticles improve the hydrophobicity of S_N compared to the traditional activation used in the mining industry. These results suggest that using nanoparticles is an excellent option to activate minerals in flotation processes, decreasing the consumption of reagents and helping to mitigate negative impacts on the environment. Full article

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

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14 pages, 1356 KiB

Open AccessArticle

Innovative Nafion- and Lignin-Based Cation Exchange Materials Against Standard Resins for the Removal of Heavy Metals During Water Treatment

by Sara Bergamasco, Luis Alexander Hein, Laura Silvestri, Robert Hartmann, Giampiero Menegatti, Alfonso Pozio and Antonio Rinaldi

Separations 2024, 11(12), 357; https://doi.org/10.3390/separations11120357 - 21 Dec 2024

Viewed by 524

Abstract

The contamination of water by heavy metals poses an escalating risk to human health and the environment, underscoring the critical need for efficient removal methods to secure safe water resources. This study evaluated the performance of four cationic exchange materials (labeled “PS—DVB”, “PA—DVB”, [...] Read more.

The contamination of water by heavy metals poses an escalating risk to human health and the environment, underscoring the critical need for efficient removal methods to secure safe water resources. This study evaluated the performance of four cationic exchange materials (labeled “PS—DVB”, “PA—DVB”, “TFSA”, and “OGL”) in removing or harvesting metals such as copper, silver, lead, cobalt, and nickel from aqueous solutions, several of which are precious and/or classified as Critical Raw Materials (CRMs) due to their economic importance and supply risk. The objective was to screen and benchmark the four ion exchange materials for water treatment applications by investigating their metal sequestration capacities. Experiments were conducted using synthetic solutions with controlled metal concentrations, analyzed through ICP-OES, and supported by kinetic modeling. The adsorption capacities (qe) obtained experimentally were compared with those predicted by pseudo-first-order and pseudo-second-order models. This methodology enables high precision and reproducibility, validating its applicability for assessing ion exchange performance. The results indicated that PS—DVB and PA—DVB resins proved to be of “wide range”, exhibiting high efficacy for most of the metals tested, including CRM-designated ones, and suggesting their suitability for water purification. Additionally, the second-life Nafion-based “TFSA” material demonstrated commendable performance, highlighting its potential as a viable and technologically advanced alternative in water treatment. Lastly, the lignin-based material, “OGL”, representing the most innovative and sustainability apt option, offered relevant performance only in selected cases. The significant differences in performance among the resins underscore the impact of structural and compositional factors on adsorption efficiency. This study offers valuable insights for investigating and selecting new sustainable materials for treating contaminated water, opening new pathways for targeted and optimized solutions in environmental remediation. Full article

(This article belongs to the Special Issue Separation Technology for Metal Extraction and Removal)

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18 pages, 9422 KiB

Open AccessArticle

Activating Peroxymonosulfate by a NovelFe-MOF-C/N Catalyst to Effectively Degrade Sulfamethoxazole: Catalyst Performance and Its Mechanism

by Zhaowei Wu, Meiyi Hu, Pengfan Zhuo, Jie Wang and Shaoping Tong

Separations 2024, 11(12), 356; https://doi.org/10.3390/separations11120356 - 21 Dec 2024

Viewed by 655

Abstract

A composite Fe-MOF-C/N was prepared with Fe-MOF and g-C₃N₄ precursors, and its activation property of peroxymonosulfate (PMS) in the degradation of Sulfamethoxazole (SMX) was studied. XRD, SEM, and TEM analyses showed that Fe-MOF-C/N was porous and mainly composed of phases [...] Read more.

A composite Fe-MOF-C/N was prepared with Fe-MOF and g-C₃N₄ precursors, and its activation property of peroxymonosulfate (PMS) in the degradation of Sulfamethoxazole (SMX) was studied. XRD, SEM, and TEM analyses showed that Fe-MOF-C/N was porous and mainly composed of phases of Fe₃N, C_0.08Fe_1.92, and graphite. XPS indicated that Fe-MOF-C/N mainly had Fe, C, N, and O elements, among which Fe existed in the form of Fe²⁺ and Fe³⁺. Fe-MOF-C/N was used to activate PMS to degrade SMX, and the result showed that Fe-MOF-C/N had excellent catalytic performance and 84.17% of SMX could be removed in 8 min. Free radical quenching experiments showed that ¹O₂ was the main active species in Fe-MOF-C/N/PMS. The stability experiment showed that Fe-MOF-C/N had good stability, and the degradation rate of SMX only decreased by 5.8% after five times of use. Full article

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16 pages, 12963 KiB

Open AccessArticle

Evaluating Bioflocculation Harvesting of Freshwater and Marine Microalgae Using Exopolysaccharides (EPSs) from Klebsiella sp.

by Yicheng Yuan, Jingxuan Lu and Quan Wang

Separations 2024, 11(12), 355; https://doi.org/10.3390/separations11120355 - 19 Dec 2024

Viewed by 544

Abstract

The rising global energy demand and environmental concerns associated with fossil fuels have intensified interest in sustainable biofuel sources, with microalgae emerging as a viable candidate due to its high biomass yield and efficient CO₂ conversion. However, the economic feasibility of microalgal [...] Read more.

The rising global energy demand and environmental concerns associated with fossil fuels have intensified interest in sustainable biofuel sources, with microalgae emerging as a viable candidate due to its high biomass yield and efficient CO₂ conversion. However, the economic feasibility of microalgal biofuels is currently challenged by costly harvesting processes. This study investigates the use of exopolysaccharides (EPSs) derived from Klebsiella sp. as an environmentally friendly bioflocculant for harvesting two microalgae species: Raphidocelis subcapitata and Dunaliella salina. Comparative flocculation experiments revealed that Klebsiella EPS promotes efficient aggregation in R. subcapitata, achieving over 90% flocculation efficiency, while performance with D. salina was impacted by high salinity, which reduced charge neutralization and bridging effects. Structural analyses using FTIR, 3D-EEM, CLSM, and XPS elucidated the EPS composition, underscoring the roles of polysaccharides and proteins in facilitating microalgal aggregation. The findings indicate that Klebsiella EPS offers a sustainable alternative to chemical flocculants, supporting eco-friendly biofuel production and potential applications in wastewater treatment. This approach provides insights into optimizing EPS-based flocculation for diverse environmental conditions, paving the way for more sustainable biomass recovery practices. Full article

(This article belongs to the Special Issue Separation Technology for Solid Waste Treatment and Recycling)

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22 pages, 8084 KiB

Open AccessArticle

Optimization of Extraction of Luteolin from Schisandra chinensis by Ionic Liquid–Enzyme Complex System and Antioxidant Study Analysis

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

Separations 2024, 11(12), 354; https://doi.org/10.3390/separations11120354 - 19 Dec 2024

Viewed by 527

Abstract

The luteolin in Schisandra chinensis [Schisandraceae Schisandra (Turcz.) Baill.] were extracted by ultrasonic extraction assisted by an ionic liquid–enzyme composite system, and the content of luteolins was determined using high-performance liquid chromatography (HPLC). This process was initially conducted through a one-factor experiment and [...] Read more.

The luteolin in Schisandra chinensis [Schisandraceae Schisandra (Turcz.) Baill.] were extracted by ultrasonic extraction assisted by an ionic liquid–enzyme composite system, and the content of luteolins was determined using high-performance liquid chromatography (HPLC). This process was initially conducted through a one-factor experiment and a Box–Behnken combinatorial design of response surface method. The extraction process was optimized, and the results demonstrated that the optimal extraction conditions were 13.31% enzyme addition, 0.53 mol/L ionic liquid concentration, 173.47 min ultrasonic shaking, and 0.2266 mg/g, which was 4.88 times higher than that of the traditional reflux extraction. Secondly, the antioxidant function of luteolins was studied based on network pharmacology. For the study of the antioxidant mechanism of luteolin, the herb group identification database, SwissTargetPrediction on luteolins target prediction, and GeneCards database to achieve the antioxidant target were used. For the analysis of the intersection of the target protein interactions, GO bioanalysis and KEGG signaling pathway enrichment analysis were used. There were 57 overlapping targets of luteolin and antioxidants, including AKT1, MMP9, ESR1, EGFR, and SRC. GO function and KEGG pathway enrichment analysis showed that luteolin antioxidants were related to zoerythromycin metabolic process, adriamycin metabolic process, negative regulation of apoptotic process, endocrine resistance and oxidoreductase. The key targets in the pathways, such as luteolin AKT1 and MMP9, exert antioxidant effects. The antioxidant activity of luteolins was investigated by determining the scavenging ability of luteolins against two types of free radicals: 2,2-bipyridine-bis(3-ethyl-benzothiazole-6-sulfonic acid) diammonium salt (ABTS+) free radicals and 1,1-diphenyl-2-trinitrophenylhydrazine free radicals (DPPH-). The results of the antioxidant test demonstrated that the ABTS radical scavenging rate was 87.26%, and the DPPH radical scavenging rate was 93.85% when the quality concentration of Schisandra luteolins was 0.1 mg/g, indicating the potential of this natural antioxidant. This method of extracting Schisandra chinensis luteolins is highly productive, environmentally friendly, and practical, and it facilitates the development and utilization of industrial Schisandra chinensis. Full article

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17 pages, 2035 KiB

Open AccessReview

The Removal of Organic Pollutants and Ammonia Nitrogen from High-Salt Wastewater by the Electro-Chlorination Process and Its Mechanism

by Yujun Zhou, Tangrui Hou and Bo Zhou

Separations 2024, 11(12), 353; https://doi.org/10.3390/separations11120353 - 18 Dec 2024

Viewed by 697

Abstract

Electro-chlorination (E-Cl) is an emerging and promising electrochemical advanced oxidation technology for wastewater treatment with the advantages of high efficiency, deep mineralization, a green process, and easy operation. It was found that the mechanism of pollutant removal by electro-chlorination mainly involves an indirect [...] Read more.

Electro-chlorination (E-Cl) is an emerging and promising electrochemical advanced oxidation technology for wastewater treatment with the advantages of high efficiency, deep mineralization, a green process, and easy operation. It was found that the mechanism of pollutant removal by electro-chlorination mainly involves an indirect oxidation process, in which pollutant removal is mainly driven by the intermediate active species, especially RCS and chlorine radicals, with a strong oxidization ability produced at the anodes. In this work, we summarized the principles and pathways of the removal/degradation of pollutants (organic pollutants and ammonia nitrogen) by E-Cl and the major affecting factors including the applied current density, voltage, electrolyte concentration, initial pH value, etc. In the E-Cl system, the DSA and BDD electrodes were the most widely used electrode materials. The flow-through electrode reactor was considered to be the most promising reactor since it had a high porosity and large pore size, which could effectively improve the mass transfer efficiency and electron transfer efficiency of the reaction. Of the many detection methods for chlorine radicals and RCS, electron paramagnetic resonance (EPR) and spectrophotometry with N, N-diethyl-1,4-phenylenediamine sulfate (DPD) as the chromogenic agent were the two most widely used methods. Overall, the E-Cl process had excellent performance and prospects in treating salt-containing wastewater. Full article

(This article belongs to the Special Issue Design and Preparation of Environmental Functional Materials for Pollutant Removal)

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16 pages, 2546 KiB

Open AccessEditor’s ChoiceArticle

Volatile Organic Compounds in Honey: Tandem Mass Spectrometry as Tool to Quantitate Priority VOCs

by Evangelia N. Tzanetou, Efstathia Vousaxaki, Kyriaki Machera, Jozef van der Steen and Konstantinos M. Kasiotis

Separations 2024, 11(12), 352; https://doi.org/10.3390/separations11120352 - 17 Dec 2024

Viewed by 492

Abstract

A headspace gas chromatographic tandem mass spectrometric (HS-GC-MS/MS) method was developed and fully validated, aiming for the simultaneous determination of 25 volatile organic compounds (VOCs, some of them previously unreported in honey bee studies) in 52 selected honey samples from Greece. The HS [...] Read more.

A headspace gas chromatographic tandem mass spectrometric (HS-GC-MS/MS) method was developed and fully validated, aiming for the simultaneous determination of 25 volatile organic compounds (VOCs, some of them previously unreported in honey bee studies) in 52 selected honey samples from Greece. The HS conditions were optimized, and method validation criteria were extensively investigated. The existence impact of the matrix effect was assessed, and matrix-matched calibration curves were developed for quantification purposes. The limits of quantification of the 25 analytes ranged from 0.2 ng g⁻¹ to 0.6 ng g⁻¹. Isoprene was the most commonly detected VOC, followed by octane and styrene. Other detected VOCs include benzene, n-hexane, trimethylbenzenes, xylenes, toluene, and p-dichlorobenzene. Concentrations fluctuated from 0.5 ng g⁻¹ for isoprene and toluene, as well as 1,2,4-trimethylbenzene, to 22.6 ng g⁻¹ for isoprene. Despite VOCs not being at the forefront of honey’s potential contamination, their prevalence in honey can provide significant data for human health risk assessment, considering their undisputable widespread consumption and the documented potential toxicity of VOCs in humans. In this sense, risk assessment for adults and children, as depicted in the hazard quotient and index and carcinogenic risk determination, did not disclose any potential threat after consumption of the investigated honey samples. Full article

(This article belongs to the Special Issue Chemical and Contaminant Residue Analysis via Chromatography)

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15 pages, 2867 KiB

Open AccessArticle

Rapid Classification of Unroasted Green Coffee Beans and Spices Based on the Tentative Determination of Volatile Compounds by Solid-Phase Dynamic Extraction (SPDE) and Gas Chromatography–Mass Spectrometry (GC–MS) with Supervised Learning

by Dimitrios G. Lazaridis, Evelyna K. Kokkosi, Emmanouela N. Mylonaki, Vassilios K. Karabagias, Nikolaos D. Andritsos and Ioannis K. Karabagias

Separations 2024, 11(12), 351; https://doi.org/10.3390/separations11120351 - 14 Dec 2024

Viewed by 562

Abstract

The present study comprises the second part of our previous work that dealt mainly with the phytochemical and physicochemical characterization of commercial unroasted green coffee beans, clove, cinnamon–clove and nutmeg ethanolic extracts of grape origin. In the present study, we focused on producing [...] Read more.

The present study comprises the second part of our previous work that dealt mainly with the phytochemical and physicochemical characterization of commercial unroasted green coffee beans, clove, cinnamon–clove and nutmeg ethanolic extracts of grape origin. In the present study, we focused on producing a discriminating model concerning commercial unroasted green coffee beans, clove, cinnamon, cinnamon and clove mixture (1:1, w/w), and nutmeg fine powders based on multivariate analysis of variance and supervised learning from tentative data of volatile compounds analysis, carried out with solid phase dynamic extraction in combination with gas chromatography–mass spectrometry. Results showed that 7 volatile compounds, i.e., ethylene, methanol, 3-methylpentane, ethyl acetate, 9-hexadecen-1-ol, toluene, and methyl acetate, could differentiate the investigated samples resulting in a 100% classification rate using the cross-validation method of linear discriminant analysis. Results were further confirmed using partial least squares regression analysis. The study contributes to the typification of commercial unroasted green coffee beans, cinnamon, clove, cinnamon and clove mixture, and nutmeg, based on selected volatile compounds. In addition, the study provides further support to the literature by means of a possible substitution of these products in rapid analysis tests, given the statistical models developed. 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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13 pages, 962 KiB

Open AccessArticle

Chan Seeds (Hyptis suaveolens L.) Storage Proteins: Isolation, Characterization, and Cytotoxic Effect on Three Cancer Cell Lines

by Elena Toribio-Nava, Yokiushirdhilgilmara Estrada-Girón, Gilberto Velázquez-Juárez, Janneth López-Mercado, Jorge I. Delgado-Saucedo, Paola Beatriz Castro-García, Martha Patricia Gallegos-Arreola, Asbiel Felipe Garibaldi-Ríos, Fabiola Rodríguez-Arevalo and Ana María Puebla-Pérez

Separations 2024, 11(12), 350; https://doi.org/10.3390/separations11120350 - 14 Dec 2024

Viewed by 418

Abstract

Since pre-Hispanic times, chan seeds (Hyptis suaveolens L.) have been used as food and in traditional medicine. However, there is still a lack of knowledge about the antioxidant capacity and cytotoxic effect of their storage proteins on cancer cells. Thus, these were [...] Read more.

Since pre-Hispanic times, chan seeds (Hyptis suaveolens L.) have been used as food and in traditional medicine. However, there is still a lack of knowledge about the antioxidant capacity and cytotoxic effect of their storage proteins on cancer cells. Thus, these were investigated in this study. The total protein content of the seeds was 19.5% (dry base), and its protein fractions were confirmed via Tris-Tricine-SDS-PAGE electrophoresis as 43.1% glutelins, 30.9% albumins, 23% globulins, and 2.9% prolamins. The antioxidant capacity determined by ABTS showed the highest percentage of inhibition for the prolamins fraction of 23.6% (half-maximal inhibitory concentration [IC50]: 1.38 µg protein/mL) and the lowest percentage for the glutelins fraction of 6.3% (IC50: 4.51 µg protein/mL). The cytotoxic activity against the murine lymphoma L5178Y, human cervical (Hela), and colorectal (Caco-2) cell lines revealed that prolamin exerted superior inhibition on the Hela and Caco-2 cancer cells, with IC50 values of 0.49 and 0.44 mg protein/mL, respectively. This study underscores the potential of chan seed proteins as natural antioxidants and anticancer agents. Full article

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17 pages, 6946 KiB

Open AccessReview

Utilization and Separation of Flavonoids in the Food and Medicine Industry: Current Status and Perspectives

by Jianan Wang, Bin Wang, Chunli Chen, Jingzhou Dong and Huafeng Zhang

Separations 2024, 11(12), 349; https://doi.org/10.3390/separations11120349 - 11 Dec 2024

Viewed by 678

Abstract

Flavonoids are the most abundant functional compounds distributed in higher plants, and are used as important dietary components for human health protection. The development of natural flavonoids, such as functional food or medicinal food, has received extensive attention in recent years. The extraction, [...] Read more.

Flavonoids are the most abundant functional compounds distributed in higher plants, and are used as important dietary components for human health protection. The development of natural flavonoids, such as functional food or medicinal food, has received extensive attention in recent years. The extraction, separation, and quantitation of flavonoids are the key techniques in the utilization of flavonoid resources. The traditional methods for flavonoid extraction and separation always used toxic solvents, which produce toxic residues and pollute the environment. Based on an analysis of the literature on flavonoid resources, the utilization, separation, quantitation, and green separation techniques of flavonoids were summarized. First, extraction by hot water or hot ethanol, assisted by pressurization and microwave-ultrasonication, then concentration and precipitation of flavonoids by cool water or cool ethanol or ethanol/water in specific ratios. This method could obtain over 85% purity in the first cycle and over 95% purity after three precipitation cycles in the separation of the most commonly used flavonoids, such as dihydromyricetin, rutin, and quercetin. In conclusion, flavonoids showed great prospects in human health protection and disease treatment. Chemical structure-based separation using the water–ethanol methods and assisted with microwave-ultrasonication, pressurization, and temperature regulation proved to be efficient and environmentally friendly, showing great potential for the flavonoid industry. These “green” processing techniques and mechanisms deserve further research. Full article

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

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10 pages, 2330 KiB

Open AccessArticle

The 288.2 K Isothermal Evaporation Experiment of Potassium Precipitation Brine in West Taijinair Salt Lake

by Yousheng Yang, Xiaowang Wu, Xudong Yu, Jiazheng Qin, Jianjun Su, Caixiong Quan and Pan Xu

Separations 2024, 11(12), 348; https://doi.org/10.3390/separations11120348 - 9 Dec 2024

Viewed by 554

Abstract

Rubidium and cesium are important strategic resources, and West Taijinar Salt Lake is rich in rubidium and cesium reserves, while the concentration is low and the relationship with coexisting potassium and magnesium ions is complex. In order to understand the evaporative enrichment and [...] Read more.

Rubidium and cesium are important strategic resources, and West Taijinar Salt Lake is rich in rubidium and cesium reserves, while the concentration is low and the relationship with coexisting potassium and magnesium ions is complex. In order to understand the evaporative enrichment and salt precipitation patterns of rare elements such as lithium, rubidium, cesium, and boron of the brine after potassium precipitation in West Taijinar Salt Lake, the 288.2 K isothermal evaporation experiment was carried out. The experimental results show that during the evaporation process at 288.2 K, the following salts precipitate from the brine after potassium crystallization: halite (NaCl), bischofite (MgCl₂·6H₂O), carnallite (KCl·MgCl₂·6H₂O), hexahydrite (MgSO₄·6H₂O), epsomite (MgSO₄·7H₂O), boric acid (H₃BO₃), and lithium sulfate monohydrate (Li₂SO₄·H₂O). The concentrations of lithium and boron are significantly enriched, the content of Li⁺ was enriched from 1.7 g/L to 5.63 g/L, and the B₂O₃ content was enriched from 6.72 g/L to 50.78 g/L. The isomorphism phenomenon of Rb⁺, Cs⁺, and K⁺ makes Rb⁺ and Cs⁺ enter potassium ore to form solid solution-type carnallite ((K, Rb)MgCl₃·6H₂O, (K, Cs)MgCl₃·6H₂O)) and reduce the content of brine. This study provides data support for the development and comprehensive utilization of lithium, boron, rubidium, and cesium resources in West Taijinar Salt Lake. Full article

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

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10 pages, 859 KiB

Open AccessCommunication

Some Aspects of the Use of Carbon Dioxide as a Carrier and Makeup Gas in GC–FID Analysis

by Łukasz Dąbrowski

Separations 2024, 11(12), 347; https://doi.org/10.3390/separations11120347 - 8 Dec 2024

Viewed by 415

Abstract

The paper presents the possibility of using carbon dioxide as a carrier gas in capillary gas chromatography (with a stationary liquid phase) to analyze semi-volatile compounds (boiling points of up to 400 °C). Based on the experiments carried out for compounds from the [...] Read more.

The paper presents the possibility of using carbon dioxide as a carrier gas in capillary gas chromatography (with a stationary liquid phase) to analyze semi-volatile compounds (boiling points of up to 400 °C). Based on the experiments carried out for compounds from the group of organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), the maximum volumetric flow rate (2.4 mL/min for CO₂) was determined, enabling the correct separation of the tested standard mixtures (except for two compounds from the OCP group: 4,4′-DDD and Endrin aldehyde and two other pairs of compounds with Rs slightly less than 1.5). Compared to using helium as a carrier gas (and makeup), carbon dioxide produces wider (about 1.6 times) and lower (about 1.8 times) peaks of analytes; these values can vary depending on the separation efficiency of the column. Carbon dioxide can also be effectively used as a makeup gas for the FID detector. The signal increase is comparable to that obtained with helium used as makeup (on average 40–50% depending on the carrier gas). When high sensitivity and high resolution are not required, CO₂ can be an alternative carrier and makeup gas to helium under the same flow conditions. The paper also describes practical aspects related to the implementation of CO₂ as a carrier and makeup gas in GC. Full article

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13 pages, 2164 KiB

Open AccessArticle

Eco-Friendly Capillary Electrophoresis Method for the Quantification of Apixaban in Oral Dosage Form

by Manoelly Oliveira Rocha, Amanda Mohr, Leandro Kolling, Marcia Messias da Silva, Jacqueline Arguello da Silva and Martin Steppe

Separations 2024, 11(12), 346; https://doi.org/10.3390/separations11120346 - 7 Dec 2024

Viewed by 693

Abstract

The present work describes, for the first time, an eco-friendly capillary zone electrophoresis (CZE) methodology for determining apixaban (APX), an oral anticoagulant. Separation was carried out using a fused silica capillary with an applied voltage of 20 kV and hydrodynamic injection for 5 [...] Read more.

The present work describes, for the first time, an eco-friendly capillary zone electrophoresis (CZE) methodology for determining apixaban (APX), an oral anticoagulant. Separation was carried out using a fused silica capillary with an applied voltage of 20 kV and hydrodynamic injection for 5 s at 50 mbar. The electrolyte system consisted of 50 mM sodium borate at pH 8.0. The method was validated as recommended by ICH, establishing selectivity, linearity, precision, accuracy, and robustness. The analytical procedure was linear in the range of 10–125 µg mL⁻¹ (r = 0.999). The limits of detection and quantification were determined to be 1.77 µg mL⁻¹ and 5.37 µg mL⁻¹, respectively. Precision was evaluated by relative standard deviation (RSD), with an intra-day RSD (n = 6) of 0.96% and an inter-day RSD (n = 18) of 4.42%. The average recovery rates for the pharmaceutical samples were excellent, ranging from 98.03% to 101.01%, with an RSD of 1.51%. Moreover, the green profile of the method was evaluated using the National Environmental Methods Index (NEMI), Analytical Eco-Scale, Green Analytical Procedure Index (GAPI), and Analytical GREEnness Metric (AGREE) assessment tools. The results suggest that the CZE method aligns with the principles of green chemistry, offering a greener alternative for the routine analysis of APX quality control. Also, the method presents a low-cost analysis, using fewer organic solvents and minimizing waste generation compared to techniques commonly used in routine analysis. Full article

(This article belongs to the Section Analysis of Natural Products and Pharmaceuticals)

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22 pages, 6605 KiB

Open AccessArticle

Technological Characterization of Cobalt and Nickel Ores from Greece for Metal Recovery

by Amina Eljoudiani, Carlos Hoffmann Sampaio, Josep Oliva, Moacir Medeiros Veras, Pura Alfonso, Hernan Anticoi, Stylianos Tampouris, Jose Luis Cortina and Percy Rodrigo Escalante

Separations 2024, 11(12), 345; https://doi.org/10.3390/separations11120345 - 6 Dec 2024

Viewed by 685

Abstract

Greece has mineral resources in which strategic elements such as nickel (Ni) and cobalt (Co) are present. In this study, characterizations of the metal concentrations of three laterite deposits, as well as minerals from a kiln originating from a mineral processing plant, were [...] Read more.

Greece has mineral resources in which strategic elements such as nickel (Ni) and cobalt (Co) are present. In this study, characterizations of the metal concentrations of three laterite deposits, as well as minerals from a kiln originating from a mineral processing plant, were carried out. The aim of this research was to integrate technological characterization data on the quantities of cobalt (Co) and nickel (Ni) present in the lateritic profiles of three mineral deposits from Greece and in kiln dust. The study was conducted at the Mineral Processing Laboratory of UPC/Bases Manresa. Aliquots were constituted for particle-size distribution tests by wet sieving followed by laser granulometry. Scanning electron microscopy (SEM) was used to determine the mineralogical compositions. Sink–float tests were conducted to estimate the particle liberation. Mineral liberation analysis (MLA) was performed to understand the liberation and the association of minerals in the samples. Full article

(This article belongs to the Special Issue Separation Technology for Metal Extraction and Removal)

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11 pages, 3928 KiB

Open AccessArticle

Effective Removal of Sr²⁺ Ions by K₂SbPO₆/Polyacrylonitrile Composite Microspheres

by Shuangjiang Li, Jianghai He, Yanling Guo, Lu Yang, Haiyan Sun, Meiling Feng and Xiaoying Huang

Separations 2024, 11(12), 344; https://doi.org/10.3390/separations11120344 - 3 Dec 2024

Viewed by 581

Abstract

⁹⁰Sr is one of the highly radioactive and hazardous nuclides in nuclear waste liquids. The high water solubility and mobility of ⁹⁰Sr²⁺ ions make it difficult to effectively remove ⁹⁰Sr from the complex aqueous environment. Herein, K₂SbPO [...] Read more.

⁹⁰Sr is one of the highly radioactive and hazardous nuclides in nuclear waste liquids. The high water solubility and mobility of ⁹⁰Sr²⁺ ions make it difficult to effectively remove ⁹⁰Sr from the complex aqueous environment. Herein, K₂SbPO₆, a phosphatoantimonate ion exchange material with an excellent removal ability for Sr²⁺ ions, has been organically granulated with polyacrylonitrile (PAN) by an automated method to form K₂SbPO₆/PAN composite microspheres. The K₂SbPO₆/PAN microspheres with radiation resistance exhibit a high maximum adsorption capacity (q_m^Sr) of 131.15 mg g⁻¹ for Sr²⁺ ions and retain the high removal rate (R^Sr) in a wide pH range (pH = 3–12). It is important that K₂SbPO₆/PAN microspheres could efficiently treat Sr²⁺ ions solutions in a dynamic adsorption manner even at 970 bed volumes (R^Sr > 81%). This work paves the way for the preparation of low-cost ion exchange materials with the advantages of regular shape and easy operation by a simple and fast method and the practical application of powdered ion exchange materials. Full article

(This article belongs to the Special Issue Separation Technology for Metal Extraction and Removal)

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19 pages, 4646 KiB

Open AccessArticle

Hazelnut Shells as a Tenable Biosorbent for Basic Red 18 Azo Dye Removal

by Naji Agilee, Tijana Spasojević, Milica Delić, Đorđe Ogrizović, Isabel R. Gria, Nevena Prlainović and Maja Đolić

Separations 2024, 11(12), 343; https://doi.org/10.3390/separations11120343 - 2 Dec 2024

Viewed by 771

Abstract

The increasing pollution from the textile industry, particularly organic azo dyes, presents a significant environmental challenge, necessitating the development of effective and sustainable treatment methods. This study investigates the adsorption potential of hazelnut shells (raw—RHSs; modified—MHSs) for the removal of organic azo dyes [...] Read more.

The increasing pollution from the textile industry, particularly organic azo dyes, presents a significant environmental challenge, necessitating the development of effective and sustainable treatment methods. This study investigates the adsorption potential of hazelnut shells (raw—RHSs; modified—MHSs) for the removal of organic azo dyes from aqueous solutions. As biomass, hazelnut shells are biodegradable and represent a sustainable alternative to synthetic adsorbents, thereby reducing the ecological footprint. Through a series of batch adsorption experiments, the influence of various parameters, including pH, contact time, concentration, and temperature, on adsorption capacity was examined. Characterization of the hazelnut shells was conducted using optical microscopy and ATR-FTIR, XRF, and XRD spectroscopy, confirming its suitability as a biosorbent. The analyzed isotherms showed that adsorption onto RHSs was best fitted by the Freundlich model, while adsorption onto MHSs was best fitted by the Temkin model. Kinetic studies demonstrated that the adsorption process is well described by the pseudo-second-order model, suggesting that chemical adsorption plays a significant role. The maximal adsorption capacity was 62.11 mg/g for RHSs and 80.65 mg/g for MHSs, highlighting the potential of hazelnut shells as an abundant, low-cost, and eco-friendly adsorbent. Furthermore, recycling studies indicated the feasibility of the adsorbent, underscoring its practical applicability in real scenarios. Full article

(This article belongs to the Special Issue Materials from Biomass and Waste for Adsorption Applications)

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44 pages, 489 KiB

Open AccessReview

Recent Developments (2020–23) on the Use of LC in the Determination of Food Contaminants

by A. P. Louppis and M. G. Kontominas

Separations 2024, 11(12), 342; https://doi.org/10.3390/separations11120342 - 28 Nov 2024

Viewed by 1196

Abstract

Food quality and safety are critical public health concerns, with approximately 600 million people worldwide being affected by foodborne diseases each year due to contamination. These diseases not only lead to a notable number of deaths but also impose substantial economic burdens, especially [...] Read more.

Food quality and safety are critical public health concerns, with approximately 600 million people worldwide being affected by foodborne diseases each year due to contamination. These diseases not only lead to a notable number of deaths but also impose substantial economic burdens, especially in low- and middle-income countries. Given the severe health risks posed by food contaminants, developing advanced, sensitive analytical methods to detect such contaminants is essential. Contemporary food safety challenges include detecting contaminants at trace levels and managing cumulative risks from simultaneous exposure to multiple chemicals. Liquid chromatography, particularly in combination with high-resolution mass spectrometry (LC/MS), has proven indispensable for detecting key contaminants such as perfluoroalkyl and polyfluoroalkyl substances, polycyclic aromatic hydrocarbons, pesticides, veterinary residues, packaging-derived contaminants, mycotoxins, and pyrrolizidine alkaloids in various food matrices. The present article reviews recent studies on the subject published between 2020 and 2023. Full article

(This article belongs to the Collection Liquid Chromatography: Its Effectiveness in Food Safety)

17 pages, 4437 KiB

Open AccessArticle

Study on Separation Kinetics of Non-Spherical Single Feeding Particle in the Gas–Solid Separation Fluidized Bed

by Xuchen Fan, Yuping Fu, Yongliang He and Liying Sun

Separations 2024, 11(12), 341; https://doi.org/10.3390/separations11120341 - 28 Nov 2024

Viewed by 526

Abstract

Gas–solid separation fluidized bed is an efficient and clean coal separation technology with a good separation effect for coal particles. However, there is a lack of systematic research on the complex motion behavior of the feeding particles in gas–solid separation fluidized beds. In [...] Read more.

Gas–solid separation fluidized bed is an efficient and clean coal separation technology with a good separation effect for coal particles. However, there is a lack of systematic research on the complex motion behavior of the feeding particles in gas–solid separation fluidized beds. In this study, the separation kinetics of non-spherical single feeding particles in the fluidized bed are examined. The particle sphericity coefficient Φ is introduced to characterize the morphology of irregular coal particles, and the drag coefficient for the feeding particles is modified to verify the suitability of the non-spherical particle drag model for gas–solid fluidized bed separation. After optimization and correction, a ρ_S.sus (the bed density when single feeding particles are suspended in the gas–solid separation fluidized bed) prediction model is obtained. When the prediction accuracy of the ρ_S.sus prediction model is 90%, the confidence degree is 85.72%. This ρ_S.sus of the single non-spherical feeding particle prediction model highlights a direction for improving the separation effect, provides a theoretical basis for the industrialization of gas–solid fluidized bed, and promotes the process of dry fluidized separation. Full article

(This article belongs to the Special Issue Research Progress of Gas–Solid Fluidized Dry Separation)

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19 pages, 4118 KiB

Open AccessArticle

A Convenient and Efficient Strategy for Improving Separation Ability of Capillary Electrophoresis Through Tilting Capillary as Needed

by Wenhui Jia, Pingyi Zheng, Yuchen Cui, James J. Bao, Yanmei Xu and Youxin Li

Separations 2024, 11(12), 340; https://doi.org/10.3390/separations11120340 - 27 Nov 2024

Viewed by 489

Abstract

The effect of gravity based on the vector sum of gravity and buoyancy forces working spontaneously for all species was introduced into capillary electrophoresis (CE) as another important force which cooperated with electrophoretic flow and electro-osmotic flow. Their portion was adjusted by simply [...] Read more.

The effect of gravity based on the vector sum of gravity and buoyancy forces working spontaneously for all species was introduced into capillary electrophoresis (CE) as another important force which cooperated with electrophoretic flow and electro-osmotic flow. Their portion was adjusted by simply tilting the whole of the capillary at an angle during CE running. The related formula was proposed and verified through a series of experiments. After investigating the related parameters, results showed that the gravity effect was significantly affected by additives in the buffer, the length, and the inner diameter of the capillary, and the size of the sample molecule. This made the different ions with opposite or significantly different mobilities to be observed at a CE run. It significantly improved separation efficiencies of some small molecules, chiral compounds, macromolecules and cells when the tilt angles of the capillary were adjusted to a special range predicted through the fitting curve. In addition, micrometer level microspheres and cells were firstly separated by the new CE strategy and the resolutions were more than 1.0. After ingeniously designing the gradient of the tilting angle with time, we were able to further enhance the separation efficiency of the targets. For example, the resolution of lysozyme and ribonuclease A could be increased from 3.691 to 7.342. These indicated the huge potential of the new CE strategy and its gradient mode in separation. Full article

(This article belongs to the Special Issue Development and Applications of Chromatographic Materials and Analytical Methods)

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14 pages, 2204 KiB

Open AccessArticle

Qualitative and Quantitative Analysis Method of Recombinant Collagen in Complex Matrix Based on HPLC-MS/MS

by Jianping Gao, Liping Jia, Zhenhu Guo, Liming Xu, Daidi Fan and Guifeng Zhang

Separations 2024, 11(12), 339; https://doi.org/10.3390/separations11120339 - 26 Nov 2024

Viewed by 636

Abstract

The purpose of this study is to achieve the quantitative detection of recombinant type III collagen (rh-COL-III) in dressings with complex matrix. First of all, the marker peptide (GEAGIPGVPGAK) of rhCOL-III was identified with HPLC-MS/MS. Then, a qualitative and quantitative method based on [...] Read more.

The purpose of this study is to achieve the quantitative detection of recombinant type III collagen (rh-COL-III) in dressings with complex matrix. First of all, the marker peptide (GEAGIPGVPGAK) of rhCOL-III was identified with HPLC-MS/MS. Then, a qualitative and quantitative method based on marker peptides was established and validated. In order to obtain higher sensitivity, a pretreatment method of liquid, gel, and ointment dressings was optimized. The reference material for quantification was combined using rhCOL-III and blank matrix of each dressing. The results indicated that the relative standard deviation (RSD) of the quantitative method was 2.77%, and the RSD of intraday and interday precision was 2.76% and 2.31%, respectively. The spiking recovery rate was between 80% and 90%. The optimal pretreatment method was Tris-HCl solvent replacement. The optimal trypsin concentration for the dressing solution was 20 μg in 500 μL. The method of preparing standard substances with a blank matrix can effectively eliminate the influence of the matrix effect on the quantitative results. The average spiking recovery rates of 50 μg/mL, 100 μg/mL, and 200 μg/mL in three different dressings ranged from 80% to 120%. The quantitative detection of limit (LOD) of rhCOL-III was 1 ng/mL, 2 ng/g, and 1 ng/g in liquid, ointment, and gel dressings. Full article

(This article belongs to the Topic Application of Liquid Chromatography-Mass Spectrometry and Related Techniques)

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22 pages, 956 KiB

Open AccessArticle

Theory of Gas Purification by Liquid Absorber in Small Rotating Channels with Application to the Patented Rotational Absorber Device

by J. J. H. Brouwers

Separations 2024, 11(12), 338; https://doi.org/10.3390/separations11120338 - 26 Nov 2024

Viewed by 447

Abstract

A new design for absorbing vapour-phase impurities from gases is presented. It consists of small channels packed in a rotating vertical cylinder. Gas flows through the channels adjacent to a thin film of absorber liquid. The liquid film is pressed to the radially [...] Read more.

A new design for absorbing vapour-phase impurities from gases is presented. It consists of small channels packed in a rotating vertical cylinder. Gas flows through the channels adjacent to a thin film of absorber liquid. The liquid film is pressed to the radially outward side of each channel by the centrifugal force and flows downwards by gravity. Formulae are presented which describe the concentration distributions of gaseous impurities subject to absorption in gas and liquid. Results include expressions for laminar and turbulent diffusion coefficients to be used in mass balance equations. The role of rotation is quantified including the effect on wavy motion and enhanced diffusion in the liquid layer. Application in design is indicated for the case of separation of the greenhouse gas

C O_{2}

from flue gases of fossil fuel combustion processes. At other equal dimensions, the height of the Rotational Absorber Device is calculated to be 25 times shorter than the enormous heights of conventional tray and packed columns. Full article

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20 pages, 11422 KiB

Open AccessArticle

Modified Fly Ash as an Adsorbent for the Removal of Pharmaceutical Residues from Water

by Marija Vukčević, Dušan Trajković, Marina Maletić, Miljana Mirković, Aleksandra Perić Grujić and Dragana Živojinović

Separations 2024, 11(12), 337; https://doi.org/10.3390/separations11120337 - 26 Nov 2024

Viewed by 731

Abstract

In this work, different methods for fly ash modification were applied to obtain an adsorbent for the efficient removal of selected pharmaceuticals from a multiclass aqueous solution. Morphological and surface properties of the modified fly ash samples were analyzed by scanning electron microscopy, [...] Read more.

In this work, different methods for fly ash modification were applied to obtain an adsorbent for the efficient removal of selected pharmaceuticals from a multiclass aqueous solution. Morphological and surface properties of the modified fly ash samples were analyzed by scanning electron microscopy, X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy, and point of zero charge, and the influence of the applied modifications was determined by comparison with the results obtained for unmodified fly ash. Experimental parameters of the adsorption of the pharmaceutical onto the modified fly ash were optimized, and special attention was paid to the influence of different parameters on the adsorption capacities. Multivariate methods of analysis, such as artificial neural networks, applied to the obtained results showed that the contact time, the initial concentration of the pharmaceutical solution, and the pH value had the strongest influence on the adsorption process. Fly ash modified with chitosan and magnetic iron oxide showed the best adsorption properties (removal efficiency above 80% for the majority of the selected pharmaceuticals), and artificial neural networks confirmed its susceptibility to the modeling process. Full article

(This article belongs to the Special Issue Materials from Biomass and Waste for Adsorption Applications)

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13 pages, 1187 KiB

Open AccessEditor’s ChoiceArticle

Body Volatilome Study Strategy for COVID-19 Biomarker Identification Considering Exogenous Parameters

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

Separations 2024, 11(12), 336; https://doi.org/10.3390/separations11120336 - 22 Nov 2024

Viewed by 766

Abstract

Since the 1950s, the screening of the body volatilome has proven to be a powerful tool for preventing diseases from spreading. Following the COVID-19 crisis, several studies began investigating the connection between viruses and the body volatilome, gradually identifying potential biomarkers, which varied [...] Read more.

Since the 1950s, the screening of the body volatilome has proven to be a powerful tool for preventing diseases from spreading. Following the COVID-19 crisis, several studies began investigating the connection between viruses and the body volatilome, gradually identifying potential biomarkers, which varied depending on the study. To try to elucidate potential sources of inconsistency in biomarker findings, we decided to set up a study taking into consideration the factors often overlooked in previous studies. The VOCs constituting the body volatilomes of 40 COVID-19 patients and 13 healthy subjects were sampled by using PowerSorb^® as the sorbent phase. Thermodesorption, followed by comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry (TD-GC×GC/TOF MS), was utilized for the analysis. A non-targeted biomarker research methodology compared Covid(+) and Covid(−) chromatograms, assessing statistical significance and peak area changes. Out of the 25 compounds highlighted, 13 associated with cosmetic products were excluded, and 8 linked to air pollution in urban settings were also excluded. Finally, after having quantitatively evaluated the potential sources of the compounds (cosmetic or environmental), 4 compounds remained and their relevance was assessed using ROC curves. Among them, hexanoic acid, 2-ethyl- identification was confirmed with standard and led to an area-under-the-curve value of 92%. More in-depth studies are needed to investigate the specificity of the biomarker in relation to COVID-19, but the strategy of this study shows how to avoid obtaining data that are biased by exogenous factors. Full article

(This article belongs to the Section Bioanalysis/Clinical Analysis)

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8 pages, 3294 KiB

Open AccessArticle

Aggregation-Dispersion Chromatography: Application of Elastin-like Polypeptides

by Han Bin Shin and Young Kee Chae

Separations 2024, 11(12), 335; https://doi.org/10.3390/separations11120335 - 21 Nov 2024

Viewed by 836

Abstract

Protein purification is a crucial step for various downstream applications like drug development, antibody preparation, and structure determination. The constant pursuit is for methods that are more efficient and cost-effective. We propose a novel approach using an elastin-like polypeptide (ELP) as an aggregation [...] Read more.

Protein purification is a crucial step for various downstream applications like drug development, antibody preparation, and structure determination. The constant pursuit is for methods that are more efficient and cost-effective. We propose a novel approach using an elastin-like polypeptide (ELP) as an aggregation core that serves as an anchor between the beads in a chromatography column. In this method, a chilled sample containing a [target protein type] fusion protein is loaded onto a pre-equilibrated IMAC (immobilized metal affinity chromatography) column with a low-salt buffer. The column is then washed with a warm buffer containing high salt to remove impurities. Here, the key step involves warming the column above the ELP’s transition temperature (Tt), which triggers its aggregation. This aggregation is expected to trap the target protein tightly between the beads. Subsequently, a harsh wash with high salt and high imidazole can be applied to remove even persistent contaminants, achieving high protein purity. Finally, the temperature is lowered, and a cold, low-salt buffer is introduced to reverse the aggregation and elute the purified target protein. This method has the potential to eliminate the need for sophisticated chromatography systems while still achieving high protein purity. Full article

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27 pages, 1465 KiB

Open AccessReview

Useful Extracts from Coffee By-Products: A Brief Review

by Krystyna Pyrzynska

Separations 2024, 11(12), 334; https://doi.org/10.3390/separations11120334 - 21 Nov 2024

Viewed by 743

Abstract

The waste materials generated from the processing of coffee cherries are still rich in several bioactive compounds. Several studies highlight coffee by-products as a valuable source for diverse applications, such as biofuels, biopolymers, biocomposites, and natural antioxidants in food, pharmaceuticals, and cosmetics. The [...] Read more.

The waste materials generated from the processing of coffee cherries are still rich in several bioactive compounds. Several studies highlight coffee by-products as a valuable source for diverse applications, such as biofuels, biopolymers, biocomposites, and natural antioxidants in food, pharmaceuticals, and cosmetics. The development of prospective strategies for the valorization of coffee wastes is a goal of a sustainable and circular bioeconomy, increasing the added value of these wastes and reducing environmental pollution. This brief overview describes the recently proposed procedures for the extraction and recovery of functional ingredients from the diversity of coffee by-products. The comparison between conventional and alternative extraction methods enables one to choose the most suitable techniques for valorizing a given coffee by-product. Full article

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

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19 pages, 6365 KiB

Open AccessArticle

Hierarchically Ordered Macroporous–Mesoporous (HOM-m) MgFe₂O₄/MgO for Highly Efficient Adsorption of Ce(III) and La(III): Experimental Study and DFT Calculation Analysis

by Lina Zhang, Jiarui Lu and Baixiong Liu

Separations 2024, 11(12), 333; https://doi.org/10.3390/separations11120333 - 21 Nov 2024

Viewed by 459

Abstract

This study employed a template method to prepare a highly ordered and interconnected porous HOM-m MgFe₂O₄/MgO rare earth ion-efficient adsorbent. The specific surface area of the adsorbent was as high as 130 m²/g, with saturation adsorption capacities [...] Read more.

This study employed a template method to prepare a highly ordered and interconnected porous HOM-m MgFe₂O₄/MgO rare earth ion-efficient adsorbent. The specific surface area of the adsorbent was as high as 130 m²/g, with saturation adsorption capacities for Ce(Ⅲ) and La(Ⅲ) of 5689.69 mg/g and 2123.50 mg/g, respectively. The adsorbent exhibited superparamagnetism with efficient and rapid separation from an aqueous solution using a magnet. The adsorption results indicated that the adsorption mechanism of HOM-m MgFe₂O₄/MgO towards Ce(III) and La(III) primarily involved the ion exchange and redox reactions between Mg(II) hydrolyzed from MgO and Ce(III)/La(Ⅲ), as well as the electrostatic attraction between MgFe₂O₄ and Ce(Ⅲ)/La(Ⅲ). Density functional theory (DFT) calculations revealed that the adsorption process was driven by the interaction of Ce(III) and La(III) ions with the surface oxygen atoms of MgFe₂O₄/MgO. Moreover, MgFe₂O₄/MgO showed a higher affinity and stronger adsorption effect towards Ce(III) than La(III). Adsorption cycling experiments demonstrated that even after three cycles, HOM-m MgFe₂O₄/MgO maintained good removal efficiency for Ce(III) and La(III). Therefore, this adsorbent shows promise as an effective material for removing Ce(III) and La(III) and has significant implications for the remediation of water resources in ion adsorption-type rare earth mining areas. Full article

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

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Separations, Volume 11, Issue 12 (December 2024) – 32 articles

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