Separations

15 pages, 3354 KiB

Open AccessArticle

A Hollow Hemispherical Mixed Matrix Lithium Adsorbent with High Interfacial Interaction for Lithium Recovery from Brine

by Yuyang Feng, Yifei Zhang, Lin Wang, Shiqiang Wang, Lina Xu, Senjian Han and Tianlong Deng

Separations 2024, 11(10), 301; https://doi.org/10.3390/separations11100301 (registering DOI) - 19 Oct 2024

Abstract

Mixed matrix lithium adsorbents have attracted much interest for lithium recovery from brine. However, the absence of an interfacial interaction between the inorganic lithium-ion sieves (LISs) and the organic polymer matrix resulted in the poor structural stability and attenuated lithium adsorption efficiency. Here, [...] Read more.

Mixed matrix lithium adsorbents have attracted much interest for lithium recovery from brine. However, the absence of an interfacial interaction between the inorganic lithium-ion sieves (LISs) and the organic polymer matrix resulted in the poor structural stability and attenuated lithium adsorption efficiency. Here, a novel hollow hemispherical mixed matrix lithium adsorbent (H-LIS) with high interfacial compatibility was constructed based on mussel-bioinspired surface chemistry using a solvent evaporation induced phase transition method. The effects of types of functional modifiers, LIS loading amount, adsorption temperature and pH on their structural stability and lithium adsorption performance were systematically investigated. The optimized H-LIS adsorbent with the LIS loading amount of 50 wt.% possessed the structural merit that the LIS functionally modified by dopamine exposed on both the inner and outer surfaces of the hollow hemispheres. At the best adsorption pH of 12.0, it showed a comparable lithium adsorption capacity of 25.68 mg·g⁻¹ to the powdery LIS within 4 h, favorable adsorption selectivity of Mg/Li and good reusability that could maintain over 90% of lithium adsorption capacity after the LiCl adsorption—0.25 M HCl pickling-DI water cleaning cycling processes for three times. The interfacial interaction mechanism of H-LIS for lithium adsorption was innovatively explored via advanced microcalorimetry technology. It suggested the nature of the Li⁺ adsorption process was exothermic and dopamine modification could reduce the activation energy for lithium adsorption from 15.68 kJ·mol⁻¹ to 13.83 kJ·mol⁻¹ and trigger a faster response to Li⁺ by strengthening the Li⁺-H⁺ exchange rate, which established the thermodynamic relationship between the structure and Li⁺ adsorption performance of H-LIS. This work will provide a technical support for the structural regulation of functional materials for lithium extraction from brine. Full article

(This article belongs to the Section Separation Engineering)

18 pages, 3713 KiB

Open AccessArticle

Retention Mechanisms of Basic Compounds in Liquid Chromatography with Sodium Dodecyl Sulfate and 1-Hexyl-3-Methylimidazolium Chloride as Mobile Phase Reagents in Two C18 Columns

by Carlos Josué Tereba-Mamani, Maria Celia Garcia-Alvarez-Coque and María José Ruiz-Ángel

Separations 2024, 11(10), 300; https://doi.org/10.3390/separations11100300 (registering DOI) - 19 Oct 2024

Abstract

Reversed-phase liquid chromatography (RPLC) relies on a non-polar stationary phase and a more polar hydro-organic mobile phase, where compound retention is primarily governed by hydrophobicity, with more hydrophobic compounds being retained longer. The introduction of secondary equilibria in the chromatographic system through additives, [...] Read more.

Reversed-phase liquid chromatography (RPLC) relies on a non-polar stationary phase and a more polar hydro-organic mobile phase, where compound retention is primarily governed by hydrophobicity, with more hydrophobic compounds being retained longer. The introduction of secondary equilibria in the chromatographic system through additives, such as anionic surfactants and ionic liquids (ILs), was proposed to mitigate ionic interactions between positively charged analytes and the anionic free silanol groups in non-endcapped stationary phases, thereby preventing increased retention and peak tailing. Additionally, the combined hydrophobic and ionic interactions between cationic analytes and the ions in these additives was demonstrated to create mixed retention mechanisms that influence retention and selectivity. In this regard, this study investigates aqueous chromatographic systems incorporating both the anionic surfactant sodium dodecyl sulfate (SDS) and the IL 1-hexyl-3-methylimidazolium chloride as mobile phase reagents. This combination of reagents modulates the retention, eliminating the need for organic solvents and resulting in highly sustainable HPLC procedures. The chromatographic behavior was assessed using two different C18 columns (Zorbax Eclipse and XTerra-MS). The strength of solute interactions was estimated by calculating equilibrium parameters and the contributions of hydrophobic and ionic interactions through simple mathematical models. Focusing on the retention of six basic drugs (β-adrenoceptor antagonists), the study highlighted the significant role of ionic interactions. The results demonstrate the feasibility of using aqueous systems combining SDS and an IL for the efficient separation of moderately polar basic compounds without the use of organic solvents. Full article

(This article belongs to the Section Chromatographic Separations)

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21 pages, 4102 KiB

Open AccessReview

Research Progress on Physical and Chemical Remediation Methods for the Removal of Cadmium from Soil

by Yonglin Mu, Chunhui Zhang, Yiyun Li, Weilong Zhou, Yanxin Li, Guifeng Zhao and Peidong Su

Separations 2024, 11(10), 299; https://doi.org/10.3390/separations11100299 - 17 Oct 2024

Viewed by 281

Abstract

Soil cadmium contamination is a global environmental issue, threatening ecosystem health and human safety. Common remediation strategies, including phytoremediation and soil replacement, are typically hampered by their lengthy processes or high costs. The aim of this review is to explore and evaluate innovative [...] Read more.

Soil cadmium contamination is a global environmental issue, threatening ecosystem health and human safety. Common remediation strategies, including phytoremediation and soil replacement, are typically hampered by their lengthy processes or high costs. The aim of this review is to explore and evaluate innovative physical and chemical remediation techniques to address cadmium pollution effectively. This review focuses on three promising approaches: the co-application of phosphate fertilizers and sepiolite, CaAl-layered double hydroxide (LDH) immobilization, and hydrochar treatments. The primary methodologies involved evaluating the adsorption capacity, ion exchange mechanisms, and remediation efficiency under varying environmental conditions. Results indicate that these techniques significantly enhance cadmium immobilization, with the co-application of phosphate fertilizers and sepiolite demonstrating up to 72.6% removal of HCl-extractable cadmium. The review concludes that these techniques offer superior cost-effectiveness and scalability for large-scale applications and recommends future research to optimize amendment formulations and develop renewable adsorbents to further improve sustainability. Full article

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17 pages, 2436 KiB

Open AccessReview

Treatment and Recycling of Tungsten Beneficiation Wastewater: A Review

by Wenxia Zhu, Jianhua Kang, Danxian Zhang, Wei Sun, Zhiyong Gao, Haisheng Han and Runqing Liu

Separations 2024, 11(10), 298; https://doi.org/10.3390/separations11100298 - 16 Oct 2024

Viewed by 502

Abstract

The large amount of wastewater containing various pollutants generated during the tungsten beneficiation process has become a bottleneck for the sustainable development of tungsten mining enterprises. Typical pollutants mainly include suspended solids (SSs), silicate ions, metal ions, and residual organic reagents. The direct [...] Read more.

The large amount of wastewater containing various pollutants generated during the tungsten beneficiation process has become a bottleneck for the sustainable development of tungsten mining enterprises. Typical pollutants mainly include suspended solids (SSs), silicate ions, metal ions, and residual organic reagents. The direct discharge of untreated tungsten beneficiation wastewater can cause serious harm to the ecological environment, while recycling can significantly affect flotation indicators. In this paper, the sources and characteristics of typical pollutants were analyzed, and various purification techniques were outlined, including coagulation, adsorption, chemical precipitation, oxidation, and biological treatment methods. Among these techniques, coagulation is particularly effective for the removal of SSs, while adsorption and chemical precipitation are recommended for the removal of soluble ions. For residual organic reagents, oxidation methods have demonstrated high treatment efficiencies. The mainstream methods for wastewater recycling were summarized, including centralized recycling, as well as internal recycling at certain stages. For tungsten beneficiation such a complex process, where the quality of wastewater varies greatly between different stages, it is suitable to recycle the wastewater after appropriate treatment at a specific stage. Furthermore, this study provided a perspective on the future directions of tungsten beneficiation wastewater treatment, serving as a reference for related research and industrial practices. Full article

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14 pages, 2938 KiB

Open AccessArticle

Study on Phosphorus Variability Characteristics and Response Mechanism of Microbial Community during Sediment Resuspension Process

by Bo Zhang, Yujia Liu, Haoran Yang, Peng Ji and Yunyan Guo

Separations 2024, 11(10), 297; https://doi.org/10.3390/separations11100297 - 14 Oct 2024

Viewed by 516

Abstract

Submerged plants and related disturbances can affect both the phosphorus (P) release and the microbial communities in sediments. In this study, a sediment resuspension system was constructed, and P variability characteristics influenced by Vallisneria natans (V. natans) and the response mechanism [...] Read more.

Submerged plants and related disturbances can affect both the phosphorus (P) release and the microbial communities in sediments. In this study, a sediment resuspension system was constructed, and P variability characteristics influenced by Vallisneria natans (V. natans) and the response mechanism of the microbial community were studied. The results indicated that the total phosphorus (TP) content increased from 678.875 to 1019.133 mg/kg and from 1126.017 to 1280.679 mg/kg in sediments and suspended solids (SSs) during the sediment resuspension process, respectively. Organic P (OP) increased by 127.344 mg/kg and 302.448 mg/kg in sediments and SSs after the disturbance, respectively. The microbial communities in the sediments and the leaves of V. natans had higher Chao values after the disturbance, while Shannon values decreased after the disturbance compared to the control in SSs. Proteobacteria had the highest abundance with the value of 51.1% after the disturbance in the sediments and SSs, and the abundance values of Proteobacteria in rhizomes and leaves of V. natans could reach 73.2% on average. Chloroflexi, Acidobacteria, and Firmicutes were also the main phyla in the sediment resuspension system. Sodium hydroxide extractable P (NaOH-P) in sediments could reduce the bioavailability of this P fraction under disturbance conditions. The decrease in the abundance of Bacteroidetes and Nitrospirae indicated that they were more sensitive to the disturbance, and the rotational speed changed the survival conditions for the Bacteroidetes and Nitrospirae. The response mechanism of microbial community during the sediment resuspension process could reflect the influence of the microbial community on the changing characteristics of P and could provide a theoretical foundation for P control at the micro level. Full article

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

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18 pages, 2924 KiB

Open AccessArticle

Comparison and Optimization of Three Extraction Methods for Epimedium polysaccharides

by Cheng Liu, Fangyuan Gong, Yijia Chen, Zhengwei Xiong, Cun Wang, Jiepei Li and Jin Guo

Separations 2024, 11(10), 296; https://doi.org/10.3390/separations11100296 - 14 Oct 2024

Viewed by 371

Abstract

Epimedium is used in traditional Chinese medicine. Epimedium polysaccharides have a variety of physiological properties. This study compared three different processes for the extraction of polysaccharides from Epimedium spp., including ultrasonic, aqueous enzymatic, and microwave extraction, to optimize the extraction conditions and determine [...] Read more.

Epimedium is used in traditional Chinese medicine. Epimedium polysaccharides have a variety of physiological properties. This study compared three different processes for the extraction of polysaccharides from Epimedium spp., including ultrasonic, aqueous enzymatic, and microwave extraction, to optimize the extraction conditions and determine the optimal extraction method. The optimal parameters for each method were analyzed. The results showed that the optimal process for ultrasonic extraction was an ultrasonic power of 250 W, an extraction time of 60 min, a temperature of 50 °C, and a solid–liquid ratio of 1:35. The optimal conditions for the aqueous enzymatic method were a papain concentration of 70 U/mL, extraction time of 70 min, a temperature of 50 °C, and a material-to-liquid ratio of 1:30, while those for microwave extraction were a microwave power of 650 W, an extraction time of 50 min, a temperature of 40 °C, and a material-to-liquid ratio of 1:25. The polysaccharide yields were 4.85%, 4.72%, and 3.98% for the three methods, respectively, indicating that ultrasonic extraction resulted in the highest yield of polysaccharides from Epimedium brevicornum. After purification with DEAE-cellulose, the polysaccharide yields were 4.13%, 3.67%, and 3.12%, respectively. A comprehensive comparison demonstrated the superiority of the ultrasonic extraction method in terms of both extraction yield and purification efficiency. Characterization of the extracted Epimedium polysaccharides showed the presence of five monosaccharides, i.e., glucose, galactose, mannose, galacturonic acid, and rhamnose, and a number average molecular weight Mn of 1.65 × 10⁵ Da and weight average molecular weight Mw of 6.61 × 10⁵ Da. These results provide a scientific basis for the in-depth study and application of Epimedium polysaccharides. Full article

(This article belongs to the Special Issue Separation and Purification of Functional Components of Foods and Herbs)

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10 pages, 1179 KiB

Open AccessArticle

Supercritical Extraction of Ylang Ylang (Cananga odorata) Essential Oil at the Near-Critical Region

by Rodney Mahabir, Sharad Maharaj, Marian J. Watson, David R. McGaw and Cian Coonai

Separations 2024, 11(10), 295; https://doi.org/10.3390/separations11100295 - 13 Oct 2024

Viewed by 384

Abstract

The flowers of the ylang ylang tree contain an essential oil which is utilized in high-quality perfumes. The traditional mode of extraction is by steam distillation but it has been shown that the more modern supercritical fluid extraction (SFE) using carbon dioxide has [...] Read more.

The flowers of the ylang ylang tree contain an essential oil which is utilized in high-quality perfumes. The traditional mode of extraction is by steam distillation but it has been shown that the more modern supercritical fluid extraction (SFE) using carbon dioxide has potential for replacing steam distillation. This technology, however, generally operates under high pressures, up to 500 bar. The work described in this paper examines the possibility of using carbon dioxide at much lower pressures, close to the critical point, i.e., 75 bar and 30 °C. Two series of experiments were therefore carried out under such conditions, the first using carbon dioxide alone and the second utilizing ethanol as a co-solvent, the conditions being chosen by applying the Design of Experiments (DOE) technique over ranges of pressure from 80 to 120 bar and temperatures from 35 to 50 °C. Extraction curves are presented which show the rates of extraction to be significantly increased by the use of the co-solvent, with the measured values being 0.74% to 0.97% with no co-solvent addition, increasing to 0.92% to 1.16% with co-solvent addition. These rates are, however, lower than the rates previously reported at higher pressures, i.e., 0.9 to 1.8%. Better quality oils are, however, produced compared to those at higher pressures, with the major components being benzene benzoate, benzene salicylate, cubebene, and benzyl acetate. It is recommended that an economic study be carried out to evaluate whether it is feasible to utilize this process commercially. 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, 2526 KiB

Open AccessArticle

Heavy Metal Removal from Water Using Graphene Oxide in Magnetic-Assisted Adsorption Systems: Characterization, Adsorption Properties, and Modelling

by A. P. Melchor-Durán, M. R. Moreno-Virgen, A. Bonilla-Petriciolet, H. E. Reynel-Ávila, E. Lucio Ortiz and O. F. González-Vázquez

Separations 2024, 11(10), 294; https://doi.org/10.3390/separations11100294 - 12 Oct 2024

Viewed by 645

Abstract

This study investigated the adsorption properties of graphene oxide in a magnetic-assisted adsorber for the depollution of water containing heavy metals. Two samples of graphene oxide with different surface chemistry were synthetized and assessed using the magnetic-assisted adsorption systems. One graphene oxide sample [...] Read more.

This study investigated the adsorption properties of graphene oxide in a magnetic-assisted adsorber for the depollution of water containing heavy metals. Two samples of graphene oxide with different surface chemistry were synthetized and assessed using the magnetic-assisted adsorption systems. One graphene oxide sample exhibited a dual magnetic behavior presenting both diamagnetic and ferromagnetic phases, while the other graphene oxide was diamagnetic. The adsorption properties of these graphene oxide samples for removing Pb²⁺ and Cu²⁺ were tested and compared with and without a magnetic field exposure. The results showed that the Pb²⁺ removal increased using both graphene oxide samples in the magnetic-assisted configuration, while Cu²⁺ adsorption was less sensitive to the application of the magnetic field. A monolayer model was used to simulate all the heavy metal adsorption isotherms quantified experimentally. It was concluded that the adsorption mechanism designed to remove Pb²⁺ and Cu²⁺ using tested graphene oxide samples was mainly multi-ionic where two metallic cations could interact with one active site (i.e., oxygenated functional groups) from the adsorbent surface. The oxygenated surface functionalities of graphene oxide samples played a relevant role in determining the impact of magnetic field exposure on the heavy metal removal efficacy. Magnetic-assisted adsorption using graphene oxide is an interesting alternative to reduce the concentration of Pb²⁺ in polluted effluents, and it can also be applied to improve the performance of adsorbents with a limited concentration of oxygenated functional groups, which usually show poor removal of challenging water pollutants such as toxic heavy metals. Full article

(This article belongs to the Special Issue Adsorption Process in Chemical Engineering)

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17 pages, 2804 KiB

Open AccessArticle

Quantitation of Copper Tripeptide in Cosmetics via Fabric Phase Sorptive Extraction Combined with Zwitterionic Hydrophilic Interaction Liquid Chromatography and UV/Vis Detection

by Pantelitsa Pingou, Anthi Parla, Abuzar Kabir, Kenneth G. Furton, Victoria Samanidou, Spyridon Papageorgiou, Efthimios Tsirivas, Athanasia Varvaresou and Irene Panderi

Separations 2024, 11(10), 293; https://doi.org/10.3390/separations11100293 - 12 Oct 2024

Viewed by 436

Abstract

The increasing demand for effective cosmetics has driven the development of innovative analytical techniques to ensure product quality. This work presents the development and validation of a zwitterionic hydrophilic interaction liquid chromatography method, coupled with ultraviolet detection, for the quantification of copper tripeptide [...] Read more.

The increasing demand for effective cosmetics has driven the development of innovative analytical techniques to ensure product quality. This work presents the development and validation of a zwitterionic hydrophilic interaction liquid chromatography method, coupled with ultraviolet detection, for the quantification of copper tripeptide in cosmetics. A novel protocol for sample preparation was developed using fabric phase sorptive extraction to extract the targeted analyte from the complex cosmetic cream matrix, followed by chromatographic separation on a ZIC^®-pHILIC analytical column. A thorough investigation of the chromatographic behavior of the copper tripeptide on the HILIC column was performed during method development. The mobile phase consisted of 133 mM ammonium formate (pH 9, adjusted with ammonium hydroxide) and acetonitrile at a 40:60 (v/v) ratio, with a flow rate of 0.2 mL/min. A design of experiments (DOE) approach allowed precise adjustments to various factors influencing the extraction process, leading to the optimization of the fabric phase sorptive extraction protocol for copper tripeptide analysis. The method demonstrated excellent linearity over a concentration range of 0.002 to 0.005% w/w for copper tripeptide, with a correlation coefficient exceeding 0.998. The limits of detection and quantitation were 5.3 × 10⁻⁴% w/w and 2.0 × 10⁻³% w/w, respectively. The selectivity of the method was verified through successful separation of copper tripeptide from other cream components within 10 min, establishing its suitability for high-throughput quality control of cosmetic formulations. Full article

(This article belongs to the Special Issue Analysis and Bioanalysis of Pharmaceuticals: Sample Preparation and Chromatography)

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13 pages, 2048 KiB

Open AccessArticle

Separation and Characterization of Wenjin Tongluo San Essential Oil with a Comprehensive Chromatographic Separation

by Chaoyue Wang, Xionggao Han, Guanglei Zuo and Jinghui Feng

Separations 2024, 11(10), 292; https://doi.org/10.3390/separations11100292 - 11 Oct 2024

Viewed by 310

Abstract

The essential oil components of traditional Chinese medicine in-hospital preparation were complex, and one-dimensional chromatographic separation was difficult to completely separate them due to the limited peak capacity. This study was carried out to establish a comprehensive two-dimensional chromatographic separation and analysis method [...] Read more.

The essential oil components of traditional Chinese medicine in-hospital preparation were complex, and one-dimensional chromatographic separation was difficult to completely separate them due to the limited peak capacity. This study was carried out to establish a comprehensive two-dimensional chromatographic separation and analysis method based on countercurrent chromatography (CCC) and gas chromatography (GC). In this paper, we focused on the separation of the essential oil of the traditional Chinese medicine in-hospital preparation Wenjing Tongluo San by CCC × GC, and explored the orthogonality between the two chromatographic techniques to provide the new technical support for the screening of the active ingredients. A solvent system composed of n-hexane-ethyl acetate-methanol-water (9.5:0.5:8.5:1.5, v/v) was chosen for the first-dimensional CCC separation. All the fractions collected from CCC were transferred to GC for plotting two-dimensional contours map. The calculated capacity of the two-dimensional separation system exceeded 3000, which was 8 times more than that of the one-dimensional separation system. High orthogonality (r = 0.42) and spatial coverage factor (70.42%) were obtained. Meanwhile, all the fractions were identified by GC-MS. Our research provided a new methodology for separating essential oils in traditional Chinese medicine as well as an approach for evaluating the quality of traditional Chinese medicinal in-hospital preparation based on two-dimensional chromatographic fingerprints. Full article

(This article belongs to the Special Issue The 10th Anniversary of Separations: Advances in Separation and Analysis of Natural Products/Medicines)

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64 pages, 8926 KiB

Open AccessReview

Emerging and Conventional Water Desalination Technologies Powered by Renewable Energy and Energy Storage Systems toward Zero Liquid Discharge

by Mahmoud M. Elewa

Separations 2024, 11(10), 291; https://doi.org/10.3390/separations11100291 - 11 Oct 2024

Viewed by 1616

Abstract

The depletion of fossil fuels has become a significant global issue, prompting scientists to explore and refine methods for harnessing alternative energy sources. This study provides a comprehensive review of advancements and emerging technologies in the desalination industry, focusing on technological improvements and [...] Read more.

The depletion of fossil fuels has become a significant global issue, prompting scientists to explore and refine methods for harnessing alternative energy sources. This study provides a comprehensive review of advancements and emerging technologies in the desalination industry, focusing on technological improvements and economic considerations. The analysis highlights the potential synergies of integrating multiple renewable energy systems to enhance desalination efficiency and minimise environmental consequences. The main areas of focus include aligning developing technologies like membrane distillation, pervaporation and forward osmosis with renewable energy and implementing hybrid renewable energy systems to improve the scalability and economic viability of desalination enterprises. The study also analyses obstacles related to desalination driven by renewable energy, including energy storage, fluctuations in energy supply, and deployment costs. By resolving these obstacles and investigating novel methodologies, the study enhances the understanding of how renewable energy can be used to construct more efficient, sustainable, and economical desalination systems. Thermal desalination technologies require more energy than membrane-based systems due to the significant energy requirements associated with water vaporisation. The photovoltaic-powered reverse osmosis (RO) system had the most economically favourable production cost, while MED powered via a concentrated solar power (CSP) system had the highest production cost. The study aims to guide future research and development efforts, ultimately promoting the worldwide use of renewable energy-powered desalination systems. Full article

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15 pages, 2136 KiB

Open AccessArticle

Development, Validation, and Greenness Assessment of Eco-Friendly Analytical Methods for the Determination of Abiraterone Acetate in Pure Form and Pharmaceutical Formulations

by Erten Akbel

Separations 2024, 11(10), 290; https://doi.org/10.3390/separations11100290 - 11 Oct 2024

Viewed by 508

Abstract

This study presents the development and validation of environmentally friendly analytical methods for quantifying Abiraterone Acetate (AA) in both its pure form and commercial pharmaceutical formulations. An optimized High-Performance Liquid Chromatography (HPLC) method was developed using an Agilent Extend C18 column (250 mm [...] Read more.

This study presents the development and validation of environmentally friendly analytical methods for quantifying Abiraterone Acetate (AA) in both its pure form and commercial pharmaceutical formulations. An optimized High-Performance Liquid Chromatography (HPLC) method was developed using an Agilent Extend C18 column (250 mm × 4.6 mm, 5 μm) at 25 °C. The mobile phase consisted of formic acid and ethanol in isocratic mode, with a flow rate of 1.0 mL min⁻¹, and detection was performed at 253 nm. The spectrophotometric method involved a comprehensive evaluation of AA’s spectral properties in various solvents, with ultrapure water providing the most suitable spectra for analysis at 253 nm. Both methods were validated according to ICH guidelines, demonstrating selectivity, linearity, accuracy, precision, detection and quantification limits, and robustness, with correlation coefficients exceeding 0.999 across the 5–30 μg mL⁻¹ concentration range. Comparative statistical analysis using Student’s t-test and Fisher’s F-test showed no significant differences between the two methods. The environmental impact of both methods was assessed using AGREE and GAPI software, confirming their sustainability. These validated methods offer reliable and eco-friendly approaches for the quantitative analysis of AA in tablet formulations, promoting safer and greener laboratory practices in pharmaceutical analysis. Full article

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

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16 pages, 2520 KiB

Open AccessArticle

Dehydration by Pervaporation of an Organic Solution for the Direct Synthesis of Diethyl Carbonate

by Kouessan Aziaba, Marco Annerl, Gerhard Greilinger, Magdalena Teufner-Kabas, Florian Kabas, Christian Jordan and Michael Harasek

Separations 2024, 11(10), 289; https://doi.org/10.3390/separations11100289 - 10 Oct 2024

Viewed by 394

Abstract

Pervaporation has been a central subject in the research community within the scope of the further development of energy- and cost-efficient alternatives to conventional liquid–liquid separation technologies. The potential eligibility of four commercial membranes (ZEBREX ZX0, PERVAP^TM 4155-80, PERVAP^TM 4100, PERVAP [...] Read more.

Pervaporation has been a central subject in the research community within the scope of the further development of energy- and cost-efficient alternatives to conventional liquid–liquid separation technologies. The potential eligibility of four commercial membranes (ZEBREX ZX0, PERVAP^TM 4155-80, PERVAP^TM 4100, PERVAP^TM 4101) for use in an integrated dehydration application of a diethyl carbonate/water/ethanol mixture by pervaporation was assessed experimentally. The impact of feed concentration, operating temperature, pressure, and sweep gas flow rate on membrane separation performance, including permeation flux, permeate quality, selectivity, and permeance, was thoroughly investigated. Applying the ZX0 membrane delivered the best qualities of all tested membranes of the permeate stream, with a water concentration of mostly >98%. In comparing the water flux, the ZX0 membrane remained reasonably competitive with the polymer membranes. Furthermore, the sweep gas volume flow rate and the operating temperature were identified as influencing the flux significantly but not the product composition. At the same time, the feed concentration of water also influenced the water purity within the permeate. The experiments were monitored with a partial least squares model, allowing a quick assessment of obtained samples while delivering accurate results. Full article

(This article belongs to the Section Separation Engineering)

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17 pages, 4277 KiB

Open AccessArticle

Comparative Analysis of Acid Leaching for the Efficient Recovery of Lanthanum and Cerium from Phosphate

by Rinat Abdulvaliyev, Almagul Ultarakova, Arailym Mukangaliyeva, Nina Lokhova and Kaisar Kassymzhanov

Separations 2024, 11(10), 288; https://doi.org/10.3390/separations11100288 - 10 Oct 2024

Viewed by 515

Abstract

The extraction of rare earth elements (REEs) from mineral resources is of significant global importance due to their critical role in modern technologies. This study focuses on the leaching behavior of artificial cerium and lanthanum phosphates using nitric, sulfuric, and hydrochloric acids under [...] Read more.

The extraction of rare earth elements (REEs) from mineral resources is of significant global importance due to their critical role in modern technologies. This study focuses on the leaching behavior of artificial cerium and lanthanum phosphates using nitric, sulfuric, and hydrochloric acids under varying conditions of acid concentration and temperature. Our experiments demonstrated that the maximum extraction efficiency of lanthanum and cerium was achieved with nitric acid solutions at concentrations of 12.5 mol/dm³, with 85.0% and 79.1% extraction efficiency, respectively. The leaching mechanism involved the protonation of phosphate anions, which disrupted the phosphate matrix, facilitating the dissolution of lanthanum and cerium into solution. Sulfuric acid, although less effective at room temperature, proved to be the most thermodynamically favorable leaching agent at higher temperatures due to the formation of stable sulfate complexes. Additionally, hydrochloric acid displayed high selectivity for cerium extraction, although its applicability is limited by complexation and environmental concerns. This study offers new insights into optimizing REE recovery from phosphates, demonstrating the advantages of sulfuric acid for industrial-scale leaching processes due to its economic and thermodynamic benefits. The novelty of this work lies in its systematic comparison of the three acids’ effects on REE extraction, providing a comprehensive framework for selecting optimal leaching agents based on specific operational conditions. Full article

(This article belongs to the Section Separation Engineering)

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13 pages, 3128 KiB

Open AccessReview

Systematic Assessment of Practical Challenges in Rural Domestic Sewage Treatment in China: Examining Treatment Models, Ecological Risks, and Management Dilemmas

by Yi Gao, Luoyu Wei, Yihong Ge, Xia Xiong, Ming Liu, Xiaomei Jiang, Ke Pan, Xiaobo Guo, Yunhui Lei and Nuan Yang

Separations 2024, 11(10), 287; https://doi.org/10.3390/separations11100287 - 9 Oct 2024

Viewed by 499

Abstract

The treatment and purification of rural domestic sewage (RDS) is a pivotal focus in enhancing the living environment in rural areas. Since 2008, special funds for comprehensive rural environmental improvement have been established by the Chinese government. Numerous projects have been implemented to [...] Read more.

The treatment and purification of rural domestic sewage (RDS) is a pivotal focus in enhancing the living environment in rural areas. Since 2008, special funds for comprehensive rural environmental improvement have been established by the Chinese government. Numerous projects have been implemented to treat RDS, resulting in a significant enhancement of China’s rural sewage treatment ratio. However, current discussions often focus on technical investigations, process selection, and operation modes pertaining to urban sewage while overlooking the unique challenges posed by decentralized sewage treatment facilities in rural areas. This work aims to provide technical support for addressing rural sewage treatment and purification in China through an analysis of limitations associated with prevailing mainstream sewage treatment and separation technologies, ecological risks arising from new pollutants present in domestic wastewater, and subsequent management difficulties. Full article

(This article belongs to the Special Issue Bioelectrochemical Treatment and Purification of Wastewater)

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15 pages, 1399 KiB

Open AccessArticle

Bioactives in Berry Fruits with Emphasis on In Vitro Bioaccessibility for Human Nutrition

by Iulia Varzaru, Arabela Elena Untea, Alexandra Gabriela Oancea, Mihaela Saracila and Petru Alexandru Vlaicu

Separations 2024, 11(10), 286; https://doi.org/10.3390/separations11100286 - 6 Oct 2024

Viewed by 391

Abstract

This study aimed to investigate the bioaccessibility and biostability of carotenoids, vitamin E isomers, and individual polyphenolic compounds after the in vitro gastrointestinal digestion of two types of berries (raspberry and blackberry fruits). The results of the polyphenols analysis showed that raspberry fruits [...] Read more.

This study aimed to investigate the bioaccessibility and biostability of carotenoids, vitamin E isomers, and individual polyphenolic compounds after the in vitro gastrointestinal digestion of two types of berries (raspberry and blackberry fruits). The results of the polyphenols analysis showed that raspberry fruits contained higher concentrations of hydroxybenzoic acids, hydroxycinnamic acids, flavanols, and flavonols compared to blackberry fruits, but exhibited the lowest bioaccessibility values for all the studied polyphenol classes. Ellagic acid represented 13.63% and 2.65% of the hydroxybenzoic acids in raspberry and blackberry fruits. The hydroxybenzoic acids exhibited the highest bioaccessibility index in the intestinal phase of both types of berries, and gallic acid emerged as one of the most bioaccessible phenolic compounds. The bioaccessibility of carotenoids ranged between 15.7 and 17.30% for lutein, 5.52 and 7.56% for astaxanthin, and 7.85 and 9.93% for canthaxanthin, with elevated values being observed in raspberry fruits. Although vitamin E and carotenoids follow a similar path for absorption, the bioaccessibility of vitamin E isomers was higher than that of carotenoids, with γ-tocopherol being the most bioaccessible isomer in both raspberries and blackberries. Knowing the bioaccessibility of food constituents during digestion is crucial, as the potential effectiveness of bioactives for human health largely depends on the bioavailability of these molecules. Full article

(This article belongs to the Special Issue Isolation and Identification of Biologically Active Natural Compounds)

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6 pages, 654 KiB

Open AccessArticle

On the Specific Diclofenac–Iron Cation Interaction for Selective Diclofenac Removal from a Water Solution

by Magdalena Frańska and Aleksandra Grześkowiak

Separations 2024, 11(10), 285; https://doi.org/10.3390/separations11100285 - 5 Oct 2024

Viewed by 306

Abstract

Diclofenac is one of the most common, commercially available, non-steroidal anti-inflammatory drugs (NSAIDs) in the world, with thousands of tons produced and consumed per year, which creates issues related to its presence in water bodies and the need for its removal from them. [...] Read more.

Diclofenac is one of the most common, commercially available, non-steroidal anti-inflammatory drugs (NSAIDs) in the world, with thousands of tons produced and consumed per year, which creates issues related to its presence in water bodies and the need for its removal from them. Diclofenac forms complexes with cations of each metal, which has inspired a study to check if the formation/precipitation of such complexes can be used for effective diclofenac removal from water solutions. It was found that iron salts, e.g., FeCl₃, can be used to remove diclofenac from a water solution in the form a of precipitated complex, provided that a high excess of iron salt was used. It has been observed that the diclofenac initial concentration of 5 × 10⁻⁴ M, as a result of FeCl₃ addition, after 48 h, decreased by two orders of magnitude. Salts of other metals were found less effective in reducing diclofenac concentration. The iron cation–diclofenac interaction was found to be specific, since the precipitation of other drugs by iron cations has not been observed. In order to quantitively analyze the diclofenac removal (precipitation) by iron and other metal cations, the HPLC/ESI-MS analyses were performed. Full article

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21 pages, 6854 KiB

Open AccessReview

Process Intensification of Gas–Liquid Separations Using Packed Beds: A Review

by Yafang Zhang, Chencan Du, Zhibo Zhang, Jiawei Du, Yuming Tu and Zhongqi Ren

Separations 2024, 11(10), 284; https://doi.org/10.3390/separations11100284 - 2 Oct 2024

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Abstract

The gas–liquid multiphase process plays a crucial role in the chemical industry, and the utilization of packed beds enhances separation efficiency by increasing the contact area and promoting effective gas–liquid interaction during the separation process. This paper primarily reviews the progress from fundamental [...] Read more.

The gas–liquid multiphase process plays a crucial role in the chemical industry, and the utilization of packed beds enhances separation efficiency by increasing the contact area and promoting effective gas–liquid interaction during the separation process. This paper primarily reviews the progress from fundamental research to practical application of gas–liquid multiphase processes in packed bed reactors, focusing on advancements in fluid mechanics (flow patterns, liquid holdup, and pressure drop) and the mechanisms governing gas–liquid interactions within these reactors. Firstly, we present an overview of recent developments in understanding gas–liquid flow patterns; subsequently we summarize liquid holdup and pressure drop characteristics within packed beds. Furthermore, we analyze the underlying mechanisms involved in bubble breakup and coalescence phenomena occurring during continuous flow of gas–liquid dispersions, providing insights for reactor design and operation strategies. Finally, we summarize applications of packed bed reactors in carbon dioxide absorption, chemical reactions, and wastewater treatment while offering future perspectives. These findings serve as valuable references for optimizing gas–liquid separation processes. Full article

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

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18 pages, 4958 KiB

Open AccessArticle

Roles of Nitrogen- and Sulphur-Containing Groups in Copper Ion Adsorption by a Modified Chitosan Carboxymethyl Starch Polymer

by Zhongbao Hua, Yujie Dong, Liang Chen, Feng Jiang, Honghu Tang and Dongxia Feng

Separations 2024, 11(10), 283; https://doi.org/10.3390/separations11100283 - 1 Oct 2024

Viewed by 381

Abstract

Owing to the toxicity and widespread use of copper, the pollution caused by copper ions has become a long-standing environmental and industrial challenge. In this study, a new adsorbent was developed to dispose of and remove copper ions from water. The modified chitosan–carboxymethyl [...] Read more.

Owing to the toxicity and widespread use of copper, the pollution caused by copper ions has become a long-standing environmental and industrial challenge. In this study, a new adsorbent was developed to dispose of and remove copper ions from water. The modified chitosan–carboxymethyl starch (MCTS-CMS) polymer was characterised, and FTIR and SEM-EDS confirmed the successful graft modification of the receptor. The adsorption behaviour was investigated through various parameters, and the results showed that the optimal parameters were pH > 4.0, an adsorption time of 30 min, a reaction temperature of 293 K, and an initial concentration of 100–120 mg/L. The experimental data exhibited a good fit with pseudo-second-order models, and the Langmuir isotherm revealed that the polymer was found to be highly suitable for adsorption, with a maximum adsorption capacity of 321.16 mg/g. Thermodynamic analysis revealed that the adsorption process was exothermic and spontaneous. XRD and XPS confirmed the generation of posnjakite after the adsorption and the predominant roles of nitrogen- and sulphur-containing groups in the adsorption. Further analysis confirmed the existence of chemisorption and physical adsorption, with chemisorption mainly facilitating the Cu(II) absorption of the polymer. MCTS-CMS showed an excellent removal efficiency of 98% in acidic solutions. On the basis of these findings, the MCTS-CMS polymer demonstrates excellent performance and high selectivity in the removal of copper ions from industrial wastewater or polluted water bodies. This work recommends expanding the polymer’s practical applications to contribute to water purification efforts. Full article

(This article belongs to the Special Issue Separation and Extraction Technology in Mineral Processing)

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28 pages, 1405 KiB

Open AccessReview

Hyphenated Techniques and NMR Methods for Possible Organochlorinated Pesticides Occurrence in Human and Animal Milk

by Eleni D. Thanou and Constantinos G. Tsiafoulis

Separations 2024, 11(10), 282; https://doi.org/10.3390/separations11100282 - 29 Sep 2024

Viewed by 541

Abstract

Although not expected to be used due to restrictions raised on their usage, Persisted Organic Pollutants (POP) such as organochlorinated pesticides (OCPs) can be found in several matrices, even nowadays. The lack of biodegradation and, furthermore, their persistence in the environment result in [...] Read more.

Although not expected to be used due to restrictions raised on their usage, Persisted Organic Pollutants (POP) such as organochlorinated pesticides (OCPs) can be found in several matrices, even nowadays. The lack of biodegradation and, furthermore, their persistence in the environment result in the possible occurrence of these lipophilic toxins in several matrices, from environmental samples and foods to human milk. The current review focuses on the usage of hyphenated techniques for the determination and monitoring of OCPs in several matrices, such as milk—both animal and human milk. The lipid matrix of milk and dairy products favors the possible bioaccumulation of the above pollutants, and the complex matrix of the dairy products is a challenge for method development. Additionally, spectroscopic methods—mainly Nuclear Magnetic Resonance (NMR)-based metabolomics—for biomonitoring of OCPs persistence, bioaccumulation, and effect of possible exposure, along with NMR usage in several methods developed, are also presented and discussed. Finally, we introduce and present the metabolomic approach for OCPs and other POPs in lipid matrices. Full article

(This article belongs to the Special Issue Hyphenated Techniques’ Enlightenment in Chemical Analysis: From Complex Matrices of Plant Extracts and Foods to Human and Human Metabolism)

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11 pages, 1956 KiB

Open AccessArticle

The Removal of Organic Contaminants from Condensed Wastewater Using Electrolysis Combined with Ozonation: A Pilot-Scale Study

by Yalei Ding, Jie Wang and Bin Tan

Separations 2024, 11(10), 281; https://doi.org/10.3390/separations11100281 - 29 Sep 2024

Viewed by 467

Abstract

A pilot-scale investigation of ozonation combined with electrolysis (E-O₃) was performed to treat concentrated wastewater from a reverse osmosis system from the printing and dyeing industry. It was found that E-O₃ only exhibits an efficiency advantage after the removal of [...] Read more.

A pilot-scale investigation of ozonation combined with electrolysis (E-O₃) was performed to treat concentrated wastewater from a reverse osmosis system from the printing and dyeing industry. It was found that E-O₃ only exhibits an efficiency advantage after the removal of carbonate ions. The synergy of ozone and electrolysis lies not only in the generation of hydroxyl radicals, but also in the degradation of organic compounds. Moreover, the combination of electrolysis and ozonation has an inhibitory effect on the decrease in pH, which plays an important role in the synergistic generation of hydroxyl radicals. This pilot-scale study holds reference significance for the engineering applications of the E-O₃ technology. Full article

(This article belongs to the Special Issue Applications of Electrochemistry in Water and Wastewater Treatment)

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13 pages, 2474 KiB

Open AccessArticle

Phytochemical Analysis and In Vitro Effects on Isolated Murine Lymphocytes and Macrophages of Polymeric Micelles Loaded with Cycloartane Saponin

by Aleksandar Shkondrov, Denitsa Stefanova, Ivan Stambolov, Krassimira Yoncheva, Virginia Tzankova and Ilina Krasteva

Separations 2024, 11(10), 280; https://doi.org/10.3390/separations11100280 - 28 Sep 2024

Viewed by 315

Abstract

Triterpenoid saponins from the Astragalus species possess valuable effects (cytotoxic, adjuvant, hepatoprotective, neuroprotective, antiviral, etc.). Some also have immunomodulatory activities. Astragalus glycyphyllos is distributed in Bulgaria and mainly accumulates cycloartane saponins. From the overground parts of the species, a triterpenoid cyloartane-type saponin (AGOS3) [...] Read more.

Triterpenoid saponins from the Astragalus species possess valuable effects (cytotoxic, adjuvant, hepatoprotective, neuroprotective, antiviral, etc.). Some also have immunomodulatory activities. Astragalus glycyphyllos is distributed in Bulgaria and mainly accumulates cycloartane saponins. From the overground parts of the species, a triterpenoid cyloartane-type saponin (AGOS3) was isolated by different chromatographic techniques. A quantitative LC-MS method for the determination of the saponin was developed and validated. Further, the saponin was loaded in copolymeric micelles based on triblock copolymers of polyethylene oxide and polypropylene oxide (Pluronics). The LC-MS method was applied on the developed micelles to determine their loading degrees. Afterwards, the possible pharmacological effects of free and encapsulated in polymeric nanoparticles of triterpenoid saponin (1, 5, 10, 25, 50, and 100 µg/mL) were evaluated in isolated murine macrophages and lymphocytes in vitro. Free AGOS3 stimulated proliferation only at the highest tested concentrations (50–100 µg/mL), and the effect was more evident in isolated macrophages. Interestingly, AGOS3-loaded polymeric micelles caused concentration dependency and statistically significant increases in the proliferation of both isolated lymphocytes and macrophages, even at a lower concentration (10 µg/mL). These results could serve as the basis for further research on the immunomodulatory effect of this saponin. Full article

(This article belongs to the Special Issue Isolation of Natural Compounds—Emphasis on Antioxidants' Purification)

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17 pages, 4999 KiB

Open AccessArticle

Development and Validation of a Novel Method Using QuEChERS and UHPLC-MS-MS for the Determination of Multiple Emerging Fungicides in Surface Waters

by Pulasthi Serasinghe, Deni Taleski, Hao T. K. Nguyen, Dayanthi Nugegoda and Vincent Pettigrove

Separations 2024, 11(10), 279; https://doi.org/10.3390/separations11100279 - 24 Sep 2024

Viewed by 566

Abstract

The increasing global reliance on pesticides for agricultural pest control has raised significant environmental concerns, particularly due to inadequate monitoring of emerging chemicals in surface waters. This study addresses the potential contamination of aquatic ecosystems by developing and validating a method for detecting [...] Read more.

The increasing global reliance on pesticides for agricultural pest control has raised significant environmental concerns, particularly due to inadequate monitoring of emerging chemicals in surface waters. This study addresses the potential contamination of aquatic ecosystems by developing and validating a method for detecting trace amounts of four recently registered fungicides: three succinate dehydrogenase inhibitors (fluopyram, penthiopyrad, pydiflumetofen) and fluopicolide, a structurally related fungicide. Employing QuEChERS-based sample extraction combined with ultra-high-performance liquid chromatography (UHPLC-MS-MS), this method achieves detection limits of 0.1 to 0.2 μg/L, with recovery rates between 90% and 110%, and intra-day relative standard deviation values well within the acceptable range of less than 20%. Applied to surface grab water samples from the greater Melbourne area, Australia, the method successfully identified all four fungicides at trace levels, including a notable high concentration of fluopyram (7.3 μg/L) during autumn, with the others intermittently detected at lower concentrations. This study represents the first documented instance of quantifiable detections of these four fungicides in Australian surface water systems. Given their high toxicity to several organisms and the limited global data on these substances, our findings underscore the critical need for continuous monitoring to inform strategies to safeguard aquatic ecosystems from these chemicals. Full article

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

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Separations, Volume 11, Issue 10 (October 2024) – 23 articles

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