Separations

17 pages, 5169 KiB

Open AccessArticle

Research on the Flotation Mechanism of Microemulsion Collector Enhanced Removal of Dyeing Impurities from Phosphogypsum

by Xiaosheng Yu, Lijun Deng, Changpan Shen, Huiyong Li, Jingchao Li, Yijun Cao, Guoli Zhou and Guosheng Li

Separations 2025, 12(1), 7; https://doi.org/10.3390/separations12010007 - 31 Dec 2024

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Abstract

Phosphogypsum is an industrial byproduct that is limited in its high-value application due to the presence of dyeing impurities (such as organic matter and carbon black). The flotation method has been verified to be effective in separating these dyeing impurities from gypsum. In [...] Read more.

Phosphogypsum is an industrial byproduct that is limited in its high-value application due to the presence of dyeing impurities (such as organic matter and carbon black). The flotation method has been verified to be effective in separating these dyeing impurities from gypsum. In this study, microemulsion was used as the collector method of dyeing impurities for their separation from gypsum. The results of flotation tests showed that the microemulsion collector exhibited excellent collection capability and selectivity under natural pH conditions (pH = 1.5). With a microemulsion collector consumption of 400 g/t, purified gypsum of 65.1% whiteness, 95.74% yield, and 97.01% recovery was obtained. The purified gypsum of 65.1% whiteness, 95.74% yield, 97.01 recovery obtained by a used microemulsion collector amount of 400 g/t was better than using the same dosage of kerosene collector. The dispersion behavior of the microemulsion collector was studied by low-temperature transmission electron microscopy. The microemulsion collector demonstrated superior dispersibility, as it forms nano-oil droplets with an average size of 176.83 nm in the pulp, resolving issues associated with poor dispersibility observed in traditional kerosene collectors. Additionally, the nano-oil droplets effectively adsorbed onto the surface of dyeing impurities through hydrogen bonding, enhancing their hydrophobicity. Therefore, the microemulsion collector holds great potential for application in flotation whitening processes involving phosphogypsum. Full article

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

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15 pages, 2061 KiB

Open AccessArticle

Kinetics of Supercritical CO₂ Extraction from Burrito (Aloysia polystachya) Leaves and Sucupira-Preta (Bowdichia virgilioides) Seeds

by Gabrielle Vaz Vieira, Michel Rubens dos Reis Souza, Carlos Toshiyuki Hiranobe, José Eduardo Goncalves, Cristiane Mengue Feniman Moritz, Otávio Akira Sakai, Leila Maria Sotocorno e Silva, Michael Jones da Silva, Erivaldo Antônio da Silva, Renivaldo José dos Santos, Edson Antônio da Silva, Lucio Cardozo-Filho and Leandro Ferreira-Pinto

Separations 2025, 12(1), 6; https://doi.org/10.3390/separations12010006 - 31 Dec 2024

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Abstract

This study investigated the application of supercritical carbon dioxide (CO₂) for the extraction of essential oils from plant materials with anxiolytic potential, focusing on the leaves of burrito (Aloysia polystachya) and the seeds of sucupira-preta (Bowdichia virgilioides). [...] Read more.

This study investigated the application of supercritical carbon dioxide (CO₂) for the extraction of essential oils from plant materials with anxiolytic potential, focusing on the leaves of burrito (Aloysia polystachya) and the seeds of sucupira-preta (Bowdichia virgilioides). The supercritical extraction technique was chosen for its ability to produce high-purity extracts without residual solvents and to reduce the environmental impact. This study evaluated the influence of temperature (40 °C, 50 °C, and 60 °C) and pressure (22 MPa, 25 MPa, and 28 MPa) on extraction efficiency using a 2² factorial design with triplicates at the central point. The maximum yields were 1.2% for burrito leaves and 4.2% for sucupira-preta seeds. Despite their relatively low yields, the extracts contained a diverse range of chemical compounds, including fatty acids (oleic, linoleic, and palmitic acids), squalene, β-carotene, vitamin E, and other bioactive molecules with antioxidant, anti-inflammatory, and immunomodulatory properties. Statistical analysis demonstrated that pressure was the most influential factor affecting yield, whereas temperature played a secondary role. The Sovová kinetic model provided a good fit for the extraction curves, with determination coefficients (R²) above 0.95, thus validating the efficiency of the method. These results highlight the pharmaceutical potential of these extracts, particularly for therapeutic and anxiolytic purposes. Full article

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17 pages, 5353 KiB

Open AccessArticle

A Compact Instrument for Temperature-Programming-Assisted Capillary–Nanoliquid Chromatography

by Lincon Coutinho Marins, Alessandra Maffei Monteiro, Vivane Lopes Leal, Deyber Arley Vargas Medina, Edwin Martin Cardenas and Fernando Mauro Lanças

Separations 2025, 12(1), 5; https://doi.org/10.3390/separations12010005 - 30 Dec 2024

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Abstract

The miniaturization of liquid chromatography (LC) columns to capillary and nanoscales allows temperature programming to be an effective alternative to solvent gradients for modulating eluotropic strength. This approach simplifies instrument design and operation, as a single pump can suffice to achieve efficient separations. [...] Read more.

The miniaturization of liquid chromatography (LC) columns to capillary and nanoscales allows temperature programming to be an effective alternative to solvent gradients for modulating eluotropic strength. This approach simplifies instrument design and operation, as a single pump can suffice to achieve efficient separations. This study presents the development and application of a compact, lab-built high-pressure system for temperature-programmed capillary and nanoLC separations. The instrument includes a high-pressure capillary–nanoflow syringe pump, a time-based nanoliter injection system, a programmable capillary column oven for controlled temperature gradients, and a UV-Vis detection system with a custom nanoliter-scale detection cell. Each system component was designed and built in-house, with rigorous calibration to ensure accuracy and operational reliability. Experimental data confirm the system’s capability to deliver precise, reproducible temperature, and flow rates. Functionality was validated through temperature-programmed separations on packed and open tubular capillary columns. The results demonstrated that the developed instrument offers enhanced separation efficiency and reduced analysis time compared to isothermal methods, underscoring its potential for advanced applications in miniaturized liquid chromatography. Full article

(This article belongs to the Special Issue Separation Techniques on a Miniaturized Scale)

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22 pages, 2361 KiB

Open AccessReview

Advances in Recycling Technologies of Critical Metals and Resources from Cathodes and Anodes in Spent Lithium-Ion Batteries

by Shuwen Wang, Yanrong Lai, Jingran Yang, Jiaxue Zhao, Yushan Zhang, Miaoling Chen, Jinfeng Tang, Junhua Xu and Minhua Su

Separations 2025, 12(1), 4; https://doi.org/10.3390/separations12010004 - 30 Dec 2024

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Abstract

With the rapid economic development and the continuous growth in the demand for new energy vehicles and energy storage systems, a significant number of waste lithium-ion batteries are expected to enter the market in the future. Effectively managing the processing and recycling of [...] Read more.

With the rapid economic development and the continuous growth in the demand for new energy vehicles and energy storage systems, a significant number of waste lithium-ion batteries are expected to enter the market in the future. Effectively managing the processing and recycling of these batteries to minimize environmental pollution is a major challenge currently facing the lithium-ion battery industry. This paper analyzes and compares the recycling strategies for different components of lithium-ion batteries, providing a summary of the main types of batteries, existing technologies at various pre-treatment stages, and recycling techniques for valuable resources such as heavy metals and graphite. Currently, pyrometallurgy and hydrometallurgy processes have matured; however, their high energy consumption and pollution levels conflict with the principles of the current green economy. As a result, innovative technologies have emerged, aiming to reduce energy consumption while achieving high recovery rates and minimizing the environmental impact. Nevertheless, most of these technologies are currently limited to the laboratory scale and are not yet suitable for large-scale application. Full article

(This article belongs to the Section Purification Technology)

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12 pages, 1644 KiB

Open AccessArticle

CO₂/CH₄ and CO₂/CO Selective Pebax-1657 Based Composite Hollow Fiber Membranes Prepared by a Novel Dip-Coating Technique

by Dionysios S. Karousos, George V. Theodorakopoulos, Francesco Chiesa, Stéphan Barbe, Mirtat Bouroushian and Evangelos P. Favvas

Separations 2025, 12(1), 3; https://doi.org/10.3390/separations12010003 - 29 Dec 2024

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Abstract

A novel and innovative method was developed to fabricate defect-free composite hollow fiber (HF) membranes using drop-casting under continuous flow. The synthesized Pebax-1657—based membranes were examined for gas separation processes, focusing on the separation of CO₂ from CH₄ and CO gases. [...] Read more.

A novel and innovative method was developed to fabricate defect-free composite hollow fiber (HF) membranes using drop-casting under continuous flow. The synthesized Pebax-1657—based membranes were examined for gas separation processes, focusing on the separation of CO₂ from CH₄ and CO gases. The separation performance of the membranes was rigorously assessed under realistic binary gas mixture conditions to evaluate their selectivity and performance. The effect of pressure on separation performance was systematically investigated, with transmembrane pressures up to 10 bar being applied at a temperature of 298 K. Remarkable CO₂/CH₄ selectivities of up to 110 and CO₂/CO selectivities of up to 48 were achieved, demonstrating the robustness and effectiveness of these composite HF membranes, suggesting their suitability for high-performance gas separation processes under varying operational conditions. Overall, this study introduces a novel approach for scaling up the fabrication of HF membranes and provides valuable insights into their application in CO₂ separation technologies, offering the potential for advancements in areas such as natural gas processing and carbon capture from CO-containing streams. Full article

(This article belongs to the Special Issue 10th Anniversary Special Issues: Membrane Separation Processes)

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21 pages, 5817 KiB

Open AccessArticle

Application of Magnetic Aquatic Plant Biochar for Efficient Removal of Antimony from Water: Adsorption Properties and Mechanism

by Luyi Nan, Yuting Zhang, Min Liu, Liangyuan Zhao, Yuxuan Zhu and Xun Zhang

Separations 2025, 12(1), 2; https://doi.org/10.3390/separations12010002 - 28 Dec 2024

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Abstract

Antimony (Sb) pollution in natural water bodies can cause significant harm to aquatic ecosystems. Currently, the utilization of chemicals in water bodies presents disadvantages, such as the hardship in collecting dispersed flocs and the incomplete elimination of pollutants. In the present research, a [...] Read more.

Antimony (Sb) pollution in natural water bodies can cause significant harm to aquatic ecosystems. Currently, the utilization of chemicals in water bodies presents disadvantages, such as the hardship in collecting dispersed flocs and the incomplete elimination of pollutants. In the present research, a novel type of efficient adsorbent material for the magnetic recovery of Sb was proposed: the magnetic aquatic plant biochar. Its adsorption characteristics and mechanism were deeply investigated. The results demonstrated that, among the three types of aquatic plants, the magnetic biochar of Arundo donax magnetic biochar (LMBC) displayed the most superior adsorption effect on Sb. Under optimal adsorption conditions (pyrolysis temperature of 300 °C, dosage of 100 mg, pH of 8), the removal rate of Sb by LMBC exceeded 97%. The adsorption rate of Sb by LMBC was relatively rapid, and the kinetics of adsorption conformed to a pseudo-second-order kinetic model. The adsorption isotherm was consistent with the Langmuir and Freundlich models, and the maximum adsorption capacity of Sb reached 26.07 mg/g, suggesting that the adsorption process pertained to the adsorption of multi-molecular layers. The influence of coexisting ions on the adsorption effect of LMBC was insignificant. The SEM characterization results revealed that LMBC mainly consisted of the elements C and O. The BET characterization results demonstrated that the magnetization modification augmented the specific surface area by approximately 30 times to reach 89.14 m²/g, and the pore volume increased by twofold to 0.18 cm³/g, creating a favorable condition for Sb adsorption. The FTIR, XRD, and XPS results indicated that the surface of LMBC was rich in carboxyl and hydroxyl groups and was successfully loaded with Fe₂O₃ and Fe₃O₄. LMBC not only facilitates the resourceful utilization of aquatic plant waste but also effectively removes antimony (Sb) pollution through its magnetic properties. This dual functionality presents promising application prospects for the efficient adsorption and removal of Sb from water. Full article

(This article belongs to the Special Issue Adsorption of Emerging Water Pollutants by Advanced Materials)

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18 pages, 8445 KiB

Open AccessArticle

Irradiated Gao Miao Zi Bentonite for Uranium Retention: Performance and Mechanism

by Yushan Zhang, Gang Song, Yujie Mo, Shuwen Wang, Diyun Chen and Minhua Su

Separations 2025, 12(1), 1; https://doi.org/10.3390/separations12010001 - 26 Dec 2024

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Abstract

Bentonite has been considered as backfill material in the long-term deep geological disposal sites for radioactive waste. The performance of raw and irradiated bentonite based on the retention of radioactive nuclides, such as U(VI), is a critical factor for its application. Herein, the [...] Read more.

Bentonite has been considered as backfill material in the long-term deep geological disposal sites for radioactive waste. The performance of raw and irradiated bentonite based on the retention of radioactive nuclides, such as U(VI), is a critical factor for its application. Herein, the intrinsic features and adsorption behavior of Gao Miao Zi (GMZ) bentonite based on uranyl ions was investigated. In aqueous solutions, bentonite can achieve an adsorption rate of up to 100% for U(VI). The primary mechanism of U(VI) adsorption by GMZ bentonite is ion exchange, supplemented by surface complexation. Strong irradiation can introduce slight structural changes and framework fractures in bentonite, reducing its adsorption capacity for U(VI). This study provides an in-depth analysis of the adverse effects of high doses of radiation (100 kGy) on the microstructure and adsorption properties of bentonite, offering important insights for the safe storage of radioactive waste. Full article

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

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Separations, Volume 12, Issue 1 (January 2025) – 7 articles

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