Separations

50 pages, 6479 KiB

Open AccessArticle

Sustainable and Efficient Wastewater Treatment Using Cellulose-Based Hydrogels: A Review of Heavy Metal, Dye, and Micropollutant Removal Applications

by Ziao Zhang, Yujie Lu, Shoujian Gao and Shuping Wu

Separations 2025, 12(3), 72; https://doi.org/10.3390/separations12030072 - 18 Mar 2025

Cited by 1 | Viewed by 1142

Abstract

The rapid pace of global industrialization and population growth has intensified freshwater scarcity and water pollution, necessitating urgent solutions. Adsorption technology, favored for its cost-effectiveness, simplicity, and scalability, has emerged as a promising approach. Hydrogels, particularly cellulose-based hydrogels (CBHs), have gained significant attention [...] Read more.

The rapid pace of global industrialization and population growth has intensified freshwater scarcity and water pollution, necessitating urgent solutions. Adsorption technology, favored for its cost-effectiveness, simplicity, and scalability, has emerged as a promising approach. Hydrogels, particularly cellulose-based hydrogels (CBHs), have gained significant attention as green adsorbents due to their biodegradability, non-toxicity, low cost, and exceptional adsorption capacity. This paper reviews recent advancements in CBHs for sustainable wastewater treatment, focusing on synthesis techniques, performance, and mechanisms for removing heavy metals, dyes, and micropollutants. Updated applications and their outcomes are also discussed. Despite their advantages, CBHs face challenges such as limited mechanical strength, practical production difficulties, insufficient reuse studies, and separation inefficiencies. This review addresses these issues and explores future prospects for their practical implementation. The findings provide valuable insights into advancing CBHs in sustainable and efficient water treatment solutions. Full article

(This article belongs to the Special Issue Design and Preparation of Sustainable Separation Membrane for Efficient Water Purification)

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Graphical abstract

68 pages, 9886 KiB

Open AccessReview

Polyethylene Glycol (PEG) Additive in Polymer Membranes for Carbon Dioxide Separation: A Critical Review on Performances and Correlation with Membrane Structure

by Riccardo Checchetto

Separations 2025, 12(3), 71; https://doi.org/10.3390/separations12030071 - 16 Mar 2025

Viewed by 549

Abstract

The efficient separation and removal of carbon dioxide (

{C O}_{2}

) from its mixtures is an important technological challenge to limit effects resulting from the increase of the carbon dioxide concentration in the atmosphere. Membrane technology is an environmentally friendly approach, [...] Read more.

The efficient separation and removal of carbon dioxide (

{C O}_{2}

) from its mixtures is an important technological challenge to limit effects resulting from the increase of the carbon dioxide concentration in the atmosphere. Membrane technology is an environmentally friendly approach, highly scalable and less energy-consuming than conventional methods such as adsorption, absorption and cryogenic separation. Hybrid membrane materials incorporating inorganic filler nanostructures in polymer matrices having polyethylene glycol (PEG) as a plasticized additive are promising membrane materials given the presence of

{C O}_{2}

-philic polar functional groups of PEGs and the structural refinements on the blend matrix consequent to the filler distribution. In this review, literature information on hybrid polymer/PEG membranes are critically reviewed to discuss how filler dispersion in the blend matrix gives rise to enhanced

{C O}_{2}

separation performances with respect to those obtained with traditional mixed matrix membranes where filler nanostructures are dispersed in the neat polymer. The discussion will be focused on the correlation between the

{C O}_{2}

transport properties, membrane structural properties and defect resulting from the polymer-filler incompatibility. It is shown that hybrid polymer/PEG membranes with dispersed filler nanostructures simultaneously offer improved

{C O}_{2}

separation performances and enhanced mechanical properties compared with nanocomposite ones where filler particles are dispersed in the neat polymer matrix. PEG addition enhances the filler-matrix compatibility, delays filler aggregation and limits the formation of filler-matrix interface defects. Full article

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

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17 pages, 313 KiB

Open AccessReview

Competitive Adsorption of Metal Ions by Lignocellulosic Materials: A Review of Applications, Mechanisms and Influencing Factors

by Morgana Macena, Helena Pereira, Luísa Cruz-Lopes, Lucas Grosche and Bruno Esteves

Separations 2025, 12(3), 70; https://doi.org/10.3390/separations12030070 - 16 Mar 2025

Cited by 1 | Viewed by 559

Abstract

The rapid expansion of industrial and agricultural activities in recent years has significantly contributed to water pollution leading to a decline in water quality and the need for effective treatment and reuse strategies. Metal contamination in water bodies poses severe environmental and health [...] Read more.

The rapid expansion of industrial and agricultural activities in recent years has significantly contributed to water pollution leading to a decline in water quality and the need for effective treatment and reuse strategies. Metal contamination in water bodies poses severe environmental and health risks, making the development of cost-effective and sustainable remediation methods essential. Among the various treatment approaches, biosorption using biological adsorbents has emerged as a promising alternative due to its low cost and high efficiency. However, while the adsorption mechanisms of single metals are well understood, the competitive interactions between multiple metal ions during the sorption process remain less explored. In this review, we analyze the competitive biosorption of metals in multi-metallic wastewater systems. Key factors influencing metal removal, such as pH, contact time, biosorbent dosage, and initial metal concentration, are discussed, along with the intrinsic properties of biosorbents and metal ions that affect sorption efficiency. Additionally, we highlight recent studies on agroforestry byproducts as effective biosorbents for metal removal, showcasing their potential for sustainable water treatment. Heavy metals pose significant risks even at low concentrations, necessitating robust regulations and advanced treatment technologies; biomass byproducts, as cost-effective biosorbents, can be optimized through pre-treatment, activation, pH and temperature control, and particle size reduction, while effectively managing competitive multi-metal adsorption remains crucial for industrial effluent treatment. Full article

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

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19 pages, 15230 KiB

Open AccessArticle

Exploration of the Synergistic Smelting Behavior of Electroplating Sludge and Lead–Zinc Ore

by Meiling Wu, Chi Wang, Cong Peng, Kai Li and Lei Shi

Separations 2025, 12(3), 69; https://doi.org/10.3390/separations12030069 - 14 Mar 2025

Viewed by 352

Abstract

With the rapid development of China’s zinc-related industries, the grade of zinc concentrate has steadily declined, while the generation of zinc-containing solid waste has shown a significant upward trend. To address this issue, a collaborative smelting process for lead–zinc ores and zinc-containing solid [...] Read more.

With the rapid development of China’s zinc-related industries, the grade of zinc concentrate has steadily declined, while the generation of zinc-containing solid waste has shown a significant upward trend. To address this issue, a collaborative smelting process for lead–zinc ores and zinc-containing solid waste has been proposed, aiming to effectively recycle zinc-based solid waste during the processing of lead–zinc ores. This study examined the effects of adding different proportions of electroplating sludge (3%, 6%, 9%, and 12%) to lead–zinc ores on the smelting performance of primary ores. The results indicated that when the addition reached 6% or higher, certain complex compounds were effectively decomposed, while the volatilization rate remained comparable to that of the primary ore. Moreover, increasing the proportion of electroplating sludge not only immobilized part of the lead, reducing its volatilization, but also significantly lowered the melting point of the mixture. The lowest melting point (1199 °C) was observed with a 9% addition; although it slightly increased at 12%, it remained below the melting point of the primary ore. Based on these findings, an optimal addition of approximately 6% electroplating sludge is recommended to maximize the efficiency and benefits of the collaborative smelting process. Full article

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12 pages, 1534 KiB

Open AccessArticle

Assessment of Bioactive Compounds and Antioxidant Activity of Barley Sprouts

by Geon Oh, Im-Joung La, Do-Sang Lee, Jong-Woo Chae, Ji-Hyun Im, Seon Woo Park, Xiaolu Fu, June-Seok Lim, Min-Hye Kim, Yeon-Seok Seong, DoSu Park and Ok-Hwan Lee

Separations 2025, 12(3), 68; https://doi.org/10.3390/separations12030068 - 13 Mar 2025

Viewed by 518

Abstract

Barley sprouts, rich in bioactive compounds, have gained attention as functional food ingredients because of their antioxidant potential. This study evaluated their bioactive composition and antioxidant capacity, focusing on the saponarin, chlorophyll, policosanol, total polyphenol (TP), and total flavonoid (TF) contents. The antioxidant [...] Read more.

Barley sprouts, rich in bioactive compounds, have gained attention as functional food ingredients because of their antioxidant potential. This study evaluated their bioactive composition and antioxidant capacity, focusing on the saponarin, chlorophyll, policosanol, total polyphenol (TP), and total flavonoid (TF) contents. The antioxidant capacity was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric-reducing antioxidant power (FRAP) assays. The results showed that barley sprouts contained 8.14 ± 0.02 mg/g of saponarin, 15.36 ± 0.18 mg/g of total chlorophyll, 396.99 mg/100 g of policosanols, 12.64 ± 0.04 mg of gallic acid equivalent (GAE)/g, and 5.99 ± 0.09 mg of rutin equivalent (RE)/g. The half-maximal inhibitory concentration (IC₅₀) values exhibited the trend FRAP > DPPH > ABTS. Significant correlations (R > 0.891, p < 0.05) were observed between the antioxidant assays and TP and TF contents, indicating their substantial role in the antioxidant properties of barley sprout extracts. These findings suggest that barley sprouts are a valuable natural source of antioxidants for functional food applications. Nevertheless, additional in vivo and clinical research is necessary to improve their bioavailability and expand their potential use in food formulations. Full article

(This article belongs to the Special Issue Extraction and Isolation of Nutraceuticals from Plant Foods)

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8 pages, 1590 KiB

Open AccessArticle

Separation of D-Amino Acid-Containing Tripeptide L-Asn-D-Trp-L-Phe-NH₂ and Its Diastereomer Using Crown–Ether-Type Chiral Stationary Phase

by Batsaikhan Mijiddorj, Yohei Kayano, Hiroki Yamagishi, Haruto Nakajima and Izuru Kawamura

Separations 2025, 12(3), 67; https://doi.org/10.3390/separations12030067 - 10 Mar 2025

Viewed by 484

Abstract

Several D-amino acid residue-containing peptides (DAACPs) with antimicrobial, cardio-excitatory, and neuronal activities have been identified in various species. The L-Asn-D-Trp-L-Phe-NH₂ (N(dW)F) tripeptide, derived from Aplysia kurodai, exhibits cardiac activity in invertebrates. The chirality of the tryptophan residue at the second position [...] Read more.

Several D-amino acid residue-containing peptides (DAACPs) with antimicrobial, cardio-excitatory, and neuronal activities have been identified in various species. The L-Asn-D-Trp-L-Phe-NH₂ (N(dW)F) tripeptide, derived from Aplysia kurodai, exhibits cardiac activity in invertebrates. The chirality of the tryptophan residue at the second position in N(dW)F influences its conformation and biological characteristics. We demonstrated the chiral separation of N(dW)F and its diastereomer NWF using (S)-3,3′-diphenyl-1,1′-binaphthyl-20-crown-6-ether columns (CR-I(+)). A reduction in the ratio of acetonitrile and methanol in the mobile phase allowed the complete separation of N(dW)F and its diastereomer, improving the separation factor (α) from 0.96 to 6.28. Molecular dynamics simulations revealed that the interaction of N(dW)F with CR-I(−) was more favorable than with CR-I(+). These findings indicate that the structure of the CR-I column stereoselectively recognizes peptides and facilitates the separation of naturally occurring D-amino acid residue-containing tripeptides. Full article

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

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14 pages, 2047 KiB

Open AccessArticle

Difference in Biological Oxidation Between High-Sulfur Coal and Pure Pyrite at Different pH Levels

by Dongxu Yuan, Yiyang Wei, Xinyu Fan and Fenwu Liu

Separations 2025, 12(3), 66; https://doi.org/10.3390/separations12030066 - 10 Mar 2025

Viewed by 347

Abstract

In this study, Acidthiobacillus ferrooxidans LX5 was used as an experimental microbial strain, and differences in biological oxidation between high-sulfur coal and pure pyrite were thoroughly investigated over 18 days in acidic environments with initial pH values of 1.70, 2.00, 2.30, and 2.60. [...] Read more.

In this study, Acidthiobacillus ferrooxidans LX5 was used as an experimental microbial strain, and differences in biological oxidation between high-sulfur coal and pure pyrite were thoroughly investigated over 18 days in acidic environments with initial pH values of 1.70, 2.00, 2.30, and 2.60. The results showed that the pyrite bio-oxidation efficiency in the coal biological desulfurization system exceeded that in the pure pyrite bio-oxidation system at the same initial pH. The net increase in SO₄²⁻ concentration in the coal biological desulfurization system increased with increasing initial pH values, consistent with the net increasing trend in SO₄²⁻ in the pure pyrite biological oxidation system. The net increase in SO₄²⁻ concentration in the high-sulfur coal biological oxidation system with an initial pH of 2.60 reached 4589.06 mg/L after 18 days. The density of A. ferrooxidans LX5 in both systems increased with increasing initial pH values. With increasing initial pH levels, the inorganic sulfur (pyritic sulfur and sulfate sulfur) removal efficiencies increased in both the coal biological desulfurization and pyrite biological oxidation systems, reaching 88.28% and 9.25%, respectively, at an initial pH of 2.60. The results are of great significance for better understanding the biological desulfurization process of coal. Full article

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

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40 pages, 6428 KiB

Open AccessReview

Greener Pectin Extraction Techniques: Applications and Challenges

by Shaikh Manirul Haque, Abuzar Kabir, Elaref Ratemi, Mohamed Elzagheid, Sreekumar Parambathmadhom Appu, Syed Sauban Ghani and Abdullah Sarief

Separations 2025, 12(3), 65; https://doi.org/10.3390/separations12030065 - 9 Mar 2025

Viewed by 1878

Abstract

Pectin is a complex and versatile polysaccharide crucial for various industries. It functions as a thickener, gelling agent, emulsifier, and low-calorie food. Its anti-inflammatory and immunomodulatory properties have attracted biomedical interest, while its biodegradability and biocompatibility make it valuable for biomaterial applications. The [...] Read more.

Pectin is a complex and versatile polysaccharide crucial for various industries. It functions as a thickener, gelling agent, emulsifier, and low-calorie food. Its anti-inflammatory and immunomodulatory properties have attracted biomedical interest, while its biodegradability and biocompatibility make it valuable for biomaterial applications. The effectiveness of these applications depends on the quality of pectin extraction procedures. While traditional extraction methods exist, green methodologies and alternative techniques have improved pectin’s physicochemical properties—a significant advantage for industrial applications. Pectin can be extracted from various sources, with its molecular structure and functional groups analyzed through different characterization techniques. Modern green extraction methods include ultrasound-assisted extraction, pulsed ultrasound-assisted extraction, pulsed electric field, moderate electric field mediated extraction, microwave-assisted extraction, subcritical water extraction, enzyme-assisted extraction, ohmic heating-assisted extraction, ultrasound-assisted microwave extraction, ultrasound-assisted ohmic heating extraction, hydrothermal processing, high-pressure processing extraction, and dielectric barrier discharge extraction. This review examines these methods’ advantages and disadvantages, along with their applications and future possibilities; it serves as a comprehensive guide for researchers exploring new pectin-rich sources and green extraction technologies for commercial applications. Full article

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12 pages, 1419 KiB

Open AccessReview

A Brief Overview of Nanomaterials in Inorganic Selenium Speciation

by Krystyna Pyrzynska

Separations 2025, 12(3), 64; https://doi.org/10.3390/separations12030064 - 9 Mar 2025

Viewed by 419

Abstract

Although total selenium content is still useful in many areas, knowledge of its speciation is gaining importance as its various chemical forms have different environmental effects, toxicities and biological utilization. Among several methods used for the isolation and enrichment of selenium species, solid-phase [...] Read more.

Although total selenium content is still useful in many areas, knowledge of its speciation is gaining importance as its various chemical forms have different environmental effects, toxicities and biological utilization. Among several methods used for the isolation and enrichment of selenium species, solid-phase extraction and its alternative approaches are often applied due to their simplicity and high efficiency. This brief overview summarizes the progress made in using different nanostructure sorbents to separate and preconcentrate inorganic selenium species in environmental waters. Nanomaterials are finding increasing applications as they have a large specific surface area and high chemical stability. Functionalizing their surface by covalent or noncovalent interactions with other components, grafting or doping with heteroatoms can improve the separation and removal efficiency. Strategies based on combining selective chemical reactions and separation procedures are discussed. Full article

(This article belongs to the Special Issue Environmental Functional Nanomaterials in Heavy Metal Removal and Pollutant Degradation)

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11 pages, 1602 KiB

Open AccessArticle

Green Protein Extraction from Hazelnut Press Cake: Yield, Efficiency, and Secondary Structure Analysis

by Bruna Anzà, Silvia Fraterrigo Garofalo, Alessandro Lapolla and Debora Fino

Separations 2025, 12(3), 63; https://doi.org/10.3390/separations12030063 - 9 Mar 2025

Viewed by 638

Abstract

Hazelnut (Corylus avellana L.) oil production generates press cakes, a by-product rich in plant-based proteins. As demand for alternative proteins grows, sustainable extraction methods like deep eutectic solvents (DESs) are essential for reducing the environmental impact. Alkali solubilization/isoelectric precipitation (ALKIS) is a [...] Read more.

Hazelnut (Corylus avellana L.) oil production generates press cakes, a by-product rich in plant-based proteins. As demand for alternative proteins grows, sustainable extraction methods like deep eutectic solvents (DESs) are essential for reducing the environmental impact. Alkali solubilization/isoelectric precipitation (ALKIS) is a widely used method for protein extraction due to its simplicity and cost-effectiveness. Despite that, ALKIS extraction has limitations due to the alteration in protein functionality, a reduction in protein stability, and significant wastewater production. This study compares DESs with ALKIS for extracting proteins from hazelnut press cake. ALKIS resulted in higher protein content (42.53 ± 17.45% vs. 8.55 ± 1.68%), while DES extraction showed higher efficiency (56.41 ± 2.4% vs. 45.16 ± 5.32%). FTIR analysis revealed significant structural differences: DES-extracted proteins exhibited higher β-sheet content (α-helix peak: 31.55 ± 6.97% vs. 18.13 ± 1.15%, p = 0.0302), indicating enhanced stability, whereas ALKIS-extracted proteins had more random coil structures (β-sheet peak: 57.92 ± 3.12% vs. 34.07 ± 12.45%, p = 0.0324), suggesting partial denaturation. The preservation of native protein structures in DES extraction is likely due to hydrogen bonding networks that stabilize proteins during processing. Full article

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

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16 pages, 10973 KiB

Open AccessArticle

Enrichment of Trace Selenium in Water Based on Metal−Organic Framework Materials and Reversed−Phase Ultra−High−Performance Liquid Chromatography−Diode Array Determination

by Hanqing Cai, Hongmei Guo, Hanlu Jing, Pingping Wen, Qiuying Wu, Yang Li, Zhirong Suo and Jian Zhang

Separations 2025, 12(3), 62; https://doi.org/10.3390/separations12030062 - 9 Mar 2025

Viewed by 468

Abstract

A method for the determination of trace selenium in water enriched by metal–organic−framework material (MIL−125−NH₂) and reversed−phase ultra−high−performance liquid chromatography−diode array detection (UPLC−DAD) was established. The MIL−125−NH₂ material, synthesized by the microwave method, was characterized by SEM, XRD, and FT−IR. [...] Read more.

A method for the determination of trace selenium in water enriched by metal–organic−framework material (MIL−125−NH₂) and reversed−phase ultra−high−performance liquid chromatography−diode array detection (UPLC−DAD) was established. The MIL−125−NH₂ material, synthesized by the microwave method, was characterized by SEM, XRD, and FT−IR. The MIL−125−NH₂ material was added to the water sample to enrich the selenium, the enriched selenium was desorbed with dilute HCl, and then the derivative reaction with 0.1 mol·L⁻¹ 4−nitro−o−phenylenediamine was performed to produce piaselenole. After extraction with cyclohexane, the retention time and the spectrogram were qualitatively detected by a liquid chromatography−diode array detector, and the peak area was quantitatively detected. The pH, time, amount of material, extractant, and other conditions of derivation and enrichment were optimized in the experiment, and the methodology was verified under optimized conditions. The results showed that the linear correlation coefficient R² was 0.9998, the detection limit of 0.13 μg·L⁻¹ without enrichment was close to that of the ICP−MS method, the detection limit after 10−fold enrichment was 0.013 μg·L⁻¹, the RSD was 0.7~2.7%, and the recovery was 87.8~102.1%, in the range of 2~1000 μg·L⁻¹. Therefore, the method can be applied for the determination of trace selenium in tap water, river water, mountain spring water, packaged drinking water, and industrial sewage. Full article

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13 pages, 3079 KiB

Open AccessArticle

The Bio-Desulfurization of Cassiterite–Polymetallic Sulfide Ores Enhanced by a Consortium of Moderately Thermophilic Bacteria

by Mingwei Wang, Weimin Zeng, Zhen Yan, Li Shen, Runlan Yu, Xueling Wu, Jiaokun Li, Guanzhou Qiu, Wolfgang Streit and Yuandong Liu

Separations 2025, 12(3), 61; https://doi.org/10.3390/separations12030061 - 6 Mar 2025

Viewed by 417

Abstract

Sulfides should be removed before the recovery of cassiterite from tin-rich minerals due to their similarity in flotation properties. However, the traditional methods used have low selectivity. Therefore, moderately thermophilic microorganisms were used to desulfurize tin ore in this study, and the success [...] Read more.

Sulfides should be removed before the recovery of cassiterite from tin-rich minerals due to their similarity in flotation properties. However, the traditional methods used have low selectivity. Therefore, moderately thermophilic microorganisms were used to desulfurize tin ore in this study, and the success of the microbial community was investigated. The bio-desulfurization rate reached 90% on the 10th day using the mixed culture of Leptospirillum ferriphilum (L. ferriphilum), Sulfobacillus thermosulfidooxidans (S. thermosulfidooxidans), and Acidithiobacillus caldus (A. caldus), while the pure culture needs at least 14 days. The results of X-ray Diffraction (XRD) and Inductively Coupled Plasma show that the sulfides were nearly fully solubilized. XRD results showed no pyrite in the residue, indicating that pyrite was almost fully removed while cassiterite was enriched compared with the original minerals. The high-throughput sequencing analysis showed that S. thermosulfidooxidans were the predominant species during the early bioleaching period, and L. ferriphilum were the predominant species in the following period. A. caldus is consistently detected and accounts for 30–50% of the different growth stages. This study supplied a potentially practical application for the desulfurization in tin ore. Full article

(This article belongs to the Section Purification Technology)

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13 pages, 3743 KiB

Open AccessArticle

Inserting an Additional Vortex Finder to Improve the Performance of Cyclones in Series

by Weihong He, Jingxuan Yang and Guogang Sun

Separations 2025, 12(3), 60; https://doi.org/10.3390/separations12030060 - 3 Mar 2025

Viewed by 534

Abstract

Multiple cyclones working in series are sufficient for heavy separation tasks at the cost of significant energy consumption. The majority of researchers conducting optimization studies on multiple cyclones have attempted to find the best possible compromise between pressure drop and collection efficiency by [...] Read more.

Multiple cyclones working in series are sufficient for heavy separation tasks at the cost of significant energy consumption. The majority of researchers conducting optimization studies on multiple cyclones have attempted to find the best possible compromise between pressure drop and collection efficiency by optimizing the geometry of the cyclones. In a departure from this approach, we report a novel design. Using the proposed method, exit gas is divided into dirty and clean gas by inserting a secondary vortex finder (SVF) into the primary vortex finder (PVF) of the previous cyclone. The dirty gas flows into the succeeding cyclone, whereas the clean gas passes over the succeeding cyclone and directly flows into the device farther behind. Methodologically, the separation performance was tested experimentally, and computational fluid dynamics (CFD) simulations were employed. The Reynolds Stress Model (RSM) for turbulence and the Discrete Phase Model (DPM) were used to simulate the turbulent two-phase flow within the gas–solid separator, capturing the three-dimensional, transient, and turbulent characteristics of the flow. Our performance test results showed that the new series configuration clearly reduces energy consumption while not hindering overall efficiency. The CFD simulation was used to optimize the SVF’s diameter and length. The results indicated that having an SVF with optimal dimensions significantly enhances the vortex flow in the separation space and thus improves the efficiency of the previous cyclone. In addition, an equation was established that describes the volume of gas flowing into a succeeding cyclone. Full article

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16 pages, 5306 KiB

Open AccessArticle

On the Identification of Mobile and Stationary Zone Mass Transfer Resistances in Chromatography

by Alessandra Adrover and Gert Desmet

Separations 2025, 12(3), 59; https://doi.org/10.3390/separations12030059 - 28 Feb 2025

Viewed by 433

Abstract

A robust and elegant approach, based on the Two-Zone Moment Analysis (TZMA) method, is proposed to assess the contributions of the mobile and stationary zones,

H_{C m}

and

H_{C s}

, to the C term

H_{C}

in the van Deemter [...] Read more.

A robust and elegant approach, based on the Two-Zone Moment Analysis (TZMA) method, is proposed to assess the contributions of the mobile and stationary zones,

H_{C m}

and

H_{C s}

, to the C term

H_{C}

in the van Deemter equation for plate height. The TZMA method yields two formulations for

H_{C m}

and

H_{C s}

, both fully equivalent in terms of

H_{C}

, yet offering different decompositions of the contributions from the mobile and stationary zones. The first formulation proposes an expression for the term

H_{C s}

that has strong similarities, but also significant differences, from the well-known and widely used one proposed by Giddings. While it addresses the inherent limitation of Giddings’ approach—namely, the complete decoupling of transport phenomena in the moving and stationary zones—it introduces the drawback of a non-unique decomposition of

H_{C}

. Despite this, it proves highly valuable in highlighting the limitations and flaws of Giddings’ method. In contrast, the second formulation not only properly accounts for the interaction between the moving and stationary zones, but provides a unique and consistent decomposition of

H_{C}

into its components. Three different geometries are investigated in detail: the 2D triangular array of cylinders (pillar array columns), the 2D array of rectangular pillars (radially elongated pillar array columns) and the 3D face-centered cubic array of spheres. It is shown that Giddings’ approach significantly underestimates the

H_{C s}

term, especially for porous-shell particles. Its accuracy is limited, being reliable only when intra-particle diffusivity (

D_{s}

) and the zone retention factor (

k^{″}

) are very low, or when axially invariant systems are considered. Full article

(This article belongs to the Section Chromatographic Separations)

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17 pages, 1767 KiB

Open AccessArticle

Solid-State Fermentation of Brewery Spent Grains to Enhance Biomolecule Extraction

by Chiara Mollea and Francesca Bosco

Separations 2025, 12(3), 58; https://doi.org/10.3390/separations12030058 - 22 Feb 2025

Viewed by 712

Abstract

In the present work, brewer’s spent grain, BSG, the main by-product of beer production, was applied for the recovery of total polyphenols (TPs). Whole and ground BSG (wBSG and gBSG), derived from a Pilsen beer, was subjected to a solvent extraction using ethanol/water [...] Read more.

In the present work, brewer’s spent grain, BSG, the main by-product of beer production, was applied for the recovery of total polyphenols (TPs). Whole and ground BSG (wBSG and gBSG), derived from a Pilsen beer, was subjected to a solvent extraction using ethanol/water (50:50 v/v), and then, to improve TP recovery, microwave, ultrasound bath or probe pre-treatments were applied. The highest total phenolic content (TPC) (5.8 mg GAE/g_DW) was obtained with gBSG pre-treated with the ultrasound (US) probe for 15 min at 250 W. Solid-state fermentation (SSF) with Phanerochaete chrysosporium, in microcosms was investigated to improve the release of TPs. Microcosms were monitored by means of CO₂ production, the total proteins, and laccase activity. Fungal growth on gBSG, after only 10 days of fermentation, resulted in a 30% increase in the TPC compared to the unfermented substrate. Applying US probe-assisted extraction to fermented, ground BSG resulted in a 51% improvement compared to the untreated sample. Full article

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

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12 pages, 826 KiB

Open AccessArticle

Isolation, Spectral Assignments and Absolute Configuration of a Linear Hexapeptide from the Culture Broth of the Plant-Associated Actinomycete Actinomycetospora sp. CA-287887

by Katerina Georgousaki, Nikolaos Tsafantakis, Ignacio González, Jesús Martin, Thomas Andrew Mackenzie, Sentiljana Gumeni, Ioannis P. Trougakos, Fernando Reyes, Olga Genilloud and Nikolas Fokialakis

Separations 2025, 12(3), 57; https://doi.org/10.3390/separations12030057 - 21 Feb 2025

Viewed by 353

Abstract

A high proteolytic-resistant hexapeptide (α_s1-CN 181–186) (1) along with two known 2,5-diketopiperazines, namely cyclo-(L-Pro-L-Phe) (2) and cyclo-(L-Pro-L-Tyr) (3), as well as the carboxylic acid 2-hydroxyphenylacetic acid (4), were isolated from the actinomycete strain [...] Read more.

A high proteolytic-resistant hexapeptide (α_s1-CN 181–186) (1) along with two known 2,5-diketopiperazines, namely cyclo-(L-Pro-L-Phe) (2) and cyclo-(L-Pro-L-Tyr) (3), as well as the carboxylic acid 2-hydroxyphenylacetic acid (4), were isolated from the actinomycete strain CA287887. The morphological 16S rRNA gene sequence and phylogenetic data of the strain exhibited high similarity with members of the genus Actinomycetospora. The structure of 1 was thoroughly investigated for the first time through the extensive use of 1D and 2D NMR experiments while its absolute configuration was determined by Marfey’s analysis. The anti-tyrosinase effects of the aforementioned compounds were investigated in vitro using kojic acid as the positive control (IC₅₀ 14.07 μΜ). Compound 3 exhibited the highest activity (IC₅₀ 28.69 μΜ), followed by compound 4 (IC₅₀ 98.29 μΜ). Compound 1 was further evaluated for cytotoxicity against HepG2, A2058, A549, and MiaPaca-2 cell lines. At all the tested concentrations (0.01–200 μg/mL), no cytotoxic effect was observed. Full article

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

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15 pages, 2978 KiB

Open AccessArticle

Effect of Vacuum Process on Enrichment of Low-Concentration Coal Mine Methane by Adsorption

by Yuanyuan Kang, Yingshu Liu, Wenhai Liu, Ye Li, Ningqi Sun, Quanli Zhang, Ziyi Li and Xiong Yang

Separations 2025, 12(3), 56; https://doi.org/10.3390/separations12030056 - 20 Feb 2025

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Abstract

The massive emission of low-concentration coal mine methane (CMM) has resulted in the ineffective utilization of a large amount of energy methane and caused environmental pollution. The gas mixture used in the study consisted of methane (CH₄) 12% and nitrogen (N [...] Read more.

The massive emission of low-concentration coal mine methane (CMM) has resulted in the ineffective utilization of a large amount of energy methane and caused environmental pollution. The gas mixture used in the study consisted of methane (CH₄) 12% and nitrogen (N₂) 88%. The adsorbent was coconut activated carbon. This paper uses the adsorption method to conduct enrichment research on 12% low-concentration CMM. Firstly, the variation in methane gas concentration under different desorption methods was studied by numerical simulation, and the desorption methods suitable for increasing methane concentration were analyzed. A three-bed VPSA CMM separation experimental device was built, and three enrichment processes of feed gas pressurization, exhaust gas pressurization, and vacuum exhaust (VE) were studied. The results show that using the three-bed vacuum pressure swing adsorption (VPSA) process can effectively enrich low-concentration CMM. Under the adsorption pressure of 110 kPa and the desorption pressure of 10 kPa, 12% of CMM can be enriched to more than 25%, with a recovery rate higher than 80%. The exhaust process can significantly increase the product gas concentration. The product gas concentration increased by 18.2%, with the product rising from 22.5% to 26.6% when the extraction step increased from 0 s to 8 s. This research may provide reliable fundamental data for industrial-scale low-concentration CMM enrichment. Full article

(This article belongs to the Section Separation Engineering)

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Open AccessArticle

Isolation and Hydrolysis of Proteins from Vigna umbellata and the Effect on Their Antioxidant and Anticancer Activities

by Leopoldo González-Cruz, Leonardo Morales-Cerda, Gerardo Teniente-Martínez, Carmen Valadez-Vega and Aurea Bernardino-Nicanor

Separations 2025, 12(3), 55; https://doi.org/10.3390/separations12030055 - 20 Feb 2025

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Abstract

Rice bean is a legume that is considered to be an important source of protein; it is still poorly understood but can produce peptides with various biological activities. These peptides can be released by enzymes during gastrointestinal passage and have a physiological effect [...] Read more.

Rice bean is a legume that is considered to be an important source of protein; it is still poorly understood but can produce peptides with various biological activities. These peptides can be released by enzymes during gastrointestinal passage and have a physiological effect on cancer cells. Since both the type of legume and the enzyme cocktail used are crucial for the production of peptides against certain cancer cell types, the anticancer effects of Vigna umbellata isolate and hydrolysate against MDA and SiHa cells were investigated in this study. The isolate was obtained via isoelectric precipitation, and the hydrolysate was obtained via pepsin P7012 and pancreatin P1750. The anticancer activity was determined by cell viability via the MTT assay, and a Pearson correlation coefficient was calculated to determine the relationships between the anticancer activity and total phenolic compounds, and the antioxidant activity of the isolated rice bean protein and its hydrolysate. The rice bean hydrolysate had a higher concentration of phenolic compounds than the isolate does, resulting in high antioxidant activity. The inhibition of proliferation in SiHa cells and MDA cells was twofold greater when they were exposed to the hydrolysate than when they were exposed to the isolate, with the IC₅₀ values at a concentration of 1000 μg/mL after 48 h of exposure for both MDA and SiHa cells. Rice bean protein hydrolysate is a good alternative for inhibiting the proliferation of SiHa cells and MDA cells, although further studies are needed. Full article

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

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Separations, Volume 12, Issue 3 (March 2025) – 18 articles

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