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Separations
Volume 13
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Separations, Volume 13, Issue 3 (March 2026) – 26 articles

Cover Story (view full-size image): Green Analytical Chemistry (GAC) provides a framework for reducing hazardous reagents, energy consumption, and waste. This topic has gained momentum across many chemical industries over the past 25 years. The purpose of this review is to highlight green approaches to analytical separation methods, including greenness assessment metrics, which have been reported in the literature for forensic science. Recent scientific literature highlights promising advances in greener sample preparation and chromatographic approaches, particularly in forensic toxicology and seized-drug analysis. Emerging trends include the increase in greenness assessment tools, use of green solvents, bio-based and deep eutectic solvent systems, the rapid expansion of microextraction techniques, as well as portable and miniaturized chromatographic instrumentation. View this paper
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32 pages, 19018 KB  
Article
A Cleaner Phosphoric Acid Production Path: Simultaneous P Extraction and REE Enrichment via Controlled HCl Leaching
by Jiawei Lin, Jue Kou, Chunbao Sun, Xiaojin Wen and Hongda Xu
Separations 2026, 13(3), 101; https://doi.org/10.3390/separations13030101 - 23 Mar 2026
Cited by 1 | Viewed by 1275
Abstract
Rare earth elements (REEs), as significant associated resources in sedimentary phosphate deposits, are commonly processed via the conventional hydrochloric acid wet-process phosphoric acid route (IMI process). In this method, phosphate and rare earth elements are typically leached simultaneously, which subsequently complicates their separation. [...] Read more.
Rare earth elements (REEs), as significant associated resources in sedimentary phosphate deposits, are commonly processed via the conventional hydrochloric acid wet-process phosphoric acid route (IMI process). In this method, phosphate and rare earth elements are typically leached simultaneously, which subsequently complicates their separation. In this study, a dolomitic rare earth-bearing phosphate concentrate from the Zhijin region of Guizhou Province was selected as the research subject. A stepwise phosphorus-prioritized leaching process was proposed, whereby precise regulation of hydrochloric acid dosage and reaction temperature enabled the preferential leaching of phosphorus (91.27%) and the directed enrichment of rare earth elements in the leaching residue (enrichment ratio of 4.7), thereby achieving efficient phosphorus–rare earth separation at the source. Subsequent process mineralogical analyses of the phosphate concentrate and the leaching residue revealed that rare earth elements occur in fluorapatite predominantly through isomorphic substitution. Following preferential phosphorus leaching, the residual Ca combines with F to form CaF2, while rare earth elements become concentrated within the leaching residue. Finally, kinetic investigations and response surface analyses demonstrated that the preferential phosphorus leaching process is governed by diffusion through the solid product layer. Among the influencing factors, hydrochloric acid dosage (A), leaching temperature (C), and the interactions between leaching time and the solid–liquid ratio (B, D) were identified as the most significant parameters affecting phosphorus leaching efficiency. This study elucidates, from a mechanistic perspective, the governing principles of phosphorus dissolution and rare earth enrichment within the hydrochloric acid preferential leaching system, thereby providing important theoretical support and technical guidance for simultaneously achieving efficient phosphorus extraction and targeted rare earth enrichment within the hydrochloric acid wet-process phosphoric acid production route. Full article
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20 pages, 1975 KB  
Article
Modelling Adsorption Breakthrough Curves
by Xin Shen and Jules Thibault
Separations 2026, 13(3), 100; https://doi.org/10.3390/separations13030100 - 20 Mar 2026
Cited by 1 | Viewed by 1748
Abstract
Adsorption is a widely employed separation technique valued for its low energy requirements and its applicability to diverse processes, including air separation, water purification, chromatographic analysis, wastewater treatment, and protein immobilization on biomaterials. Industrial adsorption–desorption cycles are typically carried out in parallel packed-bed [...] Read more.
Adsorption is a widely employed separation technique valued for its low energy requirements and its applicability to diverse processes, including air separation, water purification, chromatographic analysis, wastewater treatment, and protein immobilization on biomaterials. Industrial adsorption–desorption cycles are typically carried out in parallel packed-bed columns. The accurate design and optimization of these columns rely on experimental breakthrough curves. These curves provide essential information on adsorption capacity and mass-transfer kinetics. In this study, five modelling approaches, based on instantaneous adsorption, non-instantaneous adsorption, Fickian diffusion, and anomalous diffusion, were evaluated for their ability to predict breakthrough behaviour during the adsorption of butanol on activated carbon. The first four models were formulated using conventional partial differential equations of varying complexity, whereas the fifth model incorporated anomalous diffusion through fractional-order differential equations. The results indicate that model performance depended strongly on the adsorbent type: certain models provided superior predictions for one activated carbon, while different models were more accurate for the other. Full article
(This article belongs to the Special Issue Numerical Modeling and Computation in Separation and Adsorption)
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19 pages, 3132 KB  
Article
Inorganic–Organic Hybrid Polymer for Fine-Rich Coal Slime Water Treatment: Performance and Interfacial Adsorption Mechanism on Kaolinite Aluminol Surface
by Jing Chang, Hang Zhao, Shizhen Liang, Xihao Feng, Jia Xue and Wei Zhao
Separations 2026, 13(3), 99; https://doi.org/10.3390/separations13030099 - 19 Mar 2026
Viewed by 632
Abstract
High-ash coal slime water, characterized by its stable colloidal suspension of fine kaolinite particles, poses a significant challenge in the coal preparation industry because it is hard to achieve efficient solid–liquid separation. While traditional coagulants and flocculants often suffer from limited bridging capabilities [...] Read more.
High-ash coal slime water, characterized by its stable colloidal suspension of fine kaolinite particles, poses a significant challenge in the coal preparation industry because it is hard to achieve efficient solid–liquid separation. While traditional coagulants and flocculants often suffer from limited bridging capabilities and distinct pH sensitivity, novel molecular architectures offer potential solutions. In this study, a star-shaped inorganic–organic hybrid flocculant (Al-PAM) was synthesized via in situ polymerization. Its flocculation performance and interfacial adsorption mechanism on the specifically targeted aluminol basal plane of kaolinite were systematically investigated and compared with Polyaluminum Chloride (PAC), Non-ionic Polyacrylamide (NPAM), and their combination (PAC + NPAM). Settling tests revealed that Al-PAM exhibited superior performance at a significantly lower dosage (10 mg∙L−1) compared to the PAC + NPAM binary reagent system. It achieved a rapid initial settling velocity and reduced the supernatant turbidity to 48.45 NTU, while maintaining a near-neutral pH favorable for water recycling. Furthermore, Quartz Crystal Microbalance with Dissipation (QCM-D) monitoring confirmed that Al-PAM forms a thick, viscoelastic, and irreversible adsorption layer on the Al2O3 substrate. The dissipation shifts (ΔD) revealed that the star-shaped architecture promotes distinct bridging and electrostatic adsorption, overcoming the limitation of linear polymers. This work elucidates the specific contribution of the alumina-surface interaction with flocculants and proposes an efficient strategy for treating refractory coal slime water. Full article
(This article belongs to the Special Issue Separation Technology in Mineral Processing)
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16 pages, 592 KB  
Review
Macroporous Resin-Based Purification of Flavonoids: Quantitative Structure–Adsorption Relationships and a Preliminarily Validated Selection Framework
by Gang Tian, Yihang Tian, Shiping Cheng, Cong Yang and Guoxu He
Separations 2026, 13(3), 98; https://doi.org/10.3390/separations13030098 - 19 Mar 2026
Cited by 2 | Viewed by 1887
Abstract
Macroporous adsorption resins (MARs) are widely used for preparative-scale flavonoid purification, yet rational resin selection remains difficult because flavonoids differ substantially in hydrophobicity, hydrogen-bonding capacity, molecular size, and planarity. This review reorganizes the available literature into a structure-guided and data-supported selection aid rather [...] Read more.
Macroporous adsorption resins (MARs) are widely used for preparative-scale flavonoid purification, yet rational resin selection remains difficult because flavonoids differ substantially in hydrophobicity, hydrogen-bonding capacity, molecular size, and planarity. This review reorganizes the available literature into a structure-guided and data-supported selection aid rather than a fully predictive model. A systematic search of Web of Science, Scopus, PubMed, and CNKI (January 2000 to February 2026) identified 55 studies for qualitative synthesis. Because many reports describe total flavonoids or mixed extracts rather than explicit single-compound adsorption data, only the subset with sufficiently clear compound-level or narrowly interpretable adsorption information was used for cautious comparative interpretation. Across the compiled evidence, non-polar resins generally favored less polar aglycones and methoxylated flavonoids, whereas medium-polar and polar resins more often performed well for glycosylated or more hydrophilic targets. On this basis, flavonoids were organized into four operational classes linked to recommended resin polarity, indicative adsorption capacity ranges, and typical ethanol-elution windows. A retrospective comparison with independent literature cases suggests practical value for initial resin prioritization, but the framework should be interpreted primarily as a heuristic, trend-based guide rather than as a strictly predictive model, because mixed-matrix effects, pore accessibility, and competitive adsorption can override simple polarity matching. A generalized operating window for adsorption and desorption is also summarized. Overall, this review provides a mechanism-informed starting point for resin screening while making explicit the conditions under which case-specific experiments remain necessary. Full article
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16 pages, 6071 KB  
Article
Parametric Study of Flow Uniformity for Mitigating Ammonium Bisulfate Fouling in Air Preheaters Based on CFD Simulations
by Li Yao, Kuan Xu, Linfang Zhang and Xiaodong Wu
Separations 2026, 13(3), 97; https://doi.org/10.3390/separations13030097 - 19 Mar 2026
Viewed by 607
Abstract
Ammonium bisulfate (ABS) fouling in air preheaters has become a critical challenge restricting the safe and efficient operation of coal-fired units. Optimizing the flow field of the outlet of the upstream SCR system is a potentially effective path to mitigate ABS fouling. In [...] Read more.
Ammonium bisulfate (ABS) fouling in air preheaters has become a critical challenge restricting the safe and efficient operation of coal-fired units. Optimizing the flow field of the outlet of the upstream SCR system is a potentially effective path to mitigate ABS fouling. In this work, CFD simulations were conducted on the SCR De-NOx system and its succeeding flue ducts connected to the air preheater. The simulation results of the original design show that a significant velocity deviation exists at the inlet of the air preheater (with the CV1 up to 53.2%), with a portion of the flue gas adhering to the walls, which could induce ABS fouling in the low-temperature region. By adding flow guide plates into the flue duct, the flow uniformity before the air preheater was expected to be effectively improved. Notably, considering the deposition characteristics of ABS and the operating characteristics of the rotary air preheater, this study proposed a novel evaluation indicator, radial variance coefficient (CV2), which focuses on the velocity uniformity based on the annular sector unit, to indicate the risk of ABS deposition. The influence on velocity uniformity of different flow guide plate layouts was analyzed. Based on the multiple evaluation metrics including pressure drop and flow uniformity, the optimal layout scheme was then selected. After optimization, the radial variance coefficient decreased from 30.7% to 11.7%, with the pressure drop slightly increased from 50 Pa to 80 Pa. This study could help to reduce unit failure frequency and support efficient operation of coal-fired power plants. Full article
(This article belongs to the Special Issue Numerical Modeling and Computation in Separation and Adsorption)
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18 pages, 3130 KB  
Article
Efficient Removal of Oxytetracycline by Fe/N Co-Doped Biochar Derived from Fava Bean Straw: Performance and Mechanisms
by Xinyu Dong, Yu Zhang, Xinyi Zhang, Yaping Xu, Haitao Zhao, Nan Jiang, Lijun Meng and Shengyang Zheng
Separations 2026, 13(3), 96; https://doi.org/10.3390/separations13030096 - 18 Mar 2026
Cited by 1 | Viewed by 495
Abstract
To efficiently remove oxytetracycline (OTC) pollution from water bodies, this study utilized fava bean straw as a precursor to synthesize iron-nitrogen (Fe/N) co-doped biochar via pyrolysis. By regulating the synthesis ratio of iron and nitrogen, the material’s adsorption performance was optimized. The adsorption [...] Read more.
To efficiently remove oxytetracycline (OTC) pollution from water bodies, this study utilized fava bean straw as a precursor to synthesize iron-nitrogen (Fe/N) co-doped biochar via pyrolysis. By regulating the synthesis ratio of iron and nitrogen, the material’s adsorption performance was optimized. The adsorption characteristics and mechanisms of OTC were systematically investigated. The findings reveal that when the proportion of iron to nitrogen is set at 1:3, the adsorption efficacy reaches its peak. Moreover, this material demonstrates outstanding reusability characteristics. The outcomes of kinetic fitting suggest that the adsorption procedure adheres to the pseudo-second-order kinetic model (R2 = 0.967), primarily characterized by chemisorption. The isothermal adsorption data better fit the Langmuir model (R2 = 0.9984), with a theoretically attainable upper-limit adsorption capacity reaching 666.13 mg/g. This signifies the occurrence of monolayer adsorption, while the adsorption procedure constitutes an endothermic reaction. Based on characterization and mechanistic analysis, it can be concluded that the adsorption mechanism of Fe1N3KBC on OTC mainly involves π-π stacking interactions and chelation reactions. The Fe/N co-doped biochar prepared in this present research features readily available raw materials and a simple preparation process, combining high adsorption efficiency with excellent stability. It provides a novel technical paradigm for developing environmentally friendly adsorbents to address antibiotic pollution in water bodies. Full article
(This article belongs to the Special Issue Adsorption/Degradation for Environmental Pollutants)
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26 pages, 2255 KB  
Article
Development of the VARICOL Process for the Resolution of Racemic Menthol
by Linhe Sun, Ying Yang and Jianguo Yu
Separations 2026, 13(3), 95; https://doi.org/10.3390/separations13030095 - 17 Mar 2026
Cited by 1 | Viewed by 696
Abstract
This paper reports the chiral separation of menthol enantiomers using the VARICOL process to improve productivity. Amylose 3,5-dimethylphenylcarbamate coated on silica gel was employed as the chiral stationary phase, and n-hexane/2-propanol (95/5, v/v) was used as the eluent. To design [...] Read more.
This paper reports the chiral separation of menthol enantiomers using the VARICOL process to improve productivity. Amylose 3,5-dimethylphenylcarbamate coated on silica gel was employed as the chiral stationary phase, and n-hexane/2-propanol (95/5, v/v) was used as the eluent. To design and optimize the VARICOL process, a linear driving-force model was developed to predict the separation performance. Separation regions of the conventional simulated moving bed (SMB) and VARICOL processes were evaluated and compared. It was found that, under an outlet purity requirement of 95.0%, the five-column VARICOL process has a separation region comparable to that of the six-column conventional SMB process. As an illustrative example, a five-column VARICOL unit and a six-column conventional SMB unit, both operating under the same conditions, were employed to resolve the menthol racemate. Purities for both the extract and raffinate were above 95.0%, and a productivity of 0.400 gracemate/(LCSP∙min) and a solvent consumption of 0.355 L/gracemate were achieved in the VARICOL process. Productivity increased by 20% while solvent consumption maintained relative to the conventional SMB process, though product purities decreased slightly. Full article
(This article belongs to the Topic Processing Design and Intensification in Chemical Engineering)
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20 pages, 807 KB  
Article
HPLC-DAD Determination of Hydroquinone, Salicylic Acid, and Niacinamide in Skin-Whitening Products: Method Validation and Safety Evaluation
by Khadejah D. Otaif
Separations 2026, 13(3), 94; https://doi.org/10.3390/separations13030094 - 14 Mar 2026
Viewed by 2451
Abstract
Skin-whitening products (SWPs) are widely used, yet many contain prohibited or misdeclared depigmenting agents posing safety concerns. This study developed and validated a sensitive and reliable HPLC-DAD method for the simultaneous determination of hydroquinone (HQ), salicylic acid (SAL), and niacinamide (NIC) in commercial [...] Read more.
Skin-whitening products (SWPs) are widely used, yet many contain prohibited or misdeclared depigmenting agents posing safety concerns. This study developed and validated a sensitive and reliable HPLC-DAD method for the simultaneous determination of hydroquinone (HQ), salicylic acid (SAL), and niacinamide (NIC) in commercial and homemade SWPs. Validation followed ICH Q2(R1), demonstrating good specificity, linearity (R2 > 0.9999), method precision (%RSD < 2%), and LOD/LOQ values of 0.2 and 0.7 µg/mL for all analytes. Recoveries of 97.48–99.83% for HQ, 99.37–101.26% for NIC, and 83.04–95.38% for SAL were also obtained. Analysis of 51 products revealed major discrepancies between declared and measured contents. HQ was detected in 18.60% of commercial samples despite its prohibition in OTC cosmetic formulations; none of the SAL-containing products matched their labels, and NIC appeared in 25.58% of samples, with only one sample compliant with its declared content. Homemade products showed undeclared HQ in 62.50% of samples, 25% of samples exceeded the 2% permitted SAL limit, and unregulated multi-ingredient combinations. Risk assessment showed all HQ-containing commercial products and several homemade formulations posed unacceptable systemic exposure risks (MoS < 100). Overall, the proposed method provides a practical and accessible approach for routine quality control and market surveillance of cosmetic products. Full article
(This article belongs to the Section Chromatographic Separations)
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17 pages, 1724 KB  
Article
Differential Behavior of Salt and Organic Matter Passage in 2-Pass RO Systems for Ultrapure Water Production
by Changryeol Oh, Dongkeon Kim and Suhan Kim
Separations 2026, 13(3), 93; https://doi.org/10.3390/separations13030093 - 13 Mar 2026
Cited by 2 | Viewed by 1034
Abstract
This study investigates how membrane transport characteristics affect permeate quality in a 2-pass reverse osmosis (RO) system for ultrapure water (UPW) production. Unlike conventional RO, UPW-RO operates in an ultra-low concentration range. Seven commercial 4-inch RO membrane modules spanning a wide range of [...] Read more.
This study investigates how membrane transport characteristics affect permeate quality in a 2-pass reverse osmosis (RO) system for ultrapure water (UPW) production. Unlike conventional RO, UPW-RO operates in an ultra-low concentration range. Seven commercial 4-inch RO membrane modules spanning a wide range of water (A) and salt (B) permeability coefficients were evaluated under various second-pass RO feed concentrations (specifically, total dissolved solids (TDS) and total organic carbon (TOC)). Second-pass RO permeate TDS remained almost constant regardless of membrane specifications, whereas the permeate TOC was strongly membrane-dependent. RO permeates from high-permeability membranes showed significantly higher TOC than those from high-selectivity membranes. The experiments also revealed that a high-permeability membrane configuration for both RO passes resulted in excessive TOC leakage, while a high-selectivity membrane configuration mitigated TOC passage at the cost of a high operating pressure requirement. A combination of a high-permeability membrane (the first pass) and a high-selectivity membrane (the second pass) could achieve an acceptable TOC passage with a moderate operating pressure requirement in UPW-RO systems. Full article
(This article belongs to the Special Issue Design and Preparation of Sustainable Separation Membrane for Efficient Water Purification)
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20 pages, 1274 KB  
Article
Integrated Purification Process for 5-Aminolevulinic Acid Phosphate Produced via Biological Fermentation
by Naoyuki Iwata, Kazunari Fukumoto and Mitsuharu Uchino
Separations 2026, 13(3), 92; https://doi.org/10.3390/separations13030092 - 9 Mar 2026
Cited by 1 | Viewed by 1281
Abstract
5-aminolevulinic acid (5-ALA) affords various positive health effects, including benefits for conditions such as diabetes. Biological fermentation holds potential for efficiently mass-producing biomolecules, including 5-ALA, yet it generally results in a mixture of target molecules and impurities, including byproducts. Pyrazine-2,5-dipropionic acid (PY), a [...] Read more.
5-aminolevulinic acid (5-ALA) affords various positive health effects, including benefits for conditions such as diabetes. Biological fermentation holds potential for efficiently mass-producing biomolecules, including 5-ALA, yet it generally results in a mixture of target molecules and impurities, including byproducts. Pyrazine-2,5-dipropionic acid (PY), a dimer of 5-ALA, can easily form in 5-ALA production and is one of its major impurities. In this study, we developed an integrated purification process for 5-aminolevulinic acid phosphate (5-ALAP) produced via biological fermentation. The process consists of 16 stages, including impurity removal (ion-exchange resins) and crystallization. Three types of ion-exchange resin (IER) columns were combined to remove impurities such as byproducts and pigment. Comprehensive condition setting for crystallization was carried out to reduce the amount of residual poor solvent in the 5-ALAP crystals. The obtained crystals contained significantly fewer impurities (<0.05% vs. 5-ALAP), such as PY, compared with their commercially available counterparts. The residual poor solvent in the 5-ALAP crystals was reduced to below 1000 ppm under the crystallization conditions. We confirmed the high scalability of the purification method developed in this study. Therefore, this article provides an industrially applicable purification process for fermentatively produced 5-ALA. Full article
(This article belongs to the Section Purification Technology)
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24 pages, 15417 KB  
Article
Effect of Electrical Conductivity Degradation on Particle Motion Trajectories of Crushed Lithium-Ion Battery Products During Eddy Current Separation
by Yuxuan Bai, Huabing Zhu, Haijun Bi and Yigeng Huang
Separations 2026, 13(3), 91; https://doi.org/10.3390/separations13030091 - 8 Mar 2026
Viewed by 698
Abstract
Traditional lithium-ion battery recycling relies mainly on pyrolysis or chemical leaching to separate current collectors from electrode materials, inevitably resulting in secondary pollution. In contrast, eddy current separation (ECS) applied to crushed lithium-ion battery residues can substantially reduce the introduction of contaminants while [...] Read more.
Traditional lithium-ion battery recycling relies mainly on pyrolysis or chemical leaching to separate current collectors from electrode materials, inevitably resulting in secondary pollution. In contrast, eddy current separation (ECS) applied to crushed lithium-ion battery residues can substantially reduce the introduction of contaminants while minimizing material losses. However, the heterogeneous composition and diverse surface characteristics of crushed battery products, together with the conductivity degradation of electrode materials after long-term use, make conventional empirical particle–trajectory correlations inadequate for accurate optimization of ECS operating parameters. In addition, the coupling between process parameters and the resultant forces acting on conductive particles, as well as the associated separation trajectories, remain insufficiently understood, which severely limits process controllability. A force–trajectory model was therefore developed for spent current collectors and conductivity-degraded LiFePO4 to describe their particle dynamics in an alternating magnetic field. The results demonstrate that the trajectory of LiFePO4 is very similar to that of non-conductive materials, thereby facilitating its effective separation from metallic components in battery scrap. Eddy current separation experiments further confirm the accuracy of the model predictions with respect to separation trajectories and the influence of key process parameters. On this basis, optimization of the operating parameters increased the separation efficiency of the cathode material to above 95.1%. The clarified ECS mechanism for current collectors and electrode materials provides new insights into the mechanical pre-sorting and mechanistic understanding of lithium-ion battery fragments, thereby contributing to reductions in contaminant introduction during battery material recycling. Full article
(This article belongs to the Topic Advances in Separation Engineering)
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18 pages, 1062 KB  
Review
Hesperidin from Citrus Processing By-Products: Integrated Strategies from Extraction to Downstream Separation
by Li Shang, Yiyang Zhang and Miao Long
Separations 2026, 13(3), 90; https://doi.org/10.3390/separations13030090 - 8 Mar 2026
Viewed by 1656
Abstract
The extraction of functional organic compounds from natural products has become an important focus of current research. Citrus fruits are among the most widely produced fruits worldwide and have attracted increasing attention because of their pleasant flavor and rich content of bioactive compounds. [...] Read more.
The extraction of functional organic compounds from natural products has become an important focus of current research. Citrus fruits are among the most widely produced fruits worldwide and have attracted increasing attention because of their pleasant flavor and rich content of bioactive compounds. Hesperidin, the focus of this review, is a representative flavonoid glycoside that is abundant in citrus fruits and their processing by-products. Owing to its unique molecular structure and physicochemical properties, hesperidin frequently coexists with structurally similar flavonoids. This similarity makes its separation and purification particularly challenging. Although many studies have reported different methods for the extraction and purification of hesperidin, most of them concentrate on individual techniques. Systematic analyses of how upstream extraction strategies affect downstream separation efficiency are still limited. In this review, separation strategies for hesperidin are systematically discussed, covering the entire process from extraction to downstream purification. The focus shifts from isolated separation methods to a strategy-oriented design. Special attention is given to how different extraction approaches influence matrix complexity, and, consequently, the difficulty of subsequent separation steps. Downstream separation technologies, including adsorption, liquid–liquid partitioning, crystallization, and chromatography, are compared from the perspectives of separation mechanisms and process integration. Based on a comparative analysis of crystallization, phase partitioning, membrane processing, adsorption, and chromatographic techniques, this review discusses the typical process roles of different separation strategies. Solubility-driven crystallization and membrane-based clarification are identified as more suitable for large-scale processing, whereas adsorption and chromatography are more appropriate as enrichment and polishing steps, respectively. In addition, key control points for green extraction–separation integration are identified, including solvent recyclability, matrix complexity control, and early-stage load reduction. This work aims to provide a practical reference for the sustainable and scalable separation of flavonoid glycosides from citrus by-products. Full article
(This article belongs to the Special Issue Extraction, Purification and Functional Substances of Natural Products and Plants)
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18 pages, 7613 KB  
Article
Cu-Ni Captures Platinum Group Metals from Spent Automotive Exhaust Catalysts
by Jiahao Li, Jibiao Han, Han Yang, Guozhen Wang, Kuo Liu, Lang Liu, Yong Li, Qingfeng Xiong, Junmei Guo, Bin Yang and Haigang Dong
Separations 2026, 13(3), 89; https://doi.org/10.3390/separations13030089 - 6 Mar 2026
Cited by 1 | Viewed by 1212
Abstract
Platinum group metals (PGMs) are strategic metals, and recycling PGMs in spent automobile exhaust catalysts (SACs) is a key path to alleviate the contradiction between resource supply and demand. This paper proposes a new Cu-Ni capture process and conducts research on the recovery [...] Read more.
Platinum group metals (PGMs) are strategic metals, and recycling PGMs in spent automobile exhaust catalysts (SACs) is a key path to alleviate the contradiction between resource supply and demand. This paper proposes a new Cu-Ni capture process and conducts research on the recovery of PGMs from SACs. Through the binary phase diagram analysis of Cu, Ni and PGMs and the thermodynamic calculation of the system reduction reaction, the feasibility of this technology was theoretically confirmed. Experimental results show that under the conditions of a temperature of 1450 °C, a holding time of 90 min, a Cu-Ni ratio of 1:1, and a basicity of 0.58, the recovery rates of Pt, Pd, and Rh reached 99.2%, 99.34%, and 98.48% respectively. Combined with orthogonal experiments, it was verified that temperature is the most influential factor on the recovery rate, and the four-stage capture mechanism of “initial diffusion—droplet aggregation—sedimentation and wetting—slag–metal separation” was clarified. This process reduces the melting temperature and provides new technology for green and efficient recycling of PGMs. Full article
(This article belongs to the Special Issue Separation Techniques in Recovery of Valuable Metal Resources)
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18 pages, 3178 KB  
Article
Moisture Migration and Drying Mechanisms of Coal Slime Under Hot–Air and Steam Flash Drying
by Gangqiang Zhao, Ke Li, Fengyuan Cui, Shaoyu Yao, Yadong Zhang and Zongsheng Sun
Separations 2026, 13(3), 88; https://doi.org/10.3390/separations13030088 - 6 Mar 2026
Cited by 2 | Viewed by 830
Abstract
Coal slime, typically with particle sizes below 1 mm, is difficult to utilize directly and is frequently associated with energy loss and environmental burden. This study comparatively investigates hot–air drying and transient steam flash drying for the dehydration and upgrading of filter–pressed coal [...] Read more.
Coal slime, typically with particle sizes below 1 mm, is difficult to utilize directly and is frequently associated with energy loss and environmental burden. This study comparatively investigates hot–air drying and transient steam flash drying for the dehydration and upgrading of filter–pressed coal slime. In hot–air drying, elevated temperature and reduced particle size markedly accelerate the drying rate, and the apparent activation energy ranges from 18.39 to 20.96 kJ·mol−1 for different particle sizes. For steam flash drying, the influences of steam pressure, particle size, and holding time on moisture–removal efficiency and physicochemical structure are evaluated. The dehydration performance is enhanced by higher steam pressure and larger particle size, reducing the moisture content of the coal slime from 38% to 20%, with approximately 80% of the total water removed during the transient depressurization stage. Structural analyses reveal partial decomposition of oxygen–containing functional groups and mesopore contraction after flash treatment. Compared with hot–air drying, steam flash drying achieves shorter processing time and lower specific energy consumption. These findings indicate that steam flash drying is governed by a pressure–induced phase transition and enhanced thermodynamic driving force, providing an intensified pathway for the efficient upgrading of high–moisture coal slime. Full article
(This article belongs to the Special Issue Research Progress of Gas–Solid Fluidized Dry Separation)
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11 pages, 1658 KB  
Article
Determination of Benzo[a]pyrene in Edible Oil Using Nickel Oxide Deposited Silica-Based Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography–Diode Array Detector
by Yuejiao Yang, Yingjie Guo, Guanglin Huang and Qiongwei Yu
Separations 2026, 13(3), 87; https://doi.org/10.3390/separations13030087 - 5 Mar 2026
Viewed by 1115
Abstract
A simple, rapid, and cost-effective method for the determination of benzo[a]pyrene (BaP) in edible oil was developed and validated. Nickel oxide-deposited silica (SiO2@NiO) was employed as a solid-phase extraction (SPE) adsorbent for the extraction of BaP from edible oil, followed by [...] Read more.
A simple, rapid, and cost-effective method for the determination of benzo[a]pyrene (BaP) in edible oil was developed and validated. Nickel oxide-deposited silica (SiO2@NiO) was employed as a solid-phase extraction (SPE) adsorbent for the extraction of BaP from edible oil, followed by high-performance liquid chromatography–diode array detector (HPLC-DAD) analysis of BaP. The edible oil was diluted with n-hexane and directly loaded to SiO2@NiO for SPE. The n-hexane was also used to clean the fat-soluble interference substance in the edible oil, and BaP was selectively captured using SiO2@NiO through the electron donor–acceptor interaction. The SPE conditions, including the amount of adsorbent, volume of washing solvent, and type and volume of desorption solvent, were optimized. This SiO2@NiO-based SPE coupled with the HPLC-DAD method demonstrated good linearity within a BaP concentration range of 6–1875 ng/g in edible oils, with a limit of detection of 1.3 ng/g, spiked recovery of 97.4–105.1%, and relative standard deviation (RSD) of <3.0%. The method was applied to the analysis of BaP in 11 real oil samples (soybean oil, olive oil, corn germ oil, flaxseed oil, walnut oil, sunflower kernel oil, peanut oil, unrefined oil, and high-temperature frying oil), and the results show that the unrefined oil and high-temperature frying oil were at risk of BaP exceeding acceptable level. Full article
(This article belongs to the Special Issue Research on Novel Separation Media and Separation/Analysis Technologies)
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21 pages, 4880 KB  
Article
The Effect of Inorganic Mineral Embedding Features in Coking Middling Coals on Their Liberation and Flotation Separation
by Yuzhe Hua, Wenli Liu and Qiming Zhuo
Separations 2026, 13(3), 86; https://doi.org/10.3390/separations13030086 - 4 Mar 2026
Viewed by 650
Abstract
China’s coking coal resources are scarce, and maximizing the recycling of these resources is the primary objective of coal processing and utilization. The embedding features of inorganic minerals within coking middling coal resources are an inherent factor influencing their liberation and separation efficiency. [...] Read more.
China’s coking coal resources are scarce, and maximizing the recycling of these resources is the primary objective of coal processing and utilization. The embedding features of inorganic minerals within coking middling coal resources are an inherent factor influencing their liberation and separation efficiency. However, current research lacks a systematic investigation into how the embedding features of inorganic minerals in coking middling coal affect their liberation characteristics and flotation separation performance. This study examines three Chinese coking middling coal samples with distinct embedding features. Based on quantitative characterization of inorganic mineral embedding, grinding tests with varying durations and flotation separation tests on post-grinding products were conducted. Liberation and separation efficiencies were evaluated to explore the influence of inorganic mineral embedding on liberation degree and the subsequent impact of the liberation degree on flotation performance. The results indicate that the three coking middling coal samples with different embedding features exhibit significant differences in the dissociation behavior between inorganic minerals and organic matter. The particle size (D) of inorganic mineral phases is the primary factor influencing the liberation degree of inorganic minerals, while the complexity of intergrowth between inorganic minerals and organic matter (CIG) is a secondary factor. The CIG is the primary factor affecting the liberation of organic matter. As the liberation of inorganic minerals and organic matter increases, the separation efficiency improves for the Liuwan middling coal samples, whereas it deteriorates for the Shaqu and Changzhi samples. Full article
(This article belongs to the Special Issue Application of Green Flotation Technology in Mineral Processing)
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20 pages, 4403 KB  
Article
Effects of Metal Ions on the Flotation of Fluorite and Barite: An Experimental and Mechanistic Investigation
by Ying Wei, Yuqiong Li, Yingchao Liu, Yuxin Guo, Caiyun Li and Wanglin Yang
Separations 2026, 13(3), 85; https://doi.org/10.3390/separations13030085 - 3 Mar 2026
Cited by 1 | Viewed by 658
Abstract
Fluorite (CaF2) and barite (BaSO4) commonly occur together in the same deposits. Due to their similar surface chemical properties, their flotation separation is often challenging. In flotation pulps, dissolved metal ions can further interfere with separation and exert a [...] Read more.
Fluorite (CaF2) and barite (BaSO4) commonly occur together in the same deposits. Due to their similar surface chemical properties, their flotation separation is often challenging. In flotation pulps, dissolved metal ions can further interfere with separation and exert a pronounced influence on the flotation behavior of these minerals. This study investigated the effects of metal ions frequently encountered in industrial pulps (Fe3+, Al3+, Mg2+, Ca2+, and Zn2+) on the floatability of fluorite and barite in a sodium oleate (NaOL) collector system. The aims were to clarify how metal ions affect flotation behavior and to evaluate the feasibility of enhancing fluorite–barite separation via metal-ion regulation. Flotation results showed that, in the NaOL system, the largest floatability difference between fluorite and barite occurred at pH 10. Al3+ exhibited the strongest depression on barite while only weakly affecting fluorite flotation. Fe3+ and Mg2+ caused slight depression of barite, whereas Ca2+ and high concentrations of Zn2+ (>20 mg/L) promoted barite flotation. Overall, these metal ions had little influence on fluorite flotation. Adsorption measurements indicated that Al3+ reduced NaOL adsorption by more than 40% and decreased the contact angle from 35.6° to 23.1°, resulting in a sharp loss of surface hydrophobicity. ICP adsorption tests revealed that Al3+ showed the highest uptake on barite surfaces. Density functional theory (DFT) calculations further confirmed that surface SO42− groups on barite form strong chemisorption with hydrolyzed Al species (adsorption energy: −436.19 kJ/mol), whereas only weak physisorption occurs on hydroxylated fluorite surfaces (adsorption energy: −43.73 kJ/mol). This study provides insights into the flotation separation of non-metallic minerals dominated by polar ionic bonding and offers practical guidance for efficient fluorite–barite separation under complex ionic environments. Full article
(This article belongs to the Special Issue Efficient Extraction, Separation and Purification of Critical Metal Resources)
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31 pages, 1562 KB  
Review
Green Approaches in Forensic Separations—An Overview
by Thomas A. Brettell
Separations 2026, 13(3), 84; https://doi.org/10.3390/separations13030084 - 3 Mar 2026
Cited by 2 | Viewed by 2307
Abstract
Green Analytical Chemistry (GAC) provides a framework for reducing hazardous reagents, energy consumption, and waste. The topic has gained momentum across many chemical industries over the past 25 years; however, progress in implementing sustainable methods and conducting greenness assessments within forensic laboratories has [...] Read more.
Green Analytical Chemistry (GAC) provides a framework for reducing hazardous reagents, energy consumption, and waste. The topic has gained momentum across many chemical industries over the past 25 years; however, progress in implementing sustainable methods and conducting greenness assessments within forensic laboratories has been comparatively slow. The purpose of this review is to highlight green approaches to analytical separation methods, including greenness assessment metrics, that have been reported in the literature for forensic chemistry and toxicology applications and to raise awareness of GAC in the forensic field. Recent scientific literature highlights promising advances in greener sample preparation and chromatographic approaches, particularly in forensic toxicology and seized-drug analysis. Emerging trends include the use of green solvents, bio-based and deep eutectic solvent systems, and the rapid expansion of microextraction techniques such as SPME, LPME, MEPS, FPSE, and DLLME, which reduce solvent volumes, minimize waste, and support higher-throughput workflows. Parallel developments in portable and miniaturized chromatographic instrumentation such as miniaturized LC–MS systems with increased detection specificity and Lab-on-a-Chip applications show promise for in situ measurements in the field. Ambient ionization mass spectrometry—in particular, DESI and DART—has had a major impact on forensic chemistry by providing tools for the rapid and direct analysis of chemical compounds in complex matrices with little or no sample preparation. Greenness assessment tools—including AGREE, AGREEprep, Eco-Scale, GAPI, and BAGI—are increasingly applied to evaluate analytical methods in forensic chemistry and toxicology, including those used for novel psychoactive substances. Although many green methodologies are well documented, their routine implementation remains limited. The continued integration of green solvents, microextractions, portable instrumentation, and standardized greenness metrics will be essential for advancing sustainable forensic separations. Full article
(This article belongs to the Section Forensic Science and Toxicology)
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46 pages, 15545 KB  
Review
Converting Industrial Inorganic Solid Wastes from Chemical Processes into High-Efficiency Adsorbents: A Review
by Ruiling Du, Xiaoya Li and Shuai Wang
Separations 2026, 13(3), 83; https://doi.org/10.3390/separations13030083 - 3 Mar 2026
Cited by 1 | Viewed by 1825
Abstract
With ongoing development in the process industries, the accumulation of industrial inorganic solid wastes (IISWs) has become increasingly significant. IISWs are characterized by large volume and toxicity and pose challenges in treatment and control. IISWs from chemical processes mainly include red mud (RM), [...] Read more.
With ongoing development in the process industries, the accumulation of industrial inorganic solid wastes (IISWs) has become increasingly significant. IISWs are characterized by large volume and toxicity and pose challenges in treatment and control. IISWs from chemical processes mainly include red mud (RM), zinc slag, lithium slag (LS), electrolytic manganese residue (EMR), phosphogypsum (PG), water treatment sludge (WTS), sewage sludge, blast furnace slag (BFS), steel slag (SS), coal fly ash (CFA), coal gasification slag (CGS), copper smelting slag (CSS), and lead smelting slag (LSS). Having been chemically processed, they exhibit complex compositions that pose challenges for further utilization. In this paper, we comprehensively review the preparation of adsorbents from IISWs as raw materials, the applications of IISW-derived adsorbents, and their adsorption mechanisms. The obtained adsorbents include modified IISWs, zeolites, porous ceramics, and composite and hybrid adsorbents. The adsorption mechanisms, such as van der Waals forces, electrostatic interactions, and π–π interactions, contribute to the rapid adsorption kinetics and high adsorption capacity observed in these adsorbents. Full article
(This article belongs to the Special Issue Separation Technology for Resource Utilization and Recovery)
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28 pages, 3716 KB  
Article
Comprehensive Characterization of Aroma-Active Components in Three Grades of Raw Tea Leaves and Their Jasmine Tea Products of Wuyutai Using GC×GC-O-MS and Chemometrics
by Aping Gan, Tingting Zou, Huanlu Song, Shuxin Zhao, Lanlan Zhang and Zejie Ling
Separations 2026, 13(3), 82; https://doi.org/10.3390/separations13030082 - 1 Mar 2026
Cited by 2 | Viewed by 1566
Abstract
This study investigated the aroma characteristics of three grades of raw tea leaves and their corresponding jasmine tea products from Guangxi, China. Aromatic profiles of jasmine tea varieties were analysed using two-dimensional gas chromatography-olfactory-mass spectrometry (GC×GC-O-MS), stir bar sorptive extraction (SBSE), and descriptive [...] Read more.
This study investigated the aroma characteristics of three grades of raw tea leaves and their corresponding jasmine tea products from Guangxi, China. Aromatic profiles of jasmine tea varieties were analysed using two-dimensional gas chromatography-olfactory-mass spectrometry (GC×GC-O-MS), stir bar sorptive extraction (SBSE), and descriptive sensory evaluation. Chemometric methods were applied to compare sensory scores with instrumental data. Volatile compound concentrations and relative odour activity values (r-OAVs) were calculated. The results indicated significant differences in base tea leaf quality: high-grade tea leaf G1 exhibited pure, sweet characteristics, serving as an excellent aroma-absorbing carrier. The scenting process significantly imparted jasmine fragrance to the finished product, although its efficacy was constrained by tea leaf grade. GH1 finished tea exhibited a fresh, vibrant, and rich aroma with a sweet, mellow fragrance and high floral integration. In contrast, GH3, due to its inferior base material quality, yielded a weak aroma after scenting with limited quality improvement. The initial quality of the tea base is the fundamental determinant of the upper limit of the finished jasmine tea’s sensory quality, while the scenting process is the core means of shaping its signature floral aroma. The combination of high-quality tea leaves and precise scenting techniques is essential for developing the fresh, vibrant, and rich flavour profile of premium jasmine tea. This study reveals that the flavour formation of jasmine tea originates from the foundational quality of the tea leaves, providing a theoretical basis for monitoring the aroma quality of jasmine tea produced from different grades of tea leaves. Full article
(This article belongs to the Special Issue Design and Optimization of Extraction/Separation Processes for Natural Products)
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17 pages, 1203 KB  
Article
A Proof-of-Concept Study for the Strong Electrolyte (SE) Switching and the Combined CO2-SE Switching of the Polarity of Tertiary Amine for Lipid Separation Application
by Costas Tsioptsias, Ioannis Maletskos, George Tachias, Thomas Palikrousis, Xanthi Ntampou, Eleni P. Kalogianni and Petros Samaras
Separations 2026, 13(3), 81; https://doi.org/10.3390/separations13030081 - 1 Mar 2026
Cited by 2 | Viewed by 477
Abstract
Tertiary amines such as N,N-dimethyl-cyclohexylamine (DMCHA) are recently explored as candidate solvents for the extraction and separation of lipids from algal biomass. DMCHA exhibits the interesting property of polarity switching which is based on the interaction of DMCHA with CO2, termed [...] Read more.
Tertiary amines such as N,N-dimethyl-cyclohexylamine (DMCHA) are recently explored as candidate solvents for the extraction and separation of lipids from algal biomass. DMCHA exhibits the interesting property of polarity switching which is based on the interaction of DMCHA with CO2, termed CO2 switching. Although this approach exhibits certain advantages, various issues have to be improved to address for example the duration required for process optimization, the energy demand, or the low solvent recovery. The aim of this work is the examination of amine recovery from an oil extract, utilizing strong electrolytes (SE) such as HCl for protonation and NaOH for deprotonation of amine, instead of conventional CO2 switching. It was found that the acid based hydrophobic-to-hydrophilic switching and the alkali based hydrophilic-to-hydrophobic back-switching carried out in the order of few minutes, a considerably shorter time compared to few hours required by gas switching, resulting in addition to higher amine recovery. In addition, the combined CO2 switching with SE-back switching using NaOH proved to be a promising approach for large-scale applications, exhibiting several advantages related to technical, economic, environmental and safety issues. Full article
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17 pages, 5471 KB  
Article
Influence of Anionic Polyacrylamide Molecular Weight on Ultrafine Hematite Flocculation: Mechanistic Insights from Experiments and Molecular Dynamics Simulations
by Shijie Zhou, Qiang Zhao, Zhangke Kang, Jizong Wu, Zhenguo Song, Tao Song, Baoyu Cui and Haoyu Du
Separations 2026, 13(3), 80; https://doi.org/10.3390/separations13030080 - 1 Mar 2026
Cited by 1 | Viewed by 978
Abstract
Ultrafine hematite particles (<10 μm), commonly generated in beneficiation circuits, exhibit poor flocculation and slow settling, posing challenges for solid–liquid separation. This study investigates the influence of the anionic polyacrylamide (APAM) molecular weight on ultrafine hematite flocculation under controlled laboratory conditions, combining macroscopic [...] Read more.
Ultrafine hematite particles (<10 μm), commonly generated in beneficiation circuits, exhibit poor flocculation and slow settling, posing challenges for solid–liquid separation. This study investigates the influence of the anionic polyacrylamide (APAM) molecular weight on ultrafine hematite flocculation under controlled laboratory conditions, combining macroscopic experiments with molecular dynamics simulations (MDSs). Sedimentation tests show that the APAM molecular weight strongly affects settling kinetics, supernatant clarity, and floc structure, with the settling rate, flocculation-stage reaction time, supernatant turbidity, and underflow concentration exhibiting a non-monotonic trend and optimal performance at seven million. Under this condition, particles aggregate most efficiently, achieving a turbidity of 182 NTU, an underflow concentration of 51.5%, and the largest compact flocs, averaging 379.8 μm with a fractal dimension of 1.71. Higher molecular weights (≥9 million) induce chain coiling, reduce floc compactness, increase water retention, and impair settling. MDS indicates that polymer–surface interactions improve with an increasing polymerisation degree only up to an intermediate chain length; a polymerisation degree of 30 exhibits the most favourable extended–flexible conformation, maximal surface enrichment, strongest coordination between carboxyl groups and surface Fe atoms, lowest adsorption energy, and fastest adsorption kinetics. The functional-group distribution and hydrogen-bond analyses show that –NH2 and –COO– groups dominate interfacial interactions, with a polymerisation degree of 30 yielding the highest density of interfacial hydrogen bonds. By correlating macroscopic experiments with molecular-scale observations, this work provides mechanistic insight into how the APAM chain length governs ultrafine hematite flocculation, highlighting the role of polymer conformation and multipoint adsorption in controlling the settling performance. Full article
(This article belongs to the Special Issue Advances in Technologies Used for Mineral Separation)
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16 pages, 3975 KB  
Article
Recovery of Bioactive Extracts from Cistus creticus Using Supercritical CO2
by Maria Chiliou, Vasiliki Louli and Kostis Magoulas
Separations 2026, 13(3), 79; https://doi.org/10.3390/separations13030079 - 28 Feb 2026
Viewed by 814
Abstract
Cistus creticus is a species of the Cistus family that exhibits a wide range of bioactivities; therefore, its oil recovery using a green extraction method is of significant importance for both academic research and industrial applications. Thus, the objective of this work is [...] Read more.
Cistus creticus is a species of the Cistus family that exhibits a wide range of bioactivities; therefore, its oil recovery using a green extraction method is of significant importance for both academic research and industrial applications. Thus, the objective of this work is cistus oil recovery by supercritical fluid extraction (SFE) with CO2. To this end, the effect of various process parameters, namely extraction pressure (110–250 bar), extraction temperature (40–60 °C), and solvent flow rate (1–3 kg/h), on the yield of the process was examined. It was shown that an increase in temperature, and particularly in pressure, positively affects the yield, while the flow rate increase mainly enhances the extraction rate. Hence, the highest yield (8.58% wt) was obtained at 60 °C, 250 bar, and 3 kg/h after 150 min of extraction. Furthermore, the experimental data regarding the kinetics of SFE were correlated successfully by a mass balance model based on Lack’s plug flow model. In addition, the comparison of SFE extracts obtained under intermediate conditions with the essential oil produced by hydrodistillation revealed the extraction of heavier compounds, notably a high content of linoleic acid. Finally, the addition of a small amount of co-solvent (5% wt ethanol) to the SFE process enhanced yield (9.53% wt) as well as antioxidant activity (IC50 = 95.4 mgextract/mL) and total phenolic content of the extract (23.2 mgGAE/gextract). Thus, SFE could become a promising alternative to conventional extraction with ethanol, which exhibited the highest yield (28.5% wt) and a high antioxidant activity (IC50 = 3.2 mgextract/mL), given SFE’s shorter extraction duration. Full article
(This article belongs to the Special Issue Advances in the Analysis of Bioactive Plant Extracts: Separation Techniques and Their Applications)
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14 pages, 3499 KB  
Article
Domination of Tocotrienols in Passifloraceae Species’ Seeds and Recovery Using Ethanolic Extraction
by Danija Lazdiņa, Inga Mišina, Krists Dukurs and Paweł Górnaś
Separations 2026, 13(3), 78; https://doi.org/10.3390/separations13030078 - 27 Feb 2026
Cited by 1 | Viewed by 689
Abstract
Current industrial sources of tocotrienols are almost entirely composed of tropical monocots. However, recent reports have observed significant tocotrienol (T3) contents in eudicot families, including Passifloraceae. While passion fruits are also tropical, their cultivation is not strictly limited to rainforests, and seeds are [...] Read more.
Current industrial sources of tocotrienols are almost entirely composed of tropical monocots. However, recent reports have observed significant tocotrienol (T3) contents in eudicot families, including Passifloraceae. While passion fruits are also tropical, their cultivation is not strictly limited to rainforests, and seeds are often a by-product of fruit processing. To elucidate tocochromanol production in the Passifloraceae family, seeds (54 samples representing 18 species) were gathered from botanical gardens worldwide. Ultrasound-assisted extraction in ethanol (UAEE) was compared with the standard saponification protocol as a greener alternative. Tocotrienols constituted a major percentage (48–91%) of Passifloraceae species’ seed tocochromanols, and γ-T3 (12–53%) and δ-T3 (8–68%) were major contributors. Although a higher δ-T3 content was observed in some Passiflora species, it was less consistent than the γ-T3 content between and within species. The highest total tocochromanol content was observed in P. subpeltata (28.98 ± 5.83 mg 100 g−1 dry weight). The UAEE protocol recovered tocotrienols and tocopherols at degrees similar to those of saponification (100% and 93%, respectively). Therefore, UAEE could also be proposed for the effective recovery of these valuable phytochemicals from by-products of Passiflora fruits. Full article
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19 pages, 4214 KB  
Article
Highly Acidic Macro-Porous Cation Exchange Resin D001 for Efficient Separation of Co(II) from Nd(III) and Dy(III) During Rare Earth Recycling
by Yao Li, Huilin An, Zezuo Jiang, Haixiang Tan and Chunlin He
Separations 2026, 13(3), 77; https://doi.org/10.3390/separations13030077 - 27 Feb 2026
Viewed by 1607
Abstract
Addressing the need for efficient separation of critical elements from NdFeB magnets, this study introduces, for the first time, a D001 cation exchange resin for the selective separation Co(II) from Nd(III) and Dy(III). At pH 5, the resin adsorbs Nd and Dy with [...] Read more.
Addressing the need for efficient separation of critical elements from NdFeB magnets, this study introduces, for the first time, a D001 cation exchange resin for the selective separation Co(II) from Nd(III) and Dy(III). At pH 5, the resin adsorbs Nd and Dy with high capacities (97.57 and 86.38 mg/g, respectively) and efficiencies (over 98%), but shows low affinity for Co (26.6% efficiency). The resin exhibits excellent stability across a wide pH range of 2–7 and maintains high adsorption performance over five consecutive cycles. The process follows pseudo-second-order kinetics and the Langmuir model. Co(II) is effectively desorbed with high purity (>99%) using 2.5 M H2SO4. Characterization confirms that adsorption occurs via ion exchange on –SO3Na groups. This method successfully separates Co, providing a high-purity stream for further rare earth purification and demonstrating strong industrial potential. Full article
(This article belongs to the Section Separation Engineering)
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20 pages, 4686 KB  
Article
Response Surface Methodology-Optimized QuEChERS Combined with Liquid Chromatography–Quadrupole-Time-of-Flight Mass Spectrometry for Simultaneous Screening of Pesticides and Mycotoxins in Astragalus
by Hang Yin, Yanlong Chen, Yingchun Wang, Zhihong Shi, Xueyan Hu and Hongyi Zhang
Separations 2026, 13(3), 76; https://doi.org/10.3390/separations13030076 - 25 Feb 2026
Viewed by 927
Abstract
This study used the QuEChERS method in combination with liquid chromatography–quadrupole-time-of-flight mass spectrometry (LC-Q-TOF/MS) to develop a method for simultaneous detection of 187 pesticides and 10 mycotoxins in Astragalus. The samples were extracted using an acetonitrile–water solution containing 5% formic acid, and the [...] Read more.
This study used the QuEChERS method in combination with liquid chromatography–quadrupole-time-of-flight mass spectrometry (LC-Q-TOF/MS) to develop a method for simultaneous detection of 187 pesticides and 10 mycotoxins in Astragalus. The samples were extracted using an acetonitrile–water solution containing 5% formic acid, and the amount of purification materials was optimized through response surface methodology. The results show that 197 compounds exhibit good linear relationships within their respective linear ranges (R2 > 0.995). The screening detection limits (SDLs) and the limits of quantification (LOQs) ranged from 0.001 to 0.02 mg/kg and 0.002 to 0.02 mg/kg, respectively. At the spiked levels of 1, 2, and 10 times LOQ, compound recoveries ranged from 61.5% to 118.9%, 67.1% to 119.6%, and 72.0% to 119.3%, respectively, with relative standard deviations (RSDs) all less than 20.0%. The intra-day precision and inter-day precision are less than 10% and 20%, respectively. This method was applied to detect 20 batches of commercially available Astragalus samples. Six compounds (three pesticides and three mycotoxins) were detected; the residues of aflatoxin and ochratoxin A in two batches exceeded the maximum residue limits and required attention. The established method is simple, rapid, and highly sensitive. It is also reproducible and meets the requirements for the accurate quantitative analysis of multiple pesticide residues and mycotoxins in Astragalus. Full article
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