Separations doi: 10.3390/separations13100283

Authors: Ruirui Li Ruiliang Zhu Subhan Mahmood Tenghe Zhang Shun Yao

Periplaneta americana (American cockroach) is a traditional medicinal insect rich in bioactive peptides and amino acids, yet its efficient and green extraction remains challenging due to its complex matrix and the thermolabile nature of its active components. This study developed a novel pressurized deep eutectic solvent (DES) extraction method using a “sandwich” system with a phase-switchable feature for the efficient enrichment of total amino acids and peptides from P. americana. A choline chloride-phenylacetic acid (ChCl-PA, 1:2 molar ratio) DES was selected for its suitable melting point (~25 °C), strong intermolecular interactions with the targets, and ease of recovery via phase switching. The extraction was performed in a stainless-steel mold under mild conditions under 8 MPa for 2 h without extra liquid organic solvents. Key parameters including solid-to-solid ratio, pressure, temperature, and time were systematically optimized, achieving a maximum total yield of 120.2 mg/g, higher than conventional stirring, ultrasound-assisted, microwave-assisted, or ethanol reflux extraction. The kinetic study showed that the extraction process of the experimental method could be better described by the pseudo-second-order kinetic model (R2 = 0.9791). The fitting trend of the experimental data generally conformed to the mass transfer behavior similar to chemical adsorption. Theoretically, it is speculated that potential intermolecular interactions including electrostatic attraction, π-π stacking and ion exchange may occur between DES and target components. The DES could be efficiently recovered (>86% recovery) and reused for at least four cycles with acceptable performance. Scanning electron microscopy confirmed pronounced structural disruption of insect powders after extraction, facilitating target release. Greenness assessment using ComplexGAPI and AGREE tools validated the method’s environmental friendliness, with minimal solvent consumption, low energy input, and reduced hazardous waste. Overall, this pressurized DES strategy provides a simple, economical and sustainable laboratory-scale alternative for the extraction of thermosensitive bioactive components from soft biomaterials. It has certain reference significance in laboratory-scale analysis pretreatment and future amplification research in natural product research.

Separations doi: 10.3390/separations13100282

Authors: Junhong Wu Peng Gao Yanyu Huang Yujin Peng Anlin Liu Liang Ma

Accurately quantifying and reducing the carbon footprint of the sulfur recovery unit (SRU) tail gas treatment process is crucial for pollution and carbon reduction in the chemical industry. This study employed Aspen Plus to simulate the N-methyldiethanolamine (MDEA)-based SRU tail gas treatment process at a sulfur production plant in Shandong, China. A carbon footprint of a product (CFP) method based on life cycle assessment was used to calculate the cradle-to-gate carbon footprint of the SRU tail gas treatment process. The results demonstrate that the carbon footprint of treating 1 Nm3 pretreated SRU tail gas (CFPTG) is 0.495 kgCO2e/Nm3, with gas treatment and steam contributing 99.9% and 98.8%, respectively. The data quality indicator—Monte Carlo simulation uncertainty analysis indicates that the relative standard deviation of CFPTG is 7.4%. Furthermore, 16 emission mitigation pathways were established, focusing on energy supply. Biomass boilers reduce CFPTG by 92.6%, whereas electric boilers increase it by 45.2% under the current power mix. Electricity substitution alone reduces emissions by only 0.1–0.4%, while boiler electrification coupled with low-carbon electricity achieves 85.1–96.5% reduction. This study quantifies the life cycle carbon footprints of the MDEA-based SRU tail gas treatment process, providing a scientific basis for low-carbon transformation in tail gas treatment.

Separations doi: 10.3390/separations13100281

Authors: S’busiso M. Nkosi Precious N. Mahlambi

Pharmaceuticals have been the focus of research into South Africa’s water resources for the past ten years and more. Five pharmaceutical residues were examined in this investigation in plant, sediment, and river water samples from Durban, SA. Fenoprofen, diclofenac, naproxen, gemfibrozil, and ibuprofen were the compounds of interest; they are some of the most widely used and often prescribed medications globally. Compound concentrations found in sediments and river water ranged from 0.2 to 12.0 ng g−1 and 0.2 to 5.1 µg L−1, respectively. Different plant parts (roots, stems, and leaves) had varying quantities of the target compounds in the Stevia rebaudiana species. The most prevalent drug in Stevia rebaudiana was ibuprofen, which was discovered in roots at the highest concentration of 7.2 ng g−1. Although there was no apparent trend in the amounts identified in different areas of Stevia rebaudiana in this preliminary analysis, it is hypothesized that these pharmaceuticals penetrate into the aquatic plant roots from water and then move into the stem and leaves. The partitioning coefficients (L kg−1) varied from one sampling location to another; fenoprofen, diclofenac, naproxen, gemfibrozil, and ibuprofen and diclofenac ranged from 0.1 to 4.0, 0.9 to 6.8, 0.8 to 3.7, 0.2 to 8.5, and 0.6 to 5.6, respectively. This suggests that environmental factors, including climate and the existence of additional pollutants from water, as well as variations in physicochemical properties, may have an impact on the fates of these pharmaceuticals. Overall, it was found that the target compounds were present in river water, sediments, and Stevia rebaudiana. This suggests that Stevia rebaudiana may reduce water pollution by absorbing pharmaceuticals through its roots.

Separations doi: 10.3390/separations13100280

Authors: Keyla Nunes Farias Gomes João Claudio Vitoria Ático Leite Leonardo da Silva Rangel Isabelle Soares Ricardo Diego Galhardo de Albuquerque José Augusto Albuquerque dos Santos Robson Xavier Faria

Schistosomiasis remains a critically neglected tropical disease, and its control relies on the suppression of vector snails of the genus Biomphalaria. The extensive use of niclosamide is limited by its high cost, poor water solubility, and ecotoxicity. In this study, the molluskicidal, ovicidal, ecotoxicological, and biosafety properties of fractions obtained from the ethanolic seed extract of Abelmoschus esculentus were evaluated. Soxhlet extraction and liquid–liquid partitioning yielded five fractions of increasing polarity. LC–QTOF–MS analysis of the active fractions: crude ethanolic extract in ethyl acetate, crude ethanolic extract in acetone, and crude ethanolic extract in ethanol revealed bioactive polyphenols, including glycosylated flavonols, astilbin, catechin/epicatechin, procyanidin dimers, and protocatechuic acid. The ethyl acetate fraction showed the highest molluskicidal activity against adult Biomphalaria glabrata (48 h LC50 = 41.76 mg/L; LC90 = 61.25 mg/L), while crude ethanolic extract in acetone and crude ethanolic extract in ethanol also met the World Health Organization (WHO) efficacy threshold (LC90 < 100 mg/L). Strong ovicidal activity was observed, particularly for the crude ethanolic extract in ethanol (LC50 = 37.82 mg/L) and crude ethanolic extract in ethyl acetate (LC50 = 40.56 mg/L) fractions. The crude ethanolic extract in ethanol and crude ethanolic extract in dichloromethane fractions caused no mortality in Physella acuta or Biomphalaria tenagophila. Biosafety assays demonstrated low cytotoxicity, minimal hemolysis, and no acute toxicity in mice. These findings highlight A. esculentus seed fractions, especially crude ethanolic extract in ethyl acetate, as promising, biodegradable botanical molluskicides for schistosomiasis control.

Separations doi: 10.3390/separations13100279

Authors: Hanyue Ma Zhennan Wu Luyu Zhang Yan Zhou Yan Wu Yuezhou Wei

Cesium and strontium (Cs/Sr) are key radionuclides in radioactive wastewater. Dynamic fixed-bed adsorption is a practical approach for Cs/Sr removal, but engineering-scale design remains challenging because laboratory-derived breakthrough models have rarely been validated against independent pilot-scale data. Here, a mechanistic framework was developed and independently validated for a layered column containing silica-supported ammonium molybdophosphate (AMP/SiO2) and silica-supported potassium hexatitanate (K2Ti6O13/SiO2) as Cs- and Sr-selective beds. An axial-dispersion model with material-specific equilibrium relations and an effective liquid-concentration driving-force coefficient was calibrated solely against laboratory breakthrough curves. The resulting parameters were transferred without refitting to a pilot-scale column operated with a seawater-like feed, representing a 1500-fold increase in adsorbent mass. Laboratory calculations yielded R2 values of 0.997 for Cs and 0.998 for Sr. The pilot calculation reproduced the Sr curve with R2 = 0.974 and RMSE = 0.068; the predicted 5% breakthrough volume (V5) differed from experiment by 3.6%. Propagated V5 uncertainty limits were ≤9.3% for Cs and Sr. Cs remained below 5% breakthrough through 44.2 L. Sensitivity analysis identified equilibrium capacity and feed concentration as the principal controls on breakthrough bed volumes; geometry and transport affected bed utilization and front width. These results support model-based scale-up under the tested conditions.

Separations doi: 10.3390/separations13100278

Authors: Zixuan Yang Zurong Yi Libing Zhao Mingmei Li Jindong Han Bin Guo Ming Han Wantao Li Youbang Lai Chuntao Wu Xiaofei Guo Fengliang Liu

Biotite in mica-bearing phosphate ores is prone to sliming and forms fine intergrowths with apatite, impairing flotation selectivity. Taurine, sodium lignosulfonate, chitosan, hydroxypropyl distarch phosphate, and carboxymethyl chitosan (CMCS) were screened by single-mineral and artificial-mixture flotation tests. Contact angle, adsorption, zeta potential, FTIR, and XPS analyses focused on the −0.023 mm fraction. At pH 9 and a collector dosage of 268 mg/L, CMCS retained selectivity in favor of apatite. In single-mineral tests, CMCS dosages of 30, 60, and 150 mg/L produced apatite–biotite recovery differences of 47.57, 40.51, and 20.59 percentage points for the +0.074, −0.074 + 0.023, and −0.023 mm fractions, respectively. In artificial-mixture tests, selected dosages of 20, 120, and 180 mg/L yielded P2O5 recoveries of 95.50%, 95.58%, and 74.37% and grades of 28.02%, 26.47%, and 21.10%, respectively. As particle size decreased, the required CMCS dosage increased and separation deteriorated. Contact-angle measurements showed that CMCS pretreatment preserved the strong collector-induced hydrophobicity of apatite while slightly weakening that of biotite, thereby increasing the wettability contrast between the two minerals. Biotite showed a larger negative zeta-potential shift and greater CMCS adsorption than apatite; at 180 mg/L, the adsorption amounts were 1.17 and 0.76 mg/g, respectively. Together with the adsorption results, FTIR and XPS suggested stronger CMCS–biotite interfacial interactions involving carboxyl and hydroxyl-containing groups, with possible participation of Mg-related surface sites. These findings demonstrate the particle-size dependence of CMCS-assisted apatite-biotite flotation and reveal preferential CMCS interaction with biotite under fine-particle conditions.

Separations doi: 10.3390/separations13100277

Authors: Qiansheng Liu Zhiqiang Hu Ming Li Xichang Shi

Manganese-based lithium ion-sieves (LIS) are promising adsorbents for lithium extraction from salt lake brines. Their powder form, however, hinders industrial application because it disperses poorly, is difficult to recover, and causes excessive pressure drop in fixed-bed columns. Here we address this powder-forming challenge through porous spherical granulation, using solid paraffin as a mesoporous porogen. Co-doped precursors were prepared by hydrothermal calcination. XPS showed that Co doping raised the Mn4+ ratio from 65.77% to 72.16%, which suppresses the Jahn-Teller effect. The optimal powder reached 33.36 mg/g in LiCl solution and retained 89.0% of this capacity after five cycles. For granulation, the powder was modified with octadecyltrimethoxysilane (OTMS) and granulated by suspension polymerization. The solid paraffin porogen created mesoporous channels that increased the BET surface area from 0.82 to 82.00 m2/g. The optimized granule reached 4.42 mg/g in LiCl solution and 1.56 mg/g in real salt lake brine, with separation factors of 357.0, 256.5, 225.4, and 41.87 for Na+, K+, Mg2+, and Ca2+, respectively. It kept 62% of its capacity after 20 cycles, and Mn dissolution stabilized at 0.18%. The combined doping and pore-engineering strategy offers a viable route to lithium extraction from salt lake brines.

Separations doi: 10.3390/separations13100276

Authors: Qingyang Liu Xuekui Qi

Short-chain per- and polyfluoroalkyl substances (PFAS) have emerged as a challenging issue in water remediation due to their strong hydrophilicity and small molecular dynamic dimensions. Most current studies on biochar-based PFAS removal treat short-chain PFAS as secondary issues related to long-chain congeners. These technologies often apply classical theoretical frameworks, including hydrophobic interactions, electrostatic attraction, and conventional micropore filling, to explain mechanisms and develop functional materials. However, recent experimental evidence suggests that the dominant adsorption behavior of short-chain PFAS at biochar interfaces differs substantially from that of long-chain PFAS. First, the key capture process for short-chain PFAS appears to occur within sub-nanoporous domains with sizes between 0.56 and 0.85 nm, rather than within the broad microporous structures traditionally assumed. In addition, design principles based on synergistic pore–surface chemistry for long-chain PFAS may cause irreversible damage to sub-nanopores through metal-loading modifications, potentially reducing short-chain PFAS adsorption performance. Finally, material regeneration and disposal strategies for short-chain PFAS may need to shift from passive physical adsorption toward integrated adsorption–degradation systems. The main contribution of this perspective is to propose an independent mechanistic and material design framework for short-chain PFAS removal, based on the possible synergy between sub-nanopores and surface basic sites, and to outline a transition from passive adsorption to integrated adsorption–degradation. Future breakthroughs may depend less on pursuing ultra-high adsorption capacities alone and more on the precise, synergistic control of pore structure and surface chemistry, enabling combined adsorptive enrichment and in situ degradation.

Separations doi: 10.3390/separations13100275

Authors: Małgorzata Janicka Irena Malinowska

Liquid chromatography techniques used to investigate the biological properties of substances are described. The focus was on systems that mimic the environment in which the drug acts, i.e., biomimetic systems such as RP-LC with a non-polar stationary phase mimicking the interior of biological membranes, systems with phases mimicking cell membranes like the IAM-type stationary phases, micellar systems in which both the stationary and mobile phases mimic cell membranes; and systems in which the stationary phases consist of immobilised proteins. The paper discusses the chromatographic parameters used to assess the biological activity of substances, as well as the role of computational methods and statistical tools used in the analysis of chromatographic data and in the development of models to predict the biological activity of substances. The significant role of chromatography (in particular thin-layer chromatography) with biological detection in the study of the microbiological, microbiochemical and enzymatic activity of components of natural mixtures was also demonstrated.

Separations doi: 10.3390/separations13100274

Authors: Daniela D. Pereira Cleusa F. Zanchin Lara D. D. Santana Diogo Marchesan Osmar D. Prestes Renato Zanella

The use of herbicides to control weeds in crops, especially in soybeans, corn, and sugarcane, is a common practice, but it poses a risk to nearby sensitive crops, since herbicide drift is common and has caused phytotoxicity, resulting in reduced crop yield. Thus, the determination of acid herbicides in plant leaves is important but challenging due to the complexity of the matrix and compound characteristics. Considering this, an analytical method was developed and validated for the determination of 22 acid herbicides in plant leaves, using a modified QuEChERS procedure and ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) with a run time of 10 min. The optimized method involved the extraction of the hydrated sample with acetonitrile containing formic acid, partitioning with salts, and cleanup with graphitized carbon black. Validation presented recoveries from 71 to 118%, with RSD ≤ 19% and method limit of quantification of 5 µg kg−1 for most of the herbicides indicating satisfactory performance. The proposed method was applied to 50 plant leaf samples, 36 of which contained residues of at least one of the evaluated herbicides. The developed method is rapid and efficient and can be applied in routine analyses of acid herbicides in plant leaves.

Separations doi: 10.3390/separations13100273

Authors: Anahí López-Martínez Kevin Alejandro Avilés-Betanzos Juan Cauich-Rodríguez Georgina Sandoval Manuel Octavio Ramírez-Sucre Ingrid Mayanin Rodríguez-Buenfil

Natural deep eutectic solvents (NADES) have been increasingly explored as alternative extraction media for recovering high-value phytochemicals from agro-industrial byproducts. In this study, a 5 × 22 factorial design was used to evaluate the influence of HBD type, molar ratio, and added water content for choline chloride-based NADES-UAE of neohesperidin from Citrus aurantium byproducts. Individual flavonoids were quantified by Ultrahigh-Performance Liquid Chromatograph (UPLC), while total polyphenolic content (TPC), total flavonoid content (TFC), vitamin C content (TAA), and antioxidant activity (AX) were determined by spectrophotometric assays. The highest extracted neohesperidin content, 995.98 ± 1.77 mg/100 g dry mass (DM), was achieved with lysine-based (HBD) NADES (1:2 mol/mol, 40% w/w). In addition, the flavonoid profile was dominated by hesperidin, quercetin + luteolin and diosmetin. Among the NADES formulations evaluated, the highest TPC and TFC with a fructose-based (HBD) concentration of 4436.03 ± 94.31 mg GAE/100 g DM (1:1 mol/mol, 40% w/w) and 1514.64 ± 53.11 mg QE/100 g DM (1:1 mol/mol, 60% w/w), respectively; for TAA, 2467.39 ± 52.18 mg AAE/100 g DM with citric acid (HBD); and finally for AX, 91.71 ± 0.86% was obtained by fructose (HBD) both with 1:2 mol/mol, 60% w/w. Changes in the NADES composition also altered the extraction of other flavonoids, generating distinct phytochemical profiles. Statistical analyses demonstrated that the solvent composition significantly affected the extraction selectivity and the resulting phytochemical profile. Overall, the fructose-based NADES provided one of the most effective systems for recovering bioactive compounds from Citrus aurantium byproducts, supporting the potential of NADES-UAE as an alternative extraction strategy for obtaining flavonoid-enriched extracts with potential relevance for future food, nutraceutical, and pharmaceutical applications.

Separations doi: 10.3390/separations13100272

Authors: Mohammed B. Alamari Fatimah A. Almulhim Ali Laksaci

Mango fruit is widely recognized for its substantial nutritional value and its contribution to a balanced diet. It is an excellent source of vitamin C, vitamin A, and dietary fiber that facilitates digestive function. This fruit also provides many important minerals, including potassium and magnesium, and it is rich in bioactive compounds, particularly polyphenols. It is an important tropical fruit crop widely cultivated in Saudi Arabia, especially in the southwestern regions, where climatic conditions are favorable for its production. In this paper, we propose novel techniques for analyzing the nutritional composition and quality attributes of mango. The approach integrates spectroscopic techniques with advanced statistical modeling to evaluate and predict the quality attributes of mango. Specifically, we employ some functional regression methods, including least squares relative error regression(LSRE), least absolute relative error regression (LARE), and functional least absolute deviations regression (FLAD), to predict important indicators such as vitamin C content, soluble solids content (SSC), and total acidity (TA). The results demonstrate that these functional approaches outperform conventional methods, such as partial least squares regression (PLSR) and principal component regression (PCR), in terms of predictive accuracy. Furthermore, the proposed models exhibit strong robustness, which maintains reliable performance under heterogeneous and non-normal data conditions, highlighting their suitability for practical applications in fruit quality assessment.

Separations doi: 10.3390/separations13100271

Authors: Xin Lu Jingjing Wang Kaige Shi Shuaijun Han Qingcong Wei Bei Kang Bing Liu Yanmin Chen Mengtao Song

A novel amidoxime-functionalized carbon fiber adsorbent (CFAO) was successfully fabricated via surface grafting modification for U(VI) removal. The sorption behaviors of the CFAO were systematically explored under various experimental conditions involving solution pH, contact time, initial U(VI) concentration, temperature, and complex competing ion environments. With a fixed adsorbent dosage of 10 mg in 30 mL solution, the maximum experimental equilibrium adsorption capacity was 56.25 mg/g at an initial U(VI) concentration of 60 mg/L, with sufficient contact time to attain full adsorption equilibrium. The Langmuir model yielded a theoretical saturated adsorption capacity of 63.78 mg/g. The adsorption process was well described by the pseudo-second-order kinetic and Langmuir isotherm models, while thermodynamic results confirmed the spontaneous and endothermic nature of U(VI) sorption. Benefiting from grafted amidoxime chelating groups, CFAO exhibited significantly improved uranium uptake compared with pristine carbon fibers. The material presented selectivity toward U(VI) in simulated seawater and nuclear wastewater, and retained over 90% of its original capacity after five adsorption–desorption cycles. With good recyclability and U(VI) selectivity, as reflected by the retained adsorption performance upon cycling, CFAO shows potential as a reusable adsorbent for U(VI) recovery from complex aqueous systems under laboratory batch conditions.

Separations doi: 10.3390/separations13100270

Authors: Huadong Zhu Hao Wang Chengqian Zhang Chenxin Lyu Baocai Zhang Peng Zhao

Label-free and non-contact manipulation methods capable of actively regulating particle trajectories are important for particle handling, selective separation, and targeted collection. However, conventional magnetic-levitation approaches primarily rely on passive equilibrium positioning and provide limited capability for actively transporting particles to prescribed locations. Here, we propose a position-amplified active MagLev method that uses a moving magnetic field as a controllable non-contact actuator for particle manipulation, separation, and targeted placement. A magneto-manipulation model incorporating gravity, buoyancy, magnetic force, and hydrodynamic drag is established to predict particle trajectories and the final center distance, enabling parameter optimization. For particles of the same density with diameters of 3, 4, and 5 mm, the predicted horizontal center-to-center distances between the 3 and 4 mm particles and between the 4 and 5 mm particles are 13.16 and 3.40 mm, respectively, closely matching experimental values of 12.46 and 3.56 mm (deviations of 0.70 and 0.16 mm, respectively). The three particles form a size-ordered spatial distribution and are successfully directed into separate collection troughs. Vertically, increasing magnet spacing enhances vertical density sensitivity and enlarges inter-material distances; for TPEE, PA66, and PC/ABS, the vertical distance between PA66 and TPEE increases from 3.99 mm to 5.70 mm, and that between PA66 and PC/ABS increases from 3.08 mm to 3.99 mm, with all three guided into distinct troughs. These results demonstrate that the proposed method extends MagLev from passive equilibrium positioning to an active, model-guided manipulation platform in which particle-property differences are converted into predictable spatial responses and subsequently exploited for targeted collection. The method therefore integrates non-contact transport, positional separation, sensitivity tuning, and prescribed particle placement within a single magnetic-manipulation process.

Separations doi: 10.3390/separations13100269

Authors: Athanasia K. Tolkou Nikoletta A. Kasviki Anastasios I. Zouboulis

Metal–Organic Frameworks (MOFs) have emerged as promising materials for the removal of pharmaceutical contaminants, including antibiotics and endocrine-disrupting compounds (EDCs), from contaminated water due to their high surface areas, tunable porosity, and versatile chemical functionalities. This review provides a comprehensive and critical assessment of MOF-based approaches for the adsorptive removal of pharmaceutical contaminants, including tetracyclines, sulfonamides, fluoroquinolones, non-steroidal anti-inflammatory drugs (NSAIDs), antidepressants, and EDCs. Particular emphasis is placed on the relationship between MOF characteristics and adsorption performance, including adsorption capacity and specific surface area, as well as on the adsorption isotherm, kinetic, and thermodynamic models used to elucidate adsorption behavior and mechanisms. A distinctive aspect of this review is the integrated evaluation of regeneration and reusability, including regeneration strategies, agents, adsorption–desorption cycles, and their effects on adsorption performance and material stability. Furthermore, FTIR-based evidence is critically examined to identify possible MOF–pharmaceutical interactions by comparing pristine and contaminant-loaded materials. The role of MOF composites and selected catalytic processes as complementary approaches to pharmaceutical removal is also discussed. Finally, challenges related to MOF production cost, metal toxicity, structural stability, scalability, regeneration efficiency, and application under realistic wastewater conditions are evaluated. By integrating adsorption performance, modeling, thermodynamics, regeneration, reusability, and spectroscopic evidence, this review provides a comprehensive and practically oriented perspective on the development of MOF-based technologies for pharmaceutical-contaminated water treatment.

Separations doi: 10.3390/separations13090268

Authors: Bingyue Zhang Qingzhao Wan Huiling Zhang Yaqi Wang

Steam explosion-assisted vacuum extraction (SVE), an integrated extraction strategy, was developed to improve the yields of bioactive constituents from Perilla frutescens and to explore the potential mechanisms responsible for the observed performance enhancement. Compared with conventional Reflux extraction (RE), extracts obtained using the integrated SVE process contained higher abundances of major bioactive compounds. The contents of ferulic acid, scutellarin, and rosmarinic acid extracted from P. frutescens leaves rose from 3.126 to 4.025 mg per g of dried leaves (increased 1.29-fold), 0.236 to 0.536 mg/g (increased 2.27-fold), and 0.614 to 2.386 mg/g (increased 3.89-fold), respectively, while the total content of the four quantified bioactive compounds rose from 4.574 to 7.521 mg/g (increased 1.64-fold). Scanning electron microscopy revealed that SVE-treated samples exhibited microstructural alterations characterized by greater surface roughness and visible pore formation, which may enhance solvent accessibility and facilitate mass transfer. Metabolomic profiling further indicated higher levels of hydroxycinnamic acids, flavonoid glycosides, fatty acids, and triterpenoids in SVE-processed samples, reflecting compositional changes in P. frutescens extracts. These favorable changes may be partly attributed to the combined effects of structural modification induced during SVE pretreatment and low-temperature vacuum extraction; such combined effects may facilitate mass transfer and mitigate thermal degradation of heat-sensitive constituents. Overall, this study provides preliminary insights into the possible mechanisms underlying this integrated extraction strategy and may support the development of efficient extraction approaches for P. frutescens.

Separations doi: 10.3390/separations13090267

Authors: Christian Larenas Jonathan Chauca Edison Osorio Marjourie Yanez Paco Noriega

Ilex guayusa Loes., known as guayusa, is a plant that has been used for generations by the indigenous peoples of the Ecuadorian Amazon for its medicinal properties, notably its stimulating effects. This bioactivity is primarily due to the presence of xanthine alkaloids such as caffeine, theobromine, and theophylline. In this study, the concentration of each alkaloid was determined in thirty populations throughout the Amazon region, with data ranging from 2065.0 mg/100 g to 364.8 mg/100 g for caffeine; 225.8 mg/100 g and 74.6 mg/100 g for theobromine; and 4.9 mg/100 g and 1.5 mg/100 g for theophylline. A statistical analysis was conducted on twenty-four guayusa populations by integrating alkaloid concentrations with altitude, climatic, and soil variables. Caffeine showed high variability among populations and was only weakly associated with elevation, whereas theobromine and theophylline were determined primarily by climatic and soil factors. These results indicate that methylxanthine accumulation in Ilex guayusa is driven by the combined influence of climatic and edaphic conditions rather than by a single environmental factor.

Separations doi: 10.3390/separations13090266

Authors: Yuqiang Sheng Yongzhen Zhang Shujiang Liu Zhanying Chen Di Liu Shilian Wang

To address the challenge of identifying the true structure–performance relationship governing xenon adsorption in silver-exchanged zeolites, a series of Ag/13X adsorbents with tunable silver loadings were synthesized via liquid-phase ion exchange. The unique FAU-type topology of 13X zeolite, composed of spacious supercages interconnected by large 12-membered-ring windows, enables high silver dispersion while minimizing diffusion limitations. This unique structural advantage makes Ag/13X an ideal model system for investigating the intrinsic role of silver active sites in Xe adsorption. We identify a pronounced volcano-shaped dependence of Xe adsorption on silver loading, establishing that total silver content is not the governing factor for Xe capture. Combined structural characterization and spectroscopic analyses reveal that increasing silver loading continuously alters silver speciation from highly dispersed Ag+ ions toward more aggregated silver species, which may reduce the fraction of accessible Ag+-related adsorption sites and simultaneously modify the local electronic environment of silver species. At an optimal AgNO3 exchange concentration of 0.5 M, the predominance of well-dispersed Ag+ species maximizes accessible active-site density and leads to the highest Xe uptake. Charge-corrected GCMC simulations provide molecular-level validation by showing that these accessible Ag+ sites reinforce Xe adsorption through stronger ion-induced dipole interactions. Consequently, this work identifies the density of accessible Ag+ sites as an important descriptor for Xe capture, offering a design guideline for engineering high-efficiency noble-gas adsorbents.

Separations doi: 10.3390/separations13090265

Authors: Montaha Mt. Miratun Ah-Reum Han Chang Hyun Jin Euna Choi Ha-Yeon Song Trung Huy Ngo Kyu Joon Lee Hyukjae Choi Joo-Won Nam Eui-Baek Byun

Naringenin is a flavanone recognized for its diverse pharmacological properties, including anti-inflammatory and anticancer effects. This study aimed to produce novel structures with enhanced biological activity by subjecting (±)-naringenin (1) to γ-irradiation. Compound 1 in an ethanol solution was irradiated at doses of 30, 50, 70, and 100 kGy, among which the 100 kGy dose yielded the highest concentration of radiolysis products. These radiolysis products were further processed through multi-step semi-preparative HPLC utilizing a chiral column, yielding compounds 2–5. These compounds were identified as apigenin (2) and three stereoisomers of 2-(1-hydroxyethyl)-naringenin (2,3-dihydro-5,7-dihydroxy-2-(1-hydroxyethyl)-2-phenyl-4H-1-benzopyran-4-one; 3–5) via high-resolution electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. The absolute stereochemistry of compounds 3–5 was determined to be (2S,11S)-, (2S,11R)-, and (2R,11S)-configurations, respectively, by comparing experimental electronic circular dichroism data and specific optical rotations. Evaluation of nitric oxide inhibition in lipopolysaccharide-stimulated RAW 264.7 cells revealed that compound 2 exhibited greater activity to the parent compound 1, whereas derivatives 3‒5 were inactive. These findings indicate that γ-irradiation is an effective strategy for structural modification and enhancing the bioactivity in flavonoids.

Separations doi: 10.3390/separations13090264

Authors: Jan Kuhnholz Albert Beyer Martina Balazinski Anja Noke Katja Zocher

Phycocyanin as water-soluble, accessory pigment is commonly extracted from Limnospira platensis (L. platensis). The pigment is often used as natural food colourant and is a potential antioxidant. Usually, the pigment is extracted with several freeze–thawing cycles with subsequent purification steps. The cell disintegration with physical plasma (here spark discharges) is already described for microalgae and was tested for the extraction of phycocyanin from L. platensis. Moreover, calcium chloride was examined as a non-toxic and inexpensive precipitator in the purification step. Samples were treated with water as solvent alone or precipitated with calcium chloride. Also, samples were divided for immediate analysis after extraction and 24 h incubation after the respective cell wall rupture method with subsequent analysis. The extracts were tested for C-phycocyanin (C-PC) concentration, content, selectivity, and radical scavenging activity. Spark discharges were administered with 4 Hz, 100 ns high-voltage pulses of 35 kV, resulting in a pulse energy of ca. 0.2 J/pulse. For freeze–thawing, a maximum yield of 2.75 mg/mL was obtained, for spark discharges, max. 0.24 mg/mL. However, despite a lower concentration, a remarkable purity was found for plasma-treated samples. In addition, radical scavenging activity was not influenced by the spark discharge exposure.

Separations doi: 10.3390/separations13090263

Authors: Zhiyuan Sun Zhongjun Zhou Tianyang Sun Shiyu Wang Kaile Xiao

Coal and gangue separation is crucial for clean and efficient coal utilization. However, practical sorting environments are highly unstructured, where irregular fragments exhibit random distribution, varying orientations, and occlusion. Conventional 2D vision methods cannot provide the 3D geometric information required for intelligent sorting, while model-based 6D pose estimation is unsuitable for coal gangue fragments due to their irregular morphology and lack of predefined models. This study proposes an RGB-D cascaded fusion framework for partial point cloud-based 3D geometric estimation. The framework follows a detection–segmentation–reconstruction pipeline, where object detection provides semantic priors, zero-shot segmentation generates pixel-level masks, and the masks guide depth extraction and local point cloud reconstruction. Based on the reconstructed point clouds, task-oriented geometric parameters, including centroid position, oriented bounding box dimensions, visible volume, and principal orientation, are estimated for intelligent separation. Experiments on a dedicated RGB-D coal and gangue dataset demonstrate that the proposed method achieves a centroid localization error of 14.22 mm, dimension error of 9.34%, and volume error of 11.3%. Compared with detection-box-based depth reconstruction, the proposed semantic-guided strategy significantly improves geometric estimation accuracy. The proposed framework provides reliable 3D perception for intelligent coal gangue separation and robotic sorting.

Separations doi: 10.3390/separations13090262

Authors: Yu-Ting Huang Ming-Cheng Shih

This study explores the adsorption performance of clean peanut husk (CPH) as a sustainable and low-cost biosorbent for removing methylene blue (MB) from aqueous solutions. Batch experiments investigated the effects of dye concentration, biosorbent dosage, pH, particle size, and temperature. FT-IR analysis confirmed the involvement of hydroxyl, carbonyl, and aromatic groups, with spectral changes indicating both physical and chemical adsorption mechanisms. Adsorption capacity increased with initial dye concentration and decreased with larger particle size or excessive adsorbent dosage. The process was highly pH-sensitive, favoring adsorption under neutral to alkaline conditions, while temperature had minimal influence, a finding compatible with a physisorption-dominated contribution to the overall process. Kinetic data were best described by the pseudo-second-order model, and equilibrium behavior was best described by the Langmuir isotherm; however, these mathematical fits are interpreted here as indicative of, rather than definitive proof of, the specific molecular mechanism, and the overall adsorption process is best described as involving a combination of physisorption and chemisorption contributions. The separation factor (RL) values indicated favorable adsorption. Furthermore, an exploratory artificial neural network (ANN) analysis, based on a limited dataset of 39 experimental observations, achieved a high goodness-of-fit (R2 = 0.99) in describing the nonlinear relationships between each individual operational parameter and the adsorption capacity; given the small sample size and limited validation strategy employed, these results should be regarded as a preliminary demonstration of feasibility rather than evidence of robust predictive generalization. The findings support the potential of CPH as an efficient biosorbent for dye-contaminated wastewater.

Separations doi: 10.3390/separations13090261

Authors: Lingyu Zhao Fuming Qu Hui Chen Zhengyu Liu Yaming Ji Xiaoming Liu

Accurate prediction of flotation concentrate grade is essential for maintaining product quality and supporting timely process adjustment. However, mechanistic prediction remains difficult because industrial flotation involves nonlinear multivariable interactions and partially observed operating states. Recent advances in machine learning have increased interest in data-driven methods, with encouraging results. Although recent studies have incorporated temporal dependencies into flotation-grade prediction, explicitly modeling the condition-dependent evolution of multivariate process–quality relationships under changing plant conditions remains challenging. In this study, industrial flotation records were systematically analyzed from a data-driven perspective to identify challenges affecting concentrate-grade prediction. Statistical analyses showed that variable–grade relationships are condition-dependent and vary across operating periods, indicating that measured variables only partially characterize evolving flotation states and that fixed input–output mappings may be inadequate. Accordingly, a DGraFormer-based model was developed to capture evolving inter-variable dependencies and multi-scale temporal patterns. For one-hour-ahead forecasting, the model achieved an RMSE of 0.7587 and an R2 of 0.5423 for iron concentrate grade, and an RMSE of 0.6917 and an R2 of 0.6384 for silica concentrate grade, outperforming the evaluated machine-learning and deep-learning baselines overall. These results underscore the importance of dynamic multivariate modeling for accurate concentrate-grade forecasting.

Separations doi: 10.3390/separations13090260

Authors: Ahmet Ozan Cengiz Yavuz Bülent Köse Bilge Nur Mutlu Derya Osmaniye Betül Demirci

Origanum saccatum P.H. Davis and O. solymicum P.H. Davis are two endemic species of section Amaracus distributed in Türkiye and characterized by close morphological and genetic relationships. Although their volatile and non-volatile compounds and several biological activities have previously been investigated, the antimicrobial and cytotoxic activities of methanol and ethyl acetate extracts of both species have not been systematically compared within a common experimental framework. In this study, the volatile profiles of the two species were compared, while the antimicrobial and cytotoxic activities of their methanol and ethyl acetate extracts were evaluated comparatively. Essential oils were obtained by hydrodistillation and analyzed by GC-FID/GC-MS. Antimicrobial activity was determined by the broth microdilution method, and cytotoxicity was evaluated against A549, MCF-7, and NIH/3T3 cells using the MTT assay. Both essential oils showed a p-cymene-rich profile, although substantial differences were observed in the proportions of γ-terpinene (3.1–24.4%), thymol (4.0–18.2%), borneol (0.6–15.6%), linalool (0.1–10.4%), and carvacrol (0.1–3.4%). The ethyl acetate extracts showed generally lower MIC values (125–250 µg/mL) than the corresponding methanol extracts (500–1000 µg/mL) against the most responsive microorganisms. Ethyl acetate extracts also showed the strongest cytotoxic activity with IC50 values of 6.74–14.49 µg/mL, although the response varied depending on species and cell line. The O. saccatum ethyl acetate extract showed the highest selectivity toward MCF-7 among the tested extracts, with a selectivity index of 3.176. To the best of our knowledge, this is the first report of the cytotoxicity of these two species against A549 and MCF-7 cells. The findings provide a comparative assessment of their volatile profiles and solvent-dependent biological properties.

Separations doi: 10.3390/separations13090259

Authors: Ping Liu Chuntao Zhang Jun Guo Fangyuan Yu Xu Ma

Lithium recovery from salt lake brines with high Mg/Li ratios remains highly challenging due to the comparable physicochemical properties of Mg2+ and Li+, while lithium–aluminum-layered double hydroxides (Li/Al-LDHs) have emerged as promising lithium-selective adsorbents. However, their practical application is hindered by particle aggregation, limited structural stability, and insufficient processability under continuous-flow conditions. Herein, a mineral-directed synthesis strategy was developed to construct natural mineral-supported Li/Al-LDHs composite adsorbents using three abundant clay minerals, chlorite, montmorillonite, and illite, as structural substrates. The mineral crystal structures were demonstrated to regulate the nucleation, growth behavior, and dispersion of Li/Al-LDH nanosheets, resulting in distinct hierarchical architectures and lithium adsorption performances. Comprehensive structural characterization revealed the successful integration of Li/Al-LDH phases with different mineral matrices while preserving the intrinsic layered structures of both components. The results demonstrated that different mineral substrates significantly influenced the crystal growth, dispersion, and interfacial structure of Li/Al-LDHs. Among the prepared composites, montmorillonite @Li/Al-LDHs exhibited the optimal lithium adsorption performance, achieving a lithium adsorption capacity of 6.0 mg·g−1 and a remarkable Li+/Mg2+ separation factor of 73.5 in a brine with a high Mg/Li ratio of 61.25. Furthermore, the optimized adsorbent maintained 81.7% of its initial adsorption capacity after 100 adsorption–desorption cycles and demonstrated stable lithium recovery performance under continuous-flow conditions. This work establishes the relationship between natural mineral crystal structures and Li/Al-LDH adsorption behaviors, providing new insights into the rational design of economical, scalable, and environmentally friendly lithium adsorbents for sustainable recovery of lithium resources from Mg-rich brines.

Separations doi: 10.3390/separations13090258

Authors: Qiaoling Tu Zengming Qu Zihuan Wang Yihang Tian Gang Tian Xiaoming Peng

Water-vapor removal from compressed air is governed by the product pressure dew point (PDP), dynamic bed utilization, hydraulic loss, regeneration demand, and cyclic reliability, yet activated-alumina studies are often interpreted from powder Brunauer–Emmett–Teller (BET) area or equilibrium uptake alone. This critical narrative review evaluates where evidence can and cannot be transferred across material, formed-particle, packed-bed, cycle, and field scales. It distinguishes equilibrium capacity, static test capacity, dynamic breakthrough capacity, and usable cycle capacity; conditionally compares desiccants and regeneration modes; and links PDP-defined breakthrough, mass-transfer-zone (MTZ)/length-of-unused-bed (LUB) measures, non-spherical-particle pressure drop, thermal waves, and regeneration endpoints. The available evidence supports several directional conclusions but not universal design values: alkali modification can increase uptake despite lower surface area; forming and binder chemistry alter accessible pores and strength; wall effects and particle geometry require measured hydrodynamic validation; and reported regeneration savings of approximately 27–40% are architecture-specific relative results rather than matched absolute energy benchmarks. A baseline-normalized diagnostic framework separates reversible regeneration faults and feed contamination from material aging and particle/bed degradation. The review identifies the central evidence gap as the absence of matched datasets reporting formed-body properties, adiabatic breakthrough, segmented pressure drop, regeneration energy, and long-cycle failure for the same material. It concludes with a standards-coverage map, a transparent screening sensitivity analysis, and a prioritized validation agenda.

Separations doi: 10.3390/separations13090257

Authors: Eliézer Quadro Oreste Krystopher Borges Krammer Antunielle Schneider Arias Rodrigo Gamarra Navarrete Janaína Oliveira Gonçalves Jean Lucas de Oliveira Arias Karina Lotz Soares Daiane Dias Ednei Gilberto Primel Anelise Christ-Ribeiro Sergiane Caldas Barbosa

The increasing occurrence of emerging organic contaminants (EOCs) in environmental matrices has intensified the demand for sensitive, selective, and sustainable analytical methods. Sample preparation plays a pivotal role, particularly for trace-level determination in complex matrices. Biochar is a promising sorbent for sample preparation because of its porous structure, tunable surface chemistry, low cost, and potential to be produced from renewable biomass waste. This review examines the use of biochar-based sorbents to extract EOCs from environmental matrices since 2020, with special emphasis on the relationships among precursor biomass, production conditions, surface chemistry, sorption mechanisms, and extraction performance. Agricultural waste was the predominant biomass class, while solid-phase extraction (SPE), magnetic solid-phase extraction (MSPE), and solid-phase microextraction (SPME) were the most frequently reported approaches. Biochar-based extraction has been applied to a wide range of EOCs, with pesticides being the most investigated analyte class. The authors discuss how pyrolysis conditions, activation, surface chemistry, and other parameters affect analyte retention and desorption. The authors compare different extraction approaches in terms of extraction efficiency, precision, and other analytical parameters. Finally, the authors discuss current limitations and research opportunities to guide the development of biochar-based sorbents as sustainable materials for sample preparation and environmental monitoring.

Separations doi: 10.3390/separations13090256

Authors: Elsa Uribe Jéssica López Camila Cortés Débora Cerdá-Bernad

Pecan oil is a valuable source of unsaturated fatty acids and bioactive compounds whose recovery and stability may be influenced by the extraction process. This study compared Soxhlet extraction (SE), ultrasound-assisted extraction (UAE), and supercritical CO2 extraction (sCO2) in terms of extraction yield, fatty acid profile, physicochemical properties, total phenolic content (TPC), antioxidant activity, and oxidative stability. SE achieved the highest extraction yield (69.21%), followed by sCO2 (52.89%) and UAE (48.68%). The fatty acid profile was relatively stable among extraction methods, although differences were observed in the relative proportions of oleic and linolenic acids. UAE produced oil with the highest TPC (32.55 µg GAE/g oil), whereas sCO2 showed the highest initial antioxidant activity (2681 µmol TE/100 g oil). After 12 days, UAE oil exhibited the lowest peroxide value (10.49 meq O2/kg) and the highest TPC retention, whereas sCO2 oil showed the greatest peroxide accumulation (28.16 meq O2/kg) and the largest decrease in TPC. These results demonstrate that extraction conditions differently affect oil recovery, antioxidant-related properties, and oxidative stability. Under the conditions evaluated, UAE showed particular advantages in preserving TPC and limiting primary oxidation during accelerated storage, despite its lower extraction yield.

Separations doi: 10.3390/separations13090255

Authors: Babak Rouhi Broujeni Ayoub Karimi-Jashni

This study aimed to remove licorice (Glycyrrhiza glabra) extract from pharmaceutical wastewater using a combination of treatment processes. An Artificial Neural Network (ANN) was coupled with a Genetic Algorithm (GA) to optimize the treatment parameters. Alum, polyaluminum chloride (PAC), and ferric chloride (FC), were first screened for chemical oxygen demand (COD) and color removal, after which alum was selected as the most effective coagulant for further experiments. The optimal ANN structure was identified based on three criteria: mean absolute percentage error, normalized root mean squared error, and correlation coefficient (R). The variables analyzed included pH (7–12), coagulant dose (200–1000 mg L−1), and oxidation time (6–60 min). ANOVA results revealed that coagulant type was the most statistically significant factor influencing both COD and color removal (p < 0.01), while pH and dose had relatively lower effects unless paired optimally. Results demonstrated a removal efficiency of approximately 98% under optimal conditions (pH = 10, coagulant dose = 610 mg L−1, and ozonation time = 53 min), with a remaining COD of 190 mg L−1. Overall, the combined coagulation–flocculation and ozonation process demonstrated high effectiveness for the treatment of licorice-based pharmaceutical wastewater.

Separations doi: 10.3390/separations13090254

Authors: Shanmei Li Mingxuan Li Jianping Meng Ligang Yu

Rapid and accurate quantification of residual guar gum in bauxite slurry flocculation is a critical bottleneck for closed-loop control of flocculant dosage. In this study, we systematically compared the anti-interference performance of the two UV-Vis spectrophotometer approaches, the single-wavelength absorbance method (A263) and the peak-trough difference method (ΔA), in complex slurry matrices. Our results revealed that the two methods respond differently to pH and salt concentration variations, leading to the proposal of a dual-mode synergistic detection strategy. The A263 method provides quantification under the specific conditions tested within the ranges of pH 3.0–8.0 and CaCl2 concentration below 4.5 mmol/L. Beyond these boundaries, deviations from the Beer-Lambert law occurred, attributable to conformational transitions or salting-out aggregation of the polymer chains. In contrast, the ΔA method partially mitigated background drift through differential calculation and exhibited a more stable signal trend than A263 across the tested ranges (pH 2.0–11.0, CaCl2 0–18 mmol/L), suggesting its potential utility as a semi-quantitative indicator in challenging matrices. However, its quantitative precision was constrained by small absolute signal values and systematic dependence on pH and salt conditions. Based on these findings, we propose a synergistic strategy-preferring the A263 method under routine conditions while recommending the ΔA method for high-salinity or wide-pH scenarios- and accordingly define the preliminary applicability boundaries based on signal response observations at a single concentration. Flocculation–sedimentation tests confirmed that the method successfully determined the optimum dosage (5.0 g/kg dry slurry), at which the residual concentration in the supernatant correlated negatively with the sedimentation rate (R2 > 0.95). The supernatant matrix after sedimentation (pH ≈ 7.1, low ionic strength) fell exactly within the safe window. This work provides a methodological reference for spectrophotometric quantification of trace organics in turbid, saline, and pH-variable slurry systems, and lays an analytical foundation for intelligent dosage control in bauxite slurry dewatering.

Separations doi: 10.3390/separations13090253

Authors: Fanxuan Xia Tao Yu Bin Kong Zhiyuan Wang Ran Wang Jiyi Mi Ruijie Xie Hanxiao Wang Zhiwei Li Zhuo Chen Ziquan Yin

Shipboard cabins can contain both oil mist-dominated particulate matter and volatile organic compounds (VOCs), creating a need for compact air-cleaning systems capable of simultaneous particle and gas-phase removal. This study developed an integrated filtration–adsorption air cleaner through a performance-oriented route combining a low-resistance gradient filter with an activated-carbon packed bed. The gradient filter maintained PM2.5 single-pass removal efficiencies above 99.99% across airflow rates of 150–650 m3/h and under inlet concentrations up to approximately 11 mg/m3, while maintaining relatively low airflow resistance. Three activated carbons were also systematically compared based on particle morphology, packed-bed characteristics, pore structure, and dynamic adsorption performance. JZT-07 showed the most favorable overall characteristics and achieved breakthrough capacities of 132, 167, and 159 mg/g for benzene, toluene, and n-heptane, respectively. The selected filtration and adsorption modules were integrated into accommodation- and machinery-cabin air cleaners and evaluated under standard-chamber and shipboard conditions. During treated voyages, average PM10 and TVOC concentrations decreased by 75.3% and 66.4% in the accommodation cabin and by 65.8% and 69.6% in the machinery cabin, respectively. These results demonstrate a practical development route from component optimization to device integration and field validation for simultaneous particulate and VOC control in confined ship environments.

Separations doi: 10.3390/separations13090252

Authors: Yibin Wang Kai Wang Jianbu Wang Zongxing Wang Xiaofei Yin Ning Du Aimin Zhang

Benzophenone-3 (BP-3), an organic UV filter extensively applied in sunscreens, cosmetics and daily plastic products, is classified as a typical emerging endocrine-disrupting micropollutant. This compound is highly susceptible to bioaccumulation in aquatic organisms, triggers coral bleaching, and incurs oxidative damage to algae, fish and invertebrates. Conventional wastewater treatment processes cannot efficiently eliminate BP-3 from aqueous media, thereby imposing severe ecological risks on freshwater and marine ecosystems. In this study, iron-impregnated biochar (Fe-BC) was synthesized via an impregnation–pyrolysis route using powder of cultivated Chlorella pyrenoidosa (green microalga) as raw feedstock. Batch adsorption experiments revealed that iron impregnation remarkably enhanced the removal efficiency of BP-3. The maximum Langmuir saturated adsorption capacity of Fe-BC reached 91.7 mg/g, considerably exceeding the value of 51.5 mg/g for pristine biochar. Kinetic data exhibited favorable fitting with the pseudo-first-order kinetic model, demonstrating that Fe-BC rapidly captures BP-3 and achieves adsorption equilibrium within 120 min. Solution pH exerted a prominent influence on adsorption performance: the material maintained high BP-3 adsorption capacity at pH 7–10, whereas adsorption capacity declined drastically under strongly acidic (pH < 5) and extreme alkaline conditions (pH > 10.5). Fourier-transform infrared spectroscopy (FTIR) validated the successful loading of iron species onto the biochar surface, as well as the binding of BP-3 onto Fe-BC. Combined with pH-controlled experimental results, hydrogen bonding, hydrophobic interactions, and pore-filling effects are inferred as the dominant adsorption mechanisms for BP-3 removal. Furthermore, Fe-BC retained favorable BP-3 removal performance in simulated seawater matrices, endowing it with preliminary potential for wastewater treatment in coastal zones and tourist scenic areas. This work offers basic laboratory insights into BP-3 adsorption, while further verification concerning environmental low-concentration conditions, authentic water matrices, material reusability and stability is essential for its practical application.

Separations doi: 10.3390/separations13090251

Authors: Yingli Li Meixi Cui Xu Ding Ying Yang Di Zhang Jianfei Song Yaodong Wei

Short-circuit flow severely degrades cyclone separation, yet its influence zone has not been clearly defined. In this work, the Reynolds stress model (RSM) was adopted to perform numerical simulations for a 300 mm PV-type cyclone separator, and the simulation results were validated against published tangential-velocity experimental data. The radial velocity along the extension lines of the vortex finder’s inner wall was analyzed to define the short-circuit flow influence zone, and a sector-resolved intensity index was proposed to quantify its circumferential non-uniformity. The results show that the lower boundary of the influence zone is a circumferentially varying curved surface rather than a horizontal plane. Among the four sectors, the 180–270° sector exhibits the greatest penetration depth (55 mm) and the highest inward radial velocity (−15.45 m/s). The proposed index indicates that Sector III contributes 38.7% of the total short-circuit flow intensity, and the dimensionless index is 0.127 for the present case. Within the influence zone, the inward radial velocity peaks at Z = 12 mm and approaches zero by Z = 53 mm, while the tangential velocity increases from 4.22 to 57.13 m/s, indicating Rankine vortex development. The short-circuit flow is governed by the coupled effects of inlet jet squeezing, vortex-core displacement, and the interaction between upward and downward flows. The proposed influence-zone definition and intensity index provide a quantitative framework for describing short-circuit flow and may be useful for evaluating cyclone design and short-circuit-flow suppression strategies.

Separations doi: 10.3390/separations13090250

Authors: Maqbool Hussain Liang Zhao Xusheng Zhang Hongyu Chen Yi Cui Hongxun Zhang Ruyin Liu Jianzhong Zheng

Gallium is a critical metal for high-tech industries, with its global demand surging in recent years. Currently, approximately 90% of primary gallium is extracted from Bayer liquor. Chelating resins such as amidoxime sorbents are widely adopted commercial materials for this purpose. However, gallium recovery from such highly caustic media remains a formidable challenge, as gallium is present at low concentrations while aluminate ions are hundreds of times more abundant, and the medium is rich in competing vanadate ions and humic substances. These interfering components impede both adsorption and desorption cycles, leading to a progressive decline in resin performance and a subsequent increase in operational costs. In recent years, functionalized carbon-based materials have gained significant traction. This growing interest is motivated by the carbon-based materials’ exceptional chemical resilience across both acidic and alkaline environments, tunable surface chemistry, and facile re-functionalization. This mini-review synthesizes recent progress in functionalized carbon-based materials for gallium recovery, with a particular emphasis on their adsorption performance and mechanistic insights. At the end of the paper, major challenges and research gaps are identified, and future research directions are proposed.

Separations doi: 10.3390/separations13090248

Authors: Duong Huu Huy Le Thi Ngoc Hanh

A simple and efficient QuEChERS-HPLC-DAD method was developed and validated for the simultaneous determination of benzoic acid, sorbic acid, and eight parabens in diverse food matrices. The sample preparation procedure was systematically optimized by evaluating the extraction solvent composition, salting-out conditions, and dispersive solid-phase extraction clean-up to achieve satisfactory recoveries while minimizing matrix interferences. Chromatographic separation was accomplished using isocratic elution on a C18 column with dual-wavelength ultraviolet detection, enabling the simultaneous determination of both authorized preservatives and non-authorized parabens within a single analytical run. The validated method exhibited excellent linearity (R2 > 0.996), low to moderate matrix effects (within ±20%), satisfactory recoveries (79–112%), and good precision (RSD < 7.3%), meeting the performance criteria for routine residue analysis. The applicability of the method was demonstrated by analyzing commercial food samples from six food categories. Benzoic acid and sorbic acid were the most frequently detected preservatives, whereas only methylparaben and propylparaben were identified among the investigated parabens. No non-authorized parabens were detected in the analyzed samples. Owing to its simplicity and reliability, the proposed QuEChERS-HPLC-DAD method represents a practical analytical approach for routine multi-matrix monitoring of food preservatives in quality control and food safety laboratories.

Separations doi: 10.3390/separations13090249

Authors: Yujian Wang Zhengang Liang Haimin Huang Zhenfeng Lin Qingqi Liu

This study developed a detection method for hymexazol residues in sugar beet, targeting its low molecular weight, high polarity, and lack of chromophores. The method optimized mass spectrometry conditions, liquid chromatography parameters, and extraction/purification protocols to address the matrix characteristics of sugar beet. Specifically, the sample pretreatment involved extraction with acetonitrile, followed by purification using GCB, silica, and C18 sorbents to minimize matrix interference. Sensitivity was enhanced by reducing flow rate and spray voltage. The method demonstrated high performance and was applied to analyze real samples. The LOD and LOQ were theoretically determined to be 1.22 and 3.80 μg/kg, respectively, using the blank standard deviation method. At the spiked levels of 5.0, 10, and 50 μg/kg, the intraday and interday recoveries were 80.2–97.9% and 78.1–101.7%, with corresponding RSDs of 4.8–6.4% and 4.6–8.8%, respectively. These results could meet the requirements for pesticide residue analysis and regulatory monitoring.

Separations doi: 10.3390/separations13090247

Authors: Yuehong Cui Ming Zhang Yuxiao Jing Hualei Yi Yafeng Yu Meng Yang Shuo Liu Jingyu Xu

Variations and unstable characteristics of two-phase flow in oil and gas pipelines readily induce severe equipment vibration and internal liquid sloshing, which seriously endanger the safety of pipeline systems. Existing investigations on conventional T-junctions have been restricted to single working conditions, without systematic optimization of structural parameters across multiple flow regimes or full evaluation of integrated separation and slug suppression performance. To address this research gap, this work proposed an optimized four-branch T-junction. The geometric configuration of the T-junction was optimized, and a test prototype was fabricated for gas–liquid two-phase flow experiments. Combined with experimental measurements and computational fluid dynamics (CFD) simulations, the overall performance of the optimized T-junction was comprehensively analyzed under diverse flow patterns and operating conditions. The test results indicated that the gas separation efficiency exceeded 90% under stratified flow, whereas slug flow brought strongly time-dependent separation performance. The gas separation efficiency was maintained above 40% for all test cases. The optimized structure reduced liquid slug velocity and length and significantly suppressed liquid level fluctuations in the downstream separation tank. The numerical predictions agreed well with experimental data, which validated the reliability of the present numerical framework. This study provides technical references for the design of inline pipe separators that realize both gas–liquid separation and slug mitigation.

Separations doi: 10.3390/separations13090246

Authors: Nurasyqin Abdul Fattah Muhammad Zulhaziman Mat Salleh Nor Yuliana Yuhana Mohd Ali Hashim Mohamed K. Hadj-Kali

A circular economy for polyethylene terephthalate (PET) aims to achieve complete material recirculation and reduce dependence on fossil-based feedstocks. Among recycling strategies, depolymerization offers the greatest potential for true circularity. This work investigates deep eutectic solvent (DES)-assisted PET depolymerization using a tetrabutylammonium bromide/sulfolane (TBABr/Sulf) system. A four-factor, three-level Box–Behnken design was employed, where reaction time, NaOH concentration, PET/solvent ratio, and water content were selected as independent variables, with PET weight loss as the response. The optimized conditions of 35 min reaction time, 5.9 wt% NaOH, a PET/solvent ratio (g/g) of 0.061, and a 1:1 water-to-DES ratio achieved 97% PET depolymerization and 93.8% TPA recovery. The process achieved a relatively low PET/DES (g/g) utilization ratio of 0.12 and required at least 40% less NaOH than other DES-based alkaline hydrolysis reported in the literature. The identity and quality of the recovered TPA were confirmed by FTIR, NMR, DSC, and elemental analysis. Under microwave-assisted conditions, TBABr/Sulf was successfully reused over three consecutive cycles while maintaining 100% depolymerization efficiency with consistent TPA quality. Collectively, these results demonstrate the technical potential of the proposed DES-assisted PET depolymerization process, particularly in terms of reduced solvent and alkaline requirements, shortened reaction time, and demonstrated solvent recyclability.

Separations doi: 10.3390/separations13090245

Authors: Shantel N. Mohammed Sharad Maharaj Marian J. Watson David R. McGaw Cian Coonai

This study investigates the formulation of a natural cosmetic product using pigment derived from annatto (Bixa orellana) seeds, which is widely utilised as a natural colourant in food, pharmaceutical, and cosmetic applications. The objective was to optimise pigment extraction using supercritical fluid extraction (SFE) and evaluate its suitability for cosmetic formulation. Extraction was performed using supercritical carbon dioxide and ethanol as a co-solvent over a range of operating conditions to identify parameters that provided high pigment recovery. High extraction yields were obtained under several operating conditions, with favourable performance achieved at relatively low temperature, pressure, and flow rate. The annatto pigment extract was incorporated as a colouring agent into a naturally derived lipstick formulation containing beeswax and plant-derived oils. The developed formulation demonstrated satisfactory performance and appearance, confirming the suitability of annatto-derived pigment. Colour analysis indicated that processing conditions influenced extraction yield but did not significantly affect pigment colour or final product appearance. Overall, the results support the use of annatto pigment extracted via SFE as a viable and sustainable option for natural cosmetic product development.

Separations doi: 10.3390/separations13090244

Authors: Yanghua Liu

Polyethylene wax (PEW) often carries a broad carbon-number distribution (CND) that limits its use in grades with controlled melting point, viscosity, and hardness. This study examines how multistage molecular distillation reshapes PEW composition and how the resulting compositional change is transmitted to fraction properties. An industrial PEW was processed through a wiped-film light-removal step and three short-path distillation stages, yielding five fractions whose normalized yields were 4.03% (PEW-40), 12.16% (PEW-70), 22.26% (PEW-80), 30.33% (PEW-90) and 30.71% (PEW-105). The peak carbon number migrated stepwise from C42 in the feedstock to C21, C37, C42, C50 and C68 in the fractions, and basic wax properties, DSC transition temperatures and TGA mass-loss temperatures moved consistently with the compositional shift. Weighted mean carbon number correlated with drop melting point (R2 = 0.938), kinematic viscosity at 100 °C (R2 = 0.951), penetration (R2 = 0.780) and oil content (R2 = 0.798), and the second-heating melting peak correlated with the 50% mass-loss temperature (R2 = 0.992). These results support a three-level correspondence connecting distillation operation, CND reshaping and fraction properties, and position molecular distillation as a grade-oriented physical process for by-product PEW.

Separations doi: 10.3390/separations13090243

Authors: Jianfa Wu Wenbin Liu Ying Cui Zhiqiang Gan Jing Zhang Tingting Kuang Ce Tang Dongsheng Ren Yue Liu Yi Zhang

Xueshan Jinluohan Pain-Relief Liniment (XJPL) is a Tibetan topical compound preparation composed of 11 medicinal materials. Its current quality standard relies mainly on thin-layer chromatographic identification, which is insufficient to comprehensively characterize its complex chemical composition, marker constituents from key medicinal materials, and batch-to-batch quality consistency. In this study, 17 batches of XJPL were analyzed by ultra-performance liquid chromatography coupled with quadrupole-Exactive Orbitrap high-resolution mass spectrometry (UPLC-Q-Exactive Orbitrap MS) for systematic chemical profiling. An integrated quality evaluation method was further developed by combining high-performance liquid chromatography (HPLC) fingerprinting, similarity evaluation, chemometric analysis, and multicomponent quantification. A total of 139 chemical constituents were confirmed by reference standards or putatively characterized, including alkaloids, flavonoids, phenolics, terpenoids, organic acids, lactones, and other compounds, indicating the coexistence of multiple medicinal-material-derived and structurally diverse constituents in XJPL. The HPLC fingerprint established for the 17 batches contained 23 common peaks, among which 10 representative constituents were assigned, and similarity evaluation indicated a high degree of overall chemical consistency among batches. Hierarchical cluster analysis (HCA), principal component analysis (PCA), and orthogonal partial least squares-discriminant analysis (OPLS-DA) further revealed batch-related differences and suggested that common peaks corresponding to gentiopicroside, loganic acid, and related constituents contributed substantially to sample differentiation. On this basis, quantitative methods were established for representative constituents covering phenolic acids, iridoid glycosides, carotenoid glycosides, and Corydalis-derived alkaloids. Overall, this study improves the quality evaluation framework for XJPL by integrating chemical profiling, holistic fingerprint assessment, batch-difference characterization, and multicomponent quantitative control, providing experimental support for quality standard improvement and manufacturing quality control.

Separations doi: 10.3390/separations13090242

Authors: Rezeye Rehemituli Qiaoyu Liu Xinyue Wang Jingmao Wang Ziheng Zhang Yansheng Liu Junwei Hou

To improve regeneration performance and shorten desorption time in amine-based CO2 capture, this study proposes an integrated “blended-amine solvent and microwave regeneration” process. Triethylenetetramine (TETA) was used as the primary absorbent and blended with diethanolamine (DEA) and 2-amino-2-methyl-1-propanol (AMP). Response Surface Methodology (RSM, Box–Behnken design) was employed to establish formulation–performance relationships, and an entropy-weighted TOPSIS method was further applied for multi-objective evaluation and optimization. The optimal formulation consisted of TETA, DEA, and AMP at a mass ratio of 6:1:2. Under the optimized conditions (20 wt% aqueous solvent, 30 °C absorption, 95 °C microwave regeneration), the solvent achieved an absorption capacity of 1.0 mol CO2·mol−1 amine with a CO2 recovery of 93.56%. Compared with conventional heating, microwave regeneration markedly accelerated CO2 desorption, reducing regeneration time from 30 min to 4 min. The estimated total regeneration energy was approximately 2.4 GJ·t−1 CO2 under microwave heating for the optimized blend. In addition, among the water/n-butanol formulations tested, the fully aqueous system showed the best overall absorption–regeneration performance. Overall, the data-driven solvent design coupled with microwave regeneration offers a practical route toward more efficient CO2 capture processes.

Separations doi: 10.3390/separations13090241

Authors: Zengqiang Chen Shuai Zhou Yadong Zhang Guangqing Zhu Bin Li Dingjie Zhang Enhui Zhou

During coal beneficiation in a gas–solid fluidized bed, coarse feed particles act as moving intruders whose size and shape can reorganize the local gas–solid flow field. This study combines particle-surface differential-pressure measurements, synchronized visual observation, pressure-signal analysis, and Eulerian–Eulerian CFD to distinguish the disturbance caused by the feed particle from the background fluctuation of the dense medium. Unlike studies that characterize only the global bed pressure drop, the present work resolves the pressure response on the upper and lower surfaces of individual 13–50 mm feed particles and links it to bubble attachment, bypassing, and medium-particle recirculation. Within a fluidization-number range of 1.0–1.6, the disturbance intensified with feed-particle size: the 50 mm particle produced the largest upper–lower pressure difference and pressure-drop fluctuations exceeding 100 Pa. Particle shape also altered the local flow topology; the flat lower face of the block-shaped particle promoted a persistent gas cushion, localized pressure concentration, and medium recirculation; whereas, the spherical particle generated a comparatively symmetric disturbance. Synchronized images confirmed the transition from intermittent small bubbles near minimum fluidization to bubble coalescence and vigorous recirculation at higher gas velocities. At N = 1.2, the CFD results reproduced the experimental size and shape rankings, with case-by-case relative errors of 4.7–7.0% and a mean absolute relative error of 5.5%. Coherence analysis further showed that the influence of a large particle decayed with distance and produced a stepwise axial distribution of local flow states. These results provide a particle-scale basis for controlling feed-induced disturbances in gas–solid fluidized-bed separation.

Separations doi: 10.3390/separations13090240

Authors: Yujie Ding Jiacan Huang Zhigang Xu

Molecularly imprinted polymers (MIPs) have emerged as promising recognition materials for antibiotic sensing owing to their high stability, low cost, and tunable selectivity. However, enhanced recognition capability does not necessarily translate into high-performance sensing. A critical yet often overlooked bottleneck lies in the inherently indirect nature of this conversion: molecular binding occurs within an insulating polymer matrix that is spatially and functionally decoupled from the underlying signal transducer, particularly in complex environmental matrices. To address this limitation, this review proposes a unified framework centered on recognition–structure–signal interplay. Within this framework, sensing performance depends not on the simple addition of independently optimized components, but on the synergistic integration of recognition fidelity, structural accessibility, and signal transduction efficiency. Recent advances in electrochemical, optical, photoelectrochemical, and electrochemiluminescent MIP sensors are critically examined through this lens, with emphasis on platform-specific failure modes-including inaccessible recognition sites, insufficient site-transducer integration, weak binding-induced signal modulation, signal amplification-dominated responses, and matrix-induced decoupling. Machine learning is further critically assessed as an emerging data-driven tool for MIP design, signal decoding, experimental optimization, and sensor-level performance prediction, while its broader applicability remains constrained by limited datasets, insufficient external validation, and poor cross-platform transferability. Despite major progress in sensitivity, unresolved challenges persist, including weak intrinsic conversion efficiency, structural trade-offs, limited reliability in real-world samples, a lack of standardized validation protocols, and poor scalability of laboratory fabrication. This review concludes that next-generation MIP-based antibiotic sensors require a paradigm shift from affinity-oriented imprinting and signal amplification toward co-localized recognition-transduction interfaces, matrix-tolerant architectures, interpretable data-driven design, and manufacturable field-deployable systems.

Separations doi: 10.3390/separations13090239

Authors: Zhengwu Peng Ruili Zheng Xiangyu Wang Zhen Wan Xiaolin Pan Zhi Wang Zongliang Zhang Dong Wang Guoyu Qian

The increasing generation of spent Ni-rich layered cathodes creates an urgent demand for efficient lithium recovery and value-added reutilisation of transition-metal components. An MnSO4·H2O-assisted rapid thermal reconstruction route coupled with water leaching was developed for selective lithium recovery from spent NCM811 cathodes. At an MnSO4·H2O-to-NCM811 mass ratio of 0.9:1, an applied current of 30 A, and a treatment duration of 20 s, the layered structure was converted into water-soluble lithium sulfates and transition-metal-rich oxides. Water leaching at 20 °C for 20 min achieved a stage lithium-leaching recovery of 99.12%, with limited dissolution of Ni, Co, and Mn. The combined aqueous stream contained 0.42 g L−1 Li. After concentration and CO2 carbonation, Li2CO3 was obtained with a precipitation efficiency of 90.6% and a purity of 99.52 wt.%, corresponding to an overall lithium recovery of 88.7%. Elemental-balance closures were 98.6–99.6% for Li, Ni, Co, Mn, and S. The regenerated cathode LiNi0.54Co0.07Mn0.39O2 delivered 95.2 mAh g−1 after 150 cycles at 0.2 C. These results demonstrate integrated lithium recovery and transition-metal reutilisation from spent Ni-rich cathodes.

Separations doi: 10.3390/separations13090238

Authors: Jian Xu Peixuan Li Wenxia Zhu Jianhua Kang Li Wang

Ceramic balls are utilized as grinding media for regrinding of titanomagnetite rougher, owing to its low liberation degree and intricate intergrowth with gangue minerals. Process mineralogy, regrinding experiments and EDEM simulations were adopted to investigate the influencing mechanism of ceramic balls on the regrinding performance of titanomagnetite rougher. The Dv(90) of titanomagnetite rougher is 198.19 μm, and the titanomagnetite is closely intergrown with gangue minerals, including chlorite, serpentine and ilmenite, in the forms of inclusions, interlocks and solid solutions with a liberation degree of 75.54%. The Dv(90) reduces to 39.86 μm, and the liberation degree of titanomagnetite increases to 92.86% after regrinding with ceramic balls. The grade was improved from 53.01% to 58.83% with a recovery of 96.19% after magnetic separation. EDEM simulation results reveal that raising stirrer speed elevated collision energy, increasing pulp density enhanced viscous coupling and particle capture, and improving media filling ratio boosted collision frequency. These findings demonstrate that ceramic balls could effectively refine product size, facilitate mineral liberation and improve concentrate grade, offering a viable pathway toward efficient utilization of titanomagnetite.

Separations doi: 10.3390/separations13080237

Authors: Linyiyin Wang Caiyun Xu Yisheng Azuo Liying Qiu Zangjia Geng Jiachuan Li Laiming Li

This study developed an integrated process combining ultrasound-assisted enzymatic extraction (UAEE) with purification for the efficient recovery of bioactive flavonoids from Rhododendron anthopogonoides Maxim. (RA). Extraction conditions were optimized via Plackett–Burman screening followed by response surface methodology (RSM). Optimal conditions (enzyme dosage 30 mg/g, liquid-to-solid ratio 30:1 mL/g, 70% ethanol, 70 °C, ultrasonic power 490 W, extraction time 40 min) produced a total flavonoid yield of 13.56%. RSM established a reliable quadratic model (R2 = 0.9800), with artificial neural network cross-validation further validating the robustness of the optimized parameters. Notably, UAEE substantially outperformed conventional ultrasound-assisted extraction. Purification using AB-8 resin raised flavonoid purity to 25.4 ± 0.48%. SEM and FT-IR analyses revealed effective cell wall disruption while maintaining flavonoid structural integrity. UPLC-Q-Orbitrap-HRMS identified 19 flavonoid compounds in the purified fraction. In vitro assays demonstrated that the purified flavonoids exhibited strong antioxidant activity, with IC50 values of 28 µg/mL (DPPH), 38 µg/mL (ABTS+), and 43 µg/mL (•OH), corresponding to scavenging rates of 98.4%, 98.1%, and 94.2% at 200 µg/mL, respectively. Furthermore, the purified flavonoids dose-dependently inhibited the release of NO, TNF-α, and IL-6 in LPS-induced macrophages at non-cytotoxic concentrations.

Separations doi: 10.3390/separations13080236

Authors: Doretta Cuffaro Enrico Crispino Lizzia Raffaghello Roberto Benelli Vincenzo Calderone Maria Digiacomo Elisa Nuti

Antibody–drug conjugates (ADCs) are structurally complex biopharmaceuticals whose quantitative characterization is often complicated by payload-related interferences and molecular heterogeneity. In this study, two complementary chromatographic methods based on reverse-phase ultra-high-performance liquid chromatography (RP-UHPLC) and size-exclusion ultra-performance liquid chromatography (SEC-UHPLC) coupled with diode array detection were developed and comparatively evaluated for quantitative and integrity assessment of Cetuximab (CET) in ADC formulations. The RP-UHPLC method, developed on a C8 stationary phase under denaturing conditions, showed linearity over the range 0.05–5 mg/mL (R2 = 0.9979), with LOD and LOQ values of 10 and 40 μg/mL, respectively. The SEC-UHPLC method, optimized under native conditions on a Yarra SEC-3000 column, exhibited linearity within the 0.5–5 mg/mL range (R2 = 0.9998), with LOD and LOQ values of 17 and 52 μg/mL, respectively. Both methods showed satisfactory accuracy, precision, and robustness according to a fit-for-purpose validation approach. Application to CET-based ADCs bearing different aminobisphosphonate payloads confirmed reliable quantification. RP-UHPLC enabled sensitive determination of antibody concentration, whereas SEC-UHPLC enabled assessment of monomeric integrity and sample heterogeneity under native conditions. Comparative analysis of aged ADC samples demonstrated that SEC-UHPLC revealed loss of structural integrity and sample heterogeneity that were not detectable by RP-UHPLC or direct UV spectrophotometry. The combined RP-UHPLC/SEC-UHPLC workflow provides a robust, accessible, and complementary platform for routine quantitative analysis and integrity assessment of ADC formulations.

Separations doi: 10.3390/separations13080235

Authors: Tingjie Xu Dahuan Gan Guowang Wei Xing Wei Zijian Qiu Jun Wu Zhenhai Huang Chunlin He Qiankun Wei

Germanium is a strategically critical metal with indispensable applications in infrared optics, fiber-optic communications, and semiconductor devices. Although previous reviews have extensively addressed the hydrometallurgical recovery of germanium from specific enriched materials and the associated extraction efficiencies, a systematic and integrated understanding of its migration behavior, occurrence states, and phase transformations across the entire zinc smelting process is still lacking. This review fills this gap by investigating the migration and enrichment characteristics of germanium in zinc smelting residues and by constructing a comprehensive framework encompassing occurrence, roasting, leaching, separation, and purification, covering the entire route from zinc concentrate to high-purity germanium production. By establishing this integrated analytical framework that traces the migration and enrichment pathways throughout the whole process chain, this review provides a valuable technical reference for elucidating the migration patterns of germanium in complex smelting systems, devising efficient recovery strategies, and advancing the sustainable utilization of germanium resources.

Separations doi: 10.3390/separations13080234

Authors: Zulaikha Abid Yuandong Liu

The global energy transition and rapid electrification are driving increased demand for copper. However, conventional pyrometallurgical and hydrometallurgical extraction routes are increasingly challenged by declining ore grades and stricter environmental regulations. Bioleaching involves the microbial catalysis of sulfide mineral dissolution and provides a sustainable method for copper recovery from low-grade ores, tailings and secondary resources. This review provides a critical and integrated analysis of copper sulfide bioleaching, covering microbial diversity, molecular mechanisms, mineralogical controls, operational parameters, and industrial applications. This review also examines the functional roles of prominent acidophiles, including the functional roles of prominent acidophiles, including Acidithiobacillus spp., Leptospirillum spp. and thermophilic archaea, in the oxidation of iron and sulfur, mitigation of passivation, and metal solubilization. The molecular underpinnings of these processes are explored by investigating iron and sulfur oxidation gene networks (the rus operon and sox cluster), copper resistance systems (CopA, CusCBA) and biofilm formation pathways. The mineralogical controls on the behavior of chalcopyrite (refractory/passivating), chalcocite (highly reactive) and bornite (intermediate) are critically assessed. The synergistic effects of key operational parameters (temperature, pH, redox potential, aeration and particle size) on leaching kinetics and microbial community dynamics are investigated. The scalability, efficiency and environmental footprint of industrial applications such as heap, dump, stirred-tank and in situ bioleaching are discussed. Despite more than four decades of commercial development, several challenges remain, such as slow chalcopyrite dissolution, passivation, metal toxicity, and scale-up limitations. Emerging solutions such as synthetic microbial consortia, multi-omics technologies, artificial intelligence-assisted optimization, and digital twins are identified as transformative approaches for next-generation biomining. In this review, microbiology, mineralogy, electrochemistry, and process engineering are integrated to demonstrate that biotechnological leaching is among the most promising technologies for the sustainable production of copper and to identify future directions for its industrial application.

Separations doi: 10.3390/separations13080233

Authors: Jiawei Wang Meiqin Zheng

A new efficient coupled process to produce green solvent ethyl propionate was developed, which involved a fixed-bed reactor and pervaporation membrane separation. Firstly, the esterification reaction alone was investigated to explore reaction conditions and kinetics. Secondly, the pervaporation alone was investigated to explore separation conditions and the separation performance of pervaporation membranes. Then, the esterification reaction, coupled with pervaporation to enhance the reaction process, was investigated. Finally, the mathematical model of the esterification reaction, coupled with the pervaporation process, was established. The results showed that the conversion of ethanol reached 78.4% within 5 h. The reaction kinetics were obtained based on the pseudo-homogeneous (PH) model. Under the condition of a circulation flow rate of 100 L/h, the influence of concentration polarization could be well overcome, and a high level of pervaporation could be achieved. The pervaporation coefficients of the four-component system were obtained based on Fick’s law. The dehydration rate increased significantly with the increase in pervaporation temperature, which could effectively enhance the esterification reaction. The model could well predict the experimental results, and the experimental results were in good agreement with the theoretical calculations.

Separations doi: 10.3390/separations13080232

Authors: Chuyue Zhang Le Duan Xu Wang Lanlan Qiu Deli Xiao

Reversed-phase chromatography stationary phases (such as C18) are widely used in commercial high-performance liquid chromatography (HPLC). However, when dealing with complex mixtures, they often exhibit limited separation capabilities and peak tailing phenomena. To address this problem, two novel HPLC stationary phases based on polyamine macrocycles were developed. A trianglamine macrocyclic stationary phase (TRI-Sil) was first prepared using chlorinated silica gel as the support, which can effectively separate a variety of aromatic compounds, but with limited selectivity for positional isomers such as phenylenediamine. To further improve the separation selectivity, a polyamine-silica macrocyclic stationary phase (CPAM-Sil) was synthesized by introducing a branched-chain-containing monomer. Under optimized conditions, CPAM-Sil achieved baseline separation of phenylenediamine and phenylenediol positional isomers and improved the separation of terphenyl isomers, with favorable asymmetry factors and high column efficiency compared with the commercial C18 column. Molecular docking confirmed multiple interactions such as electrostatic interactions and hydrogen bonding between the polyamine macrocycle (CPAM) and analytes. The CPAM-Sil column also exhibited good reproducibility and stability, showing promising potential for industrial application in chromatographic separation.

Separations doi: 10.3390/separations13080231

Authors: Rou Wang Chunlei Liu Jing Chang Shaopo Wang Jianfei Li

Excessive nitrate discharge causes water eutrophication and public health risks, which has become a core challenge in global water environment governance. Conventional nitrogen removal technologies suffer from limitations such as carbon source dependence and secondary pollution, and can hardly meet the requirements of low-carbon water treatment. Driven by electric energy and free of additional chemical reagents, electrocatalytic nitrate reduction enables flexible regulation of product selectivity. Among all possible reaction pathways, selective N2 production is the nitrogen removal route with the highest environmental benefits. However, constrained by the high energy barrier of N–N coupling and intense competition from side reactions, achieving highly selective N2 production remains a major technical difficulty, and most existing reviews in this field focus on ammonia synthesis. This paper systematically reviews the research progress in this field, elucidates the reaction network and nitrogen production mechanism, compares the advantages and disadvantages of three types of selectivity evaluation methods, summarizes the design strategies of multi-scale electrocatalysts, and analyzes how operational parameters (including applied potential, electrolyte composition, pH, etc.) and reactor configuration regulate the reaction selectivity. Finally, the existing challenges are concluded and future development directions are prospected, so as to provide a reference for the research, development and engineering application of electrocatalytic nitrogen removal technology.

Separations doi: 10.3390/separations13080230

Authors: Runlin Han Zanming Zhu Jiale Li Yiting Kou Chaowei Yan Hongbo Gu

Photocatalytic degradation technology has been widely acknowledged for its low cost and high degradation efficiency. However, the loss, migration and difficult recovery of powdered catalysts are still critical bottlenecks for practical applications. In this study, silver nanoparticles (Ag NPs)/polyvinylidene fluoride (PVDF) photocatalytic composite membranes were in situ fabricated by incorporating AgNO3 into a PVDF casting solution, followed by electrospinning and UV post-treatment. The resulting membranes exhibited sustained photocatalytic capability towards dyes and antibiotics. The optimal membrane achieved 89.6% and 83.0% degradation efficiency for chloramphenicol (CAP) and rhodamine B within 16 h under UV irradiation, respectively. Free radical trapping experiments revealed that the superoxide radical (·O2−) dominated the photocatalytic degradation of CAP, and the mechanism of photocatalytic degradation was explored. Additionally, the Ag NPs/PVDF photocatalytic membrane demonstrated a distinct antibacterial efficacy against Staphylococcus aureus (S. aureus) with a distinct inhibition zone of 20 mm, effectively inhibiting bacterial proliferation.

Separations doi: 10.3390/separations13080229

Authors: Shuyun Chen Changchun Mu Jun Zhang Ming Shao Dawei Yu Kunkun Jiang Xuchen Fan Hongning Duan

Gas–solid fluidized bed separation uses upward gas flow to fluidize a dense medium. By controlling medium properties, gas velocity, and bed height, the apparent bed density can be adjusted so that low-density particles float and high-density particles sink. In practice, separation density may differ from measured bed density. Large feed particles can cause local defluidization near the upper bed, increasing resistance and effective particle weight. Bubble behavior also affects separation: near minimum fluidization, limited bed activity restricts particle motion, whereas higher gas velocities promote bubble growth, coalescence, and wake-induced upward transport of medium particles. Fine low-density particles may also pass through bubbles, disrupting normal separation. These effects are especially important in high-bed Geldart A systems. This study developed a separation-density model for a Geldart A dense-medium gas–solid fluidized bed from the force balance of spherical particles and compared it with a Geldart B model. Forces on spherical simulated feed particles were measured under different operating conditions, and theoretical separation densities were calculated. Separation tests were then performed to evaluate the effects of gas velocity and bed height, compare bed and separation densities, and assess model reliability. The results support density regulation and scale-up of dry beneficiation using Geldart A media.

Separations doi: 10.3390/separations13080228

Authors: Da-Qi Cao Zheng-Wei Yan Qing-Yue Zhang Wen-Yu Zhang

Extracellular polymeric substances (EPS) are recoverable high-value biopolymers from excess sludge (ES), but their antioxidant performance and enhancement strategies remain poorly understood. This study systematically investigated sludge-derived EPS (EPSS) and Pseudomonas sp.-derived EPS (EPSP) to elucidate the effects of source, extraction conditions, and sulfation on antioxidant activity. Compositional analysis, physicochemical characterization, Fourier-transform infrared spectroscopy, and excitation-emission matrix fluorescence spectroscopy were used for mechanistic analysis. EPSS exhibited stronger 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity than EPSP, associated with its higher polysaccharide content, lower protein-to-polysaccharide ratio, and more stable polysaccharide–protein heterogeneous network. Extraction conditions significantly influenced EPS yield, particle size, apparent viscosity, and composition; optimal recovery efficiency and antioxidant activity were achieved by centrifugation at 10,000 rpm for 10 min followed by dialysis through a 3500 Da molecular weight cutoff membrane. Sulfation successfully introduced sulfate ester groups while preserving the main structural framework, further enhancing the radical scavenging activities of both EPS types. Notably, EPSS demonstrated greater structural stability during sulfation and retained higher Pb(II) removal capacity compared with EPSP at the tested concentration. Overall, this study provides a mechanistic understanding of factors governing EPS antioxidant performance and validates sulfation as an effective enhancement strategy, supporting the high-value utilization of ES from wastewater treatment plants.

Separations doi: 10.3390/separations13080227

Authors: Jinhua Wang Na Xiao Po Bai Junfeng Wu Xindi Wan Yafei Zhao

Heavy metal wastewater, characterized by high toxicity, poor biodegradability, and strong bioaccumulation potential, poses a serious threat to the ecological environment and human health. Conventional chemical treatment methods are costly and prone to secondary pollution. In contrast, using solid waste to prepare environmental functional materials for “waste control by waste” has emerged as a research hotspot in the field of synergistic water pollution control and resource recovery. This review systematically consolidates the sources, physicochemical properties, and compositional characteristics of typical industrial solid wastes—including red mud, electroplating sludge, fly ash, copper slag, and blast furnace slag—and elucidates how compositional variations constrain the selection of functionalization pathways. On this basis, key preparation techniques, namely hydrothermal synthesis, surface modification/impregnation, thermal treatment, geopolymerization, and sol–gel/polymerization, are critically reviewed and compared in terms of product structural regulation, process complexity, and engineering scale-up potential. Subsequently, the adsorption performance of the resultant materials toward heavy metals such as Pb2+, Cu2+, Cr(VI), As(VI), Cd2+, Ni2+, and Zn2+ is discussed, with particular emphasis on the pronounced effects of pH, temperature, initial concentration, coexisting ions, and adsorbent dosage on adsorption capacity. Notably, Pb2+ exhibits the highest adsorption capacity, whereas the removal of Cr(VI) and As(V) is strongly governed by the positive charge density and reduction efficiency of the material surface. In quinary heavy metal competitive systems, marked differences in the affinity of adsorption sites toward distinct metal ions have been observed. Mechanistic analysis identifies ion exchange, surface complexation, electrostatic attraction, and redox reactions as the predominant removal pathways. This review further incorporates engineering-oriented assessments, including multi-component competitive adsorption, fixed-bed column operation, and regeneration stability, and identifies the critical bottlenecks currently impeding the transition from laboratory-scale research to practical implementation—namely, performance instability arising from feedstock variability, attenuation of adsorption capacity during prolonged operation (with a 10–40% decline over 5–10 cycles), underdeveloped regeneration and recovery routes, and a systemic deficiency in techno-economic analysis and life-cycle assessment data. Finally, future research directions are proposed, emphasizing the development of low-carbon and energy-efficient preparation technologies, the promotion of synergistic valorization of multiple solid wastes alongside critical metal recovery, and the advancement of this field toward engineering applications through artificial intelligence-assisted design and life-cycle assessment, thereby furnishing theoretical references and technical support for the integrated management of industrial solid waste resource utilization and heavy metal wastewater treatment.

Separations doi: 10.3390/separations13080226

Authors: Levent Pelit Berfu Yığrık Sibel A. Ozkan

Separation sciences in Türkiye have evolved from early laboratory-based instruction into a robust, multidisciplinary field integral to analytical chemistry. The foundational roots were established before the Ottoman period and were further strengthened with the integration of chemistry into medical, pharmacy, military, and technical curricula. Following the inception of Darülfünun, the first European-style higher education institution and subsequent Republican-era academic reforms, chemistry emerged as an independent discipline supported by specialized institutes and training programs. Collaborative efforts by Turkish and foreign scientists fostered a rigorous laboratory culture, laying the groundwork for modern analytical practices. Since the mid-twentieth century, advanced sample preparation, chromatographic, electrophoretic, and mass spectrometry-based methods have become pivotal across Turkish research centers. Today, these methodologies drive critical applications in environmental monitoring, pharmaceutical and biomedical analysis, food safety, toxicology, forensic science, and industrial quality control. Reflecting this sustained growth and rising international prominence, Türkiye was formally admitted to the Central European Group of Separation Sciences at the 29th International Symposium on Separation Sciences in Belgrade, Serbia, in September 2025. This article provides a comprehensive historical overview of separation sciences in Türkiye, highlighting institutional evolution, major scientific contributors, and the contemporary research directions shaping the field’s future.

Separations doi: 10.3390/separations13080225

Authors: Jian Feng Tao Ou Wuhan Zhang Xin Deng Shijun Chen Xiaoyan Wu Jianyun Chen Ruan Chi Fang Zhou

After in situ leaching of weathered crust elution-deposited rare earth ore (WREO), large amounts of residual ammonium (RA) salts remain in the ore body and slowly release, causing persistent ammonia-nitrogen pollution in surrounding waters. This study proposes using magnesium chloride for in situ elution remediation of closed mines. Column experiments were conducted to evaluate the effects of eluent concentration, liquid–solid ratio, flow rate, pH, and temperature on residual ammonium removal, and a kinetic model was established based on the shrinking unreacted-core model. The results show that increasing Mg2+ concentration, temperature, or flow rate accelerates the eluting rate, with temperature being the most influential. A higher liquid–solid ratio in the tested range could enhance the elution efficiency of residual ammonium, but it will substantially raise the production cost. Weakly acidic pH 4–6 favors the reaction, while alkaline conditions inhibit it. Kinetic analysis indicates inner particle diffusion control, with an activation energy of 6.03 kJ/mol and a reaction order of 0.3009. Under optimal conditions of 0.1 mol/L Mg2+, 2:1 liquid–solid ratio, 0.6 mL/min, pH 4–6 and room temperature, elution efficiency reaches 95.45%. This work provides theoretical and technical support for green remediation of historical ammonium contamination in WREO.

Separations doi: 10.3390/separations13080224

Authors: Meysam Barasm Sodeif Azadmard-Damirchi Mohammadali Torbati Ebrahim Afkhami Sarai

Black cumin (Nigella sativa L.) oil is one of the most important vegetable oils with food, therapeutic and medicinal uses; however, it has high acid and peroxide values even in fresh oil extracted by cold pressing. One of the main factors that can cause high peroxide value (PV) and acid value (AV) in the extracted black cumin oil (BO) is the presence of essential oils (EO), which are highly sensitive to oxidation. In this study, separation by steam was used to strip EO from BO, and the obtained oil quality was evaluated during storage in room conditions for 90 days. The AV and PV in BO without EO were lower and showed a lower increase compared to BO with EO during storage. Chlorophyll, carotenoid, thymoquinone, phytosterols and tocopherols were lower in samples without EO than those with EO. Fatty acid composition was similar in both types of oils, but linoleic acid (18:2) was decreased at a higher rate in the oil with EO during storage. Therefore, the obtained results show that steam stripping of EO from BO can be suggested to obtain oil with lower PV and AV and with a relatively longer shelf life.

Separations doi: 10.3390/separations13080223

Authors: Yu Yang Ying Fu Christopher W. K. Chow Jie Wang

Low-cost and effective F− removal technology and operational parameters were provided. A novel bimetallic fluoride-removing coagulant (BFrC) was synthesized. Simultaneous removal of fluoride (F−) and turbidity were studied using a new integrated coagulation–adsorption technology based on BFrC (BFrC-“Coagulation-driven adsorption” system (BCS)) in treating low-temperature and low-turbidity waters, in which a “Coagulation-driven adsorption” was the key point. Optimal conditions of the BCS were determined, and Zeta potential and meso- and micro-scopic morphologies were characterized. The results showed BFrC was hydrolyzed and hydroxylated to form positively charged flocs, and BCS reduced residual F− concentration to <1 mg/L. The in situ flocs formed in the BCS (BCS-flocs) gave a very large surface area, providing abundant adsorption sites and channels for F−. Neutral water environment (7.5–8) was conducive to remove F−, while neutral and alkaline conditions are beneficial for turbidity removal. The BCS exhibited strong adaptability to varying water temperatures and turbidity levels. Higher initial turbidity in test waters improved F− removal, while elevated initial F− levels linearly reduced F− removal. Divalent anions (SO42−) inhibited defluoridation more significantly than monovalent anions (Cl− or HCO3−). The BCS-flocs effectively removed F− and turbidity simultaneously, in which F- removal was achieved through adsorption on the flocs, maybe including a combination among initial chemical adsorption, subsequent physical adsorption, and complex composite adsorption, and turbidity removal mainly relied on a multi-mechanism process, including double-layer compression, charge neutralization, and sweep flocculation.

Separations doi: 10.3390/separations13080222

Authors: Bo Yang Ping Wang Wentian Li Xuanye Wei Wenqian Bi Chele Mugong Sicheng Ye Yunchong Jiang Yoshinori Yamaguchi Zhenqing Li

Capillary electrophoresis (CE) is widely used for DNA fragment analysis, but its separation performance depends strongly on the composition of the polymer sieving matrix, especially in multicapillary systems where matrix operability and reproducibility are critical. Herein, a laboratory-built multicapillary electrophoresis system was used to optimize the sieving matrix for high-throughput DNA fragment separation. The system integrated twelve fused-silica capillaries, high-voltage electrokinetic injection, fluorescence detection, and digital electropherogram acquisition. Using a 100 bp DNA ladder as the model sample, the effects of poly(ethylene oxide) (PEO), Tween 20, and glycerol on electropherogram quality were systematically investigated. PEO concentration was the dominant factor controlling the dynamic sieving network: 0.1% PEO provided insufficient separation, whereas 0.8–1.0% PEO produced clearly resolved DNA peaks. Tween 20 improved peak regularity and electropherogram quality under the tested conditions, with 0.05% providing sufficient improvement without prolonging migration time. Glycerol affected peak distribution by increasing apparent migration resistance in the polymer matrix; however, excessive glycerol slowed DNA migration and markedly extended the separation window. Considering separation quality, matrix operability, and analytical efficiency, 1.0% PEO, 0.05% Tween 20, 2.5% glycerol, 1× SYBR Gold, and 0.5× TBE were selected as the optimized sieving matrix. Under the optimized matrix, inter-capillary migration-time alignment improved the consistency of parallel capillary outputs, with corrected migration-time RSD values generally below 0.5%. The optimized formulation provides a practical basis for high-throughput CE-based DNA fragment analysis.

Separations doi: 10.3390/separations13080221

Authors: Qiang-Ying Zhang Jia-Le Chen Yuan-Ping Zeng Shi-Yu Ren Raymond Jianxiong Zeng Jun-Li Chen

Sludge-conditioning strategies are commonly optimized for filtration performance, with less attention paid to the rheological and textural properties of concentrated sludge and their relevance to low-temperature drying. Here, thermally modified drinking-water sludge (HDWS) was evaluated as a waste-derived mineral conditioner for filtration dewatering and low-temperature drying. The specific resistance to filtration (SRF) was lowest at 30% DS, whereas the 60% DS treatment reduced the moisture content to 35.66% after drying at 60 °C for 30 min, indicating that the optimum filtration condition did not deliver the best drying performance. Increasing the HDWS dosage from 0 to 60% DS reduced the Jenike shear stress from approximately 565 to 490 Pa and the apparent yield stress from approximately 670 to 380 Pa, while also decreasing adhesiveness and cohesiveness. At higher dosages, the sludge retained relatively high small-strain stiffness but exhibited lower nonlinear elastic and viscous resistance. These responses were consistent with weakened macroscopic bonding and altered deformation-dependent energy dissipation after HDWS addition. A possible contribution from mineral-particle contacts is suggested, although the underlying microstructural mechanism was not directly resolved. The 60% DS treatment shortened the time required to reach 20% water content to approximately two-thirds of that for raw sludge but reduced the cake calorific value from approximately 9.6 to 4.3 kJ g−1. HDWS, therefore, exhibited process-specific trade-offs, and its dosage should be selected according to the targeted unit operation and downstream management route rather than regarded as a single overall optimum.

Separations doi: 10.3390/separations13080220

Authors: Bo Peng Xinyan Zhang Qiuxiang Lu Zefeng Ge

The booming clean energy industry has driven the expansion of photovoltaic (PV) and lithium-ion battery (LIB) sectors, causing the accumulation of new energy solid wastes such as wind turbine blades (WTB), PV modules and LIBs. Such solid wastes exhibit prominent characteristics such as multi-layer composition, a high degree of cross-linking, and multi-component coupling, presenting both high resource value and significant recycling challenges. This paper systematically reviews the material structural characteristics, EoL attributes, and current resource utilization status of these three new energy solid wastes. Existing recycling technologies are classified into three categories based on material structural evolution and value realization pathways: structure-retaining mechanical conversion, selective component extraction, and structure-reconstruction-based full-component upcycling. Furthermore, this study further compares various recycling routes in terms of recycling depth, value creation and development potential. The analysis indicates that, in the face of the impending large-scale retirement wave, relying solely on morphological reuse or partial component extraction is inadequate to meet the demands for efficient, high-value, and low-carbon recycling. Consequently, structure-reconstruction-based full-component upcycling will emerge as a crucial development direction for the resource utilization of new energy solid wastes. This paper provides a theoretical reference for related technological research and development, process optimization, and industrial system layout.:

Separations doi: 10.3390/separations13080219

Authors: Alejandra Caluña Padilla Miguel A. Reinoso Diego Barzallo

The compositional complexity of plant-derived food matrices and the structural diversity of phenolic compounds influence sample preparation, promoting miniaturized solid-phase extraction using advanced sorbents for their determination. This critical systematic review examines these sorbents over the 2016–2025 period, organizing the analysis according to their structural platform to investigate how their architecture is associated with the reported interaction mechanisms, to interpret analytical performance in the appropriate context, and to identify methodological trends, limitations, and knowledge gaps. Through a systematic search in Scopus and the application of predefined eligibility criteria, 37 studies were selected and included in the critical narrative synthesis. The analysis primarily covered molecularly imprinted sorbents, functionalized polymeric and carbon-based platforms, and layered inorganic materials. Magnetic separation using Fe3O4 emerged as the most widely employed operational strategy across the analyzed platforms, while flavonoids and phenolic acids were the predominant target subclasses. Identified gaps include the infrequent evaluation of matrix effects, the limited formal assessment of method sustainability, and the scarce experimental validation of the relative contribution of retention mechanisms in systems involving multiple simultaneous interactions. By organizing the available evidence according to sorbent structural platform, this review provides a critical framework for interpreting analytical performance, informing the rational design of advanced sorbents, and supporting the development of miniaturized solid-phase extraction techniques for food analysis.

Separations doi: 10.3390/separations13080218

Authors: Chen Tian Yiying Gao Wenli Zhao Zaishen Ling Zhongdan Li Huabo Xie Bingxin Mao

Hydrodesulfurization (HDS) is a critical technology for producing clean petroleum products. With the steady growth in annual crude oil processing volumes, the consumption of HDS catalysts has been continuously increasing. The massive release of spent catalysts imposes significant pressure on both the environmental compliance and sustainable operation of companies. Spent HDS catalysts contain relatively high concentrations of valuable metals such as Mo, Ni, V, and Co. These materials are toxic and harmful heavy metal pollutants, yet they also constitute an important secondary resource of strategic metals with extremely high recycling value. Based on a systematic comparison of relevant recovery technologies, this paper reviews the current status of valuable metal recovery from spent HDS catalysts. It summarizes typical process routes for the full-component recovery of valuable metals and discusses future research directions, with the aim of providing a theoretical reference for the high-value resource utilization of spent HDS catalysts.

Separations doi: 10.3390/separations13080217

Authors: Iulia Varzaru Arabela Elena Untea

Natural bioactive compounds found in plants, agri-food by-products, microorganisms, marine sources, and other sustainable biological resources continue to drive scientific innovation due to their structural diversity and wide spectrum of biological activities, supporting advances in pharmaceuticals, nutraceuticals, functional foods, cosmetics, agriculture, and animal nutrition [...]

Separations doi: 10.3390/separations13080216

Authors: Chenzhe Lian Yinping Wang Jianwei Liu Qian Zhang Zhihua Gao

This study developed an analytical method based on comprehensive two-dimensional gas chromatography–mass spectrometry/flame ionization detection (GC×GC-MS/FID) for the simultaneous qualitative and quantitative analysis of phenolic compounds in coal-derived liquids. After sample injection, the analytes were first separated on a non-polar column in the first dimension and then transferred via a modulator to a medium-polar column for further orthogonal separation. The target phenolic compounds were simultaneously identified by MS and quantified by FID. By comparing the quantitative performance of the area normalization, external standard, and internal standard methods, the internal standard method was found to be more accurate and reliable. The limits of detection (LODs) for individual phenolic compounds ranged from 0.011 to 0.263 mg/L. Acceptable recoveries were obtained in spiked recovery tests using real coal tar samples, and the relative standard deviations (RSDs, n = 6) for repeatability tests met the acceptance criteria for quantitative analysis. These results demonstrate that the proposed GC×GC-MS/FID strategy enables efficient separation and reliable quantification of phenolic compounds, providing a valuable reference for the compositional analysis of complex mixtures in coal tar.

Separations doi: 10.3390/separations13080215

Authors: Barış Enez

Wastewater from textile industries that contain methylene blue poses a serious environmental problem due to its stability and toxicity. In the current study, calf starter feed (CSF), goat feed (GF), and lamb grower feed (LGF) were investigated as potential adsorbents for methylene blue removal from aqueous solutions. For structure and surface analyses of the adsorbents, EDX analysis was performed with FTIR and SEM, respectively. Parameters such as pH, adsorbent dosage, dye concentration, and time were varied, and optimum pH values of 6.0 and 7.0 were obtained for CSF and both GF and LGF, respectively. It was noted that adsorption increased with adsorbent concentration; conversely, it decreased with an increase in initial dye concentration. Among all the isotherms examined, the Langmuir isotherm yielded the best correlation, with R2 > 0.98. The maximum adsorption capacity was found to be 12.4, 11.5, and 11.01 mg g−1 for CSF, GF, and LGF, respectively. Kinetic analysis showed that the pseudo-second-order model provided the best fit to the experimental data, suggesting that adsorption may involve surface interaction processes. The findings demonstrate that commercial animal feeds can serve as alternative adsorbents for methylene blue removal and provide the first evidence of their potential application in wastewater treatment.

Separations doi: 10.3390/separations13080214

Authors: Mansour Alblaji Sultan Matar Almutairi Fahad Saad Alhodieb Saleh A. Alsanie

This study optimized supercritical fluid extraction (SC-CO2) parameters for Boswellia sacra leaves to evaluate how extraction thermodynamics influence subsequent pharmacological bioactivity. Using a multi-parametric approach, extracts obtained at 40 °C and 80 °C (100 bar) were profiled via HPLC-DAD and evaluated using in vitro antimicrobial, pancreatic lipase inhibition, and Caco-2 cell antiproliferative assays. HPLC analysis revealed that the 40 °C threshold preserved chemical diversity (17 active peaks, retaining higher caffeic acid and rutin concentrations), whereas 80 °C conditions caused severe compound degradation. Consequently, the 40 °C extracts exhibited significantly enhanced biomedical potencies over the 80 °C variants, demonstrating superior microbiostatic activity against Gram-positive bacteria and Candida albicans (MIC = 15.62 µg/mL), stronger porcine pancreatic lipase inhibition (IC50 = 17.21 µg/mL), and greater antiproliferative efficacy against human colorectal adenocarcinoma cells (IC50 = 109.47 µg/mL). Ultimately, maintaining low thermal thresholds during green extraction is critical to preserving the integrated polyphenolic architecture of B. sacra required for multi-targeted antimicrobial, anti-obesity, and anticancer therapeutics.

Separations doi: 10.3390/separations13080213

Authors: Almira A. Saparbekova Gulzhan O. Kantureyeva Alimjon D. Matchanov Ulugbek R. Togaev Amanbay J. Pirniyazov Darikha E. Kudassova Gulnur M. Kaldybekova Alina Altekey

The food industry is interested in utilizing active compounds from agri-food waste to produce healthy products and promote sustainability and resource efficiency. This study aimed to conduct a phytochemical analysis of grape pomace derived from Vitis vinifera wine grape varieties Saperavi and Cabernet Sauvignon, as well as pomegranate (Punica granatum L.) peel of the Nar-Shirin variety, which are widely processed in South Kazakhstan. The extraction processes were simple and employed water and ethanol, two food-grade solvents widely used in green extraction due to their low toxicity and compatibility with food applications.Among the extraction methods tested, aqueous–alcoholic extraction demonstrated the highest efficiency in recovering total phenolic content (TPC), yielding 225.5 ± 1.46 mg GAE/g extract from pomegranate peel, 153.9 ± 1.25 mg GAE/g extract from Cabernet Sauvignon pomace, and 98.6 ± 0.83 mg GAE/g extract from Saperavi pomace. Phenolic profiling of the aqueous–alcoholic extract was performed using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (HPLC-Q-TOF MS/MS). The total ion chromatograms revealed the presence of predominant phenolic compounds in all analyzed samples. Key identified constituents in grape pomace included kaempferol 3-O-β-D-xylofuranoside, kaempferol 3-O-β-glucopyranoside-7-O-α-rhamnopyranoside, quercetin-3-O-α-L-arabinoside, genistin, and megastigmane glycoside. In pomegranate peel, compounds such as myricetin, 5-(2Z,8Z)-pentadecadien-1-yl-1,3-benzenediol were identified for the first time. These findings highlight the rich phenolic composition of grape pomace and pomegranate peel’s extracts and support their potential as valuable sources of bioactive compounds for food, pharmaceutical, and industrial applications.

Separations doi: 10.3390/separations13080211

Authors: Bo Yang Xuanye Wei Wenqian Bi Chele Mugong Sicheng Ye Yunchong Jiang Yoshinori Yamaguchi Zhenqing Li

The rapid expansion of RNA therapeutics requires analytical methods that resolve molecular integrity, heterogeneity, and process-related impurities. Capillary electrophoresis (CE) provides direct RNA separation with low sample consumption and can be coupled with laser-induced fluorescence (LIF) or mass spectrometry (MS). This review assesses CE across RNA therapeutic development, release testing, and process analytics. We examine CE separation methods and platform formats for mRNA integrity and poly(A) tail analysis, size- and structure-related impurity profiling, circular RNA purity evaluation, RNA modification analysis by CE-MS, and aptamer discovery. We also discuss multi-capillary systems, microchip electrophoresis (MCE), automation, artificial intelligence (AI)-assisted data analysis, and bioprocess integration. CE is already highly useful for selected quality control tasks, especially mRNA integrity, poly(A) tail profiling, and circular RNA purity, but broader routine adoption requires improved sensitivity, standardization, method transfer, and regulatory acceptance.

Separations doi: 10.3390/separations13080212

Authors: Hongliang Shang Biao Wang Haotian Zhang Jianwu Zeng Zhengchang Shen

China is rich in magnetite mineral resources, but they are generally characterized by low grade, fine dissemination size, and a high content of harmful impurities. Wet low-intensity magnetic separation (WLIMS) is an important method for processing fine-grained magnetite. However, during the separation process, fine magnetite particles are prone to magnetic agglomeration, which makes it difficult for conventional WLIMS separators to achieve high-selectivity separation. To address this issue, a novel WLIMS separator based on a rotating magnetic system was developed in this investigation, and its separation characteristics were systematically investigated through a combined approach comprising CFD–DEM–FEM multiphysics coupling simulations and experimental validation. Simulation results indicate that the rotating magnetic system significantly reduces the chain length and the structural stability of magnetic agglomerates just as magnetite particles enter the magnetic field region. Furthermore, under the rotating action of the magnetic system, the magnetic chains only enclose a portion of the intergrowth minerals, while gangue minerals remain unattached, which positively contributes to improved separation selectivity. Both laboratory-scale experimental results and industrial production data indicate that, compared to the conventional WLIMS separator, the rotating magnetic system WLIMS separator achieves significantly superior separation performance. For a magnetite ore with a grade of 57.68%, the rotating magnetic system WLIMS separator achieved an optimal concentrate grade of 65.43% (with a recovery of 94.78%), whereas the conventional WLIMS separator attained only 60.32% at a similar recovery rate. This investigation provides an important basis for the large-scale industrial application of rotating magnetic system WLIMS separators and the efficient development and utilization of fine-grained magnetite resources.

Separations doi: 10.3390/separations13080210

Authors: Xia Deng Lemin Huang Yunfei Mo Xuemin Cui

Self-supported gradient bilayer NaA zeolite membranes were hydrothermally converted from geopolymer precursors for pervaporative dehydration of the propylene glycol methyl ether (PGME)/water azeotrope. XRD confirms crystallization of amorphous geopolymer into NaA zeolite. The 9 mm-thick membrane comprises a thin surface NaA-selective layer and a porous substrate providing low-resistance feed transport. The membrane shows preferential water adsorption and separates via the adsorption–diffusion mechanism. Performance depends on feed temperature and PGME concentration. At 30 °C and 95 wt% PGME, it achieves a flux of 1.1 kg·m−2·h−1 and an ultrahigh separation factor of 2695, far exceeding conventional PVA membranes. This low-cost membrane demonstrates excellent potential for lab-scale organic solvent dehydration.

Separations doi: 10.3390/separations13080209

Authors: Yuan Fang Chunjuan Zhang Wenting Song Xuefeng Guo

A preparative purification process was developed for the enrichment of four C-glycosyl flavones from leaves of Phyllostachys edulis (Carrière) J.Houz., namely orientin, isoorientin, vitexin, and isovitexin. The crude P. edulis leaf extract was used as the feed material, and HPLC was employed for quantitative analysis. Macroporous resins and polyamide resins were compared in terms of their adsorption and desorption performance toward the target compounds. The results showed that D101 macroporous resin provided the best overall process suitability among the tested resins. The optimal purification conditions were an initial sample concentration of 10 mg·mL−1, a resin-to-sample loading ratio of 5:1 (g·g−1), a sample-loading flow rate of 4 BV·h−1, impurity removal with 15% ethanol, elution with 60% ethanol, an elution volume of 3 BV, and a 60% ethanol elution flow rate of 3 BV·h−1. After D101 resin purification, the yield of the four C-glycosyl flavones was 11.712 mg·g−1 relative to the crude extract, and their combined content in the D101-purified flavonoid-enriched powder reached 68.359 mg·g−1. Further purification using polyamide resin with a particle-size range of 0.15–0.25 mm and 40% ethanol resulted in the recovery of 16.128 mg·g−1 of the four C-glycosyl flavones relative to the D101-purified feed material, while their combined content in the polyamide-purified flavonoid-enriched powder reached 76.939 mg·g−1. This process provides a basis for the preparative separation and utilization of C-glycosyl flavones from P. edulis leaves.

Separations doi: 10.3390/separations13070208

Authors: Shuling Gao Xintong Zhang Qian Wang Xiaohong Zhou Chunyu Liu Guixia Fan Daoguang Teng

The middle trough of spirals serves simultaneously as a buffer zone for variations in hydrodynamic parameters and as a region where mineral particles of different densities are prone to mixing, exerting a profound influence on particle-separation effect. This study employed a multi-fluid volume of fluid (VOF) model incorporating the Bagnold effect to simulate the ilmenite–chlorite slurry flow in a custom-designed Φ400 mm short-travel spiral concentrator with three turns. This study systematically investigated the influence of the transverse inclination angle of the middle trough (ranging from 3.5° to 9.5°) on separation indicators, flow film morphology, secondary circulation characteristics, and particle force dynamics. The results indicate that employing a lower transverse inclination angle is more conducive to improving the technical separation indicators for ilmenite and chlorite. When using enrichment ratio and separation efficiency as criteria, the optimal inclination angles range from 3.5° to 5° and 3.5° to 6.5°, respectively. Meanwhile the separation efficiency and its sensitivity to the middle trough transverse inclination angle vary remarkably with different feeding sizes. Feeding of 112 μm ilmenite and 19 μm chlorite yields the premium separation performance and is minimally affected by the middle trough transverse inclination angle. Conversely, as the ilmenite particle size decreases or the chlorite particle size increases, the separation indicators decline but become significantly regulated by the middle trough transverse inclination angle, exhibiting a desirable angle range of 3.5–6.5°. Hydrodynamic parameter analyses indicate that a moderate flow film depth, continuous secondary circulation morphology and stabilizing inner circulation in the middle trough can be obtained at a middle trough transverse inclination angle scope of 3.5–6.5°. Once the inclination angle exceeds 6.5°, a distinct ridge forms in the flow film of the middle trough, and extensive disruptions occur in the outward circulation, which subsequently impedes the outward transport of low-density particles along with the fluid. At a middle trough transverse inclination angle scope of 3.5–6.5°, the Bagnold force exerted on the ilmenite particles in the middle trough remains low during the initial stage of flow field evolution, which favors their retention in the lower fluid layer to become the concentrate product. Concurrently, the chlorite particles near the inner region experience a higher Bagnold force, which facilitates their suspension into the upper outer circulation, thereby amplifying the kinematic differences between the chlorite and ilmenite particles. This study demonstrates that fluid dynamic parameters and the force characteristics of mineral particles can effectively characterize the separation process of mineral particles in spirals.

Separations doi: 10.3390/separations13070207

Authors: Mao Maekawa Masamitsu Maekawa Yu Sato Shimpei Watanabe Masatoshi Saito Nariyasu Mano

In neonatal intensive care units (NICUs), limited vascular access often necessitates the co-administration of multiple intravenous medications through a single line, increasing the risk of physicochemical incompatibility. Doxapram hydrochloride (DOP), a respiratory stimulant used when caffeine therapy is insufficient, is continuously infused and frequently requires Y-site administration with other drugs. This study systematically evaluated the compatibility of seven commonly used NICU medications—midazolam (MDZ), dalteparin sodium (DLT), cefazolin, cefepime (CFPM), vancomycin, fosfluconazole, and famotidine—under conditions simulating co-administration through the side port of a continuous DOP infusion. Visual inspection, UV absorbance, pH measurement, and HPLC/UV analysis were performed at 0 and 3 h, with extended evaluation to 24 h for only MDZ and DLT. All mixtures showed acceptable physicochemical compatibility within 3 h, and MDZ and DLT remained stable for 24 h, indicating feasibility for co-infusion in the same syringe. In HPLC/UV analysis, the CFPM–DOP mixture exhibited a marked artifactual increase in DOP peak area, likely due to pH-dependent chromatographic behavior changing rather than true incompatibility. These findings provide practical compatibility data for NICU drug administration and offer a methodological framework for evaluating untested drug combinations, contributing to safer and more efficient intravenous therapy in preterm infants.

Separations doi: 10.3390/separations13070206

Authors: Chinemerem Ruth Ohoro Veronica M. Ngole-Jeme

Per- and polyfluoroalkyl substances (PFASs) are persistent environmental contaminants widely recognized as “forever chemicals” due to the exceptional stability of their carbon–fluorine (C-F) bonds. Their widespread occurrence in water, soil, sediments, and biota, coupled with increasing evidence of toxicity, bioaccumulation, and long-range transport, has intensified the search for sustainable remediation strategies. Conventional remediation technologies for PFASs have been widely applied but remain constrained by several technical and environmental limitations, such as incomplete mineralization, high energy requirements, secondary waste generation, and the formation of toxic transformation products. Moreover, many conventional treatment processes were not originally designed to handle the chemical stability and structural diversity of PFASs, resulting in variable removal efficiencies across different compounds. Bio-based strategies for PFAS remediation, particularly those targeting C-F bond cleavage and biological defluorination, are gaining attention due to the unique challenges posed by the chemical stability and environmental persistence of these “forever chemicals”. This review addresses the fragmented nature of PFAS remediation research by integrating biological and physicochemical strategies and critically examining mechanisms of C-F bond cleavage and defluorination. Emerging technologies, including bioelectrochemical systems, photocatalytic and electrochemical defluorination, adsorption-assisted degradation, plasma treatment, hydrothermal processes, and synthetic biology approaches, are evaluated in relation to their degradation efficiencies, defluorination capacities, and applicability in diverse environmental matrices. Particular attention is given to integrated “capture-and-destroy” systems that combine adsorption with catalytic or biological degradation to enhance remediation efficiency and reduce energy demand. PFAS treatment performance varies markedly across scalability, destruction, and cost. Key knowledge gaps and future perspectives are outlined, emphasizing the need for scalable, energy-efficient, and environmentally sustainable remediation technologies capable of achieving complete PFAS mineralization in complex environmental systems.

Separations doi: 10.3390/separations13070205

Authors: Andreas Tsakalof

Biomedical research has undergone profound changes in recent years, driven by advances in analytical technologies that enable the investigation of increasingly complex biological systems [...]

Separations doi: 10.3390/separations13070204

Authors: Linlin Yan Jinglin Hong Jialing Zhang Yanying Zhao Yuqian He Kai Wang Yuhua Gao Zongli Xie Xiquan Cheng

Membrane separation technology has been extensively applied to treat oily effluent given its high performance and ease of operation. However, conventional polymer membranes are resistant to natural degradation after use, leading to severe environmental concerns. Consequently, the development of biodegradable membranes that combine satisfactory oil–water separation performance with ecological safety has emerged as a critical research priority. In this work, we fabricated a biodegradable membrane consisting of chitosan (CS), sodium methacrylate (SMa) and polyvinyl alcohol (PVA) via electrospinning, with anionic super-hydrophilic polyacrylamide (PAM) incorporated to enhance wettability. No toxic chemicals were used throughout the fabrication process. The resulting membrane with an interpenetrating network and beaded structure not only rendered the crosslinked nanofiber more hydrophilic but also improved the porosity of membranes, which significantly enhanced the separation performance and fouling resistance of the membrane. Specifically, the CS/PVA/SMa-PAM membrane achieved a separation flux of 2.7 × 104 L·m−2·h−1·bar−1 for oil–water emulsions. After 20 emulsion separation cycles, the flux of the modified membrane was stable at 2.5 × 104 L·m−2·h−1·bar−1. Benefiting from its excellent anti-fouling properties, high separation efficiency, eco-friendly biodegradability, and toxic-reagent-free fabrication, the as-prepared CS/PVA/SMa-PAM membrane offers a promising and sustainable option for oily wastewater treatment.

Separations doi: 10.3390/separations13070203

Authors: Guangyu Zhang Weiguang Zhang Yingxuan Wang Lexuan Zhang Xuejiao Cao Yibing Li Yang Chen Yan Wang

Aiming at the bottleneck of the difficult scrubbing and separation of scandium and titanium in the solvent extraction process for scandium recovery, a novel strategy for scandium–titanium separation via citrate complex scrubbing is proposed based on the difference in complexation properties between scandium/titanium and hydroxycarboxylic acids. The mixed Na3Cit + H2O2 system was screened as the optimal scrubbing agent. The effects of key parameters including dosages of Na3Cit and H2O2 and phase ratio (O/A) on scrubbing performance were systematically investigated. The optimal process conditions were determined as follows: temperature of 25 °C, molar ratio n(Na3Cit)/n(Ti) = 30:1, molar ratio n(H2O2)/n(Ti) = 3:1, phase ratio (O/A) of 1:1, shaking speed of 200 r/min, and scrubbing time of 30 min. Under the optimal conditions, the titanium scrubbing efficiency reaches 97.37% with zero co-scrubbing efficiency of scandium. The separation efficiency is 14.47 times higher than that of the conventional H2SO4 + H2O2 scrubbing system, which significantly enhances the scandium–titanium separation performance. This work provides a feasible technical route for the deep separation and purification of scandium and titanium from titanium white waste acid.

Separations doi: 10.3390/separations13070202

Authors: Yikai Chen Zhiying Pan Hongcheng Li Shichao Du Yan Wang Fumin Xue

This study develops a spherical crystallization approach using a small amount of water, which avoids adding extra bridging agents. Notably, a new ternary solvate of pantoprazole sodium (PS–BuOH–H2O) was obtained, and its crystal structure was determined by single–crystal X-ray diffraction. The crystal packing and Hirshfeld surface analyses were performed to identify intermolecular interactions within the crystal. In the crystal lattice, water molecules not only coordinate to the sodium ion of pantoprazole sodium but also form a hydrogen bond with n-butanol via O6–H6A···O5. In order to regulate the particle morphology, the effects of crystallization conditions were investigated, including water content, feeding rate of water, solute concentration, temperature, cooling rate, and stirring rate. It was discovered that water plays a key role in promoting the spherical crystallization of PS–BuOH–H2O. In addition, the morphology of the solvate was closely related to the competition process of crystal agglomeration and spherulitic growth. By optimizing the process parameters, well–developed spherical particles could be prepared and stepwise evolution of spherulites via noncrystallographic branching was observed. This study established a water–induced spherical crystallization technique, offering a promising strategy for preparing new crystal forms and improved particle morphology.

Separations doi: 10.3390/separations13070201

Authors: Hayley Corbett Brian Solan Svetlana Tretsiakova-McNally Pilar Fernandez-Ibañez Bárbara Luíza Souza Freitas Rodney McDermott

The intensifying rate of global water stress is motivating the exploration of alternative water sources. This research aims to unlock conventionally unusable wastewater effluent for reuse with the aid of slow sand filtration (SSF). In this study, a traditional SSF reactor was constructed and later modified by replacing a section with sawdust, a sustainable material. The two filter configurations were asynchronously investigated to evaluate their potential capacity for the removal of antibiotics and common surface-water nutrients, i.e., nitrates and phosphates. Each filtration system was operated in a recirculating mode over four weeks to develop the biological component referred to as the “schmutzdecke”. Standard water-quality testing indicated that the SSF with an incorporated sawdust layer buffered shock events (e.g., turbidity spikes) while still cultivating a healthy schmutzdecke. Furthermore, the sawdust facilitated greater microbial activity, which is associated with the biodegradation of various contaminants and pathogens. Following filtration of a simulated wastewater effluent containing sulfamethoxazole (SMX) and trimethoprim (TMP) antibiotics (ca. 1 mg∙L−1), it was found that the TMP removal exceeded 93% in both configurations. The SMX removal rate was much lower and varied significantly, ranging from 1.2 to 38.6% and from 1.4 to 3.4% for the traditional and modified filters, respectively. These findings suggest that the proposed configuration has the potential to address some emerging contaminants but that refinements are needed to address other contaminants such as SMX.

Separations doi: 10.3390/separations13070200

Authors: Ying Yang Xiaofei Xie Jingchang Zhang Jirui Sui Chuancheng Lin Mingxing Li Weixue Liu Chunying Li Chunjian Zhao

Chlorogenic acid (CA) is an important natural antioxidant component and holds strong potential for health food and cosmetic applications. In this study, a silica-based photo-responsive molecular imprinting material (PMI-PDA@NH2-SiO2) was designed as a solid-phase extraction (SPE) adsorption filler and applied for the efficient separation of CA in Ficus carica L. Using polydopamine-modified NH2-SiO2 silica as the base, combined with the photo-responsive monomer 4-methacryloyloxyazobenzene (AZO-MAA), a molecular imprinting layer with photo-responsive regulation function was constructed. Under 365 nm ultraviolet light irradiation, the azobenzene group was isomerized to the cis structure, causing the imprint cavity to shrink, thereby enabling controlled release of CA, with complete desorption within 40 min, and a desorption rate of 94.33%. Importantly, the material retained 85.56% of its initial adsorption capacity and 91.38% of its original desorption efficiency after 6 consecutive adsorption/desorption cycles, confirming robust operational stability and reproducibility. PMI-PDA@NH2-SiO2 was applied to the extract of Ficus carica L., achieving an adsorption rate of 92.3% for CA and a desorption rate of 87.27%. Density functional theory (DFT) calculations and NOESY spectroscopic analyses revealed that CA interacted with functional monomers via hydrogen bonding and van der Waals forces. This study advances a green separation strategy for bioactive phytochemicals in complex natural matrices.

Separations doi: 10.3390/separations13070199

Authors: Zilong Liu Jiawei Wang Shuyuan Zhu Shangyi Li

With the widespread application of new chemicals, the concentration of emerging contaminants (ECs), such as antibiotics, per- and polyfluoroalkyl substances (PFAS), microplastics, and new pesticides, in aquatic environments is on the rise. ECs such as those examined in the studies exhibit high toxicity, persistence, and a propensity for bioaccumulation, which can lead to significant risks for ecosystems and human health. Traditional water treatment technologies exhibit limited removal capabilities for ECs, whereas micro-nano bubbles (MNBs) exhibit great potential in the field of ECs treatment, due to their unique physicochemical properties. This article systematically reviews the research progress on the treatment of ECs using MNBs combined with other technologies, including physical methods (adsorption enhancement), chemical methods (ozonation, persulfate oxidation, photocatalysis, and material catalysis) and biological methods (microbial synergy). This review summarizes the research progress and mechanisms of MNBs combination technologies, outlining the critical knowledge gaps and future research perspectives to advance the rational design and engineering application of MNBs for ECs’ elimination in water treatment.

Separations doi: 10.3390/separations13070198

Authors: Haicheng Zhao Lihui Gao Xinmeng Jiang Yijing Zhang

Coal gasification slag (CGS), a massive industrial solid waste, possesses inherent adsorptive potential that remains underutilized due to pore blockage by amorphous siliceous phases. Conventional modification strategies typically rely on energy-intensive high-temperature processes. Herein, we report a facile, low-temperature alkaline activation approach to transform CGS into a high-efficiency adsorbent (denoted NCGS) for Cd2+ removal. Sodium hydroxide (NaOH) solution was employed under mild conditions (90 °C) to selectively etch siliceous species, thereby generating a porous architecture and enriching surface oxygen-containing functionalities. Orthogonal experimental design identified optimal synthesis parameters (1 mol/L NaOH, solid–liquid ratio of 1:30 g/mL, 12 h), yielding NCGS with significantly enhanced textural properties. The adsorption isotherm was well described by the Langmuir model, with a maximum capacity of 87.06 mg/g at pH 6.0, while kinetic studies indicated the adsorption process could be described by pseudo-second-order kinetic model. Comprehensive characterization via SEM-EDS, FTIR, and XPS elucidated a multi-mechanistic adsorption pathway mainly involving ion exchange (Na+/Cd2+) and coordination complexation. Life cycle assessment analysis revealed that NCGS production generates 11.23 kg CO2 eq emissions, with transportation accounting for 88%. This study presents an energy-saving and environmentally friendly strategy to unlock the adsorptive potential of CGS, providing a highly promising waste-based adsorption material for the remediation of Cd2+-contaminated water.

Separations doi: 10.3390/separations13070197

Authors: Zhuowen Feng Jieshan Wu Tingwei Huang Liang Pan Yue Zhao Yun Cui Shiwei Ren Abderrahim Yassar

An analytical method was established for the rapid determination of 45 pigments and preservatives in edible ink by ultra-high performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry (UHPLC-MS/MS), which provides technical support for the composition analysis and industrial development of edible ink. The samples were easily extracted with 75% aqueous methanol solution and purified with a Captiva EMR-Lipid HF solid-phase extraction cartridge. After filtration through a polytetrafluoroethylene (PTFE) membrane, the analytes were determined by UHPLC-MS/MS under multiple reaction monitoring (MRM) mode in both positive and negative ion modes. Poroshell 120 AQ-C18 was selected as the analytical column, and valve switching timing control was adopted during the gradient elution process. The external standard method was used for quantitative analysis. In the established method, the 45 pigments and preservatives exhibited good linear relationships within the mass concentration range of 0.0002–200.0 μg/mL. The limits of detection (LOD) and limits of quantification (LOQ) were 0.0004–8.00 mg/kg and 0.001–20.00 mg/kg, respectively. Using 25% aqueous glycerol solution as the blank matrix, the recoveries of analytes at different spiked levels met the detection requirements. The established method is simple and rapid, and can be applied to the qualitative and quantitative detection of typical pigments and preservatives in edible ink.

Separations doi: 10.3390/separations13070196

Authors: Guoqiang Liang Chenpeng Wang Qianwei Ji Xusheng Zhang Liang Zhao Xinchun Liu Zhisheng Yu Hongxun Zhang Guoqiang Zhuang Jianzhong Zheng Ruyin Liu

Facing the severe environmental challenge of massive red mud (RM) stockpiles, iron extraction research is accelerating from traditional pyrometallurgy and other conventional processes toward green low-carbon, multi-source synergistic, and total-component high-value utilization approaches—a transition that continues to evolve. This review systematically examines three frontiers: green reduction technologies, synergistic valorization via waste-treating-waste, and integrated cascading strategies for total-component high-value utilization. Evaluation focuses on the principles, advantages, and challenges of biomass reduction, hydrogen metallurgy, selective flocculation, advanced heating techniques, co-processing with other solid wastes, and multi-metal cascading extraction. Evidence suggests that future RM iron extraction technology lies in establishing cross-industry circular economy networks, transforming RM from a singular waste into a resource hub linking aluminum, steel, and construction industries to maximize environmental and economic benefits.

Separations doi: 10.3390/separations13070195

Authors: Rosella Prestia Damian Hauri Mattia Sponchioni Sebastian Vogg Thomas Müller-Späth

Peptide purification by preparative reversed-phase liquid chromatography remains one of the most resource-intensive stages in synthetic peptide manufacturing. Production processes commonly rely on acetonitrile/trifluoroacetic acid (ACN/TFA) mobile phases mainly because of their high chromatographic resolution. However, both components raise significant environmental and safety concerns related to toxicity, flammability, waste generation, and, in the case of TFA, environmental persistence as a per- and polyfluoroalkyl substance (PFAS, known as a “forever chemical”). Green alternatives based on ethanol, dimethyl carbonate, and sustainable acidic additives such as acetic acid have been proposed, but their industrial adoption remains limited due to reduced chromatographic performance, often resulting in lower yield and productivity under conventional batch operation. In this work, multi-column counter-current solvent gradient purification (MCSGP) was investigated as a strategy to integrate the use of green eluent systems without compromising process performance. Two therapeutic peptides, Tirzepatide and Tetracosactide, were selected as representative case studies with different structural complexity. Using ethanol/acetic acid for Tirzepatide and dimethyl carbonate/acetic acid for Tetracosactide, the MCSGP process achieved purity levels equivalent to those obtained with conventional ACN/TFA batch chromatography, with 88.1% yield at 89.0% purity for Tirzepatide and 93.8% yield at 94.0% purity for Tetracosactide. Productivity for Tirzepatide was improved, reaching 6.3 g/Lresin/h. These results demonstrate that MCSGP can compensate for the reduced separation efficiency typically associated with green eluent systems, enabling sustainable peptide purification without compromising process performance. By combining green solvents with the MCSGP process, this work paves the way for more sustainable peptide purification processes while maintaining high yield and productivity.

Separations doi: 10.3390/separations13070194

Authors: Xin-Wen Huang Xiang Li Yi-Jing Lang Ran-Xu Song Jing-Jing Ren Yan-Hua Xie Hui-Min Xiao Si-Wang Wang

To establish a comprehensive quality control method for Qili Qiangxin Capsules, an HPLC-DAD-ESI-MS/MS approach was developed for characteristic chromatogram analysis, marker compound identification, and multi-compound quantification. Similarity analysis of the characteristic chromatogram was conducted, and 25 characteristic peaks were identified using MS/MS fragment information. Methodological validation (specificity, linearity, precision, stability, repeatability, spiked recovery) was performed, followed by content determination of the 25 marker compounds. Results showed that the similarity of 10 batches of samples was >0.9 (Peak 6 as reference peak). The methodological validation for the quantitative analysis of 25 compounds met the requirements. All 25 compounds exhibited good linearity (R2 > 0.999), with spiked recoveries of 98–103% (RSD < 2.0%). All validation indicators met Chinese Pharmacopoeia requirements. The established method is specific, precise, and stable, enabling simultaneous characteristic chromatogram identification and multi-compound quantification of Qili Qiangxin Capsules. It provides technical support for production quality supervision and clinical medication safety, and offers a reference for quality control of similar traditional Chinese medicine preparations.

Separations doi: 10.3390/separations13070193

Authors: Zi-Ying Zeng Cheng-Xiang He Qin Tian Jun Long Bing-Yan Du Er-Cheng Zhao Zhong-Hua Yang

The increasing prevalence of multiclass pesticide residues in aquatic environments poses a significant threat to ecosystems and human health. To address this challenge, magnetic Fe3O4@Co5Al-LDH nanoparticles were synthesized as high-performance, easily recoverable catalysts for the peroxymonosulfate (PMS)-mediated degradation of epoxiconazole, atrazine, and metalaxyl. Under optimized conditions (pH 7.0, 35 mg catalyst, and 4.0 mM PMS), the system achieved 100% degradation of the three coexisting pesticides within 15 min. Quenching experiments and electron paramagnetic resonance (EPR) spectroscopy confirmed that SO4− and •OH radicals were the primary reactive species driving the process. Liquid chromatography–mass spectrometry (LC-MS) analysis identified four intermediates for epoxiconazole, three for atrazine, and four for metalaxyl, facilitating the proposal of distinct degradation pathways. The degradation mechanism revealed that electron transfer between Fe/Co and PMS promoted the generation of reactive oxygen species, leading to dechlorination, hydroxylation, and dealkylation of the pesticides transiently adsorbed on the surface of Fe3O4@Co5Al-LDH. In summary, this study demonstrates that Fe3O4@Co5Al-LDH is an easily recoverable, reusable, and cost-effective catalyst for the simultaneous remediation of complex pesticide mixtures in water.

Separations doi: 10.3390/separations13070192

Authors: Yao Zhang Yong Yu Zhi-Bin Zhou Zheng-Hao Yang Yu-Long Chang Li-Wang Wang Ben-Shuai Guo

The complex behavior of multi-scale droplets in Hydro-jet Cyclone (HJC) systems constrains the parametric study of gas–liquid separation and interfacial transfer. To investigate droplet dynamics at a specific scale in swirling flows, this study employed 500-μm simulated droplet particles (SDPs) and examined the effects of inlet gas rate, column height, and cone angle on trajectories, revolution speed, and self-rotation speed using the Computational Fluid Dynamics-Discrete Phase Model (CFD-DPM). The results demonstrate that SDPs exhibit suspended circulation within the cyclone. The suspension zone expands toward the overflow pipe with increasing gas rate and cone angle, but migrates downward with increasing column height. The revolution speed increases from about 50 rad/s to 80 rad/s as inlet gas rate rises, but decays with increasing column height, while cone angle has little influence. The self-rotation speed is driven by near-wall shear, reaching an instantaneous peak of 4500 rad/s at the inlet; after stable suspension, it increases markedly with gas rate, from <3500 rad/s at 12 m/s to 12,000 rad/s at 22 m/s. Inlet gas rate is the dominant factor governing self-rotation, followed by cone angle, whereas column height mainly affects suspension position. This study provides a numerical reference for droplet dynamics in HJC gas–liquid systems.

Separations doi: 10.3390/separations13070191

Authors: Qiyuan Wei Yanru Cui Hongqiong Zhang Jianbo Li

Coal plays a vital role in energy production, but its combustion releases SO2, causing serious environmental problems. In this study, indigenous microorganisms with sulfur-metabolism potential were isolated from raw coal and evaluated for coal biodesulfurization. The isolated strain, Arthrobacter sp. DBW, degraded 50% of DBT within 100 h and reduced the total sulfur content of coal by 42%. Since pyrite remained after treatment, the sulfur removal was mainly attributed to organic sulfur removal. Mechanistic analysis indicated that Arthrobacter sp. DBW may remove organic sulfur through enzyme binding to DBT and subsequent C-S bond cleavage via the 4S pathway. In addition, partial kaolinite dissolution occurred during biodesulfurization, reducing the ash content by 1.06%. These results suggest that Arthrobacter sp. DBW has potential for organic sulfur removal from coal and may help reduce SO2 emissions during subsequent combustion.

Separations doi: 10.3390/separations13070190

Authors: Nianzi Liu Yilin Wang Qing Long Anyan Long Guihua Liu Tiangui Qi Qiusheng Zhou Leiting Shen Jian Guo

Secondary aluminum dross (SAD) from the aluminum industry is a hazardous residue that restricts sustainable aluminum production. Residual aluminum nitride (AlN) and insoluble fluorides after conventional pretreatment are major barriers to the safe utilization of SAD. In this study, a low-temperature intensified roasting–alkaline leaching process was developed to remove harmful elements by using reaction heat and waste heat to expose enveloped AlN and fluoride phases, form soluble sodium-bearing compounds, and intensify AlN oxidation. Without additives, roasting at 750 °C for 3 h converted 91.65% of AlN, leaving 1.37% AlN in the roasted SAD. With Na2O2 as an oxygen donor in situ, NaF as a mineralizer to reduce roasting temperature, and sodium-bearing species as reactants for soluble NaAlO2/Na2SiO3 formation, the AlN conversion increased up to 97.01% under 5% NaF and 2.5% Na2O2 at 750 °C for 3 h. Afterwards, higher temperature, longer duration, lower roasted SAD dosage, and higher caustic soda concentration all improved fluorine removal in the subsequent alkaline leaching. Under 100 g/L Na2O, 20 g/L roasted SAD, and 100 °C, fluorine and chlorine removal efficiencies reached 92.52% and 99.47%, respectively. The final high-alumina residue contained 74% Al2O3, mainly in the forms of α-Al2O3, NaAl11O17, and MgAl2O4, with only 0.19% F and 0.03% Cl, making it suitable for the preparation of various alumina-bearing materials and alumina production.

Separations doi: 10.3390/separations13070189

Authors: Jieru Zhang Ying Yang Xiaoming Peng

Ionic liquid-assisted extraction can improve the recovery of monoterpene glycosides from Radix Paeoniae Alba, whereas post-extraction purification and ionic-liquid-associated marker-level quality control remain necessary before further bioactivity evaluation. In this study, a macroporous resin-based purification process was developed for monoterpene glycoside-enriched extracts obtained by conventional reflux extraction and ionic liquid-assisted microwave–ultrasound extraction. Among the five tested resins, AB-8 resin showed the best adsorption performance and was selected for further process optimization. The optimized purification conditions were a loading concentration of 13 mg/mL, loading pH of 7, elution with 70% ethanol, loading volume of 6 BV and elution volume of 9 BV. After purification, the total quantified monoterpene glycoside content increased from 6.59% to 51.68% in the conventional extract and from 15.30% to 75.30% in the ionic liquid-assisted extract. The ionic-liquid-associated elemental marker content in the ionic liquid-assisted extract decreased from 5.593% to 0.072% after purification, corresponding to an approximately 98.7% reduction at the elemental-marker level. Stability evaluation indicated that Na2SO3, Fe3+, ascorbic acid, sucrose and light exposure affected the detected monoterpene glycoside content to different extents, whereas short-term heating within 20–80 °C caused only slight fluctuations. The purified extracts showed stronger DPPH and ABTS radical scavenging activities and reducing power than the crude extracts. In LPS-stimulated RAW264.7 cells, the purified extracts reduced NO production and downregulated the mRNA expression of IL-6, IL-1β, TNF-α, iNOS and COX-2, suggesting anti-inflammatory potential at the NO and gene-expression levels. AB-8 resin purification enriched the monitored monoterpene glycosides, reduced the selected ionic-liquid-associated elemental marker, and generated purified fractions suitable for subsequent stability and bioactivity evaluation.

Separations doi: 10.3390/separations13070188

Authors: Petr Česla Václav Kašička

Research in the analytical and preparative fields of separation science has a long-standing tradition in the Czech Republic and former Czechoslovakia. Czech and Slovak scientists recognized the advantages of the two most widely used separation techniques, i.e., chromatography and electrophoresis, soon after their discovery and broader adoption. Their contributions to the development of the fundamentals and applications of chromatography and electrophoresis are demonstrated not only by numerous publications in renowned scientific journals and books, but also by several breakthrough innovations that led to patents and sometimes also to successful commercialization. The contributions of the earlier most prominent Czech scientists to the development of separation sciences have already been summarized in the literature. In the following lines, we instead aim to highlight less well-known, yet important, contributions within the Czech chromatographic and electrophoretic community. Moreover, recent developments since the last comprehensive reviews are covered in greater depth.

Separations doi: 10.3390/separations13070187

Authors: A K M Ahsan Ahmed Douglas E. Raynie

This study investigated the effect of ethanol on the relative headspace percent composition of evaporative emissions from gasoline at different temperatures using HS-SPME-GC-MS. The results showed that the relative abundance of monoaromatics in the headspace decreased with increasing ethanol content in all tested fuels at all temperatures examined. The paraffins and i-paraffins exhibited a similar decreasing trend in most samples, with reductions more pronounced in E20 (20% ethanol content) than in E10 (10% ethanol content) fuels. The experimental results for the temperature effect on headspace composition were variable: monoaromatics showed slight increases at higher temperatures, whereas paraffins, iso-paraffins, and mononaphthenes generally decreased. However, ethanol addition did not significantly alter these temperature-dependent trends, as similar patterns were observed in both ethanol-blended and ethanol-free fuels. The magnitude of the ethanol effect depended on fuel composition, with the largest reductions in monoaromatic hydrocarbons observed for the high-density gasoline samples. These findings demonstrate that ethanol modifies the relative distribution of hydrocarbon classes in gasoline headspace, with the most pronounced effect being a reduction in monoaromatic hydrocarbons, and highlight the value of class-resolved analysis for understanding fuel evaporation behavior.

Separations doi: 10.3390/separations13070186

Authors: Zhe Wang Hongquan Jing Bingbing Liu Yixuan Zhang Jiangli Li Cuihong Hou

Phosphate tailings (PTs), a solid waste generated from phosphate flotation, are a low-grade phosphate resource rich in quartz and dolomite. Their long-term accumulation leads to both resource loss and environmental risks, making valorization increasingly important for the sustainable development of the phosphorus chemical industry. In this study, calcareous–magnesian PTs were used as raw materials, and selective hydrothermal leaching with weakly acidic AlCl3 solution was employed to separate the dolomite phase and directly construct a Ca-Mg-Al precursor solution for layered double hydroxides (LDHs). The LDHs were subsequently synthesized by co-precipitation and evaluated for phosphate removal from wastewater. The results showed that the precipitation pH markedly affected the phase composition and platelet morphology of the LDHs, while appropriate aging conditions further improved their adsorption performance. Under the optimal conditions of pH 12, aging at 40 °C for 2 h, the obtained LDHs exhibited the best phosphate uptake. Adsorption kinetics followed the pseudo-second-order model, and the maximum adsorption capacity calculated from the Langmuir model reached 38.61 mg-P/g. Characterization by XRD, FTIR, TG-DTA, point of zero charge, and XPS indicated that phosphate removal was dominated by surface complexation, accompanied by anion exchange, ionic precipitation, and electrostatic attraction.

Separations doi: 10.3390/separations13070185

Authors: Sheng Li Yaying Wang Lidan Lv Lingyuan Liao

212Pb is an important medical radionuclide for targeted alpha therapy, and its reliable supply depends on the efficient production of parent nuclides such as 228Ra, 228Th, and 224Ra. Natural thorium resources are abundant and represent a potential source of these radionuclides. However, the separation and enrichment of trace radium from thorium-rich high-salinity systems remain challenging due to extremely low radium concentrations and Th/Ra mass ratios on the order of 109. In this work, a radium separation strategy based on BaSO4 co-precipitation was developed. The precipitation behavior of BaSO4, precipitation kinetics, radium co-precipitation efficiency, and thorium recovery in concentrated thorium nitrate solutions were systematically investigated. The results show that elevated ionic strength and competitive interactions between Th4+ and SO42− reduce the effective sulfate activity under high-thorium conditions, making excess sulfate necessary to achieve efficient BaSO4 precipitation. Under optimized conditions, the radium co-precipitation recovery exceeded 80% at a Ba2+ concentration of 3 mM. Meanwhile, thorium exhibited negligible incorporation into the BaSO4 phase and could be almost completely recovered via subsequent hydroxide precipitation. The proposed method features operational simplicity, use of common reagents, low cost, and compatibility with high-salinity matrices. It provides a feasible technical pathway for the subsequent production of high-purity 228Th or 224Ra and the preparation of 228Th/212Pb or 224Ra/212Pb generator systems.

Separations doi: 10.3390/separations13060184

Authors: Ioannis P. Gerothanassis

Qualitative and quantitative analysis of complex mixtures and structure elucidation is generally impeded by the intrinsic complexity of the NMR spectra and the extensive signal overlap. The conventional approach to characterizing individual metabolites from complex crude extracts of natural products relies on multistep separation workflows employing diverse liquid chromatographic approaches and/or hyphenated techniques, which combine online integration of NMR with separation methods and other forms of spectroscopy. In recent decades, considerable efforts have been devoted to NMR applications in crude extracts without previous separation and isolation of the individual analytes. We present herein a critical overview of several NMR applications using chemical shift ranges of common organic functional groups, which can provide significant resolution advantages under specific experimental conditions. Particular emphasis is placed on: (i) characteristic chemical shift regions of strongly deshielded phenol OH groups, aldehyde CHO groups, hydroperoxide C-O-O-H groups and olefinic protons in conjugated double bonds; (ii) the advantages of using 13C chemical shift ranges through 2D 1H-13C HSQC and HMBC experiments of strongly deshielded phenol OH groups, aldehyde CHO groups, hydroperoxide groups, conjugated double bonds, and deshielded aliphatic CH groups; (iii) selective 1D NMR-spin chromatography techniques (1D TOCSY, 1D NOE); (iv) multiple suppression of strong resonances for minor analyte identification and (v) band-selective excitation techniques for minor analyte identification and quantification. The complementary contributions of statistical heterospectroscopy and computational chemical shift prediction are also considered, together with a brief assessment of the NMR experimental parameters and performance characteristics.