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Separations, Volume 12, Issue 9 (September 2025) – 3 articles

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21 pages, 3021 KiB  
Article
Alkali-Resistant Ion-Imprinted Chitosan–Mesoporous Silica Composite for Efficient and Selective Gallium Separation
by Zhifang Lv, Shiqiao Yang, Jiangyan Wu, Guixia Fan, Guosheng Li, Yijun Cao, Peng Li and Daoguang Teng
Separations 2025, 12(9), 226; https://doi.org/10.3390/separations12090226 (registering DOI) - 24 Aug 2025
Abstract
Efficient and selective separation of gallium (Ga(III)) from alkaline industrial waste streams remains a significant challenge due to the coexistence of chemically similar ions such as Al(III) and V(V). In this study, a novel ion-imprinted chitosan-based adsorbent (CS/(H-CGCS)-Ga-IIP) was synthesized via a hybrid [...] Read more.
Efficient and selective separation of gallium (Ga(III)) from alkaline industrial waste streams remains a significant challenge due to the coexistence of chemically similar ions such as Al(III) and V(V). In this study, a novel ion-imprinted chitosan-based adsorbent (CS/(H-CGCS)-Ga-IIP) was synthesized via a hybrid cross-linking strategy using glutaraldehyde and siloxane-modified chitosan. The optimized material exhibited a high adsorption capacity of 106.31 mg·g−1 for Ga(III) at pH 9, with fast adsorption kinetics reaching equilibrium within 60 min. Adsorption behavior followed the pseudo-second-order kinetic and Langmuir isotherm models, and thermodynamic analysis indicated a spontaneous and endothermic process. In simulated Bayer mother liquor systems, the material demonstrated outstanding selectivity and a distribution coefficient ratio kd-Ga/kd-Al = 146.9, highlighting its strong discrimination ability toward Ga(III). Mechanistic insights from SEM-EDS, FTIR, and XPS analyses revealed that Ga(III) adsorption occurs via electrostatic interaction, ligand coordination, and structural stabilization by the siloxane network. The material maintained good adsorption performance over three regeneration cycles, indicating potential for reuse. These findings suggest that CS/(H-CGCS)-Ga-IIP is a promising candidate for the sustainable recovery of gallium from complex alkaline waste streams such as Bayer process residues. Full article
(This article belongs to the Special Issue Solid Waste Recycling and Strategic Metal Extraction)
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16 pages, 1544 KiB  
Article
Chemistry and Diversity of Nitrogen-Containing Metabolites in Heliotropium procumbens: A Genus-Wide Comparative Profile
by Kalliopi-Maria Ozntamar-Pouloglou, Evgenia Panou, Tomasz Mroczek, Nikola Milic, Konstantia Graikou, Christos Ganos, Nikolas Fokialakis, George-Albert Karikas and Ioanna Chinou
Separations 2025, 12(9), 225; https://doi.org/10.3390/separations12090225 (registering DOI) - 24 Aug 2025
Abstract
Heliotropium procumbens, a Boraginaceae species native to Panama, has remained largely unexplored regarding its nitrogen-containing metabolites, including pyrrolizidine alkaloids (PAs). In the current study, a comprehensive phytochemical investigation of its aerial parts is presented using HPLC-DAD-IT-MS, UHPLC–HRMS, and GC-MS primarily to profile [...] Read more.
Heliotropium procumbens, a Boraginaceae species native to Panama, has remained largely unexplored regarding its nitrogen-containing metabolites, including pyrrolizidine alkaloids (PAs). In the current study, a comprehensive phytochemical investigation of its aerial parts is presented using HPLC-DAD-IT-MS, UHPLC–HRMS, and GC-MS primarily to profile its PA composition. A total of twelve PAs and N-oxides (PANOs) were identified, along with two phenolamides—including N1, N10-diferuloylspermidine, which is biosynthetically related to PAs—and the distinctive metabolite heliotropamide. The detected PAs included unsaturated necines, primarily monoesters of retronecine and heliotridine, as well as saturated PAs such as a platynecine-type PA and the less commonly encountered triol necines and their N-oxides. Among these, helifoline-N-oxide was isolated and structurally elucidated by NMR spectroscopy for the first time as a natural product. Comparison with the chemodiversity of PAs within the Heliotropium genus revealed a high degree of diversity in H. procumbens, which can be attributed both to the species’ inherent biosynthetic capacity for chemical variation and to the more comprehensive and extensive studies conducted on it, which naturally enrich the apparent diversity observed. This work expands the phytochemical knowledge of H. procumbens and contributes to a broader understanding of PA diversity in the genus, offering new insights into their potential ecological and toxicological significance. Full article
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15 pages, 2314 KiB  
Article
Techno-Economic Assessment (TEA) of a Minimal Liquid Discharge (MLD) Membrane-Based System for the Treatment of Desalination Brine
by Argyris Panagopoulos
Separations 2025, 12(9), 224; https://doi.org/10.3390/separations12090224 (registering DOI) - 23 Aug 2025
Abstract
Desalination plays a critical role in addressing global water scarcity, yet brine disposal remains a significant environmental challenge. This study evaluates a minimal liquid discharge (MLD) membrane-based system integrating high-pressure reverse osmosis (HPRO) and membrane distillation (MD) for brine treatment, with a focus [...] Read more.
Desalination plays a critical role in addressing global water scarcity, yet brine disposal remains a significant environmental challenge. This study evaluates a minimal liquid discharge (MLD) membrane-based system integrating high-pressure reverse osmosis (HPRO) and membrane distillation (MD) for brine treatment, with a focus on the Eastern Mediterranean. A techno-economic assessment (TEA) was conducted to analyze the system’s feasibility, water recovery performance, energy consumption, and cost-effectiveness. The results indicate that the hybrid HPRO-MD system achieves a high water recovery rate of 78.65%, with 39.65 m3/day recovered from MD and 39 m3/day from HPRO. The specific energy consumption is 23.2 kWh/m3, with MD accounting for 89% of the demand. The system’s cost is USD 0.99/m3, generating daily revenues of USD 228 in Cyprus and USD 157 in Greece. Compared to conventional brine disposal methods, MLD proves more cost-effective, particularly when considering evaporation ponds. While MLD offers a sustainable alternative for brine management, challenges remain regarding energy consumption and the disposal of concentrated waste streams. Future research should focus on renewable energy integration, advanced membrane technologies, and resource recovery through brine mining. The findings highlight the HPRO-MD MLD system as a promising approach for sustainable desalination and circular water resource management. Full article
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