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Search Results (691)

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Keywords = Al2O3-MgO-CaO

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48 pages, 65093 KB  
Article
A Precambrian Rare-Metal Granite Dike as a Natural Experiment: Constraints on Extraction and Quenching at the Melt-Hydrothermal Transition (Salmi Batholith, Karelia, Russia)
by Artem A. Konyshev, Yana O. Alferyeva, Ekatherina N. Sokolova and Vasily D. Shcherbakov
Minerals 2026, 16(9), 923; https://doi.org/10.3390/min16090923 - 7 Sep 2026
Abstract
This work is devoted to the investigation of rare-metal granites associated with anorthosite–rapakivi granite rock complexes. This article evaluates the physicochemical conditions that governed the formation of a rare-metal granite dike. It also explores assumptions regarding the geological characteristics of the magmatic chamber, [...] Read more.
This work is devoted to the investigation of rare-metal granites associated with anorthosite–rapakivi granite rock complexes. This article evaluates the physicochemical conditions that governed the formation of a rare-metal granite dike. It also explores assumptions regarding the geological characteristics of the magmatic chamber, describes evidence for liquid immiscibility, and addresses the post-entrapment evolution of hydrosilicate liquids. In addition, new mineralogical data are presented. The methods employed include optical and electron microscopy, Raman spectroscopy, secondary ion mass spectrometry, laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS), melt inclusion homogenisation experiments, and fluid inclusion study. The investigated granitic dike formed under low pressure (60–110 MPa) and temperatures of about 580–600 °C, from a specific volatile-saturated magma rich in H2O (up to 16.76 wt% in quenched hydrosilicate liquid products) and in F (up to 4.16 wt%) and Li (up to 3804 ppm), as indicated by homogenised melt inclusions. At the time of emplacement, a silicate melt, a probable Ca-fluoride melt, an Mg-Fe Al-Si-rich hydrosilicate liquid (either mutually soluble with or mixed with the inferred Ca-fluoride melt), and an essentially aqueous fluid coexisted. Depolymerisation of the silicate melt and the presence of complex ions probably promoted the dissolution and transport of high field strength elements (HFSE) and large ion lithophile elements (LILE) elements by the Mg-Fe Al-Si-rich hydrosilicate liquid. During the final stage of evolution of the granitic magmatic system, Mg behaved incompatibly because of its negligible partitioning into mica; rather than accumulating in the silicate melt, it entered the hydrosilicate liquid as a major component. The residual silicate melt consequently attained even lower Zr/Hf, Nb/Ta, and Y/Ho ratios than the studied rock. Full article
(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)
29 pages, 8778 KB  
Article
Parametric Optimization of Organic Waste Removal Using Agro-Food Carbon–Zeolite Adsorbents
by Vasiliki Anastasia Giota, Sofia Papadopoulou, Zacharias Ioannou, Georgios Skoulatakis, George Kiouranakis and Dimitris Sarris
Clean Technol. 2026, 8(5), 147; https://doi.org/10.3390/cleantechnol8050147 - 7 Sep 2026
Abstract
The production of carbonaceous materials from agro-food byproducts, i.e., olive stone and molasses alone or in combination with aluminosilicate minerals, i.e., zeolite, was investigated. Two different dyes, i.e., methylene blue (MB) and C-phycocyanin (C-PhC) contained in Spirulina extract, were used for the examination [...] Read more.
The production of carbonaceous materials from agro-food byproducts, i.e., olive stone and molasses alone or in combination with aluminosilicate minerals, i.e., zeolite, was investigated. Two different dyes, i.e., methylene blue (MB) and C-phycocyanin (C-PhC) contained in Spirulina extract, were used for the examination of the adsorptive properties of the materials. The combination of the Brunauer–Emmett–Teller surface area, X-ray diffraction, and X-ray photoelectron spectroscopy provides a comprehensive profile of composite sorbents. Several key factors, including initial dye concentration, pH, contact time, temperature, and sorbent, were investigated. All the produced adsorbents have shown a highly disordered carbon structure with specific surface areas between 16 and 1211 m2/g. The elemental composition analysis revealed the presence of C-C, C-H, C-O, C=O, O-C=O, and (CO3)2− bonds during high-resolution C1s and O1s deconvolution and detected the elements Al, Si, Na, Ca, K, Na, and S, confirming the aluminosilicate framework of the zeolitic structure of the materials. The examined conditions showed the best MB and C-PhC adsorption results at pH 8, temperatures of 50 °C and 40 °C, respectively, an initial concentration of 0.5 mg/L for MB and 32 mg/L for Spirulina extract (SE), and a sorbent dosage of 2.0 g/L C/MB or SE solution. The adsorbents produced were applied to the removal of C-PhC from industrial waste. To conclude, this research underscores the viability and high efficiency of repurposing agricultural waste into carbonaceous composite sorbents to eliminate dyes from wastewater. Full article
(This article belongs to the Special Issue Biomass Valorization and Sustainable Biorefineries)
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19 pages, 12386 KB  
Article
First-Principles Insights into Coverage-Dependent Water Adsorption Mechanisms on Representative Lunar Regolith Mineral Surfaces
by Xinnan Deng, Yue Hong, Xueli Wang, Xiuming Ye, Hongtao Xue, Chengdan He, Jin Wang and Fuling Tang
Materials 2026, 19(17), 3805; https://doi.org/10.3390/ma19173805 - 7 Sep 2026
Abstract
Water retention on the lunar surface is governed by water–mineral interactions, yet the atomic-scale transition from isolated adsorption to high-coverage water accumulation remains insufficiently understood. We perform spin-polarized first-principles calculations to investigate single- and multi-water adsorption on representative surfaces of four major lunar [...] Read more.
Water retention on the lunar surface is governed by water–mineral interactions, yet the atomic-scale transition from isolated adsorption to high-coverage water accumulation remains insufficiently understood. We perform spin-polarized first-principles calculations to investigate single- and multi-water adsorption on representative surfaces of four major lunar regolith minerals: CaAl2Si2O8, MgFeSi2O6, FeTiO3, and Mg3FeSi2O8. Single-water adsorption reveals that H2O preferentially anchors at exposed metal sites via O-M coordination, with Ti and Fe sites exhibiting stronger initial binding than Mg, Ca, or Al sites. The Hard–Soft Acid–Base (HSAB) principle provides a qualitative framework for this low-coverage site preference based on Lewis acidity. Specifically, the accessible d-orbitals and localized states of Ti/Fe centers introduce substantial covalent orbital coupling and interfacial polarization, which effectively reinforce the binding with the hard O-donor of water. However, as water coverage increases, the stabilization mechanism undergoes a fundamental transition. At low coverage, adsorption is localized and site-specific, governed by cation acidity. At high coverage, the formation of laterally connected hydrogen-bonded networks becomes the dominant stabilizing factor, and the overall adsorption behavior is increasingly dictated by surface topology and geometric compatibility for hydrogen-bond connectivity rather than by isolated cation acidity. This coverage-dependent evolution from electronic-driven anchoring to topology-driven network formation establishes a dual-stage cooperative mechanism for water accumulation on lunar mineral surfaces. Our findings suggest that models for volatile retention on airless bodies must account for both the electronic activity of surface cations and the structural topology of mineral surfaces. Full article
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19 pages, 4126 KB  
Article
Spatial Mineralogical and Geochemical Variations Across Mafic Dike–Country Rock Contacts in the Permian Nam Duk Formation, Thailand
by Vimoltip Singtuen, Juthatip Khonman and Burapha Phajuy
Minerals 2026, 16(9), 918; https://doi.org/10.3390/min16090918 - 5 Sep 2026
Viewed by 130
Abstract
The emplacement of mafic dikes into carbonate-bearing sedimentary successions commonly produces localized mineralogical and geochemical variations in adjacent country rocks. However, the spatial distribution of these variations remains poorly documented in the Permian sedimentary successions of Thailand. The study investigates spatial mineralogical and [...] Read more.
The emplacement of mafic dikes into carbonate-bearing sedimentary successions commonly produces localized mineralogical and geochemical variations in adjacent country rocks. However, the spatial distribution of these variations remains poorly documented in the Permian sedimentary successions of Thailand. The study investigates spatial mineralogical and geochemical variations across intrusive rocks and adjacent sedimentary rocks in the Permian Nam Duk Formation, Phetchabun Province, Thailand. Petrographic observations and whole-rock geochemical analyses (XRF and ICP-MS), supported by qualitative XRD phase identification, were integrated to characterize mineral assemblages and whole-rock geochemistry. The intrusive rocks display porphyritic textures dominated by plagioclase and hornblende, whereas the adjacent country rocks are characterized by quartz, calcite, feldspar, clay minerals, and secondary alteration phases. Spatial variations in mineral assemblages are accompanied by changes in contents of some major oxides (SiO2, Al2O3, Fe2O3, MgO, and CaO) and selected trace and rare earth elements. The sedimentary country rocks generally contain higher total REE concentrations, particularly La and Ce, whereas the contact-proximal sample shows values closer to the mafic dike. Site A shows the clearest spatial variations across the exposed mafic dike–country rock contact, whereas site B exhibits compositional variability associated with strongly altered porphyritic andesite and heterogeneous sedimentary rocks. The integrated results document localized mineralogical and geochemical variations across the investigated intrusive–sedimentary rock systems, although primary lithological heterogeneity and secondary alteration may also contribute to these patterns. Full article
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20 pages, 5145 KB  
Article
Elemental Variation in Juniperus Leaves and Cones: A Comparative Study of Three Species and Soil Under Their Canopies
by Oimahmad Rahmonov and Małgorzata Rahmonov
Forests 2026, 17(9), 1042; https://doi.org/10.3390/f17091042 - 1 Sep 2026
Viewed by 214
Abstract
Juniperus species form critical, long-lived high-mountain forest ecosystems in Central Asia, serving essential phytocoenotic and ecological functions in environmentally challenging habitats. However, the relationships between the elemental composition of these evergreen conifers and their underlying soils remain poorly understood. This study evaluated and [...] Read more.
Juniperus species form critical, long-lived high-mountain forest ecosystems in Central Asia, serving essential phytocoenotic and ecological functions in environmentally challenging habitats. However, the relationships between the elemental composition of these evergreen conifers and their underlying soils remain poorly understood. This study evaluated and compared the distribution of major elements (Fe, Ca, P, Mg, Al, Na, K, S), trace elements (Cu, Pb, Zn, Ni, Co, Mn, As, Cd, Cr, Mo, U, Th, Sr, Sb, Bi, V, La, Ba, Ti, B, W, Sc, Zr, Tl, Ta, Nb, Se, Te, Ga, Cs, Ge, Hf, Rb, Sn and others), and environmental pollution indices (Igeo, EF, CF, BAF) in plant tissues (leaves and cones) and canopy soils of three key juniper species (Juniperus seravschanica, J. turkestanica, and J. semiglobosa) in the Fann Mountains, Tajikistan. Soil and plant samples were collected across natural habitats and analyzed for total chemical composition using ICP-OES. The soils showed a near-neutral reaction (pH 7.02–7.42 in H2O and 6.41–7.15 in KCl), with considerable variability in Corg. content (5.04%–21.82%) and Nt content (0.337%–1.149%) in the humus (A) horizons. Geochemical indices (Igeo up to 2.42, EF up to 35.30) indicated noticeable soil enrichment and localized contamination by arsenic (As) and cadmium (Cd), likely driven by a combination of regional industrial and mining activities alongside natural geogenic enrichment. Across all sites, elemental concentrations followed a consistent sequence: soil > leaves ≈ cones. Heavy metals in plant tissues remained well below toxic thresholds. High organ-specific partitioning was observed: K predominated in cones (K > Ca > P), whereas Ca and Fe accumulated predominantly in leaves (Ca > K). Low bioaccumulation factor values (BAF < 1) indicate limited element accumulation relative to total soil concentrations for all three species, which may be influenced by both reduced bioavailability in neutral-to-alkaline soils and potential physiological regulation. As the first data reported from this region, these findings establish an essential baseline for long-term ecological monitoring, soil–plant chemistry, conservation, and environmental risk assessment in the Fann Mountains’ juniper ecosystems. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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22 pages, 32457 KB  
Article
Preparation and Characterization of the Properties of Atmospheric Plasma-Sprayed Sr/Mg-Doped Bioactive Glass Coatings on Titanium Alloys
by Da Zeng, Yanwen Chen, Jianfeng Chen, Cijun Shuai, Fangwei Qi, Peilin Chen and Deping Wang
Materials 2026, 19(17), 3596; https://doi.org/10.3390/ma19173596 - 24 Aug 2026
Viewed by 251
Abstract
Titanium alloys are widely used in clinical settings due to their excellent mechanical properties and biocompatibility. However, the biologically inert surface of titanium alloys limits interfacial bioactivity and bone integration, which may compromise long-term implant stability. Therefore, this study innovatively proposes a synergistic [...] Read more.
Titanium alloys are widely used in clinical settings due to their excellent mechanical properties and biocompatibility. However, the biologically inert surface of titanium alloys limits interfacial bioactivity and bone integration, which may compromise long-term implant stability. Therefore, this study innovatively proposes a synergistic “composition design and process adaptation” strategy. Specifically, borosilicate bioactive glasses (BSBGs) with a high B2O3 content (36 mol%), co-doped with strontium (Sr) and magnesium (Mg), were designed and systematically compared with Sr/Mg-doped silicate bioactive glasses (SBGs). Both glasses were subsequently deposited onto Ti6Al4V substrates using atmospheric plasma spraying. The results showed that the BSBG coating exhibited an initial boron release concentration of up to 116 mg/L but exhibited excellent cytocompatibility, which is likely related to the synergistic regulation of Sr, Mg, and B ions. Moreover, the BSBG coating induced Ca-P compound mineralization within 24 h, significantly faster than the SBG coating, which required a minimum of 3 days, confirming superior biomineralization kinetics. Both coatings achieved a bonding strength of 30 MPa, meeting clinical requirements. In vivo experiments confirmed that the BSBG coating significantly promoted new bone regeneration and implant osseointegration. This work not only delivers experimental validation supporting the implementation of high-boron-content bioactive glass coatings but also provides a practical method for designing rapidly degradable and highly bioactive coatings to facilitate improved osseointegration. Full article
(This article belongs to the Section Biomaterials)
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28 pages, 5485 KB  
Article
Flow Characteristics of Unclassified Tailings Backfill Slurry and Optimization of Roof-Contact Backfilling Scheme
by Hongjiao Li, Yuye Tan, Xu Huang, Zenggui Zhang, Jiazhao Chen and Yuchao Deng
Materials 2026, 19(17), 3580; https://doi.org/10.3390/ma19173580 - 24 Aug 2026
Viewed by 226
Abstract
Roof-contact backfilling is a critical determinant of stope stability in cut-and-fill mining, and the rheological properties of backfill slurry decisively influence the quality of roof contact. To investigate the flow characteristics of unclassified tailings backfill slurry and their effect on rheological parameters, this [...] Read more.
Roof-contact backfilling is a critical determinant of stope stability in cut-and-fill mining, and the rheological properties of backfill slurry decisively influence the quality of roof contact. To investigate the flow characteristics of unclassified tailings backfill slurry and their effect on rheological parameters, this study uses the Daye Iron Mine as its engineering case. It adopts a combined laboratory and numerical simulation approach. The physicochemical characteristics of the unclassified tailings and the rheological behavior of the slurry were systematically characterized using particle-size analysis, density measurements, spreadability tests, and rheometer measurements. Subsequently, a numerical model of the L-type flow tester was developed in COMSOL Multiphysics (6.4) to simulate the flow process at varying concentrations. Based on the simulation results, a Gaussian process regression (GPR)-based inversion model for rheological parameters was proposed, and the predictive performance of different kernel functions was compared and evaluated. Finally, the existing backfilling scheme at the Daye Iron Mine was optimized based on the obtained rheological characteristics to improve the roof-contact rate. The results indicate that the unclassified tailings from the Daye Iron Mine have a median particle size of 12.1 μm and a density of 2855 kg·m−3, with CaO, Al2O3, and MgO as the primary active components. Under the same cement-to-tailings ratio, slurry flowability decreases markedly with increasing concentration. The rheological curves exhibit three stages, with the third conforming to the Bingham model; both yield stress and viscosity increase exponentially with concentration. Evaluation of the inversion results demonstrates that the GPR model with the Rational Quadratic (RQ) kernel achieves optimal performance. The recommended slurry concentration for the Daye Iron Mine is determined to be in the range of 69–71%, and the recommended spacing between filling pipelines is 13.34–18 m. This study reveals the flow evolution patterns of unclassified tailings backfill slurry, demonstrates the potential of the GPR-based inversion approach, and optimizes the roof-contact backfilling scheme, offering a scientific reference for flow characterization and backfill optimization in analogous mining operations. Full article
(This article belongs to the Special Issue Sustainability and Performance of Cement-Based Materials)
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19 pages, 7287 KB  
Article
Effect of ZnO on Copper Loss and Fe3O4 Reduction During the Copper Slag Cleaning
by Tao Wei, Haipei Zhang, Haoyuan Xu, Shuang Shao, Shichao Wu, Kai Fan and Bo Li
Metals 2026, 16(8), 893; https://doi.org/10.3390/met16080893 - 10 Aug 2026
Viewed by 289
Abstract
A mass action concentration model of FeO-Fe2O3-SiO2-CaO-MgO-Al2O3-ZnO multi-component slag was established to address the problems of high viscosity and high copper content in oxygen-enriched top-blown copper smelting slag. Theoretical calculations, combined with experimental [...] Read more.
A mass action concentration model of FeO-Fe2O3-SiO2-CaO-MgO-Al2O3-ZnO multi-component slag was established to address the problems of high viscosity and high copper content in oxygen-enriched top-blown copper smelting slag. Theoretical calculations, combined with experimental investigations, were performed to evaluate the effects of ZnO additions (0–25 wt.%) on phase transformation, Fe3O4 reduction and copper content in the slag at temperatures ranging from 1200 to 1400 °C. The results indicate that ZnO addition decreases the mass concentrations of Fe2O3, Fe3O4, Fe2SiO4 and SiO2, while increasing the proportions of zinc-bearing structural units and enhancing the reducing capability of the slag. In the copper slag system, Zn2+ substitutes for Fe in Fe3O4 and Fe2SiO4 through isomorphous substitution, forming Fe-Zn spinel and Fe-Zn olivine. As the addition of ZnO gradually increases to 25 wt.%, the liquid slag fraction increases and the slag viscosity decreases, resulting in a reduction in copper content from 5.64 wt.% to 2.04 wt.%. Furthermore, ZnO promotes the transformation of Fe3O4 into zinc–iron spinel, which is more readily reducible by carbothermic reaction than Fe3O4 itself, thereby facilitating the overall reduction of iron oxides in the copper slag. These findings provide a theoretical basis for slag-type regulation and the efficient separation of copper from slag via high-temperature gravity settling of matte. Full article
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11 pages, 4521 KB  
Article
Structure of Natural Hexacelsian
by Evgeny Galuskin, Irina Galuskina, Maria Książek, Joachim Kusz and Yevgeny Vapnik
Minerals 2026, 16(8), 815; https://doi.org/10.3390/min16080815 - 6 Aug 2026
Viewed by 377
Abstract
For the first time, the structure of natural hexacelsian, BaAl2Si2O8, a polymorph of celsian and paracelsian, has been refined. Hexacelsian was found in rankinite-bearing paralava near Mount Ye’elim in the northern part of the large Hatrurim Complex [...] Read more.
For the first time, the structure of natural hexacelsian, BaAl2Si2O8, a polymorph of celsian and paracelsian, has been refined. Hexacelsian was found in rankinite-bearing paralava near Mount Ye’elim in the northern part of the large Hatrurim Complex pyrometamorphic rock area (Hatrurim Basin) in the Negev Desert, Israel. It associates with Ba-bearing minerals such as barioferrite, walstromite, gurimite and the potentially new mineral BaCa2Mg(SiO4)2, forming small isolated aggregates between the rock-forming minerals. These rock-forming minerals are represented by gehlenite, rankinite, wollastonite and schorlomite. The structure was refined for a hexacelsian grain measuring 0.039 × 0.026 × 0.016 mm with the composition (Ba1.01K0.05Na0.01Ca0.01)Σ1.08(Si1.96Al1.91Fe3+0.11)Σ3.98O8 to R1 = 3%. Natural hexacelsian with P63/mcm symmetry and unit cell parameters of a = 5.2973(4) Å, c = 15.6068(10) Å, γ = 120°, and V = 379.28(6) Å3 is an analogue of synthetic low-temperature α-hexacelsian. The hexacelsian structure (polytype 2H) is formed by double layers of tetrahedra linked by their tops and bases, which are parallel to (001). Each layer is built from hexagonal (ditrigonal) rings of tetrahedra. The tetrahedra in rings with a disordered Al/Si distribution are rotated by approximately 14.5° compared to the position of the tetrahedra in ideal hexagonal rings in the high-temperature γ-hexacelsian. Every second layer in the structure of the studied hexacelsian is rotated through 180°. The hexacelsian crystallised at temperatures above 1100 °C as a disordered, metastable γ-hexacelsian (1H). A decrease in temperature leads to the ordering of O2 sites and the formation of partially ordered α-hexacelsian (2H), which preserves the disordered distribution of Al/Si at the tetrahedra. Some of the γ-hexacelsian grains in paralava were replaced by celsian under high-temperature conditions. Under low-temperature conditions, α-hexacelsian is replaced by cymrite during the zeolitisation of pyrometamorphic rocks of the Hatrurim Complex. Full article
(This article belongs to the Collection New Minerals)
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25 pages, 17940 KB  
Article
Compositional Characterization of Ultrafine Composite Powder as a Novel Supplementary Cementitious Material
by Baoliang Li, Hongrui Shang, Liying Shi, Sahi Wail, Shouhua Liu, Yuanyang Chen and Binbin Huo
Materials 2026, 19(15), 3337; https://doi.org/10.3390/ma19153337 - 5 Aug 2026
Viewed by 294
Abstract
To investigate the application potential of ultrafine composite powder (UCP) as a novel supplementary cementitious material to replace ground granulated blast-furnace slag (GBFS) in cement-based materials and its underlying mechanism, this study first compared the activity differences between UCP and GBFS and their [...] Read more.
To investigate the application potential of ultrafine composite powder (UCP) as a novel supplementary cementitious material to replace ground granulated blast-furnace slag (GBFS) in cement-based materials and its underlying mechanism, this study first compared the activity differences between UCP and GBFS and their effects on mortar workability. Subsequently, multiple characterization techniques including XRF, XRD, TG/DTG, FTIR, mapping, SEM-EDS, and BET were employed to systematically examine the morphology, composition, particle size distribution, and pore structure characteristics of the two powders. Results show that UCP exhibits slightly higher 3 d and 28 d strength activity indices than GBFS, but contributes less to strength progression between 3 and 28 days. In terms of chemical composition, UCP contains lower combined CaO + MgO + Al2O3 content but significantly higher C and Fe levels and alkalinity than GBFS. Phase and microstructural analyses further reveal that UCP is predominantly composed of GBFS, fly ash (FA), steel slag, limestone powder, gypsum, superplasticizer, and alkaline activator, and is characterized as a mesoporous material with pores arising from fragmented FA, unburned carbon residues, and grinding-induced cracks. Quantitatively, the BET specific surface area, Blaine specific surface area, and total pore volume of UCP are 2.47, 1.59, and 3.31 times those of GBFS, respectively. Therefore, the early-age activity advantage of UCP is mainly attributed to the filling effect, the additional nucleation sites provided by its larger specific surface area, and the chemical activation induced by alkali and gypsum. Full article
(This article belongs to the Section Construction and Building Materials)
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29 pages, 18554 KB  
Article
Humic Acid Alleviates Aluminum Toxicity in Citrus grandis (L.) Osbeck: Insight from Growth, Gas Exchange, and Related Physiological Parameters
by Qian Shen, Tian-Tian Xia, Liang-Yuan Tong, Bin-Bin Lan, Wei-Lin Huang, Ti Wu, Xin Ye, Ning-Wei Lai and Li-Song Chen
Plants 2026, 15(15), 2370; https://doi.org/10.3390/plants15152370 - 31 Jul 2026
Viewed by 514
Abstract
Most Citrus spp. trees in China are cultivated in acidic soils with low soil organic matter and high Al3+. The mechanisms of humic acid (HA) to alleviate Al3+ stress in plants remain unclear. ‘Sour pummelo’ (Citrus grandis (L.) Osbeck) [...] Read more.
Most Citrus spp. trees in China are cultivated in acidic soils with low soil organic matter and high Al3+. The mechanisms of humic acid (HA) to alleviate Al3+ stress in plants remain unclear. ‘Sour pummelo’ (Citrus grandis (L.) Osbeck) seedlings were exposed to 0.5 (HA0.5), 0.1 (HA0.1), or 0 (HA0) mM sodium humate and 1.2 (Al1.2) or 0 (Al0) mM AlCl3·6H2O for 128 days. Thereafter, the research examined biomass; Al and mineral nutrients; leaf photosynthetic performance; and leaf and root nonstructural carbohydrates, reactive oxygen species metabolism, and related physiological parameters. Al1.2 significantly reduced whole plant dry weight (DW), root DW, leaf CO2 assimilation (ACO2), and chlorophyll a + b concentration by 61%, 45%, 61%, and 35%, respectively, at HA0, but only 48%, 17%, 44%, and 11%, respectively, at HA0.5. Further analysis suggested that the addition of HA endowed Citrus with Al resilience by the following several aspects: (a) lessened tissue (leaf, stem, and root) concentrations of Al and enhanced capacity to maintain macronutrient (S, K, Mg, Ca, N, and P) homeostasis at Al1.2; (b) improved capacity to combat oxidative stress at Al1.2; and (c) enhanced ACO2 and growth at Al1.2. Further analysis indicated that HA-mediated alleviation of growth decline caused by Al1.2 involved (a) reduced ability to absorb Al and less root-to-shoot Al transport and (b) increased ability to maintain macronutrient homeostasis and to combat oxidative stress; and that HA-mediated alleviation of leaf chlorophyll and ACO2 decline and photosynthetic electron transport chain impairment involved less leaf Al concentration and improved leaf macronutrient homeostasis. To conclude, the addition of HA lowered roots’ ability to absorb Al and tissue Al concentration and subsequently mitigated Al-toxic impairment to root growth and function, thereby enhancing the ability of plants to maintain macronutrient homeostasis, and hence alleviating Al1.2-stimulated oxidative damage and inhibition of ACO2 and growth. Full article
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24 pages, 4720 KB  
Review
Review of Glycerol Conversion to Glycerol Carbonate via Alkyl Carbonates: Reflections, Future Perspective and Catalytic Roles of Mixed/Promoted Metal Oxides and Mechanistic Insights from DFT
by Sakhile T. Dube, Lindelani Q. Qwabe and Holger B. Friedrich
Molecules 2026, 31(15), 2623; https://doi.org/10.3390/molecules31152623 - 28 Jul 2026
Viewed by 462
Abstract
This review summarizes recent progress in the catalytic conversion of glycerol to glycerol carbonate (GC) via transesterification with alkyl carbonates, a sustainable route for valorizing surplus glycerol from biodiesel production. Emphasis is placed on mixed and promoter-modified metal oxide catalysts, which exhibit high [...] Read more.
This review summarizes recent progress in the catalytic conversion of glycerol to glycerol carbonate (GC) via transesterification with alkyl carbonates, a sustainable route for valorizing surplus glycerol from biodiesel production. Emphasis is placed on mixed and promoter-modified metal oxide catalysts, which exhibit high activity, selectivity, and stability due to their tunable balance of basic and Lewis acidic sites. Systems such as Mg-Fe, Mg-Al, Mg-Zr, CaO-CeO2, and Mg-Ba oxides have achieved over 90% glycerol conversion and 90–96% GC selectivity under mild, often solvent-free conditions. Mechanistic insights, increasingly supported by density functional theory (DFT), reveal that the reaction proceeds via base-assisted glycerol deprotonation, carbonate activation at Lewis acidic centers, and subsequent cyclization to GC. These findings underscore the importance of acid–base cooperation and promoter effects in enhancing turnover frequency, reducing energy barriers, and mitigating catalyst deactivation due to carbonate deposition or leaching. By integrating experimental results with theoretical modelling, this review provides a comprehensive understanding of catalyst design principles, offering guidance for the development of efficient and robust systems for scalable glycerol upgrading. Full article
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27 pages, 22484 KB  
Article
Waste Aluminum Dust-Derived Functional Zeolites for Heavy Metal Removal and Water Softening: Synthesis, Purification, and Ion-Exchange Modification
by Min-Seo Choi, Jeong-Sik Moon and Jei-Pil Wang
Metals 2026, 16(7), 779; https://doi.org/10.3390/met16070779 - 12 Jul 2026
Viewed by 308
Abstract
Waste aluminum dust generated from aluminum refining and machining processes contains high fractions of Al2O3 and SiO2, making it a potential secondary aluminosilicate resource for zeolite synthesis. In this study, waste aluminum dust was converted into functional zeolite [...] Read more.
Waste aluminum dust generated from aluminum refining and machining processes contains high fractions of Al2O3 and SiO2, making it a potential secondary aluminosilicate resource for zeolite synthesis. In this study, waste aluminum dust was converted into functional zeolite materials through dry fusion purification, NaOH-assisted hydrothermal synthesis, acid purification, Si/Al ratio control, and cation-exchange modification. The raw dust was subjected to dry fusion at 1600 °C under an Ar atmosphere to remove metallic impurities and obtain an aluminosilicate precursor. Na-type zeolite was then synthesized using 50 wt.% NaOH solution at 90 °C for 24 h. The as-synthesized Na-type zeolite exhibited an estimated chemical purity of 97.501 wt.% based on measured residual impurities, with Mg, Ca, K, and Ti remaining as major impurities. HCl leaching at 0.25 M for 24 h increased the estimated chemical purity based on measured residual impurities to 98.469 wt.% while retaining the major zeolitic diffraction features. The Si/Al ratio was further controlled using water glass, and the maximum Si/Al ratio of 1.77 was obtained at a Na-type zeolite-to-water-glass mass ratio of 1:2 after reaction at 90 °C for 6 h. The purified and composition-controlled zeolite was subsequently modified with Mg2+ and K+ ions to prepare Mg-modified and K-modified zeolites. Under fixed batch conditions using a relatively high zeolite dosage and a single initial concentration, Mg-modified zeolite reduced Pb, Hg, Cr(VI), and Cd concentrations from 100 ppm to 0.004, 0.00059, 0.018, and 0.004 ppm, respectively, while K-modified zeolite reduced the total hardness of synthetic hard water from 308.3 to 40.13 ppm as CaCO3. These results should be interpreted as preliminary batch-performance results under the tested conditions rather than as maximum adsorption capacities or a complete adsorption-mechanism evaluation. Overall, this study demonstrates the feasibility of valorizing waste aluminum dust into purified and cation-modified zeolite materials for potential water-treatment applications. Further adsorption isotherm, kinetic, dosage-dependent, BET surface area, pore-volume, pore-size distribution, and quantitative phase analyses are required to evaluate adsorption capacity, adsorption mechanism, true zeolite phase purity, and framework–performance relationships. Full article
(This article belongs to the Special Issue Recent Advances in Metal Ion Separation)
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18 pages, 6597 KB  
Review
Progress in Melting-Flow Characteristics of Titanium-Bearing Blast Furnace Slag
by Guang Li, Shuai Wang, Yufeng Guo, Mao Chen, Yihan Huang, Feng Chen, Jinlai Zhang and Lingzhi Yang
Metals 2026, 16(7), 707; https://doi.org/10.3390/met16070707 - 27 Jun 2026
Viewed by 391
Abstract
Vanadium–titanium magnetite is a critical strategic polymetallic mineral resource in China, and blast furnace smelting represents the dominant large-scale industrial process for its utilization. The melting and fluidity properties of titanium-bearing blast furnace slags (TBFS) directly govern stable blast furnace operation and the [...] Read more.
Vanadium–titanium magnetite is a critical strategic polymetallic mineral resource in China, and blast furnace smelting represents the dominant large-scale industrial process for its utilization. The melting and fluidity properties of titanium-bearing blast furnace slags (TBFS) directly govern stable blast furnace operation and the recovery efficiency of vanadium–titanium resources. This paper systematically reviews research progress on the melting and flow characteristics of TBFS. The influences of main components (TiO2, CaO/SiO2, MgO, Al2O3), trace oxides, and strongly reduced products TiC and TiN on slag mineral phases, break point temperature (TBr) and viscosity are summarized. Combined with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman characterizations and FactSage thermodynamic calculations, the inherent mechanisms are revealed from the perspectives of microstructural network polymerization and crystalline phase precipitation. TiO2 exerts dual effects: it depolymerizes the silicate network to reduce slag viscosity while promoting the precipitation of high-melting-point perovskite. Al2O3 intensifies network polymerization and impairs slag fluidity. MgO, basicity, MnO and BaO can decrease slag viscosity. Solid particles of TiC and TiN generated under the strong reducing atmosphere inside blast furnaces drastically increase slag viscosity and Tbr. This paper proposes that future research should focus on slag systems with higher TiO2 contents, so as to provide theoretical support for the high-efficiency blast furnace smelting of VTM and resource utilization of titanium-bearing slags. Full article
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15 pages, 4069 KB  
Article
Elucidating the Firing Mechanisms of Ceramics in Guizhou Province via Interfacial Electronic and Mechanical Properties
by Yun Xu and Weifu Cen
Ceramics 2026, 9(6), 63; https://doi.org/10.3390/ceramics9060063 - 22 Jun 2026
Viewed by 421
Abstract
Ceramics, as a handicraft, is the crystallization of art and science. In order to study the firing process of ceramics, improve their density, mechanical properties, viscosity, and surface tension, and enhance the surface quality of the shaft, this article uses first-principles methods to [...] Read more.
Ceramics, as a handicraft, is the crystallization of art and science. In order to study the firing process of ceramics, improve their density, mechanical properties, viscosity, and surface tension, and enhance the surface quality of the shaft, this article uses first-principles methods to study the electronic properties of ceramic colorants Al2O3, Fe2O3, TiO2, CaO, MgO, Na2O, KO2, and ceramic body SiO2. Research has shown that these seven color-developing agents exhibit anisotropy and have stable crystal structures. The bandgap values of Al2O3, CaO, Fe2O3, KO2, MgO, Na2O, TiO2, and ceramic SiO2 are 6.325 eV, 3.654 eV, 0 eV, 0 eV, 4.731 eV, 1.972 eV, 2.18 eV and 6.002 eV, respectively. In Al2O3/SiO2, Fe2O3/SiO2, TiO2/SiO2, CaO/SiO2, MgO/SiO2, Na2O/SiO2, and KO2/SiO2 systems, due to the influence of the potential field in the SiO2 system, the charge characteristics exhibit obvious interfacial and non-periodic characteristics. The research results revealed the charge transfer and distribution patterns at the interface between ceramic colorants and ceramic ligands, elucidating the influence mechanism of different colorants/embryo components on firing temperature, shrinkage rate, and finished product defects. This mechanism can be used to predict the advantages and disadvantages of alkali metals, iron, titanium, and aluminum components in raw materials, optimize low-temperature rapid firing formulas, suppress firing deformation, control pore defects, and improve the mechanical properties of finished products. It provides micro theoretical support for the industrialization, stabilization, and high-quality production of local ceramics in southwestern China. Full article
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