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Keywords = calcination test

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20 pages, 3271 KiB  
Article
Calculation Model for the Degree of Hydration and Strength Prediction in Basalt Fiber-Reinforced Lightweight Aggregate Concrete
by Yanqun Sun, Haoxuan Jia, Jianxin Wang, Yanfei Ding, Yanfeng Guan, Dongyi Lei and Ying Li
Buildings 2025, 15(15), 2699; https://doi.org/10.3390/buildings15152699 (registering DOI) - 31 Jul 2025
Viewed by 162
Abstract
The combined application of fibers and lightweight aggregates (LWAs) represents an effective approach to achieving high-strength, lightweight concrete. To enhance the predictability of the mechanical properties of fiber-reinforced lightweight aggregate concrete (LWAC), this study conducts an in-depth investigation into its hydration characteristics. In [...] Read more.
The combined application of fibers and lightweight aggregates (LWAs) represents an effective approach to achieving high-strength, lightweight concrete. To enhance the predictability of the mechanical properties of fiber-reinforced lightweight aggregate concrete (LWAC), this study conducts an in-depth investigation into its hydration characteristics. In this study, high-strength LWAC was developed by incorporating low water absorption LWAs, various volume fractions of basalt fiber (BF) (0.1%, 0.2%, and 0.3%), and a ternary cementitious system consisting of 70% cement, 20% fly ash, and 10% silica fume. The hydration-related properties were evaluated through isothermal calorimetry test and high-temperature calcination test. The results indicate that incorporating 0.1–0.3% fibers into the cementitious system delays the early hydration process, with a reduced peak heat release rate and a delayed peak heat release time compared to the control group. However, fitting the cumulative heat release over a 72-h period using the Knudsen equation suggests that BF has a minor impact on the final degree of hydration, with the difference in maximum heat release not exceeding 3%. Additionally, the calculation model for the final degree of hydration in the ternary binding system was also revised based on the maximum heat release at different water-to-binder ratios. The results for chemically bound water content show that compared with the pre-wetted LWA group, under identical net water content conditions, the non-pre-wetted LWA group exhibits a significant reduction at three days, with a decrease of 28.8%; while under identical total water content conditions it shows maximum reduction at ninety days with a decrease of 5%. This indicates that pre-wetted LWAs help maintain an effective water-to-binder ratio and facilitate continuous advancement in long-term hydration reactions. Based on these results, influence coefficients related to LWAs for both final degree of hydration and hydration rate were integrated into calculation models for degrees of hydration. Ultimately, this study verified reliability of strength prediction models based on degrees of hydration. Full article
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17 pages, 2736 KiB  
Article
Controlled Formation of α- and β-Bi2O3 with Tunable Morphologies for Visible-Light-Driven Photocatalysis
by Thomas Cadenbach, María Isabel Loyola-Plúa, Freddy Quijano Carrasco, Maria J. Benitez, Alexis Debut and Karla Vizuete
Molecules 2025, 30(15), 3190; https://doi.org/10.3390/molecules30153190 - 30 Jul 2025
Viewed by 181
Abstract
Water pollution caused by increasing industrial and human activity remains a serious environmental challenge, especially due to the persistence of organic contaminants in aquatic systems. Photocatalysis offers a promising and eco-friendly solution, but in the case of bismuth oxide (Bi2O3 [...] Read more.
Water pollution caused by increasing industrial and human activity remains a serious environmental challenge, especially due to the persistence of organic contaminants in aquatic systems. Photocatalysis offers a promising and eco-friendly solution, but in the case of bismuth oxide (Bi2O3) there is still a limited understanding of how structural and morphological features influence photocatalytic performance. In this work, a straightforward hydrothermal synthesis method followed by controlled calcination was developed to produce phase-pure α- and β-Bi2O3 with tunable morphologies. By varying the hydrothermal temperature and reaction time, distinct structures were successfully obtained, including flower-like, broccoli-like, and fused morphologies. XRD analyses showed that the final crystal phase depends solely on the calcination temperature, with β-Bi2O3 forming at 350 °C and α-Bi2O3 at 500 °C. SEM and BET analyses confirmed that morphology and surface area are strongly influenced by the hydrothermal conditions, with the flower-like β-Bi2O3 exhibiting the highest surface area. UV–Vis spectroscopy revealed that β-Bi2O3 also has a lower bandgap than its α counterpart, making it more responsive to visible light. Photocatalytic tests using Rhodamine B showed that the flower-like β-Bi2O3 achieved the highest degradation efficiency (81% in 4 h). Kinetic analysis followed pseudo-first-order behavior, and radical scavenging experiments identified hydroxyl radicals, superoxide radicals, and holes as key active species. The catalyst also demonstrated excellent stability and reusability. Additionally, Methyl Orange (MO), a more stable and persistent azo dye, was selected as a second model pollutant. The flower-like β-Bi2O3 catalyst achieved 73% degradation of MO at pH = 7 and complete removal under acidic conditions (pH = 2) in less than 3 h. These findings underscore the importance of both phase and morphology in designing high-performance Bi2O3 photocatalysts for environmental remediation. Full article
(This article belongs to the Special Issue Green Catalysis Technology for Sustainable Energy Conversion)
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17 pages, 4077 KiB  
Article
The Impact of Sm Promoter on the Catalytic Performance of Ni/Al2O3-SiO2 in Methane Partial Oxidation for Enhanced H2 Production
by Salwa B. Alreshaidan, Rasha S. A. Alanazi, Omalsad H. Odhah, Ahmed A. Ibrahim, Fekri Abdulraqeb Ahmed Ali, Naif Alarifi, Khaled M. Banabdwin, Sivalingam Ramesh and Ahmed S. Al-Fatesh
Catalysts 2025, 15(8), 721; https://doi.org/10.3390/catal15080721 (registering DOI) - 29 Jul 2025
Viewed by 277
Abstract
This study investigates the effects of samarium (Sm) promotion on the catalytic activity of 5 weight percent Ni catalysts for partial oxidation of methane (POM)-based hydrogen production supported on a Si-Al mixed oxide (10SiO2+90Al2O3) system. Several 5% [...] Read more.
This study investigates the effects of samarium (Sm) promotion on the catalytic activity of 5 weight percent Ni catalysts for partial oxidation of methane (POM)-based hydrogen production supported on a Si-Al mixed oxide (10SiO2+90Al2O3) system. Several 5% Ni-based catalysts supported on silica–alumina was used to test the POM at 600 °C. Sm additions ranged from 0 to 2 wt.%. Impregnation was used to create these catalysts, which were then calcined at 500 °C and examined using BET, H2-TPR, XRD, FTIR, TEM, Raman spectroscopy, and TGA methods. Methane conversion (57.85%) and hydrogen yield (56.89%) were greatly increased with an ideal Sm loading of 1 wt.%, indicating increased catalytic activity and stability. According to catalytic tests, 1 wt.% Sm produced high CH4 conversion and H2 production, as well as enhanced stability and resistance to carbon deposition. Nitrogen physisorption demonstrated a progressive decrease in pore volume and surface area with the addition of Sm, while maintaining mesoporosity. At moderate Sm loadings, H2-TPR and XRD analyses showed changes in crystallinity and increased NiO reducibility. Sm incorporation into the support and its impact on the ordering of carbon species were indicated by FTIR and Raman spectra. The optimal conditions to maximize H2 yield were successfully identified through optimization of the best catalyst, and there was good agreement between the theoretical predictions (87.563%) and actual results (88.39%). This displays how successfully the optimization approach achieves the intended outcome. Overall, this study demonstrates that the performance and durability of Ni-based catalysts for generating syngas through POM are greatly enhanced by the addition of a moderate amount of Sm, particularly 1 wt.%. Full article
(This article belongs to the Section Industrial Catalysis)
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17 pages, 7274 KiB  
Article
Sol–Gel-Derived Silica/Alumina Particles for Enhancing the Mechanical Properties of Acrylate Composite Materials
by Khaled Altwair, Vladisav Tadić, Miloš Petrović, Andrija Savić, Vesna Radojević, Radmila Jančić Heinemann and Marija M. Vuksanović
Gels 2025, 11(8), 575; https://doi.org/10.3390/gels11080575 - 24 Jul 2025
Viewed by 262
Abstract
Silica/alumina composite particles were synthesized via the sol–gel method to promote fine dispersion and homogenous mixing. Aluminum chloride hydroxide served as the alumina precursor, while amorphous silica, obtained from rice husk, was directly incorporated into the alumina sol. Following synthesis, the material was [...] Read more.
Silica/alumina composite particles were synthesized via the sol–gel method to promote fine dispersion and homogenous mixing. Aluminum chloride hydroxide served as the alumina precursor, while amorphous silica, obtained from rice husk, was directly incorporated into the alumina sol. Following synthesis, the material was calcined at 1000 °C, yielding an α-cristobalite form of silica and corundum-phase alumina. These hybrid particles were introduced into polymer composites at reinforcement levels of 1 wt.%, 3 wt.%, and 5 wt.%. Mechanical behavior was evaluated through three-point bending tests, Shore D hardness measurements, and controlled-energy impact testing. Among the formulations, the 3 wt.% composite exhibited optimal performance, displaying the highest flexural modulus and strength, along with enhanced impact resistance. Hardness increased with rising particle content. Fractographic analysis revealed that the 3 wt.% loading produced a notably rougher fracture surface, correlating with improved energy absorption. In contrast, the 5 wt.% composite, although harder than the matrix and other composites, exhibited diminished toughness due to particle agglomeration. Full article
(This article belongs to the Special Issue Advances in Composite Gels (3rd Edition))
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26 pages, 4943 KiB  
Article
Ultrasonic Pulse Velocity for Real-Time Filament Quality Monitoring in 3D Concrete Printing Construction
by Luis de la Flor Juncal, Allan Scott, Don Clucas and Giuseppe Loporcaro
Buildings 2025, 15(14), 2566; https://doi.org/10.3390/buildings15142566 - 21 Jul 2025
Viewed by 283
Abstract
Three-dimensional (3D) concrete printing (3DCP) has gained significant attention over the last decade due to its many claimed benefits. The absence of effective real-time quality control mechanisms, however, can lead to inconsistencies in extrusion, compromising the integrity of 3D-printed structures. Although the importance [...] Read more.
Three-dimensional (3D) concrete printing (3DCP) has gained significant attention over the last decade due to its many claimed benefits. The absence of effective real-time quality control mechanisms, however, can lead to inconsistencies in extrusion, compromising the integrity of 3D-printed structures. Although the importance of quality control in 3DCP is broadly acknowledged, research lacks systematic methods. This research investigates the feasibility of using ultrasonic pulse velocity (UPV) as a practical, in situ, real-time monitoring tool for 3DCP. Two different groups of binders were investigated: limestone calcined clay (LC3) and zeolite-based mixes in binary and ternary blends. Filaments of 200 mm were extruded every 5 min, and UPV, pocket hand vane, flow table, and viscometer tests were performed to measure pulse velocity, shear strength, relative deformation, yield stress, and plastic viscosity, respectively, in the fresh state. Once the filaments presented printing defects (e.g., filament tearing, filament width reduction), the tests were concluded, and the open time was recorded. Isothermal calorimetry tests were conducted to obtain the initial heat release and reactivity of the supplementary cementitious materials (SCMs). Results showed a strong correlation (R2 = 0.93) between UPV and initial heat release, indicating that early hydration (ettringite formation) influenced UPV and determined printability across different mixes. No correlation was observed between the other tests and hydration kinetics. UPV demonstrated potential as a real-time monitoring tool, provided the mix-specific pulse velocity is established beforehand. Further research is needed to evaluate UPV performance during active printing when there is an active flow through the printer. Full article
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29 pages, 3791 KiB  
Article
Production of Sustainable Synthetic Natural Gas from Carbon Dioxide and Renewable Energy Catalyzed by Carbon-Nanotube-Supported Ni and ZrO2 Nanoparticles
by João Pedro Bueno de Oliveira, Mariana Tiemi Iwasaki, Henrique Carvalhais Milanezi, João Lucas Marques Barros, Arnaldo Agostinho Simionato, Bruno da Silva Marques, Carlos Alberto Franchini, Ernesto Antonio Urquieta-González, Ricardo José Chimentão, José Maria Corrêa Bueno, Adriana Maria da Silva and João Batista Oliveira dos Santos
Catalysts 2025, 15(7), 675; https://doi.org/10.3390/catal15070675 - 11 Jul 2025
Viewed by 474
Abstract
The production of synthetic natural gas in the context of power-to-gas is a promising technology for the utilization of CO2. Ni-based catalysts supported on carbon nanotubes (CNTs) were prepared through incipient wetness impregnation and characterized using N2 adsorption, X-ray diffraction [...] Read more.
The production of synthetic natural gas in the context of power-to-gas is a promising technology for the utilization of CO2. Ni-based catalysts supported on carbon nanotubes (CNTs) were prepared through incipient wetness impregnation and characterized using N2 adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and temperature-programmed reduction (TPR). The catalysts were tested for CO2 methanation in the 200–400 °C temperature range and at atmospheric pressure. The results demonstrated that the catalytic activity increased with the addition of the CNTs and Ni loading. The selectivity towards CH4 was close to 100% for the Ni/ZrO2/CNT catalysts. Reduction of the calcined catalyst at 500 °C using H2 modified the surface chemistry of the catalyst, leading to an increase in the Ni particles. The CO2 conversion was dependent on the Ni loading and the temperature reduction in the NiO species. The 10Ni/ZrO2/CNT catalyst was highly stable in CO2 methanation at 350 °C for 24 h. Thus, CNTs combined with Ni and ZrO2 were considered promising for use as catalysts in CO2 methanation at low temperatures. Full article
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21 pages, 4087 KiB  
Article
Performance Evaluation of Low-Grade Clay Minerals in LC3-Based Cementitious Composites
by Nosheen Blouch, Syed Noman Hussain Kazmi, Nijah Akram, Muhammad Junaid Saleem, Imran Ahmad Khan, Kashif Javed, Sajjad Ahmad and Asfandyar Khan
Solids 2025, 6(3), 35; https://doi.org/10.3390/solids6030035 - 10 Jul 2025
Viewed by 337
Abstract
The cements industry is increasingly under pressure to reduce carbon emissions while maintaining performance standards. Limestone calcined clay cement (LC3) presents a promising low-carbon alternative; however, its performance depends significantly on the type and reactivity of clay used. This study investigates [...] Read more.
The cements industry is increasingly under pressure to reduce carbon emissions while maintaining performance standards. Limestone calcined clay cement (LC3) presents a promising low-carbon alternative; however, its performance depends significantly on the type and reactivity of clay used. This study investigates the effect of three common low-grade clay minerals—kaolinite, montmorillonite, and illite—on the behavior of LC3 blends. The clays were thermally activated and characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray fluorescence spectroscopy (XRF), and Blaine air permeability testing to evaluate their mineralogical composition, thermal behavior, chemical content, and fineness. Pozzolanic reactivity was assessed using the modified Chapelle test. Microstructural development was examined through scanning electron microscopy (SEM) of the hydrated specimens at 28 days. The results confirmed a strong correlation between clay reactivity and hydration performance. Kaolinite showed the highest reactivity and fineness, contributing to a dense microstructure with reduced portlandite and enhanced formation of calcium silicate hydrate. Montmorillonite demonstrated comparable strength and favorable hydration characteristics, while illite, though less reactive initially, showed acceptable long-term behavior. Although kaolinite delivered the best overall performance, its limited availability and higher cost suggest that montmorillonite and illite represent viable and cost-effective alternatives, particularly in regions where kaolinite is scarce. This study highlights the suitability of regionally available, low-grade clays for use in LC3 systems, supporting sustainable and economically viable cement production. Full article
(This article belongs to the Topic Novel Cementitious Materials)
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11 pages, 1263 KiB  
Article
Characteristics of Laterite Soil for Potential Geopolymer Applications
by Zeyneb K. Nuru, Walied A. Elsaigh and Elsabe P. Kearsley
Minerals 2025, 15(7), 719; https://doi.org/10.3390/min15070719 - 9 Jul 2025
Viewed by 356
Abstract
Laterite soil is widely found in various tropical and subtropical regions. This study focuses on the physical and chemical properties of laterite soil as a precursor for geopolymer synthesis. The characteristics of the soil were determined through experimental analyses, including XRF, XRD, SEM, [...] Read more.
Laterite soil is widely found in various tropical and subtropical regions. This study focuses on the physical and chemical properties of laterite soil as a precursor for geopolymer synthesis. The characteristics of the soil were determined through experimental analyses, including XRF, XRD, SEM, EDS, FTIR, TGA/DTA, and pH measurements. XRF analysis revealed that the primary chemical oxides are silica, alumina, and iron oxide, which are very essential for geopolymer production. Both XRD and FTIR assessments revealed that the calcination process applied to laterite diminishes its crystallinity while enhancing its amorphous nature, thereby improving its reactivity. TGA and DTA results confirmed significant weight loss and dihydroxylation between 400 °C and 700 °C, while temperatures above 700 °C showed minimal weight loss and no further dihydroxylation. The pH of the tested laterite soil was measured at 5.35, indicating strong acidic behaviour. Based on these combined chemical and physical analyses, this study concludes that laterite soil is a viable precursor material for geopolymer synthesis. Full article
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18 pages, 4306 KiB  
Article
Optimizing the Thermal Treatment of Mining-Waste-Amended Clays for Ceramic Aggregates in Pavement Applications
by Murilo Miguel Narciso, Lisley Madeira Coelho, Sergio Neves Monteiro and Antônio Carlos Rodrigues Guimarães
Materials 2025, 18(13), 3180; https://doi.org/10.3390/ma18133180 - 4 Jul 2025
Viewed by 317
Abstract
Mining activities generate large volumes of tailings with significant environmental impact but also the potential for sustainable reuse in construction materials. This study evaluates the production of ceramic aggregates from mixtures of clay, sand, and iron ore waste subjected to thermal treatment at [...] Read more.
Mining activities generate large volumes of tailings with significant environmental impact but also the potential for sustainable reuse in construction materials. This study evaluates the production of ceramic aggregates from mixtures of clay, sand, and iron ore waste subjected to thermal treatment at temperatures ranging from 600 to 1100 °C. The influence of calcination temperature on mineralogical transformations and mechanical integrity was investigated using X-ray diffraction (XRD) and the α-Treton parameter, derived from standardized impact resistance testing. The results indicate that the formation of metakaolinite between 700 and 900 °C enhances mechanical resistance, while higher temperatures (>900 °C) lead to structural degradation, followed by partial recovery due to mullite crystallization. The α-Treton curve exhibited clear correlation with the phase changes identified by XRD, demonstrating its applicability as a low-cost, sensitive proxy for optimizing thermal activation. A simplified methodology is proposed to optimize the thermal activation of such materials by correlating firing temperature with mineralogical evolution and mechanical integrity, contributing to the development of sustainable ceramic aggregates for pavement applications. Full article
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25 pages, 4500 KiB  
Article
Cost-Effective Bimetallic Catalysts for Green H2 Production in Anion Exchange Membrane Water Electrolyzers
by Sabrina Campagna Zignani, Marta Fazio, Mariarosaria Pascale, Chiara Alessandrello, Claudia Triolo, Maria Grazia Musolino and Saveria Santangelo
Nanomaterials 2025, 15(13), 1042; https://doi.org/10.3390/nano15131042 - 4 Jul 2025
Viewed by 441
Abstract
Green hydrogen production from water electrolysis (WE) is one of the most promising technologies to realize a decarbonized future and efficiently utilize intermittent renewable energy. Among the various WE technologies, the emerging anion exchange membrane (AEMWE) technology shows the greatest potential for producing [...] Read more.
Green hydrogen production from water electrolysis (WE) is one of the most promising technologies to realize a decarbonized future and efficiently utilize intermittent renewable energy. Among the various WE technologies, the emerging anion exchange membrane (AEMWE) technology shows the greatest potential for producing green hydrogen at a competitive price. To achieve this goal, simple methods for the large-scale synthesis of efficient and low-cost electrocatalysts are needed. This paper proposes a very simple and scalable process for the synthesis of nanostructured NiCo- and NiFe-based electrode materials for a zero-gap AEMWE full cell. For the preparation of the cell anode, oxides with different Ni molar fractions (0.50 or 0.85) are synthesized by the sol–gel method, followed by calcination in air at different temperatures (400 or 800 °C). To fabricate the cell cathode, the oxides are reduced in a H2/Ar atmosphere. Electrochemical testing reveals that phase purity and average crystal size significantly influence cell performance. Highly pure and finely grained electrocatalysts yield higher current densities at lower overpotentials. The best performing membrane electrode assembly exhibits a current density of 1 A cm−2 at 2.15 V during a steady-state 150 h long stability test with 1 M KOH recirculating through the cell, the lowest series resistance at any cell potential (1.8 or 2.0 V), and the highest current density at the cut-off voltage (2.2 V) both at the beginning (1 A cm−2) and end of tests (1.78 A cm−2). The presented results pave the way to obtain, via simple and scalable techniques, cost-effective catalysts for the production of green hydrogen aimed at a wider market penetration by AEMWE. Full article
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24 pages, 4363 KiB  
Article
Ni Supported on Pr-Doped Ceria as Catalysts for Dry Reforming of Methane
by Antonella R. Ponseggi, Amanda de C. P. Guimarães, Renata O. da Fonseca, Raimundo C. Rabelo-Neto, Yutao Xing, Andressa A. A. Silva, Fábio B. Noronha and Lisiane V. Mattos
Processes 2025, 13(7), 2119; https://doi.org/10.3390/pr13072119 - 3 Jul 2025
Viewed by 438
Abstract
The use of CH4 and CO2 as fuels in direct internal reforming solid oxide fuel cells (DIR-SOFCs) is a promising strategy for efficient power generation with reduced greenhouse gas emissions. In this study, Ni catalysts supported on Ce–Pr mixed oxides with [...] Read more.
The use of CH4 and CO2 as fuels in direct internal reforming solid oxide fuel cells (DIR-SOFCs) is a promising strategy for efficient power generation with reduced greenhouse gas emissions. In this study, Ni catalysts supported on Ce–Pr mixed oxides with varying Pr contents (0–80 mol%) were synthesized, calcined at 1200 °C, and tested for dry reforming of methane (DRM), aiming at their application as catalytic layers in SOFC anodes. Physicochemical characterization (XRD, TPR, TEM) showed that increasing Pr loading enhances catalyst reducibility and promotes the formation of the Pr2NiO4 phase, which contributes to the generation of smaller Ni0 particles after reduction. Catalytic tests revealed that all samples exhibited low-carbon deposition, attributed to the large Ni crystallites. The catalyst with 80 mol% Pr showed the best performance, achieving the highest CH4 conversion (72%), a H2/CO molar ratio of 0.89, and improved stability. These findings suggest that Ni/Ce0.2Pr0.8 could be a promising candidate for use as a catalyst layer of anodes in DIR-SOFC anodes. Although electrochemical data are not yet available, future work will evaluate the catalyst’s performance and durability under SOFC-relevant conditions. Full article
(This article belongs to the Special Issue Advances in Synthesis and Applications of Supported Nanocatalysts)
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18 pages, 4392 KiB  
Article
Trimethylamine Gas Sensor Based on Electrospun In2O3 Nanowires with Different Grain Sizes for Fish Freshness Monitoring
by Xiangrui Dong, Bo Zhang, Mengyao Shen, Qi Lu, Hao Shen, Yi Ni, Yuechen Liu and Haitao Song
Chemosensors 2025, 13(6), 218; https://doi.org/10.3390/chemosensors13060218 - 14 Jun 2025
Viewed by 2421
Abstract
Seafood, especially marine fish, is highly prone to spoilage during processing, transportation, and storage. It releases pungent trimethylamine (TMA) gas, which severely affects food quality and safety. Metal–oxide–semiconductor (MOS) gas sensors for TMA detection offer a rapid, convenient, and accurate method for assessing [...] Read more.
Seafood, especially marine fish, is highly prone to spoilage during processing, transportation, and storage. It releases pungent trimethylamine (TMA) gas, which severely affects food quality and safety. Metal–oxide–semiconductor (MOS) gas sensors for TMA detection offer a rapid, convenient, and accurate method for assessing fish freshness. Indium oxide (In2O3) has shown potential as an effective sensing material for the detection of TMA. In this work, one-dimensional In2O3 nanowires with different grain sizes and levels of crystallinity were synthetized using the electrospinning technique and underwent different thermal calcination processes. Gas-sensing tests showed that the In2O3–3 °C/min–500 °C gas sensor exhibited an outstanding performance, including a high response (Ra/Rg = 47.0) to 100 ppm TMA, a short response time (6 s), a low limit of detection (LOD, 0.0392 ppm), and an excellent long-term stability. Furthermore, the sensor showed promising experimental results in monitoring the freshness of Larimichthys crocea (L. crocea). By analyzing the relationship between the grain size and crystallinity of the In2O3 samples, a mechanism for the enhanced gas-sensing performance was proposed. This work provides a novel strategy for designing and fabricating gas sensors for TMA detection and highlights their potential for broad applications in real-time fish freshness monitoring. Full article
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23 pages, 6740 KiB  
Article
Stabilization of Clay Soils Using a Lime Derived from Seashell
by Luis Carlos Suárez López, Juan Carlos López Ramos, Yamid E. Nuñez de la Rosa, Giovani Jordi Bruschi and Jair de Jesús Arrieta Baldovino
Materials 2025, 18(12), 2723; https://doi.org/10.3390/ma18122723 - 10 Jun 2025
Viewed by 540
Abstract
The valorization of mollusk shell waste offers a promising alternative to conventional binders in soil stabilization, contributing to circular economy strategies and improved solid waste management. This study aimed to evaluate the mechanical and microstructural behavior of clayey soil stabilized with Waste Seashell [...] Read more.
The valorization of mollusk shell waste offers a promising alternative to conventional binders in soil stabilization, contributing to circular economy strategies and improved solid waste management. This study aimed to evaluate the mechanical and microstructural behavior of clayey soil stabilized with Waste Seashell Lime (WSL), a binder produced by calcining crushed snail and mussel shells at different temperatures (700–900 °C) and durations (2–4 h). A recommended calcination condition (800 °C for 2 h) was selected based on thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) results. WSL was incorporated at 3%, 7%, and 11% by dry soil weight and activated using NaOH at molarities ranging from 0.5 to 2.0 mol/L. A total of 122 specimens were prepared and tested for unconfined compressive strength (UCS) after 7 and 28 days. The highest UCS (4605 kPa) was recorded for the mix with 11% WSL and 1.0 mol/L NaOH at 28 days. At lower contents (3% and 7%), WSL-treated soils outperformed those stabilized with Type III Portland cement (Type III PC) under the same curing conditions. SEM-EDS analysis revealed the formation of cementitious phases, such as C–S–H and C–A–S–H, and factorial ANOVA confirmed the statistical significance of the WSL content, curing time, and alkali concentration. These results confirm the research hypothesis and demonstrate that alkali-activated WSL, derived from marine shell waste, can serve as a technically viable binder while supporting circular economy principles and waste reuse practices. Full article
(This article belongs to the Section Construction and Building Materials)
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16 pages, 5202 KiB  
Article
Active Sites in Low-Loaded Copper-Exchanged Mordenite: Spectroscopic and Stability Study for Methane Oxidation Using Mild Conditions
by Rodrigo Mojica, Marlene González-Montiel, Daniel Ramírez-Rosales, Paula M. Crespo-Barrera and Amado Enrique Navarro-Frómeta
Processes 2025, 13(6), 1795; https://doi.org/10.3390/pr13061795 - 5 Jun 2025
Viewed by 446
Abstract
Low-loaded copper-exchanged mordenite samples (3 wt.% of copper) were prepared by a solid-state milling method using controlled conditions. The milled samples were then submitted to a calcination process where trimeric copper active species were formed, according to XPS, EPR, IR, and UV–vis recorded [...] Read more.
Low-loaded copper-exchanged mordenite samples (3 wt.% of copper) were prepared by a solid-state milling method using controlled conditions. The milled samples were then submitted to a calcination process where trimeric copper active species were formed, according to XPS, EPR, IR, and UV–vis recorded spectra. To verify the interaction of the active site with methane at mild conditions, a test experimental design was developed in a batch reactor configuration using mild two-step conditions: (1) activation temperature at 400 °C in an air atmosphere, and (2) isothermal conversion process at 200 °C with 6 bar methane. The analyzed samples were active in methanol conversion in batch conditions, nonetheless less efficient than the usually reported copper mono μ-oxo sites using harder experimental conditions. The herein reported copper active sites are as follows: a trinuclear copper active cluster [Cu3(μ-O)3]2+ and a possible intermediate during methane contact detected as bis(μ-oxo) dicopper species were identified and studied on each reaction step. This study revealed that trinuclear copper active sites can be obtained through grinding. Nonetheless, they stabilize after a calcination stage in an air atmosphere. Their stability is then maintained during the whole cyclic experimental test, suggesting their potential use for multicyclic processes. Full article
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30 pages, 4630 KiB  
Article
Moderate-Temperature Carbon Capture Using Thermally Pre-Treated Dolomite: A Novel Approach
by Iyiade G. Alalade, Javier E. Morales-Mendoza, Alma B. Jasso-Salcedo, Jorge L. Domínguez-Arvizu, Blanca C. Hernández-Majalca, Hammed A. Salami, José L. Bueno-Escobedo, Luz I. Ibarra-Rodriguez, Alejandro López-Ortiz and Virginia H. Collins-Martínez
C 2025, 11(2), 37; https://doi.org/10.3390/c11020037 - 5 Jun 2025
Viewed by 1922
Abstract
This study investigates a novel approach to moderate-temperature carbon capture by examining the enhanced performance of thermally pre-treated dolomite. To obtain mixed oxides, dolomite samples were prepared via calcination in a quartz cylindrical furnace under an ambient atmosphere at 900 °C, and subsequently [...] Read more.
This study investigates a novel approach to moderate-temperature carbon capture by examining the enhanced performance of thermally pre-treated dolomite. To obtain mixed oxides, dolomite samples were prepared via calcination in a quartz cylindrical furnace under an ambient atmosphere at 900 °C, and subsequently thermally pre-treated under an inert (argon) stream at 650 °C. Characterization of the as-prepared samples involved morphological, structural, textural, and optical features examined through XRD, BET, SEM-EDS, FT-IR, and RAMAN, XPS, and UV-vis spectroscopy, whereas TGA and subsequent multicyclic tests were used to study the CO2 sorption. The dolomite sample calcined at 900 °C for 60 min, and after being activated under an inert atmosphere (argon), labeled PCD60Act, exhibited the highest CO2 uptake of 0.477 gCO2/gsorbent; after 15 sorption–regeneration cycles, it still retained a CO2 uptake of 0.38 gCO2/gsorbent at 650 °C, and it was also successfully regenerated at this moderate temperature, demonstrating 84% capture capacity retention. These remarkable results are explained by the crystalline defects generated during the thermal pre-treatments of the dolomite. This research offers valuable perspectives on the viability of employing thermally pre-treated dolomite as an inexpensive, thermally stable, and moderate-temperature regenerable CaO-based sorbent for applications in CO2 removal in the context of integrated carbon capture and conversion (ICCC) for the production of high-purity hydrogen. Full article
(This article belongs to the Section Carbon Cycle, Capture and Storage)
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