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Keywords = packed-bed

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24 pages, 2278 KiB  
Article
Performance Analysis of Silica Fluidized Bed Membrane Reactor for Hydrogen Production as a Green Process Using CFD Modelling
by Maryam Barmaki, Elham Jalilnejad, Kamran Ghasemzadeh and Adolfo Iulianelli
Membranes 2025, 15(8), 248; https://doi.org/10.3390/membranes15080248 - 18 Aug 2025
Viewed by 176
Abstract
The main aim of this study deals with the potential evaluation of a fluidized bed membrane reactor (FBMR) for hydrogen production as a clean fuel carrier via methanol steam reforming reaction, comparing its performance with other reactors including packed bed membrane reactors (PBMR), [...] Read more.
The main aim of this study deals with the potential evaluation of a fluidized bed membrane reactor (FBMR) for hydrogen production as a clean fuel carrier via methanol steam reforming reaction, comparing its performance with other reactors including packed bed membrane reactors (PBMR), fluidized bed reactors (FBR), and packed bed reactors (PBR). For this purpose, a two-dimensional, axisymmetric numerical model was developed using computational fluid dynamics (CFD) to simulate the reactor performances. Model accuracy was validated by comparing the simulation results for PBMR and PB with experimental data, showing an accurate agreement within them. The model was then employed to examine the effects of key operating parameters, including reaction temperature, pressure, steam-to-methanol molar ratio, and gas volumetric space velocity, on reactor performance in terms of methanol conversion, hydrogen yield, hydrogen recovery, and selectivity. At 573 K, 1 bar, a feed molar ratio of 3/1, and a space velocity of 9000 h−1, the PBMR reached the best results in terms of methanol conversion, hydrogen yield, hydrogen recovery, and hydrogen selectivity, such as 67.6%, 69.5%, 14.9%, and 97.1%, respectively. On the other hand, the FBMR demonstrated superior performance with respect to the latter reaching a methanol conversion of 98.3%, hydrogen yield of 95.8%, hydrogen recovery of 74.5%, and hydrogen selectivity of 97.4%. These findings indicate that the FBMR offers significantly better performance than the other reactor types studied in this work, making it a highly efficient method for hydrogen production through methanol steam reforming, and a promising pathway for clean energy generation. Full article
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20 pages, 7249 KiB  
Article
Enhanced Degradation of 4-Nitrophenol via a Two-Stage Co-Catalytic Fenton Packed-Bed Reactor with External Circulation
by Yan Liu, Jingyu Liu, Yongyou Hu, Yueyue Shi, Chaoyang Tang, Jianhua Cheng, Xiaoqiang Zhu, Guobin Wang and Jieyun Xie
Environments 2025, 12(8), 280; https://doi.org/10.3390/environments12080280 - 14 Aug 2025
Viewed by 413
Abstract
To mitigate the consumption of active sites on co-catalysts by H2O2 and to enhance the efficiency and stability of co-catalytic Fenton reactions, an external circulation two-stage packed-bed reactor (ECTPBR) was developed using DPW (diatomite plate@polydopamine@WC) as a co-catalyst to degrade [...] Read more.
To mitigate the consumption of active sites on co-catalysts by H2O2 and to enhance the efficiency and stability of co-catalytic Fenton reactions, an external circulation two-stage packed-bed reactor (ECTPBR) was developed using DPW (diatomite plate@polydopamine@WC) as a co-catalyst to degrade 4-nitrophenol (4-NP). Under suitable conditions, the ECTPBR could achieve over 91.97% 4-NP degradation, with low iron sludge production (11.97 mg/L) and minimal tungsten leaching (3.6363 mg/L). The two-stage strategy enabled spatial separation of Fe3+ reduction and Fenton reactions, minimizing the loss of active sites on DPW, ensuring long-term system stability, and reducing the toxicity of 4-NPdegradation products. In addition, external circulation enhanced mass transfer and improved resistance to shock loads. These advantages suggest that the ECTPBR may serve as an effective strategy for applying co-catalytic Fenton reactions in the treatment of toxic and refractory organic wastewater. Full article
(This article belongs to the Special Issue Advances in Heavy Metal Remediation Technologies)
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25 pages, 4421 KiB  
Review
Advances in Solid Particle Thermal Energy Storage: A Comprehensive Review
by Guang Zeng, Shijie Hou, Qiankun Guo, Yongtie Cai and Mobei Xu
Sustainability 2025, 17(16), 7244; https://doi.org/10.3390/su17167244 - 11 Aug 2025
Viewed by 533
Abstract
Solid particle thermal energy storage technology demonstrates extraordinary thermal stability across wide temperature ranges and possesses significant cost-effectiveness that meets stringent economic requirements for long-duration energy storage. These distinctive characteristics enable this technology to continuously support increasing decarbonization demands and drive the strategic [...] Read more.
Solid particle thermal energy storage technology demonstrates extraordinary thermal stability across wide temperature ranges and possesses significant cost-effectiveness that meets stringent economic requirements for long-duration energy storage. These distinctive characteristics enable this technology to continuously support increasing decarbonization demands and drive the strategic progression of sustainable energy transformations. This review work conducts a thorough analysis of three representative reactor types: packed beds, moving beds, and fluidized beds, focusing on how particle thermophysical properties affect heat transfer and storage performance. The paper analyzes pressure drop and heat transfer correlations to reveal the coupling effects between particles and working fluids that impact system efficiency. By comparing hydrodynamic behavior across different reactor types, the study identifies optimization strategies and technical challenges. The review paper concludes by outlining future research directions for enhancing system efficiency, supporting industrial deployment, and facilitating integration with next-generation renewable energy technologies. Full article
(This article belongs to the Special Issue Innovative Pathways of Renewable Energy for Sustainable Development)
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19 pages, 2630 KiB  
Article
Experimental and Kinetic Modelling Study of the Heterogeneous Catalytic Conversion of Bioethanol into n-Butanol Using MgO–Al2O3 Mixed Oxide Catalyst
by Amosi Makoye, Anna Vikár, András Bence Nacsa, Róbert Barthos, József Valyon, Ferenc Lónyi and Tibor Nagy
Catalysts 2025, 15(8), 709; https://doi.org/10.3390/catal15080709 - 25 Jul 2025
Viewed by 374
Abstract
Ethanol upgrading via catalytic C–C coupling, commonly known as the Guerbet reaction, offers a sustainable route to produce 1-butanol, a high-performance biofuel. To address gaps in the mechanistic understanding of the catalytic reaction, we investigated the process involving a fixed-bed reactor, operated at [...] Read more.
Ethanol upgrading via catalytic C–C coupling, commonly known as the Guerbet reaction, offers a sustainable route to produce 1-butanol, a high-performance biofuel. To address gaps in the mechanistic understanding of the catalytic reaction, we investigated the process involving a fixed-bed reactor, operated at 275–325 °C, 21 bar, and weight hourly space velocities of 0.25–2.5 gEtOH/(gcat·h), using helium as a carrier gas, with a 5:1 He/EtOH molar ratio. The catalyst was a MgO–Al2O3 mixed oxide (Mg/Al = 2:1), derived from a hydrotalcite precursor. A detailed kinetic model was developed, encompassing 15 species and 27 reversible steps (10 sorption and 17 reaction steps), within a 1+1D sorption–reaction–transport framework. Four C4-forming pathways were included: aldol condensation to form crotonaldehyde, semi-direct coupling to form butyraldehyde and crotyl alcohol, and direct coupling to form 1-butanol. To avoid overfitting, Arrhenius parameters were grouped by reaction type, resulting in sixty rate parameters and one active site-specific density parameter. The optimized model achieved high accuracy, with an average prediction error of 1.44 times the experimental standard deviation. The mechanistic analysis revealed aldol condensation as the dominant pathway below 335 °C, with semi-direct coupling to crotyl alcohol prevailing above 340 °C. The resulting model provides a robust framework for understanding and predicting complex reaction networks in ethanol upgrading systems. Full article
(This article belongs to the Special Issue Biomass Catalytic Conversion to Value-Added Chemicals)
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22 pages, 8896 KiB  
Article
Synergistic Sequestration and Hydroxyapatite-Based Recovery of Phosphorus by the Coupling Process of CaCl2/Modified Oyster Shell and Circulating Fluidized Bed Reactor
by Xuejun Long, Nanshan Yang, Huiqi Wang, Jun Fang, Rui Wang, Zhenxing Zhong, Peng Yu, Xuelian Xu, Hao Huang, Jun Wan, Xiejuan Lu and Xiaohui Wu
Catalysts 2025, 15(8), 706; https://doi.org/10.3390/catal15080706 - 24 Jul 2025
Viewed by 442
Abstract
A novel modified oyster shell (MOS-800) was developed to enhance phosphorus sequestration and recovery from wastewater. Approximately 33.3% of phosphate was eliminated by the MOS-800, which also exhibited excellent pH regulation capabilities. In semicontinuous tests, a synergistic phosphorus separation was achieved through the [...] Read more.
A novel modified oyster shell (MOS-800) was developed to enhance phosphorus sequestration and recovery from wastewater. Approximately 33.3% of phosphate was eliminated by the MOS-800, which also exhibited excellent pH regulation capabilities. In semicontinuous tests, a synergistic phosphorus separation was achieved through the coupling process of CaCl2/MOS-800 and a circulating fluidized bed (CFB), resulting in an 86.5% phosphate separation. In continuous flow experiments, phosphorus elimination reached 98.2%. Material characterization revealed that hydroxyapatite (HAP) was the primary component of the crystallized products. Additionally, MOS-800 released 506.5–572.2 mg/g Ca2+ and 98.1 mg/g OH. A four-stage heterogeneous crystallization mechanism was proposed for the coupling process. In the first stage, Ca2+ quickly reacted with phosphate to form Ca-P ion clusters, etc. In the second stage, these clusters packed randomly to form spherical amorphous calcium phosphate (ACP). In the third stage, the ACP spheres were transformed and rearranged into sheet-like HAP crystallites, Finally, in the fourth stage, the HAP crystallites aggregated on the surface of crystal seeds, also with the addition of crystal seeds and undissolved MOS-800, potentially catalyzing the heterogeneous crystallization. These findings suggest that the CaCl2/MOS-800/CFB system is a promising technique for phosphate recovery from wastewater. Full article
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22 pages, 2359 KiB  
Article
Investigation of the Charging and Discharging Cycle of Packed-Bed Storage Tanks for Energy Storage Systems: A Numerical Study
by Ayah Marwan Rabi’, Jovana Radulovic and James M. Buick
Thermo 2025, 5(3), 24; https://doi.org/10.3390/thermo5030024 - 18 Jul 2025
Viewed by 297
Abstract
In recent years, packed-bed systems have emerged as an attractive design for thermal energy storage systems due to their high thermal efficiency and economic feasibility. As integral components of numerous large-scale applications systems, packed-bed thermal energy stores can be successfully paired with renewable [...] Read more.
In recent years, packed-bed systems have emerged as an attractive design for thermal energy storage systems due to their high thermal efficiency and economic feasibility. As integral components of numerous large-scale applications systems, packed-bed thermal energy stores can be successfully paired with renewable energy and waste heat to improve energy efficiency. An analysis of the thermal performances of two packed beds (hot and cold) during six-hour charging and discharging cycles has been conducted in this paper using COMSOL Multiphysics software, utilizing the optimal design parameters that have been determined in previous studies, including porosity (0.2), particle diameters (4 mm) for porous media, air as a heat transfer fluid, magnesia as a storage medium, mass flow rate (13.7 kg/s), and aspect ratio (1). The performance has been evaluated during both the charging and discharging cycles, in terms of the system’s capacity factor, the energy stored, and the thermal power, in order to understand the system’s performance and draw operational recommendations. Based on the results, operating the hot/cold storage in the range of 20–80% of the full charge was found to be a suitable range for the packed-bed system, ensuring that the charging/discharging power remains within 80% of the maximum. Full article
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16 pages, 1925 KiB  
Article
Simulation of Pb(II) and Ni(II) Adsorption in a Packed Column: Effects of Bed Height, Flow Rate, and Initial Concentration on Performance Metrics
by Candelaria Tejada-Tovar, Ángel Villabona-Ortíz, Ángel Gonzalez-Delgado, Rodrigo Ortega-Toro and Sebastián Ortega-Puente
Processes 2025, 13(7), 2141; https://doi.org/10.3390/pr13072141 - 5 Jul 2025
Cited by 1 | Viewed by 401
Abstract
Numerous studies have been conducted employing various techniques to remove pollutants from water bodies. Among these techniques, adsorption a surface phenomenon that utilises adsorbents derived from agricultural residues has shown considerable potential for the removal of contaminants such as heavy metals. However, most [...] Read more.
Numerous studies have been conducted employing various techniques to remove pollutants from water bodies. Among these techniques, adsorption a surface phenomenon that utilises adsorbents derived from agricultural residues has shown considerable potential for the removal of contaminants such as heavy metals. However, most of these investigations have been carried out at the laboratory scale, with limited efforts directed towards predicting the performance of these systems at an industrial level. Accordingly, the present study aims to model a packed bed column at industrial scale for the removal of Pb(II) and Ni(II) ions from aqueous solutions, employing biomass derived from oil palm residues as the adsorbent material. To achieve this, Aspen Adsorption was used as a modelling and simulation tool to evaluate the impact of bed height, inlet flow rate, and initial concentration through a parametric assessment. This evaluation incorporated the Freundlich, Langmuir, and Langmuir–Freundlich isotherm models in conjunction with the Linear Driving Force (LDF) kinetic model. The results indicated that the optimal operating parameters included a column height of 5 m, a flow rate of 250 m3/day, and an initial metal concentration of 5000 mg/L. Moreover, all models demonstrated removal efficiencies of up to 94.6% for both Pb(II) and Ni(II). An increase in bed height resulted in longer breakthrough and saturation times but led to a reduction in adsorption efficiency. Conversely, higher flow rates shortened these times yet enhanced efficiency. These findings underscore the potential of computational modelling tools as predictive instruments for evaluating the performance of adsorption systems at an industrial scale. Full article
(This article belongs to the Special Issue Separation Processes for Environmental Preservation)
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19 pages, 3824 KiB  
Article
Thermostable D-Allulose 3-Epimerase for Long-Term Food-Compatible Continuous Production Systems
by Jiawei Cui, Yan Li and Ming Yan
Appl. Sci. 2025, 15(13), 7318; https://doi.org/10.3390/app15137318 - 29 Jun 2025
Viewed by 429
Abstract
D-allulose is a rare sugar with promising applications in food and health industries, owing to its low caloric value and multiple health benefits. In this study, we systematically investigated a thermostable D-allulose 3-epimerase (TcDAEase) from Thermogemmatispora carboxidivorans for food-compatible continuous production. The enzyme [...] Read more.
D-allulose is a rare sugar with promising applications in food and health industries, owing to its low caloric value and multiple health benefits. In this study, we systematically investigated a thermostable D-allulose 3-epimerase (TcDAEase) from Thermogemmatispora carboxidivorans for food-compatible continuous production. The enzyme exhibited remarkable thermostability, with over 70% activity retained at 80 °C, and showed broad pH tolerance across the range of 8.0 to 13.0. Notably, TcDAEase exhibited high catalytic activity toward D-allulose and D-fructose even without the addition of metal ions. Moreover, food-grade Mg2+ was identified as enhancing enzyme activity by 14.3%, thus ensuring compliance with Generally Recognized as Safe (GRAS) standards for food applications. To improve industrial applicability, the enzyme was immobilized using a chitosan-diatomaceous earth (DE) matrix via three-step adsorption–crosslinking–embedding strategy. The immobilized TcDAEase achieved 48.7% ± 2.4% activity recovery and retained 90.3% ± 1.5% activity over seven reaction cycles. Furthermore, continuous production of D-allulose was realized in a packed-bed reactor, operating stably at 60 °C, pH 8.0 and 5 mM Mg2+ for 150 days, producing 756 kg of D-allulose with a conversion yield exceeding 89.7% of the theoretical maximum. Overall, this study provides a feasible strategy for the continuous and efficient production of high-value-added D-allulose in the food industry. Full article
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18 pages, 2688 KiB  
Article
Synergistic Effects of a Packed Bed Bipolar Electrolysis System Combined with Activated Carbon for Efficient Treatment of Dyeing Wastewater
by Hyung-kyu Lee, Go-eun Kim, Seong-ho Jang and Young-chae Song
Water 2025, 17(13), 1911; https://doi.org/10.3390/w17131911 - 27 Jun 2025
Viewed by 401
Abstract
Textile dyeing wastewater is one of the most challenging industrial effluents to treat due to its high concentrations of persistent organic compounds and nitrogenous substances. Conventional treatment methods often fall short in achieving both sufficient removal efficiency and environmental safety. In this study, [...] Read more.
Textile dyeing wastewater is one of the most challenging industrial effluents to treat due to its high concentrations of persistent organic compounds and nitrogenous substances. Conventional treatment methods often fall short in achieving both sufficient removal efficiency and environmental safety. In this study, we aimed to remove the total nitrogen (T-N) and total organic carbon (TOC) of dyeing wastewater from an industrial complex in D City, Korea, by applying bipolar and packed bipolar electrolysis using aluminum (Al) electrodes and activated carbon (AC). The system was operated for 60 min under varying conditions of applied voltage (5–15 V), electrolyte type and concentration (non-addition, NaCl 5 mM, NaCl 10 mM, Na2SO4 5 mM, Na2SO4 10 mM), and AC packing amount (non-addition or 100 g/L). The highest T-N and TOC removal efficiencies were observed at 15 V, reaching 69.53% and 63.68%, respectively. Electrolyte addition significantly improved initial treatment performance, with NaCl 10 mM showing the best results. However, Al leaching also increased, from 549.83 mg/L (non-addition) to 623.06 mg/L (NaCl 10 mM). When AC was used without electrolysis (control experiment), the T-N and TOC removal efficiencies were limited to 30.24% and 29.86%, respectively. In contrast, AC packing combined with 15 V electrolysis under non-addition achieved 86.04% T-N and 77.98% TOC removal, while also reducing Al leaching by 40.12%. These results suggested that electrochemical treatment with AC packing under non-addition conditions offers the best balance between high treatment efficiency and low environmental impact. These findings demonstrate that the synergistic use of packed activated carbon and electrochemical treatment under additive-free conditions can overcome the limitations of conventional methods. This study contributes to the development of more sustainable and effective technologies for treating high-strength industrial wastewater. Full article
(This article belongs to the Special Issue Adsorption Technologies in Wastewater Treatment Processes)
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21 pages, 1361 KiB  
Article
Anhydrous Ethanol Production from Discarded Fruits Using Fermentation and a Green Dehydration System
by Margarita Ramírez-Carmona, Leidy Rendón-Castrillón, Carlos Ocampo-López, Manuela García-Ríos, Xiomy Lamilla-Mendoza, Sebastián Piedrahíta-Pérez, Juliana Rodríguez-Estrada, Valerie Samaan-Salazar, Samuel Urrea-López, Daniel Valencia-Yepes and Santiago Zea-Gutiérrez
Processes 2025, 13(6), 1854; https://doi.org/10.3390/pr13061854 - 12 Jun 2025
Viewed by 867
Abstract
This study explores the production of anhydrous ethanol from discarded fruits, aiming to determine optimal fermentation conditions and evaluate the feasibility of a green separation technology. Fermentation experiments were performed using juices from Psidium guajava (S1), Carica paapaya (S2), and mucilage residues of [...] Read more.
This study explores the production of anhydrous ethanol from discarded fruits, aiming to determine optimal fermentation conditions and evaluate the feasibility of a green separation technology. Fermentation experiments were performed using juices from Psidium guajava (S1), Carica paapaya (S2), and mucilage residues of Coffea arabica (S3). All fermentations were carried out at a pH of 4.5 for 7 days in 1 L bioreactors. A full 22 factorial design was applied to evaluate the effects of two variables: yeast type (commercial Saccharomyces cerevisiae [CY] vs. native yeast [NY]) and temperature (21 °C vs. 30 °C). Higher ethanol concentrations were achieved with CY at 30 °C, yielding 6.79% ethanol for S3. A multi-criteria matrix prioritized coffee residues due to their high ethanol yield, biomass availability, and economic viability. The ethanol was dehydrated using a packed-bed bioadsorption system with crushed corn, which increased purity from 6.7% v/v to 98.9% v/v in two stages, while avoiding azeotropic limitations. Energy analysis revealed low specific consumption (3.68 MJ/kg), outperforming conventional distillation. The results of this study, obtained at operating temperatures of 30 °C and 21 °C, a pH of 4.5, and an operating time of 7 days in a 1L bioreactor, demonstrate ethanol concentrations of 6.79%, confirming the technical feasibility of using agricultural waste as a raw material and validating the efficiency of a bioadsorption-based dehydration system. These findings address the current gap in integrating green ethanol separation with low-cost agricultural residues and highlight a sustainable alternative for decentralized bioethanol production. Full article
(This article belongs to the Special Issue Green Separation and Purification Processes)
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16 pages, 4129 KiB  
Article
Quaternary Amine-Functionalized Reed Straw Bioadsorbent: Synergistic Phosphate Recovery and Sustainable Nutrient Recycling in Circular Economy Systems
by Zhan Yang, Qi Zhang, Changyi Liu, Haodong Zhang and Zhe Qin
Sustainability 2025, 17(12), 5301; https://doi.org/10.3390/su17125301 - 8 Jun 2025
Viewed by 548
Abstract
The scarcity of phosphorus resources and the excessive accumulation of phosphates in aquatic environments pose significant threats to ecological systems and human health, while traditional treatment methods often fail to achieve effective resource recovery and reuse. This study aims to develop an efficient [...] Read more.
The scarcity of phosphorus resources and the excessive accumulation of phosphates in aquatic environments pose significant threats to ecological systems and human health, while traditional treatment methods often fail to achieve effective resource recovery and reuse. This study aims to develop an efficient method for phosphate removal and resource recycling through the modification of reed straw (MRS) by introducing amine groups. Key operational parameters such as packed bed height, flow velocity, and initial solute concentration were systematically investigated to optimize MRS’s adsorption efficiency. Experimental results demonstrated that under optimized conditions, MRS achieved a maximum phosphate adsorption capacity of 8.337 mg/g and maintained over 80% efficiency after nine adsorption–desorption cycles. Utilizing the desorbed solution as a nutrient solution significantly enhanced maize seedling growth, increasing stem height by 23.8%, fresh weight by 51.3%, and phosphorus content by 80.7%. These findings highlight MRS’s potential, not only as an effective phosphate adsorbent, but also as a means of successful phosphorus resource recovery and recycling, indicating promising applications in environmental remediation and resource management. Full article
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23 pages, 2069 KiB  
Article
Evaluating the Odor Mitigation Effects of Biochar-Enhanced Bedding Materials in a Simulated Bedded Pack Dairy Barn Environment: A Laboratory-Scale Study
by Jinho Shin, Daehun Kim, Yangjoon Lee, Seunghun Lee, Riuh Wardhani and Heekwon Ahn
Appl. Sci. 2025, 15(11), 6361; https://doi.org/10.3390/app15116361 - 5 Jun 2025
Viewed by 933
Abstract
This study evaluated the odor mitigation potential of rice husk biochar in a simulated dairy bedded pack over 21 days. Biochar was incorporated into a dairy manure–sawdust mixture at 5% and 10% dry weight. Emissions of key odorous compounds—ammonia (NH3), sulfur [...] Read more.
This study evaluated the odor mitigation potential of rice husk biochar in a simulated dairy bedded pack over 21 days. Biochar was incorporated into a dairy manure–sawdust mixture at 5% and 10% dry weight. Emissions of key odorous compounds—ammonia (NH3), sulfur compounds, volatile fatty acids, phenol, p-cresol, and indole—were evaluated. Odor units were assessed to determine perceived odor reduction. Biochar significantly reduced NH3 and dimethyl sulfide (DMS) emissions: NH3 by 27% and 43%, and DMS by 53% and 75%, at 5% and 10% application, respectively. The NH3 reduction was attributed to ammoniacal nitrogen adsorption, while the DMS reduction likely resulted from enhanced air permeability suppressing anaerobic bacterial activity. The 5% biochar treatment, achieving 63% and 70% of the NH3 and DMS reductions attained by the 10% treatment, respectively, offers a more practical and cost-effective option. Other odorous compounds were not significantly affected. A temporary reduction in odor units was observed on day 7. Rice husk biochar contains 14.5% atomic Si, primarily as silica, which supports structural stability but hinders pore development, reducing adsorption efficiency. These findings demonstrate the importance of biochar’s physicochemical properties in odor mitigation. Future research should evaluate long-term field performance, microbial interactions, and silica modification strategies. Full article
(This article belongs to the Section Agricultural Science and Technology)
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14 pages, 1115 KiB  
Article
Development of an Innovative and Sustainable Technological Process for Biogas Purification Through the Reuse of Autoclaved Aerated Concrete Waste
by Eric Dumont, Noé Kautzmann and Annabelle Couvert
Processes 2025, 13(6), 1767; https://doi.org/10.3390/pr13061767 - 3 Jun 2025
Viewed by 542
Abstract
This study demonstrated the effectiveness of using autoclaved aerated concrete AAC waste as a low-cost filtering material for removing hydrogen sulfide (H2S) from gas streams. A long-term experiment (89 days) was conducted in a packed bed reactor to purify synthetic biogas [...] Read more.
This study demonstrated the effectiveness of using autoclaved aerated concrete AAC waste as a low-cost filtering material for removing hydrogen sulfide (H2S) from gas streams. A long-term experiment (89 days) was conducted in a packed bed reactor to purify synthetic biogas composed of N2, CO2, H2S, and O2. Optimal H2S removal efficiencies, reaching up to 100%, were achieved under highly acidic conditions (pH ≈ 1–3) and low oxygen concentrations (<1%). In the presence of oxygen, calcium oxides in the AAC waste react with H2S to form gypsum (CaSO4 2H2O). The simultaneous removal of both oxygen and H2S by AAC waste, following an approximate 2:1 molar ratio, may be particularly beneficial for biogas streams containing unwanted traces of oxygen. The transformation and lifespan of AAC waste were monitored through sulfur accumulation in the material and pressure drop measurements, which indicated structural changes in the AAC waste. At the end of its lifespan, the AAC waste exhibited an H2S removal capacity of 185 gH2S kgAAC−1. This innovative and sustainable process not only provides a cost-effective and environmentally sound solution for the simultaneous removal of H2S and O2 from biogas, but also promotes waste valorization and aligns with circular economy principles. Full article
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19 pages, 8327 KiB  
Article
Investigation of Ti65 Powder Spreading Behavior in Multi-Layer Laser Powder Bed Fusion
by Zhe Liu, Ju Wang, Ge Yu, Xiaodan Li, Meng Li, Xizhong An, Jiaqiang Ni, Haiyang Zhao and Qianya Ma
Appl. Sci. 2025, 15(11), 6220; https://doi.org/10.3390/app15116220 - 31 May 2025
Viewed by 469
Abstract
Powder bed fusion using a laser beam (PBF-LB) offers a suitable alternative to manufacturing Ti65 with intricate geometries and internal structures in hypersonic aerospace applications. However, issues such as undesirable surface roughness, defect formation, and microstructural inhomogeneity remain critical barriers to its wide [...] Read more.
Powder bed fusion using a laser beam (PBF-LB) offers a suitable alternative to manufacturing Ti65 with intricate geometries and internal structures in hypersonic aerospace applications. However, issues such as undesirable surface roughness, defect formation, and microstructural inhomogeneity remain critical barriers to its wide application. In this study, a coupled discrete element method–computational fluid dynamics (DEM-CFD) model was utilized to investigate the spreading behavior of Ti65 powder in a multi-layer PBF-LB process. The macro- and microscopic characteristics of the powder beds were systematically analyzed across different layers and regions under various spreading velocities. The results show that the packing density and uniformity of the powder beds in multi-layer PBF-LB of Ti65 powder improves as the number of solidified layers increases. Poor bed quality is observed in the first two layers due to a strong boundary effect, while a stable and denser powder bed emerges from the fourth layer. The presence of a previously solidified region strongly influences its neighboring unsolidified areas, enhancing density in the upstream region and causing looser packing downstream. Additionally, due to the existence of a solidified region, the height of the powder bed progressively decreases along the spreading direction. Full article
(This article belongs to the Special Issue Advanced Granular Processing Technologies and Applications)
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15 pages, 1574 KiB  
Article
Simulation and Parametric Evaluation of Pb (II) Adsorption in a Biomass-Packed Bed Using Isothermal Freundlich–LDF and Langmuir II–LDF Models
by Angel Villabona-Ortíz, Oscar E. Coronado-Hernández and Candelaria Tejada-Tovar
Processes 2025, 13(6), 1655; https://doi.org/10.3390/pr13061655 - 24 May 2025
Viewed by 648
Abstract
The objective of this study was to model an adsorption column bed with biomass residues using computational software to remove Pb (II) at the industrial level and analyse the effects of parametric variation. For this purpose, several simulations of the adsorption column were [...] Read more.
The objective of this study was to model an adsorption column bed with biomass residues using computational software to remove Pb (II) at the industrial level and analyse the effects of parametric variation. For this purpose, several simulations of the adsorption column were performed using Aspen Adsorption software, evaluating the effects of varied height, inlet flow rate, and initial concentration on the adsorption process performance. The Langmuir II and Freundlich models are established as isotherm models, and the linear driving force (LDF) model is established as the kinetic model. The findings showed that Freundlich–LDF obtained efficiencies of up to 99.9% and Langmuir II–LDF efficiencies of up to 99.7%. The optimal simulation conditions were a column height of 4 m, an initial Pb (II) concentration of 3000 mg/L, and an inlet flow rate of 250 m3/d. This study presents a novel engineering approach to predict the potential performance of columns packed with organic waste-derived biomasses in multi-scale Pb (II) removal using computer-aided engineering tools. Full article
(This article belongs to the Special Issue Modeling and Optimization for Multi-scale Integration)
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