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Search Results (2,484)

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Keywords = gas removal

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29 pages, 1496 KiB  
Article
Advanced and Robust Numerical Framework for Transient Electrohydrodynamic Discharges in Gas Insulation Systems
by Philipp Huber, Julian Hanusrichter, Paul Freden and Frank Jenau
Eng 2025, 6(8), 194; https://doi.org/10.3390/eng6080194 - 6 Aug 2025
Abstract
For the precise description of gas physical processes in high-voltage direct current (HVDC) transmission, an advanced and robust numerical framework for the simulation of transient particle densities in the course of corona discharges is developed in this work. The aim is the scalable [...] Read more.
For the precise description of gas physical processes in high-voltage direct current (HVDC) transmission, an advanced and robust numerical framework for the simulation of transient particle densities in the course of corona discharges is developed in this work. The aim is the scalable and consistent modeling of the space charge density under realistic conditions. The core component of the framework is a discontinuous Galerkin method that ensures the conservative properties of the underlying hyperbolic problem. The space charge density at the electrode surface is imposed as a dynamic boundary condition via Lagrange multipliers. To increase the numerical stability and convergence rate, a homotopy approach is also integrated. For the experimental validation, a measurement concept was realised that uses a subtraction method to specifically remove the displacement current component in the signal and thus enables an isolated recording of the transient ion current with superimposed voltage stresses. The experimental results on a small scale agree with the numerical predictions and prove the quality of the model. On this basis, the framework is transferred to hybrid HVDC overhead line systems with a bipolar design. In the event of a fault, significant transient space charge densities can be seen there, especially when superimposed with new types of voltage waveforms. The framework thus provides a reliable contribution to insulation coordination in complex HVDC systems and enables the realistic analysis of electrohydrodynamic coupling effects on an industrial scale. Full article
(This article belongs to the Section Electrical and Electronic Engineering)
16 pages, 2899 KiB  
Article
The Coupling Mechanism of the Electricity–Gas System and Assessment of Attack Resistance Based on Interdependent Networks
by Qingyu Zou and Lin Yan
Eng 2025, 6(8), 193; https://doi.org/10.3390/eng6080193 - 6 Aug 2025
Abstract
Natural gas plays a critical role in integrated energy systems. In this context, the present study proposes an optimization model for the electricity–gas coupling system, grounded in the theory of interdependent networks. By integrating network topology parameters with real-time operational metrics, the model [...] Read more.
Natural gas plays a critical role in integrated energy systems. In this context, the present study proposes an optimization model for the electricity–gas coupling system, grounded in the theory of interdependent networks. By integrating network topology parameters with real-time operational metrics, the model substantially enhances system robustness and adaptability. To quantify nodal vulnerability and importance, the study introduces two novel evaluation indicators: the Electric Potential–Closeness Fusion Indicator (EPFI) for power networks and the Pressure Difference–Closeness Comprehensive Indicator (PDCI) for natural gas systems. Leveraging these indicators, three coupling paradigms—assortative, disassortative, and random—are systematically constructed and analyzed. System resilience is assessed through simulation experiments incorporating three attack strategies: degree-based, betweenness centrality-based, and random node removal. Evaluation metrics include network efficiency and the variation in the size of the largest connected subgraph under different coupling configurations. The proposed framework is validated using a hybrid case study that combines the IEEE 118-node electricity network with a 20-node Belgian natural gas system, operating under a unidirectional gas-to-electricity energy flow model. Results confirm that the disassortative coupling configuration, based on EPFI and PDCI indicators, exhibits superior resistance to network perturbations, thereby affirming the effectiveness of the model in improving the robustness of integrated energy systems. Full article
19 pages, 3110 KiB  
Article
Integrated Environmental–Economic Assessment of Small-Scale Natural Gas Sweetening Processes
by Qing Wen, Xin Chen, Xingrui Peng, Yanhua Qiu, Kunyi Wu, Yu Lin, Ping Liang and Di Xu
Processes 2025, 13(8), 2473; https://doi.org/10.3390/pr13082473 - 5 Aug 2025
Abstract
Effective in situ H2S removal is essential for the utilization of small, remote natural gas wells, where centralized treatment is often unfeasible. This study presents an integrated environmental–economic assessment of two such processes, LO-CAT® and triazine-based absorption, using a scenario-based [...] Read more.
Effective in situ H2S removal is essential for the utilization of small, remote natural gas wells, where centralized treatment is often unfeasible. This study presents an integrated environmental–economic assessment of two such processes, LO-CAT® and triazine-based absorption, using a scenario-based framework. Environmental impacts were assessed via the Waste Reduction Algorithm (WAR), considering both Potential Environmental Impact (PEI) generation and output across eight categories, while economic performance was analyzed based on equipment, chemical, energy, environmental treatment, and labor costs. Results show that the triazine-based process offers superior environmental performance due to lower toxic emissions, whereas LO-CAT® demonstrates better economic viability at higher gas flow rates and H2S concentrations. An integrated assessment combining monetized environmental impacts with economic costs reveals that the triazine-based process becomes competitive only if environmental impacts are priced above specific thresholds. This study contributes a practical evaluation framework and scenario-based dataset that support sustainable process selection for decentralized sour gas treatment applications. Full article
(This article belongs to the Section Chemical Processes and Systems)
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29 pages, 3037 KiB  
Review
Methods for GC/MS Analysis of the Most Commonly Seized Drugs of Abuse and Their Metabolites in Biological Samples
by Ivan Kojić, Violeta M. Đurović, Yulia A. Smyatskaya, Nemanja Brkljača, Angi E. Skhvediani, Andrey V. Vasin, Ksenija Stojanović and Saša D. Đurović
Chemosensors 2025, 13(8), 286; https://doi.org/10.3390/chemosensors13080286 - 4 Aug 2025
Viewed by 18
Abstract
Gas chromatography with mass spectrometry (GC-MS) is a common analytical technique used for identifying and quantifying drugs of abuse, as well as their metabolites, extracted from biological samples. Depending on the properties of the analyzed compounds, particularly in the case of metabolites, derivatization [...] Read more.
Gas chromatography with mass spectrometry (GC-MS) is a common analytical technique used for identifying and quantifying drugs of abuse, as well as their metabolites, extracted from biological samples. Depending on the properties of the analyzed compounds, particularly in the case of metabolites, derivatization is often necessary. In this article, we will address the definition, properties, sample preparation, and GC-MS analysis of the most common drugs of abuse in their native (seized) form and their metabolites in biological samples (urine, blood, hair, and tissue). Drugs that will be described are: amphetamines and their derivatives, cannabinoids, cocaine, opioids, lysergide (LSD), benzodiazepines, gamma-hydroxybutyric acid (GHB), phencyclidine (PCP), mescaline, psilocin, and psilocybin. The literature review showed that the analysis of the drugs of abuse requires a simple extraction procedure and analysis with or without derivatization. However, the analysis of the metabolites requires removing the interferences from the matrix (proteins, other compounds, water, and other species that may interfere with the analysis or contaminate the GC-MS). This review article will provide insights into the available procedures for sample preparation and analytical methods, helping authors gain the necessary information and select the desired procedure for analysis. Full article
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20 pages, 2327 KiB  
Article
From Climate Liability to Market Opportunity: Valuing Carbon Sequestration and Storage Services in the Forest-Based Sector
by Attila Borovics, Éva Király, Péter Kottek, Gábor Illés and Endre Schiberna
Forests 2025, 16(8), 1251; https://doi.org/10.3390/f16081251 - 1 Aug 2025
Viewed by 261
Abstract
Ecosystem services—the benefits humans derive from nature—are foundational to environmental sustainability and economic well-being, with carbon sequestration and storage standing out as critical regulating services in the fight against climate change. This study presents a comprehensive financial valuation of the carbon sequestration, storage [...] Read more.
Ecosystem services—the benefits humans derive from nature—are foundational to environmental sustainability and economic well-being, with carbon sequestration and storage standing out as critical regulating services in the fight against climate change. This study presents a comprehensive financial valuation of the carbon sequestration, storage and product substitution ecosystem services provided by the Hungarian forest-based sector. Using a multi-scenario framework, four complementary valuation concepts are assessed: total carbon storage (biomass, soil, and harvested wood products), annual net sequestration, emissions avoided through material and energy substitution, and marketable carbon value under voluntary carbon market (VCM) and EU Carbon Removal Certification Framework (CRCF) mechanisms. Data sources include the National Forestry Database, the Hungarian Greenhouse Gas Inventory, and national estimates on substitution effects and soil carbon stocks. The total carbon stock of Hungarian forests is estimated at 1289 million tons of CO2 eq, corresponding to a theoretical climate liability value of over EUR 64 billion. Annual sequestration is valued at approximately 380 million EUR/year, while avoided emissions contribute an additional 453 million EUR/year in mitigation benefits. A comparative analysis of two mutually exclusive crediting strategies—improved forest management projects (IFMs) avoiding final harvesting versus long-term carbon storage through the use of harvested wood products—reveals that intensified harvesting for durable wood use offers higher revenue potential (up to 90 million EUR/year) than non-harvesting IFM scenarios. These findings highlight the dual role of forests as both carbon sinks and sources of climate-smart materials and call for policy frameworks that integrate substitution benefits and long-term storage opportunities in support of effective climate and bioeconomy strategies. Full article
(This article belongs to the Section Forest Economics, Policy, and Social Science)
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15 pages, 1591 KiB  
Article
Role of Cation Nature in FAU Zeolite in Both Liquid-Phase and Gas-Phase Adsorption
by Baylar Zarbaliyev, Nizami Israfilov, Shabnam Feyziyeva, Gaëtan Lutzweiler, Narmina Guliyeva and Benoît Louis
Catalysts 2025, 15(8), 734; https://doi.org/10.3390/catal15080734 - 1 Aug 2025
Viewed by 247
Abstract
This study focuses on the exchange of mono- and divalent metal cations in FAU-type zeolite and their behavior in gas-phase CO2 adsorption measurements and liquid-phase methylene blue (MB) adsorption in the absence of oxidizing agents under dark conditions. Firstly, zeolites exchanged with [...] Read more.
This study focuses on the exchange of mono- and divalent metal cations in FAU-type zeolite and their behavior in gas-phase CO2 adsorption measurements and liquid-phase methylene blue (MB) adsorption in the absence of oxidizing agents under dark conditions. Firstly, zeolites exchanged with different cations were characterized by several techniques, such as XRD, SEM, XRF, XPS, and N2 adsorption–desorption, to reveal the impact of the cations on the zeolite texture and structure. The adsorption studies revealed a positive effect of cation exchange on the adsorption capacity of the zeolite, particularly for silver-loaded FAU zeolite. In liquid-phase experiments, Ag-Y zeolite also demonstrated the highest MB removal, with a value of 79 mg/g. Kinetic studies highlighted that Ag-Y could reach the MB adsorption equilibrium within 1 h, with its highest rate of adsorption occurring during the first 5 min. In gas-phase adsorption studies, the highest CO2 adsorption capacity was also achieved over Ag-Y, yielding 10.4 µmol/m2 of CO2 captured. Full article
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20 pages, 3578 KiB  
Article
Performance Improvement of Proton Exchange Membrane Fuel Cell by a New Coupling Channel in Bipolar Plate
by Qingsong Song, Shuochen Yang, Hongtao Li, Yunguang Ji, Dajun Cai, Guangyu Wang and Yuan Liufu
Energies 2025, 18(15), 4068; https://doi.org/10.3390/en18154068 - 31 Jul 2025
Viewed by 133
Abstract
The geometric design of flow channels in bipolar plates is one of the critical features of proton exchange membrane fuel cells (PEMFCs), as it determines the power output of the fuel cell and has a significant impact on its performance and durability. The [...] Read more.
The geometric design of flow channels in bipolar plates is one of the critical features of proton exchange membrane fuel cells (PEMFCs), as it determines the power output of the fuel cell and has a significant impact on its performance and durability. The function of the bipolar plate is to guide the transfer of reactant gases to the gas diffusion layer and catalytic layer inside the PEMFC, while removing unreacted gases and gas–liquid byproducts. Therefore, the design of the bipolar plate flow channel is directly related to the water and thermal management of the PEMFC. In order to improve the comprehensive performance of PEMFCs and ensure their safe and stable operation, it is necessary to design the flow channels in bipolar plates rationally and effectively. This study addresses the limitations of existing bipolar plate flow channels by proposing a new coupling of serpentine and radial channels. The distribution of oxygen, water concentrations, and temperature inside the channel is simulated using the multi-physics simulation software COMSOL Multiphysics 6.0. The performance of this novel design is compared with conventional flow channels, with a particular focus on the pressure drop and current density to evaluate changes in the output performance of the PEMFC. The results show that the maximum current density of this novel design is increased by 67.36% and 10.43% compared to straight channel and single serpentine channels, respectively. The main contribution of this research is the innovative design of a new coupling of serpentine and radial channels in bipolar plates, which improves the overall performance of the PEMFC. This study provides theoretical support for the design of bipolar plate flow channels in PEMFCs and holds significant importance for the green development of energy. Full article
(This article belongs to the Special Issue Advanced Energy Storage Technologies)
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16 pages, 3038 KiB  
Article
The Interaction Mechanism Between Modified Selective Catalytic Reduction Catalysts and Volatile Organic Compounds in Flue Gas: A Density Functional Theory Study
by Ke Zhuang, Hanwen Wang, Zhenglong Wu, Yao Dong, Yun Xu, Chunlei Zhang, Xinyue Zhou, Yangwen Wu and Bing Zhang
Catalysts 2025, 15(8), 728; https://doi.org/10.3390/catal15080728 - 31 Jul 2025
Viewed by 233
Abstract
The overall efficiency of combining denitrification and volatile organic compound (VOC) removal through selective catalytic reduction (SCR) technology is currently mainly limited by the VOC removal aspect. However, existing studies have not studied the microscopic mechanism of the interaction between VOCs and catalysts, [...] Read more.
The overall efficiency of combining denitrification and volatile organic compound (VOC) removal through selective catalytic reduction (SCR) technology is currently mainly limited by the VOC removal aspect. However, existing studies have not studied the microscopic mechanism of the interaction between VOCs and catalysts, failing to provide a theoretical basis for catalysts. Therefore, this work explored the interaction mechanisms between SCR catalysts doped with different additives and typical VOCs (acetone and toluene) in flue gas based on density functional theory (DFT) calculations. The results showed that the VNi-TiO2 surface exhibited a high adsorption energy of −0.80 eV for acetone and a high adsorption energy of −1.02 eV for toluene on the VMn-TiO2 surface. Electronic structure analysis revealed the VMn-TiO2 and VNi-TiO2 surfaces exhibited more intense orbital hybridization with acetone and toluene, promoting charge transfer between the two and resulting in stronger interactions. The analysis of temperature on adsorption free energy showed that VMn-TiO2 and VNi-TiO2 still maintained high activity at high temperatures. This work contributes to clarifying the interaction mechanism between SCR and VOCs and enhancing the VOC removal efficiency. Full article
(This article belongs to the Section Computational Catalysis)
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14 pages, 2295 KiB  
Article
Design of Novel Hydraulic Drive Cleaning Equipment for Well Maintenance
by Zhongrui Ji, Qi Feng, Shupei Li, Zhaoxuan Li and Yi Pan
Processes 2025, 13(8), 2424; https://doi.org/10.3390/pr13082424 - 31 Jul 2025
Viewed by 231
Abstract
Deep drilling and horizontal wells, as important means of unconventional oil and gas development, face problems with the high energy consumption but low removal efficiency of traditional well washing equipment, the uneven cleaning of horizontal well intervals, and an insufficient degree of automation. [...] Read more.
Deep drilling and horizontal wells, as important means of unconventional oil and gas development, face problems with the high energy consumption but low removal efficiency of traditional well washing equipment, the uneven cleaning of horizontal well intervals, and an insufficient degree of automation. This paper proposes a novel hydraulic drive well washing device which consists of two main units. The wellbore cleaning unit comprises a hydraulic drive cutting–flushing module, a well cleaning mode-switching module, and a filter storage module. The unit uses hydraulic and mechanical forces to perform combined cleaning to prevent mud and sand from settling. By controlling the flow direction of the well washing fluid, it can directly switch between normal and reverse washing modes in the downhole area, and at the same time, it can control the working state of corresponding modules. The assembly control unit includes the chain lifting module and the arm assembly module, which can lift and move the device through the chain structure, allow for the rapid assembly of equipment through the use of a mechanical arm, and protect the reliability of equipment through the use of a centering structure. The device converts some of the hydraulic power into mechanical force, effectively improving cleaning and plugging removal efficiency, prolonging the downhole continuous working time of equipment, reducing manual operation requirements, and comprehensively improving cleaning efficiency and energy utilization efficiency. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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19 pages, 2595 KiB  
Article
Evolutionary Polynomial Regression Algorithm with Uncertain Variables: Two Case-Studies in the Field of Civil Engineering
by Alessandra Fiore, Sebastiano Marasco and Rita Greco
Appl. Sci. 2025, 15(15), 8432; https://doi.org/10.3390/app15158432 - 29 Jul 2025
Viewed by 210
Abstract
Data-driven approaches and calibration techniques for mathematical models, starting from observed data, are attracting more and more interest in the field of civil engineering. Among them, evolutionary polynomial regression (EPR) is an artificial intelligence (AI) technique that combines genetic algorithms (GAs) and regression [...] Read more.
Data-driven approaches and calibration techniques for mathematical models, starting from observed data, are attracting more and more interest in the field of civil engineering. Among them, evolutionary polynomial regression (EPR) is an artificial intelligence (AI) technique that combines genetic algorithms (GAs) and regression strategies. However, the difficulties and uncertainties inherent in the method have pointed out how the implementation of proper computational methods together with the use of recent and qualified databases of experimental data are essential to carry out reliable formulations. In this framework, this paper explores a new robust EPR approach able to remove potential outliers and leverage points often occurring in biased dataset and simultaneously accounting for the effects of probabilistic uncertainties. Uncertainties are incorporated in the EPR methodology by adopting the direct perturbation method. In particular, it is shown the importance to set the parameters representative of experimental and analytical dispersions on the basis of the characteristics of the database in terms of homogeneity. With this purpose, two different case-studies are analyzed, dealing with the shear capacity of RC beams without stirrups and the compressive strength of cement-based mortar specimens, respectively. Finally, the best capacity equations are selected and discussed. Full article
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21 pages, 6272 KiB  
Article
Numerical Study of Gas Dynamics and Condensate Removal in Energy-Efficient Recirculation Modes in Train Cabins
by Ivan Panfilov, Alexey N. Beskopylny, Besarion Meskhi and Sergei F. Podust
Fluids 2025, 10(8), 197; https://doi.org/10.3390/fluids10080197 - 29 Jul 2025
Viewed by 175
Abstract
Maintaining the required relative humidity values in the vehicle cabin is an important HVAC task, along with considerations related to the temperature, velocity, air pressure and noise. Deviation from the optimal values worsens the psycho-physiological state of the driver and affects the energy [...] Read more.
Maintaining the required relative humidity values in the vehicle cabin is an important HVAC task, along with considerations related to the temperature, velocity, air pressure and noise. Deviation from the optimal values worsens the psycho-physiological state of the driver and affects the energy efficiency of the train. In this study, a model of liquid film formation on and removal from various cabin surfaces was constructed using the fundamental Navier–Stokes hydrodynamic equations. A special transport model based on the liquid vapor diffusion equation was used to simulate the air environment inside the cabin. The evaporation and condensation of surface films were simulated using the Euler film model, which directly considers liquid–gas and gas–liquid transitions. Numerical results were obtained using the RANS equations and a turbulence model by means of the finite volume method in Ansys CFD. Conjugate fields of temperature, velocity and moisture concentration were constructed for various time intervals, and the dependence values for the film thicknesses on various surfaces relative to time were determined. The verification was conducted in comparison with the experimental data, based on the protocol for measuring the microclimate indicators in workplaces, as applied to the train cabin: the average ranges encompassed temperature changes from 11% to 18%, and relative humidity ranges from 16% to 26%. Comparison with the results of other studies, without considering the phase transition and condensation, shows that, for the warm mode, the average air temperature in the cabin with condensation is 12.5% lower than without condensation, which is related to the process of liquid evaporation from the heated walls. The difference in temperature values for the model with and without condensation ranged from −12.5% to +4.9%. We demonstrate that, with an effective mode of removing condensate film from the window surface, including recirculation modes, the energy consumption of the climate control system improves significantly, but this requires a more accurate consideration of thermodynamic parameters and relative humidity. Thus, considering the moisture condensation model reveals that this variable can significantly affect other parameters of the microclimate in cabins: in particular, the temperature. This means that it should be considered in the numerical modeling, along with the basic heat transfer equations. Full article
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18 pages, 1597 KiB  
Article
Influence Mechanism of Coexisting Ions on the Extraction Efficiency of Lithium from Oil and Gas Field Water
by Qiaoli Shan, Guocheng Zhu, Pengjun Fan, Mengyu Liang, Xin Zhang, Jie Liu and Guizhi Wu
Water 2025, 17(15), 2258; https://doi.org/10.3390/w17152258 - 29 Jul 2025
Viewed by 124
Abstract
Oil and gas field water not only contains low concentrations of lithium but also a lot of suspended matter, inorganic salt, and organic matter. Both inorganic ions and organic substances influence the extraction of lithium. To improve the extraction efficiency of low-concentration lithium [...] Read more.
Oil and gas field water not only contains low concentrations of lithium but also a lot of suspended matter, inorganic salt, and organic matter. Both inorganic ions and organic substances influence the extraction of lithium. To improve the extraction efficiency of low-concentration lithium in oil and gas field water, the effects of Na+, K+, Ca2+, Mg2+, Cl, Br, SO42−, NO3, and organic substances on the extraction efficiency of lithium were studied. The results showed that Na+ can promote the extraction of lithium to a certain extent, and lithium ions competed with K+ for extraction; however, the separation coefficient remained more than 13. Ca2+ and Mg2+ have a significant influence on the extraction of lithium and should be removed prior to extraction. Cl, SO42−, and NO3 have little influence on the extraction solution of lithium. Among the organic components, a high concentration of long-chain alkane has a certain effect on the extraction efficiency of lithium, while other substances have little effect. On this basis, the first step for precipitating impurity ions and the second step for solvent extraction of lithium were established. After removing the impurity ions, the extraction efficiency of lithium can reach over 90%. Taking 15L of oil and gas field water as the research object, after extraction, back extraction, concentration, depth impurities removal by extraction, and precipitation drying, the purity of the lithium carbonate product can be achieved at 99.28%. This study can provide technical support for the efficient extraction of low-concentration lithium from oil and gas field water. Full article
(This article belongs to the Special Issue Science and Technology for Water Purification, 2nd Edition)
14 pages, 1577 KiB  
Article
Determination of Acidity of Edible Oils for Renewable Fuels Using Experimental and Digitally Blended Mid-Infrared Spectra
by Collin G. White, Ayuba Fasasi, Chanda Swalley and Barry K. Lavine
J. Exp. Theor. Anal. 2025, 3(3), 20; https://doi.org/10.3390/jeta3030020 - 28 Jul 2025
Viewed by 183
Abstract
Renewable fuels produced from animal- and plant-based edible oils have emerged as an alternative to oil and natural gas. Burgeoning interest in renewables can be attributed to the rapid depletion of fossil fuels caused by the global energy demand and the environmental advantages [...] Read more.
Renewable fuels produced from animal- and plant-based edible oils have emerged as an alternative to oil and natural gas. Burgeoning interest in renewables can be attributed to the rapid depletion of fossil fuels caused by the global energy demand and the environmental advantages of renewables, specifically reduced emissions of greenhouse gases. An important property of the feedstock that is crucial for the conversion of edible oils to renewable fuels is the total acid number (TAN), as even a small increase in TAN for the feedstock can lead to corrosion of the catalyst in the refining process. Currently, the TAN is determined by potentiometric titration, which is time-consuming, expensive, and requires the preparation of reagents. As part of an effort to promote the use of renewable fuels, a partial least squares regression method with orthogonal signal correction to remove spectral information related to the sample background was developed to determine the TAN from the mid-infrared (IR) spectra of the feedstock. Digitally blended mid-IR spectral data were generated to fill in regions of the PLS calibration where there were very few samples. By combining experimental and digitally blended mid-IR spectral data to ensure adequate sample representation in all regions of the spectra–property calibration and better understand the spectra–property relationship through the identification of sample outliers in the original data that can be difficult to detect because of swamping, a PLS regression model for TAN (R2 = 0.992, cross-validated root mean square error = 0.468, and bias = 0.0036) has been developed from 118 experimental and digitally blended mid-IR spectra of commercial feedstock. Thus, feedstock whose TAN value is too high for refining can be flagged using the proposed mid-IR method, which is faster and easier to use than the current titrimetric method. Full article
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21 pages, 3300 KiB  
Article
Catalytic Ozonation of Nitrite in Denitrification Wastewater Based on Mn/ZSM-5 Zeolites: Catalytic Performance and Mechanism
by Yiwei Zhang, Yulin Sun, Yanqun Zhu, Wubin Weng, Yong He and Zhihua Wang
Processes 2025, 13(8), 2387; https://doi.org/10.3390/pr13082387 - 27 Jul 2025
Viewed by 358
Abstract
In wet flue gas desulfurization and denitrification processes, nitrite accumulation inhibits denitrification efficiency and induces secondary pollution due to its acidic disproportionation. This study developed a Mn-modified ZSM-5 zeolite catalyst, achieving efficient resource conversion of nitrite in nitrogen-containing wastewater through an O3 [...] Read more.
In wet flue gas desulfurization and denitrification processes, nitrite accumulation inhibits denitrification efficiency and induces secondary pollution due to its acidic disproportionation. This study developed a Mn-modified ZSM-5 zeolite catalyst, achieving efficient resource conversion of nitrite in nitrogen-containing wastewater through an O3 + Mn/ZSM-5 catalytic system. Mn/ZSM-5 catalysts with varying SiO2/Al2O3 ratios (prepared by wet impregnation) were characterized by BET, XRD, and XPS. Experimental results demonstrated that Mn/ZSM-5 (SiO2/Al2O3 = 400) exhibited a larger specific surface area, enhanced adsorption capacity, abundant surface Mn3+/Mn4+ species, hydroxyl oxygen species, and chemisorbed oxygen, leading to superior oxidation capability and catalytic activity. Under the optimized conditions of reaction temperature = 40 °C, initial pH = 4, Mn/ZSM-5 dosage = 1 g/L, and O3 concentration = 100 ppm, the NO2 oxidation efficiency reached 94.33%. Repeated tests confirmed that the Mn/ZSM-5 catalyst exhibited excellent stability and wide operational adaptability. The synergistic effect between Mn species and the zeolite support significantly improved ozone utilization efficiency. The O3 + Mn/ZSM-5 system required less ozone while maintaining high oxidation efficiency, demonstrating better cost-effectiveness. Mechanism studies revealed that the conversion pathway of NO2 followed a dual-path catalytic mechanism combining direct ozonation and free radical chain reactions. Practical spray tests confirmed that coupling the Mn/ZSM-5 system with ozone oxidation flue gas denitrification achieved over 95% removal of liquid-phase NO2 byproducts without compromising the synergistic removal efficiency of NOx/SO2. This study provided an efficient catalytic solution for industrial wastewater treatment and the resource utilization of flue gas denitrification byproducts. Full article
(This article belongs to the Special Issue Processes in 2025)
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17 pages, 8482 KiB  
Article
The Optimization of Culture Conditions for the Cellulase Production of a Thermostable Cellulose-Degrading Bacterial Strain and Its Application in Environmental Sewage Treatment
by Jiong Shen, Konglu Zhang, Yue Ren and Juan Zhang
Water 2025, 17(15), 2225; https://doi.org/10.3390/w17152225 - 25 Jul 2025
Viewed by 273
Abstract
A novel cellulose-degrading bacterial strain, D3-1, capable of degrading cellulose under medium- to high-temperature conditions, was isolated from soil samples and identified as Staphylococcus caprae through 16SrRNA gene sequencing. The strain’s cellulase production was optimized by controlling different factors, such as pH, temperature, [...] Read more.
A novel cellulose-degrading bacterial strain, D3-1, capable of degrading cellulose under medium- to high-temperature conditions, was isolated from soil samples and identified as Staphylococcus caprae through 16SrRNA gene sequencing. The strain’s cellulase production was optimized by controlling different factors, such as pH, temperature, incubation period, substrate concentration, nitrogen and carbon sources, and response surface methods. The results indicated that the optimal conditions for maximum cellulase activity were an incubation time of 91.7 h, a temperature of 41.8 °C, and a pH of 4.9, which resulted in a maximum cellulase activity of 16.67 U/mL, representing a 165% increase compared to pre-optimization levels. The above experiment showed that, when maize straw flour was utilized as a natural carbon source, strain D3-1 exhibited relatively high cellulase production. Furthermore, gas chromatography–mass spectrometry (GC-MS) analysis of products in the degradation liquid revealed the presence of primary sugars. The results indicated that, in the denitrification of simulated sewage, supplying maize straw flour degradation liquid (MSFDL) as the carbon source resulted in a carbon/nitrogen (C/N) ratio of 6:1 after a 24 h reaction with the denitrifying strain WH-01. The total nitrogen (TN) reduction was approximately 70 mg/L, which is equivalent to the removal efficiency observed in the glucose-fed denitrification process. Meanwhile, during a 4 h denitrification reaction in urban sewage without any denitrifying bacteria, but with MSFDL supplied as the carbon source, the TN removal efficiency reached 11 mg/L, which is approximately 70% of the efficiency of the glucose-fed denitrification process. Furthermore, experimental results revealed that strain D3-1 exhibits some capacity for nitrogen removal; when the cellulose-degrading strain D3-1 is combined with the denitrifying strain WH-01, the resulting TN removal rate surpasses that of a single denitrifying bacterium. In conclusion, as a carbon source in municipal sewage treatment, the degraded maize straw flour produced by strain D3-1 holds potential as a substitute for the glucose carbon source, and strain D3-1 has a synergistic effect with the denitrifying strain WH-01 on TN elimination. Thus, this research offers new insights and directions for advancement in environmental sewage treatment. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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