Search Results (3,591)

Supercritical carbon dioxide (SC-CO₂) power cycles offer a promising solution for offshore platforms’ gas turbine waste heat recovery due to their compact design and high thermal efficiency. This study proposes a novel parallel-preheating recuperated Brayton cycle (PBC) using SC-CO₂ for waste heat recovery on offshore gas turbines. An integrated energy, exergy, and economic (3E) model was developed and showed good predictive accuracy (deviations < 3%). The comparative analysis indicates that the PBC significantly outperforms the simple recuperated Brayton cycle (SBC). Under 100% load conditions, the PBC achieves a net power output of 4.55 MW, while the SBC reaches 3.28 MW, representing a power output increase of approximately 27.9%. In terms of thermal efficiency, the PBC reaches 36.7%, compared to 21.5% for the SBC, marking an improvement of about 41.4%. Additionally, the electricity generation cost of the PBC is 0.391 CNY/kWh, whereas that of the SBC is 0.43 CNY/kWh, corresponding to a cost reduction of approximately 21.23%. Even at 30% gas turbine load, the PBC maintains high thermoelectric and exergy efficiencies of 30.54% and 35.43%, respectively, despite a 50.8% reduction in net power from full load. The results demonstrate that the integrated preheater effectively recovers residual flue gas heat, enhancing overall performance. To meet the spatial constraints of offshore platforms, we maintained a pinch-point temperature difference of approximately 20 K in both the preheater and heater by adjusting the flow split ratio. This approach ensures a compact system layout while balancing cycle thermal efficiency with economic viability. This study offers valuable insights into the PBC’s variable-load performance and provides theoretical guidance for its practical optimization in engineering applications. Full article

Background: Post-COVID-19 syndrome (PCS) is defined as the persistence or development of new symptoms 3 months after the initial infection with the SARS-CoV-2 virus, these clinical aspects being most often associated with functional respiratory changes, as well as imagistic modifications. This study aimed to evaluate longitudinal changes in pulmonary function among patients with PCS, in relation to the severity of the acute COVID-19 episode and the time elapsed since infection. Methods: A retrospective, observational study was conducted at the Clinical Hospital of Pulmonary Diseases Iași, Romania, between January 2021 and December 2022, including 97 adult patients with confirmed PCS. Demographic, clinical, and functional data were collected from medical records. Pulmonary function tests (PFTs) were performed according to ATS/ERS standards, assessing Forced Vital Capacity (FVC), Forced Expiratory Volume in the First Second (FEV₁), FEV₁/FVC ratio (Tiffeneau Index), Maximal Expiratory Flow at 50% and 25% of FVC (MEF50, MEF25), Diffusing Capacity of the Lung for Carbon Monoxide (adjusted for haemoglobin) (DLCO), Carbon Monoxide Transfer Coefficient (KCO), Alveolar Volume (AV), Total Lung Capacity (TLC) and Residual Volume (RV). Patients were grouped by time elapsed since infection (1–3, 4–7, 9–12, and up to 22 months). Statistical analyses included the Mann–Whitney U test, Spearman’s correlation, ROC curve analysis, and Principal Component Analysis (PCA). Results: A progressive improvement in FVC was observed up to 9–18 months post-infection (p < 0.05), while FEV₁ remained stable, suggesting a predominantly restrictive ventilatory pattern. Patients with moderate acute COVID-19 presented significantly lower FVC%, FEV₁%, DLCO%, and KCO% values compared with those with mild disease (p < 0.05). Diffusion abnormalities (DLCO and KCO) persisted beyond 12 months, indicating lasting alveolar-capillary impairment. ROC analysis identified TLC (AUC = 0.857), AV (AUC = 0.855), and KCO (AUC = 0.805) as the most discriminative parameters for residual dysfunction. PCA revealed three major functional domains—airflow limitation, diffusion capacity, and lung volume—explaining up to 70% of total variance. Conclusions: We are facing the emergence of a new phenomenon, namely a secondary post-COVID-19 pandemic of patients confronting with persistent post-COVID-19 symptoms who present with functional respiratory changes and who require careful monitoring in dynamics, personalized treatments and a multidisciplinary approach. Full article

Biochar, a carbon-rich material produced through the pyrolysis of wood residues and agricultural byproducts, has carbon storage capacity and potential as a low-carbon construction material. This study predicts the compressive strength of cementitious composites in which cement is partially replaced with biochar using machine learning models. A total of 716 data samples were analyzed, including 480 experimental measurements and 236 literature-derived values. Input variables included the water-to-cement ratio (W/C), biochar content, cement, sand, aggregate, silica fume, blast furnace slag, superplasticizer, and curing conditions. Predictive performance was evaluated using Multiple Linear Regression (MLR), Elastic Net Regression (ENR), Support Vector Regression (SVR), and Gradient Boosting Machine (GBM), with GBM showing the highest accuracy. Further optimization was conducted using XGBoost, Light Gradient-Boosting Machine (LightGBM), CatBoost, and NGBoost with GridSearchCV and Optuna. LightGBM achieved the best predictive performance (mean absolute error (MAE) = 3.3258, root mean squared error (RMSE) = 4.6673, mean absolute percentage error (MAPE) = 11.19%, and R² = 0.8271). SHAP analysis identified the W/C and cement content as dominant predictors, with fresh water curing and blast furnace slag also exerting strong influence. These results support the potential of biochar as a partial cement replacement in low-carbon construction material. Full article

The utilization of sustainable feedstocks offers significant opportunities for innovation in sustainable and efficient processing technologies, targeting a vacuum residue upgrade industry projected to be valued at around USD 26 billion in 2024. This review examines advances in catalytic strategies for upgrading waste-derived products (plastics, tires) and biomass, in addition to heavy oil feedstocks. Particular emphasis is placed on hydrogen addition pathways, specifically, residue hydroconversion facilitated by dispersed nanocatalysts and waste co-processing methodologies. Beyond nanoscale catalyst design and reaction performance, this work also addresses refinery-level sustainability impacts. The advanced catalytic conversion of heavy oil residue demonstrates superior conversion efficiency, significant coke suppression, and improved carbon utilization, while life cycle and illustrative techno-economic comparisons indicate greenhouse gas reductions and a net economic gain of approximately USD 2–3 per barrel relative to conventional refining under scenarios assuming decarbonized hydrogen production. Co-processing of plastics, tires, and biomass with heavy oil feedstocks is highlighted as a practical and effective approach. Together, these findings outline a rational catalytic pathway toward optimized refining systems. Within the framework of the circular carbon economy, these catalytic processes enable enhanced feedstock utilization, integration of low-carbon hydrogen, and coupling with carbon-capture technologies. Full article

Water quality assessment is crucial for the sustainable use and management of groundwater resources. This study was carried out in the irrigated plains of Vehari District, Punjab, Pakistan, to evaluate groundwater suitability for a managed aquifer recharge (MAR) project. Twenty groundwater samples were collected in June 2021 from an area of 1522 km² and analysed for major physicochemical parameters including electrical conductivity (EC), total dissolved solids (TDS), pH, turbidity, calcium (Ca), magnesium (Mg), chloride (Cl), alkalinity (Alk), bicarbonate (HCO₃⁻), hardness, potassium (K), sulphate (SO₄²⁻), sodium (Na), and nitrate (NO₃⁻). Water quality was assessed using WHO and PID standards, alongside derived hydrochemical indices such as sodium percentage (%Na), Kelly’s ratio (KR), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), and the water quality index (WQI). The dataset was interpreted using geo-statistical, geospatial, multivariate, and correlation analyses. Cations and anion dominance followed the order Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and HCO₃⁻ > SO₄²⁻ > Cl⁻ > NO₃⁻. According to the WQI analysis, 35% of the water samples are classified as “poor,” half (50%) as “very poor,” and the remaining 15% as “unsuitable” for drinking purposes. However, irrigation suitability indices confirmed that groundwater is generally acceptable for agricultural use, though unfit for drinking. The outcomes of this study provide essential insights for groundwater management in the region, where the Punjab Irrigation Department (PID) has initiated a MAR project. Considering that the irrigation sector is the major groundwater consumer in the area, the compatibility of groundwater and surface water quality supports the implementation of MAR to enhance agricultural sustainability. Full article

Ammonia (NH₃) is a zero-carbon fuel and an attractive hydrogen (H₂) carrier for gas turbine power generation due to its high energy density, ease of storage, and transportation. This study numerically investigates NH₃/air combustion using a hybrid Well-Stirred Reactor (WSR) and Plug Flow Reactor (PFR) model in Cantera at pressures of 1–20 atm, temperatures of 1850–2150 K, and equivalence ratios (ϕ) of 0.7–1.2. The effects of pressure, equivalence ratio, and temperature on NH₃ conversion and NO formation are examined. Results show that NH₃ exhibits a non-monotonic conversion curve with pressure after the WSR, reaching a minimum near 5 atm, whereas NO formation decreases monotonically from 1 to 20 atm. Equivalence ratio sweeps show that NO decreases steeply as ϕ increases from 0.7 to ~1.1 as nitrogen is redirected toward N₂ and oxidizer availability declines; residual NH₃ increases rapidly for ϕ > 1.0, especially at high pressure. Increasing temperature accelerates NH₃ oxidation and raises NO formation, most strongly at low pressure where thermal and NH/OH pathways are least inhibited. These results indicate that co-tuning pressure and equivalence ratio near rich operation enables low-NO_x ammonia combustion suitable for advanced gas turbine applications. Full article

Spent coffee grounds (SCG) are an abundant, carbon-rich residue that can be valorized through thermochemical conversion into biochar. Conventional CO₂ activation is typically performed in a two-step process, which is time- and energy-consuming. This study aims to evaluate whether a one-step CO₂-assisted pyrolysis can produce biochar with comparable or enhanced structural and textural properties while simplifying the process. We compare a two-step pyrolysis process followed by CO₂ activation with a one-step CO₂-assisted route for producing biochar from SCG. CO₂ treatment markedly increases surface area (from 9.8 m²∙g⁻¹ to 550.6–671.0 m²∙g⁻¹) and pore volume. FTIR and Boehm titration indicate depletion of oxygenated surface groups, while N₂ adsorption–desorption analyses and SEM reveal a more uniform micro/mesoporous texture for the one-step sample. Although fixed carbon decreases due to gasification, the one-step route delivers superior textural properties in a single thermal stage, reducing energy demand. These results highlight one-step CO₂-assisted pyrolysis as an efficient, scalable option for producing high-porosity biochar from coffee waste. Full article

The valorization of wet blue leather waste represents an important strategy for both environmental management and the development of sustainable adsorbent materials. In this study, activated carbons were produced from wet blue leather residue and characterized in terms of surface area and chromium content. Pyrolysis at 700 °C yielded activated carbons with surface areas exceeding 500 m²·g⁻¹, directly associated with the chromium content of the material. The results indicate that chromium embedded in the leather matrix acts as an effective chemical activator, enhancing the porous structure. Adsorption experiments demonstrated that both pH and methylene blue concentration positively influenced adsorption capacity, whereas temperature exhibited a negative effect. The maximum adsorption capacity reached 20.2 mg g⁻¹. These results show the potential of wet blue leather waste-derived activated carbon as a low-cost and efficient adsorbent for dye removal from aqueous systems. Full article

This work used activated carbon material obtained by chemical activation of abundantly available agricultural sunflower waste residues to remove metol (4-(methylamino) phenol sulfate, MTL) from aqueous solutions. The adsorbent structure was characterized using SEM-EDS and FT-IR spectroscopy. A modified screen-printed carbon electrode (SPCE) with gold nanoparticles synthesized using the Laser Ablation Synthesis in Solution (LASIS) method was used to detect MTL. The successful LASIS formation of gold nanoparticles was confirmed by the specific dark burgundy–red color. TEM measurements showed uniform pseudo-spherical particles with an average diameter of 7.9 ± 0.2 nm. The modified electrode showed improved electrochemical activity, which was confirmed by comparing it with an unmodified electrode using cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode was subsequently used to optimize the MTL detection conditions. UV–Vis spectroscopy was used to optimize the adsorption conditions, with the optimal values for pH and contact time found to be 8 and 120 min, respectively. The electrochemical detection of MTL was performed using differential pulse voltammetry, and the linear calibration range was established for concentrations ranging from 0.73–49.35 µM. The obtained limits of detection (LOD) and quantification (LOQ) were 0.06 µM and 0.2 µM, respectively. The efficiency of MTL removal was 100% after a contact time of 1 min and remained at 100% after 120 min. Full article

To identify the emission reduction potential and policy synergies of Tokyo’s road passenger and urban road freight transport under the “carbon neutrality target,” this paper constructs an assessment framework for megacities. First, based on macroeconomic socioeconomic variables (population, GDP, road length, and employment), regression equations are used to predict traffic turnover for different modes of transport from 2021 to 2050. Then, the prediction results are imported into the LEAP (Long-range Energy Alternatives Planning) model. By adjusting three policy levers—vehicle technology substitution (ZEV: EV/FCEV), energy intensity improvement, and upstream electricity and hydrogen supply decarbonization—a “single-factor vs. multi-factor (policy synergy)” scenario matrix is designed for comparison. The results show that the emission reduction potential of a single measure is limited; upstream decarbonization yields the greatest independent emission reduction effect, while the emission reduction effect of deploying zero-emission vehicles and improving energy efficiency alone is small. In the most ambitious composite scenario, emissions will decrease by approximately 83% by 2050 compared to the baseline scenario, with cumulative emissions decreasing by over 35%. Emissions from rail and taxis will approach zero, while buses and freight will remain the primary residual sources. This indicates that achieving net zero emissions in the transportation sector requires not only accelerated ZEV penetration but also the simultaneous decarbonization of electricity and hydrogen, as well as policy timing design oriented towards fleet replacement cycles. The integrated modeling and scenario analysis presented in this paper provide quantifiable evidence for the formulation of a medium- to long-term emissions reduction roadmap and the optimization of policy mix in Tokyo’s transportation sector. Full article

This manuscript reports the preparation, surface characterization, and modeling of chars and activated carbons obtained from avocado biomass for hydrogen storage. Activated carbons were prepared from avocado biomass via the following stages: (a) pyrolysis of avocado biomass, (b) impregnation of the avocado-based char using an aqueous lithium solution, and (c) thermal activation of lithium-loaded avocado char. The synthesis conditions of char and activated carbon samples were tailored to maximize their hydrogen adsorption properties at 77 K, where the impact of both pyrolysis and activation conditions was assessed. The hydrogen storage mechanism was discussed based on computational chemistry calculations and multilayer adsorption simulation. The modelling focuses on the analysis of the saturation of activated carbon active sites via the adsorption of multiple hydrogen molecules. The results showed that the activated carbon samples displayed adsorption capacities higher than their char counterparts by 71–91% because of the proposed activation protocol. The best activated carbon obtained from avocado residues showed a maximum hydrogen adsorption capacity of 142 cm³/g, and its storage performance can compete with other carbonaceous adsorbents reported in the literature. The hydrogen adsorption mechanism implied the formation of 2–4 layers on activated carbon surface, where physical interactions via oxygenated functionalities played a relevant role in the binding of hydrogen dimers and trimers. The results of this study contribute to the application of low-cost activated carbons from residual biomass as a storage medium in the green hydrogen supply chain. Full article

Given the potential hazards of enrofloxacin (ENR) residues to human health, establishing an accurate, rapid, and stable detection method is of importance. To enable the direct detection of ENR, an electrochemical sensor was constructed in this study. N- and S-doped carbon quantum dots (CQDs) with peroxidase-like activity were prepared using DL-malic acid, L-alanine, and L-cysteine as precursors and compounded with a tetrakis (4-carboxyphenyl) porphyrin (TCPP) and Fe(NO₃)₃·9H₂O to make novel N/S CQDs@Fe-TCPP composite carbon-based nanozymes to construct an electrochemical sensor, and the electrochemical behavior was investigated. Under optimal experimental conditions, the sensor exhibited a linear current response to ENR concentrations in the range of 1–1300 nM (I (μA) = 0.0106c (nM) + 2.9861, R² = 0.9962), with a calculated detection limit of 0.872 nM (S/N = 3). The recovery rate of this sensor in actual milk samples ranged from 99.02% to 100.9%. The reproducibility experiments demonstrated the high precision of the method, with a relative standard deviation (RSD) of 1.27%. Stability testing revealed a peak current retention rate of 93.51% on day 21, indicating excellent system stability. These findings indicate that the sensor shows great capability for ENR detection in food products. Full article

Tillage practices regulate soil health by influencing soil’s physico-chemical qualities and its capacity to sequester organic carbon. Maintaining soil health contributes to ecosystem stability and fluidity in the soil–plant–atmosphere relationship. This study aimed to evaluate soil porosity (SP), aeration limit (SAL), soil capillary capacity (SCC), soil total capacity (STC), soil temperature (Ts), air temperature (Ta), nutrient availability, soil organic carbon (SOC), and soil organic matter (SOM) under three different tillage systems: no-tillage (NT), minimum tillage (MT), and conventional tillage (CT), based on a short-term field experiment. This research was conducted on Cambic Chernozem soil using a randomized complete block design with three replications. The results revealed a significant effect of tillage systems on all evaluated properties. SP reached a higher value under MT (60.01%), NT (56.74%) and CT (53.58%), respectively. This observation is similar with regard to SAL, SCC, and STC. It might be due to the reduced soil disturbance characteristics of conservation systems, thereby maintaining the soil’s natural state. There is a positive regression between these two properties across all three systems, with the highest R² = 0.8308 observed under MT. The highest carbon stocks were recorded in NT (2.82%) and MT (2.91%) compared to 2.01% in CT at surface depths of 0–5 and 5–10 cm. This can be explained by the accumulation of organic residues and a reduction in their oxidation. Nutrient availability (TN, P, and K) increased at depths of 0–5 cm and 5–10 cm, with the highest values in conservation systems. Furthermore, the results demonstrate a significant relationship and positive synergy between soil depth, tillage practices, and key physical and chemical soil properties, especially carbon stock, across the two cropping seasons. Full article

Graphene oxide (GO) is a carbon-based nanomaterial explored for agricultural and forestry uses, but plant responses are strongly subject to both the dose and the route of exposure. We summarized recent studies with defined graphene oxide (GO) exposures by seed priming, foliar delivery, and root or soil exposure, while comparing annual crops with woody forest plants. Mechanistic progress points to a shared physicochemical basis: surface oxygen groups and sheet geometry reshape water and ion microenvironments at the soil–seed and soil–rhizosphere interfaces, and many reported shifts in antioxidant enzymes and hormone pathways likely represent downstream stress responses. In crops, low-to-moderate doses most consistently improve germination, root architecture, and tolerance to salinity or drought stress, whereas high doses or prolonged root exposure can cause root surface coating, oxidative injury, and photosynthetic inhibition. In forest plants, evidence remains limited and often relies on seedlings or tissue culture. For forest plants with long life cycles, processes such as soil persistence, aging, and multi-seasonal carry-over become key factors, especially in nurseries and restoration substrates. The available data indicate predominant root retention with generally limited root-to-shoot translocation, so residues in edible and medicinal organs remain insufficiently quantified under realistic-use patterns. This review provides a scenario-based framework for crop- and forestry-specific safe-dose windows and proposes standardized endpoints for long-term fate and ecological risk assessment. Full article

The escalating release of synthetic dyes from textile and allied industries has become a pressing global environmental issue due to their toxicity, persistence, and resistance to biodegradation. Among the various treatment strategies, adsorption has emerged as one of the most efficient, economical, and sustainable techniques for dye removal from aqueous environments. This review highlights recent advances in bio-derived adsorbents—particularly raw biomass powders, biochars, and activated carbons—developed from renewable waste sources such as agricultural residues, fruit peels, shells, and plant fibers. It systematically discusses adsorption mechanisms, the influence of process parameters, kinetic and thermodynamic models, and regeneration performance. Furthermore, the review emphasizes the superior adsorption efficiency and cost-effectiveness of biomass-derived carbons compared to conventional adsorbents. The integration of surface modification, magnetization, and nanocomposite formation has further enhanced dye uptake and reusability. Overall, this study underscores the potential of biomass-derived materials as sustainable alternatives for wastewater treatment and environmental remediation. Full article