Search Results (16,430)

The synthesis of carbon dots (CDs) from coal represents a promising strategy for advancing both the efficient, low-carbon utilization of coal resources and the cost-effective production of CDs. To enable the controlled, high-quality conversion of CDs from coal, a comprehensive understanding of the relationship between the coal chemical structure and the properties of CDs is crucial. This study prepared CDs from nine kinds of coal using a chemical oxidation method, and the correlations between properties of coal-based carbon dots and the original materials were revealed. The results show that the luminescence sites of coal-derived CDs are mostly distributed around 435 nm or 500 nm, where the former one relates to the confined sp² domains and the latter one is associated with the defect structure. Coal with a volatile content of about 20–30% in the nine samples was found to produce higher CD yields, with a maximum mass yield of 19.96%, accompanied by stronger fluorescence intensity. During chemical oxidation processes, the unsaturated double bonds (C=C, C=O) and aliphatic chains firstly break, and then aromatic clusters are formed by dehydrocyclization between carbon crystallites, followed by the introduction of a C–O group. The growth of the C–O group in the CDs contributes to a stronger fluorescence property. Furthermore, strong correlations were found between the carbon skeleton structure of raw coal and photoluminescence characteristics of corresponding CDs, as reflected by Raman parameters A_D1/A_G, I_D1/I_G, and FWHM_D. The findings offer significant insights into the precise modulation and control of coal-based carbon dot structures. Full article

Against the escalating challenges of global climate change and intensifying resource-environment constraints, exploring the green effects of industrial spatial organization has become crucial. Utilizing panel data from the Yangtze River Delta cities spanning 2011–2023, this study empirically examines the nonlinear impact of manufacturing-producer services co-agglomeration on urban green efficiency. The results reveal a significant U-shaped relationship: co-agglomeration initially suppresses efficiency due to coordination costs and congestion effects, but after crossing a specific threshold, the resulting scale economies and knowledge spillovers dominate and begin to promote green enhancement. Mechanism tests indicate that industrial upgrading serves as a direct mediating channel, while the mediating effect of green technological innovation exhibits a time lag. Further heterogeneity analysis shows that this U-shaped pattern is particularly pronounced in cities with low agglomeration levels, those not designated as low-carbon pilots, and non-resource-based cities. This study uncovers the nonlinear dynamics and key boundary conditions of the green effects arising from industrial co-agglomeration, providing an empirical basis for implementing differentiated regional spatial coordination policies. Full article

Recycling industrial CO₂ into agricultural systems offers a dual-purpose strategy for achieving carbon neutrality and enhancing sustainable crop production. Although elevated CO₂ is known to influence plant growth, the directed delivery of industrially sourced CO₂ via drip irrigation to modulate rhizosphere processes in arid soils remains underexplored. We conducted a two-year field experiment in a Xinjiang cotton field to evaluate the effects of five concentrations of industrial CO₂ solution (0.00–0.16 kg·m⁻³) on soil properties, nutrient dynamics, and crop performance. The optimal CO₂ treatment (0.08 kg·m⁻³) significantly reduced soil pH by up to 0.3 units and electrical conductivity by up to 27.9%, while enhancing the availability of ammonium-N (51.1%), available P (8.1%), and available K (32.65%). These improved soil conditions subsequently enhanced plant N, P, and K accumulation (56.2%, 41.9%, and 53.2%, respectively), total biomass (31.8%), and seed cotton yield (5.76–6.06%). Our findings demonstrate that CO₂-enriched irrigation enhances the rhizosphere microenvironment and nutrient availability, providing a novel pathway for carbon recycling and high-efficiency cotton production in arid regions. Full article

Recycling water offers a powerful way to lower the environmental water impact of mining activities. Pressure-retarded osmosis (PRO) represents a promising pathway for simultaneous water reuse and clean energy generation from salinity gradients. In this study, the performance of a thin-film nanocomposite (TFN) membrane containing functionalized multi-walled carbon nanotubes (fMWCNTs) within a polyacrylonitrile (PAN) support layer, followed by polydopamine (PDA) surface modification, was investigated under a PRO operation using pretreated gold mining wastewater as the feed solution. Unlike most previous studies that rely on synthetic feeds, this work evaluates the membrane performance under a PRO operation using a real mining wastewater stream. The membrane with fMWCNTs and PDA exhibited a maximum power density of 25.22 W/m² at 12 bar, representing performance improvements of 23% and 68% compared with the pristine thin-film composite (TFC) and commercial cellulose triacetate (CTA) membranes, respectively. A high water flux of 75.6 L·m⁻²·h⁻¹ was also obtained, attributed to enhanced membrane hydrophilicity and reduced internal concentration polarization. The optimized membrane, containing 0.3 wt% fMWCNTs in the support layer and a PDA coating on the active layer, produced a synergistic enhancement in the PRO performance, resulting in a lower reverse salt flux and an improved flux–selectivity trade-off. Furthermore, the ultrafiltration (UF) and nanofiltration (NF) pretreatment effectively reduced the hardness and ionic content, enabling a stable PRO operation with real mining wastewater over a longer period of time. Overall, this study demonstrates the feasibility of achieving both reusable water and enhanced osmotic power generation using modified TFN membranes under realistic mining wastewater conditions. Full article

Smallholder farmers in semi-arid regions worldwide face persistent water scarcity, declining soil fertility, and increasing climate variability, which constrain food production. This study investigated soil and water management practices and their effects on soil health, crop productivity, and adoption among smallholder vegetable farmers in a semi-arid area in Kenya. A mixed-methods approach was employed, combining survey data from 397 farmers with a randomized field experiment. Results showed that hand watering (88.7%) and manure application (95.5%) were prevalent, while only 5.7% of farmers used drip irrigation. Compost and mulch treatments significantly improved soil organic carbon (p = 0.03), available water capacity (p = 0.01), and gravimetric moisture content (p = 0.02), with soil moisture conservation practices strongly correlated with higher yields in leafy green vegetables (R = 0.62). Despite these benefits, adoption was hindered by high water costs (42.6%) and unreliable sources (25.7%). Encouragingly, 96.2% of respondents expressed willingness to pay for improved water systems if affordable and dependable. The findings stress the need for integrated water–soil strategies supported by inclusive policy, infrastructure investment, and gender-responsive training to enhance resilience and productivity in smallholder farming under water-scarce conditions across sub-Saharan Africa and other regions globally, contributing to global sustainability targets such as SDG 6, 12 and 15. Full article

Today, PHB and its copolymers—potential plastic substitutes—are produced by fermenting sugar, which is not scalable to the volumes of plastic consumption. PHB from CH₄ can offer a sustainable process route, with CH₄ potentially produced from a variety of waste biomass streams through anaerobic digestion, gasification, and methanation. The high molar mass (M_w) of PHB is a key determinant of its mechanical properties, and strain, culture conditions and downstream processing influence it. In this work, the strain Methylocystis sp. GB 25 (DSMZ 7674) was grown on natural gas as the sole carbon and energy source and air (1:1) in a loop reactor with 350 L active fermentation volume, at 35 °C and ambient pressure. After two days of continuous growth, the bacteria were limited in P and N for 1, 2, and 2.5 days to determine the optimal conditions for PHB accumulation and the highest Mw as the target. The biomass was then centrifuged and spray-dried. For downstream processing, chloroform solvent extraction and selected enzymatic treatment were deployed, yielding ~40% PHB from the biomass. The PHB obtained by solvent extraction exhibited high average weight molar masses of M_w ~1.1–1.5 × 10⁶ g mol⁻¹. The highest M_w was obtained after one day of limitation, whereas enzyme treatment resulted in partially degraded PHB. Cold chloroform maceration, interesting due to energy savings, did not achieve sufficient extraction efficiency because it was unable to extract high-molar-mass PHB fractions. The extracted PHB has a high molar mass, more than double that of standard commercial PHB, and was characterized by DSC, which showed a high degree of crystallinity of up to 70% with a melting temperature of close to 180 °C. Mechanical tensile properties measurements, as well as dynamic mechanical thermal analysis (DMTA), were performed. Degradation of the PHB by enzymes was also determined. Methanotrophic PHB is a promising bioplastics material. The high M_w can limit and delay polymer degradation in practical processing steps, making the material more versatile and robust. Full article

The competitive adsorption of two model herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA), onto Activated Carbons (ACs) derived from pomegranate peels through chemical activation with phosphoric acid (H₃PO₄) was investigated in fixed-bed column mode. The prepared activated carbon (AC-PA) exhibited a high apparent surface area (up to 1409 m²/g) and a predominantly microporous structure. Morphological and chemical analyses (micrographic observation, X-ray difraction, N₂ adsorption–desorption) confirmed the presence of well-developed pore networks and surface oxygenated functionalities. Column adsorption experiments were performed under varying flow rates (0.25–3 mL/min) for both single and binary solutions. The breakthrough data were modeled using the Thomas and Yoon–Nelson equations, achieving high determination coefficients (R² = 0.91–0.99). Lower flow rates favored higher adsorption capacities, reaching 193.61 mg/g for 2,4-D at 0.25 mL/min. Under similar conditions (flow rate of 1.5 mL min⁻¹), the AC provided a better adsorption for 2,4-D than for MCPA in single systems, which was attributed to stronger affinity based on its greater hydrophobicity and prominence to dispersive interactions. In binary systems, competitive effects shifted the results and a noticeable roll-up phenomenon was observed for 2,4-D, attributed to its displacement by MCPA along the bed; this made the adsorbent more effective for MCPA in binary mixtures than in single ones. These findings highlight the potential of pomegranate-based activated carbon as a cost-effective and sustainable adsorbent for herbicide removal in continuous water treatment systems. Full article

In today’s increasingly serious environmental problems, a growing number of enterprises are upgrading remanufacturing as an important corporate strategy. This paper compares two third-party remanufacturing models: the entrusting and Authorizing Models, and introduces two different levels of consumer low-carbon preferences: medium and high. By establishing game equations, we find the equilibrium solution of each model. The results reveal that in the basic model, OEM tends to choose the Authorizing Model when consumers have a pronounced quality bias against remanufactured products. Contrary to intuition, TRM always prefers the Entrusting Model. In scenarios where consumers possess medium low-carbon preferences, OEM tends to choose the Authorizing Model when consumers have a high bias against the quality of the remanufactured products or a low bias against the carbon emissions of the new products. Conversely, OEM tends to choose the entrusting remanufacturing model under the opposite conditions. In scenarios where consumers express high low-carbon preferences, the situation becomes the complete opposite. When consumers exhibit a low bias against remanufactured products’ quality or a high bias against carbon emissions from new products, OEM tends to choose the Authorizing Model. Conversely, OEM prefers the Entrusting Model when consumers’ biases differ. In addition, the consumer surplus and social welfare of the Entrusting Model are higher than those of the Authorizing Model, regardless of the research scenario. Full article

A Life cycle assessment (LCA) is widely used to evaluate the carbon reduction potential of polycrystalline silicon photovoltaic systems. However, in existing LCA methods, most studies use static attenuation models and fixed lifecycle boundary frameworks. Therefore, this study proposes a dynamic LCA framework that considers the attenuation rate changes in photovoltaic systems and the energy gain during the recovery phase. The innovation of this method lies in its ability to more accurately reflect the carbon emissions and energy recovery period (EPBT) of photovoltaic systems under different operating and attenuation scenarios. In addition, this article expands the application scope of the LCA by introducing new boundary conditions, providing a new perspective for the lifecycle assessment of photovoltaic systems. A practical carbon emission calculation model was established using the full lifecycle data within this boundary, and the quantitative relationship between the EPBT and power generation was derived. A three-dimensional dynamic coupling model was developed to integrate these three key parameters and continuously characterize the dynamic behavior of the system throughout its entire lifecycle. This model explicitly addresses the attenuation of photovoltaic modules in three scenarios: low (1%), baseline (3%), and high (5%) attenuation rates. The results show that under low attenuation, the average EPBT is 4.14 years, which extends to 6.5 years under high attenuation and only 2.37 years under low attenuation. Sensitivity analysis confirmed the effectiveness of the model in representing the dynamic evolution of photovoltaic systems, providing a theoretical basis for subsequent environmental performance evaluations. Full article

The green transformation of the shipping industry urgently requires zero-carbon power, and hydrogen-powered ships such as hydrogen fuel cell ships face bottlenecks in in situ hydrogen production and storage and transportation. Methanol steam reforming (MSR) online hydrogen production is suitable for ship scenarios, reducing costs and increasing efficiency while helping achieve zero carbon throughout the entire lifecycle, which has important practical significance. The key technology for MSR technology is the performance of the catalyst. A series of Cu_1−xMn_xAl₂O₄ catalysts were successfully synthesized and applied for hydrogen production in this study. The catalyst structure was characterized using physicochemical techniques including XRD, SEM, and EDS. Hydrogen production performance was evaluated in a fixed-bed reactor under the following conditions: a liquid hourly space velocity (LHSV) of 20 h⁻¹, a water-to-methanol molar ratio of 3:1, and a reaction temperature range of 275 °C–350 °C. The results demonstrate that A-site Mn substitution significantly enhanced the catalytic performance. In addition, XRD analysis revealed that Mn incorporation effectively suppressed the formation of segregated CuO phases. However, excessive substitution (x is 0.9) led to the generation of an MnAl₂O₄ impurity phase. Finally, the Cu_0.7Mn_0.3Al₂O₄ catalyst achieved a methanol conversion of 68.336% at 325 °C, with a hydrogen production rate of 5.611 mmol/min/g_cat, and maintained CO selectivity below 1%. The results demonstrate that the hydrogen production catalyst developed in this study is a promising material for meeting the requirements of online hydrogen sources for ships. Full article

A series of silica-supported, nitrogen-doped carbon-encapsulated cobalt–nickel alloy catalysts (Co_xNi_y@NC/SiO₂) was successfully synthesized and systematically evaluated for the liquid-phase hydrogenation of 1-nitronaphthalene to 1-naphthylamine. Physicochemical characterization confirmed that the incorporation of nickel promotes the formation of Co–Ni alloys and modulates the electronic structure of the catalysts. The catalytic performance was found to be highly sensitive to the Co/Ni ratio, with Co₂Ni₁@NC/SiO₂ exhibiting the most outstanding activity. Under optimized reaction conditions (90 °C, 0.6 MPa H₂, 5.5 h), both the conversion of 1-nitronaphthalene and the selectivity toward 1-naphthylamine reached approximately 99%. The catalyst also demonstrated excellent stability and recyclability, attributed to the protective nitrogen-doped carbon shell and the synergistic interaction between the Co–Ni alloy and M–N_x active sites. This work provides a new strategy for designing efficient and robust non-noble-metal catalysts for hydrogenation reactions. Full article

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

The COVID-19 pandemic led to an unprecedented slowdown in global economic and transportation activities, offering a unique opportunity to assess the relationship between human activity and atmospheric pollution. This study analyzes global variations in major air pollutants and meteorological conditions during the pandemic period using multi-satellite and reanalysis datasets. Nitrogen dioxide (NO₂) data were obtained from the OMI sensor aboard NASA’s Aura satellite, while carbon monoxide (CO) observations were taken from the MOPITT instrument on Terra. Reanalysis products from MERRA-2 were used to assess CO, sulfur dioxide (SO₂), black carbon (BC), organic carbon (OC), and key meteorological variables, including temperature, precipitation, evaporation, wind speed, and direction. Average concentrations of pollutants for April, May, and June 2020, representing the lockdown phase, were compared with the average values of the same months during 2017–2019, representing pre-pandemic conditions. The difference between these multi-year means was used to quantify spatial changes in pollutant levels. Results reveal widespread reductions in NO₂, CO, SO₂, and BC concentrations across major industrial and urban regions worldwide, consistent with decreased anthropogenic activity during lockdowns. Meteorological analysis indicates that the observed reductions were not primarily driven by short-term weather variability, confirming that the declines are largely attributable to reduced emissions. Unlike most previous studies, which examined local or regional air-quality changes, this work provides a consistent global-scale assessment using harmonized multi-sensor datasets and uniform temporal baselines. These findings highlight the strong influence of human activities on atmospheric composition and demonstrate how large-scale behavioral and economic shifts can rapidly alter air quality on a global scale. The results also provide valuable baseline information for understanding emission–climate interactions and for guiding post-pandemic strategies aimed at sustainable air-quality management. Full article

Dual Carbon Goals are driving transformation in China’s power system, where increased renewable energy penetration is accompanied by heightened fluctuations on the generation and load sides. Energy storage and microgrid coordination have emerged as key solutions. However, existing research faces the challenge of balancing microgrid operations, energy storage services, and the alignment of user demand with stakeholder interests. This paper establishes a tripartite collaborative optimization framework to balance multi-stakeholder interests and enhance system efficiency, assuming fixed energy storage capacity. Centering on a principal-agent game between microgrid operators and consumer aggregators, energy storage service providers are integrated into this dynamic. Microgrid operators set 24-h electricity and heat pricing while adhering to tariff constraints, prompting consumer aggregators to adjust energy consumption and storage strategies accordingly. The KKT conditional method is employed to solve the model, deriving optimal user energy consumption strategies at the lower level while solving marginal pricing equilibrium relationships at the upper level, balancing accuracy with information privacy. The creative contribution of this article lies in the first construction of a tripartite collaborative optimization architecture in which energy storage service providers are embedded in a game of ownership and subordination. It proposes a dynamic coupling mechanism between pricing power, energy consumption decision-making, and energy storage configuration under fixed energy storage capacity constraints, achieving a balance of interests among multiple parties. By building a case study using MATLAB (R2022b), we compare operation costs, benefits, and absorption rates across different scenarios to validate the framework’s effectiveness and provide a reference for engineering applications. Full article

This study develops a compact elasticity-based framework for assessing how autonomous truck adoption influences corridor-level performance, freight demand, modal competition, and CO₂ emissions in multimodal freight Intelligent Transportation Systems. The model specifies the constant elastic (log-linear) responses of traffic performance and generalized costs to adoption, enabling the closed-form characterization of system-level rebound and road–rail reallocation effects. The analytical results show that an internal adoption threshold $P^{*}$ emerges, defined by $d\widehat{E}/dP=0$, which separates a beneficial regime (efficiency gains dominate) from an adverse regime (rebound and modal shift dominate). Comparative statics indicate that $P^{*}$ decreases with stronger ITS capability A and increases with rebound intensity R and the road–rail carbon intensity contrast K. Numerical experiments across representative corridor contexts illustrate induced demand effects exceeding 25% under high-rebound conditions and threshold ranges around $P^{*}\approx 0.3$–0.4 for plausible parameters. The results provide interpretable guidance for coordinating autonomous truck deployment with intermodal logistics design and decarbonization strategies. Full article