Search Results (10)

Solid oxide fuel cells (SOFCs) and solid oxide electrolyzer cells (SOECs) represent a promising clean energy solution. In the case of SOFCs, they offer efficiency and minimal to zero CO₂ emissions when used to convert chemical energy into electricity. When SOFC systems are operated in regenerative mode for water electrolysis, the SOFCs become solid oxide electrolyzer cells (SOECs). The problem with these systems is the supply and availability of raw materials for SOFC and SOEC components. This raises significant economic challenges and has an impact on the price and scalability of these technologies. Recycling the materials that make up these systems can alleviate these economic challenges by reducing dependence on the supply of raw materials and reducing overall costs. From this point of view, this work is a perspective analysis and examines the current research on the recycling of SOFC and SOEC materials, highlighting the potential paths towards a circular economy. The existing literature on different approaches to recycling the key materials for components of SOFCs and SOECs is important. Mechanical separation techniques to isolate these components, along with potential strategies like chemical leaching or hydrometallurgical and material characterization, to ensure the quality of recycled materials for reuse in new SOFCs and SOECs are important as well. By evaluating the efficiency of various methods and the quality of recovered materials, this study aims to provide valuable insights for advancing sustainable and economically viable SOFC and SOEC technologies within a net-zero economic framework. Full article

Rare earth metals are critical components for many industries. The extraction of rare earth metals from mineral raw materials presents many problems, both of a technological and theoretical nature. The use of man-made sources imposes strict requirements on the process. Thermodynamic and kinetic data that could describe the most detailed technological water–salt leaching and precipitation systems are insufficient. The study addresses the problem of a small amount of data on the formation and equilibrium of carbonate–alkali systems of rare earth metals. Isotherms of solubility of sparingly soluble carbonates with the formation of carbonate complexes are presented to evaluate equilibrium constants logK at zero ionic strength for Nd −11.3, Sm −8.6, Gd −8.0, and Ho −7.3. To accurately predict the system under consideration, a mathematical model was developed, which allows to calculate the water–salt composition. The initial data for calculation are concentration constants of stability of lanthanide complexes. This work will contribute to deepening knowledge about rare earth elements extraction problems and will serve as a reference for studying the thermodynamics of water–salt systems. Full article

To limit the oxidation of waste rocks that originates from mining operations and the subsequent leaching of acidic solutions with high concentration of metal ions, a tailing–rock–clay triple layer capillary cover system was developed to prevent rainwater infiltration in humid climatic regions. The fine grained soil (FGS) layer consists of mine tailing and a hydrodesulfurization (HDS) clay from waste-water treatment with a 95:5 mass ratio. The coarse grained soil (CGS) layer consists of local waste rock granules with a size of 1–10 mm. Methyltrimethoxysilane (MTMS), an oxidation-inhibiting agent with strong hydrophobicity, was passivated on the rock grains to further reduce water infiltration and leaching of metal ions. Prototype-scale column tests were performed with matric suction and water content measurements under 680 min rainfall of 60 mm/h, the most severe annual precipitation case scenario for the Dexing Copper Mine (Jiangxi Province, China, 28.95° N, 117.57° E, humid climate). Both the uncoated and the coated covers exhibited zero leakage throughout the experiment. The passivation on rock granules in the coated cover increased the water entry value (WEV) of the CGS layer to −0.56 kPa. This led to a 15 mm water storage increment in the overlain FGS layer as compared to that in the uncoated cover, and induced lateral drainage (5% of the precipitation) in the FGS layer, which was not overserved in the uncoated cover. The concentrations of the leached Fe²⁺, Cu²⁺, Zn²⁺, Mn²⁺ and Mg²⁺ cations drained from the CGS layers of the uncoated cover were 0, 0.4, 0.8, 73.5, and 590.5 mg/L, which are all within the regulation limits of industrial discharge water standards. The concentrations of Cu²⁺, Mn²⁺ and Mg²⁺ cations drained from the coated CGS layer were reduced by 1–3 orders of magnitude. The abovementioned laboratory studies validated the water retention and leaching prevention abilities of the proposed three-layer capillary covers and the MTMS coating, which hold promises in engineering applications. Full article

Glyphosate is a widely used herbicide, and it is an important environmental pollutant that can have adverse effects on human health. Therefore, remediation and reclamation of contaminated streams and aqueous environments polluted by glyphosate is currently a worldwide priority. Here, we show that the heterogeneous nZVI–Fenton process (nZVI + H₂O₂; nZVI: nanoscale zero-valent iron) can achieve the effective removal of glyphosate under different operational conditions. Removal of glyphosate can also take place in the presence of excess nZVI, without H₂O₂, but the high amount of nZVI needed to remove glyphosate from water matrices on its own would make the process very costly. Glyphosate removal via nZVI–-Fenton was investigated in the pH range of 3–6, with different H₂O₂ concentrations and nZVI loadings. We observed significant removal of glyphosate at pH values of 3 and 4; however, due to a loss in efficiency of Fenton systems with increasing pH values, glyphosate removal was no longer effective at pH values of 5 or 6. Glyphosate removal also occurred at pH values of 3 and 4 in tap water, despite the occurrence of several potentially interfering inorganic ions. Relatively low reagent costs, a limited increase in water conductivity (mostly due to pH adjustments before and after treatment), and low iron leaching make nZVI–Fenton treatment at pH 4 a promising technique for eliminating glyphosate from environmental aqueous matrices. Full article

Adoption of zero-tillage practices with residue retention in field crops has been introduced as an alternative soil-management technique to counteract the resource degradation and high production costs derived from intensive tillage. In this sense, the biophysical models are valuable tools to evaluate and design the most suitable soil-management technique in view of future climate variability. The aim of this study was to use the ARMOSA process-based crop model to perform an assessment of tillage (T) and no-tillage (No-T) practices of durum-wheat-cropping systems in the Campania region (South of Italy) under current and future climate scenarios. First, the model was calibrated using measurements of soil water content at different depths, leaf area index, and aboveground biomass in the T and No-T treatments during the 2013–2014 season. Then, the model was further applied in the T and No-T treatments to future climate data for 2020–2100 that was generated by the COSMO-CLM model using the RCP4.5 and 8.5 paths. Results of the calibration depicted that the model can accurately simulate the soil-crop-related variables of both soil-management treatments, and thus can be applied to identify the most appropriate conservation agricultural practices in the durum-wheat system. The simulation of soil water content at different depths resulted in small relative root mean square errors (RRMSE < 15%) and an acceptable Pearson’s correlation coefficient (r > 0.51); and the goodness-of-fit indicators for simulated LAI and AGB resulted in acceptable RRMSE (RRMSE < 28%), and high r (r > 0.84) in both soil-management treatments. Future climate simulations showed that No-T management will deliver 10% more wheat yield than the T, with an annual average 0.31% year⁻¹ increase of soil organic carbon, and an increase of 3.80% year⁻¹ for N uptake, which can diminish the N leaching. These results suggest that No-T could be implemented as a more resilient management for farming system in view of climate uncertainty and scarcity of resources. Therefore, these findings support the potential of the ARMOSA model to evaluate the soil-crop response of the durum-wheat system under different management conditions and to design appropriate soil-management practices for current and future climate predictions. Full article

Silage maize is, after grassland, the second largest crop in the Netherlands. The amounts of nutrients applied to silage maize have greatly decreased since the 1980s because of the implementation of a series of environmental policies. The aim of this review paper was to provide an overview of the nutrient management of and losses from silage maize cropping systems in the Netherlands during recent decades based on a literature review and a time series of nitrogen (N) and phosphorus (P) uses, yields, surpluses, and losses. The total N input as slurry to silage maize on sandy soils decreased from up to 500 kg N/ha in 1985 to approximately 180 kg N/ha in recent years. This decrease was due to the implementation of legislation with maximum permissible P application rates in the 1980s and 1990s, maximum permissible N and P losses in the 1997–2005 period, and of maximum permissible N and P application rates from 2006 onwards. Implementation of low ammonia (NH₃) emission application techniques of manure in the early 1990s greatly reduced NH₃ emission. The relative decrease of N losses from silage maize on sandy soils in the 1995–2018 period was 70% for nitrate (NO₃) leaching, 97% for NH₃ emissions, 65% for nitrogen oxide (NO) emissions, and 32% for nitrous oxide (N₂O) emissions. The P surplus on the soil balance of silage maize decreased from approximately 150 kg P₂O₅/ha in the 1980s to less than 10 kg P₂O₅/ha in recent years, showing that P inputs and outputs are currently coming close to a zero balance in silage maize cropping systems. Although the emissions from silage maize cultivation have greatly decreased, further improvements in nutrient management are needed. The water quality standards have still not been met and there are new challenges related to the mitigation of emissions of ammonia and greenhouse gases. Full article

Mixing municipal solid waste incineration fly ash (MSWIFA) with industrial by-products such as ground granulated blast furnace slag (GGBFS) and ladle furnace slag (LFS) can lead to a hardened system which can encapsulate the heavy metals present in the MSWIFA. The objective of this study is to find optimal mixture designs to effectively encapsulate these heavy metals. The nature of the hydrates and the strength of the mixtures are studied to develop a sustainable and practical construction material incorporating MSWIFA. Heavy metals including Cr, Cu, Zn and Cd are safely encapsulated in several developed mixtures with leachate concentration below EPA drinking water limit. The encapsulation behavior is complex and depends on metal type, age of testing, and hydration products. In general, mixtures containing LFS have more aluminate hydrates, and show greater encapsulation capacity for most heavy metals. However, they also generally show significant Sb leaching. Mixtures which show satisfactory encapsulation for all ions and adequate strength development are identified. Three ideal mixtures, including one containing zero cement, are identified which satisfy both leaching and strength requirements. Full article

Greenhouse cultivation is highly efficient in the use of water and fertilizers. However, due to intensive production, the greenhouse industry applies ample amounts of water and fertilizers. An alternative to minimize water and nutrient loss is zero-leaching systems, such as closed-loop subirrigation. The objective of the present study was to compare the water and fertilizer use efficiency in containerized tomato plants grown in a subirrigation system and a drip irrigation system. Subirrigated plants exhibited lower biomass than drip-irrigated plants. However, the amount of nutrient solution required to restore evapotranspirated water was lower in subirrigation. The yield was marginally decreased in subirrigated plants compared to drip-irrigated plants. The amount of nutrient solution required to produce 1 kg of fresh tomatoes was 22 L in subirrigation, whereas in drip irrigation, plants demanded 41 L. The total nitrogen applied through the nutrient solution was 75% lower in subirrigation than in drip irrigation, while the phosphorus, potassium, calcium and magnesium applied was 66%, 59%, 70% and 74% lower, respectively. We concluded that the subirrigation system proved to be more water- and nutrient-efficient than the drip irrigation system due to the zero leaching of the nutrient solution, the lower number of irrigation events required and the lower nutrient demand of plants. Full article

Adsorption properties of waste brick dust (WBD) were studied by the removing of Pb^II and Cs^I from an aqueous system. For adsorption experiments, 0.1 M and 0.5 M aqueous solutions of Cs⁺ and Pb²⁺ and two WBD (Libochovice—LB, and Tyn nad Vltavou—TN) in the fraction below 125 µm were used. The structural and surface properties of WBD were characterized by X-ray diffraction (XRD) in combination with solid-state nuclear magnetic resonance (NMR), supplemented by scanning electron microscopy (SEM), specific surface area (S_BET), total pore volume and zero point of charge (pH_ZPC). LB was a more amorphous material showing a better adsorption condition than that of TN. The adsorption process indicated better results for Pb²⁺, due to the inner-sphere surface complexation in all Pb²⁺ systems, supported by the formation of insoluble Pb(OH)₂ precipitation on the sorbent surface. A weak adsorption of Cs⁺ on WBD corresponded to the non-Langmuir adsorption run followed by the outer-sphere surface complexation. The leachability of Pb²⁺ from saturated WBDs varied from 0.001% to 0.3%, while in the case of Cs⁺, 4% to 12% of the initial amount was leached. Both LB and TN met the standards for Pb^II adsorption, yet completely failed for any Cs^I removal from water systems. Full article

The introduction of a saturated zone (SZ) has been recommended to address the issue of nitrogen removal fluctuation in the bioretention system, which is one of the most versatile low-impact development facilities for urban stormwater management. Nine experimental columns were used to characterize the nitrogen concentration variations over the outflow during wetting periods and in SZ during the antecedent drying periods (ADPs), as well as compare removal efficiencies of various nitrogen species in systems with different SZ depths under alternate drying and wetting conditions. Results indicated that NO₃⁻-N concentrations in the outflow showed quasi-logistic curve-shaped variations over time: being low (<0.5 mg/L) in the early process, sharply increasing thereafter, and finally flattening around 3.0 mg/L with NO₃⁻ leaching; NH₄⁺-N and organic nitrogen (ON) concentrations were consistently low around 0.5 mg/L and 1.8 mg/L, respectively during the wetting periods. NH₄⁺ removal efficiency in bioretention systems was consistently high around 80%, not varying with the increasing SZ depth; ON removal efficiency had a slight rise from 57% to 84% and NO₃⁻ removal efficiency was significantly enhanced from −23% to 62% with the SZ depth increasing from 0 to 600 mm. Deeper SZ could store more runoff and promote more denitrification of NO₃⁻ and mineralization of ON during the ADPs, providing more “old” water with low NO₃⁻ and ON concentrations for water exchange with “new” inflow of higher NO₃⁻ and ON concentrations during the wetting periods. The total nitrogen (TN) removal, a combined result of the instantaneous removal through adsorption and retention in the upper soil layer during the wetting periods and the gradual removal via denitrification and mineralization in SZ during the ADPs, was also improved by increasing the SZ depth; TN removal efficiency was elevated from 35% to 73% when the SZ depth increased from zero to 600 mm. Full article