Search Results (1,550)

Niobium and tantalum are critical metals that are important for technological development. Their main applications are in the production of alloys for the civil construction, electronics, nuclear, and aerospace industries, and in catalysis. Tin reduction slag is a possible secondary source of niobium and tantalum, containing 3.7% and 0.5% of Nb and Ta, respectively. The slag matrix is mainly composed of calcium silicate, a low-reactivity material that prevents contact between the leaching solution and the metals to be extracted; therefore, it is necessary to previously react the material with molten NaOH. This reaction converts calcium silicates into sodium silicates, which are more reactive and water-soluble, and converts the metals into oxyanions, niobates, and tantalates, which are more reactive species. After treatment with molten hydroxide, the material is then solubilized in water; this reaction removes part of the soluble materials and also fragments the silicate matrix. Nb and Ta remain in the solid phase during the water washing step and then undergo acid leaching, where, after the parameters are evaluated, Nb extraction of 96% and Ta leaching of less than 3% are achieved, using a concentration of 10 mol/L H₂SO₄, a time of 2 h, a temperature of 90 °C, and a liquid–solid ratio of 50. Full article

Significant volumes of wastewater and solid by-products are produced by olive oil industries worldwide, posing serious environmental challenges. This study presents an innovative circular economy and environmental sustainability approach that simultaneously valorizes liquid (olive mill wastewater, OMW) and solid by-products (crushed olive pits) rom olive oil production through hydroponic lettuce cultivation. The OMW was pretreated and supplemented with nutrients (OMW-N) to create a hydroponic solution for lettuce (Lactuca sativa) cultivation using crushed olive pits as growing substrate. A hydroponic system fed with a nutritive solution was used as a control. Lettuces grown in the OMW-N system achieved a 100% survival rate with no signs of phytotoxicity, although they exhibited a significant reduction in fresh mass (approx. 66%) and size, compared to the control. The sensory analysis revealed no significant differences in consumer acceptance, except for slightly lower color intensity, with 40% of participants explicitly indicating a purchase preference for the OMW-N lettuce, validating its commercial feasibility. Results demonstrated that OMW-N system functioned as a tertiary treatment, achieving additional removal of nutrients. Overall, integrating treated OMW and olive pits into hydroponics is a feasible strategy to convert agro-industrial waste into value-added food products, reducing the environmental footprint of the olive sector. Full article

Refuse-derived fuel (RDF) presents a viable strategy to concurrently address the challenges of municipal solid waste management and the need for alternative energy. In this context, the present review systematically synthesizes recent advances in RDF preparation, combustion behavior, and efficient utilization technologies. The study examines the full chain of RDF production—including waste selection, mechanical/optical/magnetic sorting, granulation, briquetting, and chemical modification—highlighting how pretreatment technologies influence fuel homogeneity, calorific value, and emissions. The thermochemical conversion characteristics of RDF are systematically analyzed, covering the mechanism differences among slow pyrolysis, fast pyrolysis, flash pyrolysis, pyrolysis mechanisms, catalytic pyrolysis, fragmentation behavior, volatile release patterns, and kinetic modeling using Arrhenius and model-free isoconversional methods (e.g., FWO). Special attention is given to co-firing and high-efficiency combustion technologies, including ultra-supercritical boilers, circulating fluidized beds, and rotary kilns, where fuel quality, ash fusion behavior, slagging, bed agglomeration, and particulate emissions determine operational compatibility. Integrating recent findings, this review identifies the key technical bottlenecks—feedstock variability, chlorine/sulfur release, heavy-metal contaminants, ash-related issues, and the need for standardized RDF quality control. Emerging solutions such as AI-assisted sorting, catalytic upgrading, optimized co-firing strategies, and advanced thermal conversion systems (oxy-fuel, chemical looping, supercritical steam cycles) are discussed within the broader context of carbon reduction and circular economy transitions. Overall, RDF represents a scalable, flexible, and high-value waste-to-energy pathway, and the review provides insights into future research directions, system optimization, and policy frameworks required to support its industrial deployment. Full article

Root-zone temperature is a critical environmental parameter affecting the development, physiology, and nutritional status of leafy vegetables in soilless systems such as the nutrient film technique (NFT) and aeroponics. In the present article, we report on responses of mini Romaine lettuce (Lactuca sativa L.) upon cultivation using heated nutrient solution targeting minimum temperatures of 14, 18, and 22 °C versus ambient (control; 11–12 °C), both in the NFT and in the aeroponics system. In both systems, the higher temperatures (i.e., 18 and 22 °C) led to considerably higher leaf mass per system area (127–232% in NFT; 54–75% in aeroponics) and leaf length (more than 21% in all cases). Root dry weight and total soluble solids were positively affected by increasing temperatures only in the NFT. Performance indices of the photosynthetic mechanism (PI_abs and PI_tot) were increased in the lower temperatures in the NFT. Antioxidant activity and total phenolics were not affected in either soilless system. Total chlorophylls and carotenoids were enhanced by 18 and 22 °C in the NFT and aeroponics, respectively, while anthocyanins were also variably affected. Finally, nitrate content was significantly reduced (−42%) in 18 °C in the NFT. Sub-optimal root-zone temperatures constrained root development and biomass accumulation, indicating that growth limitation was mainly driven by sink-related processes rather than carbon assimilation. Overall, heating the nutrient solution to a minimum of 22 °C in low- and mid-tech greenhouses during cool months can increase the production efficiency of mini Romaine lettuce in the NFT and aeroponics. Full article

The demand for high-quality agricultural products is increasing; however, this requirement is becoming increasingly challenging due to the effects of climate change, which can cause abiotic stress. In this research, we studied the performance of kiwifruit (Actinidia deliciosa var. ‘Hayward’) 60 days after storage for two different cultivation periods, in which a glycine betaine biostimulant (GB) was applied to the kiwi trees via irrigation under field conditions. Postharvest analysis was performed by measuring the fresh and dry weight of the kiwifruit, the soluble solids content, and titratable acidity. To assess the antioxidant traits of the kiwifruit, DPPH and ascorbic acid contents were recorded. Data analysis revealed that the GB treatment proved beneficial for kiwifruit during storage, enhancing their antioxidant capacity as indicated by their higher ascorbic acid content (vitamin C) compared to the control. This qualitative difference may benefit the commercial requirements of kiwifruit cultivation under the abiotic conditions of climate change, which prompts us to further investigate the application of amino acid biostimulants. This research complements the existing literature on the implementation of biostimulants, as reports regarding their application in kiwifruit cultivation are limited, and provides an optional solution for meeting the commercial needs of kiwifruit cultivation and improving the adaptability of kiwifruit cultivation under abiotic stress conditions. Full article

The relentless rise in global plastic consumption has intensified the challenge of managing plastic waste pollution. Current conventional recycling technologies face significant limitations in processing efficiency and environmental compatibility, hindering the effective recovery of plastic resources. Against this background, microwave pyrolysis technology has emerged as a promising solution, leveraging its dual advantages of thermal and non-thermal effects. This technology enables uniform and rapid heating, substantially reducing processing time and energy consumption. Its characteristics open new pathways for the high-value conversion of waste plastics. Through this approach, waste plastics can be efficiently transformed into valuable products such as pyrolysis oil, hydrogen gas, and solid carbon, demonstrating broad application prospects. This paper first systematically reviews the shortcomings of existing plastic pyrolysis technologies. It then delves into the operational mechanisms, process characteristics, and key influencing factors of microwave-assisted pyrolysis. Finally, it examines current challenges and issues while outlining future research directions, offering insights for the sustainable resource utilisation of waste plastics. Full article

In recent years, the rapid development of commercial satellite projects, such as low-Earth orbit (LEO) communication and remote sensing constellations, has driven the satellite industry toward low-cost, rapid development, and large-scale deployment. Commercial off-the-shelf (COTS) components have been widely adopted across various commercial satellite platforms due to their advantages of low cost, high performance, and plug-and-play availability. However, the space environment is complex and hostile. COTS components were not originally designed for such conditions, and they often lack systematically flight-verified protective frameworks, making their reliability issues a core bottleneck limiting their extensive application in critical missions. This paper focuses on COTS solid-state drives (SSDs) onboard the Jilin-1 KF satellite and presents a full-lifecycle reliability practice covering component selection, system design, on-orbit operation, and failure feedback. The core contribution lies in proposing a full-lifecycle methodology that integrates proactive design—including multi-module redundancy architecture and targeted environmental stress screening—with on-orbit data monitoring and failure cause analysis. Through fault tree analysis, on-orbit data mining, and statistical analysis, it was found that SSD failures show a significant correlation with high-energy particle radiation in the South Atlantic Anomaly region. Building on this key spatial correlation, the on-orbit failure mode was successfully reproduced via proton irradiation experiments, confirming the mechanism of radiation-induced SSD damage and providing a basis for subsequent model development and management decisions. The study demonstrates that although individual COTS SSDs exhibit a certain failure rate, reasonable design, protection, and testing can enhance the on-orbit survivability of storage systems using COTS components. More broadly, by providing a validated closed-loop paradigm—encompassing design, flight verification and feedback, and iterative improvement—we enable the reliable use of COTS components in future cost-sensitive, high-performance satellite missions, adopting system-level solutions to balance cost and reliability without being confined to expensive radiation-hardened products. Full article

Hydrometallurgical pretreatment of pyrite-bearing concentrates and tailings by hydrothermal interaction with Cu(II) solutions is a promising route for chemical beneficiation and mitigation of acid mine drainage but is limited by passivation caused by elemental sulfur and secondary copper sulfides. Here, the effect of sodium lignosulfonate (SLS) on the hydrothermal reaction between natural pyrite and CuSO₄ in H₂SO₄ media at 180–220 °C was studied at [H₂SO₄]₀ = 10–30 g/dm³, [Cu]₀ = 6–24 g/dm³, and [SLS]₀ = 0–1.0 g/dm³. Process efficiency was evaluated by Fe extraction into solution and Cu precipitation on the solid phase, and products were characterized by XRD and SEM/EDS. SLS markedly intensified pyrite conversion: at 200 °C and 120 min, Fe extraction increased from 14 to 26% and Cu precipitation from 5 to 23%, while at 220 °C, Fe extraction reached 33.4% and Cu precipitation 26.8%. XRD confirmed the sequential transformation CuS → Cu_1.8S. SEM/EDS showed that SLS converts localized nucleation of Cu_xS on defect sites into the formation of a fine, loosely packed, and well-dispersed copper sulfide phase. The results demonstrate that lignosulfonate surfactants efficiently suppress passivation and enhance mass transfer, providing a basis for intensifying hydrothermal pretreatment of pyrite-bearing industrial materials. Full article

This study aimed to systematically optimize the fermentation process for xylanase production by Aspergillus tubingensis FS7Y52, elucidate its enzymatic properties, and evaluate its application potential in the biodegradation of agricultural wastes. Key influencing factors were initially identified through single-factor experiments, followed by the screening of significant factors using the Plackett–Burman design. The optimal values were then approached employing the steepest ascent path method and Response Surface Methodology. The final determined optimal fermentation conditions were: corn husk (20–40 mesh) 40 g/L, tryptone 13.7 g/L, Tween-20 0.75 g/L, pH 6.5, fermentation temperature 42.1 °C, fermentation time 2 days, shaking speed 140 rpm, inoculum size 1 × 10⁷ spores/30 mL, and liquid loading volume 30 mL/250 mL. Under these conditions, xylanase activity reached 115.23 U/mL, representing a significant increase of 90.7% compared to pre-optimization levels. Studies on enzymatic properties revealed that the enzyme exhibited maximum activity at pH 5.0 and 55 °C, and demonstrated good stability within the pH range of 4.5–7.0 and at temperatures below 50 °C. In the degradation of agricultural waste, the enzyme system produced by this strain exhibits significant degradation effects on agricultural waste. A pronounced additive effect exists between xylanase and cellulase. When the dosages were 2430 U/g and 15.7 U/g for xylanase and cellulase, respectively, the maximum reducing sugar release reached 23.3%. The degradation rates of cellulose, hemicellulose, and lignin reached 57.8%, 51.9%, and 55.0%, respectively. Additionally, the strain itself exhibits significant degradation effects on substances such as cellulose in agricultural waste, achieving degradation rates of 78.8%, 70.8%, and 52.5% for cellulose, hemicellulose, and lignin, respectively. This study provides a solid theoretical foundation and technical support for the efficient production of xylanase by A. tubingensis and its industrial application in the resource utilization of agricultural wastes. From an economic perspective, the optimized strategy significantly enhances enzyme production efficiency while reducing substrate consumption and operational costs per unit of enzyme produced. This makes the resulting enzyme mixture more economically viable for large-scale applications. The utilization of this enzyme system to convert tobacco stems into sugars represents a compelling case for agricultural wastes reuse. It transforms residual biomass into high-value products, contributing to a circular bioeconomy by reducing waste and creating new renewable alternatives to conventional products. It provides an economically viable solution for the high-value utilization of woody lignocellulosic biomass. Full article

Concrete production contributes approximately 4–8% of global cardon dioxide emissions, largely due to Portland cement. Incorporating municipal solid waste (MSW) into concrete offers a pathway to reduce cement demand while supporting circular economy objectives. This study evaluates the mechanical performance, environmental impacts, and optimization potential of concrete incorporating three MSW-derived materials: cardboard kraft fibers (KFs), recycled high-density polyethylene (HDPE), and textile fibers. A maximum 10% cement replacement strategy was adopted. Compressive strength was assessed at 7, 14, and 28 days, and a cradle-to-gate life cycle assessment (LCA) was conducted using OpenLCA to quantify global warming potential (GWP100) and other midpoint impacts. A surrogate-based optimization implemented using Non-dominated Sorting Genetic Algorithm II (NSGA-II) was applied to minimize cost and GWP while enforcing compressive strength as a feasibility constraint. The results show that fiber-based wastes significantly reduce embodied carbon, with KF achieving the largest GWP reduction (19%) and textile waste achieving moderate reductions (10%) relative to the control. HDPE-modified concrete exhibited near-control mechanical performance but increased GWP and fossil depletion due to polymer processing burdens. The optimization results revealed well-defined Pareto trade-offs for KF and textile concretes, identifying clear compromise solutions between cost and emissions, while HDPE was consistently dominated. Overall, textile waste emerged as the most balanced option, offering favorable environmental gains with minimal cost and acceptable mechanical performance. The integrated LCA optimization framework demonstrates a robust approach for evaluating MSW-derived concrete and supports evidence-based decision-making toward low-carbon, circular construction materials. Full article

This study systematically examines the fluidity, setting time, mechanical properties, and microstructural evolution of metakaolin-based geopolymer grouting materials with a relatively high water-to-solid (W/S) ratio window. A four-factor, three-level orthogonal experimental design was employed to identify the dominant factors and main effect trends of W/S ratio, alkali dosage, water glass modulus (Ms, molar ratio of SiO₂ to Na₂O in alkali solution), and steel slag content on the material’s performance. The results indicated that the W/S ratio predominantly governed fluidity, while the alkali content was the primary controlling factor for setting time and early-age strength. An intermediate range of water glass modulus with a value of 1.6 provided balanced performance. The incorporation of steel slag with a range of 10–20% showed an age-dependent contribution: it not only tended to improve the rheology of the paste but also the later-age strength. XRD, FTIR, and SEM/EDS results suggested that the hardened binders were dominated by amorphous products, where alumimosilicate gel (N-A-S-H) and Ca-containing gel (C-S-H/C-A-S-H) may coexist depending on calcium availability and activator chemistry. The proposed parameter ranges are valid within the studied design space and provide guidance for the mix design of high-W/S geopolymer grout. Full article

Corn fermentation in biorefineries produces residual biomass and by-products, particularly corn kernel fiber and outgassed carbon dioxide (CO₂), that have value-added potential for improving sugar and bioethanol conversions. Recovered corn kernel fiber contains lignocellulosic components which can be made accessible by pretreating the biomass with an alkaline sodium carbonate solution made with captured CO₂ and then used as supplemental biomass in corn ethanol production. In this work, different ratios of whole and degermed corn kernel fibers are pretreated and mixed with corn to be evaluated as beneficial ingredients in bioethanol co-fermentation. Sugar yields from enzymatic hydrolysis demonstrate the pretreatment promotes saccharification reaching over 70% total sugar conversion for the whole corn fibers. During co-fermentation, 10 and 20% corn solid loadings significantly increased ethanol yields while additional corn fiber loadings increased sugar yields. Conversion rates and yields were similar between the whole and degermed corn fibers supporting how a single recovery design can benefit multiple corn streams. Full article

Thorium carbide (${\mathrm{ThC}}_{2\pm x}$) nano-structured thin disc-like pellets were produced from thoria nanoparticles (${\mathrm{ThO}}_2$-NP) and multi-walled carbon nanotubes (MWCNT). These composites are to be studied as a target material candidate for radioactive ion beam (RIB) production via nuclear reactions upon impact with high-energy proton beams on a stack of solid pellets. The ${\mathrm{ThO}}_2$-NP precursor was produced via precipitation of thorium oxalate from a thorium nitrate solution with oxalic acid and subsequent hydrothermal oxidation of the oxalate, creating the thoria nanoparticles. The ${\mathrm{ThO}}_2$-NP were then mixed with MWCNT in isopropyl alcohol and sonicated by two different methods to create a nanoparticle dispersion. This dispersion was then heated under medium vacuum to evaporate the solvent; the resulting powder was pressed into pellets and taken to an inert-atmosphere oven, where it was heated to 1650 °C and carbothermally reduced to ${\mathrm{ThC}}_{2\pm x}$. The resulting pellets were characterized via XRD, SEM-EDS, and Raman spectroscopy. The resulting thorium pellets exhibited, at most, trace levels of the oxide precursor. Furthermore, the nanotube structures were still present in the final product and are expected to contribute positively towards faster radioisotope release times by lowering isotope diffusion times, which is required for the efficient extraction of the shortest-lived (<1 s half-life) radioisotopes. Full article

Microbial fermentation is a key biotechnological tool for producing bioactive metabolites such as alkaloids, carotenoids, essential oils, and phenolic compounds, among others, with applications in human health, agriculture, and food industries. This review comprehensively reviews recent information on the synthesis of valuable compounds and enzymes through fermentation processes. Here, we discuss the advantages of the different types of fermentation, such as submerged and solid-state fermentation, in optimizing metabolite production by bacteria, fungi, and yeast. The role of microbial metabolism, enzymatic activity, and fermentation conditions in enhancing the bioavailability and functionality of these compounds is discussed. Integrating fermentation with emerging biotechnologies, including metabolic engineering, further enhances yields and specificity. The potential of microbial-derived bioactive compounds in developing functional foods, pharmaceuticals, and eco-friendly agricultural solutions positions fermentation as a pivotal strategy for future biotechnological advancements. Therefore, microbial fermentation is a sustainable tool to obtain high-quality metabolites from different sources that can be used in agriculture, animal, and human health. Full article

This study focuses on the development of sustainable construction materials via geopolymers synthesized from metakaolin and slag, aiming to identify environmentally friendly alternatives for construction material systems. A metakaolin–slag geopolymer mortar (MK–slag) was prepared using metakaolin and slag as fully solid waste raw materials, with sodium silicate solution and sodium hydroxide acting as composite activators. Initially, single-factor experiments were conducted to determine the optimal ranges for metakaolin–slag content, water/binder ratio, and water glass modulus. Subsequently, response surface methodology was employed to develop regression equations that analyze the main and interaction effects of these variables on the 7-day and 28-day compressive strength and water absorption of the mortar. The optimal mix ratio was then identified. The microstructure and formation mechanisms of MK–slag mortar were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP). The results indicate that all factors follow quadratic polynomial relationships with the response variables, showing a regression coefficient (R²) greater than 0.98, indicating an excellent model fit and prediction accuracy. According to model predictions, the optimal mix parameters under multi-objective optimization were found to be a metakaolin-to-slag ratio of 45%: 55%, a water/binder ratio of 0.45, and a water glass modulus of 1.3. After 28 days of curing, the primary hydration products were gel-like substances such as N-A-S-H and C-A-S-H. These gels interweave and overlap to form a high-density, structurally robust binary solid waste geopolymer mortar. This approach expands the application of solid waste materials, such as metakaolin and slag, while enhancing the recycling and utilization efficiency of these waste products. Full article