Search Results (1,679)

Based on the physicochemical properties of waste phosphate-based rare earth phosphors containing glass, this paper proposes a novel recovery method for rare earth elements (REEs) that integrates pre-enrichment, alkali roasting, and enhanced leaching. Initially, preliminary enrichment of REEs was achieved through sieving to remove silicon (from glass components) and pickling to reduce calcium content (originating from calcium phosphate compounds). The enriched material was then subjected to alkaline roasting, followed by washing for impurity removal, hydrochloric acid leaching, and finally oxalic acid precipitation to extract the rare earth elements. Experimental results demonstrate that the overall recovery rate of rare earth oxides (REO) reached 96.6%, indicating highly efficient extraction and separation of REEs from the waste phosphors. Furthermore, the mechanism of the alkali roasting process was investigated via differential thermal analysis (TG-DSC). Microstructural and phase changes in the waste phosphors before and after roasting were systematically characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that green phosphor (REPO₄) was converted into rare earth oxides and water-soluble sodium phosphate under alkaline roasting conditions. The Na₃PO₄ could be effectively removed through washing, while the rare earth elements were retained in the form of oxides within the washed residue. This study provides an important theoretical foundation and technical approach for the efficient recovery of rare earth resources from waste phosphate-based phosphors. Full article

Facility agriculture is essential for modernizing the production of horticultural plants, while long-standing over-fertilization and improper tillage in some vegetable facilities in northern China have resulted in reduced soil quality, increased greenhouse gas (GHG) emissions, and diminished vegetable yields and quality. This study systematically analyzed the deteriorating health of typical cucumber facility soils in Hebei Province, China, induced by long-term over-fertilization. Based on field surveys, we explored dynamic changes in soil physicochemical properties across different durations of over-fertilization. Subsequently, a series of field trials were conducted to assess whether reducing nitrogen application, either alone or when combined with microbial agents, could ameliorate soil properties, reduce greenhouse gas emissions, and enhance cucumber productivity. The initial field assessment revealed severe topsoil salt and nutrient accumulation, with water-soluble salt content in 5-year-old greenhouses from Yongqing soaring to 3.82 g·kg⁻¹, nearly eight times the level found in 1-year-old plots. Field experiments demonstrated that a 20% reduction in nitrogen application from the conventional rate of 900 kg·hm⁻² effectively mitigated salt accumulation, improved the structure of the microbial community, and maintained cucumber yield at 66,914 kg·hm⁻², an output comparable to conventional practices. More notably, integrating this 20% nitrogen reduction with an inoculation of Bacillus megaterium reduced the overall global warming potential by 26.7% and simultaneously increased cucumber yield to 72,747 kg·hm⁻². The most comprehensive strategy combined deep tillage, soybean straw incorporation, and B. megaterium application under reduced nitrogen, which boosted nitrogen use efficiency by 13.7% and achieved the highest yield among all treatments. In conclusion, our findings demonstrate that a combined approach of nitrogen reduction, microbial amendment, and straw application offers an effective strategy to restore soil health, enhance crop productivity, and mitigate environmental impacts in protective vegetable production systems. Full article

Corn (Zea mays L.) ranks among the most important cereal crops globally, extensively cultivated for food, animal feed, and industrial applications. Its large-scale production generates substantial amounts of agricultural residues such as cobs, husks, stalks, leaves and other, which are often underutilized, leading to environmental concerns. Due to their high carbon content, lignocellulosic structure, and abundant availability, these residues represent a sustainable and low-cost raw material for the synthesis of activated carbon. Corn waste-derived activated carbon has emerged as a promising material for the efficient removal of heavy metals from aqueous solutions. Its high surface area, well-developed porosity, and adjustable surface chemistry, referring to the functional groups on the adsorbent surface that can be modified to enhance affinity toward metal ions, facilitate effective adsorption. This review provides a comprehensive overview of (1) the potential of corn waste biomass as a precursor for activated carbon production, (2) methods of carbonization and activation that influence the textural and chemical properties of the resulting adsorbents, (3) adsorption performance for heavy metal removal under varying experimental parameters such as pH, initial concentration, contact time, and adsorbent dosage, (4) adsorption mechanisms responsible for heavy metal uptake. Reported maximum adsorption capacities vary for different metals, ranging from 2.814–206 mg/g for lead, 0.21–87.72 mg/g for cadmium, 9.6246–175.44 mg/g for chromium, and 0.724–643.92 mg/g for copper. Utilizing corn waste not only provides an eco-friendly approach for managing agricultural residues but also supports the development of efficient adsorbents. Nevertheless, challenges such as scaling up production and evaluating adsorbent performance in real wastewater samples remain and require further investigation. Finally, the review highlights key challenges and knowledge gaps in current research and offers recommendations for future studies aimed at advancing the practical application of corn waste–based activated carbons in water treatment. Full article

As freely available but not yet commercially acquired biomass resource, water care material (WCM) is generated seasonally in the periodic maintenance of surface water bodies and consists of mainly aquatic and/or rural-associated biomass of the water body profile, as well as wood, soil substrate, water or other possible impurities. In addition to other recovery options, such as composting or utilization in biogas production, hydrothermal carbonization (HTC) was selected as a thermochemical process because it is suitable for converting biomass with a high content of carbon into high-quality combustibles. The biomass sample used in this investigation was obtained during a single sampling event from a small stream in the North German lowlands. The material was pretreated by shredding it to a particle size of <0.12 mm. Through a 5 L stirred reactor, hydrothermal treatments were performed under low temperature conditions (200, 220 and 240 °C), residence times (120, 180, 240 min) and solid dry matter of the sample content: 6%. Solid phase was evaluated in terms of calorific value and proximate and ultimate analysis. The results suggested that the hydrothermal carbonization of WCM gave a high heating value of 23.84 MJ/kg for its char after being dried for 24 h at 105 degrees. At the same time, biochar can be used in agriculture to improve soil properties. To understand to what extent the product is suitable for soil amendment, the surface and the nutrient content of the resulting hydrochar were analyzed in detail. As the initial material is rich in fiber contents, process temperatures up to 240 °C have a huge impact on effective particle size. Furthermore, the analysis of selected nutrients, minerals and heavy metals shows the suitability of the produced hydrochar for soils in accordance with current legislation. Full article

New compostable materials have been developed to replace single-use soft materials such as polyurethane foams (PUR). To this end, eco-friendly systems have been formulated on the basis of agar gels prepared in mixed solvent (glycerol/water) to meet specifications, i.e., stiffness of several hundred kPa, reasonable extensibility, and good stability when exposed to open air. While the addition of glycerol slows down gelation kinetics, mechanical properties are improved up to a glycerol content of 80 wt%, with enhanced extensibility of the gels while maintaining high Young’s moduli. Swelling analyses of mixed gels, in water or pure glycerol, demonstrate the preservation of an energetic network, with no change in volume, in pure water and the transition towards an entropic network in glycerol related to the partial dissociation of helix bundles. Dimensional and mechanical analysis of gels aged in an open atmosphere at room temperature shows that the hygroscopic character of glycerol enables sufficient water retention to maintain the physical network, with antagonistic effects linked to relative increases in glycerol, which tends to weaken the network, and agar, which on the contrary strengthens it. Complementary analyses carried out on aged agar gels formulated with an initial glycerol/water mass composition of 60/40, the most suitable for the targeted development, enabled the comparison of the properties of agar gels favorably with those of PURs and verified their stability during long-term storage, as well as their non-toxicity and compostability. Full article

Straw return is crucial for sustainable agriculture, but its efficiency is limited by low temperatures in cold regions, especially in saline-alkali soils. This study investigates the degradation process of maize straw and the response of soil properties and microbial communities during the winter low-temperature period in the alkaline farmland of Anda, China. A two-year field experiment with straw return (SR) and no return (NR) treatments was conducted. Straw degradation rates and structural changes (as observed via scanning electron microscope, SEM) were monitored. Soil physicochemical properties and enzyme activities were analyzed. Microbial community composition was characterized using 16S rRNA and ITS sequencing. The cumulative straw degradation rate over two years reached 94.81%, with 18.33% occurring in the first winter freeze–thaw period. Freeze–thaw cycles significantly damaged the straw structure, facilitating microbial colonization. Straw return significantly improved soil properties after winter, increasing field water capacity (3.45%), content of large aggregates (6.57%), available nutrients (P 38.17 mg/kg, K 191.93 mg/kg), and organic carbon fractions compared to NR. Microbial analysis revealed that low temperatures filtered the community, enriching cold-tolerant taxa like Pseudogymnoascus, Penicillium, and Pedobacter, which are crucial for lignocellulose decomposition under cold conditions. The winter period plays a significant role in initiating straw degradation in cold regions. Straw return mitigates the adverse effects of winter freezing on soil quality and promotes the development of a cold-adapted microbial consortium, thereby enhancing the sustainability of alkaline farmland ecosystems in Northeast China. Full article

River ecosystems provide essential services that sustain human well-being and ecological integrity, yet their contributions are often underestimated in management and policy decisions. This study aims to develop and validate indicators for quantifying river ecosystem services to support evidence-based decision-making. A review of previous studies was conducted to compile a preliminary list of indicators. Expert evaluations were then applied using the Analytical Hierarchy Process (AHP) and content validity ratio (CVR) analysis to assess their representativeness and reliability. The results identified priority indicators across provisioning, regulating, and cultural services. The findings revealed that, in the AHP analysis, regulating services received the highest weight (0.4567), followed by provisioning services (0.3811) and cultural services (0.1622). In the CVR analysis, four valid indicators were identified for provisioning services, sixteen for regulating services, and eight for cultural services. These findings highlight the importance of careful indicator selection and methodological transparency. The study contributes a refined set of indicators that can inform river restoration initiatives, sustainable water management, and integration into national ecosystem accounting systems. Full article

The acid number is widely recognized as one of the most essential and frequently used indicators for evaluating the degradation state of lubricants. Changes in acid number serve as a direct reflection of the oil’s oxidative deterioration. Conventional prediction methods, however, often neglect the coupling effects among multiple physical factors and lack sufficient dynamic adaptability. Therefore, this study proposes a method for predicting the variation trend of lubricating oil acid number by integrating an Adaptive Neuro-Fuzzy Inference System (ANFIS) with Subtractive Clustering (SC), establishing an SC-ANFIS-based predictive model. The subtractive clustering technique automatically determines the number of fuzzy rules and initial parameters directly from the dataset, thereby eliminating redundant rules and simplifying the model architecture. The SC-ANFIS model further optimizes the parameters of the fuzzy inference system through the self-learning ability of neural networks. Lubricant aging tests were conducted using a laboratory oxidation stability tester. Regular sampling was carried out to acquire comprehensive lubricant performance degradation data. The input variables of the model include the current acid number, carbonyl peak intensity, metal element concentrations (Fe and Cu), viscosity, and water content of the lubricating oil, while the output variable corresponds to the rate of change in the acid number of the lubricating oil relative to the previous time step. The proposed model demonstrates effective prediction of the lubricating oil acid number variation trend. Posterior difference tests confirmed its high predictive accuracy, with all three evaluation metrics—RMSE, MAE, and MAPE—outperforming those of the BP model. Full article

Soil piping is the process by which subsurface water creates and enlarges channels, or “pipes,” within soil, enabling rapid and preferential flow beneath the surface. The collapse of these eroded pipes can lead to land degradation, gully formation, and potential damage to overlying infrastructure. While the structural consequences of pipe collapse are well recognized, there is limited understanding of the factors controlling pipe collapse and how water within the pipe influences moisture levels within a slope. This study used physical models of unsaturated slopes to examine how compaction conditions, pipe characteristics, and hydraulic conditions affect the progression of internal erosion. Models were created with different initial pipe sizes, moisture contents, densities at compaction and levels of pipe connectivity. Volumetric water content (VWC) sensors and cameras were used to monitor the slope response to subsurface flow, and measurements of pipe geometry were collected after the tests. Results showed that lower initial soil water content was more susceptible to pipe collapse, while higher water content showed improved pipe stability and sustained preferential flow. Fully connected pipes grew through erosion due to the pipe flow, while disconnected pipes grew mainly through local pipe collapse. Hydraulic equilibrium and soil erodibility affected the final pipe morphology more than the initial pipe size. These experimental results demonstrate that soil fabric and hydraulic connectivity of the pipe control the progression of piping, likelihood of collapse, and movement of water within the soil matrix. Full article

The performance of resin anchoring agents in deep coal mine roadways is significantly compromised by water-bearing and chemically aggressive conditions, posing a major threat to support system reliability. This study aims to systematically quantify this performance deterioration and develop a more resilient material solution for these challenging environments. A comprehensive experimental program was conducted, including uniaxial compression, pull-out, and interface shear tests, accompanied by the systematic improvement of the resin formulation and microstructural analysis via Scanning Electron Microscopy (SEM). The results showed that increasing borehole water content to 30% reduced the compressive strength of conventional resin by over 40%, while acidic environments (pH = 5) caused a 70% drop in its interfacial shear strength. In contrast, an improved formulation incorporating hydroxypropyl acrylate and a super absorbent polymer (SAP) exhibited a 20% higher initial strength, maintained over 85% of its strength under water saturation, and retained functional residual strength in acidic conditions. SEM analysis confirmed that the improved resin’s denser microstructure suppressed interfacial microcrack formation. The findings demonstrate that the improved formulation provides a robust material basis for enhancing the long-term durability and safety of anchorage support systems in extreme underground engineering environments. Full article

Chemical fertilizers are commonly used to supply phosphorus and other nutrients to crops, but due to high affinity of soils for P fixation, over-application of P fertilizer is common, which may result in groundwater and surface water pollution. To increase P use efficiency, different strategies, including different fertilizer formulations and types, have been developed. Two struvite-based fertilizers, Crystal Green^® (CG) and Crystal Green Pearl^® (CGP), are touted as environmentally safe, because they are insoluble in water but soluble in organic acids exuded from crop roots. The objective of this study was to assess fate and transport of P from diammonium phosphate (DAP), CG, and CGP through two loam soils with a significant difference in their initial P content. Two loamy soils, one collected from an experimental field receiving fertilizer continuously since 1985 and one from an adjacent area receiving no fertilizer, and a pure sand control were packed in 5 cm diameter and 5 cm long columns. Several grains equivalent to approximately 80 mg P from each fertilizer were imbedded at the bottom of the column. Distilled water was passed through the soil columns from the bottom at a relatively constant rate, and the outflow was collected every two hours using a fraction collector. Outflow samples from each treatment combination were analyzed for P by the colorimetric method, and the amount of P retained by the soils along the column at the end of the water application was determined by the nitric acid digestion method. Approximately 91% of P in DAP, 34% in CG, and only 3.8% in CGP was transported through the sand column. In contrast, the amounts of P transported were approximately 42.2% for DAP, 6.4% for CG, and 0.4% for CGP through the high-P soil and 22.4% for DAP, 0.6% for CG, and almost zero for CGP through the low-P soil. Overall, the results show a high solubility and transport for DAP, very low transport for CGP, and somewhat low to medium transport for CG fertilizers. In addition, the results show that even the high-P soil that has received fertilizer for about 40 years has the capacity to fix significant amounts of P. Full article

Extruded whole flours from blends of cereals and pulses have great potential to be key ingredients in the development of more innovative gluten-free products, both from a technological and nutritional perspective. The objective of this work was to obtain pre-cooked flours from four formulations based on blends of whole cereals (PR: parboiled brown rice; PM: pearl millet) and pulses (CP: chickpea; CB: common bean). CB was fixed at 10%, and the other components (PR-PM-CP) were set at 60-15-15 (F1), 15-60-15 (F2), 15-15-60 (F3), and 30-30-30 (F4), which were extruded at two combined conditions of feed moisture and screw speed: mild E1 (30% and 300 rpm) and severe E2 (18% and 600 rpm). The temperature profile was kept constant from 25 to 130 °C (from feed to output). The protein, dietary fiber, and ash contents in the raw formulations varied from 11.2 to 17.4%, 9.8 to 15.0%, and 2.2 to 3.3%, respectively, according to the low or high pulse content in the blend. As more mechanical energy was delivered to the raw formulations (W·h/kg, 63.7 for E1 and 179.4 for E2), the extruded particles had increased water absorption (g/g) from 1.7 to 4.5 (E1) or 3.8 (E2), increased water solubility due to E2 from 10.9 to 20.9%, and decreased oil absorption (g/g) from 1.5 to 0.9 (E1 and E2). The peak viscosity (PV, cP) was noticeable only in the raw formulation F2 (355), which decreased 10.3% due to E1. In the other formulations, PV appeared due to E1 in F1 (528), F3 (420), and F4 (371), while it disappeared due to E2 in all formulations. However, at the E2 condition, they did show cold viscosity in the initial stage (222 to 394 cP). The final viscosity (FV, cP) decreased from 795 to 390 (E1) or 123 (E2). In F2, the contents of phenolic compounds (285 µg GAE/g) and ABTS⁺ (13.2 μmol TE/g) were more than twice that in the other formulations, and their respective degradations were low due to E1 (4.2 and 12%) and high due to E2 (16 and 17%). Extrusion cooking did not cause significant changes in the luminosity (81) and redness (0.9) of particles, while yellowness increased from 15.7 to 18.2 (E1) or 18.7 (E2). Based on these findings, it is concluded that both extrusion conditions improved the technological and functional properties. Regarding the formulations, F2 stood out for being rich in antioxidant capacity, which poorly degraded under the conditions studied. Further work is needed to contribute to understanding the optimization of formulas and processes that would improve the nutritional, sensorial, and functional properties while still preserving the bioactive value of the final products. Full article

The water retention and permeability characteristics of loess are core factors governing geological disaster prevention and engineering stability in the loess regions of northwest China. This study focuses on Yangling loess, systematically conducting soil water characteristic curve (SWCC) measurements and saturated permeability tests under different initial compaction degrees and water contents using a pressure plate apparatus and a TST-55 permeameter. By combining fitting analyses of the Gardner, Fredlund–Xing, and Van Genuchten SWCC models, the study reveals the influence mechanism of initial conditions on the water retention properties of Yangling loess. Furthermore, the unsaturated hydraulic conductivity of loess was predicted using the Van Genuchten–Mualem model. Finally, a quantitative relationship model between hydraulic conductivity and multiple factors (initial compaction degree, water content, and matric suction) was constructed using the response surface methodology. The results indicate the following: (1) A higher initial compaction degree and water content lead to a higher air entry value of loess, resulting in stronger water retention capacity. Among the three models, the Van Genuchten model exhibits the optimal fitting effect for the SWCC of Yangling loess. Its parameter a (related to the air entry value) decreases significantly with increasing compaction degree, while parameter n (pore size distribution index) increases linearly. The SWCC model, considering compaction degree, established based on these findings, can accurately predict the water retention characteristics in the high suction range (0~1200 kPa). This model’s precision in the high-suction segment is particularly valuable, as it addresses a critical range for engineering applications where soil behavior transitions from near-saturated to highly unsaturated states. (2) When loess transitions from a saturated to an unsaturated state, the hydraulic conductivity decreases up to 10⁴ times. Both increased initial compaction degree and water content lead to a significant reduction in hydraulic conductivity. This drastic reduction highlights the sensitivity of loess permeability to saturation changes, which is attributed to the rapid reduction in interconnected pore channels as soil suction increases and pore spaces are filled or compressed under higher compaction. (3) The response surface prediction model quantitatively reveals the influence weights of various factors on hydraulic conductivity in the order of matric suction > initial compaction degree > initial water content. The model exhibits a high coefficient of determination (R² = 0.9861), enabling rapid and accurate prediction of the hydraulic conductivity of Yangling loess. This high precision confirms that the model effectively captures the complex interactions between the factors, providing a reliable tool for practical engineering calculations. This study provides a new model and experimental basis for the accurate prediction of unsaturated loess hydraulic properties. The proposed SWCC model, considering compaction degree and the response surface model for hydraulic conductivity, offers practical tools for engineers and researchers, facilitating more precise design and risk assessment in collapsible loess areas. Full article

In low-permeability reservoirs, studying reservoir sensitivity is crucial for optimizing water flooding, as it identifies detrimental mineral-fluid interactions that can cause formation damage and reduce injection efficiency. However, existing diagnostic methods for sensitivity-induced damage rely on post-facto pressure monitoring and lack a quantitative relationship between sensitivity factors and water injectivity impairment. Furthermore, correlating microscale interactions with macroscopic injectivity parameters remains challenging, causing current models to inadequately represent actual injection behavior. This study combines microscopic techniques (e.g., SEM, XRD, NMR) with macroscopic core flooding experiments under various sensitivity-inducing conditions to analyze the influence of reservoir mineral composition on flow capacity, evaluate formation sensitivity, and assess the dynamic impact on water injectivity. The quantitative relationship between clay minerals and injectivity impairment in low-permeability reservoirs is also investigated. The results indicate that flow capacity is predominantly governed by the type and content of sensitive minerals. In water-sensitive reservoirs, water injection induces clay swelling and migration, leading to flow path reconfiguration and water-blocking effects. In salt-sensitive formations, high-salinity water promotes salt precipitation within pore throats, reducing permeability. In velocity-sensitive formations, fine particle migration causes flow resistance to initially increase slightly and then gradually decline with continued injection. Acidizing generally enhances pore connectivity but induces pore-throat plugging in chlorite-rich reservoirs. Alkaline fluids can exacerbate heterogeneity and generate precipitates, though appropriate concentrations may improve connectivity. Under low effective stress, rock dilation increases porosity and permeability, while elevated stress causes compaction, increasing flow impedance. Full article

Against the backdrop of global climate change intensifying seasonal freeze–thaw cycles, deteriorating soil conditions in farmland within seasonal frost zones constrain agricultural sustainability. This study employed an in situ field experiment during seasonal freeze–thaw periods in the black soil zone of Northeast China to investigate the joint regulatory effects of seasonal freeze–thaw processes and tillage practices on multidimensional features of soil bacterial communities. Key results demonstrate that soil bacterial communities possess self-reorganization capacity. α-diversity exhibited cyclical fluctuations: an initial decline followed by a rebound, ultimately approaching pre-freeze–thaw levels. Significant compositional shifts occurred throughout this process, with the frozen period (FP) representing the phase of maximal differentiation. Actinomycetota and Acidobacteriota consistently dominated as the predominant phyla, collectively accounting for 33.4–49% of relative abundance. Bacterial co-occurrence networks underwent dynamic topological restructuring in response to freeze–thaw stress. Period-specific response patterns supported sustained soil ecological functionality. Furthermore, NCM and NST analyses revealed that stochastic processes dominated community assembly during freeze–thaw (NCM R² > 0.75). Tillage practices modulated this stochastic–deterministic balance: no-tillage with straw mulching (NTS) shifted toward determinism (NST = 0.608 ± 0.224) during the thawed period (TP). Across the seasonal freeze–thaw process, soil temperature emerged as the primary driver of temporal community variations, while soil water content governed treatment-specific differences. This work provides a theoretical framework for exploring agricultural soil ecological evolution in seasonal frost zones. Full article