Search Results (2,831)

Geothermal energy, recognized as a sustainable and clean resource, is playing an increasingly critical role in the global shift toward low-carbon energy systems. Nevertheless, the exploitation of fractured geothermal reservoirs is often impeded by severe lost circulation during drilling, where conventional plugging materials fail under high-temperature, high-salinity, and high-pressure conditions due to inadequate mechanical strength, poor thermal resistance, and lack of self-adaptive sealing behavior. In response, self-healing materials have emerged as an innovative strategy for developing intelligent lost circulation control technologies. Herein, we report a novel self-healing gel (XFFD) synthesized via inverse emulsion polymerization using acrylamide (AM), acrylic acid (AA), p-nitroblue tetrazolium (PNBT), and modified silica nanoparticles (PAS). The resulting material exhibits exceptional thermal stability, with decomposition onset above 356 °C, as determined by thermogravimetric analysis. Rheological and mechanical assessments reveal outstanding viscoelasticity, moderate swelling capacity (4.17-fold in deionized water), and a high self-recovery efficiency of 91.15%, accompanied by a bearing strength of 3.65 MPa. Mechanistic investigations indicate that the autonomous repair capability stems from dynamic non-covalent interactions—primarily hydrogen bonding and ionic associations—enabled by amide and carboxyl groups within the polymer network. Sand bed filtration tests under simulated geothermal conditions (150 °C, 8% salinity) demonstrate that XFFD forms a robust sealing barrier with significantly shallower invasion depth compared to conventional materials such as sulfonated asphalt and calcium carbonate. This work presents an effective self-healing gel system that ensures reliable wellbore strengthening and fluid loss control in challenging high-temperature, high-salinity geothermal drilling operations. Full article

Addressing the significant pressure for carbon emission reduction in the cement industry, the development of novel cement materials capable of achieving “in situ carbon sequestration” has become an important research focus. This study introduces nesquehonite (MgCO₃·3H₂O, NQ) as a functional admixture into the Portland cement system, systematically investigating its effects on the cement hydration process, the evolution of hydration products, and its carbon sequestration efficiency. Through designed penetration resistance tests and hydration tests with a high water-to-solid ratio, this research utilized X-ray diffraction analysis to determine the phase composition and content of hydration products at different ages. This was combined with scanning electron microscopy to observe microstructural evolution and Nano Measure software 1.2.5 for ettringite crystal size measurement, analyzing the impact of NQ on the early hydration process of P.I cement. The results indicate that the incorporation of NQ significantly alters the early hydration of P.I cement. The Mg²⁺ and CO₃²⁻ ions released upon its dissolution interact with Ca²⁺ and OH⁻ in the pore solution, effectively promoting the early precipitation of carbon sequestration products such as calcium carbonate and minor magnesium-containing carbonates. The addition of 10% NQ hindered the crystallization of Ca(OH)₂ before 6 h but promoted its formation after 24 h. Mechanical property tests revealed that a sample with an optimal 3% NQ dosage not only increased the paste’s penetration resistance but also enhanced the compressive strength of the 1-day hardened sample by 8.37% compared to the plain sample, without a decrease and even a slight increase at 28 days. This enhancement is closely related to the microstructural strengthening effect induced by the carbonation products. This study confirms the feasibility of using NQ to steer the cement hydration pathway towards a low-carbon direction, revealing its dual functionality in regulating hydration and sequestering carbon within cement-based materials. The findings provide a new theoretical basis and technical pathway for developing high-performance, low-carbon cement. Full article

Microbially induced calcium carbonate precipitation (MICP) is recognized as a promising, environmentally sustainable technology with diverse applications in environmental engineering. A bibliometric analysis of 5373 publications indexed in Web of Science from 2005 to 2024 was conducted using CiteSpace and VOSviewer to identify research trends and hotspots in biomineralization and calcium carbonate (CaCO₃) studies. The results showed exponential growth in publications, increasing from 96 in 2004 to 397 in 2024 and spanning 91 interdisciplinary research areas. China, United States of America, and Germany were identified as the leading contributors. Research evolution was categorized into five distinct phases, progressing from initial crystal formation investigations to the current emphasis on underlying microbial mechanisms. Trend analysis revealed four emerging research hotspots: interfaces (0.22), crystal morphology (0.18), amorphous calcium carbonate (0.05), and bacteria (0.02). Mechanisms of MICP across bacteria, fungi, and algae were examined, revealing diverse metabolic pathways, including urea hydrolysis, denitrification, and photosynthesis. These findings suggest a paradigm shift in research toward microbial diversity and the role of extracellular polymeric substances. This shift provides valuable insights for developing sustainable biotechnological applications in environmental remediation. Full article

The present paper discusses differences in the theoretical behavior of nonconventional biomasses during combustion according to their combustion parameters, focusing on their potential for sustainable energy valorization and their contribution to sustainable development. Data were obtained through thermogravimetric analysis (TGA) of biomasses from the local Galicia–North Portugal Euroregion. The samples tested were raw, nonwoody biomasses, specifically kiwi waste and gorse, and animal-derived biomasses, poultry and turkey manure. A wood pellet was also included as a reference conventional biofuel. Nonwoody biomass samples containing kaolin and calcium carbonate were also tested. Thermogravimetric analyses were performed on each biofuel under an oxidative atmosphere at different heating rates. With these data, different combustion parameters were calculated. The TGA results showed that the mean ignition temperature observed for animal-derived fuels was about 15 °C lower than for nonwoody biomasses at every heating rate, which indicates that they start to burn at lower temperatures. These animal-derived fuels generally presented better combustion parameters, suggesting that their combustion behavior is better; however, their high ash and moisture contents are problematic. These issues would be aggravated in real facilities, making them more difficult to use as fuel. The proportion of additives used had no effect on the parameters at lower heating rates, although they started to modify their tendency at 30 °C/min. For instance, the ignition index for non-additivated kiwi waste was 174.32 (wt. %/min³) × 10⁻³ compared to 143.78 (wt. %/min³) × 10⁻³ for kiwi with CaCO₃. Full article

To address the technical challenges involved in the resource utilization of hot metal containing high levels of vanadium (V: 2–5%) and chromium (Cr: 1–5%), this study proposes a novel method based on pyrometallurgical selective oxidation for simultaneously extracting vanadium and retaining chromium. Through thermodynamic analysis and high-temperature smelting experiments, the competitive oxidation behaviors of carbon, vanadium, and chromium were revealed, and the synergistic control mechanism of temperature and oxygen partial pressure was clarified. The results indicate that within a temperature range of 1693–1753 K, adjusted over 1 h, vanadium preferentially oxidizes over carbon and chromium, while carbon effectively suppresses chromium oxidation. By optimizing ω(FeO) (10.0–15.7%), we achieved a vanadium oxidation efficiency (η_V) of 72.5–82.2% and maintained a chromium retention efficiency (100−η_Cr) exceeding 57.1%. Compared to traditional methods, which rely on high-oxygen blowing (oxygen supply: 43–195 kg/tFe), multi-stage roasting, and hydrometallurgical refining, this approach eliminates roasting and hydrometallurgical steps (such as sodium/calcium roasting and the associated leaching–precipitation units), shortens the process chain, reduces oxygen consumption (>80 kg/tFe), and lowers environmental risks (Cr oxidation reduced > 40%). This study establishes a theoretical framework for achieving sustainable V/Cr separation, enhancing resource efficiency and minimizing pollution (e.g., Cr(VI)-containing wastewater, high-salinity NH₄⁺/Na⁺ wastewater). Full article

This study aims to develop a high-performance grouting material for mine goaf backfilling, creating a green and low-carbon cementitious alternative by utilizing coal gangue and sludge as the primary precursors. Based on an orthogonal experimental design, the effects of four factors including the coal gangue/sludge ratio, activator modulus, water–binder ratio, and sodium-to-aluminum ratio on the compressive strength of the geopolymer were systematically investigated. The mineral composition and microstructure of the geopolymer were analyzed using microscopic test methods such as XRD and SEM. The test results indicate that the water–binder ratio has the most significant effect on the polymerization performance of the coal gangue/sludge-based geopolymer (CSG), with compressive strength increasing as the water–binder ratio decreases. The Ca²⁺ provided by the sludge to the reaction system directly promotes the formation of new calcium-containing products such as anorthite and calcium silicate hydrate, which play an important role in improving the strength of geopolymers. Moreover, the developed CSG exhibits a significantly lower carbon footprint compared to conventional cement-based grouting materials, aligning with the goals of sustainable and green construction. When the coal gangue/sludge ratio is 7:3, the water–binder ratio is 0.3, the sodium-to-aluminum ratio is 0.64, and the activator modulus is 1.0, the 3-day compressive strength (CS) of the geopolymer reaches 34.5 MPa, demonstrating its potential as an effective and environmentally friendly grouting material for goaf applications. Full article

Lactic acid is an important biobased chemical widely used in the production of biodegradable plastics, food, and pharmaceuticals. However, the application of flocculant Saccharomyces cerevisiae remains limited in addressing stresses such as high-glucose and inhibitor-rich conditions derived from biomass, particularly in D-lactic acid (D-LA) production. This study investigates two genetically engineered S. cerevisiae F118 strains, ΔCYB2::LpDLDH and ΔPDC1::LpDLDH, for D-LA production under high-glucose and inhibitor-stress conditions that mimic lignocellulosic hydrolysates in shake-flask fermentation. At 150 g/L glucose, ΔCYB2::LpDLDH produced 41 ± 0.73 g/L D-LA, whereas ΔPDC1::LpDLDH yielded 80 ± 1.78 g/L, corresponding to 27% and 53% of the theoretical yield, respectively. Calcium carbonate (CaCO₃) supplementation enhanced glucose consumption and strengthened flocculation in ΔPDC1::LpDLDH. The addition of 5% inhibitory chemical compounds (ICCs) consisting of furfural, HMF, and weak acids redirected carbon flux in ΔCYB2::LpDLDH toward D-LA formation and reduced ethanol byproduct accumulation. Transcriptomic analysis revealed the upregulation of stress-response genes (HOG1, TPS1) and cell-wall remodeling genes (CRH1, SCW10) in response to high-glucose stress. The strongly flocculent F118ΔCYB2::LpDLDH strain exhibited greater tolerance to weak acids and furfural than the weakly flocculent F118ΔPDC1::LpDLDH strain. Metabolomic profiling indicated that under inhibitor stress, carbon flux was diverted from the TCA cycle toward lactate synthesis to maintain redox balance. These findings highlight the multifaceted benefits of flocculation in enhancing strain robustness and D-LA productivity under harsh fermentation environments, providing insights for developing resilient yeast platforms for lignocellulosic bioprocessing. Full article

This study examines key bioprocess parameters influencing the reduction in hydraulic conductivity in porous media via Microbially-Induced Calcite Precipitation (MICP), highlighting its relevance to environmental engineering applications such as bio-barriers and landfill liners. Sporosarcina pasteurii was utilized as the ureolytic bacterium to induce calcium carbonate precipitation under controlled laboratory conditions. Experimental variables included bacterial cell density (OD₆₀₀), diameter of glass beads, concentrations of precipitation solution, bentonite, and yeast extract. A total of 42 experimental runs were conducted based on a custom design in Design-Expert software. Hydraulic conductivity was selected as the response variable to evaluate treatment performance. Response surface methodology (RSM) was applied to develop a second-order polynomial model, with statistical analyses indicating a strong model fit (R² = 0.948, adjusted R² = 0.929, predicted R² = 0.868). ANOVA confirmed the significance of the main effects and interactions, particularly those involving glass bead diameter and OD₆₀₀. Among the tested factors, the precipitation solution exhibited the strongest individual effect, while bentonite and yeast extract demonstrated supportive roles. Optimization revealed that a balanced combination of microbial density and chemical inputs minimized hydraulic conductivity to 0.0399 cm/s (≈95% reduction), with an overall desirability score of 1.000. Laboratory-scale experiments demonstrated field-scale applicability, underscoring the potential of biotechnological soil treatment and empirical modeling for developing sustainable low-permeability barriers. Full article

The valorization of biomass waste represents an important direction in green chemistry. This study successfully prepared blue fluorescent carbon dots (BP-CDs) from waste banana peels via a one-step hydrothermal method, establishing a dual-functional platform for both pollutant detection and cellular imaging. The resulting material exhibited uniform particle size (~2.05 nm), good water dispersibility, and strong fluorescence emission at 445 nm under 360 nm excitation. It maintained over 93% of its initial fluorescence intensity after 20 days, demonstrating excellent stability. Based on the inner filter effect, the probe enabled a highly selective detection of tetracycline with a detection limit of 0.191 µM and two wide linear ranges (0–15 µM, R² = 0.996; 15–95 µM, R² = 0.991). Cellular experiments confirmed the good biocompatibility of BP-CDs (cell viability > 84%) and their successful application in cell imaging. More importantly, the probe achieved visual observation and semi-quantitative analysis of the distribution and content of tetracycline in living cells, providing a direct tool for studying the cellular behavior of antibiotics. This work not only offers a new strategy for banana peel valorization but also develops a green fluorescence imaging platform suitable for tracking intracellular pollutants. Full article

China’s loess deposits exhibit high vulnerability to deformation under precipitation and snowmelt, posing significant risks to infrastructure. This study utilized enzyme-induced carbonate precipitation (EICP) to enhance the mechanical properties of Yili loess. Comparative analyses of untreated and EICP-treated samples were conducted using unconfined compression strength (UCS) tests, unconsolidated–undrained (UU) triaxial shear tests, and scanning electron microscopy (SEM). Results demonstrated that urease activity increased markedly between 25–65 °C, while calcium carbonate production peaked at 55 °C before declining. EICP treatment elevated UCS by 52% relative to untreated soil and altered the failure mechanisms: untreated specimens failed through penetrating shear cracks, whereas treated specimens exhibited compressive failure with vertical fissures. Triaxial tests confirmed enhanced properties in EICP-stabilized loess, showing 8.3–10.7% higher failure strength and 15.7% greater cohesion (increasing from 31.3 kPa to 36.2 kPa), while the internal friction angle remained largely unchanged. Microstructural analysis revealed that EICP generated continuous cementitious layers and crystal bridges of vaterite, transforming particle contacts from point-to-point to surface-to-surface interfaces. Simultaneously, crystal precipitation reduced pore sizes and increased tortuosity. These micro-scale modifications improved interparticle friction constraints and stress transfer efficiency, thereby enhancing the macroscopic mechanical performance. The findings validate EICP’s efficacy for stabilizing collapsible loess deposits and provide insights for geohazard mitigation in similar engineering contexts. Full article

Titanium implants are widely used in medicine because of their favorable mechanical properties and biocompatibility; however, the rapidly forming titanium oxide coatings do not provide an ideal bioactive surface to stimulate osseointegration. This study aims to enhance titanium implant osseointegration through anodization processes designed to incorporate elements and compounds present within human bone into the surface oxides. Commercially pure titanium grade 4 (CPTi) discs were anodized in either oxalic, malic, or ascorbic acid-based electrolytes. Each resulting oxide exhibited complex surface topographies. EDS analyses revealed that Ca, P, and Mg bone chemistry dopant elements were incorporated into each of the oxide coatings. X-ray diffraction analyses revealed combinations of anatase and calcium titanate compounds present in each oxide. Additionally, two of the anodized oxides showed calcium oxide formation, and one oxide also revealed tricalcium phosphate (α-TCP) and hydroxyapatite (HA) formation. Subsequent FTIR spectroscopy analyses revealed carbonate substitution peaks to be present in two of the oxides. This finding indicated that the TCP and HA compounds shown in the XRD analyses of one oxide represented the formation of bone-like carbonated calcium phosphate compounds. A 21-day cell culture study showed favorable cell culture responses for each of the organic-acid-based anodized oxides. Moreover, two of the oxides showed good cytocompatibility and early osteogenic differentiation compared to non-anodized titanium controls. Thus, the organic acid anodization processes developed in this study show promise to enhance future titanium implant clinical outcomes. Full article

This paper reports the spinning and wear comfort properties of polyethylene terephthalate (PET)/copolymer-PET (Co-PET) hollow yarns and their fabrics, as well as the effect of the wt.% of inorganic particles embedded in the core of the bicomponent yarns. The results are discussed in terms of the types and amounts of inorganic particles (titanium dioxide (TiO₂) and calcium carbonate (CaCO₃)) embedded in the sheath of the bi-component yarns (Kolon semi-dull (KSD), Kolon full-dull (KFD), and Kolon calcium carbonate (KCC) PET/Co-PET yarns). The three sheath/3-core bicomponent yarns developed in this study exhibited good spinnability and weavability with relatively strong tenacity and breaking strain. Their optimal spinning conditions were determined. The KCC PET/Co-PET fabric showed the greatest hollowness ratio, followed by the KFD PET/Co-PET and KSD PET/Co-PET fabrics. This might be attributed to the higher wt.% (2.5 wt.%) of CaCO₃ particles embedded in the sheath of the KCC PET/Co-PET yarns and to the larger particle size (0.8 μm) of CaCO₃. Regarding the wear comfort, the moisture management system (MMT) test indicated that the KFD PET/Co-PET fabric is suitable for market applications because of its good moisture absorption and rapid drying. The KFD PET/Co-PET fabric is useful for winter clothing applications because of its relatively high heat retention rate and lack of durability issues with washing. An examination of the wearing performance for fitness with a tactile hand feel showed that KFD and KCC/Co-PET fabrics imparted a softer tactile hand feel than the KSD PET/Co-PET fabric. On the other hand, the KCC PET/Co-PET fabric was assumed to have some issues with wearing durability. Full article

Understanding groundwater quality and its controlling mechanisms is vital for the sustainable use of water resources in agriculturally intensive regions. This study evaluates the hydrochemical characteristics, controlling geochemical processes, and overall water quality of 226 groundwater samples collected from a typical agricultural reclamation area in the Sanjiang Plain, northeastern China. Major ion compositions indicate that groundwater is predominantly of the Ca–HCO₃ type, with bicarbonate, calcium, and magnesium as the dominant constituents. Spatial and statistical analyses reveal that rock weathering—particularly the dissolution of carbonates and silicates—is the primary natural process influencing groundwater chemistry, while cation exchange contributes moderately. Anthropogenic inputs, especially from fertilizers, livestock waste, and wastewater discharge, were found to elevate concentrations of NO₃⁻, Cl⁻, and SO₄²⁻ in localized zones. The entropy-weighted water quality index (EWQI) was applied to assess overall groundwater suitability. Results show that 89.8% of samples fall into “excellent” or “good” categories, though 6.6% of samples indicate poor to very poor water quality. This study identified the hydrochemical characteristics, sources of substances, and water quality of groundwater in the reclamation area, providing a basis for scientific prevention and control, rational utilization, and protection of groundwater resources. Full article

With the rapid increase in solid waste generated worldwide, sustainable approaches for the recovery of resources considering environmental protection are required. As one of the emerging strategies in recent years, biochar has shown great potential due to its high carbon stabilization, adjustable porosity and tunability. This review focuses on the critical assessment of the available technologies for biochar upgrading, with a specific objective of biochar physicochemical functionality improvement and critical materials recovery in line with circular economy targets. We systematically review physicochemical activation methodologies, functionalizations and leaching approaches, accounting for their effects on surface area, porosity and functional group chemistry. Particular attention is paid to the dual functionality of upgraded biochar (i) as a catalyst support for thermochemical processes and (ii) as a medium for the recycling of essential nutrients (e.g., phosphorus, potassium, magnesium, calcium). It is evidenced that customized activation can further improve its adsorption and catalytic efficiency as well as promote near-total nutrition extraction. This review positions advanced biochar as an enabling multipurpose technology across sustainable material production, nutrient cycling and waste valorization in the circular bioeconomy. Full article

The purpose of this study was to evaluate how a multi-component soil conditioner consisting of zeolite, calcium carbonate, potassium humate, and Ascophyllum nodosum extract affects selected soil properties (physical, chemical, and water-related properties, as well as microbial and enzymatic properties) and the growth and grain yield of spring barley (Hordeum vulgare L.). To achieve the goal, one-year research experiments were conducted at three conventionally tilled sites, which were situated on farms across three geographically separate regions in the Kuyavian–Pomeranian Region of Midwestern Poland. Most of the chemical properties, namely, total organic C, total N, pH in KCl, cation exchangeable capacity (CEC), as well as exchangeable (Mg, Ca, K, and Na) and available (Mg, K, and P) forms of nutrients, were not significantly affected by the conditioner or sampling time. Independent of the study location, the percentage of macropores in total porosity (TP) and dissolved nitrogen content (DNt) determined in July were considerably greater in the soil treated with Solactiv compared to the reference soil. Bulk density (BD), in turn, showed the opposite tendency, also suggesting the positive effect of the studied conditioner. At all study sites, application of the conditioner significantly reduced the percentage of micropores in total porosity (TP) (by 17%), while significantly increasing the content of macropores in TP (15%) and enhancing the percentage of available and readily available water capacity (8.5% and 14%). No clear changes in the results of C and N form and enzymatic activity were noted. The activities of DHA and FDAH behave differently in each study site, making it difficult to draw clear conclusions. The cellulase was the only enzyme that was significantly and positively affected by Solactiv at all study sites and for both sampling times. The values of dry matter of roots and plants, barley root length and surface, and barley grain yield were considerably greater in soil amended with Solactiv compared to the reference soil. Because some important soil and plant properties showed a positive response toward the tested conditioner, despite the low dose used, further studies should be conducted at a larger scale, focusing on different soils and plants. Full article