Search Results (832)

The sustainable valorization of marine shell waste as functional additives for geopolymer materials represents a promising strategy for developing multifunctional materials for environmental remediation. In this study, metakaolin-based geopolymers were modified with calcium-rich particles obtained by calcination of five marine shell species (Chamelea gallina, Mya arenaria, Mytilus edulis, Pecten maximus, and Rapana venosa) under identical synthesis conditions to evaluate the influence of shell mineralogy on the structural, textural, adsorption, and antibacterial properties of the resulting composites. The materials were comprehensively characterized by Fourier transform infrared spectroscopy in attenuated total reflectance (ATR-FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption–desorption (BET/BJH) analyses. Functional performance was assessed through methylene blue (MB) adsorption experiments, adsorption kinetic modeling, and antibacterial tests against Escherichia coli (E. coli). ATR-FTIR and XRD analyses confirmed the formation of a stable amorphous geopolymer network containing residual crystalline phases together with shell-derived calcium carbonate, predominantly as calcite or aragonite depending on shell origin. The incorporation of shell-derived particles modified the pore architecture of the geopolymers. GP-SJ exhibited the highest BET specific surface area (94.30 m² g⁻¹) and the most developed mesoporous structure. Among the investigated formulations, GP-RP showed the most favorable overall combination of functional properties under the investigated conditions, exhibiting the highest methylene blue removal efficiency (63.97%) and experimental adsorption capacity at 160 min (9.60 mg g⁻¹), together with a comparatively high reduction in recoverable E. coli colonies during preliminary antibacterial screening. The combined structural and functional analyses demonstrate that the environmental performance of shell-modified geopolymers cannot be predicted from a single parameter such as BET surface area or calcium content alone, but results from the synergistic interaction between mineralogical composition, particle dispersion, pore accessibility, and matrix compactness. Under the investigated conditions, these findings provide evidence for proposed structure–property correlations under the investigated conditions and suggests that shell-derived calcium particles act as microstructural regulators of geopolymer matrices, providing a basis for the further development of sustainable multifunctional materials for simultaneous dye removal and bacterial reduction in wastewater treatment. Full article

The Earth’s environment is deteriorating, and biodiversity is declining. The use of plant-based cellulose nanofibers (CNFs) as structural materials can reduce environmental impact, and further technological developments are anticipated. This review article introduces types of cellulose derived from wood, weeds, bamboo, and fruits, and examines the potential technological applications of CNFs. It is hypothesized that maintaining an appropriate content of Mn, Ca, and O—including the interactions of Ca within carbon-based structures—could contribute to plant health, while the exclusion of elements such as V, Cd, and Sn (regardless of the effectiveness of partial sequestration) could promote cell activity. Calcium deposition can influence wood growth depending on the elemental composition in the bark, and a hypothesis regarding pH adjustment for shoot formation is proposed (see textbook on inorganic chemistry). Furthermore, manufacturing processes for CNFs and their mechanical properties—including evaluation methods—are summarized. This overview focuses on nanostructures that exhibit heterogeneous functional and mechanical properties and offer potential benefits in reducing environmental impact through processes such as 3D printing and coating. CNFs derived from fruit peels can yield lightweight and durable materials. Furthermore, the roles of proteins and fruit-derived components in neutralizing acidic environments and reducing oxides are discussed. A concept is proposed that links the processing of fruit-peel-based materials with environmental applications such as forest restoration and combating desertification. The hypothesis is put forward that cytoplasmic activity and cell wall strengthening could be enhanced through chlorophyll-related processes and water transport mechanisms. Optimizing pH conditions could promote shoot formation in plants such as conifers. Sustainable greening can be achieved through the use of cellulose-based materials in combination with water-retaining components such as bamboo-derived resources. The interaction between CNFs, plant bark, and water-bound proteins can contribute to forest regeneration and the curbing of slash-and-burn practices. Overall, this approach can contribute to environmental remediation, the reduction of environmental impact, and urban greening in degraded regions. Full article

Conventional solvent-based and hot-melt road marking paints face significant challenges regarding high volatile organic compound (VOC) emissions and limited durability, necessitating the development of eco-friendly, high-performance alternatives. In this study, a waterborne acrylic road marking paint was systematically formulated and optimized using an L₁₆(4⁵) orthogonal experimental design coupled with a comprehensive weighted scoring method integrating subjective and objective (entropy) weights. Four key formulation parameters (pigment-to-binder ratio, titanium dioxide content, ground calcium carbonate content, and coalescing agent dosage) were investigated, with abrasion resistance, hiding power, luminance factor, and stain resistance as evaluation criteria. The optimized formulation was identified through range analysis of comprehensive scores and subsequently subjected to rigorous performance characterization, including retroreflectivity optimization, Taber and accelerated abrasion testing, UV-accelerated weathering, skid resistance, and VOC emissions measurement using a self-designed sealed chamber system. Benchmark comparisons against commercial waterborne and hot-melt paints demonstrated that the developed formulation achieves superior abrasion resistance, exceptional weatherability, and meaningfully lower VOC emissions. Field application on an operational highway section in Liaoning Province, China, confirmed the practical constructability and performance reliability of the optimized paint under real-world construction conditions. This research provides both theoretical guidance and practical validation for the design of sustainable, durable, and highly visible road marking materials, contributing to the advancement of environmentally responsible transportation infrastructure. Full article

Objective: To investigate the effect of milk minerals on bone mineral density (BMD) and bone quality in growing rats and explore the underlying mechanisms related to calcium absorption, bone metabolism, and the gut–bone axis. Methods: Sixty healthy 4-week-old male Sprague-Dawley (SD) rats were randomly divided to five groups based on their body weight: Low-Calcium Control Group (Control), Low-Dose milk mineral Group (Low), Medium-Dose milk mineral Group (Medium), High-Dose milk mineral Group (High) and Calcium Carbonate Control Group (CaCO₃), which received the same dose level (elemental calcium) as the High group. The milk mineral dosage was set at 5, 10, and 15 times the human recommended intake of elemental calcium. After 12 weeks of intervention, femurs were collected for analysis of BMD, bone microstructure, and bone mechanical strength. Additionally, analyses included calcium levels in the femur, feces, and diet; serum bone metabolism biomarkers; tissue protein expression; as well as gut microbiota composition and short-chain fatty acid content. Result: Milk mineral exhibited non-inferior efficacy to CaCO₃ in increasing femoral calcium content, enhancing BMD, and improving bone microarchitecture. Notably, the Medium group achieved comparable bone-protective effects to the CaCO₃ group despite a 20.8% lower calcium content, which was accompanied by a relatively high calcium absorption rate (90.9% vs. 86.5%). With respect to serum markers, milk mineral maintained bone formation while suppressing bone resorption, resulting in a net anabolic state comparable to that of CaCO₃. Milk mineral significantly upregulated the protein expression of renal CYP27B1 and intestinal calcium ion transporters, and increased serum IGF-I levels. Furthermore, milk mineral promoted the enrichment of certain specific gut microbial genera, which showed a significant positive correlation with IGF-I, bone calcium content and BMD. Conclusions: Milk mineral supplementation appears to promote bone formation and mineralization in growing rats, accompanied by enhanced intestinal calcium absorption, enrichment of characteristic gut microbes and elevated microbial metabolite concentrations. Full article

Calcareous sand is widely used in marine and island reef engineering; however, its low strength and severe particle breakage are further exacerbated under dynamic loading, making the dynamic performance of reinforced calcareous sand critical to engineering safety. Nevertheless, research on the dynamic characteristics of EICP/MICP-reinforced calcareous sand remains very limited. The dynamic performance was evaluated using Split Hopkinson Pressure Bar (SHPB) tests, and the results were compared with UCS data to examine the effects of particle gradation and fiber content on both dynamic and static behaviors. The results show that dynamic strength increases with calcium carbonate content (CCC) and impact pressure. Under the same CCC, the dynamic strength is consistently higher than the static strength, with a maximum difference of up to 2.5 MPa. Fiber incorporation significantly enhances structural integrity, and SEM analysis reveals that this improvement stems from effective bonding between fibers and cementitious materials. Based on the static and dynamic test results, the optimal mix ratio for EICP-reinforced calcareous sand is determined as 50% coarse sand content and 0.4% fiber content by mass, which provides theoretical support and design parameters for sustainable green reinforcement of calcareous sand foundations in marine and island reef engineering. Full article

Environmental variability poses major challenges to bread wheat production in arid regions. This study evaluated the adaptation, productivity, and grain quality of fifteen diverse bread wheat genotypes. The evaluated germplasm comprised advanced breeding lines developed by the Arab Center for the Studies of Arid Zones and Dry Lands (ACSAD), Saudi landraces, newly released cultivars, and a cultivar derived from the International Maize and Wheat Improvement Center (CIMMYT). Field experiments were conducted over two consecutive growing seasons (2022/2023 and 2023/2024) at two contrasting arid environments in Saudi Arabia. Riyadh exhibited warmer, drier conditions, with higher soil calcium carbonate content than Hail. Significant effects (p ≤ 0.01) of genotype, environment, and genotype-by-environment interaction were detected for all traits studied. Compared with Hail, Riyadh exhibited lower grain and biological yields, fewer spikes/m², lighter grains, reduced plant height, and shorter growth duration. Riyadh-1 achieved the highest grain yield (7.54 t/ha) and biological yield (21.44 t/ha). ACS-1454, ACS-1422, ACS-1372, and Maeaa also demonstrated superior productivity and adaptation. Local landraces were characterized by late heading and maturity, whereas ACS-1454, ACS-1422, ACS-1400, and ACS-1464 exhibited early phenology across environments. LR-12 and LR-599 exhibited the highest protein and gluten contents, whereas Riyadh-1 and Yecora recorded the highest gluten index values. Multivariate analyses, including principal component analysis, hierarchical clustering, and AMMI identified Riyadh-1, ACS-1454, ACS-1422, ACS-1372 and Maeaa as promising candidates for cultivation and breeding. Furthermore, the local landraces (LR-12 and LR-599) represent valuable sources of adaptive genetic diversity and grain quality for climate-resilient wheat cultivars. Full article

Ultra-high-performance concrete (UHPC) typically contains high cement and steel-fiber contents, leading to high cost and carbon emissions. This study developed a low-carbon UHPC by partially replacing cement with industrial solid waste (ISW) composed of ground granulated blast-furnace slag and calcium carbide slag, and by partially replacing steel fibers with recycled plastic fibers (RPF). The effects of ISW and RPF on flowability, mechanical properties, hydration behavior, microstructure, carbon emissions, and raw-material cost were investigated. ISW had a limited influence on flowability, whereas RPF markedly reduced flowability. Appropriate ISW and RPF contents increased flexural and compressive strengths by up to 41.02% and 14.93%, respectively. The 30% ISW-50% RPF mixture provided the highest flexural strength, while 30% ISW-30% RPF achieved the highest compressive strength with acceptable flowability. Hydration heat, XRD, SEM, and FTIR analyses showed that moderate ISW promoted early hydration and C-S-H/C-A-S-H gel formation, whereas excessive ISW caused dilution and reduced matrix compactness. Therefore, 30% ISW-30% RPF is recommended as the balanced formulation, whereas 50% ISW-50% RPF is more suitable for carbon- and cost-sensitive applications and maintains approximately 150 MPa compressive strength. Full article

This study provides an in-depth investigation of the influence of calcium carbonate (CaCO₃) filler on the mechanical performance and aging resistance of polyvinyl chloride (PVC)-based composites. PVC/CaCO₃ composites containing 2.5, 5, and 7.5 wt% of CaCO₃ were subjected to accelerated aging under combined ultraviolet (UV) irradiation and thermal stress for up to 1248 h. The key mechanical properties of specimens —tensile strength and elongation at break—were measured before and after aging. Changes in surface morphology, coloration, hydrophobicity, and chemical composition were characterized using scanning electron microscopy (SEM-EDS), X-ray spectroscopy, atomic force microscopy (AFM), contact angle measurements, and carbonyl index calculation to quantify relationships between the structural and physical properties of the specimens and aging conditions. The results reveal a significant correlation between filler content and the mechanical behavior of aged specimens, highlighting the potential of CaCO₃ reinforcement not only to improve the retention of mechanical properties but also to increase the service life of PVC-based insulation compounds. Full article

To address the environmental hazards caused by massive bauxite red mud stockpiles, phase-change unburned bricks have been developed. The slump flow and initial setting time of fresh mortar were tested, while the flexural strength, compressive strength, splitting tensile strength and rebound hardness of hardened mortar specimens were measured. The synergistic influence of stearic acid on mechanical strengths, rebound hardness and thermal conductivity was revealed, and the corresponding indoor simulation tests were performed. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Ultra-depth-of-field microscope cross-section scanning were adopted to interpret the intrinsic microstructure and inner mechanism. Results indicate that slump flow, initial setting time and all mechanical indices follow cubic functional relationships with red mud mass ratio. Specimens incorporating 20 wt.% red mud achieve the optimal mechanical strength, rebound hardness and thermal conductivity, with the maximum growth rates of up to 32.7%, 18.7% and 27.0%, respectively. Appropriately, straw fibers improve the mechanical properties and rebound hardness yet reduce thermal conductivity. In simulated thermal cabin tests, wall temperature continuously rises under heating and declines after heat termination; red mud and straw fibers jointly slow the heating-up rate and post-heating cooling rate. Samples with 5 wt.% red mud possess the densest hydration matrix. Red mud promotes the generation of ettringite (AFt), calcium carbonate and dolomite crystals, and elevates the content of dicalcium silicate (C₂S) within the binder system. This study provides a reference for fabricating functional wall materials using industrial solid waste (red mud) and agricultural solid waste (straw fibers). Full article

The valorisation of industrial by-products as supplementary cementitious materials is a promising strategy to reduce clinker consumption and improve the sustainability of cement-based materials. In this study, the influence of submerged arc welding (SAW) slag on the hydration behaviour and microstructural evolution of cement pastes was investigated. Two SAW slags from different industrial sources were incorporated as partial replacements of ordinary Portland cement at 5%, 15%, and 30% by mass. Cement pastes were prepared with water-to-binder ratios of 0.3 and 0.4 and characterised through setting time, water demand, mercury intrusion porosimetry (MIP), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The results showed that SAW slag systematically delayed both initial and final setting times, while having only a negligible effect on water demand. Under the fixed mix conditions adopted in this study, this retardation is interpreted as the combined effect of clinker dilution and modified fresh-state conditions. MIP analysis revealed higher early-age porosity in SAW-containing pastes, particularly at high replacement levels and higher water-to-binder ratios, although mixtures with up to 15% slag approached the reference pore structure at later ages. Thermal analysis indicated lower bound water and portlandite contents at early ages, mainly due to clinker dilution, while long-term hydration development remained comparable at moderate replacement levels. At higher slag contents, some mixtures showed higher calcium carbonate contents, suggesting a tendency toward increased carbonate formation under the investigated conditions. Overall, the results indicate that SAW slag primarily affected early paste behaviour and pore structure development, with clinker dilution appearing to be the main mechanism, although weak secondary physical or chemical contributions cannot be completely excluded. Full article

Microbially induced calcium carbonate precipitation (MICP) is a promising biotechnology for environmental remediation; however, the high cost of conventional chemical-grade calcium sources limits its large-scale scalability. This study evaluated the feasibility of utilizing an aqueous extract of natural attapulgite clay as a sustainable, low-cost calcium source for MICP-mediated arsenic (As) immobilization in both aqueous and soil systems. Among the tested minerals, Baiyin attapulgite (group B) exhibited the highest calcium content (62,808.94 mg kg⁻¹) and minimal toxic metal impurities, providing a favorable chemical matrix for biomineralization. At an optimal solid-to-liquid ratio of 1:10, Lysinibacillus fusiformis LF and Enterococcus LZU-1 successfully induced calcite precipitation driven by the attapulgite extract. In batch aqueous remediation experiments (20 days), the attapulgite extract significantly enhanced As removal efficiency compared to the controls; As removal rates peaked at 66.4% for strain LZU-1 (with LZ1 extract) and 65.8% for strain LF (with group B extract), drastically outperforming the standard CaCl₂ groups (31.2–37.3%) and blank controls (21.8–24.5%). Concurrently, soil incubation experiments (30 days) demonstrated that the combined application of attapulgite and MICP bacteria reduced the highly bioavailable exchangeable As fraction from 0.115 to approximately 0.03 mg kg⁻¹, while effectively driving its transformation into more stable carbonate-bound and organic-bound fractions without causing secondary soil salinization. Morphological and mechanistic analyses revealed that, compared to the well-defined euhedral crystals in the CaCl₂ control, the precipitates mediated by the clay extract exhibited distinctly irregular, defect-rich rhombohedral structures. This structural disruption was governed by the natural matrix effect of attapulgite, which simultaneously supplied dissolved Ca²⁺ and provided an abundance of fine clay fragments, calcite micro-grains, and associated amorphous Fe/Al/Mn-bearing phases. These constituents acted as physical scaffolding and heterogeneous nucleation sites that became embedded in the growing CaCO₃ lattice, driving the formation of highly reactive, defect-rich clay-calcite-arsenic composite precipitates that efficiently encapsulated arsenate. Mantel analysis further revealed that the remediation efficiency was significantly correlated with key environmental variables including Ni, V, Ca. These findings highlight the dual-system potential of natural attapulgite as an inexpensive, eco-friendly calcium alternative for sustainable MICP-based remediation of As-contaminated water and agricultural soils. Full article

Background: Adsorption-based solidification is a solvent-free route to prepare a solid form of self-nanoemulsifying drug delivery systems (SNEDDS). However, the limited drug loading and the low bulk density of the porous carrier restrict its pharmaceutical applicability. This study developed a pH-modulated SNEDDS in which sodium carbonate modulates the pH of the formulation microenvironment. Atorvastatin calcium and glibenclamide were used as high-dose and low-dose weakly acidic model drugs. Methods: The SNEDDS components were selected by solubility and emulsification screening. Sodium carbonate was incorporated as the pH-modulating agent, and liquid formulations were solidified by adsorption onto Syloid. The formulations were characterized by FTIR, PXRD, and SEM, and evaluated by an in vitro dissolution study. Results: The selected liquid SNEDDS (L-SNEDDS) consisted of polysorbate 80, polyethylene glycol 400, and glyceryl monocaprylate. Sodium carbonate increased the microenvironmental pH from 5.31 to 6.83. This increased drug loading by approximately 2.0-fold for atorvastatin calcium and 3.0-fold for glibenclamide. FTIR showed no chemical interaction between the components. SEM confirmed adsorption within the porous carrier, whereas PXRD showed no detectable drug crystallinity. The increased loading reduced the number of capsules required per dose from two to one for atorvastatin calcium and from four to one for glibenclamide. In vitro dissolution confirmed that pH modulation did not compromise drug dissolution despite the reduced SNEDDS content per dose. Conclusions: pH modulation with sodium carbonate enabled single-capsule dosing and provided a solvent-free route to boost drug loading for the two investigated model drugs. Full article

Ion-type rare earth tailings are mechanically weak and may release Pb and Zn, posing both geotechnical and environmental risks. Basalt-fiber-reinforced microbially induced carbonate precipitation (BF-MICP) was investigated as a combined solidification/stabilization treatment for these tailings. By integrating peak and post-peak mechanical responses, heavy-metal leaching, the spatial distribution of calcium carbonate (CaCO₃), and microstructural characterization, this study distinguishes the respective contributions of microbial mineralization and fiber reinforcement. Tailings specimens were treated with basalt fiber contents ranging from 0 to 0.8% and evaluated using unconfined compression tests, leaching tests, CaCO₃ measurements, X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy with energy-dispersive spectroscopy. The unconfined compressive strength first increased and then decreased with increasing fiber content, reaching 1.72 MPa at 0.4% fiber, approximately 90% higher than that of the MICP-only group. At the same fiber content, compressive total energy absorption increased from approximately 18 to 68 kJ·m⁻³, indicating a marked improvement in post-peak toughness. BF-MICP treatment increased the CaCO₃ content to approximately 2–3 times that of untreated tailings, although the deposits remained more abundant in the outer region than in the core, and the total CaCO₃ content varied little with fiber dosage. The leached concentrations of Pb and Zn decreased by 79–81% and 81–84%, respectively, with no clear additional reduction as the fiber dosage increased. Microstructural analyses showed that calcite-dominated deposits connected tailing particles and fiber surfaces. These results indicate that MICP primarily governed mineral cementation and heavy-metal immobilization, whereas basalt fibers mainly improved load transfer, crack bridging, and post-peak structural integrity. A fiber content of 0.3–0.4% provided the best overall balance between mechanical performance and leaching control. Full article

Marine silt is characterized by a high content of fine particles and low permeability, which often result in uneven urease diffusion, local enrichment, and significant variations in solidification performance during soybean urease-induced calcium carbonate precipitation (SICP) treatment. To address these issues, this study experimentally investigated both the preparation of marine silt mechanical specimens and the injection uniformity of the SICP technique. A cylindrical transparent acrylic mold together with a matching grouting device was developed to enable the observable and standardized preparation of marine silt specimens. On this basis, a series of experiments were conducted, including measurements of urease distribution under single SICP grouting, unconfined compressive strength (UCS) tests of solidified specimens, and quantification of calcium carbonate production. The effects of injection direction, injection volume, and injection rate on solidification uniformity and mechanical strength were systematically examined. The results show that the grouting direction governs the stratification characteristics of urease within the specimens. Increasing the grouting volume significantly enhances the total urease content and improves its distribution uniformity. The UCS of the solidified specimens was found to be closely related to the uniformity of urease distribution. Among the tested methods, the multi-round alternating injection mode from both the top and bottom produced the best overall strength performance. The maximum UCS reached 93.81 kPa at a grouting volume of 150 mL and a grouting rate of 5 mL/min. This study clarifies how injection parameters can be optimized to improve the solidification uniformity of fine-grained marine sediments and provides technical support and parameter references for the standardized preparation of SICP-solidified soil mechanical specimens. Full article

This study presents a novel, low-temperature thermochemical activation process for the selective extraction of Cr and V from carbon steel EAF (CH1) and FeCr (CH2) slags at temperatures of up to 600 °C. Of the twelve reagents tested, NaOH was identified as the optimal alkaline agent for Cr activation at 500 °C, achieving extraction yields of 61.6% for CH1 (slag-to-reagent ratio of 12:8 g) and 80.6% for CH2 (ratio of 12:16 g). KOH at 400 °C was the most effective reagent for V extraction, yielding 89.4% for CH1 and 54.5% for CH2. Maximum metal concentrations were achieved after only five minutes of leaching at 60 °C. The process exhibits high selectivity; primary matrix components (Fe, Si, Al, Ca, Mg) either do not leach or only leach in negligible amounts. Iron forms insoluble oxides, and calcium converts into stable calcite, while magnesium is bound in the form of hydrotalcite specifically in the CH2 slag leaching residue. The CaCO₃ content was proven to be a crucial parameter determining the activation efficiency and effective transformation of Fe-Cr-V phases. This procedure enables the recovery of clean Cr and V leachates, while the residual mineral-rich fraction offers potential for various industrial applications in a closed-loop slag recycling process. Full article