Search Results (3,402)

To enhance the ductility of coal mine filling materials using recycled asphalt pavement (RAP) and address the limitations in RAP recycling and utilization, this study processed RAP into crushed materials (CMs) and ball-milled materials (BMs). Supplementary with fly ash (FA) and cement, RAP-fly ash cement paste backfill (RFCPB) was prepared. For 1000 g of RFCPB slurry, the composition was 365 g CM, 73 g cement, 270 g water, and a total of 292 g of FA and BM, with an F/B ratio ranging from 1:7 to 7:1. A systematic test program was carried out, including rheological property tests, unconfined compressive strength (UCS) tests combined with deformation monitoring, microstructure analysis, and leaching toxicity tests. Based on these tests, the influence of F/B ratio on the action mechanism, workability, mechanical properties, ductility and environmental compatibility of RFCPB was comprehensively explored. The results show that the rheological behavior of RFCPB slurry conforms to the Herschel–Bulkley (H-B) model; with the decrease in F/B ratio, the yield stress and apparent viscosity of the slurry increase significantly, while the slump and slump flow decrease correspondingly, which is closely related to the particle gradation optimization by BM. For mechanical properties and ductility, the 28-day UCS of RFCPB first increases and then decreases with the decrease in F/B ratio, all meeting the mine backfilling strength requirements; notably, the increase in BM proportion regulates the failure mode from brittle to ductile, which is the key to improving ductility. Microstructural analysis indicates that Dolomite and Albite in BM participate in hydration reactions to generate N-A-S-H and C-A-S-H gels, which fill internal pores, optimize pore structure, and thus synergistically improve UCS and ductility. Additionally, the leaching concentration of toxic ions in RFCPB complies with the environmental protection standards for solid waste. This study provides a theoretical basis for enhancing backfill ductility and advancing the coordinated disposal of RAP and fly ash solid wastes. Full article

This study examines the influence of virgin polyethylene (vPE), recycled polyethylene (rPE), and Aerosil (A) on the performance of bitumen binders modified with partially devulcanized rubber (DVR). The experimental program included morphology analysis, determination of devulcanization degree, dynamic viscosity measurements, shear stress–shear rate analysis, load–displacement (F–Δl) testing, storage-stability evaluation, ring and ball softening point (R&B), penetration (P), and elastic recovery (ER) testing. The results show that DVR-rPE-modified bitumen binders exhibit 20–35% higher viscosity and up to 25% greater elongation at the break compared to DVR-vPE-modified bitumen systems, indicating more effective interaction with the bitumen matrix. The incorporation of Aerosil increased viscosity ca. 1.5–2 times for DVR-rPE and DVR-vPE-modified systems, respectively. Meanwhile, top and bottom differences in R&B decreased by a factor of 1.6–5 for DVR-rPE and DVR-vPE-containing composites, respectively, demonstrating significant enhancement in structural stability during storage. Mechanical testing further revealed that DVR-rPE + A binders absorbed 10–20% more deformation energy and consistently maintained ER values above 70–80%, corresponding to a higher elastic recovery grade at 25 °C. Overall, the DVR-rPE + A system provided the most balanced improvements in rheological, mechanical, and thermal properties, confirming its potential for use in high-performance, thermally stable, and environmentally sustainable bituminous materials for pavement applications. Full article

The electrochemical reduction of CO₂ to ethanol represents a sustainable alternative to recycle CO₂ into a value-added product, yet achieving high selectivity and efficiency remains a challenge. This work explores Cu-based catalysts supported on SiO₂ and ZrO₂, with and without ZnO doping, for ethanol production in a continuous flow-cell system. Gas diffusion electrodes are fabricated using commercial catalysts with varying Cu loadings (5–10%) and ZnO contents (2–3.5%). Comprehensive characterization by XPS confirms the presence of Cu²⁺ and Zn²⁺ species, while SEM reveals that ZnO incorporation improves surface uniformity and aggregate distribution compared to undoped samples. Electrochemical tests demonstrate that 10% Cu on SiO₂ achieves a Faradaic efficiency of 96% for ethanol at −3 mA cm⁻², outperforming both doped catalysts and previously reported materials. However, efficiency declines at higher current densities, indicating a trade-off between selectivity and productivity. ZnO doping enhances C₂⁺ product formation but does not surpass the undoped catalyst in ethanol selectivity. These results underline the importance of catalyst composition, support interactions, and operating conditions, and point to further optimization of electrode architecture and cell configuration to sustain high ethanol yields under industrially relevant conditions. Full article

Alkali-activated materials (AAMs) or geopolymers have been considered for many years as a sustainable substitution for the traditional ordinary Portland cement (OPC) binder. However, their production needs energy consumption and creates carbon emissions. Since construction and demolition waste (CDW) can become precursors for manufacturing alkali-activated materials, their use as substitutes for traditional AAM (such as metakaolin, blast furnace slag, and fly ash) can solve both the problem of their disposal and the problem of sustainability. Furthermore, CDW can also be used as aggregate replacement, avoiding the exploitation of natural river sand and gravel. A new circular economy could be created based on CDW recycling, creating a new eco-friendly building practice. Unfortunately, this process is quite difficult owing to several variables that should be taken into consideration, such as the possibility of separating and sorting the CDW, the great variability of CDW composition, the cost of the mechanical and thermal treatment, the different parameters that compose an alkali-activated mix-design, and public opinion still being skeptical about the use of recycled materials in the construction sector. This review tries to describe all these aspects, summarizing the results of the most interesting studies performed on this subject. Today, thanks to a comprehensive protocol, the use of building information modeling (BIM) software and machine learning models, a large-scale reuse of CDW in the building industry appears more feasible. Full article

In modern construction, natural materials with a low carbon footprint and full recyclability are becoming increasingly important. A typical group here is products made from solid wood, including glued wood, plywood, and wood-based composites. With their many advantages, however, they all burden the environment with the costs of production processes, as well as the need to use harmful chemicals (adhesives and impregnants). Solid wood is devoid of these disadvantages; however, it is often treated as a rather archaic material. One of the arguments here is its low durability compared to, e.g., glued wood. The article discusses the durability of solid wood using the example of a group of wooden churches preserved in Poland, in Upper Silesia. Some of these buildings are over five hundred years old, making them a reliable source of information about the durability of the material from which they were built. A total of 85 churches, at least 200 years old, were analyzed, evaluating the technical state of the main load-bearing elements of their structures. In view of the number of facilities and the inability to conduct tests in most of them, the assessment was limited to a visual inspection of the technical condition, carried out by an experienced building expert. The assessment estimated the area of corrosion damage, probed its depth, and measured the depth of cracks. The relationship between their technical condition and the environmental conditions in which they were used was described and discussed. In this way, both the threats to the durability of solid wood and the ways to keep it in good condition for hundreds of years were identified, refuting the thesis that solid wood is a material with low durability. Its use in structural elements therefore supports efficient resource management and contributes to sustainable construction, especially in small and medium-sized buildings. Full article

To address the low-value recycling dilemma of waste polyvinyl butyral (PVB) and cater to the demand for sustainable multifunctional active food packaging, this study developed a facile and cost-effective solution blow spinning approach. Continuous, smooth, and bead-free nanofiber membranes were prepared by optimizing the solution blow spinning process parameters. Zinc oxide nanoparticles (ZnO NPs) were incorporated into the PVB nanofiber membrane with vacuum impregnation. The results demonstrated that ZnO NPs significantly enhanced the tensile strength, thermal stability, and the UV absorption of PVB fiber membranes. ZnO/PVB fiber membranes exhibited antibacterial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Practical preservation tests showed that ZnO/PVB fiber membranes effectively inhibited cherry tomatoes’ microbial spoilage and water loss, extending the shelf life of tomatoes to 13 days. These findings validate the potential of ZnO/PVB composite nanofiber membranes as active food packaging and provide a feasible technical pathway for the low-cost, efficient utilization of recycled PVB. Full article

The escalating global water crisis demands the development of cost-effective and environmentally sustainable treatment technologies. Among various advanced oxidation processes (AOPs), peracetic acid (PAA) has emerged as a promising oxidant, owing to its high redox potential, chemical stability, and potent disinfection capability. Nevertheless, the lack of highly efficient catalysts remains a major obstacle to achieving the effective degradation of contaminants of emerging concern in wastewater. Heterogeneous catalysis has proven to be a viable strategy for enhancing PAA activation, highlighting the urgent need for catalysts with superior activity, stability, and recyclability. Metal–organic frameworks (MOFs), with their large surface areas, tunable porosity, and structural diversity, provide versatile platforms for catalyst design. Recently, MOF-derived materials have attracted increasing attention for PAA activation, offering a new frontier in advanced oxidation technologies for efficient and sustainable wastewater remediation. This review systematically examines the role of MOFs in PAA activation, from pristine frameworks to MOF-based composites and MOF-derived catalysts. Mechanistic insights into PAA activation are highlighted, strategies for engineering MOF-based composites with synergistic catalytic properties are discussed, and the transformation of MOFs into robust derivatives with improved stability and reactivity is explored. Special attention is given to the identification and quantification of reactive species generated in PAA systems, providing a critical understanding of reaction pathways and catalytic performance. Finally, current challenges and future directions are outlined for designing highly efficient, recyclable, and environmentally compatible MOF-based catalysts, emphasizing their potential to significantly advance PAA-based AOPs. Full article

Rubber particles have been proven to have the advantages of improving the energy absorption effect and enhancing the friction between soil particles when used to modify the soil. The rubber-modified soil technology also provides a new solution for the pollution-free disposal of waste rubber. However, when rubber particles are used to modify collapsible loess, they cannot significantly enhance its strength. Previous studies have not systematically clarified whether combining rubber particles with different cementation mechanisms can overcome this limitation, nor compared their shear mechanical effectiveness under identical conditions. In view of this, a dual synergistic strategy is implemented by combining rubber with lime and rubber with enzyme-induced calcium carbonate precipitation (EICP). Direct shear tests and scanning electron microscopy are used to evaluate four modification approaches: rubber alone, lime alone, rubber with EICP, and rubber with lime. Accordingly, shear strength, cohesion, and internal friction angle are quantified. At a vertical normal stress of 100 kPa and above, samples modified with rubber and lime (7–9% lime and 6–8% rubber) achieve peak shear strength values of 200–203 kPa, representing an 86.4% increase compared to rubber alone. Microscopic analysis reveals that calcium silicate hydrate gel effectively anchored rubber particles, forming a composite structure with a rigid skeleton and elastic buffer. In comparison, the rubber and EICP group (10% rubber) shows a substantial increase in internal friction angle (24.25°) but only a modest improvement in cohesion (16.5%), which is due to limited continuity in the calcium carbonate bonding network. It should be noted that the performance of EICP-based modification is constrained by curing efficiency and reaction continuity, which may affect its scalability in conventional engineering applications. Overall, the combination of rubber and lime provided an optimal balance of strength, ductility, and construction efficiency. Meanwhile, the rubber and EICP method demonstrates notable advantages in environmental compatibility and long-term durability, making it suitable for ecologically sensitive applications. The results offer a framework for loess stabilization based on performance adaptation and resource recycling, supporting sustainable use of waste rubber in geotechnical engineering. Full article

The problem of textile industry waste has become increasingly relevant. Recycling clothing industry waste to build acoustic panels is one of the most popular and relatively inexpensive ways to use clothing industry waste. We see a lack of information on the acoustic properties of panels made from waste from the clothing industry. The aim of this research is to determine the acoustic properties of a wide range of clothing industry waste recycled into acoustic panels. The acoustic panels were made from clothing industry waste, a different composition of textile and paper residues generated during digital printing processes. We see that panels made from square-cut scraps knitted and woven fabrics, and from yarns and fibers have relatively good acoustic properties. The panel made only of paper had good acoustic properties, the production of panels from paper and textile resulted in similar acoustic properties. Analyzing the acoustic properties of the double specimen, it was found that testing the double-layered panels, the insertion loss is better; by tripling the samples, it was found that although the acoustic properties improved, they were only marginal. Cellulose fiber boards were characterized by significantly higher air resistance. The air resistance of the boards made from fabric scraps was lower. Full article

This study investigates a metakaolin-based geopolymer matrix in which two types of non-recyclable mirror glass waste (MGW) were used as alternative aggregates. The composition, properties and contents of MGW materials as well as their impact on the structure and performance of the geopolymer composites (MGW-Gs) have been characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), and Fourier transform infrared spectroscopy (FTIR). Mechanical properties, porosity and thermal conductivity have been evaluated, and compared with silica sand reference composites. The results show that MGW-based composites achieved flexural strengths of 3.9–5.7 MPa and compressive strengths of 60–70 MPa, which are lower than those of sand-based materials (8–11 MPa and up to 93.5 MPa, respectively) but remain adequate performance for applications with moderate load. FTIR analysis has indicated that the incorporation of MGW does not adversely affect the geopolymer network. All composites display similar porosity (approximately 18–22%) and water absorption (12–14%), while MGW incorporation has improved their thermal stability and significantly reduced their thermal conductivity to values below 0.53 W·m⁻¹·K⁻¹, compared with up to 1.09 W·m⁻¹·K⁻¹ for sand-based composites, emphasizing their insulation potential and sustainability benefits. The findings indicate that MGW aggregates can influence the microstructure, mechanical performance, and thermal properties of geopolymer composites, suggesting their potential use in specific construction applications. Full article

With rising efforts to enable a circularity of valuable resources of lithium-ion batteries, a growing number of recycling companies in Europe are expanding their capacities and developing new recycling technologies. The European Union (EU) has set a benchmark for battery recycling by publishing recycling targets. These targets require precise mass determination of the individual battery components, making disassembly of the battery mandatory for characterization. The paper puts forth a semi-automated disassembly procedure for determining the composition of the components at the module and cell levels across a range of designs. Our analysis incorporates the introduction of TGA as a novel, direct method for determining the cathode active material with an accuracy above 99%. This approach is intended to define the recycling input for all extant recycling routes by providing quantitative experimental results with statistical significance. The results indicate a black mass proportion of 61.6% at the module level and 53–74% at the cell level. Additionally, there are significant differences in value creation, ranging from 0.80 to 1.81 USD kg⁻¹ black mass, depending on the cell chemistry. The procedure can be used for EoL and scrap material, and enables greater transparency and comparability in battery recycling, opening up new perspectives for the resource-efficient and targeted use of various recycling technologies. Full article

The oxidation of chlorophenolic compounds is essential for converting these persistent and toxic pollutants into less harmful products, thereby reducing their environmental and health impacts. In this study, a p-coumaric acid ester derivative was employed as the starting material to synthesize the corresponding phthalonitrile precursor (EnCA-CN), followed by the preparation of non-peripherally substituted Co(II) and Cu(II) phthalocyanine complexes (EnCA-Copc and EnCA-CuPc). These complexes were subsequently characterized using a range of spectroscopic techniques and designed to engage in π–π interactions with graphitic carbon nitride to form efficient photocatalytic materials. The structures of the two effective catalysts were characterized by FT-IR, SEM, and XRD analyses, after which their photocatalytic performance and recyclability in the degradation of 2-chlorophenol, 2,3-dichlorophenol, and 2,3,6-trimethylphenol were evaluated. The optimum catalyst loading for the MPc/g-C₃N₄ composites was determined to be 0.5 g/L, yielding the highest photocatalytic efficiency. The EnCA-CoPc/g-C₃N₄ catalyst achieved 90.8% product selectivity and 82.6% conversion in the oxidation of 2-chlorophenol, whereas the EnCA-CuPc/g-C₃N₄ catalyst exhibited approximately 80.0% pollutant removal. The degradation efficiencies followed the order 2-CP > 2,3-DCP > 2,3,6-TCP, with benzoquinone derivatives identified as the major oxidation products. In recyclability tests, both catalysts retained more than 50% of their activity after five cycles; EnCA-CoPc/g-C₃N₄ maintained 68% conversion in the 5th cycle, while EnCA-CuPc/g-C₃N₄ retained 60% conversion in the 4th cycle. Full article

This study examined rubberized concrete-filled steel tubular (RuCFST) columns as a sustainable option for structural applications. Eccentric compression tests were conducted on eight groups of square specimens, with two identical specimens per group. The main parameters were slenderness ratio, load eccentricity, and rubber replacement level for fine aggregates. Full load–displacement and load-strain curves were obtained. Results indicated that rubber particles inhibit concrete cracking. Increasing slenderness ratio reduces bearing capacity, with ductility peaking at moderate slenderness. Eccentricity significantly degrades bearing capacity and stiffness. A higher rubber replacement ratio lowers capacity but optimizes particle interaction and distribution, leading to stiffness recovery at higher ratios. Filling the steel tube with core concrete transforms it into a composite member, substantially improving load-bearing performance. Comparisons with seven design standards (including GB 50936-2014, CECS 254:2012, Eurocode 4, and AISC 360-16) revealed that Eurocode 4 provided the most reliable predictions, whereas AISC was the most cautious. None of the codes accounts for the effect of rubber on core concrete behavior. These results offer useful guidance for incorporating recycled rubber particles into composite columns to promote sustainable building practices. Full article

Anaerobic digestion of straw is a crucial method for agricultural waste valorization, yet its efficiency is limited by complex factors. This study employed machine learning to predict methane yield and optimize process parameters in biochar-amended straw digestion. A comprehensive dataset integrating experimental and literature data (100 samples, 15 input variables) was constructed, incorporating operational conditions, straw characteristics, and biochar properties (e.g., dosage, particle size, specific surface area, and elemental composition). Prediction models were developed using Random Forest (RF), XGBoost, and Support Vector Machine (SVM). Results indicated that the RF model achieved the best predictive accuracy, with an R² of 0.81 and RMSE of 36.9, significantly surpassing other models. Feature importance analysis identified feeding load, biochar dosage, and biochar carbon content (C%) as the key governing factors, collectively accounting for 65.7% of the total contribution. The model-predicted optimal ranges for practical operation were 15–30 g for feeding load and 5–20 g/L for biochar dosage. This study provides data-driven validation of biochar’s enhancement mechanisms and demonstrates the utility of RF in predicting and optimizing anaerobic digestion performance, offering critical support for sustainable agricultural waste recycling and clean energy generation. Full article

The study examines how crushed and sieved concrete rubble—recycled concrete fines (RCF) and the ways of their reactivity activation—affect processing, mix design, and properties of cement-based concrete. Based on the relationship to mass loss during crushing, the compressive strength of the concrete fines processed from rubble was initially determined. The morphology of the particles as well as the chemical and mineralogical composition of RCF were ascertained using XRD, SEM, and EDS characterization tests. Certain RCF surface area (fineness) and type of treatment are associated with specific pozzolanic activity of RCF. Using the approaches of factorial experimental design, tests were planned by varying six factors: RCF specific surface area, RCF content, thermal treatment temperature of RCF, cement content, superplasticizer dosage, and hardening accelerator (Na₂SiF₆) content in concrete containing RCF. Statistical processing of the research results data provided adequate polynomial regression models for the water demand of the concrete and the compressive strength of hardened concrete at 7 and 28 days. The models were quantitatively analyzed to evaluate the influence of the studied factors on the output parameters and to rank them according to their impact. The greatest increase in water demand was attributed to cement content change, in particular above 400 kg/m³, and to RCF content. It was established that the addition of a superplasticizer compensated for additional water demand and the reduction in compressive strength caused by partial replacement of cement with RCF. Increasing the specific surface area of RCF up to a specific surface area of 250 m²/kg improved compressive strength but further grinding caused strength reduction due to increased water demand. The positive effect of the superplasticizer on RCF-modified concrete strength was enhanced by the introduction of a chemical activator (hardening accelerator) and thermal treatment of RCF. The obtained models of water demand and compressive strength of concrete with RCF can be applied for the optimization of the mix design. This paper proposes a method of mix design and provides an example of calculation. Full article