Search Results (3,440)

Along with the growth in the production of metallurgical grade silicon and high-silicon ferrous alloys, there is a significant increase in the formation of microsilica, which is an ultra-fine technogenic waste. The direct application of microsilica in ore-thermal furnaces is hindered by low bulk density, poor gas permeability, and high dusting. This paper explores the thermophysical and microstructure properties of briquettes based on microsilica, which includes various types of carbonaceous reducing agents such as semi-coke and coal. For manufacturing, the liquid glass was used as the inorganic binder for the preparation of microsilica briquettes. The best variants were chosen based on strength tests carried out during preliminary studies. In the laboratory tests, the stability of the briquettes at elevated temperatures was evaluated. Samples were heated to 1000–1500 °C and subjected to impact testing. Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) was used to investigate the microstructure and local elemental distribution. It was revealed that the calcinated briquettes of the microsilica–semi-coke mixture have better thermal stability compared to the samples with coal and withstand the temperature range up to 1500 °C. The microstructure of the briquette from the microsilica-semi-coke mixture is characterized by the formation of a more uniform silicate matrix with the presence of a homogeneously distributed carbonaceous component. Coal-based samples show higher heterogeneity and porosity. Therefore, it can be stated that the selection of carbonaceous reductants is one of the key factors influencing the thermal stability of microsilica briquettes. Full article

Biochar (BC)-activated peracetic acid (PAA)-based advanced oxidation processes (AOPs) were increasingly considered as cost-efficient and eco-friendly water treatment technologies for the removal of organic pollutants. However, the specific role of intrinsic carbon, nitrogen species and structure properties played in activation mechanism is still vague. In this study, the waste tea residues-based biochar (WTBC) was prepared by thermal carbonization and applied to activate PAA for the degradation of bisphenol A (BPA). The product carbonized at 800 °C (WTBC800) possessed larger specific surface area (342.57 m²/g), more abundant porous structure and massive defects state (I_D/I_G = 3.53), and exhibited a superior activation performance with 83.7% BPA removal within 120 min. Adsorption and non-radical oxidation pathways [e.g., the mediated electron transfer process (ETP) and singlet oxygen (¹O₂) generation] were evidenced to play the dominant roles in the BPA degradation through the formation of metastable complex WTBC-PAA*. The graphitic carbon, functional nitrogen species, defects structure and persistent free radicals (PFRs) in WTBC were proposed to contribute to the activation of PAA. Overall, relatively higher dosages of WTBC (0–0.5 g/L) and PAA (0–1.5 mM) facilitated the BPA degradation. The solution pH and water matrix (e.g., Cl⁻, NO₃⁻, HCO₃⁻ and SO₄²⁻) presented a negligible effect on the BPA degradation in WTBC/PAA system. This study not only proposes a sustainable approach for organic pollutants removal in wastewater, but also promotes the resource re-utilization of agricultural waste. Full article

The increasing amount of untreated electronic waste, particularly in the telecommunications sector, is having a negative impact on the environment, not only by increasing the production of greenhouse gases, but also by reducing the availability of resources such as metals. At the same time, these metals are increasingly in demand to meet the manufacturing needs of new technologies. One solution is to recover metals by recycling end-of-life electronic boards. However, current processes are often implemented by large companies but are not suitable for small organizations or those with fewer resources, thus limiting their participation in local electronic waste management. Based on laboratory-scale analyses, this project compares the metal concentration results of three pre-treatments that could be suitable for smaller organizations: magnetic separation, chemical pre-treatment with sodium hydroxide, and centrifugation. The proposed preparation step, after the shredding of telecom electronic boards down to a particle diameter of less than 1 mm, is two-stage centrifugation. This pre-treatment enables metals to be concentrated efficiently and safely prior to hydrometallurgical processing. Full article

Sustainable valorization of biomass through hydrothermal carbonization (HTC) represents an environmentally benign method for producing carbon materials for water treatment applications. This research aims to optimize the production of hydrochar from waste food by focusing on parameter optimization, physicochemical characterization, and the capacity of hydrochar to act as an adsorbent for the removal of the copper (II) ion from polluted water. A design of experiments using the RSM approach was employed to evaluate and optimize the influence of carbonization temperature, ranging from 180 to 250 °C, with a residence time of 2–5 h. The predictive ability of the MINITAB-generated model was close to accurate, as demonstrated by the design application for process simulation. The maximum % hydrochar yield was 72.65% for the experimental yield and 71.53% for the predicted yield, both obtained from a sample carbonized at 166 °C for 3.5 h. Batch adsorption experiments were conducted to assess the hydrochar’s ability to remove Cu²⁺ from aqueous solutions, and the Langmuir and the Freundlich isotherms were fitted at different pH levels. A comprehensive characterization of the produced hydrochar was conducted using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM-EDS). The results revealed significant modifications in surface morphology, pore development, and the presence of oxygen-containing functional groups. Based on the findings in this report, it is safe to conclude that hydrochar derived from food waste could serve as a potential adsorbent. Overall, the study demonstrates that sustainable hydrochar production from biomass can simultaneously address waste management challenges and provide an efficient solution for heavy metal removal, thereby advancing circular bioeconomy and environmental protection. Full article

This study investigates the synthesis and kinetic behavior of a magnetic biochar derived from avocado seed biomass for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions. Magnetite (Fe₃O₄) was synthesized through different routes, including nitrogen-assisted coprecipitation, redox-controlled coprecipitation, polyol, sol–gel, and sonochemical methods, to evaluate their structural properties and iron incorporation efficiency. Based on compositional and crystallographic analyses, the coprecipitation under an inert atmosphere exhibited improved phase purity and higher Fe₃O₄ content, which was selected for in situ incorporation onto biochar produced by pyrolysis at 450 °C. The resulting magnetic material and composite were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS), confirming the suitability of the synthesis method and the successful deposition of magnetite onto the porous carbon matrix while preserving its structural integrity. Batch adsorption experiments were conducted at pH 2.0 to evaluate the effect of adsorbent dose and initial Cr(VI) concentration. The adsorption process reached equilibrium within 120 min and was better described by the pseudo-second-order kinetic model (R² ≥ 0.98), suggesting that chemisorption governs the rate-controlling step, with diffusion phenomena contributing but not dominating the overall mechanism. The maximum adsorption capacity predicted by the kinetic model reached 42.49 mg g⁻¹ at an initial concentration of 100 mg L⁻¹. The results demonstrate that avocado-seed-derived magnetic biochar represents a sustainable and effective material for chromium-contaminated water treatment, integrating agro-industrial waste valorization with enhanced adsorption performance and magnetic separability. Full article

Сommercial TiO₂ ceramic membranes were modified using a slip-casting method with coal fly ash (CFA) obtained from a thermal power plant, Almaty, Kazakhstan. The aim was to enhance membrane surface properties for improved oil-in-water emulsion separation while maintaining structural integrity. Suspension of CFA, stabilized with N-dodecylpyridinium chloride (DPC) and polyvinyl alcohol (PVA), was applied as a coating layer on the TiO₂ surface and subsequently sintered under controlled conditions. The resulting membranes were characterized by SEM-EDX (scanning electron microscopy with energy-dispersive X-ray), Raman spectroscopy, contact angle measurements, and zeta potential analysis. The modified membranes exhibited increased hydrophilicity, as indicated by a reduction in water contact angle (WCA) from 43.6 ± 2° to approximately 0°, and a decrease in the underoil contact angle of water (UOCA) from 147.6 ± 2° to 87 ± 2°. Raman spectroscopy confirmed that the TiO₂ structure remained predominantly rutile, with no additional crystalline phases detected from CFA. Despite the improved wettability, pure water and oil-in-water emulsion fluxes decreased slightly, while filtrates displayed smaller oil droplet sizes, indicating enhanced emulsion stability after passage through the modified surface. These findings demonstrate that CFA-modified TiO₂ membranes can serve as a sustainable and cost-effective approach for treating emulsified wastewater, utilizing industrial waste to improve performance without compromising mechanical robustness. Full article

As critical conduits for pollutant enrichment and transformation, lake inlets govern the biogeochemical cycling of emerging contaminants. This study investigated the occurrence, spatiotemporal heterogeneity, and source–sink dynamics of 15 organophosphate esters (OPEs) in the major inflowing rivers of Poyang Lake, China. Using UPLC–MS/MS, positive matrix factorization (PMF), and risk quotient (RQ) modeling, we identified the mechanisms driving pollutant distribution across three hydrological periods. Alkyl-OPEs (58.19%) and chlorinated OPEs (40.42%) dominated the contaminant burden, with TCPP and TEP identified as the primary congeners. Concentrations exhibited a distinct seasonal gradient, with higher levels during the dry season and lower levels during the wet season, controlled by seasonal hydrological dilution versus evaporative and stagnant accumulation. PMF indicated that source contributions shifted with hydrology: intense wet-season precipitation flushed non-point sources from waste and electronic products (45.1%), while reduced dry-season flow concentrated mixed inputs from agricultural runoff and ship traffic (50.7%). Ecological risk assessment identified EHDPP, TCrP, and TCPP as high-risk contaminants (RQ ≥ 1.0), posing direct threats to aquatic population. These findings highlight the need for adaptive, season-specific management of emerging contaminants at the river–lake interface, specifically by implementing enhanced interception of surface runoff during the wet season and enforcing stringent regulations on localized shipping emissions during the dry season to protect freshwater ecosystems. Full article

Materials derived from renewable and recycled resources offer a promising route toward more sustainable thermoset composites. In this study, waste poly(ethylene terephthalate) (PET) was depolymerized by glycolysis with propylene glycol to obtain a glycolysate, and subsequently polycondensed with biobased propylene glycol, maleic anhydride, and trimethylolpropane diallyl ether to synthesize biobased UV-curable unsaturated polyester resin (UV-bUPR). The composites were prepared with acryloyl-modified Kraft lignin (K_rL-A) as a reactive bio-filler using a dual-curing approach, in which rapid UV curing was followed by thermal/redox post-curing to improve conversion and network homogeneity. The structure of the synthesized resin and composites was confirmed by FTIR and NMR spectroscopy. Mechanical properties were evaluated by tensile testing and hardness measurements, while morphology and fracture behavior were analyzed by scanning electron microscopy. The unmodified lignin decreased tensile performance due to limited compatibility with the polyester matrix and the formation of interfacial defects and agglomerates. In contrast, K_rL-A exhibited improved dispersion and stronger filler–matrix interactions, resulting in superior mechanical performance. The most pronounced effect of lignin modification was observed at 15 wt.% filler loading, where the tensile strength reached 27.83 MPa, compared with 13.91 MPa for the corresponding unmodified system. The developed composites also showed improved sustainability, assessed through the E-factor, due to the combined use of recycled PET and renewable lignin. Full article

Optimizing chitosan recovery from shrimp shells is one of the most effective measures in shrimp waste management. Incorporating machine learning-based models will significantly impact the optimization process. This research aimed to evaluate the optimization of chitosan extraction from Litopenaeus vannamei shrimp shells using deproteinization and exploratory machine learning-based similarity model approaches. Chitosan extraction from shrimp shells was optimized using a deproteinization method, where various NaOH concentrations (1, 2, 3, 4, 5, and 10%) were applied at room temperature (RT) and 50 ± 2 °C, while maintaining controlled conditions for demineralization and deacetylation. The chitosan products were characterized by ash content, moisture, yield percentage, deproteinization efficiency, FTIR, deacetylation degree (DD), XRD, crystallinity index (CI%), and scanning electron microscopy (SEM). A machine learning random forest regressor model was developed to evaluate the similarities between the laboratory-synthesized and commercial chitosan (CC) samples. The results confirmed the formation of chitosan with semi-complete deacetylation (DD% from 98.84 ± 0.1% to 99.27 ± 0.004%). Deproteinization efficacy was in the range of 93.39 ± 0.083% to 97.0 ± 0.31%. XRD and SEM analyses demonstrated that commercial chitosan (CC) possessed a predominately amorphous structure, whereas the isolated chitosan samples exhibited low crystallinity, with increased amorphism at higher NaOH concentrations and temperatures. The machine learning-based similarity model indicated that Ch3 and Ch4 samples exhibited the highest resemblance degrees to commercial chitosan, while the S1 sample showed the lowest similarity. However, most of the recovered chitosan samples showed low similarity to commercial chitosan; they retained their higher degree of deacetylation (DD%), structural integrity, and quality parameters, indicating the success of the deproteinization route in enhancing chitosan production. Full article

Certain clayey soils are susceptible to swelling and shrinkage due to moisture variations, which can lead to ground deformation and structural damage. Although traditional stabilization methods using lime and cement are effective, they involve high energy consumption and significant CO₂ emissions. In response to sustainability concerns, this study investigates the potential of in situ geopolymer stabilization of clay soils using industrial by-products as eco-friendly binders. Experimental studies were conducted on clay specimens stabilized with geopolymer binders produced from fly ash and waste brick powder activated by alkaline solutions. The selected clay exhibited stiff to very stiff behavior and was used as a reference material to ensure reliable evaluation without the influence of severe initial degradation. Reference samples with identical water content but without alkaline activation were also prepared. The primary objective was to assess geopolymers as a sustainable alternative to conventional binders, focusing on moisture sensitivity and long-term mechanical performance. Laboratory strength tests demonstrated that geopolymer-treated specimens exhibited significantly higher strength compared to untreated samples, indicating substantial improvement in engineering properties. Furthermore, Scanning Electron Microscopy (SEM) analyses revealed that the combination of dual activators (NS+NH) and thermal curing at 85 °C transformed the weak clay matrix into a dense, fibrous geopolymer network. However, the high curing temperature was primarily used to study the reaction mechanisms; the practical applicability of the method should be evaluated based on results obtained at ambient temperature. This structure enhanced particle bonding and mechanical interlocking by filling voids within the matrix. Overall, the findings confirm that geopolymer stabilization using industrial waste materials is an effective and environmentally sustainable alternative to conventional soil stabilization techniques, contributing to reduced carbon emissions in geotechnical engineering. Full article

The purpose of this work was to synthesize and study catalytic systems based on a carbon-containing support obtained from coke fines from the Shubarkol deposit as a waste product of the coal industry for the processing of phenolic compounds. Based on the obtained carbon sorbent, mono- and binary catalysts with active phases of transition metal oxides (Fe, Co, Ni) were synthesized by wet impregnation, followed by heat treatment at 500–700 °C, as well as the aluminum oxide compositions. The surface morphology and elemental composition of the samples were studied by scanning electron microscopy (SEM) with energy dispersion analysis and elemental mapping (EDS mapping), and the content of active phases was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The catalytic activity was studied in phenol hydrogenation reactions. The CoO/C catalyst demonstrated the greatest activity, providing a 62.36% benzene yield during phenol hydrogenation. The catalytic activity of the CoO/C catalyst has also been studied in the hydrogenation reactions of structurally and functionally more complex compounds, pyrocatechol and resorcinol. The yield of benzene was 63.16% in the hydrogenation of pyrocatechol and 48.64% in the hydrogenation of resorcinol. It was found that the CoO/C catalyst exhibits the highest efficiency at a temperature of 420 °C, a pressure of 6–6.5 MPa and a reaction duration of 120 min. The results obtained make it possible to evaluate the prospects of using a carbon sorbent obtained from coke fines from the Shubarkol deposit as a support for CoO as part of an active and stable catalytic system designed for deep processing of phenolic compounds. Full article

The disposal of waste tyres presents a significant environmental challenge, necessitating sustainable, high-value recycling solutions. This study explores the incorporation of waste tyre metal fibre (WTMF) into hot mix asphalt (HMA) to enhance mechanical performance while reducing its electrical resistivity as well as the landfill burden. The primary goal of this research is to apply response surface methodology (RSM) to experimental data for modelling and optimizing WTMF-modified HMA mixes by capturing the coupled effects of fibre reinforcement and binder content on mechanical and functional performance. The microstructural characteristics of WTMF were examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). WTMF-modified mixes containing five WTMF dosages (from 0% to 1.50%) and bitumen contents from 4% to 6% were prepared and tested in the laboratory. The resulting dataset was used for RSM modelling, with WTMF and bitumen contents as input factors and Marshall stability, flow, porosity, and electrical resistivity as response variables. The central composite design (CCD) technique was employed to quantify interaction effects and to identify statistically significant trends. The developed models were validated using statistical indicators, and optimal mixture compositions were determined and experimentally verified. Microstructural analysis revealed WTMF’s irregular, rough surface with microcracks and pits, aiding crack-bridging and stress transfer. RSM results indicated 0.71% WTMF and 5.1% bitumen as an optimal combination of factors. Furthermore, high R² (>0.80) and adequate precision (>4.0) values from analysis of variance (ANOVA) underscore the significance of the proposed models, revealing a robust correlation between experimental and predicted data. This study demonstrated WTMF’s potential to be used in conventional HMA mixes, offering a sustainable recycling pathway for waste tyres. Full article

This study proposes a sustainable, integrated biorefinery approach to valorize mussel shell waste into high-value products, including chitin, chitosan, and calcium formate. Formic acid was employed as an effective demineralizing agent, enabling not only efficient mineral removal but also the direct conversion of the demineralization effluent into value-added calcium formate. The sequential extraction processes, demineralization, deproteinization, and decolorization, successfully yielded purified chitin (PCH), which was subsequently deacetylated to produce chitosan (CTS) with a degree of deacetylation of 85% and a molecular weight of 75 kDa. The physicochemical properties of all products were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). FTIR and XRD analyses confirmed the successful extraction of chitin and chitosan, demonstrating the feasibility of mussel shells as an alternative biopolymer source. In parallel, calcium formate (CCF) was obtained from the demineralization effluent with a yield of 94.19%, and its formation was verified by FTIR and XRD. Elemental analysis by XRF exhibited 98.3% CaO with minimal non-toxic impurities. The TGA/DTG profiles of CCF exhibited a well-defined two-step thermal decomposition, confirming its anhydrous form. Overall, this environmentally benign process enables the simultaneous production of multiple value-added products while significantly improving resource utilization and reducing waste generation. The proposed integrated biorefinery model offers a promising, economically viable pathway for marine biomass valorization, aligned with the Bio-Circular-Green (BCG) economy concept. Full article

This study investigates the development of sustainable composite materials using recycled low-density polyethylene (rLDPE) and high-density polyethylene (rHDPE) in an 80/20 mass ratio, incorporating kraft lignin as a bio-derived additive and polyethylene-graft-maleic anhydride (PE-g-MA) as a compatibilizer. Reactive melt mixing was employed to produce composites with varying lignin loadings (1, 3, 5, and 10 wt%). The structural, thermal, and mechanical properties and segmental dynamics of the materials were thoroughly examined using differential scanning calorimetry (DSC), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS), tensile testing, scanning electron microscopy (SEM), and dielectric relaxation spectroscopy (DRS). The incorporation of lignin exhibited minimal disruption to the polymeric thermal transitions, while it boosted thermal stability, as confirmed by the TGA curves. According to the segmental dynamics findings, the glass transition temperature of the polymeric blend (−35 °C) was increased systematically with the addition of lignin by ~1–20 K. Tensile tests showed that the 1 wt% additive ratio demonstrated the optimal balance of strength and ductility. Morphological observations supported these findings, revealing uniform dispersion at low additive ratio and increased agglomeration at higher ratios. Based on its superior performance, the composite containing 1 wt% lignin was successfully extruded into filament suitable for 3D-printing. This study highlights the synergy of bio-based additives and recycled polymers in engineering high-performance materials, promoting circular economy principles and reduced environmental footprint through upcycling post-consumer waste into functional, valuable products. Full article

This study evaluates the performance of foamed geopolymer concrete (FGC) incorporating rigid polyurethane (PU) waste as a partial sand replacement and aluminum powder (AP, 1%) as a foaming agent. The mixtures were based on metakaolin, fly ash, and silica fume. Fresh and hardened properties were assessed, including workability, setting time, density, compressive strength, flexural strength, splitting tensile strength, elastic modulus, water absorption, porosity, gas permeability, and chloride ion penetration. Microstructural characteristics were examined using scanning electron microscopy (SEM). The results show that moderate PU incorporation significantly enhances mechanical performance. The optimal mixture (PU30) achieved a compressive strength of 47.25 MPa at 180 days, representing a 15.6% increase compared to the control. Flexural and splitting tensile strengths improved by 19.9% and 16.7%, respectively, while the elastic modulus increased by 33.8% to 0.95 GPa. These improvements are attributed to enhanced particle packing and more efficient stress transfer within the matrix. In contrast, higher PU contents (>30%) reduced mechanical performance due to increased total porosity and weakened interfacial bonding. Durability-related properties indicated that mixtures PU20–PU30 exhibited reduced permeability and optimized pore structure, characterized by lower pore connectivity. SEM observations confirmed a denser matrix with uniformly distributed pores at optimal PU levels. Additionally, the integration of Random Forest regression with GLCM-based texture analysis demonstrated strong capability in predicting mechanical properties from SEM images. Overall, the combined use of PU waste and AP enables the production of lightweight, structurally efficient, and sustainable FGC with improved mechanical and durability performance. Full article