Search Results (452)

Finding cost-effective and eco-friendly ways to remove toxic heavy metals from wastewater remains a critical challenge for industrial sustainability. This study presents a comparative performance matrix of coal fly ash (CFA) and bone charcoal (BC) for the high-capacity remediation of Cd(II) and Pb(II) ions. This work establishes a direct cross-matrix comparison between a heterogeneous aluminosilicate phase (CFA) and a uniform calcium-phosphate structure (BC) under identical systemic boundaries. SEM/EDS, FT-IR, and complementary TG/DTG/DTA screenings confirmed that distinct material-specific functional frameworks drive a predominantly physical mechanism governed by electrostatic and van der Waals interactions. Equilibrium data fitted the non-linear Langmuir model well (R² > 0.99 at 20 °C). BC proved to be significantly more effective, achieving maximum sorption capacities (q_max of 397.55 mg/g for Pb(II) and 325.09 mg/g for Cd(II), outperforming CFA (118.22 and 105.59 mg/g, respectively). Sorption capacities decreased with temperature up to 80 °C, confirming the exothermic nature of the process, which was further substantiated by negative enthalpy values (∆H⁰ = −7.27 to −14.19 kJ/mol). Thermodynamic parameters indicated a spontaneous process (∆G⁰ < 0, −9.55 to −19.33 kJ/mol) with positive entropy changes (∆S⁰ = 5.82 to 39.09 J/(mol·K)). Adsorption kinetics followed the pseudo-second-order model, with intraparticle diffusion acting as a key rate-limiting step. Regardless of the adsorbent, Pb(II) ions were immobilized faster and more efficiently than Cd(II) due to a smaller hydration radius. In conclusion, both industrial by-products represent promising, sustainable options for heavy metal wastewater treatment, with BC demonstrating superior performance. Full article

Globally, large quantities of discarded shells, including scallops and surf clams, are often accumulated at disposal sites, causing environmental degradation. Calcium carbonate (CaCO₃) in seashells predominantly exists in polymorphic forms, such as aragonite and calcite, and undergoes phase transformation upon thermal treatment. This study investigates the thermal evolution of scallops and surf clam shells at various calcination temperatures to characterize changes in crystalline structure, pore morphology, and to review their potential as partial cement replacement materials. The seashells were mechanically ground into fine powder and subsequently calcined at 650 °C, 750 °C, and 850 °C for 7 h. The CaCO₃ transformation was comprehensively characterized using solid-state ¹³C NMR, XRD, TG-DTA, and SEM to resolve carbonate speciation, phase transitions, decomposition thermodynamics, and microstructural evolution. The solid-state ¹³C NMR was employed to analyze the local chemical environments of carbonate species and to provide additional spectroscopic evidence supporting the phase identification obtained from XRD and TG-DTA. Furthermore, XRD, TG-DTA, and SEM analyses consistently confirmed the phase transformations and associated changes in pore structure and crystallinity induced by calcination. These findings suggest that solid-state ¹³C NMR can be a useful technique for tracking CaCO₃ decomposition, while calcination may enhance the potential of seashell biowaste as a sustainable cementitious material. Full article

Copper smelter slag represents a significant secondary resource of critical metals, while flotation tailings serve as an abundant sulfur-bearing waste stream. This study investigated a waste-on-waste sulfation roasting approach for the selective recovery of Cu, Ni, and Co from fayalite copper smelter slag using flotation tailings as an in situ sulfur source and sodium metabisulfite (SMBS, Na₂S₂O₅) as a sulfation promoter. The effects of roasting temperature, roasting time, slag-to-tailings ratio, SMBS dosage, and water-leaching conditions were systematically evaluated. Under the optimum conditions of a slag-to-tailings ratio of 1:1, roasting at 600 °C for 4 h with 30 wt% SMBS addition, followed by water leaching at 25 °C for 2 h, extraction efficiencies of 85.5% Cu, 81.6% Ni, and 87.1% Co were achieved, while Fe dissolution remained below 5%, demonstrating high selectivity. Phase and microstructural analyses by XRD, FTIR, SEM, and TG–DTA revealed that pyrite oxidation generated sulfur oxides required for metal sulfation, whereas SMBS promoted sulfur release and sulfate stabilization, enhancing sulfation efficiency. Thermodynamic analysis further confirmed the feasibility of sulfide oxidation and sulfate formation within the investigated temperature range. The results demonstrate that the synergistic use of tailings and SMBS enables efficient low-temperature sulfation roasting of fayalite slag and provides a promising route for the selective recovery of valuable metals from metallurgical waste materials. Full article

This study investigates the thermo-mechanical and microstructural performance of concrete incorporating waste tire rubber (WR) and recycled steel fibers (WS) under elevated temperatures. Four mixtures were prepared: plain concrete (PL), rubber-modified concrete (WR5), and hybrid mixtures containing 0.4% and 0.8% steel fibers (WS0.4WR5 and WS0.8WR5). Specimens were exposed to temperatures of 400 °C, 600 °C, and 800 °C to simulate fire conditions. The results indicate that the incorporation of rubber reduces compressive strength at ambient temperature due to its lower stiffness and weak interfacial bonding. However, the addition of recycled steel fibers significantly improves crack resistance and enhances thermal stability. At 400 °C, the WS0.8WR5 mixture showed a retention rate of 92.9% (absolute strength: 44.32 MPa), compared to 72.2% for plain concrete (absolute strength: 44.11 MPa). Although the hybrid mixture has a lower ambient strength (47.68 MPa vs. 61.07 MPa), its superior retention makes it competitive in fire scenarios. Ultrasonic pulse velocity (UPV) measurements revealed a strong correlation with compressive strength degradation, confirming its effectiveness as a non-destructive indicator of internal damage. Microstructural analyses (SEM, XRD, and TGA-DTA) demonstrated that elevated temperatures lead to dehydration, phase transformation, and increased porosity, while steel fibers help maintain matrix integrity through crack-bridging mechanisms. The findings highlight a synergistic interaction between waste rubber and steel fibers, offering a sustainable and effective approach for improving the fire resistance of concrete. Full article

This paper reports new results on the synthesis and comparative characterization of cellulose nitrates (CNs) derived from Miscanthus × giganteus stems and from commercial microcrystalline cellulose (MCC). Miscanthus CNs synthesized by nitration with mixed sulfuric–nitric acids containing 16–20% water exhibit new functional properties: a high solubility in organic solvents (100% in acetone and 97–99% in alcohol–ether solvent) and a high viscosity (17–51 mPa·s), with a nitrogen content of 10.54–12.08 wt%. CNs from Miscanthus × giganteus are similar in nitrogen content and solubility to those from MCC (11.54% and 99%) but have a significantly greater viscosity (3 mPa·s), which is an undoubted advantage and considerably expands their potential application range. The solubility test of CNs synthesized from both sources demonstrated that Miscanthus CNs have a better film-forming ability. SEM analysis revealed a great difference in fiber length, despite the same cylindrical shape and observed aggregation: 1.0–2.0 mm for CNs from Miscanthus versus 40–60 μm for CNs from MCC. IR spectra of CNs from both sources showed the appearance of five new characteristic frequencies (1632–1633, 1273–1274, 823–826, 748, 677–686 cm^–1 for Miscanthus CNs and 1659, 1277, 832, 747, 691 cm^–1 for CNs from MCC), allowing the obtained compounds to be identified as nitric acid esters of cellulose. According to TGA/DTA analysis, the synthesized polymers have similarly high values of the onset temperature of both intense decomposition (197–198 °C) and narrow exothermic peaks (209–211 °C and 212 °C), respectively, indicating their high thermal stability. The combination of high solubility, viscosity, thermal stability and chemical purity of CNs derived from Miscanthus × giganteus stems suggests that strong thin films can be obtained and recommended for use in the manufacture of nitrocellulose membranes. Full article

Rare-earth vanadates constitute an important class of functional materials with potential applications as luminophores, in optoelectronics and catalysis. The research for this work was inspired by the incomplete literature data, including the synthesis, structure and physicochemical properties of europium(III) vanadate(V) with the general formula Eu₅VO₁₀. The primary goal of this work was to supplement the missing data about this compound and identify its potential applications. This compound was synthesized using three methods, including waste-free methods: ceramic, mechanochemical and a modified Pechini method. The obtained Eu₅VO₁₀ was characterized using XRD, DTA–TG, FTIR, UV–Vis–DRS, SEM and gas pycnometry. It was settled that Eu₅VO₁₀ crystallizes in the monoclinic system and is thermally stable up to a temperature of approximately 1310 °C, above which it decomposes in the solid phase. Estimated energy gap (E_g) values ranged from ~3.21 eV to ~3.53 eV depending on the synthesis method used, allowing Eu₅VO₁₀ to be classified as a wide-bandgap electrical semiconductor. The results also showed that the synthesis method affects the crystallite size of the synthesized compound. The development of synthesis methods and characterization of Eu₅VO₁₀ expands our understanding of rare-earth vanadates and their potential applications as functional materials. Full article

Phosphate tailings (PTs), a solid waste generated from phosphate flotation, are a low-grade phosphate resource rich in quartz and dolomite. Their long-term accumulation leads to both resource loss and environmental risks, making valorization increasingly important for the sustainable development of the phosphorus chemical industry. In this study, calcareous–magnesian PTs were used as raw materials, and selective hydrothermal leaching with weakly acidic AlCl₃ solution was employed to separate the dolomite phase and directly construct a Ca-Mg-Al precursor solution for layered double hydroxides (LDHs). The LDHs were subsequently synthesized by co-precipitation and evaluated for phosphate removal from wastewater. The results showed that the precipitation pH markedly affected the phase composition and platelet morphology of the LDHs, while appropriate aging conditions further improved their adsorption performance. Under the optimal conditions of pH 12, aging at 40 °C for 2 h, the obtained LDHs exhibited the best phosphate uptake. Adsorption kinetics followed the pseudo-second-order model, and the maximum adsorption capacity calculated from the Langmuir model reached 38.61 mg-P/g. Characterization by XRD, FTIR, TG-DTA, point of zero charge, and XPS indicated that phosphate removal was dominated by surface complexation, accompanied by anion exchange, ionic precipitation, and electrostatic attraction. Full article

The copolymerization of biologically active N-(carboxyphenyl)maleimides with styrene was systematically investigated to elucidate the effect of positional isomerism (ortho-, meta-, and para-) on monomer reactivity and copolymer properties. Reactivity ratios (r₁, r₂) were determined using the Fineman–Ross method, and Q–e parameters were evaluated within the Alfrey–Price framework, revealing distinct electronic effects governing copolymerization behavior. Increasing the maleimide fraction in the feed resulted in decreased copolymer yield, intrinsic viscosity, molecular weight, and glass transition temperature, while all copolymers remained styrene-rich, indicating preferential styrene propagation. Comprehensive structural characterization (NMR, FTIR, and UV–Vis) confirmed successful incorporation of both monomer units. Rheological analysis demonstrated a clear viscosity trend (ortho > meta > para), highlighting the influence of substituent position on chain interactions and macromolecular architecture. Thermal analysis (TGA/DTA) showed good thermal stability up to 250–300 °C. Notably, the copolymers exhibited significant antibacterial and antifungal activity, with maximum inhibition observed against Candida albicans. This study establishes a direct correlation between substituent position and structure–property relationships, providing new insights for the rational design of functional styrenic copolymers with potential applications in antimicrobial and biomedical materials. Full article

In the present study, the development of a high-density polyethylene/polylactic acid/titanium dioxide (HDPE–PLA–TiO₂) composite proposed for pellet-based additive manufacturing and the evaluation of its thermal and mechanical behavior are presented and discussed. The study was designed to address the printability limitations of high-HDPE-content systems, particularly extrusion instability and weak interlayer adhesion. PLA was introduced to improve processing stability, while TiO₂ was incorporated as an inorganic filler. The selected formulation allowed the production of filaments, pellets, and 3D-printed specimens. Thermal analysis indicated the absence of significant mass loss below approximately 300 °C under the applied thermogravimetric/differential thermal analysis (TG/DTA) conditions, suggesting that no major mass-loss degradation occurred within the selected processing window. However, this result should be interpreted as macroscopic thermal stability and does not exclude possible molecular-level changes in PLA during processing. Tensile tests indicated strengths of 20–25 MPa for extruded filaments and 7.86–10.36 MPa for printed specimens, with an elastic modulus of approximately 2 GPa. Scanning Electron microscopy equipped with Energy Dispersive X-Ray Spectroscopy (SEM/EDS) observations revealed a heterogeneous fracture morphology with cavities, microcracks, fibrillar structures, and local Ti-rich regions, supporting the influence of morphology and filler distribution on the mechanical response of the printed specimens. The results indicate improved printability, adequate thermal behavior for the selected processing conditions, and moderate but reproducible tensile performance, highlighting the potential of this formulation for pellet-based additive manufacturing applications where processability and rigidity are more relevant than maximum tensile strength. Full article

The high-temperature operating requirements and the issues in the packaging process of wide-bandgap power semiconductors have positioned pressureless sinter-bonding using Ag nanoparticle paste as the most promising die-attach technology. However, under pressureless conditions, where externally applied pressure-driven particle rearrangement is absent, achieving sufficient densification and suppressing residual porosity during short-duration annealing at 250 °C remain significant challenges for conventional single-composition Ag pastes. In this study, a hybrid filler paste composed of Ag nanoparticles and a Ag complex solution was developed to implement an active mass supply strategy, in which additional Ag atoms were directly introduced into interparticle voids through in situ reduction during sinter-bonding. Mono-dispersed Ag nanoparticles with a mean diameter of 75.26 nm were synthesized via H₂O₂-mediated wet-chemical reduction, and the Ag complex solution was prepared using a Ag salt–complexing agent–formic acid system dispersed in an ethylene glycol medium. TG-DTA analysis of the hybrid paste revealed four sequential thermal stages, consisting of solvent evaporation, Ag ion reduction, organic decomposition, and interparticle sintering, accompanied by approximately 16 wt% out-gassing. Based on these results, a three-step temperature profile was designed to initiate sintering after complete out-gassing. When chip/paste/substrate assemblies, pre-dried at 50 °C for 90 s and pre-compressed at 5 MPa for 60 s, were subjected to the three-step profile with a peak temperature of 250 °C, the in situ reduced Ag effectively bridged adjacent nanoparticles and filled fine interparticle voids, leading to pronounced densification of the bond line. As a result, the hybrid paste achieved an average shear strength of 19.1 MPa, exceeding the minimum requirement for sinter-bonding applications. These findings demonstrate that the proposed hybrid filler approach provides an effective pathway for enhancing pressureless Ag sinter-bonding performance. Full article

Poultry is the main reservoir of Campylobacter spp. and most human cases result from consuming undercooked poultry or handling raw meat. In 2022, a total of 55 samples, including neck skin, cecal contents, and processing waters, were collected at two poultry slaughterhouses in Italy and analysed according to ISO 10272-2:2017 at the Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata laboratories. Overall, 51/55 (92.72%) samples tested positive for Campylobacter. Among the isolates, 64.71% were identified as C. coli, and 35.29% as C. jejuni. Phenotypic and genotypic analysis were performed to assess antimicrobial resistance and virulence characteristics. All C. jejuni isolates and 72.72% of C. coli showed resistance to fluoroquinolones. Resistances to tetracycline and carbapenem were observed in 60.78% and 45.09% of isolates, respectively. Genomic analysis confirmed the presence of the tet(O) gene, conferring tetracycline resistance. In addition, OXA-450 and OXA-466 genes, conferring beta-lactam resistance, were detected in 78.43% and 3.92% of isolates. Virulence-associated genes were detected. Specifically, the ciaB gene was found in 50/51 (98.04%) of isolates, whereas jlpA, cdtA, cdtB, and ctdC genes were exclusively identified in C. jejuni strains. The high prevalence of pathogenic and antimicrobial-resistant Campylobacter strains highlights the need for strengthened control measures along the poultry production chain. Full article

To investigate the influence mechanism of Yellow River silt powder on the hydration process, microstructure, and strength development of shotcrete, and to promote the resource utilization of Yellow River sediment, this study systematically investigated the effects of different silt powder replacement levels (0%, 10%, 30%, and 50%) on a cement–accelerator system. A combination of setting time tests, isothermal calorimetry, and mechanical strength measurements was employed, together with microstructural characterization techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), and scanning electron microscopy (SEM). The results indicate that the silt powder content exerts a two-stage effect on the setting behavior of shotcrete. At low replacement levels (0–30%), both initial and final setting times are significantly prolonged, whereas at higher replacement levels (>30%), the setting time is anomalously shortened, approaching that of the reference mixture. The incorporation of silt powder delays the onset of the pre-induction period, prolongs the induction stage, and reduces the cumulative heat release, with the reduction exhibiting a staged trend characterized by gradual, pronounced, and then moderate changes as the replacement level increases. With increasing silt powder content, both compressive strength and splitting tensile strength decrease continuously. At a 50% replacement level, the 28-day compressive strength loss reaches 48.35%, while the splitting tensile strength loss reaches 43.30%, with more pronounced deterioration observed at early ages. The tensile-to-compressive strength ratio increases with silt powder content at early ages, while converging to similar values among all mixtures at later ages. Microstructural analysis indicates that silt powder primarily affects hydration through physical dilution and ion adsorption. At low dosages, nucleation effects slightly promote early hydration, whereas at high dosages, the hydration of calcium silicate phases is inhibited, resulting in reduced C–S–H gel formation and increased porosity. Additionally, AFt morphology transitions from dense prismatic crystals to loosely distributed needle-like structures. This study provides a systematic understanding of the role of silt powder in shotcrete and offers theoretical guidance for mix design optimization and the sustainable utilization of Yellow River sediment. Full article

This study aimed to produce biocarbons from pistachio shells and estimate the effect of physical activation with CO₂ and overheated steam on their physicochemical, thermal, and adsorption properties in relation to methyl orange. Biocarbons were obtained by pyrolysis at 800 °C and subsequently activated under different conditions. From the results, the type of activating agent substantially determined the development of pore structure and surface chemistry. CO₂ activation favored the formation of primarily microporous materials with a very large specific surface area, whereas steam activation led to a more open, hierarchical pore system with a greater pore volume and a larger contribution to external surface area. The most favorable textural properties were found for the samples PM-8-CO₂-3 and PM-8-H₂O-2. The FTIR, Raman, Boehm titration, CHN, SEM-EDS, and TG/DTG/DTA analyses confirmed that activation caused reconstruction of the carbon matrix, modification of the surface functional groups, and a decrease in thermal stability with increasing activation intensity. The adsorption studies proved that the sample PM-8-H₂O-2 exhibited the largest efficiency in methyl orange removal. The adsorption kinetics were best described by the pseudo-second-order model, whereas the equilibrium data were best fitted by the Freundlich model. The adsorption process was spontaneous and exothermic. Full article

This study reports the development of a hierarchically porous material based on natural diatomite, thermally treated diatomite (450 °C), and an activated carbon-modified diatomite composite for saline groundwater treatment in West Kazakhstan, addressing the need for efficient desalination solutions under real environmental conditions. The material was synthesized via sequential thermal activation at 450 °C followed by incorporation of activated carbon, with bentonite used as a binder to improve mechanical stability. Comprehensive physicochemical characterization (SEM, XRD, XRF, BET, DTA, and FTIR) confirmed significant structural and compositional transformations, including silica enrichment, removal of impurities, and the development of a well-defined hierarchical porous network. The specific surface area increased from 8 to 10 m²/g for natural diatomite to 35–40 m²/g for thermally treated diatomite and further to 55–60 m²/g for the activated carbon-modified diatomite composite, accompanied by enhanced pore volume and mesoporosity. Performance evaluation using real groundwater samples demonstrated that thermally treated diatomite (450 °C) improved removal efficiency by approximately 19%, while the activated carbon-modified diatomite composite achieved 35–37% removal of chloride, sulfate, and total dissolved solids under multi-ion competitive conditions. The enhanced adsorption performance is attributed to the synergistic effect of increased surface area, improved pore accessibility, and additional active sites introduced by activated carbon. The adsorption process is governed by ion bridging mediated by multivalent cations, pore filling within the hierarchical pore structure, and surface complexation on silanol and metal–hydroxyl functional groups. Leaching tests confirmed the structural stability of the composite and indicated no significant release of environmentally relevant elements under aqueous conditions. Compared with natural diatomite, the thermally treated and activated carbon-modified materials demonstrate improved adsorption efficiency and stable performance under realistic groundwater conditions. These results highlight their applicability for decentralized water treatment systems in regions affected by saline groundwater contamination. Full article

The study presents a comprehensive report on the kinetic and thermodynamic parameters of carbide crystallization in CrMnFeCoNi, CrMnFeCoNiV_0.5, and CrMnFeCoNiMo_0.5 HEAs. This study considers only carbon resulting from the decomposition of the process control agent, which diffuses and becomes trapped within the HEA structure (0.79–0.91 wt.% C). The crystallization and growth of the carbides were monitored through thermal analysis and thermo-XRD at different temperatures. The activation energy was calculated using the Kissinger and Flynn/Wall/Ozawa methods, and the crystallization kinetics were evaluated using the Avrami–Erofeev model. The results of the XRD analyses and DTA curves of the CrMnFeCoNi, CrMnFeCoNiV_0.5, and CrMnFeCoNiMo_0.5 HEAs showed the following nanocarbide crystallization sequences: M₇C₃→MC→M₃C₂, M₂₃C₆, and MC→M₆C, respectively. The transitions observed in the DTA curves were associated with M₇C₃, M₂₃C₆, and MC phases with activation energies (E_a) of 238–251, 188–203, and 326–341 kJ/mol, respectively. Furthermore, kinetic analyses indicate that the crystallization of M_xC_y-type carbides occurs via nucleation. Full article