Search Results (2,322)

This study investigated the effects of aqueous extracts of orange peel–derived biochar on seed germination and early seedling growth in durum wheat (Triticum durum Desf.) and common buckwheat (Fagopyrum esculentum Moench.). Biochar was produced by pyrolysis of orange peel at temperatures ranging from 250 to 550 °C. Germination assays were conducted under controlled laboratory conditions, and seedling growth parameters were evaluated after six days of cultivation. Untreated orange peel completely inhibited seed germination (0 %) in both species, while biochar produced at 250 °C significantly reduced germination (e.g., the germination index decreased from 54.21 % in the control to 47.2 % in T. durum). In contrast, biochar produced at 350 °C increased germination to >96 % in T. durum and 100 % in F. esculentum, accompanied by enhanced seedling vigor and biomass production. Chemical analyses revealed a pronounced decrease in total phenolic content (from 53.84 to 0.57 mg GAE g⁻¹ DW) and flavonoids (from 90.05 to 1.34 mg QE g⁻¹ DW) with increasing pyrolysis temperature, along with a reduction in antioxidant activity. Common buckwheat exhibited consistently higher tolerance to biochar extracts than durum wheat across all treatments. Overall, the results demonstrate that pyrolysis temperature is a key factor governing the transition from phytotoxic to biostimulatory effects, with optimal performance observed at approximately 350 °C. Full article

The conversion of livestock manure, including poultry waste (PW), into biochar represents a sustainable strategy to recycle nutrients while reducing environmental risks. This study evaluated how pyrolysis temperature regulates physicochemical properties, carbon structure, and nutrient dynamics in biochars produced from PW. Raw PW and biochars generated at 300 and 600 °C were characterized through proximate and elemental analyses, Fourrier Transform Infrared spectroscopy (FTIR), soil nutrient assessment, and germination bioassays. A multivariate approach was used to analyze the experimental data sets. Increasing pyrolysis temperature significantly reduced biochar yield (83.62% to 64.36%), while promoting carbon condensation and mineral enrichment, as indicated by the decline in H/C ratio from 1.02 to 0.22 and the increase in ash content from 41.47% to 56.77%. FTIR analysis revealed a progressive attenuation of O–H and aliphatic C–H functional groups and a relative increase in aromatic structures with increasing temperature, indicating structural reorganization of the carbon matrix. Total concentrations of macro- and micronutrients generally increased with temperature; for example, total Cu increased from 78.62 to 114.17 mg kg⁻¹, while Zn increased from 557.03 to 819.66 mg kg⁻¹ between 300 and 600 °C. In contrast, the bioavailable fractions of Fe, Cu, and Zn determined using the chelating agent DTPA declined, although not significantly (p < 0.05), with increasing pyrolysis temperature. Principal component analysis clearly distinguished raw PW from pyrolyzed materials, confirming pyrolysis temperature as the main factor dictating biochar properties. PW exhibited severe phytotoxicity, which was partially mitigated with increasing pyrolysis temperature. Overall, pyrolysis enhanced carbon stabilization and micronutrient immobilization, highlighting PW-derived biochars as promising soil amendments for improving nutrient management and reducing the environmental risks associated with raw PW application. Full article

This study investigates the ternary co-pyrolysis behavior of Soma lignite (SL), sugar beet pulp (SBP), and hazelnut husk (HH) at four blending ratios (80:10:10, 60:20:20, 40:30:30, and 20:40:40 wt.%) using thermogravimetric analysis under a nitrogen atmosphere. Synergistic interactions were quantified through mass-based ($\Delta W$) and rate-based ($\mathrm{\Psi }$) deviation indices, and the contributions of individual pseudo-components were resolved by Gaussian deconvolution of DTG curves. Among the blends investigated, the 40:30:30 (SL:SBP:HH) composition exhibited the most consistent and intense synergistic effect across all temperature zones, with the strongest promotion concentrated in the high-temperature region associated with CaCO₃ mineral decomposition. Deconvolution analysis revealed that increasing the biomass fraction systematically shifted coal-related pseudo-component peaks to lower temperatures and enhanced the hemicellulose/pectin contribution, confirming that biomass-derived volatiles accelerate lignite devolatilization. These findings demonstrate that ternary co-pyrolysis of low-rank coal with two complementary agricultural by-products is a viable and sustainable strategy to enhance pyrolysis performance, valorize agro-industrial waste, and reduce the environmental footprint of lignite utilization, providing fundamental thermochemical data for the design of integrated lignite–biomass co-processing systems. Full article

We report the synthesis of Fe/N/C ORR electrocatalysts by an original collinear CO₂ laser pyrolysis of liquid aerosol droplets in various configurations and compared them to a catalyst synthesized in the classical perpendicular one. While the precursors were always injected at the bottom side of the reactor, two collinear configurations of the laser entry into the reactor are considered: by the Top Side (T.S.) or by the Bottom Side (B.S.). The two corresponding catalysts sets show significant different ORR performances. An in-depth XPS analysis and fitting of the N1s spectra allowed for drawing the ORR performance as a function of FeN_x sites components. An original approach considering the energy delivered to a quantity of precursors in J.g⁻¹, linked to the flame temperature feature, evidenced very different conditions for perpendicular CO₂ laser pyrolysis and each of the two collinear configurations. This mass-weighted energy delivered in the classical perpendicular configuration is too low to allow for the formation of FeN_x sites and the resulting ORR performance is extremely poor, suggesting a marginal role of nitrogen species without interaction with iron atoms. In contrast, the delivered mass-weighted energies are sufficient in both collinear configurations to produce FeN_x sites. The ORR performance for catalysts produced in these both configurations is positively correlated with the amount of energy deposited on the precursors. The ORR performance in the T.S. laser configuration is positively correlated to the amount of FeN_x sites. The best performing catalysts obtained in the B.S. configuration show an opposite variation. These trends, and the ORR performance degradation of B.S. catalysts under prolonged chronoamperometry are discussed in light of the effect of temperature on the formation of the various kind of FeN_x sites. A tentative explanation is given, considering that N1s XPS fitting with a single FeN_x component may hinder the fact that Pyridinic sites components may contain a part of FeN_x sites, as suggested by theoretical calculation from the literature. The best catalysts obtained in this work by collinear configuration show similar performances to those obtained by double stage perpendicular pyrolysis previously reported with an ORR onset potential of ~860 mV. Full article

This review critically evaluates current PA6 recycling technologies, with a specific focus on caprolactam-oriented chemical recycling pathways, including hydrolysis, pyrolysis, glycolysis, ammonolysis, hydrothermal treatment, ionic-liquid-assisted depolymerization, and microwave-assisted processes. Reported caprolactam yields vary significantly depending on reaction conditions and catalyst systems, ranging from below 60 wt% in conventional hydrolysis to above 90 wt% under optimized catalytic, hydrothermal, or microwave-assisted conditions. Among these approaches, microwave-assisted hydrolysis and catalytic depolymerization have emerged as particularly promising, offering substantially reduced reaction times (minutes rather than hours), improved energy efficiency, and high monomer selectivity at moderate temperatures (typically 200–350 °C). This review integrates kinetic modeling approaches, analytical methods for monitoring depolymerization, and downstream separation considerations that govern monomer purity and recyclability. Key challenges, including energy demand, feedstock contamination, scalability, and economic competitiveness, are critically discussed in relation to industrial implementation. Overall, hydrolysis-based and microwave-assisted chemical recycling routes are the most viable pathways for closed-loop recycling of PA6. Future progress will rely on integrated reaction–separation–repolymerization designs, catalyst optimization, and process intensification to enable sustainable and industrially relevant PA6 circularity. Full article

Pyrolysis of refuse-derived fuel (RDF) is a promising waste-to-energy route, but its use in higher-value applications remains limited by tar carryover, benzene, toluene, ethylbenzene, and xylenes (BTEX), heteroatom-containing compounds, and pollutant accumulation in recirculated scrubber water. This study evaluated operating windows for RDF pyrolysis coupled with direct wet scrubbing and closed-loop water reuse, with the aim of identifying regimes suitable for different end-use tiers. A Taguchi L27 design of experiments (DOE), i.e., an orthogonal array comprising 27 experimental runs, was applied to evaluate the effects of pyrolysis temperature, residence time, scrubber liquid-to-gas ratio, and scrubber-water temperature, while sequential reuse of the same scrubber-water inventory was evaluated at 5, 10, and 15 cycles. Cleaned-gas pollutants were quantified by compound-resolved gas chromatography–mass spectrometry (GC–MS) after solid-phase adsorption (SPA) sampling, while phenolics and polycyclic aromatic hydrocarbons (PAHs) in scrubber water were determined by extraction followed by GC–MS. Feasibility within each end-use tier was defined as simultaneous satisfaction of tier-specific cleaned-gas thresholds (C_tar, C_BTEX, I_N, and I_S) and the corresponding water-loop hazard limit (I_tox), using literature-informed engineering screening criteria. The results showed that stronger scrubbing reduced gas-phase tar and BTEX burdens, whereas extended water reuse caused systematic accumulation of phenolics and PAHs and increased the composite water-loop hazard index. Boiler-grade operation remained feasible across a broad operating range, with 23 of the 27 tested conditions remaining robust, whereas internal combustion engine combined heat and power (ICE-CHP) feasibility was restricted to a narrow robust regime, and no robust microturbine-grade condition was identified. These findings show that operating windows for RDF pyrolysis must be defined jointly by gas cleanliness and water-loop management constraints. Full article

Activated carbons are usually prepared from natural precursors (e.g., fruit stones or nutshells) by carbonization and activation processes carried out at 400–1000 °C. They exhibit well-developed porosity, and chemical activation introduces hydrophilic functional groups on their surface, providing excellent sorption properties. However, the high temperatures required during thermal treatment increase production costs. In this work, cost-reducing methods for preparing carbon sorbents are proposed. Carbonization of H₃PO₄ activated waste pistachio nutshells was performed using classical pyrolysis (500 or 550 °C, 30 min, N₂ atmosphere) and microwave treatment (power 1000 W, 20 min). The properties of the synthesized carbons were characterized using thermogravimetry and spectroscopic techniques including infrared (ATR), Raman, photoelectron (XPS) spectroscopies, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). Porous structure parameters were determined using nitrogen adsorption experiments. The efficiency of Pb²⁺ removal from spiked ultrapure, tap and river water was evaluated by batch sorption experiments and inductively coupled plasma–mass spectrometry. The most porous carbons were those prepared at 500 and 550 °C, with specific surface areas of 910 and 256 m²/g, respectively. Surface phosphates increased the Pb²⁺ sorption efficiency to 99% from ultrapure water, at an initial concentration of 300 µg Pb²⁺/L. The material obtained with the microwave method was not fully carbonized and remained nonporous, but it also exhibited 99% Pb²⁺ uptake from ultrapure water due to the presence of oxygen-containing surface groups. The Pb²⁺ removal from spiked tap and river water reached up to 84% and 94%, respectively, at the spiking level of 300 µg Pb²⁺/L. Full article

The influence of the autohydrolysis temperature of sunflower stems (SSs) and sunflower inflorescence (SI) on the changes in the composition of the pyrolysis products of their hydrochars (HCs) was investigated. This research was carried out using a TG/FT-IR analytical device, the semi-quantitative ATR technique, the quantitative XRD technique, and the SEM (EDS) technique. It was found that a rise in autohydrolysis temperature alarmingly increases the contribution of undesirable hydrocarbons in the volatile pyrolysis products of HCs calculated with respect to the emitted CO₂ and substantially decreases the yield of pyrolyzed solid products. The rise in autohydrolysis temperature not only changes the content of inorganics in HCs but also influences the migration of inorganics in these samples during pyrolysis: intensifies the migration of Mg and Ca and reduces the migration of K. This affects the secondary reaction between the volatile pyrolysis products. The addition of 2 wt% of paracetamol to pyrolyzed HCs inhibits the migration of Mg and Ca and increases the migration of K with volatile products, which positively influences the reduction in undesirable compounds in the composition of emitted volatile products. The addition of paracetamol decreases the yield of pyrolyzed SSHCs by circa 2% and increases the yield of pyrolyzed SIHC₁₈₀ by almost 5%. Full article

In this study, Ag-functionalized porous ZnO nanocomposites were successfully synthesized via pyrolysis of Ag-loaded ZIF-8 precursors. The structural and surface properties of the materials were systematically characterized using XRD, XPS, FESEM, and HRTEM analyses. A gas sensor fabricated from the optimized 3.0 wt% Ag–ZnO sample exhibited a significantly enhanced response (Ra/Rg = 103) toward 100 ppm acetone at an operating temperature of 275 °C, which is approximately 2.51 times greater than that of pristine ZnO. The sensor also demonstrated rapid response/recovery times (6 s/7 s), excellent linearity over a wide concentration range (500 ppb–200 ppm), good selectivity against common interfering VOCs, and stable performance, with over 95% response retention after 30 days. The improved sensing performance is attributed to the hierarchical porous structure derived from ZIF-8 and the increased oxygen vacancy concentration and chemisorbed oxygen species induced by Ag loading, which collectively increase surface reaction activity. This work provides an effective strategy for constructing noble metal-modified porous ZnO materials for sensitive and reliable acetone detection. Full article

The improper disposal of end-of-life tires poses significant environmental challenges due to their petroleum-based composition and slow degradation, while simultaneously representing an underutilized energy resource. This study investigates the slow pyrolysis of shredded waste tires in a fixed-bed electrically heated reactor to evaluate the production and fuel properties of gaseous, liquid, and solid fractions. Experiments were conducted with 100 g samples under nitrogen at final temperatures of 400, 500, and 600 °C, with residence times of 40, 25, and 10 min, respectively. Higher temperatures promoted gas formation, increasing yields from 27% to 32% and achieving a maximum lower heating value of 30.54 MJ m⁻³ at 600 °C, with enhanced H₂ and CH₄ contents. Solid yields decreased slightly (41% to 37%), while char maintained stable heating values (~29 MJ kg⁻¹). Liquid yields remained near 33% and showed high calorific values (~41 MJ kg⁻¹), densities of 700–770 kg m⁻³, low acidity, low ash content, and increased viscosity at higher temperatures. Energy conversion efficiency reached 74.4% at 500 °C. The integrated evaluation of all fractions under identical conditions highlights fixed-bed pyrolysis as a promising pathway for waste-tire valorization and decentralized fuel production. Full article

Against the backdrop of the global search for alternatives to fossil fuels, waste tires have attracted attention as a significant resource due to their enormous production volume and considerable energy potential. However, the application of tar derived from waste tires alone is limited by its poor stability and other deficiencies. This study systematically investigates the co-pyrolysis behavior and synergistic mechanisms of waste tires and beech sawdust at various blending ratios. Thermogravimetric analysis indicates that the addition of beech sawdust reduces the decomposition temperature of the blend and induces a synergistic effect that promotes waste tire pyrolysis within the temperature range of 384–440 °C. Pyrolysis experiments results show that tar yield of the blends reached 64.45 wt.%, while the char yield decreased from 40.67 wt.% to 24.83 wt.%. Also, the presence of beech sawdust synergistically enhanced the formation of aromatic hydrocarbons in the tar of waste tires, with the total yield of aromatics increasing synergistically by up to 54.8%. Specifically, the yields of stable alkylbenzenes such as toluene and xylene were consistently promoted, whereas the yields of unsaturated aromatics such as allylbenzene and 2,4-dimethylstyrene were enhanced at low beech sawdust ratios but suppressed at higher ratios. Based on these findings, the interaction mechanisms underlying the co-pyrolysis process were elucidated, providing theoretical guidance for the high-value utilization of waste tires. Full article

Magnetic biochar (MBC), a magnetically responsive soil amendment, has attracted considerable attention due to its efficient magnetic separation capability and strong potential for remediating heavy metal-contaminated soils. Despite extensive research, a comprehensive evaluation of its raw materials, synthesis routes, performance-influencing factors, removal mechanisms, and microbial interactions remains limited. This review systematically examines biomass feedstocks and magnetic precursors used in MBC production and critically evaluates preparation methods, including hydrothermal carbonization, co-precipitation, ball milling, microwave pyrolysis, and impregnation–pyrolysis. Key factors affecting heavy metal removal—such as metal speciation, pyrolysis temperature, soil properties, dosage, and feedstock type—are discussed in detail. The primary immobilization mechanisms, including redox reactions, surface and co-precipitation, ion exchange, functional group complexation, physical adsorption, π–π interactions, and electrostatic attraction, are comprehensively analyzed. Furthermore, the interactions between MBC, soil physicochemical parameters, and microbial communities are evaluated to assess ecotoxicological implications. Finally, we provide valuable recommendations for the future direction of magnetic biochar research to advance its application in heavy metal removal from soil. Full article

Heating gases to high temperatures is essential for supplying energy to thermal and thermochemical processes. This study presents the optical–thermal design of a mini heliostat field coupled with a tubular solar receiver equipped with second optics, aiming to heat nitrogen to approximately 850 K. The secondary optical system redistributed up to 40% of the incident solar flux from the front to the rear surface of the receiver, improving radial temperature uniformity and significantly reducing thermal gradients along the tube wall. An overall optical efficiency of 65.25% was achieved, accounting for atmospheric attenuation, shading, blocking, and the cosine effect. A coupled computational model was developed by solving the conservation equations of mass, momentum, and energy, with the spatially resolved solar flux distribution obtained via ray tracing used as a thermal boundary condition. The simulation results, validated with an empirical correlation, include solar flux contours, nitrogen temperature distributions, surface temperatures, and heat transfer coefficients. The configuration with a 12 mm vertex spacing between secondary reflectors demonstrated the best thermal performance, reducing the maximum tube surface temperature by 11% and improving radial symmetry, while maintaining nitrogen outlet temperatures near the design target of 850 K. These results confirm the suitability of the system for high-temperature applications such as solar pyrolysis using nitrogen as the heat transfer fluid to deliver the required thermal energy. Full article

Utilizing the pyrolysis reaction of endothermic hydrocarbon fuels to provide thermal protection for hypersonic vehicles is a feasible approach. The introduction of catalysts or cracking-initiating additives could promote hydrocarbon fuel cracking and increase the reaction heat sink. Catalysts such as ZSM-5 zeolite, Al₂O₃, and precious metals were commonly used for hydrocarbon fuel cracking. By optimizing their pore structure and acidity, their catalytic cracking performance can be effectively improved. These catalysts can function not only as catalytic coatings but also be dispersed in the fuel to act via quasi-homogeneous catalytic cracking. Additionally, small-molecule and macromolecular additives could crack at lower temperatures to generate active free radicals, thereby initiating the cracking of hydrocarbons and increasing the reaction heat sink. Under the conditions of a reaction temperature of 650–750 °C, a pressure of 3–5.5 MPa, and a fuel flow rate of 1 g/s, quasi-homogeneous catalysts can enhance the heat sink of hydrocarbon fuel cracking by 5–21%, while cracking-initiating additives can enhance it by 5.6–8.6%. Therefore, based on the different action modes of catalysts or additives, this review summarizes the recent research on improving the cracking of endothermic hydrocarbons from three aspects: coating catalysts, quasi-homogeneous catalysts, and cracking-initiating additives. Subsequently, the potential challenges of each approach in practical applications are analyzed. Furthermore, based on the current research findings, we outline future research directions with the expectation of facilitating the advancement of efficient cracking technologies for endothermic hydrocarbons. Full article

The object of the study is a single heated carbonaceous particle of relatively small size, 0.003 to 0.01 m. Main hypothesis: The formation of soot particles and black carbon particles is caused by the thermochemical destruction of dry organic matter of forest fuel and the mechanical fragmentation of coke residue. The aim of the study is to conduct numerical simulations of heat and mass transfer in a single heated carbonaceous particle, taking into account the soot formation process and assessing its fragmentation with regard to heat exchange with the external environment in a 2D setting. As part of this study, a new model of heat and mass transfer in a pyrolyzed carbonaceous particle was developed, taking into account its step-by-step fragmentation (fragmentation tree model with four secondary particle formations from the initial particle). The calculations resulted in the distributions of temperature and volume fractions of phases in the carbonaceous particle across various scenarios. Scenarios of surface fires (initial temperatures of 900 K and 1000 K), crown fires (1100 K), and a firestorm (1200 K) for typical vegetation (pine, spruce, birch) are considered. Cubic carbonaceous particles are considered in the approximation of a 2D mathematical model. To describe heat and mass transfer in the structure of the carbonaceous particle, a differential equation of thermal conductivity with corresponding initial and boundary conditions of the third type is used, taking into account the gross reaction in the kinetic scheme of pyrolysis and soot formation. Differential analogues of partial differential equations are solved using the finite difference method of second-order approximation. Options for using the developed mathematical model and probabilistic fragmentation criterion for assessing aerosol emissions are proposed. Recommendations: The suggested mathematical model must be incorporated with mathematical models of forest fire plume and aerosol transport in the upper layers of the atmosphere. Moreover, probabilistic criteria for health assessment must be developed for the practical use of the suggested mathematical model. Full article