Search Results (136)

Mango peel (MP), an abundant agro-industrial residue, was evaluated as a solid biofuel using combined physicochemical characterisation and non-isothermal thermogravimetric kinetics (TGA). Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) revealed hydroxyl-rich surfaces and porous microstructures. Thermogravimetric combustion, conducted at heating rates of 20–80 K min⁻¹, displayed three distinct stages. These stages correspond to dehydration (330–460 K), hemicellulose/cellulose oxidation (420–590 K), and cellulose/lignin oxidation (540–710 K). Kinetic analysis using six model-free methods (Friedman (FR), Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink (STK), Kissinger (K), and Vyazovkin (VY)) yielded activation energies (E_a) of 52–197 kJ mol⁻¹, increasing with conversion (mean E_a ≈ 111 kJ mol⁻¹). Coats–Redfern (CR) fitting confirmed a three-dimensional diffusion mechanism (D3, R² > 0.99). Thermodynamic analysis revealed that the formation of the activated complex is endothermic, with activation enthalpy (ΔH) values of 45–285 kJ mol⁻¹. The process was found to be non-spontaneous under the studied conditions, with Gibbs free energy (ΔG) values ranging from 83 to 182 kJ mol⁻¹. With a high heating value (HHV) of 21.9 MJ kg⁻¹ and favourable combustion kinetics, MP is a promising supplementary fuel for industrial biomass boilers. However, its high potassium oxide (K₂O) content requires dedicated ash management strategies to mitigate slagging risks, a key consideration for its practical, large-scale application. Full article

TGA kinetic analysis can assess the thermal stability and degradation properties of PCMs by calculating activation energies and onset degradation temperatures, which are critical elements when developing optimal PCM composition and assessing long-term performance in thermal energy storage applications. In this study, we utilize a thermogravimetric analyzer to examine the thermal stability of both solar salt phase change material (i.e., commonly used in medium-temperature applications) (NaNO₃ + KNO₃) and a composite eutectic PCM mixture (i.e., PCM with 20% biochar). The activation energies of both the pure solar salt and composite solar salt PCM sample were evaluated using a variety of different kinetic models such as Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Starink. For pure PCM, the mean activation energies calculated using the KAS, FWO, and Starink methods are 581.73 kJ/mol, 570.47 kJ/mol, and 581.31 kJ/mol, respectively. Conversely, for the composite solar salt PCM sample, the calculated experimental average activation energies are 51.67 kJ/mol, 62.124 kJ/mol, and 51.383 kJ/mol. Additionally, various machine learning models, such as linear regression, decision tree regression, gradient boosting regression, random forest regression, polynomial regression, Gaussian process regression, and KNN regression models, are developed to predict the degradation behaviour of pure and composite solar salts under different loading rates. In the machine learning models, the mass loss of the samples is the output variable and the input features are PCM type, heating rate, and temperature. The machine learning models had a great prediction performance based on experimental TGA data, with KNN regression outperforming the other models by achieving the lowest RMSE of 0.0318 and the highest R² score of 0.977. Full article

The pyrolysis of non-recyclable construction, renovation, and demolition (CRD) wood waste is a complex thermochemical process involving devolatilization, diffusion, phase transitions, and char formation. CRD wood, a low-ash biomass containing 24–32% lignin, includes both hardwood and softwood components, making it a viable heterogeneous feedstock for bioenergy production. Thermogravimetric analysis (TGA) of CRD wood residues was conducted at heating rates of 10, 20, 30, and 40 °C/min up to 900 °C, employing model-fitting (Coats–Redfern (CR)) and model-free (Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS), and Friedman (FM)) approaches to determine kinetic and thermodynamic parameters. The degradation process exhibited three stages, with peak weight loss occurring at 350–400 °C. The Coats–Redfern method identified diffusion and phase interfacial models as highly correlated (R² > 0.99), with peak activation energy (E_a) at 30 °C/min reaching 114.96 kJ/mol. Model-free methods yielded E_a values between 172 and 196 kJ/mol across conversion rates (α) of 0.2–0.8. Thermodynamic parameters showed enthalpy (ΔH) of 179–192 kJ/mol, Gibbs free energy (ΔG) of 215–275 kJ/mol, and entropy (ΔS) between −60 and −130 J/mol·K, indicating an endothermic, non-spontaneous process. These results support CRD wood’s potential for biochar production through controlled pyrolysis. Full article

Identifying sustainable and efficient methods for the degradation of plastic waste in landfills is critical for the implementation of the Saudi Green Initiative, the European Union’s Strategic Plan, and the 2030 United Nations Action Plan, all of which are aimed at achieving a sustainable environment. This study assesses the influence of palm fronds (PFR) on the thermal degradation of polypropylene plastic (PP) using TGA/FTIR experimental measurements, thermo-kinetics, and machine learning convolutional deep learning neural networks (CDNN). Thermal degradation operations were conducted on pure materials (PFR and PP) as well as mixed (blended) materials containing 25% and 50% PFR, across degradation temperatures ranging from 25 to 600 °C and heating rates of 10, 20, and 40 °C·min⁻¹. The TGA data indicated a synergistic interaction between the agricultural waste (PFR) and PP plastic, with decreased thermal stability at temperatures below 500 °C, attributed to the hemicellulose and cellulose present in the PFR biomass. In contrast, at temperatures exceeding 500 °C, the presence of lignin retards the degradation of the PFR biomass and blends. Activation energy values between 81.92 and 299.34 kJ·mol⁻¹ were obtained through the application of the Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) model-free methods. The application of CDNN facilitated the extraction of significant features and labels, which were crucial for enhancing modeling accuracy and convergence. This modeling and simulation approach reduced the overall cost function from 41.68 to 0.27, utilizing seven hidden neurons, and 673,910 epochs in 13.28 h. This method effectively bridged the gap between modeling and experimental data, achieving an R² value of approximately 0.992, and identified sample composition as the most critical parameter influencing the thermolysis process. It is hoped that such findings may facilitate an energy-efficient pathway necessary for the thermal decomposition of plastic materials in landfills. Full article

This study presents a comprehensive kinetic and thermodynamic investigation of dried orange peel (OP) combustion, employing thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) at high heating rates (20–80 K min⁻¹). This gap in high heating rate analysis motivates the novelty of present study, by investigating OP combustion at 20, 40, 60, and 80 K min⁻¹ using TGA, to closely simulate rapid thermal conditions typical of industrial combustion processes. Thermal decomposition occurred in three distinct stages corresponding sequentially to the dehydration, degradation of hemicellulose, cellulose, and lignin. Activation energy (E_a) was calculated using six model-free methods—Friedman (FR), Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink (STK), Kissinger (K), and Vyazovkin (VY)—yielding values between 64 and 309 kJ mol⁻¹. The E_a increased progressively from the initial to final degradation stages, reflecting the thermal stability differences among biomass constituents. Further kinetic analysis using the Coats–Redfern (CR) model-fitting method identified that first-order (F1), second-order (F2), and diffusion-based mechanisms (D1, D2, D3) effectively describe OP combustion. Calculated thermodynamic parameters—including enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS)—indicated the endothermic and increasingly non-spontaneous nature of the reactions at higher conversions. These findings demonstrate the potential of OP, an abundant agricultural waste product, as a viable bioenergy resource, contributing valuable insights into sustainable combustion processes. Full article

This study examines the thermal characteristics and kinetics of oil shale combustion using thermogravimetric analysis (TGA) at various heating rates. The combustion process includes three stages: dehydration, main combustion (70–80% mass loss), and mineral decomposition. Kinetic analysis using model-free (Ozawa–Flynn–Wall, Kissinger) and model-based (multi-step reaction kinetics) methods revealed that the second-order reaction model (F2) had the highest accuracy. Oil shale combustion involves multi-step reactions, with activation energy and pre-exponential factors varying nonlinearly with conversion rates. Combining model-free and model-based methods provides insights for optimizing combustion processes and equipment design for the efficient utilization of unconventional energy resources. Full article

The fallen leaf has the potential to be energy-valorized in cities with sustainability goals. Thermochemical characterization of garden waste through pyrolysis and combustion kinetics will establish the reactivity of this lignocellulosic biomass as biofuel for thermochemical conversion processes for energy recovery. Herein, the thermal degradation of two types of pellets produced from fallen leaf (pellets without glycerol PG0, and pellets with 5 wt% glycerol PG5) are characterized under inert and oxidative atmospheres using three different approaches: thermogravimetry (TG) and differential thermogravimetry (DTG) analyses, TG-based reactivity, and reaction kinetics from three model-free isoconversional methods. The model-free isoconversional methods are Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Friedman, which were applied for estimating the kinetic parameters, activation energy (Eα) and pre-exponential factor, using different heating rates (20, 30, and 40 °C/min) to ensure reliable data interpretation. The pyrolysis results showed that PG5 was more reactive compared to PG0 because the addition of glycerol during the pelletizing process increased the volatile matter and oxygen content in PG5. Likewise, the higher reactivity of PG5 under pyrolysis was determined by average activation energy (Eα) with an average value of 96.82 kJ/mol compared to 106.46 kJ/mol for PG0. During the combustion process, Eα was 90.70 kJ/mol and 90.29 kJ/mol for PG0 and PG5, respectively. Finally, both materials exhibited higher reactivity under an oxidative atmosphere. Therefore, according to our results, the pellets produced from leaf litter can be used as biofuels for thermochemical processes, highlighting that using glycerol as a binder favors the reactivity of the densified garden waste. Full article

Converting food waste into biofuel resources is considered a promising approach to address the rapid increase in energy demand, reduce dependence on fossil fuels, and decrease environmental hazards. In Egypt, large quantities of fried tilapia fish waste are produced in restaurants and households, posing challenges for proper waste management due to its decaying nature. The current study investigates the kinetic triplet and thermodynamic parameters of fried tilapia fish waste (FTFW) pyrolysis. Kinetic analysis was carried out using four iso-conversional models, Friedman, Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Starink, at heating rates of 10, 15, and 20 °C/min. The study findings indicate that FTFW decomposes within the temperature range of 382–407 °C. The estimated activation energy using the Friedman, FWO, KAS, and Starink methods ranged from 43.2 to 208.2, 31.3 to 148.3, 22.3 to 179.3, and 24.1 to 181.3 kJ/mol, respectively, with average values of 118.4, 96.7, 109.7, and 100.5 kJ/mol, respectively. The average enthalpy change determined using the Friedman, FWO, KAS, and Starink methods was 113.45, 91.78, 95.58, and 104.73 kJ/mol, respectively. The average values of Gibbs free energy change for the Friedman, KAS, FWO, and Starink, methods were 192.71, 171.04, 174.83, and 183.99 kJ/mol, respectively. Full article

In this study, the decomposition processes of tabletop sweeteners based on steviol glycosides were investigated to determine the kinetic parameters of activation energy (E_a) and the logarithm of the pre-exponential factor (ln A) based on the converted fraction (α). These parameters were assessed using the Friedman and Ozawa–Flynn–Wall isoconversion methods with the NETZSCH Kinetics Neo software and the Model Free package. This study also aimed to explore the probable mechanism of the thermal decomposition of these materials. The thermal degradation of the samples was carried out in a temperature range of 150 to 400 °C under nitrogen flow, with heating rates of 5, 10, and 20 °C min⁻¹. The results indicated that both stevioside and steviol glycoside (E3) samples require higher energy to initiate their decomposition. Furthermore, the samples based on steviol glycosides exhibited distinct probable decomposition mechanisms: a model of two consecutive reactions followed by two competitive reactions for stevioside (FnFnFnFn model), three consecutive stages for the steviol glycoside sample (FnCnFn model), two consecutive stages for the steviol glycoside + erythritol sample (FnCn model), and three consecutive stages for the steviol glycoside + xylitol sample (FnFnFn model). Full article

In this study, modification of poly(adipic anhydride) through branching its chains was carried out via melt condensation polymerization with D-mannitol. The percentage of mannitol was varied (3, 4, 5, 10, 15, and 20 Wt.%) and the resulting copolymers were purified and characterized by FT-IR and ¹³C-NMR. These analyses indicated that linear chains of poly(adipic anhydride) can react with strong nucleophiles and dissociate to produce highly branched poly(adipic anhydride-co-mannitol adipate) which confirms the validity of the proposed mechanism. The copolymer’s molecular weight characteristics have been also examined using GPC analysis. Thermal properties of copolymers were also investigated using TGA, DTG, and DCS analyses. TGA/DTG revealed that the thermal degradation of copolymers proceeds in multi-stage decomposition, whereas the shift and pattern change of the melting point peak of DSC curves can identify the weight percentage of mannitol for homogenous copolymers. Two non-isothermal models, the Flynn–Wall–Ozawa and Kissinger methods, have been also employed to analyze thermogravimetric data collected from the thermal decomposition of the copolymers and found that Flynn–Wall–Ozawa method provides better results with R² correlation up to 99.3%. The activation energy in the region of T_max was determined and found that an increase in mannitol contents in copolymer has a positive impact on its thermal stability. Full article

Mg₇₂Zn₂₇Pt₁ and Mg₇₂Zn₂₇Cu₁ metallic glasses were produced using a melt-spinner. Their crystallization kinetics were investigated during annealing with five heating rates using DSC. Amorphous Mg₇₂Zn₂₇Pt₁ crystallized in the form of one and Mg₇₂Zn₂₇Cu₁ crystallized in the form of two exothermic crystallization peaks. It was noticed that the glass transition, the onset crystallization and the crystallization peak temperatures were strongly heating-rate-dependent. The addition of Pt and Cu increased the stability compared to that of binary Mg-Zn glass, and especially so with Pt, due to its higher melting point and different atom size to those of Mg and Zn. The activation energies were calculated using six model-free methods: the Kissinger, Ozawa–Flynn–Wall, Boswell, Tang, Augis–Bennett and Gao–Wang methods. The Augis–Bennett and Gao–Wang methods allow for the calculation of only the activation energy at the crystallization peak but they are the only ones that consider $T_x$ or $dx/dT$. For Mg₇₂Zn₂₇Pt₁, the calculated values fluctuate in the ranges 114.60–117.99 kJ/mol, 102.46–105.98 kJ/mol and 71.16–98.62 kJ/mol for $E_g$, $E_x$ and $E_p$, respectively, whereas, for Mg₇₂Zn₂₇Cu₁, the calculated values are in the ranges of 98.51–101.77 kJ/mol, 95.15–98.51 kJ/mol and 55.15–93.34 kJ/mol for $E_g$, $E_x$ and $E_p$, respectively. Both alloys are meta-stable in the amorphous state and crystallization occurs spontaneously. The Kissinger, Ozawa–Flynn–Wall, Tang and Boswell methods give similar values for the activation energy. The Gao–Wang method significantly underestimates values compared to other methods. The Augis–Bennett method shows much lower values for the local activation energy. Considering the ease of their formulas, best convergence and widespread use in the literature, the Kissinger and Ozawa–Flynn–Wall methods will work very well for any comparison. Full article

This study investigates the development and application of climate friendly processes in the foundry industry, particularly with regard to the use of inorganic binders to reduce emissions and pollution. An inorganic binder system based on water glass, which is used in 3D printing technology for the production of sand molds and core, is being tested and the possibility of determining a kinetic model for the curing kinetics of sodium silicate as an inorganic binder is investigated. The aim is to use a kinetic model to better describe the microwave process currently required in binder jetting for drying the binder and catalyzing the chemical reaction of the binder during curing. For sodium silicate in particular, there is still no scientific knowledge available in this respect, which is why basic investigations based on thermogravimetry or heat flow difference calorimetry must first be carried out. In this way, it should be possible to simulate the drying process in the microwave, which has so far been based on empirical values, in order to maximize the efficiency of this process and also the quality of the components. The results indicate that the weight loss and weight changes depend on the heating rates and that a heating rate of 30 K/min is not sufficient to fully cure the sample at 500 °C. The thermogravimetric analysis (TGA) shows that the fastest weight loss occurs at the beginning of the measurement, indicating a partial pre-curing of the sample before the measurement. From the measurements, an average activation energy of 144.18 kJ/mol could be determined using the Friedman method and 123.36 kJ/mol and 123.31 kJ/mol using the Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose methods, respectively. Measurements of the heat flow at a heating rate of 30 K/min indicate partially exothermic reactions during the curing process. Full article

The buildup of abandoned plastics in the environment and the need to optimize agricultural waste utilization have garnered scrutiny from environmental organizations and policymakers globally. This study presents an assessment of the thermal decomposition of date seeds (DS), polypropylene homopolymer (PP), and their composites (DS/PP) through experimental measurements, machine learning convolutional deep neural networks (CDNN), and kinetic and thermodynamic analyses. The experimental measurements involved the pyrolysis and co-pyrolysis of these materials in a nitrogen-filled thermogravimetric analyzer (TGA), investigating degradation temperatures between 25 and 600 °C with heating rates of 10, 20, and 40 °C.min⁻¹. These measurements revealed a two-stage process for the bio-composites and a decrease in the thermal stability of pure PP due to the moisture, hemicellulose, and cellulose content of the DS material. By utilizing machine learning CDNN, algorithms and frameworks were developed, providing responses that closely matched ($R^2~0.942$) the experimental data. After various modelling modifications, adjustments, and regularization techniques, a framework comprising four hidden neurons was determined to be most effective. Furthermore, the analysis revealed that temperature was the most influential parameter affecting the thermal decomposition process. Kinetic and thermodynamic analyses were performed using the Coats–Redfern and general Arrhenius model-fitting methods, as well as the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose model-free approaches. The first-order reaction mechanism was identified as the most appropriate compared to the second and third order F-Series solid-state reaction mechanisms. The overall activation energy values were estimated at 51.471, 51.221, 156.080, and 153.767 kJ·mol⁻¹ for the respective kinetic models. Additionally, the kinetic compensation effect showed an exponential increase in the pre-exponential factor with increasing activation energy values, and the estimated thermodynamic parameters indicated that the process is endothermic, non-spontaneous, and less disordered. Full article

Sulfobutyl-ether-beta-cyclodextrin sodium salt (SBECD) is a modified cyclodextrin widely used in the pharmaceutical industry to enhance the solubility and stability of poorly water-soluble drugs. As a derivative of beta-cyclodextrin, it is produced by introducing sulfobutyl ether groups into the beta-cyclodextrin molecule, which significantly increases its water solubility and decreases its toxicity compared to unmodified cyclodextrins. This study investigates the spectral and PXR diffraction characterization of SBECD, its thermal stability profile, and decomposition mechanism using isoconversional methods. Since the simple ASTM E698 method does not provide realistic data, the Flynn–Wall–Ozawa, Friedman, and NPK methods were employed, leading to the kinetic triplet that characterizes the oxidative thermolysis of this compound. Full article

Branch wood, as a renewable biomass resource, presents certain challenges due to its high volume, complex physical properties, difficulty in handling, and relatively high production costs. Potassium chloride (KCl) treatments were applied to ash branch wood (ABW) using solutions with concentrations of 5%, 10%, and 15% via immersion. Pyrolysis tests were performed at different pyrolysis temperatures (450 °C, 600 °C, 750 °C) and different pyrolysis times (2 h, 3 h, 4 h). The thermal degradation behavior was meticulously examined through Thermogravimetric Analysis (TGA). Furthermore, the pyrolysis kinetics were assessed using the Flynn–Wall–Ozawa (FWO) model, which allowed for the determination of the kinetic parameters and the exploration of the catalytic influence of KCl on the pyrolysis process. The morphology and adsorption properties of the biochar were evaluated employing SEM-EDS and BET characterization methods, respectively. The results show that the higher the impregnation concentration of ABW, the greater the shift in the TG and DTG curves, and the lower the initial temperature and maximum weight loss temperature in the devolatilization stage. The calculation of pyrolysis kinetic parameters indicates that adding a higher concentration of KCl to ABW results in a lower initial temperature and activation energy for the volatile phase of ABW. At the same time, a higher KCl concentration leads to an increased biochar yield; under single-factor conditions, a biochar yield of up to 35.81% can be achieved with an impregnation concentration of 15%. A lower KCl is more conducive to the pyrolysis reaction, with a lower activation energy throughout the devolatilization stage compared to raw ABW. Additionally, ABW treated with a low concentration of KCl results in a higher specific surface area and pore volume of the biochar. The maximum values are achieved when the KCl solution concentration is 5%, with a specific surface area of 4.2 m²/g and a pore volume of 0.00914 cm³/g. Based on these results, this paper explores the catalytic pyrolysis patterns of KCl on branch waste, providing theoretical guidance for the effective utilization of branch wood and the preparation process of biochar. Full article