Search Results (360)

Efficient and clean utilization remains a pivotal development focus within the coal industry. Nevertheless, the application of weakly caking coal results in energy loss due to the caking property, thereby leading to a waste of resources. This paper, therefore, concentrates on the caking property, offering insights into the relevant caking mechanism, evaluation indexes, and regulation technologies associated with it. The caking mechanism delineates the transformation process of coal into coke. During pyrolysis, the active component generates the plastic mass in which gas, liquid, and solid phases coexist. With an increase in temperature, the liquid phase is diminished gradually, causing the inert components to bond. Based on the caking mechanism, evaluation indexes such as that characteristic of char residue, the caking index, and the maximal thickness of the plastic layer are proposed. These indexes are used to distinguish the strength of the caking property. However, they frequently exhibit a poor differentiation ability and high subjectivity. Additionally, some technologies have been demonstrated to regulate the caking property. Technologies such as rapid heating treatment and hydrogenation modification increase the amount of plastic mass generated, thereby improving the caking property. Meanwhile, technologies such as mechanical breaking and pre-oxidation reduce the caking property by destroying agglomerates or consuming plastic mass. Full article

This study analyzes the thermal degradation of PVA and PVA/glycerol films in air under varying heating rates. Thermogravimetric analysis (TGA) of pure PVA in both air and inert atmospheres confirmed that oxidative conditions significantly influence degradation, particularly at lower heating rates. For PVA/glycerol films in air, deconvolution of the differential thermogravimetry (DTG) curves during the main degradation stage revealed distinct peaks attributable to the degradation of glycerol, PVA/glycerol complexes, and PVA itself. Isoconversional methods showed that, for pure PVA in air, the apparent activation energy (Ea) increased with conversion, suggesting the simultaneous occurrence of multiple degradation mechanisms, including oxidative reactions, whose contribution changes over the course of the degradation process. In contrast, under an inert atmosphere, Ea remained nearly constant, consistent with degradation proceeding through a single dominant mechanism, or through multiple steps with similar kinetic parameters. For glycerol-plasticized films in air, Ea exhibited reduced dependence on conversion compared with that of pure PVA in air, with values similar to those of pure PVA under inert conditions. These results indicate that glycerol influences the oxidative degradation pathways in PVA films. These findings are relevant to high-temperature processing of PVA-based materials and to the design of thermal treatments—such as sterilization or pyrolysis—where control over degradation mechanisms is essential. Full article

The disposal of agro-industrial waste is a pressing environmental issue. At the same time, due to the high silica content in specific agricultural residues, their processed products can be utilised in various industrial sectors as substitutes for commercial materials. This study investigates the key technological, physico-mechanical, and viscoelastic properties of industrial elastomeric compounds based on synthetic styrene–butadiene rubber, intended for the tread of summer passenger car tyres, when replacing the commercially used highly reinforcing silica filler (SF), Extrasil 150VD brand (white carbon black), with a carbon–silica filler (CSF). The CSF is produced by carbonising a finely ground mixture of rice production waste (rice husks and stems) in a pyrolysis furnace at 550–600 °C without oxygen. It was found that replacing 20 wt.pts. of silica filler with CSF in industrial tread formulations improves processing parameters (Mooney viscosity increases by up to 5.3%, optimal vulcanisation time by up to 9.2%), resistance to plastic deformation (by up to 7.7%), and tackiness of the rubber compounds (by 31.3–34.4%). Viscoelastic properties also improved: the loss modulus and mechanical loss tangent decreased by up to 24.0% and 14.3%, respectively; the rebound elasticity increased by up to 6.3% and fatigue resistance by up to 2.7 thousand cycles; and the internal temperature of samples decreased by 7 °C. However, a decrease in tensile strength (by 10.7–27.0%) and an increase in wear rate (up to 43.3% before and up to 22.5% after thermal ageing) were observed. Nevertheless, the overall results of this study indicate that the CSF derived from the carbonisation of rice production waste—containing both silica and carbon components—can effectively be used as a partial replacement for the commercially utilised reinforcing silica filler in the production of tread rubber for summer passenger car tyres. Full article

This study investigates the co-pyrolysis behavior of two lignocellulosic biomass blends, bamboo (B), and rice straw (R) with a plastic polyethylene (P). A total of 15 samples, including binary and ternary blends, were analyzed. Firstly, X-ray diffraction (XRD) analysis was performed to reveal high crystallinity in the B25R75 blend (I/I_c = 13.39). Whereas, the polyethylene samples showed persistent ZrP₂O₇ and lazurite phases (I/I_c up to 3.12) attributed to additives introduced during the manufacturing of the commercial plastic feedstock. In addition, scanning electron microscopy with energy-dispersive X-ray (SEM-EDX) spectroscopy was performed to characterize the surface morphology and elemental composition of the feedstock. Moreover, thermogravimetric analysis (TGA) was employed at temperatures up to 700 °C at three different heating rates (5, 10, and 20 °C/min) under pyrolysis conditions. Kinetic analysis used TGA data to calculate activation energy via Friedman’s isoconversional method, and the blended samples exhibited a decrease in activation energy compared to the individual components. Furthermore, the study evaluated transient interaction effects among the components by assessing the deviation between experimental and theoretical weight loss. This revealed the presence of significant synergistic behavior in certain binary and ternary blends. The results demonstrate that co-pyrolysis of bamboo and rice straw with polyethylene enhances thermal decomposition efficiency and provides a more favorable energy recovery route. Full article

Rapid economic growth has led to an increase in the use of multilayer plastic packaging, which involves complex polymer compositions and hinders recycling. This study investigated the catalytic pyrolysis of plastic packaging waste in a 3000 cm³ semibatch reactor, aiming to optimize kerosene-like hydrocarbon production. The temperature (420–500 °C), N₂ flow rate (25–125 mL/min), and catalyst loading (5–20 wt.%) were examined individually and in combination with activated carbon and an Fe-doped dolomite (Fe/DM) catalyst. Central composite design (CCD) and response surface methodology (RSM) were used to identify the optimal conditions and synergistic effects. Pyrolysis product analysis involved simulation distillation gas chromatography (Sim-DGC), gas chromatography/mass spectrometry (GC/MS), and Fourier transform infrared (FT-IR) spectroscopy. The optimal conditions (440 °C, 50 mL/min N₂ flow, catalyst loading of 10 wt.% using a 5 wt.% Fe-doped dolomite-activated carbon 0.6:0.4 mass/molar ratio) yielded the highest pyrolysis oil (79.6 ± 0.35 wt.%) and kerosene-like fraction (22.3 ± 0.22 wt.%). The positive synergistic effect of Fe/DM and activated carbon (0.6:0.4) enhanced the catalytic activity, promoting long-chain polymer degradation into mid-range hydrocarbons, with secondary cracking yielding smaller hydrocarbons. The pore structure and acid sites of the catalyst improved the conversion of intermediate hydrocarbons into aliphatic compounds (C₅–C₁₅), increasing kerosene-like hydrocarbon production. Full article

Plastic waste is currently a major concern in Romania due to the annual increase in quantities generated from anthropogenic and industrial activities, especially from end-of-life vehicles (ELVs), and the need to reduce environmental impact. This study investigates an alternative valorization route for polypropylene (PP) and polyethylene (PE) plastic waste through microwave-assisted pyrolysis, aiming to maximize conversion into gaseous products, particularly hydrogen-rich gas. A monomode microwave reactor was employed, using layered configurations of plastic feedstock, silicon carbide as a microwave susceptor, and activated carbon as a catalyst. The influence of catalyst loading, reactor configuration, and plastic type was assessed through systematic experiments. Results showed that technical-grade PP, under optimal conditions, yielded up to 81.4 wt.% gas with a hydrogen concentration of 45.2 vol.% and a hydrogen efficiency of 44.8 g/g. In contrast, PE and mixed PP + PE waste displayed lower hydrogen performance, particularly when containing inorganic fillers. For all types of plastics studied, the gaseous fractions obtained have a high calorific value (46,941–55,087 kJ/kg) and at the same time low specific CO₂ emissions (4.4–6.1 × 10⁻⁵ kg CO₂/kJ), which makes these fuels very efficient and have a low carbon footprint. Comparative tests using conventional heating revealed significantly lower hydrogen yields (4.77 vs. 19.7 mmol/g plastic). These findings highlight the potential of microwave-assisted pyrolysis as an efficient method for transforming ELV-derived plastic waste into energy carriers, offering a pathway toward low-carbon, resource-efficient waste management. Full article

The emergence of plastics as an essential item in modern society has led to the problem of accumulating plastic waste. Accordingly, research is being conducted around the world to reduce the production of new plastics and develop technologies to recycle waste plastics. Among the existing waste plastic recycling technologies, oil production is possible through pyrolysis, but the pyrolysis oil produced in this way has a wide carbon range (more than C5–C25), and a very high olefin content (the presence of aromatic compounds), and the resulting high calorific value of pyrolysis oil is limited in its application range. In the case of oil obtained by pyrolyzing waste plastic containing Cl, there is a concern about corrosion in the reactor. Accordingly, it is possible to diversify the range of use of pyrolysis oil produced by suppressing corrosion through Cl removal as well as oil upgrading through cracking. Therefore, this study used red mud mixed with a series of adsorbents for Cl removal and pyrolysis oil upgrade. The adsorbent was physically mixed with a binder (kaolin or methylcellulose) and activated carbon, and the results before and after the reaction were confirmed through basic characteristic analysis. Full article

Today, the global production of plastic packaging reaches a million tons annually, resulting in significant amounts of plastic waste in the environment, which causes serious pollution issues and negatively affects the health of all living beings. However, the recycling rate for plastic packaging waste in Europe currently remains limited (~38%). With this in mind, this study focuses on the collection, characterization, and recycling, through pyrolysis, of 23 random plastic samples collected from food and non-food packaging waste in Greece. The samples were analyzed using thermal characterization techniques, such as Differential Scanning Calorimetry (DSC) and Evolved Gas Analysis (EGA), in conjunction with FTIR spectroscopy to gather important information and identify the polymers present in each sample. Furthermore, the samples underwent pyrolysis, resulting in valuable products such as the monomers styrene or ethylene, along with other useful secondary compounds, including benzoic acid, depending on the polymer type of each sample. The most prevalent polymer identified was PE (35%), while the remaining samples consisted of PET (22%), PP (22%), and PS (17%); only one sample was a blend of PE/PP. DSC facilitated the identification of the polyethylene type (LDPE, HDPE, or LLDPE). Full article

Occupational exposure to commercial formic and acetic acids through dermal contact and inhalation during rubber sheet processing poses significant health risks to workers. Additionally, the use of these acids contributes to environmental pollution by contaminating water sources and soil. This study investigates the potential of three types of wood vinegar—derived from para-rubber wood, bamboo, and eucalyptus—obtained through biomass pyrolysis under anaerobic conditions, as sustainable alternatives to formic and acetic acids in the production of ribbed smoked sheets (RSSs). The organic constituents of each wood vinegar were characterized using gas chromatography and subsequently mixed with fresh natural latex to produce coagulated rubber sheets. The physical and chemical properties, equilibrium moisture content, and drying kinetics of the resulting sheets were then evaluated. The results indicated that wood vinegar derived from para-rubber wood contained a higher concentration of acetic acid compared to that obtained from bamboo and eucalyptus. As a result, rubber sheets coagulated with para-rubber wood and bamboo vinegars exhibited moisture sorption isotherms comparable to those of sheets coagulated with acetic acid, best described by the modified Henderson model. In contrast, sheets coagulated with eucalyptus-derived vinegar and formic acid followed the Oswin model. In terms of physical and chemical properties, extended drying times led to improved tensile strength in all samples. No statistically significant differences in tensile strength were observed between the experimental and reference samples. The concentration of acid was found to influence Mooney viscosity, the plasticity retention index (PRI), the thermogravimetric curve, and the overall coagulation process more significantly than the acid type. The drying kinetics of all five rubber sheet samples displayed similar trends, with the drying time decreasing in response to increases in drying temperature and airflow velocity. Full article

This study describes the step-by-step development of a simplified system which can be implemented in industrial facilities with the help of their own surplus of plastic waste, mainly packaging waste, to reach a level of energy autonomy or semi-autonomy. This waste is converted to about 57,500 L of synthetic pyrolysis oil, which can then be used to power industries, being fed into a Combined Heat and Power system. To achieve this goal, the design has hydrocarbon stability at elevated temperature and restricted oxygen exposure, so that they can be converted to new products. Pyrolysis is a key process which causes thermo-chemical changes—ignition and vaporization. The research outlines the complete process of creating a basic small-scale pyrolysis system which industrial facilities can use to generate energy from their plastic waste. The proposed unit processes 360 tons of plastic waste yearly to produce 160 tons of synthetic pyrolysis oil which enables the generation of 500 MWh of electricity and 60 MWh of heat. The total investment cost is estimated at EUR 41,000, with potential annual revenue of up to EUR 45,000 via net metering. The conceptual design proves both environmental and economic viability by providing a workable method for decentralized waste-to-energy solutions for Small and Medium-sized Enterprises. Full article

Environmental concerns about the widespread use of non-biodegradable plastic have generated interest in developing quick and effective methods to degrade synthetic polymers. With millions of tons of plastic waste generated annually, biodegradation by microorganisms presents a promising and eco-friendly solution. However, a bottleneck has arisen due to the lack of standardized methods for verification of the biodegradation process. Based on this literature review, he techniques most commonly employed for this purpose currently include measuring mass loss, examining the surface of plastic fragments by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and using analytical methods such as Fourier transform infrared spectroscopy (FTIR), pyrolysis–gas chromatography–mass spectrometry (Pyr-GC/MS) or high-performance liquid chromatography (HPLC). Each of these methods has its advantages and disadvantages. Nevertheless, currently, there is no universal approach to accurately assess the ability of individual microorganisms to degrade plastics. In this review, we summarize the latest advances in techniques for detecting biodegradation of synthetic polymers and future directions in the development of sustainable strategies for mitigating plastic pollution. Full article

Biomass residues from the agricultural industry, logging and wood processing activities have become a valuable fuel source. If processed under pyrolysis combustion, several products are generated. Bio-oil and gases are essential alternatives to fossil coal-based fuels for energy and electricity production, whose need is constantly growing. Biochar, the porous carbon-based lightweight product, often ends up as a soil fertilizer. However, it can be applied in other industrial sectors, e.g., in plastics production or in modifying cementitious materials intended for construction needs. This work dealt with the application of small amounts of softwood-based biochar up to 2.0 wt.% on hydration kinetics and a wide range of physical and mechanical properties, such as water transport characteristics and flexural and compressive strengths of modified cement pastes. In the comparison with reference specimens, the biochar incorporation into cement pastes brought benefits like the reduction of open porosity, improvement of strength properties, and decreased capillary water absorption of 7-day and 28-day-cured cement pastes. Moreover, biochar-dosed cement pastes showed an increase in heat evolution during the hydration process, accompanied by higher consumption of clinker minerals. Considering all examined characteristics, the optimal dosage of softwood-derived biochar of 1.0 wt.% of Portland cement can be recommended. Full article

Government regulations have required consumer products—electrical and electronic components, toys, furniture, clothing, and cars— to meet ever-increasing flame resistance standards, and industry has met these norms by adding brominated fire retardants. However, end-of-life treatment and up-cycling of these plastics is challenging as the brominated compounds are endocrine disruptors, bioaccumulators, and persist in the environment. Pyrolysis, catalytic cracking, or combustion, to recover its fuel value, produces toxic brominated dibenzodioxins and dibenzofurans Here, we demonstrated the efficacy of a solvothermal treatment that extracts up to 99% of the bromine from high-impact polystyrene (HIPS) and polystyrene (PS) in electrical and electronic waste (e-waste). The process operated between 160 °C and 230 °C with ethylene glycol or triethylene glycol as the solvent and NaOH or KOH as the extraction agent (0.5 M to 2 M). The reaction rates depended on the particle size: 60 mm plastic chunks took up to between 4 and 24 h to react while fibers 3 mm in diameter reacted in less than 5 min. Full article

To ensure agricultural safety and ecological security, it is crucial to effectively immobilize emerging organic pollutants, such as plasticizers, to prevent their migration in various environmental matrices. However, the ideal immobilization agent with the advantages of being environmentally friendly is very rare. In this study, low-cost and stable near-natural immobilization agents, char-derived artificial humic acids, CHAs, were proposed and prepared via hydrothermal humification (180 °C) and pyrolysis (300, 500, or 700 °C) of agroforestry biowaste. The resulting CHAs exhibit high purity (composed primarily of C (67.28–81.35%), O (6.65–21.64%), H (1.40–5.28%), and N (0.36–0.58%)) with remarkably low ash content (5.43–10.02%). Characterization revealed a compact structure with a limited porosity with small surface area (0.27–0.32 m² g⁻¹) and pore volume (2.99–3.43 × 10⁻⁴ cm³ g⁻¹). Notably, high-temperature pyrolysis induced consumption of oxygen-containing functional groups while promoting aromatic structure formation. The sorption behavior of diethyl phthalate, a representative plasticizer, on CHAs was well described by both Langmuir isotherm and pseudo-second-order kinetic models. The CHAs exhibited remarkable sorption performance for diethyl phthalate, with a maximum sorption capacity reaching 3345 mg kg⁻¹ as determined by the Langmuir model. The sorption of diethyl phthalate onto CHAs is mainly multi-layer sorption dominated by physical processes, mainly including pore filling, partitioning, hydrogen bonding, and π–π stacking. Mean sorption energies ranging from 2.56 to 4.99 × 10⁻³ kJ mol⁻¹ indicate the predominance of physical sorption mechanisms. This study developed a method to convert the liquid by-product produced during hydrothermal humification of biowaste into stable near-natural and carbon-rich char materials, and the proposed materials show great promise in immobilizing pollutants from various environmental matrices. Full article

The rapid increase in plastic production and consumption has intensified research into human exposure to micro- and nanoplastics (MNPs) and their health effects. This study quantitatively assessed MNP internal exposure levels in non-invasive human samples, focusing on the four most common types of MNPs (≥300 nm): polyethylene terephthalate (PET), polypropylene (PP), low-density polyethylene (LDPE), and polystyrene (PS). Urine samples from 18 volunteers (4 males, 14 females) were analyzed using pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS) with P(E-¹³C₂) as an internal standard. The study developed a straightforward yet effective analytical approach for quantifying MNPs in biological fluids. MNPs were detected in all urine samples, with concentrations ranging from 0.098 to 0.986 μg/mL and an average concentration of 0.268 ± 0.235 μg/mL. LDPE, 0.074 μg/mL (interquartile range: 0.030–0.243 μg/mL), was the most abundant polymer, accounting for 67.72% of the total MNPs, followed by PS at 21.17%, while PP and PET accounted for 7.06% and 4.05%, respectively. The results also suggest that drinking water type may serve as a distinct source of MNPs in urine. This study provides novel evidence on MNP (≥300 nm) internal exposure in humans and the influence of drinking habits, highlighting the application prospects of this method in assessing the potential health risks of MNPs. Full article