Search Results (76)

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

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

The most efficient technique for resolving the issue of plastic waste disposal is by converting the wastes into high-quality liquid oils through thermal and catalytic pyrolysis. The objective of this work was to study the composition of liquid oils obtained by thermal and catalytic degradation of plastic wastes containing polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). The clay catalysts were characterized by N₂ adsorption–desorption isotherms (BET), Scanning Electron Microscopy (SEM) and Fourier transform Infrared Spectrometry (FTIR), Polarized Optical Microscopy (POM), Atomic Force Microscopy (AFM). The effect of temperature and clay catalyst type on the yields of the end-products resulting in thermo-catalytic degradation of PS has been evaluated. Degradation of PS showed the highest liquid oil production at 86.85% in comparison to other plastic types. The characterization of the liquid oils was performed by comprehensive two-dimensional gas chromatography coupled with single quadrupole mass spectrometry (GC × GC-qMS). In liquid oils of PS, eighteen principal compounds (of groups: linear hydrocarbons, mono-aromatics, and di-aromatics) were identified. In the liquid oils of the plastic waste mixture, twenty-four principal compounds (of groups: linear hydrocarbons, mono-aromatics, oxygen-containing aromatic, di-aromatics, and tri-aromatics) were identified. The liquid oils were investigated in order to reconvert them as styrene monomers or other chemicals in energy recovery. Full article

Plastics are widely used in various industries because of their light weight, low cost, and high durability. The mass production and consumption of plastics have led to a rapid increase in plastic waste problem, necessitating the development of effective recycling technologies. The chemical recycling of plastics has emerged as a promising strategy to address these challenges, enabling the conversion of plastic waste into high-purity monomers or oils, even from contaminated or mixed plastic feedstock. This review focuses on the development of catalysts for the chemical recycling of plastics in South Korea, which has one of the highest per capita plastic consumption rates and both academic and industrial efforts in this field. We examine catalytic depolymerization processes for recovering monomers from polymers, such as polyethylene terephthalate (PET) and polycarbonate (PC), as well as catalytic pyrolysis processes for polyolefins, including polyethylene (PE), polypropylene (PP), and polystyrene (PS). By summarizing recent academic research and industrial initiatives in South Korea, this review highlights the strategic role of the country in advancing chemical recycling. Moreover, this review proposes future research directions including the development of reusable catalysts, energy-efficient recycling process, and strategies for recycling mixed or contaminated plastic waste. Full article

The degradation of polystyrene (PS) represents a significant challenge in plastic waste management due to its chemical stability and low biodegradability. In this study, the catalytic degradation mechanisms of PS were investigated by density functional theory (DFT)-based calculations using the hybrid functional B3LYP and the 6-311G++(d,p) basis in Gaussian 16. The influence of acidic (AlCl₃, Fe₂(SO₄)₃) and basic (CaO) catalysts was evaluated in terms of activation energy, reaction mechanisms, and degradation products. The results revealed that acid catalysts induce PS fragmentation through the formation of carbocationic intermediates, promoting the selective cleavage of C-C bonds in branched chains with bond dissociation energies (BDE) of 176.8 kJ/mol (C1-C7) and 175.2 kJ/mol (C3-C8). In contrast, basic catalysts favor β-scission by stabilizing carbanions, reducing the BDE to 151.6 kJ/mol (C2-C3) and 143.9 kJ/mol (C3-C4), which facilitates the formation of aromatic products such as styrene and benzene. Fe₂(SO₄)₃ was found to significantly decrease the activation barriers to 328.12 kJ/mol, while the basic catalysts reduce the energy barriers to 136.9 kJ/mol. Gibbs free energy (ΔG) calculations confirmed the most favorable routes, providing key information for the design of optimized catalysts in PS valorization. This study highlights the usefulness of computational modeling in the optimization of plastic recycling strategies, contributing to the development of more efficient and sustainable methods. Full article

Hydrogen is a clean, non-polluting fuel and a key player in decarbonizing the energy sector. Interest in hydrogen production has grown due to climate change concerns and the need for sustainable alternatives. Despite advancements in waste-to-hydrogen technologies, the efficient conversion of mixed plastic waste via an integrated thermochemical process remains insufficiently explored. This study introduces a novel multi-stage pyrolysis-reforming framework to maximize hydrogen yield from mixed plastic waste, including polyethylene (HDPE), polypropylene (PP), and polystyrene (PS). Hydrogen yield optimization is achieved through the integration of two water–gas shift reactors and a pressure swing adsorption unit, enabling hydrogen production rates of up to 31.85 kmol/h (64.21 kg/h) from 300 kg/h of mixed plastic wastes, consisting of 100 kg/h each of HDPE, PP, and PS. Key process parameters were evaluated, revealing that increasing reforming temperature from 500 °C to 1000 °C boosts hydrogen yield by 83.53%, although gains beyond 700 °C are minimal. Higher reforming pressures reduce hydrogen and carbon monoxide yields, while a steam-to-plastic ratio of two enhances production efficiency. This work highlights a novel, scalable, and thermochemically efficient strategy for valorizing mixed plastic waste into hydrogen, contributing to circular economy goals and sustainable energy transition. Full article

Incineration remains Europe’s main practice for plastic packaging waste treatment, primarily due to the limitations of mechanical recycling technology. Consequently, research and development of more sustainable and flexible approaches are of high importance. Thermochemical conversion of polypropylene, polystyrene, and municipal plastic packaging mix via high-temperature flash pyrolysis (1000 °C/s) is studied in this research, focusing on the kinetics and yields of the devolatilisation stage. The primary stage results in the formation of volatile organic compounds considered intermediate products for carbon black production. The experiments were conducted in a pressurised wire mesh reactor, investigating the influence of temperature (600–1200 °C), residence time (0.5–10 s), and pressure (1–25 bar). The positive effect of temperature on the volatile yield was observed up to 2–5 s. The devolatilisation stage was completed within a maximum of 5 s at temperatures ranging from 800 to 1200 °C. The pressure was determined to be a kinetically limiting factor of the process to up to 800 °C, and the effect was not present at ≥1000 °C. Raman spectroscopy measurements revealed that pyrolytic carbon deposited on the post-experimental meshes is structurally similar to the industrially produced carbon black. The kinetic data and developed model can be further applied in the upscale reactor design. Full article

Pyrolysis technology, as a method for recycling waste polystyrenes (WPs), is widely regarded as an effective means to achieve the high value reutilization of WPs due to its environmental friendliness and the renewability of the resources used. However, in the conventional pyrolysis process for WPs, relatively high temperatures are often required to induce pyrolysis. This process not only consumes a significant amount of energy but also leads to complex and variable product compositions due to the high pyrolysis temperatures. Therefore, there is an urgent need to develop a high-value-added pyrolysis process that can lower the pyrolysis temperature of WPs and regulate its products, achieving the efficient conversion of WPs. This paper proposes a high-value “threshold temperature pyrolysis process” based on the relationships between pyrolysis temperature, threshold activation energy, and the conversion rate of WPs. The study found that under a heating rate of 10 K/min, when the conversion rate of WPs reaches 0.3, the maximum activation energy required for the entire pyrolysis process is approximately 223 kJ/mol, corresponding to a pyrolysis temperature of 673.15 K. Therefore, conducting isothermal pyrolysis at this temperature is expected to achieve the efficient conversion of WPs. The experimental results show that, compared to the conventional pyrolysis of WPs, the threshold temperature of the pyrolysis process not only lowers the pyrolysis temperature by 40 K but also regulates the distribution of pyrolysis products and the composition of pyrolysis oil, leading to a 7%wt increase in the yield of the pyrolysis oil, reaching 89.3%wt. Meanwhile, the relative content of low-molecular-weight aromatic hydrocarbons (Toluene, Styrene, and α-Methylstyrene) in the pyrolysis oil increases by 7.4%wt, which also suggests that the threshold temperature of the pyrolysis process promotes the shift in pyrolysis oil towards lighter fractions. These findings provide a solution for energy saving, emissions reductions, and the efficient conversion of WPs. Full article

Pyrolysis is recognized as a promising technology for waste plastics management. Although there have been many studies on pyrolysis of waste plastics, there is still a lack of in-depth research on the mechanism of synergistic effect between mixed plastics and the mechanism of product formation. In this paper, based on the pyrolysis characteristics of Polystyrene, Polyethylene, and mixed plastics (Polystyrene/Polyethylene), it is demonstrated that a synergistic effect exists in the co-pyrolysis of Polystyrene/Polyethylene and affects the pyrolysis behavior and pyrolysis products. It was found that polystyrene chain segments containing C=C double bonds, generated from the pyrolysis of polystyrene, initiated the pyrolysis of polyethylene during the polystyrene/polyethylene co-pyrolysis, resulting in the termination pyrolysis temperature of the co-pyrolysis being advanced by 19.8 K. Due to the reduction in the termination pyrolysis temperature by 19.8 K, the average activation energy of the co-pyrolysis was reduced by about 14%. Compared with the weighted values of single-component plastics (Polystyrene and Polyethylene), the actual oil production of co-pyrolysis increased by 9.7% to 89.80%. At the same time, the content of low molecular weight Styrene and Toluene in pyrolysis oil increased by 12.3% and 1.65%, respectively. This study provides a useful and comprehensive reference for realizing the closed cycle of “from plastics to plastics”. Full article

Thermal insulation materials are important for building energy conservation, but the inherent combustibility of these materials increases the fire risk of building facades. To better understand the fire behaviors of these materials, the study of the kinetics of thermal insulation pyrolysis is particularly important because it is the initial step in ignition and combustion during fire. In this paper, the pyrolysis behavior of expanded polystyrene (EPS), a typical non-charring insulation polymer, has been investigated by thermogravimetric analysis at five different heating rates. The model-free kinetic analysis showed that the obtained average values for E and lnA were 151.23 kJ/mol and 21.29 ln/s, respectively. Model-fitting CR and masterplot methods indicated that f(α) = [2(1-α)[-ln(1-α)]]^1/2 is considered the pyrolysis reaction mechanism of EPS degradation. Based on these results, the equation of the kinetic compensation effect was further developed as lnA = −3.1955 + 0.1736 E_α. Finally, the reaction model was reconstructed with the result of the expression f(α) = 3.95335α^0.24174 (1-α) [-ln(1-α)]^1.64712. In addition, PY-GC-MS experiments were conducted to analyze the composition of EPS pyrolysis volatiles. The results showed that the products were mainly compounds of benzene, naphthalene, and biphenyl. The analysis of EPS pyrolysis behavior and evolved gas provides numerical guidance for the future treatment and fire protection of insulation materials. Full article

Sustainable aviation fuels (SAFs), produced from waste and renewable sources, are a promising means for reducing net greenhouse gas emissions from air travel while still maintaining the quality of air transportation expected. In this work, the catalytic co-pyrolysis of polystyrene and pine with red mud (bauxite residue) and ZSM-5 catalysts at temperatures of 450 °C, 500 °C, and 550 °C was investigated as a method for producing aromatic hydrocarbons with carbon numbers ranging from 7 to 17 for use as additives to blend with SAF produced through other methods to add the required quantity of aromatic molecules to these blends. The maximum yield of kerosene-range aromatic hydrocarbons was 620 mg per gram of feedstock (62% of feedstock was converted to kerosene-range hydrocarbons) obtained at 550 °C in the presence of ZSM-5. Additionally, it was noted that a positive synergy exists between pine and polystyrene feedstocks during co-pyrolysis that cracks solid and liquid products into gaseous products similarly to that of a catalyst. The co-pyrolysis of pine and polystyrene without a catalyst produced on average 17% or 36.3 mg more kerosene-range hydrocarbons than predicted, with a maximum yield of 266 mg of C7–C17 aromatic hydrocarbons per gram of feedstock (26.6% conversion of initial feedstock) obtained at 550 °C. Full article

The rapid accumulation of polymer waste presents a significant environmental challenge, necessitating innovative waste management and resource recovery strategies. This study investigates the potential of chemical recycling via pyrolysis of plastic waste, specifically polystyrene (PS) and polypropylene (PP), to produce high-quality pyrolytic oils (WPPOs) for use as alternative fuels. The physicochemical properties of these oils were analyzed, and their performance in a gas turbine engine was evaluated. The results show that WPPOs increase NO_x emissions by 61% for PSO and 26% for PPO, while CO emissions rise by 25% for PSO. Exhaust gas temperatures increase by 12.2% for PSO and 8.7% for PPO. Thrust-specific fuel consumption (TSFC) decreases by 13.8% for PPO, with negligible changes for PSO. The environmental-economic analysis indicates that using WPPO results in a 68.2% increase in environmental impact for PS100 and 64% for PP100, with energy emission indexes rising by 101% for PS100 and 57.8% for PP100, compared to JET A. Although WPPO reduces fuel costs by 15%, it significantly elevates emissions of CO₂, CO, and NO_x. This research advances the understanding of integrating waste plastic pyrolysis into energy systems, promoting a circular economy while balancing environmental challenges. Full article

Thermochemical recycling of plastics in the presence of catalysts is often employed to facilitate the degradation of polymers. The choice of the catalyst is polymer-oriented, while its selection becomes more difficult in the case of polymeric blends. The present investigation studies the catalytic pyrolysis of polymers abundant in waste electric and electronic equipment (WEEE), including poly(acrylonitrile-butadiene-styrene) (ABS), high-impact polystyrene (HIPS) and poly(bisphenol-A carbonate) (PC), along with their blends with polypropylene (PP) and poly(vinyl chloride) (PVC). The aim is to study the kinetic mechanism and estimate the catalysts’ effect on the activation energy of the degradation. The chosen catalysts were Fe₂O₃ for ABS, Al-MCM-41 for HIPS, Al₂O₃ for PC, CaO for Blend A (comprising ABS, HIPS, PC and PP) and silicalite for Blend B (comprising ABS, HIPS, PC, PP and PVC). Thermogravimetric experiments were performed in a N₂ atmosphere at several heating rates. Information on the degradation mechanism (degradation steps, initial and final degradation temperature, etc.) was attained. It was found that for pure (co)polymers, the catalytic degradation occurred in one-step, whereas in the case of the blends, two steps were required. For the estimation of the activation energy of those degradations, isoconversional kinetic models (integral and differential) were employed. In all cases, the catalysts used were efficient in reducing the estimated E_α, compared to the values of E_α obtained from conventional pyrolysis. Full article

The persistent presence of micro- and nanoplastics (MNPs) in aquatic environments, particularly via effluents from wastewater treatment plants (WWTPs), poses significant ecological risks. This study investigated the removal efficiency of polystyrene nanoplastics (PS-NPs) using a lab-scale aerobic membrane bioreactor (aMBR) equipped with different membrane types: microfiltration (MF), commercial ultrafiltration (c-UF), and recycled ultrafiltration (r-UF) membranes. Performance was assessed using synthetic urban wastewater spiked with PS-NPs, focusing on membrane efficiency, fouling behavior, and microbial community shifts. All aMBR systems achieved high organic matter removal, exceeding a 97% COD reduction in both the control and PS-exposed reactors. While low concentrations of PS-NPs did not significantly impact the sludge settleability or soluble microbial products initially, a higher accumulation increased the carbohydrate concentrations, indicating a protective bacterial response. The microbial community composition also adapted over time under polystyrene stress. All membrane types exhibited substantial NP removal; however, the presence of nano-sized PS particles negatively affected the membrane performance, enhancing the fouling phenomena and increasing transmembrane pressure. Despite this, the r-UF membrane demonstrated comparable efficiency to c-UF, suggesting its potential for sustainable applications. Advanced characterization techniques including pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) were employed for NP detection and quantification. Full article

This study explores the intersection of waste management and sustainable fuel production, focusing on the pyrolysis of plastic waste, specifically polystyrene. We examine the physicochemical parameters of the resulting waste plastic pyrolytic oils (WPPOs), blended with kerosene to form a potential alternative fuel for gas turbines. Our findings reveal that all WPPO blends lead to increased emissions, with NO_X rising by an average of 61% and CO by 25%. Increasing the proportion of WPPO also resulted in a higher exhaust gas temperature, with an average rise of 12.2%. However, the thrust-specific fuel consumption (TSFC) decreased by an average of 13.8%, impacting the overall efficiency of waste-derived fuels. This study underscores the need for integrated waste-to-energy systems, bridging the gap between waste management and resource utilization. Full article