Pyrolysis of Polystyrene Waste: A Review

Nanoplastics composite norfloxacin induced changes in conformation and function of lysozyme and differential effects of co-exposure contamination

The concurrent environmental contamination by nanoplastics (NPs) and norfloxacin (NOR) is a burgeoning concern, with significant accumulations in various ecosystems and potential ingress into the human body via the food chain, posing threats to both public health and ecological balance. Despite the gravity of the situation, studies on the co-exposure contamination effects of these substances are limited. Moreover, the response mechanisms of key functional proteins to these pollutants are yet to be fully elucidated. In this work, we conducted a comprehensive assessment of the interaction mechanisms of NPs and NOR with lysozyme under both single and co-exposure condition, utilizing dynamic light scattering, ζ-potential measurements, multi-spectroscopy methods, enzyme activity assays and molecular docking, to obtain a relationship between the compound effects of NPs and NOR. Our results indicate that NPs adsorb NOR on their surface, forming more stable aggregates. These aggregates influence the conformation, secondary structure (α-Helix ratio decreased by 3.1 %) and amino acid residue microenvironment of lysozyme. And changes in structure affect the activity of lysozyme (reduced by 39.9 %) with the influence of composited pollutants exerting stronger changes. Molecular simulation indicated the key residues Asp 52 for protein function located near the docking site, suggesting pollutants preferentially binds to the active center of lysozyme. Through this study, we have found the effect of increased toxicity on lysozyme under the compounded conditions of NPs and NOR, confirming that the increased molecular toxicity of NPs and NOR is predominantly realized through the increase in particle size and stability of the aggregates under weak interactions, as well as induction of protein structural looseness. This study proposes a molecular perspective on the differential effects and mechanisms of NPs-NOR composite pollution, providing new insights into the assessment of in vitro responses to composite pollutant exposure.

Research on the Stability and Response of Food Packaging Polystyrene Resin Materials to γ-ray Irradiation

Radiation stability of food packaging materials is the key to ensuring food quality. In this study, 60Co γ-ray was selected to investigate the radiation resistance of food packaging polystyrene (PS) resin material, although the FTIR analysis showed that the intensity of several peaks decreased slightly. The gel permeation chromatography (GPC) results displayed that the value of peak molecular weight (Mp) of PS went from 2.68 × 105 g/mol down to 2.22 × 105 g/mol. Moreover, the residual mass (Res) of PS increased from 7.208 to 30.23%, indicating that the tendency of coking of PS was stronger after irradiation. In addition, the peak intensities of the three main pyrolysis products -CH2-, CH4, and CH2=CH2 increased by more than 30% compared to unirradiated PS, and a large number of them were detected in the whole pyrolysis process. Moreover, mechanical property analysis finds that both breaking strength and elongation data increased before irradiation dose of 50 kGy, then, decreased sharply with further increase of irradiation dose. The theoretical bond order analysis confirmed that the tertiary carbon bond attaching the benzene ring had the lowest bond energy. This study can give helpful guidance when using PS for food packing materials.

Oxidative stress and metabolic process responses of Chlorella pyrenoidosa to nanoplastic exposure: Insights from integrated analysis of transcriptomics and metabolomics

Oxidative stress is a universal interpretation for the toxicity mechanism of nanoplastics to microalgae. However, there is a lack of deeper insight into the regulation mechanism in microalgae response to oxidative stress, thus affecting the prevention and control for nanoplastics hazard. The integrated analysis of transcriptomics and metabolomics was employed to investigate the mechanism for the oxidative stress response of Chlorella pyrenoidosa to nanoplastics and subsequently lock the according core pathways and driver genes induced. Results indicated that the linoleic acid metabolism, glycine (Gly)-serine (Ser)-threonine (Thr) metabolism, and arginine and proline metabolism pathways of C. pyrenoidosa were collectively involved in oxidative stress. The analysis of linoleic acid metabolism suggested that nanoplastics prompted algal cells to secrete more allelochemicals, thereby leading to destroy the immune system of cells. Gly-Ser-Thr metabolism and arginine and proline metabolism pathways were core pathways involved in algal regulation of cell membrane function and antioxidant system. Key genes, such as LOX2.3, SHM1, TRPA1, and proC1, are drivers of regulating the oxidative stress of algae cells. This investigation lays the foundation for future applications of gene editing technology to limit the hazards of nanoplastics on aquatic organism.

Conversion of toxic pyrogenic products into syngas through catalytic pyrolysis of insulation material waste under the presence of CO2

Plastic-based insulation materials have been widely employed owing to their exceptional durability, cost-effectiveness, low weight, and low thermal conductivity. Nevertheless, the disposal of the insulation material waste (IMW) within construction waste and its recycling and recovery are challenging. Meanwhile, landfilling or incineration methods can release toxic chemicals into the environment. Consequently, the accumulation of IMW in construction waste has become a pressing environmental concern. To address this issue, this paper proposes a pyrolysis platform as a disposal management method for IMW that employs CO2 as a reactive medium. IMW composed of polystyrene in the form of extruded polystyrene underwent pyrolysis to yield pyrogenic products containing toxic chemicals. These toxic chemicals were subsequently transformed into syngas via homogeneous reactions with CO2 under certain thermal conditions and Ni/Al2O3 catalyst. This resulted in a significant reduction in the total peak areas of toxic substances in the pyrogenic oil compared with that obtained using N2 as a medium. Furthermore, the efficacy of CO2 was demonstrated to increase with an increase in the atmospheric concentration. This study implied that catalytic pyrolysis under CO2 conditions is a potential platform for converting toxic chemicals from IMW into syngas through homogeneous reactions with CO2.

Is Laccase derived from Pleurotus ostreatus effective in microplastic degradation? A critical review of current progress, challenges, and future prospects

Exploration of Pleurotus ostreatus as a biological agent in the degradation of persistent plastics like polyethylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate, revealing a promising avenue toward mitigating the environmental impacts of plastic pollution. Leveraging the intrinsic enzymatic capabilities of this fungus, mainly its production of laccase, presents a sustainable and eco-friendly approach to breaking down complex polymer chains into less harmful constituents. This review focused on enhancements in the strain's efficiency through genetic engineering, optimized culture conditions, and enzyme immobilization to underscore the potential for scalability and practical application of this bioremediation process. The utilization of laccase from P. ostreatus in plastic waste management demonstrates a vital step forward in pursuing sustainable environmental solutions. By using the potential of fungal bioremediation, researchers can move closer to a future in which the adverse effects of plastic pollution are significantly mitigated, benefiting the health of our planet and future generations.

Microplastic evidence assessment from water and sediment sampling in a shallow tropical lake

Microplastics (MPs) severely threaten inland waterbodies due to the direct impact of human activities. In the present study, spatial and temporal patterns of MPs in a shallow tropical lake were assessed, describing their size, morphology, and polymer types. Water and sediment samples were collected from Lake Chapala during three seasons, and MPs were quantified with a stereomicroscope. The structure, elemental composition, and polymeric composition were determined via environmental scanning electron microscopy and Fourier transform infrared spectroscopy. The highest average concentration of microplastics in Lake Chapala was detected during the low-water period in April 2022 (2.35 items/L), exceeding the July 2022 rainy season concentration (1.8 items/L) by 0.25 items/L, and sediment concentrations were also higher in April 2022 (219 items/kg) compared to July 2022 (210 items/kg). This study highlights the significant pollution of Lake Chapala with microplastics, emphasizing the need for urgent measures to manage plastic waste and mitigate its environmental impact on aquatic ecosystems. PRACTITIONER POINTS: Microplastic contamination was evaluated in Lake Chapala. The distribution profiles of microplastics were different in each area. Heavy metals osmium, tellurium, and rhodium were found associated with the PMs. Polymers were found in this study.

Plastic particle impacts on the cardiovascular system and angiogenesis potential

The extensive application of plastics in different sectors such as packaging, building, textiles, consumer products, and several industries has increased in recent years. Emerging data have confirmed that plastic wastes and segregates are problematic issues in aquatic and terrestrial ecosystems. The decomposition of plastic particles (PPs) leads to the release of microplastics (MPs) and nanoplastics (NPs) into the surrounding environment and entry of these particles will be problematic in unicellular and multicellular creatures. It was suggested that PPs can easily cross all biological barriers and reach different organs, especially the cardiovascular system, with the potential to modulate several molecular pathways. It is postulated that the direct interaction of PPs with cellular and subcellular components induces genotoxicity and cytotoxicity within the cardiovascular system. Meanwhile, being inert carriers, PPs can intensify the toxicity of other contaminants inside the cardiovascular system. Here, in this review article, several underlying mechanisms related to PP toxicity in the cardiovascular system were discussed in detail.

Photochemical Aerobic Upcycling of Polystyrene Plastics via Synergistic Indirect HAT Catalysis

Plastic pollution constitutes an evergrowing urgent environmental problem, since overaccumulation of plastic waste, arising from the immense increase of the production of disposable plastic products, overcame planet's capacity to properly handle them. Chemical upcycling of polystyrene constitutes a convenient method for the conversion of plastic waste into high-added value chemicals, suggesting an attractive perspective in dealing with the environmental crisis. We demonstrate herein a novel, easy-to-perform organocatalytic photoinduced aerobic protocol, which proceeds via synergistic indirect hydrogen atom transfer (HAT) catalysis under LED 390 nm Kessil lamps as the irradiation source. The developed method employs a BrCH2CN-thioxanthone photocatalytic system and was successfully applied to a variety of everyday-life plastic products, leading to the isolation of benzoic acid after simple base-acid work up in yields varying from 23-49 %, while a large-scale experiment was successfully performed, suggesting that the photocatalytic step is susceptible to industrial application.

Effects of polymer matrix and temperature on pyrolysis of tetrabromobisphenol A: Product profiles and transformation pathways

Plastics are crucial constituents in electronic waste (e-waste) and part of the issue in e-waste recycling and environmental protection. However, previous studies have mostly focused on plastic recovery or thermal behavior of flame retardants, but not both simultaneously. The present study simulated the process of e-waste thermal treatment to explore tetrabromobisphenol A (TBBPA) pyrolysis at various temperatures using polystyrene (PS), polyvinyl chloride (PVC), and e-waste plastics as polymer matrices. Pyrolysis of TBBPA produced bromophenol, bromoacetophenone, bromobenzaldehyde, and bromobisphenol A. Co-pyrolysis with the polymer matrices increased emission factors by 1 - 2 orders of magnitude. The pyrolytic products of TBBPA, TBBPA+PS, and TBBPA+PVC were mainly low-brominated bisphenol A, while that of TBBPA in e-waste plastics was consistently bromophenol. Increasing temperature drove up the proportions of gaseous and particulate products, but lowered the relative abundances of inner wall adsorbed and residual products in pyrolysis of pure TBBPA. In co-pyrolysis of TBBPA with polymer matrix, the proportions of products in different phases were no longer governed solely by temperature, but also by polymer matrix. Co-pyrolysis of TBBPA with PS generated various bromophenols, while that with PVC produced chlorophenols and chlorobrominated bisphenol A. Transformation pathways, deduced by ab initio calculations, include hydrogenation-debromination, isopropylphenyl bond cleavage, oxidation, and chlorination.

Multifactorial evaluation of an ultra-fast process for electrospinning of recycled expanded polystyrene to manufacture high-efficiency membranes for nanoparticle air filtration

The increased production of polystyrene waste has led to the need to find efficient ways to dispose of it. One possibility is the use of solid waste to produce filter media by the electrospinning technique. The aim of this work was to develop an ultra-fast electrospinning process applied to recycled polystyrene, with statistical evaluation of the influence of polymeric solution parameters (polymer concentration and percentage of DL-limonene) and process variables (flow rate, voltage, and type of support) on nanoparticle collection efficiency, air permeability, and fiber diameter. An extensive characterization of the materials and evaluation of the morphology of the fibers was also carried out. It was found that recycled expanded polystyrene could be used in electrospinning to produce polymeric membranes. The optimized condition that resulted in the highest nanoparticle collection efficiency was a polymer concentration of 13.5%, percentage of DL-limonene of 50%, voltage of 25 kV, and flow rate of 1.2 mL/h, resulting in values of 99.97 ± 0.01%, 2.6 ± 0.5 × 10-13 m2, 0.19 Pa-1, and 708 ± 176 nm for the collection efficiency of nanoparticles in the range from 6.38 to 232.9 nm, permeability, quality factor, and mean fiber diameter, respectively. All the parameters were found to influence collection efficiency and fiber diameter. The use of DL-limonene, a natural solvent, provided benefits including increased collection efficiency and decreased fiber size. In addition, the electrostatic filtration mechanism was evaluated using the presence of a copper grid as a support for the nanofibers. The findings demonstrated that an electrospinning time of only 5 min was sufficient to obtain filters with high collection efficiencies and low pressure drops, opening perspectives for the application of polystyrene waste in the development of materials with excellent characteristics for application in the area of atmospheric pollution mitigation.

Effect of Feed Mass, Reactor Temperature, and Time on the Yield of Waste Polypropylene Pyrolysis Oil Produced via a Fixed-Bed Reactor

This paper presents the results of investigations into the pyrolysis of waste polypropylene in a laboratory fixed-bed batch reactor. The experiments were designed and verified in such a way as to allow the application of the response surface methodology (RSM) in the development of an empirical mathematical model that quantifies the impacts mentioned above. The influence of the mass of the raw material (50, 100, and 150 g) together with the reactor temperature (450, 475, and 500 °C) and the reaction time (45, 50 and 75 min) was examined. It has been shown that the mass of the raw material, i.e., the filling volume of the reactor, has a significant influence on the pyrolysis oil yield. This influence exceeds the influence of reactor temperature and reaction time. This was explained by observing the temperature change inside the reactor at three different spots at the bottom, middle, and top of the reactor. The recorded temperature diagrams show that, with greater masses of feedstock, local overheating occurs in the middle part of the reactor, which leads to the overcracking of volatile products and, from there, to an increased formation of non-condensable gases, i.e., a reduced yield of pyrolytic oil.

Reduction of polystyrene/polyurethane plastic wastes from the environment into binders for water-resistant emulsion paints

Waste management is fundamental to resource and environmental sustainability. Expanded polystyrene (EPS) and polyurethane (PU) waste plastics were recycled and applied as binder in emulsion paint formulation. The recycled polystyrene (rPS) and polyurethane (rPU) were blended into composite resins, where toluene was used as the solvent. The blends of rPS and rPU were optimized, while some physicochemical properties of the composite blends (rPS/PU) were evaluated. The results showed that the incorporation of rPU into rPS increased the viscosity (1818 mPa-3924 mPa), rate of gelation (dry-to-touch time: 15 min-0.25 min), moisture content (2.7%-8.1%), moisture uptake (3.2%-5.0%), solid content (48%-53.4%) and density (0.82 g/cm3 to 1.050.82 g/cm3) of the rPS/PU composite resins. Characterization was carried out using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and atomic force microscopy (AFM). The results summarily showed that there are interactions among the rPS and rPU molecules in the composite, where complimentary structural and morphological characteristics were also achieved. The composite resin also exhibited superior bond strength (0.5-4.24 Mpa) on wood, cast mortar, ceramic, and steel surfaces due to its stronger intra- and inter-surface interactions compared to the neat rPS resin. The composite resin was used as a binder in the formulation of emulsion paint. The paint exhibited stronger resistance to water, among other superior properties, when compared to the paints formulated using neat rPS and conventional polyvinyl acetate (PVA) resins. The reduction of plastic waste in this study holds potential for the production of highly water-resistant emulsion paint for outdoor and indoor applications.

Progress in polystyrene biodegradation by insect gut microbiota

Polystyrene (PS) is frequently used in the plastics industry. However, its structural stability and difficulty to break down lead to an abundance of plastic waste in the environment, resulting in micro-nano plastics (MNPs). As MNPs are severe hazards to both human and environmental health, it is crucial to develop innovative treatment technologies to degrade plastic waste. The biodegradation of plastics by insect gut microorganisms has gained attention as it is environmentally friendly, efficient, and safe. However, our knowledge of the biodegradation of PS is still limited. This review summarizes recent research advances on PS biodegradation by gut microorganisms/enzymes from insect larvae of different species, and schematic pathways of the degradation process are discussed in depth. Additionally, the prospect of using modern biotechnology, such as genetic engineering and systems biology, to identify novel PS-degrading microbes/functional genes/enzymes and to realize new strategies for PS biodegradation is highlighted. Challenges and limitations faced by the application of genetically engineered microorganisms (GEMs) and multiomics technologies in the field of plastic pollution bioremediation are also discussed. This review encourages the further exploration of the biodegradation of PS by insect gut microbes/enzymes, offering a cutting-edge perspective to identify PS biodegradation pathways and create effective biodegradation strategies.

Chemical recycling of polyolefins via ring-closing metathesis depolymerization

The current insufficient recycling of commodity polymer waste has resulted in pressing environmental and human health issues in our modern society. In the quest for next-generation polymer materials, chemists have recently shifted their attention to the design of chemically recyclable polymers that can undergo depolymerization to regenerate monomers under mild conditions. During the past decade, ring-closing metathesis reactions have been demonstrated to be a robust approach for the depolymerization of polyolefins, producing low-strain cyclic alkene products which can be repolymerized back to new batches of polymers. In this review, we aim to highlight the recent advances in chemical recycling of polyolefins enabled by ring-closing metathesis depolymerization (RCMD). A library of depolymerizable polyolefins will be covered based on the ring size of their monomers or depolymerization products, including five-membered, six-membered, eight-membered, and macrocyclic rings. Moreover, current limitations, potential applications, and future opportunities of the RCMD approach will be discussed. It is clear from recent research in this field that RCMD represents a powerful strategy towards closed-loop chemical recycling of novel polyolefin materials.

Reactive Molecular Dynamics Simulations of Polystyrene Pyrolysis

Polymers' controlled pyrolysis is an economical and environmentally friendly solution to prepare activated carbon. However, due to the experimental difficulty in measuring the dependence between microstructure and pyrolysis parameters at high temperatures, the unknown pyrolysis mechanism hinders access to the target products with desirable morphologies and performances. In this study, we investigate the pyrolysis process of polystyrene (PS) under different heating rates and temperatures employing reactive molecular dynamics (ReaxFF-MD) simulations. A clear profile of the generation of pyrolysis products determined by the temperature and heating rate is constructed. It is found that the heating rate affects the type and amount of pyrolysis intermediates and their timing, and that low-rate heating helps yield more diverse pyrolysis intermediates. While the temperature affects the pyrolytic structure of the final equilibrium products, either too low or too high a target temperature is detrimental to generating large areas of the graphitized structure. The reduced time plots (RTPs) with simulation results predict a PS pyrolytic activation energy of 159.74 kJ/mol. The established theoretical evolution process matches experiments well, thus, contributing to preparing target activated carbons by referring to the regulatory mechanism of pyrolytic microstructure.

Impacts of Plastics on Plant Development: Recent Advances and Future Research Directions

Plastics have inundated the world, with microplastics (MPs) being small particles, less than 5 mm in size, originating from various sources. They pervade ecosystems such as freshwater and marine environments, soils, and the atmosphere. MPs, due to their small size and strong adsorption capacity, pose a threat to plants by inhibiting seed germination, root elongation, and nutrient absorption. The accumulation of MPs induces oxidative stress, cytotoxicity, and genotoxicity in plants, which also impacts plant development, mineral nutrition, photosynthesis, toxic accumulation, and metabolite production in plant tissues. Furthermore, roots can absorb nanoplastics (NPs), which are then distributed to stems, leaves, and fruits. As MPs and NPs harm organisms and ecosystems, they raise concerns about physical damage and toxic effects on animals, and the potential impact on human health via food webs. Understanding the environmental fate and effects of MPs is essential, along with strategies to reduce their release and mitigate consequences. However, a full understanding of the effects of different plastics, whether traditional or biodegradable, on plant development is yet to be achieved. This review offers an up-to-date overview of the latest known effects of plastics on plants.

A Generic Platform for Upcycling Polystyrene to Aryl Ketones and Organosulfur Compounds

Polystyrene (PS) is one of the least recycled large-volume commodity plastics due to bulkiness of foam products and associated contaminants. PS recycling is also severely hampered by the lack of financial incentive, limited versatility, and poor selectivity of existing methods. To this end, herein we report a thermochemical recycling strategy of "degradation-upcycling" to synthesize a library of high-value aromatic chemicals from PS wastes with high versatility and selectivity. Two cascade reactions are selected to first degrade PS to benzene under mild temperatures, followed by the derivatization thereof utilizing a variety of acyl/alkyl and sulfinyl chloride additives. To demonstrate the versatility, nine ketones and sulfides of cosmetic and pharmaceutical relevance were prepared, including propiophenone, benzophenone, and diphenyl sulfide. The approach is also amenable to sophisticated upcycling reaction designs and can produce desired products stepwise. The facile and versatile approach will provide a scalable and profitable methodology for upcycling PS waste into value-added chemicals.

Comprehensive Analysis of lncRNA-mRNA Expression Profiles in Depression-like Responses of Mice Related to Polystyrene Nanoparticle Exposure

Plastics in the environment can break down into nanoplastics (NPs), which pose a potential threat to public health. Studies have shown that the nervous system constitutes a significant target for nanoplastics. However, the potential mechanism behind nanoplastics' neurotoxicity remains unknown. This study aimed to investigate the role of lncRNA in the depressive-like responses induced by exposure to 25 nm polystyrene nanoplastics (PS NPs). Forty mice were divided into four groups administered doses of 0, 10, 25, and 50 mg/kg via gavage for 6 months. After conducting behavioral tests, RNA sequencing was used to detect changes in mRNAs, miRNAs, and lncRNAs in the prefrontal cortex of the mice in the 0 and 50 mg/kg PS NPs groups. The results revealed that mice exposed to chronic PS NPs developed depressive-like responses in a dose-dependent manner. It was demonstrated that 987 mRNAs, 29 miRNAs, and 116 lncRNAs were significantly different between the two groups. Then, a competing endogenous RNA (ceRNA) network containing 6 lncRNAs, 18 miRNAs, and 750 mRNAs was constructed. Enrichment results suggested that PS NPs may contribute to the onset of depression-like responses through the activation of axon guidance, neurotrophin-signaling pathways, and dopaminergic synapses. This study provided evidence of the molecular relationship between PS NPs and depression-like responses.

Uptake and effects of polystyrene nanoplastics in comparison to non-plastic silica nanoparticles on small intestine cells (IPEC-J2)

Nanoplastics smaller than 1 µm accumulate as anthropogenic material in the food chain, but only little is known about their uptake and possible effects on potentially strongly exposed cells of the small intestine. The aim of the study was to observe the uptake of 100 nm polystyrene nanoplastics into a non-tumorigenic small intestine cell culture model (IPEC-J2 cells) and to monitor the effects on cell growth and gene regulation, compared to a 100 nm non-plastic silica nanoparticle reference. The intracellular uptake of both types of nanoparticles was proven via (confocal) fluorescence microscopy and complemented with transmission electron microscopy. Fluorescence microscopy showed a growth phase-dependent uptake of nanoparticles into the cells, hence further experiments included different time points related to epithelial closure, determined via electric cell substrate impedance sensing. No retardations in epithelial closure of cells after treatment with polystyrene nanoparticles could be found. In contrast, epithelial cell closure was partly negatively influenced by silica nanoparticles. An increased production of organic nanoparticles, like extracellular vesicles, was not measurable via nanoparticle tracking analysis. An assessment of messenger RNA by next generation sequencing and subsequent pathway analysis revealed that the TP53 pathway was influenced significantly by the polystyrene nanoparticle treatment. In both treatments, dysregulated mRNAs were highly enriched in the NOTCH signaling pathway compared to the non-particle control.

Effects of ZSM-5 zeolite on pyrolysis of polystyrene: from stabilizing to catalyzing

Nonisothermal pyrolysis measurements of polystyrene (PS)/ZSM-5 zeolite hybrids are conducted in N2 and thermogravimetric results have been kinetically analyzed with different isoconversional methods. Experimental results show that the addition of 5 and 10 wt.% ZSM-5 zeolite has increased the initial pyrolysis temperature of PS while the addition of 20 and 30 wt.% ZSM-5 zeolite can significantly decrease the initial pyrolysis temperature of PS. Elevated activation energy is resulted by adding low zeolite amount whereas reduced activation energy is obtained by adding high ZSM-5 amounts. The effect of zeolite ZSM-5 on PS pyrolysis can thus be observed to transfer from stabilizing to catalyzing. Furthermore, the pyrolysis mechanism functions of PS/zeolite hybrids are determined by integrating the master plots method with a new compensation effect method, and the most appropriate reaction models are found to be F0.92, F0.85, F0.56 and A1.32 for describing the pyrolysis of the PS/ZSM-5 hybrids with a zeolite loading of 5, 10, 20 and 30 wt.%, respectively. With the kinetic parameters thus available, the temperature-dependent mass conversion curves have been recast, leading to satisfactory simulations for PS/ZSM-5 hybrids.

Reversed Controlled Polymerization (RCP): Depolymerization from Well-Defined Polymers to Monomers

Controlled polymerization methods are well-established synthetic protocols for the design and preparation of polymeric materials with a high degree of precision over molar mass and architecture. Exciting recent work has shown that the high end-group fidelity and/or functionality inherent in these techniques can enable new routes to depolymerization under relatively mild conditions. Converting polymers back to pure monomers by depolymerization is a potential solution to the environmental and ecological concerns associated with the ultimate fate of polymers. This perspective focuses on the emerging field of depolymerization from polymers synthesized by controlled polymerizations including radical, ionic, and metathesis polymerizations. We provide a critical review of current literature categorized according to polymerization technique and explore numerous concepts and ideas which could be implemented to further enhance depolymerization including lower temperature systems, catalytic depolymerization, increasing polymer scope, and controlled depolymerization.

A Thermo-Catalytic Pyrolysis of Polystyrene Waste Review: A Systematic, Statistical, and Bibliometric Approach

Global polystyrene (PS) production has been influenced by the lightness and heat resistance this material offers in different applications, such as construction and packaging. However, population growth and the lack of PS recycling lead to a large waste generation, affecting the environment. Pyrolysis has been recognized as an effective recycling method, converting PS waste into valuable products in the chemical industry. The present work addresses a systematic, bibliometric, and statistical analysis of results carried out from 2015 to 2022, making an extensive critique of the most influential operation parameters in the thermo-catalytic pyrolysis of PS and its waste. The systematic study showed that the conversion of PS into a liquid with high aromatic content (84.75% of styrene) can be achieved by pyrolysis. Discussion of PS as fuel is described compared to commercial fuels. In addition, PS favors the production of liquid fuel when subjected to co-pyrolysis with biomass, improving its properties such as viscosity and energy content. A statistical analysis of the data compilation was also discussed, evaluating the influence of temperature, reactor design, and catalysts on product yield.

The Road to Sustainable Tire Materials: Current State-of-the-Art and Future Prospectives

The development of a 100% sustainable tire has emerged as a milestone for several tire companies across the globe. It has created new commercial opportunities for the biobased, renewable, and recycled polymer materials. However, there are concerns that the incorporation of such sustainable new materials may have an undesirable impact on the main performance properties of the tire. At the same time, with new capabilities and product innovations, it can help us meet society's need in a more sustainable fashion and protect the environment. This Feature first outlines the opportunities and need for sustainable tire materials. Next, it describes the main types of sustainable material attributes in tire material, elastomers, reinforcing agents, fibers, and plasticizers, among a few others. The challenges to achieving the performance properties are discussed with possible design guidelines. Recent approaches to the tire attributes are described in the form of a meticulous overview of the existing literature, with a critical analysis of some of them. This contribution attempts to highlight, in a comprehensive way, sustainable tire materials on the basis of recent research advancements, existing challenges, and prospective future scope in this field.

Nude and Modified Electrospun Nanofibers, Application to Air Purification

Air transports several pollutants, including particulate matter (PM), which can produce cardiovascular and respiratory diseases. Thus, it is a challenge to control pollutant emissions before releasing them to the environment. Until now, filtration has been the most efficient processes for removing PM. Therefore, the electrospinning procedure has been applied to obtain membranes with a high filtration efficiency and low pressure drop. This review addressed the synthesis of polymers that are used for fabricating high-performance membranes by electrospinning to remove air pollutants. Then, the most influential parameters to produce electrospun membranes are indicated. The main results show that electrospun membranes are an excellent alternative to having air filters due to the versatility of the process, the capacity for controlling the fiber diameter, porosity, high filtration efficiency and low-pressure drop.

Catalytic Pyrolysis of Polystyrene Waste in Hydrocarbon Medium

The fast catalytic pyrolysis of polystyrene in the hydrocarbon medium (light and heavy cycle oil) over zeolite catalysts at 450-550 °C was investigated. The influence of reaction conditions (medium, temperature, vapor residence time, polystyrene concentration) on polymer conversion and product distribution was studied. It was found that the polymer conversion is close to 100%, while ethylbenzene, benzene, and toluene are the main products of its transformation. The maximum yield of ethylbenzene (80%) was achieved at 550 °C, vapor residence time 1-2 s, polystyrene concentration 10%, and heavy cycle oil as the medium. The influence of zeolite topology on product distribution was explored. The possible mechanism of polystyrene pyrolysis was proposed.

Catalytic Pyrolysis of Plastic Waste and Molecular Symmetry Effects: A Review

The present review addresses the latest findings and limitations in catalytic pyrolysis for the processing of plastic waste into valuable fuels. Compared to thermal degradation of plastics, catalytic pyrolysis provides better results in regards to the quality of the obtained liquid hydrocarbon fuel. Different types of catalysts can be used in order to improve the thermal degradation of plastics. Some of the most used catalysts are different types of zeolites (HUSY, HZSM-5, Hβ), Fluid Catalytic Cracking (FCC), silica-alumina catalysts, or natural clays. There is a need to find affordable and effective catalysts in the aim of achieving commercialization of catalytic pyrolysis of plastic waste. Therefore, this study summarizes and presents the most significant results found in the literature in regards to catalytic pyrolysis. This paper also investigates the symmetry effects of molecules on the pyrolysis process.

Upcycling Polystyrene

Several environmental and techno-economic assessments highlighted the advantage of placing polystyrene-based materials in a circular loop, from production to waste generation to product refabrication, either following the mechanical or thermochemical routes. This review provides an assortment of promising approaches to solving the dilemma of polystyrene waste. With a focus on upcycling technologies available in the last five years, the review first gives an overview of polystyrene, its chemistry, types, forms, and varied applications. This work presents all the stages that involve polystyrene's cycle of life and the properties that make this product, in mixtures with other polymers, command a demand on the market. The features and mechanical performance of the studied materials with their associated images give an idea of the influence of recycling on the structure. Notably, technological assessments of elucidated approaches are also provided. No single approach can be mentioned as effective per se; hybrid technologies appear to possess the highest potential. Finally, this review correlates the amenability of these polystyrene upcycling methodologies to frontier technologies relating to 3D printing, human space habitation, flow chemistry, vertical farming, and green hydrogen, which may be less intuitive to many.

Effects of Heating Rate and Temperature on the Thermal Pyrolysis of Expanded Polystyrene Post-Industrial Waste

The use of plastic as material in various applications has been essential in the evolution of the technology industry and human society since 1950. Therefore, their production and waste generation are high due to population growth. Pyrolysis is an effective recycling method for treating plastic waste because it can recover valuable products for the chemical and petrochemical industry. This work addresses the thermal pyrolysis of expanded polystyrene (EPS) post-industrial waste in a semi-batch reactor. The influence of reaction temperature (350-500 °C) and heating rate (4-40 °C min^-1) on the liquid conversion yields and physicochemical properties was studied based on a multilevel factorial statistical analysis. In addition, the analysis of the obtaining of mono-aromatics such as styrene, toluene, benzene, ethylbenzene, and α-methyl styrene was performed. Hydrocarbon liquid yields of 76.5-93% were achieved at reaction temperatures between 350 and 450 °C, respectively. Styrene yields reached up to 72% at 450 °C and a heating rate of 25 °C min^-1. Finally, the potential application of the products obtained is discussed by proposing the minimization of EPS waste via pyrolysis.

Characterization of tars from recycling of PHA bioplastic and synthetic plastics using fast pyrolysis

The aim of this study was to investigate the pyrolysis products of polyhydroxyalkanoates (PHAs), polyethylene terephthalate (PET), carbon fiber reinforced composite (CFRC), and block co-polymers (PS-b-P2VP and PS-b-P4VP). The studied PHA samples were produced at temperatures of 15 and 50 ^oC (PHA15 and PHA50), and commercially obtained from GlasPort Bio (PHAc). Initially, PHA samples were analyzed by nuclear magnetic resonance (NMR) spectroscopy and size exclusion chromatography (SEC) to determine the molecular weight, and structure of the polymers. Thermal techniques such as thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses were performed for PHA, CFRC, and block co-polymers to investigate the degradation temperature range and thermal stability of samples. Fast pyrolysis (500 ^oC, ∼10² °C s^-1) experiments were conducted for all samples in a wire mesh reactor to investigate tar products and char yields. The tar compositions were investigated by gas chromatography-mass spectrometry (GC-MS), and statistical modeling was performed. The char yields of block co-polymers and PHA samples (<2 wt. %) were unequivocally less than that of the PET sample (~10.7 wt. %). All PHA compounds contained a large fraction of ethyl cyclopropane carboxylate (~ 38-58 %), whereas PAH15 and PHA50 additionally showed a large quantity of 2-butenoic acid (~8-12 %). The PHAc sample indicated the presence of considerably high amount of methyl ester (~15 %), butyl citrate (~12.9 %), and tributyl ester (~17 %). The compositional analyses of the liquid fraction of the PET and block co-polymers have shown carcinogenic and toxic properties. Pyrolysis removed matrices in the CRFC composites which is an indication of potential recovery of the original fibers.

Metal-Catalyzed, Photo-Assisted Selective Transformation of Tertiary Alkylbenzenes and Polystyrenes into Carbonyl Compounds

Every year, thousands of tons of polystyrene are produced and discarded, filling landfills and polluting the marine environment. Although several degradation alternatives have been proposed, the need for an effective procedure for the chemical recycling of polystyrene still remains. Here, a vanadium-catalyzed reaction, assisted by visible light, promoted the direct, selective conversion of tertiary alkylbenzenes into acetophenone and other ketone derivatives. Likewise, standard polystyrene samples as well as polystyrenes from insulation and packaging waste could be chemically recycled into acetophenone in a scalable way regardless of their molecular weight, polydispersity, or form. Preliminary mechanistic investigations revealed the participation of singlet oxygen, superoxide, and hydroxyl radical species in this homogenously catalyzed process. Acetophenone could be used as an additive to accelerate the reaction and to increase the yields in some cases.

Bio-Based Degradable Poly(ether-ester)s from Melt-Polymerization of Aromatic Ester and Ether Diols

Vanillin, as a promising aromatic aldehyde, possesses worthy structural and bioactive properties useful in the design of novel sustainable polymeric materials. Its versatility and structural similarity to terephthalic acid (TPA) can lead to materials with properties similar to conventional poly(ethylene terephthalate) (PET). In this perspective, a symmetrical dimethylated dialkoxydivanillic diester monomer (DEMV) derived from vanillin was synthesized via a direct-coupling method. Then, a series of poly(ether-ester)s were synthesized via melt-polymerization incorporating mixtures of phenyl/phenyloxy diols (with hydroxyl side-chains in the 1,2-, 1,3- and 1,4-positions) and a cyclic diol, 1,4-cyclohexanedimethanol (CHDM). The polymers obtained had high molecular weights (M_w = 5.3–7.9 × 10⁴ g.mol⁻¹) and polydispersity index (Đ) values of 1.54–2.88. Thermal analysis showed the polymers are semi-crystalline materials with melting temperatures of 204–240 °C, and tunable glass transition temperatures (T_g) of 98–120 °C. Their 5% decomposition temperature (T_d,5%) varied from 430–315 °C, which endows the polymers with a broad processing window, owing to their rigid phenyl rings and trans-CHDM groups. These poly(ether-ester)s displayed remarkable impact strength and satisfactory gas barrier properties, due to the insertion of the cyclic alkyl chain moieties. Ultimately, the synergistic influence of the ester and ether bonds provided better control over the behavior and mechanism of in vitro degradation under passive and enzymatic incubation for 90 days. Regarding the morphology, scanning electron microscopy (SEM) imaging confirmed considerable surface degradation in the polymer matrices of both polymer series, with weight losses reaching up to 35% in enzymatic degradation, which demonstrates the significant influence of ether bonds for biodegradation.

Current Prospects for Plastic Waste Treatment

The excessive amount of global plastic produced over the past century, together with poor waste management, has raised concerns about environmental sustainability. Plastic recycling has become a practical approach for diminishing plastic waste and maintaining sustainability among plastic waste management methods. Chemical and mechanical recycling are the typical approaches to recycling plastic waste, with a simple process, low cost, environmentally friendly process, and potential profitability. Several plastic materials, such as polypropylene, polystyrene, polyvinyl chloride, high-density polyethylene, low-density polyethylene, and polyurethanes, can be recycled with chemical and mechanical recycling approaches. Nevertheless, due to plastic waste’s varying physical and chemical properties, plastic waste separation becomes a challenge. Hence, a reliable and effective plastic waste separation technology is critical for increasing plastic waste’s value and recycling rate. Integrating recycling and plastic waste separation technologies would be an efficient method for reducing the accumulation of environmental contaminants produced by plastic waste, especially in industrial uses. This review addresses recent advances in plastic waste recycling technology, mainly with chemical recycling. The article also discusses the current recycling technology for various plastic materials.

Advanced microplastic monitoring using Raman spectroscopy with a combination of nanostructure-based substrates

Micro(nano)plastic (MNP) pollutants have not only impacted human health directly, but are also associated with numerous chemical contaminants that increase toxicity in the natural environment. Most recent research about increasing plastic pollutants in natural environments have focused on the toxic effects of MNPs in water, the atmosphere, and soil. The methodologies of MNP identification have been extensively developed for actual applications, but they still require further study, including on-site detection. This review article provides a comprehensive update on the facile detection of MNPs by Raman spectroscopy, which aims at early diagnosis of potential risks and human health impacts. In particular, Raman imaging and nanostructure-enhanced Raman scattering have emerged as effective analytical technologies for identifying MNPs in an environment. Here, the authors give an update on the latest advances in plasmonic nanostructured materials-assisted SERS substrates utilized for the detection of MNP particles present in environmental samples. Moreover, this work describes different plasmonic materials-including pure noble metal nanostructured materials and hybrid nanomaterials-that have been used to fabricate and develop SERS platforms to obtain the identifying MNP particles at low concentrations. Plasmonic nanostructure-enhanced materials consisting of pure noble metals and hybrid nanomaterials can significantly enhance the surface-enhanced Raman scattering (SERS) spectra signals of pollutant analytes due to their localized hot spots. This concise topical review also provides updates on recent developments and trends in MNP detection by means of SERS using a variety of unique materials, along with three-dimensional (3D) SERS substrates, nanopipettes, and microfluidic chips. A novel material-assisted spectral Raman technique and its effective application are also introduced for selective monitoring and trace detection of MNPs in indoor and outdoor environments.

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Thermochemical Conversion of Plastic Waste into Fuels, Chemicals, and Value-Added Materials: A Critical Review and Outlooks

Plastic waste is an emerging environmental issue for our society. Critical action to tackle this problem is to upcycle plastic waste as valuable feedstock. Thermochemical conversion of plastic waste has received growing attention. Although thermochemical conversion is promising for handling mixed plastic waste, it typically occurs at high temperatures (300-800 °C). Catalysts can play a critical role in improving the energy efficiency of thermochemical conversion, promoting targeted reactions, and improving product selectivity. This Review aims to summarize the state-of-the-art of catalytic thermochemical conversions of various types of plastic waste. First, general trends and recent development of catalytic thermochemical conversions including pyrolysis, gasification, hydrothermal processes, and chemolysis of plastic waste into fuels, chemicals, and value-added materials were reviewed. Second, the status quo for the commercial implementation of thermochemical conversion of plastic waste was summarized. Finally, the current challenges and future perspectives of catalytic thermochemical conversion of plastic waste including the design of sustainable and robust catalysts were discussed.

Production and Characterization of Maximum Liquid Oil Products through Individual and Copyrolysis of Pressed Neem Oil Cake and Waste Thermocol Mixture

In this study, individual and copyrolysis experiments were performed with pressed neem oil cake (NOC) and waste thermocol (WT) to produce high grade liquid oil. The effects of reactor temperature, heating rate, feed ratio, and reaction time on product yields were investigated to identify the optimum parameters for maximum oil yield. The maximum oil yield of 49.3 wt%, 73.4 wt% and 88.5 wt% was obtained from NOC pyrolysis, copyrolysis, and WT pyrolysis under optimized conditions. During copyrolysis, the maximum oil product was obtained under NOC/WT ratio of 1 : 2 and at the temperature of 550°C. The liquid oils obtained from thermal and copyrolysis were subjected to detailed physicochemical analysis. When compared to biomass pyrolysis, the copyrolysis of WT and NOC had a substantial improvement in oil properties. The copyrolysis oil shows higher heating value of 40.3 MJ/kg with reduced water content. In addition to that, the copyrolysis oil obtained under optimized conditions is analyzed with Fourier transform infrared spectroscopy (FT-IR) and Gas chromatography–mass spectrometry (GC-MS) analysis to determine the chemical characterization. The analysis showed the presence of aliphatic and aromatic hydrocarbons in the oil.

Conversion of Plastic Waste to Carbon-Based Compounds and Application in Energy Storage Devices

At present, plastic waste accumulation has been observed as one of the most alarming environmental challenges, affecting all forms of life, economy, and natural ecosystems, worldwide. The overproduction of plastic materials is mainly due to human population explosion as well as extraordinary proliferation in the global economy accompanied by global productivity. Under this threat, the development of benign and green alternative solutions instead of traditional disposal methods such as conversion of plastic waste materials into cherished carbonaceous nanomaterials such as carbon nanotubes (CNTs), carbon quantum dots (CQDs), graphene, activated carbon, and porous carbon is of utmost importance. This critical review thoroughly summarizes the different types of daily used plastics, their types, properties, ways of accumulation and their effect on the environment and human health, treatment of waste materials, conversion of waste materials into carbon-based compounds through different synthetic schemes, and their utilization in energy storage devices particularly in supercapacitors, as well as future perspectives. The main purpose of this review is to help the targeted audience to design their futuristic study in this desired field by providing information about the work done in the past few years.

Plastic waste management practices pertaining to India with particular focus on emerging technologies

Under the parent petrochemical industries, plastic industry is proliferating enormously over the past several years globally due to its advantages in terms of weight, robustness, expense, versatility, and durability. Due to the diversified consumer base representing varied climate zones, food habits, and standards of living, the generation and growth opportunities for the plastic industry in India are particularly distinct and humongous. The present work extensively reviews the Indian plastic industry with primary focus on the evolving technologies for plastic waste valorization encompassing their level of utilization, technology readiness, and progress achieved at R&D level. The study attempts to recognize different issues related to technology, recycling, policy, research, regulation that should be given attention to formulate an improved plastic waste management strategy in the region. Though significant shares of waste plastics in the country are processed by traditional practices, state-of-the-art technologies primarily plastic to oil conversion, in road making and in cement manufacturing, are being deployed at increasing rate. Action to tackle the problem of plastic contamination in India will need to adopt a pan India strategic consensus/concurrent approach for effective waste collection and segregation with active participation of urban local bodies, fixing the role of the informal sectors, investment for reliable technology adoption with skilled manpower for operation, adoption of circular economy schemes involving plastic waste co-processing, and providing support to work on R&D for better penetration of the proven plastic valorization options along with their environmental and social implications.

Thermal Stability and Flammability Studies of MXene-Organic Hybrid Polystyrene Nanocomposites

Polystyrene (PS) is widely used in the plastics industry, but the application range of PS is limited due to its inherently high flammability. A variety of two-dimensional (2D) nanomaterials have been reported to impart excellent flame retardancy to polymeric materials. In this study, a 2D nanomaterial MXene-organic hybrid (O-Ti3C2) was applied to PS as a nanofiller. Firstly, the MXene nanosheets were prepared by acid etching, intercalation, and delamination of bulk MAX (Ti3AlC2) material. These exfoliated MXene nanosheets were then functionalized using a cationic surfactant to improve the dispersibility in DMF. Even with a small loading of functionalized O-Ti3C2 (e.g., 2 wt%), the resulting PS nanocomposite (PS/O-Ti3C2) showed good thermal stability and lower flammability evidenced by thermogravimetric analysis (TGA) and pyrolysis-combustion flow calorimetry (PCFC). The peak heat release rate (pHRR) was significantly reduced by 32% compared to the neat PS sample. In addition, we observed that the temperature at pHRR (TpHRR) shifted to a higher temperature by 22 °C. By comparing the TGA and PCFC results between the PS/MAX and different weight ratios of PS/O-Ti3C2 nanocomposites, the thermal stability and 2D thermal- and mass-transfer barrier effect of MXene-organic hybrid nanosheets were revealed to play essential roles in delaying the polymer degradation.

Immuno-modulatory Effects of Microparticles Formulated from Degradable Polystyrene Analogue

Environmental accumulation of non-degradable polystyrene (PS) microparticles from plastic waste poses potential adverse impact on marine life and human health. Herein, we formulate microparticles from a degradable polystyrene analogue (dePS) and comprehensively evaluate their immuno-modulatory characteristics. Both dePS copolymer and microparticles are chemically degradable under accelerated hydrolytic condition. In vitro studies show that dePS microparticles are non-toxic to three immortalized cell lines. While dePS microparticles do not induce macrophage polarization in vitro, dePS microparticles induce in vivo upregulation of both pro-inflammatory and anti-inflammatory biomarkers in immuno-competent mice, suggesting the coexistence of mixed phenotypes of macrophages in the host immune response to these microparticles. Interestingly, on day 7 post-injection, dePS microparticles induce a lower level of several immuno-modulatory biomarkers (MMPs activity, TNF-α, and arginase activity) compared to that of reference poly(lactic-co-glycolic acid) PLGA microparticles. Remarkably, compared to PS microparticles, dePS microparticles exhibit similar in vitro and in vivo bioactivity while acquiring additional chemical degradability. Overall, our research gains new insights into the host immune response to dePS microparticles and suggests that this degradable polystyrene analogue might be explored as an alternative material choice for biomedical and consumer care applications. This article is protected by copyright. All rights reserved.

Fabrication of Highly Photostable Polystyrene Films Embedded with Organometallic Complexes

Polystyrene is a common thermoplastic and is produced in different shapes and forms. The scale of manufacture of polystyrene has grown over the years because of its numerous applications and low cost of production. However, it is flammable, brittle, has low resistance to chemicals, and is susceptible to photodegradation on exposure to ultraviolet radiation. There is therefore scope to improve the properties of polystyrene and to extend its useful lifetime. The current work reports the synthesis of organometallic complexes and investigates their use as photostabilizers for polystyrene. The reaction of excess ibuprofen sodium salt and appropriate metal chlorides in boiling methanol gave the corresponding complexes excellent yields. The organometallic complexes (0.5% by weight) were added to polystyrene and homogenous thin films were made. The polystyrene films blended with metal complexes were irradiated with ultraviolet light for extended periods of time and the stabilizing effects of the additives were assessed. The infrared spectroscopy, weight loss, depression in molecular weight, and surface morphology of the irradiated blends containing organometallic complexes were investigated. All the synthesized organometallic complexes acted as photostabilizers for polystyrene. The damage (e.g., formation of small polymeric fragments, decrease in weight and molecular weight, and irregularities in the surface) that took place in the polystyrene blends was much lower in comparison to the pure polystyrene film. The manganese-containing complex was very effective in stabilizing polystyrene and was superior to cobalt and nickel complexes.

Back-to-monomer recycling of polycondensation polymers: opportunities for chemicals and enzymes

The use of plastics in a wide range of applications has grown substantially over recent decades, resulting in enormous growth in production volumes to meet demand. Though a wide range of biomass-derived chemicals and materials are available on the market, the production volumes of such renewable alternatives are currently not sufficient to replace their fossil-based analogues due to various factors, in particular cost-effectiveness. Hence, the majority of plastics are still industrially produced from fossil-based feedstocks. Moreover, various reports have clearly raised concern about the plastics that are not recycled at their end-of-life and instead end up in landfills or the oceans. To avoid further pollution of our planet, it is highly desirable to develop recycling processes that use plastic waste as feedstock. Chemical recycling processes could potentially offer a solution, since they afford monomers from which new polymers can be produced, with the same performance as virgin plastics. In this manuscript, the opportunities for using either chemical or biochemical (i.e., enzymatic) approaches in the depolymerization of polycondensation polymers for recycling purposes are reviewed. Our aim is to highlight the strategies that have been developed so far to break down plastic waste into monomers, providing the first step in the development of chemical recycling processes for plastic waste, and to create a renewed awareness of the need to valorize plastic waste by efficiently transforming it into virgin plastics.

On the Use of Carbon Cables from Plastic Solvent Combinations of Polystyrene and Toluene in Carbon Nanotube Synthesis

For every three people on the planet, there are approximately two Tonnes (Te) of plastic waste. We show that carbon recovery from polystyrene (PS) plastic is enhanced by the coaddition of solvents to grow carbon nanotubes (CNTs) by liquid injection chemical vapour deposition. Polystyrene was loaded up to 4 wt% in toluene and heated to 780 °C in the presence of a ferrocene catalyst and a hydrogen/argon carrier gas at a 1:19 ratio. High resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Raman spectroscopy were used to identify multiwalled carbon nanotubes (MWCNTs). The PS addition in the range from 0 to 4 wt% showed improved quality and CNT homogeneity; Raman "Graphitic/Defective" (G/D) values increased from 1.9 to 2.3; mean CNT diameters increased from 43.0 to 49.2 nm; and maximum CNT yield increased from 11.37% to 14.31%. Since both the CNT diameters and the percentage yield increased following the addition of polystyrene, we conclude that carbon from PS contributes to the carbon within the MWCNTs. The electrical contact resistance of acid-washed Bucky papers produced from each loading ranged from 2.2 to 4.4 Ohm, with no direct correlation to PS loading. Due to this narrow range, materials with different loadings were mixed to create the six wires of an Ethernet cable and tested using iPerf3; the cable achieved up- and down- link speeds of ~99.5 Mbps, i.e., comparable to Cu wire with the same dimensions (~99.5 Mbps). The lifecycle assessment (LCA) of CNT wire production was compared to copper wire production for a use case in a Boeing 747-400 over the lifespan of the aircraft. Due to their lightweight nature, the CNT wires decreased the CO₂ footprint by 21 kTonnes (kTe) over the aircraft's lifespan.

Current Developments in the Chemical Upcycling of Waste Plastics Using Alternative Energy Sources

The management of plastics waste is one of the most urgent and significant global problems now. Historically, waste plastics have been predominantly discarded, mechanically recycled, or incinerated for energy production. However, these approaches typically relied on thermal processes like conventional pyrolysis, which are energy-intensive and unsustainable. In this Minireview, some of the latest advances and future trends in the chemical upcycling of waste plastics by photocatalytic, electrolytic, and microwave-assisted pyrolysis processes are discussed as more environmentally friendly alternatives to conventional thermal reactions. We highlight how the transformation of different types of plastics waste by exploiting alternative energy sources can generate value-added products such as fuels (H₂ and other carbon-containing small molecules), chemical feedstocks, and newly functionalized polymers, which can contribute to a more sustainable and circular economy.

Catalytic pyrolysis of linear low-density polyethylene using recycled coal ash: Kinetic study and environmental evaluation

Catalytic pyrolysis offers a sustainable route to convert plastic wastes into fuel. We investigated the catalytic performance of coal ash (fly and bottom ash) at blending ratio of 5 wt%, and 15 wt% during pyrolysis of linear low-density polyethylene (LLDPE). The influence on activation energy and oil was characterized via thermogravimetric analyzer (TGA) and gas chromatography-mass spectrometry (GC-MS). Results have shown that 15 wt% bottom ash exhibited higher catalytic activity. The activation energy estimated by Coats-Redfern method decreased from 458.7 kJ·mol-1 to 437.8 kJ·mol-1, while the alicyclic hydrocarbon yield increased from 5.97% to 32.09%. This implies that CaO, which is abundant in bottom ash, could promote the conversion of LLDPE. Furthermore, a cradle-to-factory gate life cycle assessment was performed to investigate three scenarios (non-catalytic pyrolysis, 15 wt% fly ash, and 15 wt% bottom ash) of LLDPE conversion strategies via a normalization and weighting approach. It was found that LLDPE pyrolysis with 15 wt% bottom ash also showed the lowest normalized score of 2.83, implying the lowest environmental impact. This work has demonstrated that the recycling of coal ash, particularly bottom ash, as catalysts for LLDPE pyrolysis is effective.

Effect of Ultraviolet Irradiation on Polystyrene Containing Cephalexin Schiff Bases

The scale of production of polystyrene has escalated in the recent past in order to meet growing demand. As a result, a large quantity of polystyrene waste continues to be generated along with associated health and environmental problems. One way to tackle such problems is to lengthen the lifetime of polystyrene, especially for outdoor applications. Our approach is the synthesis and application of new ultraviolet photostabilizers for polystyrene and this research is focused on four cephalexin Schiff bases. The reaction of cephalexin and 3-hydroxybenzaldehyde, 4-dimethylaminobenzaldehyde, 4-methoxybenzaldehyde, and 4-bromobanzaldehyde under acidic condition afforded the corresponding Schiff bases in high yields. The Schiff bases were characterized and their surfaces were examined. The Schiff bases were mixed with polystyrene to form homogenous blends and their effectiveness as photostabilizers was explored using different methods. The methods included monitoring the changes in the infrared spectra, weight loss, depression in molecular weight, and surface morphology on irradiation. In the presence of the Schiff bases, the formation of carbonyl group fragments, weight loss, and decrease in molecular weight of polystyrene were lower when compared with pure polystyrene. In addition, undesirable changes in the surface such as the appearance of dark spots, cracks, and roughness were minimal for irradiated polystyrene containing cephalexin Schiff bases. Mechanisms by which cephalexin Schiff bases stabilize polystyrene against photodegradation have also been suggested.