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Plastics are inexpensive, easy to mold, and lightweight. These and many other advantages make them very promising candidates for commercial applications. In many areas, they have substantially suppressed traditional materials. However, the problem of recycling still is a major challenge. There are both technological and economic issues that restrai...
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... imple- mentation of this technology re- quires subsidies because of the low prices of feedstock materi- als compared with plant and processing costs incurred by de- polymerizing the plastics. [27] Polymers formed through polycondensation reactions (Figure 2), such as polylactic acid (PLA), PET, and PU, can be ef- ficiently depolymerized through catalytic reactions; thus, the obtained monomers can be reused to synthesize the original polymers. [28] Achilias et al. achieved an efficient depolymerization of PET [29] and a polycarbonate [30] made from bisphenol A (PC/BPA) into their monomers and oligomers under microwave irradia- tion. ...
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... As immobilized-enzyme carriers, polymer materials have the advantages of low cost and a wide range of sources [38,39]. The synthesis of polymeric structures that can be used in enzyme-immobilization applications is seen as an important target for today's technology [40]. ...
Due to the specificity, high efficiency, and gentleness of enzyme catalysis, the industrial utilization of enzymes has attracted more and more attention. Immobilized enzymes can be recovered/recycled easily compared to their free forms. The primary benefit of immobilization is protection of the enzymes from harsh environmental conditions (e.g., elevated temperatures, extreme pH values, etc.). In this paper, catalase was successfully immobilized in a poly(aryl ether sulfone) carrier (PAES-C) with tunable pore structure as well as carboxylic acid side chains. Moreover, immobilization factors like temperature, time, and free-enzyme dosage were optimized to maximize the value of the carrier and enzyme. Compared with free enzyme, the immobilized-enzyme exhibited higher enzymatic activity (188.75 U g−1, at 30 °C and pH 7) and better thermal stability (at 60 °C). The adsorption capacity of enzyme protein per unit mass carrier was 4.685 mg. Hydrogen peroxide decomposition carried out in a continuous-flow reactor was selected as a model reaction to investigate the performance of immobilized catalase. Immobilized-enzymes showed a higher conversion rate (90% at 8 mL/min, 1 h and 0.2 g) compared to intermittent operation. In addition, PAES-C has been synthesized using dichlorodiphenyl sulfone and the renewable resource bisphenolic acid, which meets the requirements of green chemistry. These results suggest that PAES-C as a carrier for immobilized catalase could improve the catalytic activity and stability of catalase, simplify the separation of enzymes, and exhibit good stability and reusability.
... [5,6] Landfilling and incineration are two of the most popular, yet inefficient, attempts to manage plastic waste, since they are outdated and only mask the situation rather than alleviate the problem, while also participating in environmental pollution (Scheme 1). On the other hand, mechanical recycling has its own implications in real-life application [7,8] and offers a minor solution, since it leads to downgraded products, which are going to end up as waste later (Scheme 1). Modern research is now shifting towards a circular economy spirit to transform waste into useful materials, referred with the term "upcycling" (Scheme 1). ...
Although the introduction of plastics has improved humanity's everyday life, the fast accumulation of plastic waste, including microplastics and nanoplastics, have created numerous problems with recent studies highlighting their involvement in various aspects of our lives. Upcycling of plastics, the conversion of plastic waste to high‐added value chemicals, is a way to combat plastic waste that is receiving increased attention. Herein, we describe a novel aerobic photochemical process for the upcycling of real‐life polystyrene‐based plastics into benzoic acid. A new process employing a thioxanthone‐derivative, in combination with N‐bromosuccinimide, under ambient air and 390 nm irradiation is capable of upcycling real‐life polystyrene‐derived products in benzoic acid in yields varying from 24–54 %.
... Often, the method involves creating mixtures of recycled polymers, for example, PET/PE, PET/PP, and producing a new material by adding an agent that makes the mixture compatible. 287,288 As a result, composite fibres were produced from polypropylene (PP) and PET, using a copolymer of PP grafted with acrylic acid (PP-g-AA) as a compatibilizer. 289 An approach to modifying PET chains from textile recycling can also be developed to elongate these chains using different chain extenders. ...
Amongst all synthetic polymers used in the clothing industry, polyethylene terephthalate (PET) is the most widely used polyester, its fibres representing half the total PET global market (in comparison bottle PET being less than a third). Compared to bottle PET, the recycling of fabric PET fibres represents a challenge, both due to intrinsic structural differences (chain length and crystallinity) and to the presence of various additives (dyes, protection or finishing agents). Effective waste management requires addressing these additives through elimination or recycling processes. This review article aims to give an overview about all the existing means to recycle PET fibres. Textile recycling encompasses primary (closed-loop), secondary (mechanical), tertiary (chemical), and quaternary (incineration with energy recovery) processes. Mechanical recycling faces challenges due to PET's characteristics, including lower molecular weight and additives. Chemical recycling, particularly solvolysis processes (hydrolysis in neutral, acidic, or alkaline media, alcoholysis, glycolysis, aminolysis or enzymatic hydrolysis), offers a more advanced approach and will be described in detail, focusing both on the specific recycling of fibres when available and enlightening the advantages and drawbacks of each method. To discuss the environmental impact of each process, a quantitative analysis was conducted by defining the experimental domain represented by the temperature range and reaction time, and then calculating the energy-saving coefficient, as a green metric adapted to the diversity of textile PET recycling processes and data provided in the literature. This coefficient allows for discussing the relevance of using complex or non-renewable catalysts in processes, the positioning of enzymatic pathways, and the choice of reaction mechanisms applicable to the industry. A prospective approach was employed to identify key criteria for future advancements in green recycling. Subsequently, a comparative analysis of depolymerisation methods will be presented within the context of sustainable development goals (SDGs), green chemistry, and green metrics. Finally, using ε factors, this analysis will facilitate the detection and highlighting of pathways that show the most promise in terms of greening PET recycling.
... Plastic recovery comprises material recycling, mechanical or chemical reprocessing, energy recovery, and reprocessing into materials for backfilling or fuel applications [5]. Plastic recovery can be divided into four main options: quaternary recovery (incineration with energy recovery), tertiary recovery (chemical recycling through pyrolysis and solvolysis), secondary recovery (mechanical), and primary recovery (in-plant recycling) [6]. Quaternary recycling applies to practically all plastics and can save some energy, but it produces more CO 2 emissions than the other three recycling procedures. ...
This research highlights the importance of addressing bioplastic contamination in recycling processes to ensure the quality of recycled material and move towards a more sustainable circular economy. Polyethylene (PE) is a conventional plastic commonly used in packaging for which large amounts of waste are produced; therefore, PE is generally recycled and has an established recycling process. However, the contamination of biodegradable polymers in the PE waste stream could impact recycling. This study, therefore, focuses on polyethylene (PE) that has been polluted with a commercial thermoplastic starch polymer (TPS), as both materials are used to produce plastic films and bags, so cross-contamination is very likely to occur in waste separation. To achieve this, recycled PE was blended with small quantities of the commercial TPS and processed through melt extrusion and injection molding, and it was further characterized. The results indicate that the PE-TPS blend lacks miscibility, evidenced by deteriorated microstructure and mechanical properties. In addition, the presence of the commercial TPS affects the thermal stability, oxidation, and color of the recycled PE.
... The process of mechanical recycling of ABS waste involves separating the polymer from contaminants and reprocessing it by melt extrusion or other similar techniques, and it can only be carried out on single polymer waste streams [97]. [1,83] Content courtesy of Springer Nature, terms of use apply. ...
... This method of recycling aligns with the principles of sustainable development, and its products are useful as feedstock or transportation fuel. [97]. The monomers produced by this process can be converted into high-purity polymers using suitable chemical solvents and specific methodologies like pyrolysis, fluid catalytic cracking, hydrogen techniques, chemolysis, and gasification [74]. ...
Acrylonitrile butadiene styrene (ABS) is a polymer used for diverse applications such as automobile parts, electronic components, and consumer goods owing to properties like high impact strength, lightweight nature, and chemical resistance. However, the extensive use of ABS polymer generates a significant amount of waste, which has environmental repercussions due to improper disposal, such as landfilling and incineration, which severely threaten the ecosystems around us. Recycling ABS waste reduces the burden on landfills and enables us to reuse waste ABS, which aligns with the principles of sustainability. This article discusses the processes involved in recycling ABS waste, including collection, segregation, recycling technologies, preparation of blends, and applications of recycled ABS. Mechanical and chemical recycling technologies are comprehensively covered as these are the two main recycling technologies employed for ABS waste recycling. This review attempts to cover recent ABS recycling techniques and highlight the significance of ABS plastic recycling for the circular economy. Recycling ABS waste is vital in extending its lifespan, leading to more cost-effective and resource-efficient industrial processes. Embracing the transformative potential of ABS waste unlocks many possibilities and opportunities for innovation while upholding sustainability principles.
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... For thermoplastics, mechanical recycling can include melt processing/remolding and/or dissolution and solvent casting. 17 For thermosets or mixed thermoplastic/thermosets, mechanical recycling primarily consists of grinding scraps into granules, flakes, or powder and then rebonding for use as filler in new products. 18,19 In both cases, compatibilizers or other additives are often employed to facilitate blending with virgin polymer, increasing the complexity and cost of the recycling process. ...
We report a depolymerization strategy to nearly quantitatively regenerate isocyanates from thermoplastic and thermoset polyurethanes (PUs) and then resynthesize PUs using the recovered isocyanates. To date, chemical/advanced recycling of PUs has focused primarily on the recovery of polyols and diamines under comparatively harsh conditions (e.g., high pressure and temperature), and the recovery of isocyanates has been difficult. Our approach leverages an organoboron Lewis acid to depolymerize PUs directly to isocyanates under mild conditions (e.g., ∼80 °C in toluene) without the need for phosgene or other harsh reagents, and we show that both laboratory-synthesized and commercially sourced PUs can be depolymerized. Furthermore, we demonstrate the utility of the recovered isocyanate in the production of second-generation PUs with thermal properties and molecular weights similar to those of the virgin PUs. Overall, this route uniquely provides an opportunity for circularity in PU materials and can add significant value to end-of-life PU products.
... Much research has been conducted in the petrochemical industry to recycle wastes or products obtained from petroleum. [1] Because wastes like plastic and rubber pollute the environment and cause financial losses, recycling, and trash evaluation have become increasingly important. Research on sustainable development, clean production, eco-efficiency, and the preservation of natural resources has gained prominence as a result of the detrimental effects of plastic waste, which is seen as a global issue, on the ecological balance. ...
Many fillers are employed as reinforcement in polymeric materials to improve their properties and reduce expenses. This research aims to improve the mechanical and thermophysical properties of waste polyethylene terephthalate (WPET). Using recycled materials is also one of the study's objectives in support of environmental preservation. Glass fiber (3 wt.%, 6 wt.%, 9 wt.%, and 15 wt.%), calcium carbonate (5 wt.%, 15 wt.%, and 25 wt.%), and corn starch (3 wt.%) have all been added to WPET in different ratios to create composite materials. The mechanical strength, Shore D hardness tests, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and thermal, mechanical, physical, and chemical properties of these composites have all been investigated. It has been shown that while the amount of starch in the samples remains constant, the hardness increases as the amount of calcite and glass wool increases. The thermal conductivity does not significantly change as the ratio of glass fiber increases, notwithstanding a modest drop Nonetheless, the thermal conductivity values rise in tandem with the calcium carbonate (CaCO 3) ratio. ARTICLE HISTORY
... In addition, it served as a filter to prevent soil migration, often known as internal slope erosion (Tian et al. 2020). Along with polyester (PET) and polyethylene (PE), polypropylene (PP) was the most often utilized polymer for these purposes (Ignatyev et al. 2014). Polypropylene possessed exceptional chemical resistance (Wen et al. 2016). ...
Geotextile is a geosynthetic-based soil stabilization technique recently used to reinforce the soil and stabilize the canal slopes. In this study, the effect of using different nonwoven geotextile configurations on soil reinforcement and slope stability for irrigation canals subjected to loads on a canal berm was experimentally and numerically investigated. First, a laboratory model was constructed, the materials were prepared, and testing procedures were performed. The experiments were conducted to investigate settlement due to footing loads of width B acting on a canal berm in a dry case under different scenarios of geotextile soil reinforcement. Different lengths (l = 1.5, 2.0, and 4.0 B) and depths (d = 0.5, 1.0, and 2.0 B) of geotextile layers were used. Second, the experimental data were used to calibrate and validate the PLAXIS-3D model. Third, a series of simulation scenarios were conducted to investigate the joint effect of geotextile configurations on settlement. After that, the PLAXIS-3D model was used to determine the factor of safety (FoS) of the Ismailia Canal (i.e., real case study) side slope under different loading conditions with and without geotextile reinforcement. Finally, a cost analysis was conducted for Ismailia Canal under different geotextile configurations. Results showed a close agreement between experimental and PLAXIS-3D simulation results. Results also showed that geotextile reinforcement enhances bearing capacity ratio (BCR) and reduces settlement. As the length of the geotextile layer increases, the BCR increases and the settlement decreases. Among the investigated geotextile configurations, the optimum configuration was found when l = 4 B and d = B. In addition, soil reinforcement by geotextile for Ismailia Canal under an excavator load of 40 tons lowered the settlement values by about 10%, whereas its effect on the slope stability FoS was almost inconsiderable. Therefore, geotextile reinforcement can be used to relatively reduce settlement near canals’ embankments.
... However, the utilization of different polymers in products poses significant challenges when it comes to their recycling. One major drawback is the difficulty in sorting and separating these polymers during the recycling process [33]. Due to variations in chemical structures and properties, identifying and separating individual polymers becomes a complex task, increasing costs and decreasing feasibility of recycling [34]. ...
... Enzymatic degradation of PUR can be quite complex due to its various chemical compositions. 63,64 However, certain enzymes such as esterase and ureases show great potential in breaking down PUR. 28,65,66 The enzymes have the ability to specically target certain bonds in the PUR polymer, resulting in its degradation. 28 Researchers in this eld are focused on uncovering and enhancing the efficiency of these enzymes with the goal of developing effective techniques for breaking down PURs. ...
This review examines the escalating issue of plastic pollution, specifically highlighting the detrimental effects on the environment and human health caused by microplastics and nanoplastics. The extensive use of synthetic polymers such as polyethylene (PE), polyethylene terephthalate (PET), and polystyrene (PS) has raised significant environmental concerns because of their long-lasting and non-degradable characteristics. This review delves into the role of enzymatic and microbial strategies in breaking down these polymers, showcasing recent advancements in the field. The intricacies of enzymatic degradation are thoroughly examined, including the effectiveness of enzymes such as PETase and MHETase, as well as the contribution of microbial pathways in breaking down resilient polymers into more benign substances. The paper also discusses the impact of chemical composition on plastic degradation kinetics and emphasizes the need for an approach to managing the environmental impact of synthetic polymers. The review highlights the significance of comprehending the physical characteristics and long-term impacts of micro- and nanoplastics in different ecosystems. Furthermore, it points out the environmental and health consequences of these contaminants, such as their ability to cause cancer and interfere with the endocrine system. The paper emphasizes the need for advanced analytical methods and effective strategies for enzymatic degradation, as well as continued research and development in this area. This review highlights the crucial role of enzymatic and microbial strategies in addressing plastic pollution and proposes methods to create effective and environmentally friendly solutions.
