Search Results (479)

The growing volume of plastic waste is one of the major environmental problems of this century. Among the plastics discarded each year, polyethylene terephthalate (PET) waste accounts for a significant proportion, making it increasingly urgent to establish new methods for its recovery and recycling. This study addresses the manufacture and characterisation of new gypsum composites incorporating PET waste from bottle preforms. Specifically, different series were produced by partially replacing the original gypsum with rPET at 7.5%, 15.0%, and 22.5% by volume. The resulting composites were then subjected to mechanical, thermal and environmental characterisation. All the materials analysed exceeded the minimum mechanical strength values set by the regulations, achieving flexural and compressive strengths of over 2 MPa and 8 MPa, respectively. Furthermore, thermal conductivity was reduced by up to 10%, resulting in a thermal resistance of 0.77 (m²·K)/W when employed as prefabricated blocks for interior partition walls in residential buildings. Furthermore, the environmental impact analysis, covering the cradle-to-site life cycle, showed a reduction in impact across all assessed categories, including up to 22% in CO₂ eq. emissions. These results support the suitability of using plastic waste in the manufacture of gypsum-based prefabricated elements and demonstrate that this alternative constitutes a technically and environmentally viable solution. Full article

A circular economy for polyethylene terephthalate (PET) aims to achieve complete material recirculation and reduce dependence on fossil-based feedstocks. Among recycling strategies, depolymerization offers the greatest potential for true circularity. This work investigates deep eutectic solvent (DES)-assisted PET depolymerization using a tetrabutylammonium bromide/sulfolane (TBABr/Sulf) system. A four-factor, three-level Box–Behnken design was employed, where reaction time, NaOH concentration, PET/solvent ratio, and water content were selected as independent variables, with PET weight loss as the response. The optimized conditions of 35 min reaction time, 5.9 wt% NaOH, a PET/solvent ratio (g/g) of 0.061, and a 1:1 water-to-DES ratio achieved 97% PET depolymerization and 93.8% TPA recovery. The process achieved a relatively low PET/DES (g/g) utilization ratio of 0.12 and required at least 40% less NaOH than other DES-based alkaline hydrolysis reported in the literature. The identity and quality of the recovered TPA were confirmed by FTIR, NMR, DSC, and elemental analysis. Under microwave-assisted conditions, TBABr/Sulf was successfully reused over three consecutive cycles while maintaining 100% depolymerization efficiency with consistent TPA quality. Collectively, these results demonstrate the technical potential of the proposed DES-assisted PET depolymerization process, particularly in terms of reduced solvent and alkaline requirements, shortened reaction time, and demonstrated solvent recyclability. Full article

The catalytic upcycling of waste polyethylene terephthalate (PET) is a key strategy for both plastic recycling and the high-value conversion of carbon resources. PET has a rigid aromatic backbone, a semi-crystalline morphology, and a complex composition in real waste streams. These properties make its catalytic conversion sensitive to factors such as chemical bond activation, segment accessibility, and mass transfer limitations. This paper systematically summarizes the core scientific issues associated with the catalytic upgrading of PET through a logical research framework. The discussion covers structural characteristics, catalyst design, reaction pathway control mechanism analysis, and high-value product development. This review emphasizes the relationship between the molecular structure and reactivity of PET. It also elaborates the regulatory effects of diverse catalytic functions on selective conversion. These functions involve acid–base sites, metal sites, interfacial structures, and pore structures. Furthermore, this work illustrates the formation mechanisms of typical target products. The discussed products include ring-closed monomers, aromatic chemicals, alicyclic monomers, functionalized derivatives, and fuel precursors. By integrating in situ characterization, kinetic analysis, and theoretical calculations, this review identifies key challenges in current mechanistic research on PET catalytic upgrading. Prospective research directions are also proposed for the future development of highly efficient, stable, and scalable catalytic systems. Full article

The growing demand for high-performance air filtration materials, coupled with increasing concerns over plastic waste accumulation, has accelerated interest in sustainable filtration technologies. Recycled polyethylene terephthalate (r-PET) has emerged as a promising feedstock for electrospun nanofibrous membranes due to the abundance, low cost, and sustainability of this plastic waste feedstock. The filtration performance of r-PET membranes has been demonstrated to be comparable to that of conventional virgin polymer filters. This review critically examines recent developments in electrospun r-PET nanofibrous membranes for air filtration applications, with particular emphasis on the role of membrane morphology in governing filtration performance. Unlike previous reviews that primarily summarize electrospinning techniques or recycled polymer applications, this review critically evaluates how membrane morphology—including fiber diameter, pore architecture, bead-on-string structures, and multilayer configurations—governs filtration performance in electrospun r-PET membranes. Evidence suggests that rational morphological engineering plays a more decisive role than polymer chemistry in overcoming the conventional filtration efficiency–pressure drop trade-off. Finally, future research opportunities in scalable manufacturing, environmentally benign processing, and artificial intelligence-assisted membrane design are discussed to support the development of next-generation sustainable air filtration media. Full article

The increasing accumulation of polyethylene terephthalate (PET) bottles represents a significant environmental challenge due to their high consumption and limited recovery. The purpose of this study was to develop a sustainable alternative for reusing this waste by manufacturing educational test specimens for laboratory exercises in electrical mechanical engineering and industrial engineering programs. The proposed method was based on mechanical recycling and incorporated, as an innovation, a stage for measuring bottle parameters before processing to improve the quality and uniformity of the recycled material. The results were calculated with the participation of 6 students per test type, which showed that 66.66% of the specimens intended for impact tests and 83.33% of those intended for torsion tests exhibited adequate functional performance. Likewise, it was estimated that a weekly production of 1 kg of crushed PET would cover approximately half a week (three days) of laboratory practices, considering the large number of students. Therefore, it could use 60 to 80% of the total consumption during a standard 15-week course, depending on the situation, demonstrating that integrating recycling into academic activities supports the circular economy, reduces the environmental impact of plastic waste, and strengthens students’ practical training and professional skills. Full article

Poly(ethylene terephthalate) (PET) hydrolases have emerged as promising biocatalysts for closed-loop plastic recycling. Among the most efficient enzymes reported to date, LCC-ICCG exhibits exceptional PET-depolymerization performance under industrially relevant conditions. However, the molecular basis for its superior activity relative to engineered PETases such as FAST-PETase and HotPETase remains incompletely understood. Here, we combine microsecond-scale molecular dynamics simulations, quantum mechanical cluster calculations, pre-reaction-state analysis, noncovalent-interaction mapping, and distortion/interaction activation strain analysis to compare LCC-ICCG with FAST-PETase and HotPETase. The simulations show that LCC-ICCG samples catalytically competent pre-reaction-state geometries more frequently, mainly because V212 reshapes the local environment around the scissile ester. This residue relieves steric congestion, supports weak C–H···O guided substrate preorganization, and reinforces both the Asp-His catalytic dyad and the W190-associated pocket architecture. Density functional theory calculations further indicate that this preorganized active site lowers the acylation barrier to 15.5 kcal/mol by reducing substrate distortion and strengthening transition-state interactions. High-temperature simulations show that LCC-ICCG better preserves near-attack geometries at 350 K, linking thermal robustness to sustained catalytic preorganization. Moreover, reciprocal I208V mutations in IsPETase-derived enzymes enrich pre-reaction-state populations, supporting the transferability of the V212-centered design principle. Overall, these results establish pre-reaction-state stabilization as a key determinant of PET-hydrolase efficiency and provide mechanistic design rules for engineering next-generation PET depolymerases. Full article

Chemical glycolysis can convert waste poly(ethylene terephthalate) (PET) into bis(2-hydroxyethyl) terephthalate (BHET), but recyclable heterogeneous catalysts derived from circular carbon sources and showing low metal release remain limited. Here, post-consumer expanded polystyrene (EPS) was transformed into a hypercrosslinked polymer (HCP) and carbonized with Fe to produce Fe@graphitic-carbon (Fe@C) catalysts for PET glycolysis. The catalysts are denoted mFe@EPS-HCP₈₀₀, where m represents the nominal Fe loading (wt.%), and 800 is the carbonization temperature (°C). The optimized 5Fe@EPS-HCP₈₀₀ contained graphitic carbon layers, bamboo-like carbon nanotube (CNT) domains, hierarchical porosity, and Fe-rich domains associated with graphitic carbon coverage. Under atmospheric-pressure conditions (PET, 2.00 g; ethylene glycol, 20.00 g; catalyst, 0.20 g; 200 °C; 2 h), it achieved complete PET conversion and 94.6% BHET yield. The catalyst also maintained BHET yields of ca. 90–94% over ten reuse runs, and post-reaction microscopy confirmed the retention of graphitic carbon layers and Fe-containing domains. Fe was below the detection limit in the product solutions for the 1, 3, and 5 wt.% Fe catalysts, whereas 7Fe@EPS-HCP₈₀₀ released 9.1 mg kg⁻¹ Fe, consistent with incomplete carbon coverage at excessive Fe loading. Conversion profiles followed an Avrami–Erofeev/Weibull model, giving an apparent activation energy of 205.6 kJ mol⁻¹. The data support a two-stage pathway in which external graphitic carbon/CNT domains promote primary PET chain scission to soluble oligomers, followed by Fe@C interfacial secondary glycolysis to BHET. This work demonstrates dual waste-polymer valorization by using EPS waste as catalytic infrastructure for PET chemical recycling. Full article

This study evaluated the chemical and mechanical stability of recycled polyethylene terephthalate (rPET) fibers produced by rotary die extrusion under selected aqueous exposure conditions. The rPET fibers, natural wool, cotton batting, and a polyester and cotton apparel fabric were exposed to powder detergent, liquid soap, bleach, and dilute hydrochloric acid for periods ranging from 2 h to 7 days. Mass retention was assessed for all materials, whereas tensile properties were evaluated only for rPET. The rPET fibers retained between 99.92 and 100% of their initial mass and more than 95% of their initial tensile strength after 7 days of exposure. Wool showed its greatest mass loss in bleach, while cotton batting and apparel fabric showed measurable mass losses under specific exposure conditions. These reference materials differed in composition and physical form and were therefore used only to provide descriptive context. Overall, the results indicate high mass retention and tensile property retention of the investigated rPET fibers under static exposure at 25 °C. The findings support their potential use in textile applications requiring resistance to the tested aqueous environments but do not establish molecular chain integrity or equivalence with virgin PET. Full article

Poly(ethylene terephthalate) (PET) waste management faces challenges as mechanical recycling limitations become apparent under strict EU regulations. This review critically evaluates PET glycolysis as a vital chemical recycling method, focusing on overcoming barriers to industrial implementation. While systematizing knowledge on reaction mechanisms and parameters, a significant research gap is identified: the necessity for utilizing a high initial mass fraction of waste PET in the reaction feed. Specifically, exceeding a critical concentration of PET-derived oligomers in the resulting glycolysis reaction mixture (typically when the initial waste PET input is above 40% by mass) inevitably triggers phase instability and secondary crystallization during storage. This instability at high concentrations is fundamentally driven by the altered oligomer molecular-weight distribution and the thermodynamic supersaturation of rigid aromatic segments upon cooling. Traditional laboratory approaches using a high excess of glycolyzing agent fail to meet industrial stability demands for subsequent polyester polyol synthesis. Currently, preventing crystallization relies on costly branched glycols or modifiers to disrupt molecular symmetry. This article highlights the urgent need for alternative, additive-free methods to achieve phase stability, such as the elimination of released ethylene glycol from the reaction environment. By addressing shortcomings in glycolysate shelf-life studies, this review charts innovative directions for developing technologies that convert high concentrations of waste PET into phase-stable glycolysates. Full article

Vulnerable coastal urban margins face overlapping pressures from erosion, climate change, and plastic-waste accumulation. This study presents a screening-level numerical assessment of a hollow modular unit made of a recycled polyethylene terephthalate (PET)–concrete composite, proposed for coastal slope protection and stabilisation in Chucuito, Callao, Peru. A limit-equilibrium baseline indicates that the unprotected slope is marginal to unstable under the site’s seismic demand, motivating the evaluation of a surface-protection concept through a parallel, one-way finite element analysis–computational fluid dynamics (FEA–CFD) framework applied at three slope angles (60°, 53°, 45°). The FEA structural-response screening indicates consistent trends across configurations under an equivalent impact load and the adopted basal restraint. For the hydraulic comparison, inlet velocities of 3, 5 and 7 m/s were anchored to the site-specific Delft3D inundation modelling (site maximum 5 m/s), with a conservative 10 m/s upper bound; relative to a rip-rap reference, the hollow configuration suggests midpoint run-up velocity reductions of approximately 52% at θ = 53° under the conservative scenario and ≈57% at 3 and 5 m/s, falling to ≈25% at 7 m/s with overlapping ranges and the simulated free surface exceeding the crest. The CFD free-surface elevations show order-of-magnitude consistency with an indicative EurOtop-based run-up benchmark used as a consistency check rather than as hydraulic validation. Independent of this hydraulic comparison, the hollow geometry saves ≈ 62% of the material volume relative to an equivalent solid concrete block, valorises ≈ 793 post-consumer PET bottles per unit at a 10% dosage, and suggests a 42–58% embodied-CO₂ reduction relative to the same solid-concrete reference, driven mainly by the hollow geometry rather than by the PET substitution itself. The results are internally consistent but not experimentally validated and are intended as a comparative baseline to guide subsequent experimental and field studies, in line with Sustainable Development Goals (SDG) 11, 12 and 13. Full article

Decarbonizing the process heat required for chemical recycling would improve the environmental performance of plastic-waste valorization. This study presents an evaluation of the use of concentrated solar thermal energy as the reaction heat source for the hydrothermal depolymerization of post-consumer polyethylene terephthalate (PET). The solar-driven hydrothermal process (HTP-S) maintained an internal reactor temperature of approximately 200 °C for 4 h under favorable irradiance conditions. During the single experimental run, the system received 14.95 MJ of incident solar energy, whereas the conventional hydrothermal process (HTP-C) consumed 47.52 MJ of electricity per run. Starting from 1.2 g of PET, HTP-C and HTP-S produced 0.862 and 0.895 g of dry recovered solid, corresponding to recovered-solid yields of 71.7% and 74.5%, respectively. Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis and derivative thermogravimetry (TGA/DTG), transmission electron microscopy (TEM), and X-ray diffraction (XRD) showed that the recovered solids exhibit physicochemical characteristics consistent with the formation of a crystalline terephthalic acid (TPA)-rich product. A cradle-to-gate life cycle assessment normalized to 1 kg of treated PET showed that cumulative energy demand decreased from 44,383.7 MJ for HTP-C to 7342.5 MJ for HTP-S, while global warming impacts decreased from 9717 to 1607 kg CO₂-eq. These results demonstrate the technical feasibility of coupling concentrated solar heating with hydrothermal PET depolymerization and identify reaction heating as the principal opportunity for reducing external electricity demand. These outcomes indicate that solar-powered hydrothermal processing provides a feasible pathway for PET recycling, reducing the environmental footprint. Full article

The recycling of post-industrial multilayer polyethylene terephthalate (mPET) packaging waste remains a major challenge due to the coexistence of incompatible polymeric phases and the deterioration of properties during reprocessing. In this work, different reactive compatibilization strategies were evaluated to improve the processability and performance of recycled multilayer PET scraps generated during industrial packaging manufacturing processes. Several functional compatibilizers were investigated, including poly(ethylene-co-acrylic acid) (EAA), poly(ethylene-alt-maleic anhydride) (EMA), poly(ethylene-co-glycidyl methacrylate) (EGMA), poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) (EMAGMA), and maleic anhydride (MA). The influence of compatibilization on the thermal, mechanical, chemical, surface, and morphological properties of recycled mPET was systematically analyzed. Processing behavior revealed that EMA- and MA-based formulations could not be successfully injection molded. In contrast, EAA-, EGMA-, and EMAGMA-based formulations showed suitable processability and enabled the production of defect-free specimens. Thermogravimetric analysis revealed only minor changes in thermal degradation behavior after compatibilization. In contrast, differential scanning calorimetry revealed changes in the melting behavior of the recycled formulations, while tensile and impact tests demonstrated marked improvements in ductility and toughness for EGMA- and EMAGMA-modified systems. Among them, EMAGMA provided the highest elongation at break and impact resistance. Contact angle measurements showed moderate changes in surface wettability, whereas density and hardness remained largely unaffected. FESEM analysis revealed a more homogeneous phase distribution and reduced dispersed-domain size in the compatibilized formulations, particularly for EGMA, indicating improved interfacial compatibility. These results demonstrate that glycidyl methacrylate-based compatibilizers are effective reactive agents for upgrading post-industrial multilayer PET waste into higher-performance recycled materials for different applications. Full article

Plastic packaging is indispensable in modern food and beverage supply chains. However, its production and end-of-life management require substantial primary energy inputs. Improving the energy efficiency of packaging systems is therefore a key objective of circular economy strategies. This study applies Life Cycle Assessment (LCA) to evaluate the cumulative energy demand (CED) of a beverage packaging system comprising polyethylene terephthalate (PET) bottles, recycled polyethylene terephthalate (rPET) bottles, high-density polyethylene (HDPE) caps, and polypropylene (PP) labels under two end-of-life scenarios: recycling and landfilling. The assessment was performed using Polish production and waste-management conditions (2022–2024). A functional unit of 100,000 complete 1 L beverage packages was adopted, and the life cycle inventory combined primary industrial data with background datasets from the ecoinvent database. Recycling scenarios were modelled using a substitution-based allocation (system expansion) approach. The results indicate that non-renewable energy accounted for approximately 88–97% of the total cumulative energy demand of the analysed packaging components. Among the investigated materials, PP labels exhibited the highest component-specific cumulative energy demand, whereas rPET bottles showed the lowest values, corresponding to an approximately 13% lower energy demand than conventional PET bottles under the adopted modelling assumptions. Recycling consistently outperformed landfilling by reducing cumulative primary energy demand across all analysed impact categories, with the greatest energy-saving potential observed for PP labels. Negative CED values obtained for selected recycling scenarios represent avoided primary energy resulting from virgin material substitution rather than physically negative energy consumption. The findings demonstrate that component-level LCA provides a robust basis for identifying energy hotspots within plastic packaging systems and supports evidence-based decisions regarding eco-design, material selection, and recycling strategies. Although the absolute CED values are specific to Polish production and recycling conditions, the overall results confirm that material recycling is a more energy-efficient end-of-life strategy than landfilling and contributes to the development of more sustainable circular packaging systems. Full article

Polyethylene terephthalate (PET) is a common plastic widely used in food packaging, especially plastic bottles, and in fibers and textiles. The widespread use of PET and its intentional and unintentional release and disposal over the past few decades have placed significant pressure on the environment, necessitating the development of green, low-cost, and efficient recycling technologies to mitigate this impact. This article reviews recent advances in microwave-assisted catalytic depolymerization of PET. It begins by outlining the fundamental principles of PET materials science and depolymerization mechanisms. The article then reviews the historical evolution of this research and presents a benchmark comparison of different depolymerization methodologies. Finally, through a critical analysis and comparison of state-of-the-art approaches, the article identifies emerging trends and highlights promising directions for future research in the field. A comprehensive comparison of conventional and microwave heating methods is presented, indicating that catalyst-assisted microwave systems can shorten reaction times and achieve high product yields under optimized conditions. Key advantages and limitations are highlighted, and persistent challenges are discussed. Overall, this article surveys the latest progress in the chemical recycling of PET and provides critical insights for future research and further development of microwave-assisted catalytic PET depolymerization technology. Full article

Polyethylene terephthalate (PET) is one of the most widely used synthetic plastics and a major contributor to global plastic pollution because of its high resistance to degradation. Enzymatic degradation by PET hydrolases (PETase) has emerged as a sustainable strategy for PET recycling; however, the limited thermostability of wild-type PETase restricts its industrial application. To elucidate the molecular basis underlying the different thermal behaviors of PET hydrolases, long-timescale molecular dynamics simulations were performed on WT-PETase, FAST-PETase, and the thermostable cutinase variant LCC-ICCG at 30 °C, 50 °C, and 70 °C. Comparative analyses integrating structural stability, residue flexibility, rigidity networks, free energy landscapes, and neural relational inference models revealed that FAST-PETase and LCC-ICCG exhibited enhanced conformational stability and reduced structural flexibility compared with WT-PETase, particularly under elevated temperatures. The improved thermostability was associated with more compact free energy landscapes, strengthened residue interaction networks, and better preservation of the catalytic architecture during thermal perturbation. These results suggest that an optimal balance between structural rigidity and conformational flexibility is critical for maintaining enzyme stability at elevated temperatures. Overall, this study provides molecular-level insights into the structural determinants of PETase thermostability and offers a theoretical framework for the rational engineering of efficient and heat-resistant plastic-degrading enzymes. Full article