Search Results (274)

Micro- and nanoplastics (MNPs) are increasingly recognized as emerging contaminants in drinking water, yet quantitative data remain limited due to analytical challenges. In this study, the occurrence, morphology, and polymer composition of MNPs were investigated in commercial drinking water from Saxony-Anhalt, Germany, including ultrapure water, tap water, and five bottled mineral waters. A dual-stage cascade filtration system combining silicon filters (5 µm pore size) and aluminum oxide membranes (90 nm pore size) was employed for size-selective particle separation. Retained particles were characterized using optical microscopy, scanning electron microscopy (SEM), and Raman spectroscopy. Tap water exhibited the highest concentration of microparticles, whereas ultrapure water showed minimal microparticle contamination. Nanoparticles were detected in all samples, including ultrapure water, with mean particle sizes below 1 µm, highlighting the pervasive nature of nanoscale plastic contamination. Raman analysis identified polyethylene terephthalate (PET) as the most frequently detected synthetic polymer, together with polypropylene (PP), polystyrene (PS), and poly(methyl methacrylate) (PMMA). The results demonstrate that no drinking water source tested in this study was free of detectable MNPs and underline the need for standardized analytical approaches capable of reliably detecting MNPs in drinking water. 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

Previous studies have indicated that polyethylene terephthalate (PET) micro/nanoplastics (MNPs) may coexist with antibiotics in environmental and biological matrices; however, their combined behavior in blood remains insufficiently characterized. This study examined PET MNPs prepared from water bottles at 0.5, 2.5, and 7.5 mg/mL together with tetracycline (2–50 µg/mL) in defibrinated horse blood. After 24 h exposure and particle removal, UV–visible absorbance, intrinsic fluorescence, redox indicators, and subsequent Escherichia coli responses were evaluated. The blood biochemical results showed condition-dependent changes in hemoglobin-associated absorbance, tryptophan-dominated fluorescence, reactive oxygen species, reduced glutathione, superoxide dismutase, and lipid peroxidation. When treated blood supernatants were applied to Escherichia coli, tetracycline alone reduced bacterial OD600, whereas selected PET MNP–tetracycline co-exposures partially restored bacterial proliferation and modified oxidative-stress responses. ATR–FTIR analysis of Escherichia coli pellets showed dose-dependent modulation of phosphate-, lipid-, and protein-associated bands, indicating changes in bacterial biochemical fingerprints under specific exposure combinations. Overall, the findings suggest that PET MNPs can modify tetracycline-associated spectral, redox, and bacterial response patterns in a blood matrix. Future studies incorporating adsorption assays, free tetracycline quantification, protein-corona profiling, time-course exposure designs, and antibiotic susceptibility testing would further clarify the mechanistic basis and biological relevance of these matrix-dependent interaction effects. 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

MP contamination in drinking water is an emerging public health concern, yet standardized analytical workflows and exposure assessments remain limited and fragmented. This study provides an exploratory assessment of MP exposure through drinking water, combining particle-resolved analysis with consumption-based estimates. Laser Direct Infrared (LDIR) spectroscopy was applied within the analytical workflow to characterize MPs across different drinking water supply types. Ten drinking-water samples (five bottled, two tap, two public dispensers, and one office dispenser) were analyzed within a 10–500 µm size window, and particle-resolved results were combined with a consumption survey to support preliminary exposure estimates. MPs in the 10–150 µm range were detected in six of ten samples, while tap waters and all blanks were particle-free, supporting analytical robustness. Bottled waters showed the highest MP abundances (6–148 particles L⁻¹) and mass concentrations (0.03–22.4 µg L⁻¹). Particle-size distributions were right-skewed and dominated by particles ≤ 30 µm. PET, PU, PA, and ABS predominated, consistent with packaging and dispensing origins. EDI estimates for bottled-water consumers ranged from 0.1008 to 0.3023 µg kg-bw⁻¹ day⁻¹ across three consumption scenarios (1–3 L day⁻¹). Despite the limited sample size, the results support LDIR for source discrimination and exposure screening, providing a basis for future research. 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

Tactile sensing can enhance robotic grasping by providing contact information unavailable from vision or control signals alone. However, implementing tactile sensing in robotic hands is often constrained by external wiring, data-acquisition hardware, power requirements, and limited fingertip space. This study presents a self-contained capacitive tactile fingertip module for adding wireless multi-point contact sensing to robotic grippers. The module integrates a 3 × 1 array of thin flexible capacitive sensors, a capacitance-to-digital converter, a Bluetooth-enabled microcontroller, and an onboard battery within a compact fingertip-shaped housing. It can be mounted in place of an existing fingertip and operates independently of the robotic hand controller. Individual sensors characterized before module integration responded near-linearly to normal compression up to 2.5 N, with an approximately 8% relative capacitance change at 2.5 N and R² = 0.99, and were evaluated over 100 repeated compression cycles. In proof-of-concept grasping tests with an empty PET bottle, a water-filled PET bottle, and a water-filled aluminum tumbler, the assembled module produced distinguishable capacitance changes at the mid- and proximal-position sensors, providing relative information on contact location and local loading rather than calibrated force. These results demonstrate the feasibility of wireless tactile sensing in robotic grasping using a compact standalone fingertip module. Full article

The construction sector is responsible for approximately 38% of global CO₂ emissions, driven primarily by energy demand for thermal comfort. This research evaluated the implementation of a Passive Climate Control System (PCCS) based on circular economy principles. This system acts as a thermal buffer composed of recycled PET bottles filled with 500 mL of water and a reflective coating, installed on the roof slab. Through a case–control study in Veracruz, Mexico, hygrothermal performance was monitored for ten months. The results demonstrated the superiority of the PCCS over the conventional slab: in autumn–winter, temperature fluctuations were reduced by 26.7%, while in spring–summer, the maximum temperature was limited by 1.3 °C during the daytime peak. Fractal analysis confirmed that the PCCS promotes a homogeneous thermal distribution (Fd ≤ 1.255), maintaining internal conditions within the comfort zone. The implementation of this PCCS, based on waste valorization, is a robust and sustainable solution that offers a viable alternative to active climate control. It promotes hygrothermal comfort and reduces energy consumption, aligning with the objectives of Clean Technology and building efficiency. Full article

Designing sustainable closed-loop supply chain (CLSC) networks requires jointly assessing node-level operational attributes (recovery efficiency, processing capacity, unit cost) and inter-node spatial structure. Existing methods, including mixed-integer programming, multi-objective metaheuristics, and graph-matching, typically optimize a single cost dimension and do not decompose structural connectivity from attribute-level inefficiency. We propose a Fused Gromov–Wasserstein (FGW) diagnostic framework that combines the Wasserstein distance (attribute similarity) and the Gromov–Wasserstein distance (structural alignment) via a convex trade-off parameter α, solved using the conditional gradient algorithm. Supply–capacity imbalances are resolved by marginal rescaling, with residual unabsorbed mass reported as a diagnostic indicator of infrastructure shortfall. The framework is applied to an eight-echelon PET bottle recovery and filament manufacturing network across 24 synthetic benchmark instances at three scale classes. The FGW cost decomposes exactly into feature and structural components, allowing bottleneck arcs to be diagnosed as attribute-driven or structure-driven. Under this benchmark, bottleneck cost decreases with network size, the most frequent bottleneck arc shifts from the collection interface in small networks to the mid-chain processing handoff in large networks, and attribute heterogeneity accounts for the majority of FGW cost (57.9%, conditional on the normalization and weighting scheme used) across all 144 arc–instance combinations. These results position FGW as a tractable, interpretable diagnostic layer for circular supply chain analysis, complementing rather than replacing classical CLSC design models. Full article

This study presents finite element investigations on the use of polyethylene terephthalate (PET) bottles as void formers in reinforced concrete columns subjected to pure axial compression. The incorporation of PET bottles in reinforced concrete structures reduces concrete consumption while also providing a sustainable disposal solution for used PET bottles. In addition, for the same amount of concrete used in equivalent solid and voided columns, the voided column can exhibit greater flexural capacity due to the increased moment arm of the longitudinal reinforcement. In this study, a finite element-based parametric study is conducted on reinforced concrete columns containing voids within the core. The model was validated using the results of an experimental testing program consisting of 16 scaled reinforced concrete columns, of which 8 specimens had solid cross-sections and 8 specimens had hollow cross-sections. The numerical study considered variations in the longitudinal reinforcement ratio, tie spacing, concrete compressive strength and shape of cross-section. The finite element analyses were conducted using ABAQUS with consideration of material nonlinearity, and the results showed good agreement with the experimental findings. Furthermore, a parametric study was performed to quantify the effects of concrete compressive strength, longitudinal and transverse reinforcement ratios, void diameter, and column cross-sectional dimensions on the load-carrying capacity, ductility, stiffness, and residual strength of the columns. The findings of the study demonstrated that introducing voids formed by tightly stacked PET bottles within the core of reinforced concrete tied columns does not adversely affect their structural behavior under axial compressive loading, as the response of the voided columns was found to be comparable to that of their solid counterparts. The parametric study demonstrated that concrete compressive strength and longitudinal reinforcement ratio significantly influenced the load-carrying capacity and stiffness of voided columns, whereas tie spacing and void diameter had comparatively moderate effects, and changing the column shape while maintaining the same cross-sectional area as the equivalent solid section had negligible influence on the overall structural performance. Full article

Microplastic (MP) pollution in bottled and tap water poses escalating environmental and public health challenges due to MPs’ capacity to act as vectors for toxicants and pathogens. This study constitutes the first comprehensive evaluation of MPs in drinking water from Madeira Island, integrating detailed chemical and morphological characterisations alongside human exposure estimations. A total of 22 samples, comprising 10 bottled (four mineral, six flavoured) and 12 tap waters, were analysed via stereomicroscopy and micro-Fourier transform infrared (µ-FTIR) spectroscopy. Of the 428 particles detected, 65 were confirmed MPs, 223 were non-plastics, and 140 were indeterminate. Bottled waters were predominantly contaminated by polyethylene terephthalate (PET), polypropylene (PP), and polyethylene (PE), whereas tap waters exhibited a notable presence of PE, PP, polyester, and polyamide (PA). MPs predominantly measured under 400 µm and were transparent; fragments were the main form in bottled water, contrasting with fibres dominating tap waters. Concentrations ranged from 0.5 to 6 MPs/L, with flavoured waters exhibiting the highest average levels (2.00 ± 1.83 MPs/L), followed by tap (1.30 ± 0.80 MPs/L) and mineral waters (0.59 ± 0.37 MPs/L). Estimated daily intake (EDI) spanned 0.01–0.19 MPs/kg/day for adults and 0.05–0.68 MPs/kg/day for children, the latter exhibiting a 3.6-fold greater exposure. Although concentrations were lower than those in many global reports, the ubiquity of MPs underscores the critical need for standardised monitoring protocols, enhanced production standards, and rigorous risk assessments addressing chronic low-level human exposure, especially in insular environments. Full article

Aerogels were produced exclusively from recycled plastic bottles of poly(ethylene terephthalate) (rPET) by optimising a dissolution–precipitation process at room temperature and applying a product design strategy to improve their sustainability. Using a design of experiments methodology, the systematic assessment of the influence of different factors, namely rPET concentration, co-solvent ratio, and non-solvent quantity, on the key properties of rPET aerogel, namely bulk density, thermal conductivity, and mechanical resistance, was performed. The understanding of the significance of each parameter and the optimisation of a desirability function offered reliable optimum results for the adjustment of the experimental procedure for the reduction in the volume of the most critical solvent, trifluoroacetic acid (TFA), by 42.5%. The observed bulk density values were excellent, down to 110 kg·m⁻³, and the thermal conductivity was in the range of conventional commercial insulators (38 mW·m⁻¹·K⁻¹), positioning this material as a real alternative to conventional thermal insulators. Also, to deeply understand the dissolution/precipitation phenomena, molecular dynamics simulations were conducted to support the experimental outcomes. Full article

The utilization of polyethylene terephthalate (PET) waste from single-use packaging offers potential for sustainable manufacturing. This study evaluates recycled PET (rPET) from bottles as an FDM filament by varying infill architectures (honeycomb, gyroid, grid, and triangles) and layer thicknesses (0.20, 0.25, and 0.30 mm), with commercial PETG as a benchmark. Compared with previous rPET FDM studies, which were limited to reporting mechanical strength, the novelty of this study lies in the fact that it not only reports mechanical strength performance, but also compares printing time requirements and material efficiency. Efficiency calculations are obtained by comparing the weight of the filament to the weight of the printed specimen, which then correlates with optimizing processing time and costs. Overall, rPET produced densities of 1.11–1.22 g/cm³, tensile strengths of 12.5–22.5 MPa, flexural strengths of 12.5–30 MPa, impact strengths of 0.032–0.060 J/mm², and surface roughnesses of Ra 5.2–7.1 μm, while PETG showed higher mechanical performance (tensile 30–39.5 MPa, flexural 30–50 MPa, impact 0.037–0.065 J/mm²) and comparable density (1.15–1.27 g/cm³). Within rPET, gyroid provided the best optimal performance; the gyroid (0.20 mm) variation achieved the highest impact response (0.060 J/mm²) and the lowest Ra (5.2 μm) and the gyroid (0.25 mm) variation maximized flexural strength (30 MPa) and the gyroid (0.30 mm) variation maximized tensile strength (22.5 MPa). Material utilization efficiency was consistently higher for rPET (65–68%) than for PETG (46–56%). These results provide an integrated rPET-specific assessment and practical parameter recommendations for functional 3D printing, while also aligning with SDG 12 by pro-moting resource-efficient circular-economy practices through the utilization of waste materials in additive manufacturing. Full article

The recycling of polyethylene terephthalate (PET) into value-added products suitable for additive manufacturing remains challenging due to molecular degradation and insufficient melt strength. In this study, post-consumer recycled PET was upcycled via chain extension to develop filaments suitable for fused filament fabrication (FFF). Two chain extenders were evaluated: an epoxy-based multifunctional oligomer (Joncryl^® ADR-4468) and a tetrafunctional aromatic dianhydride (pyromellitic dianhydride, PMDA). Joncryl^® ADR-4468 increased the complex viscosity and viscoelastic moduli of rPET; however, the response was non-monotonic and resulted in limited filament dimensional stability. In contrast, rPET/vPET (70/30) blends modified with PMDA exhibited a pronounced and reproducible enhancement in melt viscosity and elasticity, enabling the production of a continuous filament with a stable diameter (1.75 ± 0.05 mm). Differential scanning calorimetry indicated that PMDA had a negligible effect on the glass transition temperature, while slightly reducing crystallinity, which is beneficial for FFF processing. Preliminary printing trials confirmed stable extrusion and controlled deposition behaviour for the PMDA-modified formulation. Overall, the results demonstrate that chain extension using PMDA is an effective strategy to restore melt processability and enable the use of recycled PET in filament-based additive manufacturing. Full article