Search Results (369)

Geopolymers, as an eco-friendly alternative construction material to ordinary Portland cement (OPC), exhibit superior performance in soil stabilization. However, their inherent brittleness limits engineering applications. To address this, polyethylene terephthalate (PET) fibers can be incorporated into a one-part geopolymer (OPG) binder to enhance ductility while promoting plastic waste recycling. However, the evaluation of ductile behavior of OPG-stabilized soil with PET fiber normally demands extensive laboratory and field experiments. Leveraging artificial intelligence, a predictive model can be developed for this purpose. In this study, data were collected from compressive and tensile tests performed on the OPG-stabilized soil with PET fiber. Four deep learning neural network models, namely ANN, BPNN, CNN, and LSTM, were then used to construct prediction models. The input parameters in the model included the fly ash (FA) dosage, dosage and length of the PET fiber, and the Curing Time. Results revealed that the LSTM model had the best performance in predicting the three ductile properties (i.e., the compressive strength index [UCS], strain energy index [CSE], and tensile strength index [TES]). The SHAP and 2D-PDP methods were further used to verify the rationality of the LSTM model. It is found that the Curing Time was the most important factor for the strength and ductile behavior. The appropriate addition of PET fiber of a certain length had a positive impact on the ductility index. Thus, for the OPG-stabilized soil, the optimal dosage and length of PET fiber were found to be 1.5% and 9 mm, respectively. Additionally, there was a synergistic effect between FA and PET on the ductility metric. This research provides theoretical support for the application of geopolymer and PET fiber in enhancing the ductility of the stabilized soil. Full article

Alkali-activated building materials have attracted the interest of many researchers due to their low cost and eco-efficiency. Different binders with different chemical compositions can be used for their production, so the reaction mechanism can become complex and the results of studies can vary widely. In this work, several alkali-activated mortars based on marginal by-products as binders, such as high calcium fly ash and ladle furnace slag, are investigated. Their mechanical (flexural and compressive strength, ultrasonic pulse velocity, and modulus of elasticity) and physical (porosity, absorption, specific gravity, and pH) properties were determined. After evaluating the mechanical performance of the mortars, the optimum mixture containing fly ash, which reached 15 MPa under compression at 90 days, was selected for the production of precast compressed slabs. Steel or glass fibers were also incorporated to improve their ductility. To reduce the density of the slabs, 60% of the siliceous sand aggregate was also replaced with recycled polyethylene terephthalate (PET) plastic aggregate. The homogeneity, density, porosity, and capillary absorption of the slabs were measured, as well as their flexural strength and fracture energy. The results showed that alkali activation can be used to improve the mechanical properties of weak secondary binders such as ladle furnace slag and hydrated fly ash. The incorporation of recycled PET aggregates produced slabs that could be classified as lightweight, with similar porosity and capillary absorption values, and over 65% achieved strength compared to the normal weight slabs. Full article

The rapid growth in plastic consumption, particularly polyethylene terephthalate (PET), has led to a significant increase in plastic waste, posing a major environmental challenge. Developing an integrated circular economy framework for nanomaterial-enhanced recycled PET (nrPET) can be a promising approach to address this issue and advance sustainable and resilient road construction practices. This comprehensive review examines the current use of rPET in road construction, its existing limitations, and the role of nanomaterials in enhancing the performance of these materials. The review explores the mechanisms by which nanomaterials, such as carbon nanotubes, graphene, nanosilica, and clay nanoplatelets, can improve the properties of rPET, leading to more durable, weather-resistant, and cost-effective road materials. Furthermore, the review analyzes the environmental and sustainability benefits of using nrPET in road construction, focusing on carbon footprint reduction, conservation of natural resources, and alignment with circular economy principles. The potential for job creation, social benefits, and support for circular economy initiatives are also discussed. The review then delves into the challenges associated with the implementation of this framework, including technical barriers, economic and market barriers, regulatory and policy challenges, and environmental and safety considerations. Strategies to address these challenges, such as advancements in nanotechnology, scaling up circular economy models, and fostering collaborative research, are presented. Finally, the article proposes a framework and outlines future directions and research opportunities, emphasizing the exploration of emerging nanomaterials, scaling up circular economy models, and encouraging collaborations between researchers, industry stakeholders, policymakers, and communities. Full article

This research aimed to evaluate the biological resistance to xylophagous organisms and the dimensional stability related to water absorption in plastic wood panels manufactured by compression molding and produced with pine wood and recycled thermoplastics. The wood–plastic composites (WPCs) were prepared from 50% pine sawdust and 50% recycled plastics (polyethylene terephthalate-PET, high-density polyethylene-HDPE, and polypropylene-PP). The thickness swelling test was carried out by immersing of the WPC samples in water at room temperature (25–30 °C) and evaluating the total change in WPC thickness after 1500 h (≈9 weeks or two months). In addition, the coefficient of initial swelling was evaluated to verify the variability of the swelling. For the biological resistance evaluation of the WPCs, tests were carried out with soil or arboreal termites (Nasutitermes corniger) and drywood termites (Cryptotermes brevis). The WPC loss of mass and termite mortality were evaluated. The use of PP promoted the best response to thickness swelling. The simple mathematical model adopted offers real predictions to evaluate the thickness of the swelling of the compounds in a given time. For some variables there were no statistical differences. It was shown that treatment 3 (T3) presented visual damage values between 0.4 for drywood termites and 9.4 for soil termites, in addition to 26% termite mortality, represented by the lowest survival time of 12 days. The developed treatments have resistance to termite attacks; these properties can be an important starting point for its use on a larger scale by the panel industries. Full article

Polyethylene terephthalate (PET) pollution represents a significant environmental challenge due to its widespread use and recalcitrant nature. PET-degrading enzymes, particularly Ideonella sakaiensis PETases (IsPETase), have emerged as promising biocatalysts for mitigating this problem. This review provides a comprehensive overview of recent advancements in the discovery and heterologous expression of IsPETase and closely related enzymes. We highlight innovative approaches, such as in silico and AI-based enzyme screening and advanced screening assays. Strategies to enhance enzyme secretion and solubility, such as using signal peptides, fusion tags, chaperone co-expression, cell surface display systems, and membrane permeability modulation, are critically evaluated. Despite considerable progress, challenges remain in achieving industrial-scale production and application. Future research must focus on integrating cutting-edge molecular biology techniques with host-specific optimisation to achieve sustainable and cost-effective solutions for PET biodegradation and recycling. This review aims to provide a foundation for further exploration and innovation in the field of enzymatic plastic degradation. Full article

EU accession countries, including the Republic of Serbia, are under growing pressure to align their plastic waste management systems with EU environmental directives. Despite this, significant challenges remain, including inadequate infrastructure, a limited recycling capacity, and weak enforcement mechanisms. This study employs life cycle assessment (LCA) to evaluate the environmental impacts of polyethylene terephthalate (PET) packaging waste in Serbia, focusing on three end-of-life scenarios (EoL): landfilling, recycling, and incineration. Using GaBi Professional v6.0 software and the ReCiPe 2016 methodology, the results indicate that mismanaged PET waste contributes notably to terrestrial ecotoxicity (3.69 kg 1.4-DB eq.) and human toxicity (non-cancer) (2.36 kg 1.4-DB eq.). In 2023, 14,967.8 tons of PET were collected by authorized operators; however, unreported quantities likely end up in landfills or the natural environment. Beyond the quantified LCA results, this study highlights microplastic pollution as an emerging environmental concern. It advocates for the development of Serbia-specific characterization factors (CFs) for PET microplastics, incorporating localized fate, exposure, and effect data. Tailored CFs would enhance the precision of impact assessments for Serbian terrestrial ecosystems, contributing to more effective, evidence-based environmental policies. These insights are crucial for supporting Serbia’s transition to sustainable waste management and for meeting EU environmental standards. Full article

Small-particle-produced goods, such as those used in industry, medicine, cosmetics, paints, abrasives, and plastic pellets or powders, are the main sources of microplastics. It is also possible to mention tire recycling granules here. Larger components break down in the environment to generate secondary microplastics. Microplastics, or particles smaller than 5 mm, and nanoplastics, or particles smaller than 1 μm, are the products of degradation and, in particular, disintegration processes that occur in nature as a result of several physical, chemical, and biological variables. Polypropylene, polyethylene, polyvinyl chloride (PVC), polystyrene, polyurethane, and polyethylene terephthalate (PET) are among the chemicals included in this contamination in decreasing order of quantity. Micro- and nanoplastics have been detected in the air, water, and soil, confirming their ubiquitous presence in natural environments. Their widespread distribution poses significant threats to human health, including oxidative stress, inflammation, cellular damage, and potential carcinogenic effects. The aim of this article is to review the current literature on the occurrence of micro- and nanoplastics in various environmental compartments and to analyze the associated health consequences. The article also discusses existing legal regulations and highlights the urgent need for intensified research into the toxicological mechanisms of microplastics and the development of more effective strategies for their mitigation. Full article

The recycling of post-consumer plastics for food-contact applications is subject to stringent regulatory requirements, particularly with regard to the removal of potentially harmful non-intentionally added substances (NIAS). While polyethylene terephthalate (PET) recycling processes are already approved by the European Food Safety Authority (EFSA), there is a lack of guidance for other polymers like polystyrene (PS). This study aims to provide a scientific basis for assessing the decontamination efficiency required for recycled post-consumer PS in food-contact applications. As one of the first studies to propose a framework for PS decontamination assessment based on EFSA food-consumption data and conservative diffusion modeling, it contributes to filling this regulatory gap. First, European food-consumption data were analyzed to identify critical scenarios of the age-group-dependent intake of PS-packaged food. Based on this, a conservative migration model was applied using a one-dimensional diffusion simulation to determine the maximum allowable initial concentrations of NIAS in PS. The calculated values were then compared with published reference contamination levels to calculate the required cleaning efficiency. The combination of food-consumption values and the migration process showed that trays for fruits and vegetables are the most critical food-contact application for post-consumer PS recycling. The most stringent assumptions resulted in necessary decontamination efficiencies ranging from 92% for the smallest molecule, toluene (92.14 g/mol), to 42% for the largest molecule, methyl stearate (298.50 g/mol). The results provide a methodological basis for regulatory assessments and offer practical guidance for designing safe recycling processes, thereby supporting the circular use of PS in food packaging and building the basis for future regulatory assessments of other polymers, in line with the European Union Plastics Strategy and circular economy objectives. Full article

Recycling plastic waste has emerged as one of the most pressing environmental challenges of the 21st century. One of the biggest challenges in polyethylene terephthalate (PET) recycling is the requirement to return bottles in their original, undeformed state. This necessitates storing large volumes of waste and takes up substantial space. Therefore, this paper seeks to address this issue and introduces a novel AIoT-based infrastructure that integrates the PET Bottle Identification Algorithm (PBIA), which can accurately recognize bottles regardless of color or condition and distinguish them from other waste. A detailed study of Azure Custom Vision services for PET bottle identification is conducted, evaluating its object recognition capabilities and overall performance within an intelligent waste management framework. A key contribution of this work is the development of the Algorithm for Citizens’ Trust Level by Recycling (ACTLR), which assigns trust levels to individuals based on their recycling behavior. This paper also details the development of a cost-effective prototype of the AIoT system, demonstrating its low-cost feasibility for real-world implementation, using the Asus Tinker Board as the primary hardware. The software application is designed to monitor the collection process across multiple recycling points, offering Microsoft Azure cloud-hosted data and insights. The experimental results demonstrate the feasibility of integrating this prototype on a large scale at minimal cost. Moreover, the algorithm integrates the allocation points for proper recycling and penalizes fraudulent activities. This innovation has the potential to streamline the recycling process, reduce logistical burdens, and significantly improve public participation by making it more convenient to store and return used plastic bottles. Full article

Non-intentionally added substances (NIAS) in plastic food contact materials represent a critical undercharacterized chemical safety concern, caused by their inherent diversity, potential toxicity, and regulatory challenges. This review synthesizes recent advances and persistent gaps in NIAS analysis, with a primary focus on analytical workflows for non-targeted analysis, alongside a consideration of risk assessment and toxicological prioritization frameworks. Conventional plastics (e.g., polyethylene, polypropylene, or polyethylene terephthalate) as well as emerging materials (e.g., bioplastics and recycled polymers) exhibit different NIAS profiles, including oligomers, degradation products, additives, and contaminants, requiring specific approaches for migration testing, extraction, and detection. Advanced techniques, such as ultra-high-performance liquid chromatography or two-dimensional gas chromatography coupled with high-resolution mass spectrometry, have enabled non-targeted analysis approaches. However, the field remains constrained by spectral library gaps, limited reference standards, and inconsistent data processing protocols, resulting in heavy reliance on tentative identifications. Risk assessment procedures mainly employ the Threshold of Toxicological Concern and classification by Cramer’s rules. Nevertheless, addressing genotoxicity, mixture effects, and novel hazards from recycled or bio-based polymers remains challenging with these approaches. Future priorities and efforts may include expanding spectral databases, harmonizing analytical protocols, and integrating in vitro bioassays with computational toxicology to refine hazard characterization. Full article

Polymer residues can be reused in civil construction by partially replacing mineral aggregates in concrete, thereby reducing the extraction of natural resources. This study aimed to evaluate the use of powdered poly (ethylene terephthalate) (PET) and polyethylene (PE) residues, accumulated in shaving-mill filters during the extrusion of multilayer films used in food packaging, in the production of sealing masonry blocks. The PET/PE residues were characterized by Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Cylindrical specimens were produced in which part of the sand, by volume, was replaced with 10, 20, 30, 40 and 50% polymer residue. The cylindrical specimens were evaluated for specific mass, water absorption and axial and diametral compressive strengths. The 10% content provided the highest compressive strength. This formulation was selected for the manufacture of concrete blocks, which were evaluated and compared with the specifications of ABNT NBR 6136:2014. The concrete blocks showed potential for applications without structural function and were classified as Class C. The results, in line with previous investigations on the incorporation of plastic waste in concrete, underscore the promising application potential of this strategy. Full article

The environmental burden of textile waste has become a critical challenge for sustainable development. This review explores recent developments in the recycling of textiles, especially polyethylene tereph-2 thalate (PET)-based fabrics, with a focus on fiber-to-fiber regeneration as a pathway toward circular textile production. Recent developments in PET recycling, such as mechanical and chemical recycling methods, are critically examined, highlighting the potential of chemical depolymerization for recovering high-purity monomers suitable for textile-grade PET synthesis. Special attention is given to electrospinning as an emerging technology for converting recycled PET into high-value nanofibers, offering functional properties suitable for advanced applications in filtration, medical textiles, and smart fabrics. The integration of these innovations, alongside improved sorting technologies and circular design strategies, is essential for overcoming current limitations and enabling scalable, high-quality recycling systems. This review aims to support the development of a more resource efficient textile industry by outlining key challenges, technologies, and future directions in PET recycling. Full article

This study identifies different polymers using their fluorescent data under various light wavelengths that ranged from 245 nm to 345 nm in 10 nm intervals. The primary goal of the proposed method is to select optimal wavelengths that can lead to the accurate identification of six polymers: polyamide 6 (PA6), polymethyl methacrylate (PMMA), polypropylene (PP), polystyrene (PS), high-density polyethylene (HDPE), and polyethylene terephthalate (PET). By examining the specific fluorescence emission patterns of these polymers, the study provides insight into how each material responds uniquely to different excitation light sources. The potential approach could streamline polymer identification in recycling applications or even in quality control and environmental monitoring, including microplastics. This approach could lead to improved accuracy in polymer classification, contributing to more efficient material sorting and processing. Full article

2,5-Furandicarboxylic acid (FDCA) is a bio-based platform chemical with high potential to replace terephthalic acid in polymer production, particularly for polyethylene furanoate (PEF), a biopolymer with superior thermal and barrier properties. This study investigates the selective oxidation of 5-hydroxymethylfurfural (HMF) into FDCA using nickel-based heterogeneous catalysts, aiming at a cost-effective and sustainable alternative to noble metal catalysts. A series of nickel oxide catalysts were synthesized and screened. The NiOx catalyst synthesized without thermal treatment via Route B showed the best performance, achieving a FDCA yield of 11.77%, selectivity of 27.41%, and concentration of 0.9 g/L under preliminary conditions. Reaction kinetics revealed that the controlled addition of NaClO enhanced FDCA yield by 2.28 times. Optimization using a 2³ factorial design identified the optimal conditions as 6% (w/v) catalyst concentration, 25 °C, and a NaClO:HMF molar ratio of 12:1, leading to 34.14% yield and 42.57% selectivity. The NiOx catalyst maintained its activity over five successive cycles, indicating good recyclability. Moreover, NiOx demonstrated catalytic activity with crude HMF derived from glucose dehydration, confirming its practical applicability. These results support the potential of nickel-based catalysts in sustainable FDCA production, contributing to the advancement of bio-based polymer synthesis. Full article

Compressed earth blocks (CEBs) obtained by laterite material geopolymerization have great potential as building materials; however, plastic waste recycling remains an important challenge for the 21st century. Samples of lateritic materials (LAT) from the locality of Kompina and its surroundings (Littoral-Cameroon) were collected, given the region’s association with polyethylene terephthalate powder (P). They were used to make geopolymeric laterite bricks using a phosphoric acid solution (A) concentrated at 10 mol/L, at a fixed value of 20% phosphoric acid, and values of 0, 5, 10, 15, and 20% polyethylene terephthalate (PET) powder. To assess the suitability of these formulations for construction, the CEBs were tested and their physico-mechanical and thermal characteristics determined, including water absorption rate, compressive strength (CS), thermal conductivity, and effusivity. It was revealed that water absorption decreased for the LAT1 and LAT6 formulas, at 6.73% and 5.01%, respectively, with the lowest value being recorded when 10% of the PET powder was used. The water absorption increased beyond this percentage; the CS values did too, with a peak at 10% PET powder, reaching 6.92 MPa and 6.96 MPa for LAT1 and LAT6, respectively, and values decreasing beyond this point. The thermal conductivity and effusivity decreased, with the lowest values at 20% of the PET powder being 0.289 W·m⁻¹·K⁻¹ and 1078.46 J·K⁻¹·m⁻²·s^−1/2, and 0.289 W·m⁻¹·K⁻¹ and 1078.2 J·K⁻¹·m⁻²·s^−1/2 for LAT1 and LAT6, respectively. Based on the results obtained, we conclude that the formulation LAT-P10A20 is the most recommendable. Full article