Dissertação apresentada ao Programa de Pós-Graduação em Engenharia Civil da Universidade Federal da Integração Latino-Americana, como parte integrante dos requisitos para obtenção do título de Mestre em Engenharia Civil.

A crescente produção e presença de micro- e nanoplásticos (MNPs) no ambiente têm levantado preocupações quanto aos seus potenciais impactos na saúde humana. Estas partículas, resultantes da degradação de polímeros sintéticos, apresentam dimensões que variam de alguns nanómetros até 5 mm e possuem propriedades físico-químicas únicas que podem influenciar a sua interação com sistemas biológicos. O polietileno tereftalato (PET) é um dos plásticos mais amplamente utilizados em embalagens descartáveis, e a sua degradação origina compostos como o ácido tereftálico (TPA), o mono-2-(hidroxietil) tereftalato (MHET), o bis-2-(hidroxietil) tereftalato (BHET) e o etilenoglicol (EG), cujos efeitos toxicológicos permanecem pouco esclarecidos. A ingestão é considerada uma das principais vias de exposição humana a MNPs, permitindo que estas partículas alcancem o trato gastrointestinal e, subsequentemente, órgãos metabólicos como o fígado, um dos principais alvos de bioacumulação e toxicidade. Neste estudo, avaliou-se o impacto de MNPs de PET (600–700 nm e < 12 μm) e dos seus produtos de degradação na viabilidade, ciclo celular, internalização e produção de espécies reativas de oxigénio (ROS) em células de fígado (linha celular HepG2) cultivadas in vitro. As células foram expostas a diferentes concentrações de partículas e produtos de degradação (12,5–400 μg/mL) durante 24, 48 e 72 horas. A viabilidade celular foi determinada através do ensaio MTT; a dinâmica do ciclo celular e a internalização das partículas foram analisadas por citometria de fluxo; e os níveis de ROS foram quantificados utilizando um kit comercial. Os resultados mostraram que os MNPs de PET600 e PET12 diminuíram a viabilidade celular de forma dependente da concentração. Os produtos de degradação induziram toxicidade significativa a partir de 12,5 μg/mL. Entre eles, BHET e TPA revelaram maior toxicidade, seguidos por MHET (com efeitos cumulativos graduais) e pelo EG. BHET, MHET e TPA provocaram alterações nas diferentes fases do ciclo celular, com aumento de células em fase S e diminuição em G0/G1, enquanto o PET12 não provocou alterações significativas. Após exposição a PET12, a intensidade da dispersão lateral (SSC) aumentou com o aumento da concentração. Isto sugere uma interação crescente das partículas com as células, seja através de adsorção superficial ou internalização celular. Todos os produtos de degradação induziram a produção de ROS, indicando stress oxidativo associado à redução da viabilidade e alterações do ciclo celular. Os resultados demonstram que tanto os MNPs de PET quanto os seus produtos de degradação apresentam citotoxicidade em hepatócitos humanos, sendo esta mais acentuada nos produtos de degradação, o que reforça a necessidade de os incluir nas avaliações de risco à saúde humana.

The production of fossil-based plastics can be credited with the usage of around 4% to 8% of oil and gas globally, with current trends pointing to upwards of 20% in 2050, making this material a threat to the worsening of greenhouse emissions and global warming (Hopewell et al., 2009; Rhodes, 2018). Within this problematic, the pollution created by single-use bottles has received a lot of regulatory oversight, with an increasing number of methods for the reduction of said waste having been developed in response to said regulations. One of the most popularly used materials within this market is Polyethylene terephthalate (PET), with Recycled Polyethylene terephthalate (rPET) standing out as the most economically and environmentally sustainable alternative. With the introduction of regulations for the quantity of recycled content in PET bottles, several markets have been affected, though little regard has been given to the consequences of setting benchmarks that may be “overly prescriptive and market intrusive” (Ilie & Jurconi, 2019), with the market for rPET currently suffering from a supply-demand imbalance that has led to claims of economically unsustainable regulations. The goal of this research was to assess the degree to which the rPET level in the current legislation, and superior levels of rPET content, affects the financial viability of products that use said materials. This being done through a financial viability analysis of introducing increasing amounts of this material in an existing, established olive-oil product. It was found that for 30%, 50%, and 75% rPET content, financial viability could be reached for this specific unit in a static setting, this being concluded through an analysis of the willingness-to-pay (WTP) of consumers, measured by form of a questionnaire, and translated into the price sensitivity of demand of the three aforementioned product variants.

The demand for plastic has led to enormous plastic waste in the environment, which persist and negatively impact the ecosystems. Polyethylene terephthalate (PET) is one of the most common thermoplastic polymers available on the market. The concerns about plastic waste generated an interest in strategies to enhance its biodegradation and finding alternative polymers. In this work was investigated the possibility of using bacteria to degrade PET and to produce bioplastics (Polyhydroxyalkanoates, PHAs). Finally, the integration of the two processes was tested. Overall, the work aimed to investigate the potential to recycle PET into bioplastic using bacteria. The potential of bacterial consortia from various environmental samples to degrade PET granules in liquid matrix was investigated. The results revealed maximum PET granules degradation of 1.1 % by one of the tested consortia. PET degradation intermediate terephthalic acid (TPA) was not detected at the end of 55 days. Fourier-transform infrared spectroscopy (FTIR) results showed major spectral peak shifts and bends on PET chemical structure compared to non-inoculated control. The biodegradation of PET films buried in the soil (A), with mangrove plants (B), and bioaugmented with a bacterial consortium (C) was also investigated. The experiments were conducted for 270 days at ambient conditions. The results revealed no difference between treatments in the degradation, with a maximum weight loss of 0.118 % in the bioaugmented treatment. Nevertheless, Scanning Electron Microscope (SEM) and FTIR results indicated significant surface changes, spectral peak shifts, and stretches in PET chemical structures. Bacterial consortia isolated from the soil of the experimental treatments were assessed for degradation of PET monomers, TPA and monoethylene glycol (MEG), and intermediate Bis(2-hydroxyethyl) terephthalate (BHET). The consortia were inoculated in flasks V containing minimal media with 1000 mg/L TPA or BHET or1113 mg/L MEG as the sole carbon source. Results showed complete degradation of TPA and significant degradation of BHET (96.09%), and MEG (83.65%) by the consortia. In the second part of the study, bacteria were isolated from various environmental samples and screened for PHA production using Sudan Black B staining on colonies and smeared glass slides. Transmission Electron Microscope images were captured to confirm the intracellular PHA inclusions. A total of 35 isolates were screened for PHA, and 22 showed positive staining. The isolate showing higher levels of PHA synthesis (EC2-30-3) was identified based on 16S rRNA gene sequence as Bacillus sp. and selected for PET monomers degradation and fermentation cultures for PHA production. It was cultured in minimal (Moreira et al., 2013) media with 1000 mg/L TPA and 1113 mg/L MEG as the carbon source for eight days. The isolate grew better in media containing MEG, which was selected as a substrate model for PHA fermentation. To integrate PET monomers biodegradation and production of PHA, the isolate was cultured in 0.2 % MEG. A control with 0.2 % of glucose was prepared, and the cultures were incubated for 96 hours. Bacillus sp. EC2-30-3 showed higher PHA accumulation in media supplied with MEG (40.31%) than glucose (25.53%). This is the first report showing that Bacillus sp. uses PET monomer as carbon source to produce a biopolymer. FTIR results of the extracted PHA identified its functional units as C–H, CH3, C=O, and C–O groups. The absorption bands obtained are closely related to the structure of PHB. The study thus confirmed the ability of the isolated bacteria to degrade PET monomers and produce biopolymers. The results of this work open the possibility for upscaling the use of bacteria to mitigate the impact of PET on the environment while producing environmentally friendly bioplastics.

Annually, large amounts of waste Polyethylene Terephthalate (PET) bottles are discarded worldwide, although their properties can be useful in engineering works, such as soil improvement. Thus, the influence of PET fibers on sandy soil mechanical behavior was assessed in the present work. Consolidated-drained triaxial tests were performed using a 0.5% addition of 1.4 (SF-1) and 3.3 dtex fibers (SF-2). Afterward, plate load and slopes tests in the laboratory scale model were carried out for the most effective fiber. Overall, the inclusion of both fibers improved the stress-strain behavior, evident by greater absorbed strain energy in the reinforced soil. The insertion of 1.4 dtex PET fibers enhanced the internal friction angle of the soil from 31.9º to 44.3º, while a 29.7º value was obtained from 3.3 dtex fibers. Also, a cohesion intercept portion was identified in both composites, corresponding to 22.5 and 58.7 kPa for SF-1 and SF-2, respectively. The PET reinforcement reduced both vertical and horizontal deformation and altered the soil failure mechanism. The settlement reduction in fiber-reinforced sand is stress magnitude dependent, decreasing about 81% for stresses above 300 kPa, in which settlement of 125.3 mm from unreinforced sand was reduced to 23.6 mm by fiber insertion at 400 kPa. At the maximum comparable settlement, a 375.7% enhancement was seen in the bearing capacity, increasing from 240 kPa to 1141.6 kPa. In addition to a better understanding of soil-PET mixture, the results contribute to encouraging sustainable applications in engineering, such as embankment, shallow foundation, and retaining wall layers.

O objetivo deste trabalho foi avaliar as propriedades de painéis fabricados com partículas de madeira, poliestireno (PS) e polietileno tereftalato (PET). Foram utilizadas três proporções, em relação à massa seca de madeira, de poliestireno (0, 25 e 50%) e duas proporções de PET/PS (5/20 e 10/40%), combinadas com 50, 75 ou 100% de partículas de madeira de Pinus elliottii. Os painéis foram produzidos com adesivos à base de uréia-formaldeído ou de fenol-formaldeído, em três teores (0, 4 ou 6%) e três níveis de solução de poliestireno em tolueno (0 , 4 e 6%), todos calculados em relação à massa seca total dos painéis. Foram produzidos painéis de aproximadamente 400 x 400 x 10 mm, em camada única, com densidade aproximada de 0,6 g/cm3. Determinou-se a resistência dos painéis à tração perpendicular à superfície, à flexão estática (módulos de ruptura (MOR) e elasticidade (MOE)), ao arrancamento de parafusos, bem como a absorção de água e o inchamento em espessura, após 24 horas de imersão. Todas as propriedades mecânicas dos painéis foram superiores às exigidas pela norma ANSI/A 208.1-1993. Contudo, todos os painéis absorveram água em valores superiores àqueles normalmente observados em painéis comerciais. Apesar disto, o inchamento em espessura foi compatível com o dos painéis de partículas de madeira existentes no mercado. Os painéis nos quais se aplicou a solução de poliestireno foram, de modo geral, os que apresentaram os melhores valores para todas as propriedades.