Funcionalização de pavimentos asfálticos para redução de emissões de NO2: um estudo de viabilidade

Abstract

Measuring and reducing levels of air pollutants to improve air quality, particularly in large urban centers, is a relevant topic and constitutes an important environmental challenge with significant influence on human health. The general objective of this research was to evaluate emissions during the machining of asphalt mixtures, as well as to investigate whether asphalt pavements functionalized with Titanium Dioxide (TiO2), and TiO2 doped with Chitosan (CSTiO2), could mitigate nitrogen dioxide (NO2) and volatile organic compounds (TVOC). This thesis was written in article format, where chapter 1 presented the general context of the study's scope, and chapters 2 through 4 are articles related to the specific objectives. Chapter 2 aimed to diagnose Volatile Organic Compounds (VOCs), including Polycyclic Aromatic Hydrocarbons (PAHs), Nickel (Ni), and Vanadium (V), through chemical speciation of these substances in particulate matter filters sampled at an asphalt mixing plant during its inactivity and production periods. The quantification of these pollutants was performed by extracting the organic compounds present in the filters using dichloromethane and analyzing the extracts via Gas Chromatography with Mass Spectrometry (GC/MS) and High-Resolution Atomic Absorption Spectroscopy (HR-CS AAS). The results showed the contribution of the asphalt mixture machining process to the worsening of air quality at the plant, evidenced by pollutant contrasts during its inactivity and operation periods. Chapter 3 aimed to evaluate passive sampling (PS) as a tool for diagnosing NO2 in the asphalt paving sector and for monitoring the photocatalytic reduction of this pollutant in functionalized asphalt pavements. For this purpose, the behavior of PS was evaluated in different locations, and it was calibrated with data from a reference station. This method was considered valid, robust, and useful for NO2 monitoring in asphalt paving services. Finally, Chapter 4 evaluated asphalt mixtures functionalized with TiO2 and CS-TiO2 for reducing NO2 and TVOCs. The CS-TiO2 composite was synthesized via wet impregnation and characterized, along with TiO2, using techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, Particle Size (DLS), and Zeta Potential. Aqueous solutions of 2.5 g/m² and 5.0 g/m² of each of these photocatalysts were applied to the pavement surface. The performance of these materials in reducing NO2 concentrations was tested in the laboratory using an alternative photocatalytic reactor. The results showed a reduction of about 25% and 30% of the initial NO2 concentration with TiO2 and CS-TiO2, respectively, with CS-TiO2 being effective in the visible light region (15%). Regarding TVOCs, emissions from the asphalt binder were observed, and their reduction by about 40% to 80% was attributed to the pavement functionalization process. Despite the promising results, it was concluded that additional tests are necessary to better evaluate the performance of these compounds and the influence of other variables in the photocatalytic pollutant reduction process.