Extração e adsorção de HPAs através de transferência gás- sólido (XAD-2 e EPU) utilizando dispositivo de extração e coleta

Abstract

Polycyclic Aromatic Hydrocarbons (PAHs) are organic compounds formed by two or more condensed aromatic rings. These compounds are important organic pollutants and due to their harmful action their concentrations in the environment are permanently controlled. Additionally, the PAHs can be found in the vapor phase environment, attached to surfaces of small solid particles and depending on the atmospheric temperature, are divided between the vapor phase and the particulate. The American Environmental Protection Agency (US EPA) listed 16 PAHs based on their toxicological profiles as priority pollutants. Therefore, in the present study, it was selected a group of 5 PAHs, which are included in this list, using as selection criterion the number of aromatic rings (PAHs with 2, 3 and 4 rings). These compounds are acenaphthylene, fluorene, phenanthrene, pyrene and benzo(k)fluoranthene. Then, it was studied the extraction capacity of the PAH solution in water under action of argon flow at different temperatures, being these 13, 50, 80 and 95ºC. The extraction of the mixture of these compounds at the same temperatures, with the exception of the temperature of 13ºC, was also studied. The gas-solid adsorption study of 3 of the selected compounds was carried out, being acenaphthylene, fluorene and phenanthrene, under the action of argon flux and temperature of 50ºC, where the adsorbents investigated were Amberlite XAD-2 and polyurethane foam (PUF). For the accomplishment of this work we used an Extraction and Collection Device (DEC), which was developed to generate and collect PAHs vapors. Molecular absorption spectrometry ultraviolet-visible region and High Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD) were used to assess the extraction yields as well as the adsorption capacities of the solid adsorbens. At none of the working temperatures was the extraction of benzo(k)fluoranthene, although all other PAHs were extracted at temperatures of 80 and 95°C. At the temperature of 50ºC, with the exception of pyrene, all the compounds were extracted and at 13ºC only acenaphthylene and fluorene. The extractions showed different results when comparing the PAHs individually and in mixtures. While the adsorbents used, Amberlite XAD-2 and PUF, presented themselves similarly efficient with respect to adsorption. In addition, different masses of these adsorbents were required for each PAH studied, due to differences in extraction yields. The PAHs with higher vapor pressure, for example, required a higher mass of adsorbent to achieve an adsorption efficiency of the order of 100%. Thus, it is concluded that PAHs can be entrained, even though they are below their boiling point, and that the adsorbents tested are efficient for the removal of these compounds from the environment.