The influence of heteroatoms on the adsorption of fluorene and analogues onto high-density polyethylene and polyurethane microplastics
Visualizar/ Abrir
Data
2023-08-30Primeiro coorientador
Villetti, Marcos Antônio
Segundo coorientador
Menezes, Bryan Brummelhaus de
Primeiro membro da banca
Rhoden, Cristiano Rodrigo Bohn
Segundo membro da banca
Souza Junior, Fernando Gomes de
Terceiro membro da banca
Pavan, Flávio André
Quarto membro da banca
Kunz, Simone Noremberg
Metadata
Mostrar registro completoResumo
Polycyclic Aromatic Hydrocarbons (PAHs) are hydrophobic organic pollutants, classified as
mutagenic and carcinogenic, found in complex mixtures in nature in their basic form and their
nitrogenous, oxygenated, and sulfur derivatives. The physical and chemical properties of PAHs
allow interaction by adsorption with small fractions of plastic contaminants, called
microplastics (MP), due to the coexistence of these two pollutants, their distribution becomes
wider. In this thesis, the adsorption of fluorene (FLN), dibenzothiophene (DBT), dibenzofuran
(DBF), and carbazole (CBZ) on high-density polyethylene (HDPE) and polyurethane (PU) MP
was investigated to elucidate the influence of heteroatom on the interaction with nonpolar
(HDPE) and polar (PU) MP. On HDPE, the adsorption of FLN, DBT, and DBF indicates the
formation of a monolayer, characterized by the Langmuir isotherm, and the adsorption
mechanism has hydrophobic interactions as predominant forces, indicated by the highest
adsorption capacity (𝑞௫) in the order of DBT>FLN≈DBF, according to Log Kow values. On
the other hand, CBZ did not show significant interaction with HDPE, as it has lower Log Kow.
The thermodynamic parameters indicate a spontaneous (∆G<0) and exothermic (∆H<0) process
with positive entropy and favoring of adsorption with decreasing temperature. The adsorption
of FLN and derivatives on PU fitted the BET isotherm model, indicating the formation of
adsorption multilayers. The BET isotherm allows us to determine the 𝑞௫ of the monolayer,
and in this case, the order was DBT>DBF≈FLN≈CBZ at 10, 15, 25, and 35°C with the
coexistence of a heterogeneous interaction mechanism with hydrophobic interaction, π─π,
hydrogen bonding, and van der Walls forces. At lower temperatures, adsorption was favored,
with exothermic (∆H<0), non-spontaneous (∆G>0) process and decrease in entropy, except for
the DBF adsorption monolayer characterized as an endothermic process (∆H>0) and positive
entropy. In PU the adsorption in artificial seawater was tested and showed no significant
difference to pure water, however, there was an increase in multilayer adsorption due to the
salting-out effect. The competitive adsorption in aqueous solutions of FLN, DBT, DBF, and
CBZ on PU showed similar results to the individual process, with lower adsorption of CBZ at
higher concentrations. The adsorption kinetics of FLN and derivatives on HDPE and PU fitted
the pseudo-second-order model. The heteroatoms in the DBT, DBF, and CBZ molecules
showed a direct influence on the adsorption mechanism in HDPE and PU MP. In HDPE the
higher hydrophobicity of DBT conferred by the sulfur atom played a fundamental role in
increasing adsorption, while the nitrogen atom in CBZ played the opposite role. In PU the
presence of heteroatoms and polar functional groups on the surface of the MP, favored
adsorption by multiple mechanisms. Thus, it was possible to determine the behavior in the
interaction of organic pollutants with MP, which contribute to understanding the role of MP as
carriers of these contaminants in the distribution in the environment or the entry into the food
chain.
Coleções
Os arquivos de licença a seguir estão associados a este item: