Utilização do hidrocarvão ativado da casca do tamarindo (tamarindus indica l.) para remoção de metformina de soluções aquosas

• Ano de defesa: 2025
• Autor(a) principal: Mattos, Eyme Gabriele de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Tecnológica Federal do Paraná; Apucarana; Brasil; Programa de Pós-Graduação em Engenharia Química; UTFPR
• Palavras-chave em Português: Carbonização; Resíduos orgânicos; Adsorção; Carbonization; Organic wastes; Adsorption; CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA; Engenharia Química
• Link de acesso: http://repositorio.utfpr.edu.br/jspui/handle/1/38485

The presence of pharmaceuticals such as metformin in water bodies has become a growing concern due to environmental impacts and health risks, as these compounds are not fully removed by conventional treatment processes. Metformin, widely used in the treatment of diabetes, is frequently found in significant concentrations in wastewater. In this context, adsorbents produced from agro-industrial residues have emerged as a promising alternative for the removal of such contaminants. This study evaluated the preparation and characterization of adsorbent materials obtained from tamarind shell subjected to different treatments: raw shell; activated shell, chemically activated with potassium hydroxide (KOH); hydrochar, obtained by hydrothermal carbonization at 180 °C for 10 hours; and activated hydrochar, which underwent hydrothermal carbonization followed by chemical activation with KOH. All materials, as well as commercial activated carbon, were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), specific surface area analysis by N₂ physisorption (BET), point of zero charge (pHPZC), quantification of acidic and basic surface groups, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA).The characterizations revealed relevant structural and chemical modifications, especially in the activated hydrochar, which showed changes in surface structure, such as modifications in functional groups and an increase in carbon content, reaching a level similar to that of commercial activated carbon. However, a decrease in specific surface area was observed, possibly due to pore collapse or blockage during chemical activation. Batch adsorption tests indicated that the activated hydrochar was the most efficient adsorbent, achieving 51% metformin removal in the preliminary test, surpassing commercial activated carbon (44%). Subsequent studies optimized the operational conditions, with the best performance observed at pH 9.0 and with 50.00 mg of adsorbent, resulting in 69% removal. The adsorption kinetics for activated hydrochar were best described by the pseudo-second-order model, with an equilibrium time of approximately 450 minutes. For commercial activated carbon, the best fit was to the pseudo-first-order model, with a similar adsorption capacity to that of activated hydrochar. The adsorption isotherms showed better fitting to the Sips model for both adsorbents, with maximum adsorption capacities close to 143.27 mg g⁻¹ for activated hydrochar and 148.97 mg g⁻¹ for commercial activated carbon, both at 55 °C. Thermodynamic analysis revealed that adsorption by activated hydrochar is endothermic (∆H° = +63.43 kJ mol⁻¹) and favored by increasing temperature, while adsorption by commercial activated carbon was exothermic (∆H° = −13.07 kJ mol⁻¹), indicating distinct adsorption mechanisms.Desorption tests showed high efficiency in the first cycle, with 94.97% metformin desorption, but a progressive reduction in efficiency in subsequent cycles, associated with the loss of surface functional groups. The results reinforced the potential of tamarind shell-derived activated hydrochar for the removal of the studied pharmaceutical.