https://ri.ufs.br/jspui/handle/riufs/2422 Sun, 06 Sep 2026 20:40:09 GMT 2026-09-06T20:40:09Z http://ri.ufs.br:80/retrieve/f3358433-77a8-4745-b3b7-b6ec0350c338/PPGQ.jpg https://ri.ufs.br/jspui/handle/riufs/2422 https://ri.ufs.br/jspui/handle/riufs/25794 Título: Estudo sistemático da transferência de energia e de espectros de absorção em complexos de európio(III): aplicações da TDDFT e análise quimiométrica Autor(es): Santos, Gabriel Silva Abstract: In this work, the performance of different TDDFT(Time-dependent density-functional theory) functionals in describing absorption spectra and energy transfer (ET) in Eu3+ complexes was evaluated. Initially, three β-diketonate complexes were studied: [Eu(DPTB)3(H2O)2] (Eu-1), [Eu(DPTB)3(BathPhen)] (Eu-2), and [Eu(hfaa)3(Nap-TerPyr)] (Eu-3), modeled using the DFT PBE0/TZVP/MWB52 method. TDDFT CAM-B3LYP results satisfactorily reproduced the experimental spectra of Eu-1 and Eu-2, with absorption dominated by β-diketonate ligands. ET occurred mainly through the T1→5D0 and T1→5D1 channels, with rates on the order of 107 s -1 . The higher sensitization efficiency of Eu-1 (η = 52.6%; exp.: 56.3%) compared to Eu-2 (η = 45.0%; exp.: 44.5%) was attributed to a lower T1→S0 deactivation rate. For Eu-3, Principal Component Analysis (PCA) grouped the functionals into three distinct clusters. The spectra predicted by PBE0, B1P, X3LYP, B1LYP, REVPBE0, TPSS0, PW1PW, mPW1PW, and mPW1LYP showed better agreement with experiment. The INDO/S-CIS method reproduced the spectrum well but significantly underestimated the T1 energy. TDDFT results indicated a relevant contribution of the neutral ligand to electronic absorption and of the β-diketonate ligands to ET via T1→Eu3+, with a calculated yield of 52.8% (exp.: 48.8%). Subsequently, the influence of methodological parameters on TDDFT spectra was investigated. PCA clustering of 122 experimental spectra revealed three distinct groups. The projection of theoretical spectra in PCA space, combined with Mahalanobis distances, indicated that the B3LYP functional is the most globally consistent among those studied. Therefore, it was adopted for the factorial design parameter study. The fractional factorial design (25-2 ) showed that the effects of basis set, number of excited states, use of TDA, implicit solvent, and dispersion depend on the spectral cluster: in group 1, effects were minimally relevant; in group 2, the absence of TDA improved agreement; and in group 3, dispersion corrections and absence of TDA were decisive for better reproduction of experimental profiles. Thu, 05 Feb 2026 00:00:00 GMT https://ri.ufs.br/jspui/handle/riufs/25794 2026-02-05T00:00:00Z https://ri.ufs.br/jspui/handle/riufs/25394 Título: Remoção de poluentes emergentes por adsorventes desenvolvidos a partir de resíduo sólido de estação de tratamento de água Autor(es): Fernandes, Erica Porto Abstract: The increasing presence of pharmaceutical compounds in aquatic environments has caused significant environmental impacts. Conventional treatment methods face challenges at the industrial scale, while abundant and low-cost adsorbents, such as industrial process residues, offer a sustainable alternative for the removal of pharmaceuticals. In this study, adsorbent materials were developed from sludge generated by the water treatment system of a thermoelectric power plant. Adsorption studies were carried out using unmodified sludge (RPL), chemically modified sludge with dodecyl trimethylammonium chloride (RMQ), and thermally modified sludge (RMT). The materials were applied for the removal of ibuprofen, diclofenac, hydroxychloroquine, and losartan in aqueous medium. Different characterization techniques were performed for the adsorbents. X-ray fluorescence (XRF) revealed the presence of Si, Al, and Fe as the predominant elements. Fourier transform infrared spectroscopy (FTIR) showed vibrational bands associated with Si-O-Si, Si-O-Al, Si-O, Si-OH, and CH₂ groups, while X-ray diffraction (XRD) indicated similar patterns among the materials, with crystalline phases such as SiO₂ and NaAlSi₃O₈. The chemical modification of the residue promoted a moderate increase in surface area and led to an improvement in the removal efficiency of the pharmaceuticals, with values higher than 70.00%.The adsorption capacities obtained in batch adsorption studies were 101.43 mg g-1 for losartan, 73.77 mg g-1 for diclofenac, 24.81 mg g-1 for ibuprofen, and 39.25 mg g-1 for hydroxychloroquine. In fixedbed column adsorption studies, the adsorption capacities were 46.71, 51.70, 44.86, and 20.43 mg g-1 for hydroxychloroquine, losartan, diclofenac, and ibuprofen, respectively. Chemical regeneration of the adsorbents allowed their reuse for most pharmaceuticals, although a reduction in adsorption capacity was observed after successive cycles. The electrochemical degradation of the pharmaceuticals was evidenced by the reduction of the characteristic anodic peaks in the voltammograms, indicating a decrease in the concentration of electroactive species in solution. Ecotoxicity tests using pharmaceutical solutions resulted in EC50,48 h values of 3.81, 24.11, 175.50, and 53.92 mg L-1 for hydroxychloroquine, diclofenac, losartan, and ibuprofen, respectively. The results obtained in this study demonstrated the feasibility of using this residue due to its efficiency in removing pharmaceuticals and its potential applicability at an industrial scale. Furthermore, the reuse of this residue may contribute to reducing its environmental impacts. Fri, 27 Mar 2026 00:00:00 GMT https://ri.ufs.br/jspui/handle/riufs/25394 2026-03-27T00:00:00Z https://ri.ufs.br/jspui/handle/riufs/24753 Título: Materiais adsorventes obtidos da biomassa de Ingá-cipó (Inga edulis): remoção de metais pesados e avaliação ecotoxicológica Autor(es): Lima, Lucas dos Santos Abstract: Water contamination by toxic metals, especially hexavalent chromium Cr(VI) and divalent lead Pb(II), represents a significant environmental challenge due to their persistence and harmful effects on aquatic organisms. In this study, two adsorbent materials derived from the biomass of Inga edulis bark were developed and evaluated: raw biomass (BMIG) and sulfuric acid–activated biomass (BMIGA). The materials were characterized using physicochemical techniques, which confirmed structural modifications and the presence of functional groups capable of interacting with the studied metals. Batch adsorption experiments enabled the identification of favorable operational conditions and showed that BMIGA exhibited maximum adsorption capacities of 356.6 and 222.1 mg g-1 for Cr(VI) and Pb(II) ions, respectively, compared to BMIG, which presented an adsorption capacity of 46.0 mg g-1 for Cr(VI) and showed no removal of Pb(II) ions. Chemical activation resulted in an increase in surface area and the introduction of oxygenated functional groups, which enhanced the adsorption of both metal ions. Kinetic models indicated that Cr(VI) adsorption by BMIG and BMIGA followed the Elovich model, characterizing a chemisorption process on a heterogeneous surface. For BMIGA and Pb(II), the best fit was obtained with the pseudo-second-order model, suggesting interaction with oxygenated functional groups. In isotherm studies, Cr(VI) adsorption fitted both the Langmuir and Freundlich models, whereas Pb(II) showed a better fit to the Freundlich model. Thermodynamic analyses demonstrated that Cr(VI) adsorption by BMIG was non-spontaneous, while BMIGA promoted spontaneous adsorption for both metals. Under continuous-flow conditions, fixed-bed columns exhibited stable performance, with breakthrough times of 200.0 min and 281.7 min for Cr(VI) adsorption and 554.8 min for Pb(II) adsorption at low concentrations, which were compatible with practical applications and showed good agreement with the Thomas, Yoon–Nelson, and Clark models. The ecotoxicological assessment performed with Daphnia similis confirmed the high toxicity of solutions containing Cr(VI) and Pb(II) ions prior to treatment. After adsorption, no acute effects were observed on the organisms, demonstrating that the materials were able to significantly reduce toxicity. Finally, the saturated adsorbents were applied in electrochemical tests for green hydrogen and oxygen production, revealing potential for reuse and value addition after environmental application. Overall, the results demonstrate that Inga edulis bark is a promising biomass for the production of sustainable and efficient adsorbents with multifunctional potential, contributing to pollution mitigation strategies and technologies associated with the circular economy. Tue, 27 Jan 2026 00:00:00 GMT https://ri.ufs.br/jspui/handle/riufs/24753 2026-01-27T00:00:00Z https://ri.ufs.br/jspui/handle/riufs/24224 Título: Eletrocatalisador bifuncional baseado em material carbonáceo para geração de hidrogênio e oxigênio de baixo carbono Autor(es): Santos, Marcos Vinícius Quirino dos Abstract: The high cost, scarcity, and limited durability of noble-metal-based electrocatalysts, such as platinum, iridium, and rhodium, have driven the search for alternative materials that are abundant, sustainable, and economically viable for use as catalysts in water electrolysis. In this context, biochar derived from plant residues has emerged as a promising carbon-based material for the development of efficient and environmentally friendly electrocatalysts. This dissertation reports the development of an electrocatalyst based on biochar derived from the aquatic plant Marsilea minuta (BMQ), applied to the hydrogen evolution reaction (HER) in acidic medium and to the oxygen evolution reaction (OER) in alkaline medium. The biochar was prepared by pyrolysis at 500 °C under an inert nitrogen atmosphere and characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results revealed an amorphous structure with a porous surface and the presence of oxygen- and nitrogen-containing functional groups, which act as active sites for electrocatalytic reactions. Electrochemical tests using a glassy carbon electrode modified with the material demonstrated significant activity for both HER and OER, exhibiting low overpotentials required to reach a current density of 10 mA cm⁻² and Tafel slopes consistent with favorable reaction kinetics. Electrochemical stability was confirmed by chronopotentiometry, highlighting the potential of BMQ as a bifunctional electrocatalyst with low carbon emissions. These results indicate that biochar derived from Marsilea minuta is a promising and sustainable alternative for application in water electrolysis systems, contributing to the advancement of low carbon hydrogen and oxygen production technologies. Thu, 14 Aug 2025 00:00:00 GMT https://ri.ufs.br/jspui/handle/riufs/24224 2025-08-14T00:00:00Z