https://repositorio.ufpb.br/jspui/handle/tede/7029 PPGQ Sun, 30 Aug 2026 09:26:12 GMT 2026-08-30T09:26:12Z https://repositorio.ufpb.br/jspui/handle/123456789/38815 Título: Produção de biocarvão a partir de ligninas residuais de biomassas pelo processo de pirólise Autor(es): Almeida, Thiago Claudino Mendes de Orientador: Santos, Nataly Albuquerque dos Abstract: Lignin is the most structurally complex component present in lignocellulosic biomass. Each year, thousands of tons of lignin-rich residues from enzymatic hydrolysis may be generated in a sugarcane cellulosic ethanol bioreûnery. The present study uses lignin extracted from sugarcane bagasse as a feedstock for biochar production, as an alternative to the direct use of raw bagasse. In addition, lignin is also present in the mesocarp of coconut, a residue that is often improperly disposed of. Therefore, the production of biochar from this lignin via pyrolysis, as well as the potential applications of the resulting material, were investigated. The lignin samples derived from sugarcane bagasse and coconut ûbers, as well as their corresponding biochars, were characterized and systematically compared with commercial kraft lignin and its biochar through elemental analysis, higher heating value determination, spectroscopic techniques, thermal analyses, X-ray diûraction, and scanning electron microscopy coupled with energy-dispersive spectroscopy. The results indicated higher efficiency in the lignin extraction process from sugarcane bagasse and further confirmed the amorphous nature of both the extracted lignin and the derived biochar. An O/C ratio of approximately 0,3 was obtained for the sugarcane bagasse lignin biochar based on both elemental and Raman spectroscopy analyses. Both elemental composition assessment and Raman spectroscopic analysis indicated that all biochar specimens exhibited hydrogen-to-carbon (H/C) ratios exceeding 0,5, however, the O/C and H/C ratios in the sugarcane bagasse lignin biochar indicated the occurrence of partially oxidized carbon, with a significant portion of fixed carbon, in a biochar with moderate stability and low levels of contamination. Analyses of the effect of an intermediate pyrolysis temperature on a recalcitrant material such as lignin indicated that the biochar derived from sugarcane lignin exhibited higher energy density, in the value of 25,95 MJ/kg, and a high carbon content, in the value of 61,64%. The proposed approach, therefore, provides promising alternatives for the valorization of lignin waste and the generation of biochar for both energy applications and as a multifunctional material, combining high energy density with structural stability, which significantly expands its industrial application potential. Editor: Universidade Federal da Paraíba Tipo: Tese Thu, 11 Dec 2025 00:00:00 GMT https://repositorio.ufpb.br/jspui/handle/123456789/38815 2025-12-11T00:00:00Z https://repositorio.ufpb.br/jspui/handle/123456789/38765 Título: Síntese de mono e diésteres, cetoésteres e 2-selenoacetanilidas derivados de ftalimida: atividade antimicrobiana, sinergismo, mecanismo de ação e ecotoxicidade Autor(es): Alves, Francinara da Silva Orientador: Athayde Filho, Petrônio Filgueiras de Abstract: Phthalimide stands out as a promising block in the synthesis of new drug candidates. Its results show several pharmacological activities, including antimicrobial, antitumor, antiinflammatory, among others. Thus, this study describes the description of four families of compounds, including potassium phthalimide (3a-e) and potassium phthaloylglycinate (4a-e), which were produced from 4-chlorobutyl benzoate precursors. Potassium phthaloylglycinate derivatives with 4-substituted 2-bromoacetophenones (6f-j) and phthaloylglycine derivatives with 2-selenoacetanilide (9k-n), in addition to phthaloylglycine monoesters (11o-u) and tetrachlorophthaloylglycine (12o-u) were also used to evaluate the impact of electrode and electrowithdrawing groups, as well as hydrocarbon spacers, on the antimicrobial properties. In total, thirty-three final compounds were synthesized, eighteen of which were new, using simplified synthetic routes and a reduced number of steps. The compounds were subjected to in vitro antimicrobial evaluation, where compounds 3a-c and 4a-d showed activity against the three bacterial strains and the four yeast strains with values ranging from 128 to 1024 μg mL-1. Compound 3b (monoester with 4-methyl substitute) derived from potassium phthalimide, showed protection against all strains of bacteria and yeasts tested, with MIC = 128 μg mL-1, lower than the standard drug for fungi (fluconazole). Thus, compound 3b was investigated in order to know its mechanism of action, where it associated with ergosterol led to an increase in MIC from 128 to 1024 μg mL-1. Compound 3b was also tested in association with chloramphenicol for the strain of Peseudomonas aeruginosa with the ICIF value = 0.5 μg mL-1 decreasing the synergism. Compound 9k (2-selenoacetanilide with phthaloylglycine) showed very significant activity against strains of Candida gattii and Aspergillus niger with MIC = 2.5 and 10 μg mL-1, respectively, and MIC of 80 and 40 μg mL-1 for Klebsiella pneumoniae and Salmonella typhimurium, respectively. Compounds 11r, 12p, 12s and 12t showed activity against strains of bacteria and fungi with MIC value = 512 and 1024 μg mL-1, where, with the increase of the carbonic extension, the impact increased. The selenide compound was obtained with sufficient crystallization quality to be diffracted and a crystallographic study was carried out, where it presented a monoclinic system. An in silico study was conducted with the most promising compounds, all of which met the Lipinski criteria, indicating good oral bioavailability in a possible application, in addition to showing low toxicity. Thus, the most promising compounds (3b, 3c, 4a and 4c) were evaluated for toxicity on Artemia salina, being classified as moderately toxic and non-toxic. Editor: Universidade Federal da Paraíba Tipo: Tese Thu, 06 Feb 2025 00:00:00 GMT https://repositorio.ufpb.br/jspui/handle/123456789/38765 2025-02-06T00:00:00Z https://repositorio.ufpb.br/jspui/handle/123456789/38636 Título: Síntese fitoassistida de óxidos metálicos para aplicação na reação de evolução de oxigênio (OER) Autor(es): Silva, Giovani Luiz da Orientador: Silva, Fausthon Fred da Abstract: Global ecological demands reinforce the need for the use of clean and renewable energy sources, such as hydrogen (H2), which is a promising energy source that can be obtained through water electrolysis. Although this process is environmentally friendly, it requires high energy input, and electrocatalysts are needed to make it viable. Therefore, efforts have been made to develop high-performance electrocatalysts based on earth-abundant transition metals. Greener synthesis routes, such as using plant extracts that stabilize nanoparticles, are also on the rise as they help reduce environmental impacts. Thus, this study reports a green synthetic route using aqueous (H) and ethanolic (E) extracts of the wild parsley plant (Ipomoea asarifolia) as a stabilizing agent to obtain nickel oxide (NiO) nanoparticles at different calcination temperatures (300 °C, 500 °C, and 700 °C). The plant’s phytochemistry was investigated by HPLC, and the materials were characterized by X-ray diffraction (XRD), vibrational spectroscopy in the infrared region (FTIR), Raman spectroscopy, solid-state UV-VIS spectroscopy, and scanning electron microscopy with energy- dispersive X-ray spectroscopy (SEM-EDS). The techniques confirmed the cubic structure of NiO and Co3O4, with residual organic groups on the material surfaces. Raman spectroscopy signals also confirmed the presence of structural defects, which positively contribute to the electrocatalytic process. The synthesis using aqueous extracts led to the formation of materials with diverse morphology, while ethanolic extracts resulted in more uniform particles. Electrocatalytic performances in alkaline solution (KOH, 1.0 mol L-1) were investigated. The experimental overpotentials at J = 10 mA cm-2 and Tafel slope values were promising, starting from 307 mV and 60.35 mV dec-1 for NiO samples, and 290 mV and 47.11 mV dec-1 for Co3O4 samples. Therefore, this green synthesis route proves to be economically viable, producing high- performance electrocatalysts compared to similar results in the literature. Editor: Universidade Federal da Paraíba Tipo: Dissertação Fri, 25 Apr 2025 00:00:00 GMT https://repositorio.ufpb.br/jspui/handle/123456789/38636 2025-04-25T00:00:00Z https://repositorio.ufpb.br/jspui/handle/123456789/38477 Título: Metodologias eletroquímicas e espectroeletroquímicas de ordem superior para análise de matrizes complexas Autor(es): Barreto, Matheus de Caldas Orientador: Fragoso, Wallace Duarte Abstract: The effect of interferences is an important problem in Analytical Chemistry. Some approaches to deal with this problem are usually separation methods, deve-lopment of selective sensors, among others. There are also ways to mathematically separate the analyte signal, with it being acquired in multiple instrumental ways, extracting relevant information and gaining robustness to the interferences through mathematical properties. These are called multiway or higher-order methods. In this work, three methods based in electrochemical and spectroelectrochemical te-chniques were used to obtain multiway signals, applying them in the study of different systems. The first is a spectroelectrochemical method, combining chro-noamperometry and fluorescence. A proprietary cell and an interfacing system were developed for the experiment, with dopamine/epinephrine mixtures being used to test the methodology. Data was acquired in three ways (emission-time-potential) and the third-order models provided predictions with relative errors of prediction (REPs) of 1 to 2%, compared to the second-order models, presenting REPs of 9 to 40%, highlighting the advantages of expanding data dimensionality beyond second-order. The second method was the expansion of electrochemical impedance spectroscopy to a second order technique by varying the direct current potential. This method was applied to the quantification of paracetamol in urine, in the presence of added uric and ascorbic acid as interferents. Using the combi-nation of the real part of the impedance with the phase shift of the signal, it was possible to determine paracetamol in the range of 0.5 to 3.0 pmol.L¹ with a root mean squared error of prediction (RMSEP) of 0.38 pmol.L. Finally, the third method consisted of the application of multiway voltammetric techniques, creating models for the identification of synthetic cannabinoids in street samples (n = 48) The best performance was attained by models created with differential pulse vol-tammetry with gradual changes in pulse times, allowing the identification of drugs based on 8-quinoline indole-3-oate, indazole-3-amide and negative samples, with a 98.3% accuracy. Editor: Universidade Federal da Paraíba Tipo: Tese Thu, 30 Oct 2025 00:00:00 GMT https://repositorio.ufpb.br/jspui/handle/123456789/38477 2025-10-30T00:00:00Z