SONIA REGINA HOMEM DE MELLO CASTANHO

SONIA REGINA HOMEM DE MELLO CASTANHO

(Fonte: Lattes)

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Graduada em Engenharia de Materiais (UFSCar, Universidade Federal de São Carlos), Mestre em Tecnologia Nuclear (IPEN/USP, Universidade de São Paulo) e Doutora em Ciências Químicas-Cerâmicos (UAM/ES -ICV/CSIC, Universidad Autónoma de Madrid, Espanha e Instituto de Ceramica y Vidrio/CSIC de Espanha). Ela é Pesquisadora Senior e atualmente Gestora Adjunta em Pesquisa e Desenvolvimento do Centro de Ciências e Tecnologia de Materiais (CCTM) do Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN-SP). É Professora da Universidade de São Paulo (USP), no programa de posgraduação Tecnologia Nuclear - Materiais. Coordenadora do grupo de pesquisas (GP/CNPq) em Materiais e Meio Ambiente. Principais áreas de atuação: - Energias Renováveis (células a combustível, catalizadores e biomassa), - Ambiental (mitigação, inertização e requalificação de efluentes e subprodutos de processos extrativistas e industriais, diretivas ambientais (RhOS, WEEE)), - Cerâmicas Biocompatíveis (vidros, compósitos multifuncionais para a implantologia). Experiência em gestão de Centro de Pesquisas, gestão ambiental, gestão de projetos, planejamento composicional de materiais, processamento coloidal, reologia, vidros e vitroceramicos, compósitos multifuncionais e nanoestruturas naturais. (Texto extraído do Currículo Lattes em 27 dez. 2021)

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Thermal evaluation of a Cs-loaded waste vitrification
2024 - COSTA-SILVA, D.L.; ARAUJO, M.S.; FUNGARO, D.A.; MELLO-CASTANHO, S.
Nuclear power generation has been increasing worldwide over the years, helping to avoid the emission of billions of tons of carbon dioxide (CO2) compared to coal power generation, making it a reliable method for providing green energy. However, as a byproduct of nuclear reactors, as well as fuel processing plants, hospitals, and research institutes, radioactive waste is generated. These wastes pose a significant risk to human health and the environment due to the penetration of radioactivity into tissues, which damages DNA. Therefore, they need to be managed appropriately before long-term disposal in geological repositories. Among the many radionuclides found in high-activity waste, 137Cs is of particular concern due to its high mobility in water systems, requiring special methods for its capture and immobilization in stable matrices. In this study, the immobilization of 137Cs radionuclides in a borosilicate glass doped with niobium (Nb) was thermally evaluated through a vitrification process, using a synthetic type A zeolite saturated with 133Cs (stable) as a simulated radioactive waste. The incorporation of 40.0 wt.% of this material into the glass composition resulted in a vitrified waste with good melting homogeneity and thermal stability. Several changes due to the incorporation were detected in thermal analysis (DTA), with events such as glass transition, initial crystallization, complete crystallization, and subsequent melting all shifting to higher temperatures. The compositional changes induced by vitrification moved the system to new locations in the ternary equilibrium phase diagrams of the subsystems, in different compatibility triangles, and closer to higher liquidus temperatures than those observed for the raw glass matrix. Through crystallization induced by heat treatment, crystalline phases were obtained, as indicated in the phase diagrams. Cs atoms previously immobilized in the glass network structure became components of pollucite crystals (CsAlSi₂O₆) during heating up to 800 ºC. These results are promising for using this glass composition to immobilize waste containing 137Cs, as Cs atoms showed excellent interaction with this system in both the glass and crystalline phases.
Byproduct-based zeolite type A as absorbent material for decontamination of simulated radioactive wastewater
2024 - ARAUJO, M.S.; COSTA-SILVA, D.L.; MELLO CASTANHO, S.R.; FUNGARO, D.A.
The secure disposal of radioactive wastewater, a waste from nuclear operations, presents a significant challenge due to the presence of hazardous radionuclides like cesium. The efficient removal of cesium, a major fission product with a long half-life and potent radiation, is crucial for environmental and human health protection. Zeolites, with their high ion exchange capacity and porous structure, offer a promising solution for cesium removal from wastewater. The potential to synthesize zeolites from abundant and cost-effective agro-industrial residues further enhances their appeal for sustainable wastewater treatment. The present study investigates the adsorption of cesium from simulated radioactive wastewater using zeolite type A synthesized from sugarcane bagasse ash, a readily available Brazilian byproduct. The synthesized zeolite was characterized by X-ray fluorescence spectroscopy, X-ray diffraction, and thermal analysis techniques. The results confirmed the successful synthesis of high-purity zeolite A with excellent adsorption capacity for cesium. The structural integrity and thermal stability of the zeolite were maintained even after cesium adsorption, making it suitable for immobilization processes. The findings highlight the potential of zeolite synthesized from sugarcane bagasse ash as an effective and sustainable material for the treatment and removal of cesium from radioactive wastewater, contributing to environmental remediation efforts in the nuclear industry.
New approach to niobia-modified borosilicate glasses for Cs waste immobilization
2024 - COSTA-SILVA, D.L.; ARAUJO, M.S.; FUNGARO, D.A.; SILVA, P.S.C.; MELLO-CASTANHO, S.
The use of nuclear materials is increasing in energy production, medicine, and environmental sectors. Following this trend, the generation of radioactive wastes is also increasing in the whole production cycle and use of this kind of materials. Among these, the 137Cs radionuclide presents a potential risk to human health due to its half-life time (30,2 years), high-level activity (1 TBq) and easiness to contaminate rivers, soil, and air. The immobilization of 137Cs in solid matrices has been an available option researched by several countries. In this context a new glass composition based on aluminoborosilicate glass modified with niobium (Nb) was used for the immobilization of cesium through adding Cs-loaded zeolite. Homogeneous vitreous wasteforms were improved with the growth of Nb content in the compositions. All compositions were able to keep up to 5.9 wt% Cs2O, previously adsorbed by zeolite A, and the immobilization efficiency was around 53%. Their structural analyses by Raman revealed a depolymerized and complex network structure, due to the presence of several cations including Cs. In turn, Nb reflected positively on the chemical resistance and thermal properties, by changing the distribution of silicate species. The wasteforms presented good glass forming ability and thermal stability up to 520 °C. Through the thermal treatment for devitrification, Cs atoms were stabilized into the Pollucite phase (CsAlSi2O6). Besides that, the wasteforms, preferably the one containing 8.0 mol% Nb, showed low elemental releases and leaching rates for Cs (1 × 10−3 g m2.day−1), after the leaching experiments at 90 °C for 7 days in static conditions, verified by the neutron activation analysis (NAA).
Byproduct-based zeolite type A as absorbent material for decontamination of simulated radioactive wastewater
2024 - ARAUJO, M.S.; COSTA-SILVA, D.L.; MELLO CASTANHO, S.R.; FUNGARO, D.A.