LEANDRO GOULART DE ARAUJO

LEANDRO GOULART DE ARAUJO

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TiO2 P25 and Kronos vlp 7000 materials activated by simulated solar light for atrazine degradation
2023 - MOYA, MURILO T.M.; ARAUJO, LEANDRO G. de; LOPES, FERNANDO S.; TEIXEIRA, ANTONIO C.S.C.
Photocatalysis-based technologies have been proposed for the treatment of wastewater containing atrazine (ATZ), a persistent and recalcitrant pollutant. This study aims to evaluate and compare the efficiency of TiO2 P25 and TiO2 modified with carbon (C–TiO2 Kronos vlp 7000) in the photocatalytic degradation of ATZ in aqueous systems. The experiments were performed in a tubular photochemical reactor equipped with a compound parabolic collector (CPC) irradiated by simulated solar light. The materials were characterized by X-ray diffraction, infrared spectroscopy, BET specific surface area, and diffuse reflectance spectroscopy. For TiO2 P25, ATZ removals varied in the range 86–100 % after 120 min of irradiation, although the total organic carbon (TOC) analyses indicated that no significant ATZ mineralization occurred (<20 %). C–TiO2 Kronos vlp 7000, on the other hand, was not able to completely remove ATZ after 120 min of irradiation. In this case, pesticide removals were 37–45 % over 120 min, while C–TiO2 performed better with regard to ATZ mineralization, with 38 % TOC removal. Given the low mineralization of atrazine, the intermediate compounds formed were identified for each photocatalytic material.
Physicochemical modifications and decolorization of textile wastewater by ozonation
2023 - PRADO, E.S.P.; MIRANDA, F.S.; ARAUJO, L.G. de; FERNANDES, G.L.; PEREIRA, A.L.J.; GOMES, M.C.; SILVA SOBRINHO, A.S. da; BALDAN, M.R.; PETRACONI, G.
This is an experimental study on the decolorization efficiency and the degradation of organic compounds from textile wastewater by the ozonation process in a batch system. The effects of different sample volumes of textile wastewater over time were investigated. The experiments were performed in a 1 L glass reactor with a magnetic stirrer and a bubble diffuser at the bottom to feed the ozone. The applied cumulative ozone dosage varied at 120 gO3 L−1, 60 gO3 L−1, and 30 gO3 L−1, and the total interaction time for each test was 1 h. To investigate the physicochemical properties of the textile wastewater (solid and liquid phases) before and after the treatment, multiple analytical characterization methods were used: Thermal Gravimetric Analysis, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy, X-ray diffraction, Fourier Transform Infrared spectroscopy, and Spectrophotometer. The most perceptive change was observed in the color of the liquid medium, which turned from black to transparent, and a visual color number indicator known as DurchsichtFarbZahl (DFZ) was used for the evaluation of this process. Absorbance values decreased about 3.5 times after 5 min of treatment with a 0.15 L sample volume, and these values differed for tests with larger sample volumes. FTIR spectroscopy demonstrated that the bands’ intensities associated with the C − H, C − N, and C − O decrease during treatment. On the other hand, it was possible to conclude that combining treatment methods to improve the degradation of persistent compounds after the ozonation process is necessary. Finally, the ozonation of the textile wastewater proved to be effective at removing color due to its high reaction capacity.
Experimental study on treatment of simulated radioactive waste by thermal plasma
2021 - PRADO, E.S.P.; MIRANDA, F.S.; ARAUJO, L.G.; PETRACONI, G.; BALDAN, M.R.; ESSIPTCHOUK, A.; POTIENS JUNIOR, A.J.
Thermal plasma technology is a process that demonstrates high performance for the processing of different types of waste. This technology can also be applied in the treatment of radioactive wastes, which requires special care. Beyond that, volumetric reduction, inertization, as well as a cheap and efficient process are necessary. In this context, the purpose of this paper is to demonstrate the application of thermal plasma technology for the treatment of solid radioactive waste. For this, stable Co and Cs were used to simulate compactable and non-compactable radioactive waste; about 0.8 g Co and 0.6 g Cs were added in each experimental test. The experimental tests were conducted using plasma of transferred arc electric discharge generated by the graphite electrode inside the process reactor. The behavior and distribution of the radionuclides present in the waste were assessed during the plasma process. The results show that the significant amounts of Co and Cs leave the melt by volatilization and are transferred to the gas phase with a small portion retained in the molten slag. The retention rate of Co in the slag phase is about 0.03% and 0.30% for compactable and non-compactable waste, respectively. On the other hand, Cs is completely transferred to the gas phase when added to the compactable waste. Conversely, when in the non-compactable waste, only 1.4% Cs is retained.
An algorithmic software model for the characterization of radioactive waste
2021 - TESSARO, ANA P.G.; ARAUJO, LEANDRO G. de; TSUTSUMIUCHI, VICTOR K.; OLIVEIRA JUNIOR, JULIO de; VICENTE, ROBERTO
Non-consolidated information base, repetitive work, and data unreliability are some of the issues that may hamper a radioactive waste characterization program. Therefore, an algorithmic software model for the characterization of radioactive waste is proposed to boost waste management in nuclear-based facilities. The data obtained have enabled the construction of a guide code in the pseudotechnical language. The developed system fully covered the characterization stage, and met the needs identified in the radioactive waste management service. Here, we propose systematic documentation of the characterization methods that are employed during the radioactive waste management processes, besides formulating the system’s data recording.
Use of calcium alginate beads and Saccharomyces cerevisiae for biosorption of 241Am
2020 - ARAUJO, LEANDRO G. de; BORBA, TANIA R. de; FERREIRA, RAFAEL V. de P.; CANEVESI, RAFAEL L.S.; SILVA, EDSON A. da; DELLAMANO, JOSE C.; MARUMO, JULIO T.
Calcium alginate beads, inactivated Saccharomyces cerevisiae and inactivated S. cerevisiae immobilized in calcium alginate beads (S. cerevisiae–calcium alginate beads) are examined as potential biosorption materials as regards their capacity to remove 241Am. In this study, initial experiments were carried out to evaluate the effects of pH (2 and 4) and 241Am initial concentration: 75, 150, and 300 Bq mL-1. The experiments were conducted in a batch reactor. Higher removal capacity was observed at pH 2 with the use of S. Cerevisiae, whereas pH 4 performed better for the essays with calcium alginate beads and S. Cerevisiae-calcium alginate beads. The pseudo-first-order kinetic model described the kinetics of biosorption. Calcium alginate was the adsorbent of choice to further experiments with synthetic organic liquid waste. A lower removal rate was observed in the organic waste, although calcium alginate beads have also been able to achieve high sorption capacity in less than 4 h. With the organic waste, the highest value of sorption capacity of 241Am was 4.38 × 10−7 mmol g−1 with an initial 241Am concentration of 2.31 × 10−8 mmol L−1.
Inventorying the radionuclides in spent cartridge filters from the primary circuit of a nuclear research reactor by the dose-to-activity method
2020 - TESSARO, ANA P.G.; ARAUJO, LEANDRO G. de; VICENTE, ROBERTO
The high activity of spent cartridge filters from the cooling water polishing system of a nuclear research reactor precludes, in routine work of a waste characterization program, the usual method of radiochemical analysis of filter samples. For this waste, the dose-to-activity method, using a gamma spectrometer and a dose rate meter, is an alternative for the determination of the activities of the gamma emitters with acceptable accuracy. The ratio of photon peak-areas from different radionuclides, corrected by the detector energy-dependent efficiency, allowed estimating the proportions between the activities of the different radionuclides present. Finally, the simulation of the counting geometry, using the point-kernel method to estimate the air dose rate resulting from an arbitrary concentration of those radionuclides and the comparison of the calculated with the measured air dose rate have yielded the needed estimates of the activity concentrations. The aim of this paper is to report the development of the method applied for the determination of the concentration of the gamma-emitters present in cartridge filters from the IEA-R1 Nuclear Research Reactor.