LEANDRO GOULART DE ARAUJO

LEANDRO GOULART DE ARAUJO

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Computational fluid dynamic simulation of a gas-solid fluidized bed system
2019 - OLIVO-ARIAS, L.P.; ARAUJO, L.G. de; ROJAS-TRIGOS, J.B.
The study of the gas-solid system was performed through an analysis of computational fluid dynamics (CFD) in a fluidized bed reactor. This process begins with the interaction between the particles and the gas phase. The fluidization process analysis is achieved through the Eulerian approach represented in the behavior of the solid phase dynamics during the bed expansion process. Within the process, the formation of the dense phase was demonstrated and how it could affect the effects of temperature, pressure and surface velocity of the gas in the fluidized bed system. The purpose of this work is to establish hydrodynamic parameters by evaluating the volumetric fraction of the particles and the axial and radial velocity profile using the drag models of Syamlal O'Brien and Gibilaro. In addition, it should be considered the analysis of the computational dynamics of fluids, such as the generation of the mesh, the selection of the models, and the run time of the simulation. The results of the simulations showed that the solid phase concentration has had a uniform distribution, a dense phase formation, given the changes in operating conditions and a reasonable expansion of the bed in the final simulation time.
Disposal of a pretreated oil sludge by the cementation method
2019 - WATANABE, NAOMI; SILVA, THALITA T.; MARUMO, JULIO T.; ARAUJO, LEANDRO G. de
Hydrothermal and assisted microwaved syntheses of Stanno and Yttrium metallosilicates as heterogeneous catalyst for biodiesel production and environmental remediation
2019 - NERY, JOSE G.; RATERO, DAVI R.; SILVA, DANILO A. da; MARUMO, JULIO T.; ARAUJO, LEANDRO G. de; MEDEIROS, VINICIUS L.
This study reports the synthesis, physicochemical characterization by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and solid-state MAS NMR (1H, 23Na, 29Si and 89Y and 119Sn MAS NMR) of a stanno and yttrium metallosilicate and their application as a heterogeneous catalyst for biodiesel production via ethanolysis and methanolysis routes using edible, non-edible an waste oils as feedstocks and environmental remediation. Heterogenous catalytic studies in the transesterification of refined edible, non-edible, and waste oils have resulted in high yields of FAMEs and FAEEs (fatty acid methyl and ethyl esters), nevertheless the highest FAMES (98.2%) and FAEEs (96.6%) yields were obtained for non-edible microalgae oil extracted from the genetically modified heterotrophic algal strain Prototheca moriformis. Catalytic studies also using nonedible macaw palm oil (Acrocomia aculeata) with a high content of free fatty acids (FFAs) demonstrated that the catalyst could simultaneously perform esterification and transesterification reactions using using different sources of lipids feedstocks, notably those that do not compete with food production [1]. On the other hand, Yttrium metallosilicate were very efficient in the separation, binding and chemical stabilization of hazardous inorganic, organic and radioactive species such as lead ( Pb2+, Cd2+, Ba2+ , Cs+ and Sr2+) in aqueous systems.
Oxidative degradation of organic compounds from sludge by ozonation
2019 - ARAUJO, LEANDRO G. de; WATANABE, NAOMI; SILVA, THALITA T.; TEIXEIRA, ANTONIO C.S.C.; VELOSA, ADRIANA C. de; MARUMO, JULIO T.
This study investigates the performance of the ozonation process in the treatment of petroleum sludge from an offshore production platform situated in Brazil. The effect of operating conditions is studied such as the phase to be treated and the sludge/water ratio. Total organic carbon content increased in O2 and O3 experiments, mainly because of the mixing factor. The decrease of sludge mass was observed in a situation of forced mixing and with only ozone flow. The liquid phase indicated a high TOC value, but very low radioactive activities, whereas the solid phase did not present detectable TOC amounts but significant values of radioactive activity. More experiments and analyzes will be carried out to obtain more relevant results for future discussion.
Radiochemical characterization of spent filter cartridges from the primary circuit of a research reactor
2019 - GERALDO, BIANCA; ARAUJO, LEANDRO G. de; TADDEI, MARIA H.T.; FERREIRA, MARCELO T.; MADUAR, MARCELO F.; VICENTE, ROBERTO; MARUMO, JULIO T.
Radiochemical-based analyses have been used for the characterization of radioactive waste. Nevertheless, the determination of alpha, beta and gamma emitters by radiochemical analysis of spent cartridge filters from a swimming-pool type reactor has not been previously addressed. This work aims at identifying and quantifying the radionuclides present in this waste, including the difficult to measure radionuclides. The distribution of the radionuclides in the filter was investigated by the determination of gamma-emitting nuclides and the z-score of the measured activity concentrations. The results indicated that all the filters are homogeneous, meeting the homogeneity criteria recommended by the International Atomic Energy Agency.
Brazilian clays as potential buffer materials for radioactive waste final storage
2019 - MACHADO, GABO G.; GUILHEN, SABINE N.; KRUPSKAYA, VICTORIA V.; ZAKUSIN, SERGEY V.; TYUPINA, EKATERINA A.; HARADA, JULIO; VICENTE, ROBERTO; SOUZA, RODRIGO P. de; ARAUJO, LEANDRO G. de; ESPINOSA, DENISE C.R.
Clayey materials have been adopted in most nuclear waste producing countries, as a key constituent in engineered barrier for final disposal facilities at all levels of radioactive wastes (LILW-SL, LILW-LL and HLW). The following study presents a thorough characterization upon five Brazilian clay rich deposits, mostly smectite bearing clays, aiming to evaluate their expected performance as clay buffer under the conditions associated to a Low and Intermediate Level Waste Repository (RBMN); being the former a matter of national strategic interest. Samples coming from the Brazilian states of Bahia, Maranhão, Pará and Paraíba were treated and analyzed by means of X-Ray diffraction as a main technique, and complemented by FTIR, LALLS, XRF and SEM-EDS, in order to stablish mineralogical composition, particle size distribution and chemical composition. Moreover, several standard clay treatments over the <1 μm size fraction were carried out to reveal information regarding layer charge, major interlayer cations, unit formula and other crystal features of smectite species present in a mineralogical assembly, enabling the construction of a molecular model over which would be realistic to simulate the diffusion of radionuclides. Results obtained on 133Cs adsorption experiments indicate that mineralogical composition would probably be the single most influential factor controlling transport capacity of positively charged radionuclides in the current setup, and can be expressed in terms of smectite contents, favoring montmorillonite rich materials containing majorly Na+ as compensating cation in interlayer position. Thus, the obtained data will be useful in the testing of optimal compaction conditions to obtain the most suitable buffer material for the repository design. However, this trend is yet to be contrasted against hydraulic conductivity measurements and swelling pressure to see how they match.
Oil sludge treatment by electron beam irradiation
2019 - TESSARO, ANA P.G.; CASAS, ALEXANDRE L.; TEIXEIRA, ANTONIO C.S.C.; VICENTE, ROBERTO; MARUMO, JULIO T.; ARAUJO, LEANDRO G. de
Radiation induced advanced oxidation processes have been proposed for the treatment of various types of wastes. However, electron beam technologies for the removal of recalcitrant compounds in petroleum wastes are still poorly understood. This work aims at evaluating the effects on the degradation of organic matter from oil sludge by electron beam irradiation. The radiometric analysis was also performed to identify radionuclides and measure dose rates. An electron beam accelerator, model Dynamitron II, with variable current up to 25 mA was employed and the irradiation dose values ranged from 20 to 250 kGy. Solutions were prepared with an initial H2O2 concentration of 1.34 mol L 1. Samples without H2O2 addition, but with water were also evaluated. Control tests with dry and pulverized sludge were submitted to irradiation. The effects on the removal of total organic carbon and the sludge degradation are discussed.
Reaction of ion exchange resins with Fenton's reagent
2018 - ARAUJO, LEANDRO G. de; MARUMO, JULIO T.
One of the most common treatment methods for spent ion exchange resins is their immobilization in cement, which reduces the release of radionuclides into the environment. Although this method is efficient, it considerably increases the final volume of the waste due to its low incorporation capacity. This work aims to evaluate the degradation of ion exchange resins by the Fenton process (H2O2/Fe (2+)). The resin evaluated was a mixture of cationic and anionic resins, both non-radioactive. The reactions were conducted by varying the catalyst concentration (25, 50, 100, and 150 mmol L-1) and the volume of hydrogen peroxide. Three different temperatures were evaluated by varying the flow of reactants, which were 50, 60, and 70 degrees C. Cement specimens were prepared from the treated solutions and two parameters were assessed-namely, final setting time and axial compressive strength. The results showed that the experimental conditions were suitable to dissolve the resins, and the Fe3+ produced as precipitate during the experiments increased the resistance of the final product. The immobilized product complied with the limits established by regulation.
Chemical analysis of radioactive mixed liquid wastes by alpha/gamma spectrometry, ICP-OES and arsenazo III
2013 - FERREIRA, EDUARDO G.A.; FERREIRA, RAFAEL V.P.; ARAUJO, LEANDRO G.; TADDEI, MARIA H.T.; DELLAMANO, JOSE C.; MARUMO, JULIO T.
Evaluation of the resin oxidation process using Fento's reagent
2013 - ARAUJO, LEANDRO G.; GOES, MARCOS M.; MARUMO, JULIO T.