Navegação Periódicos - Artigos por autor "10132"

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  • IPEN-DOC 29688

    ARAUJO, LEANDRO G. de ; MEDEIROS, VINICIUS L.; GUARNIERI, GUILHERME de P.; SILVA, DANILO A. da; WATANABE, TAMIRES ; MARUMO, JULIO T. ; NERY, JOSE G.. An adsorption agent based on chitosan–zeolite composite: environmental and radioactive liquid waste remediation. Environmental Science: Advances, v. 2, n. 3, p. 484–494, 2023. DOI: 10.1039/d2va00148a

    Abstract: In this article, we present a chitosan–zeolite composite, which was synthesized and used as an adsorbent material for caesium (Cs) removal from aqueous media and real liquid radioactive organic waste (LROW). The compound was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy techniques. The physicochemical characterization indicates the production of a composite. Adsorption experiments were first performed using the prepared solutions contaminated with Cs using full factorial design with two variables of interest: initial Cs concentration (Cs0) and adsorbent dosage (mg L−1 ). The results indicated a high caesium removal rate with removal values above 93% and adsorption capacity of up to 10 mg g−1 . With the best experimental conditions according to our experimental domain, time was evaluated and equilibrium was reached in 180 min. Finally, the adsorbent material was tested as an adsorbent for Cs, Am, and U from LROW. When in contact with LORW, the removal rates (%) were 21.51 (137Cs), 26.39 (241Am), and 20.26 (U (total)). Although lower, this material indicated that it has the potential to be used for multi-elemental adsorption.

    Palavras-Chave: adsorption; chitin; zeolites; polysaccharides; radioactive wastes; liquid wastes; radioactive effluents

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  • IPEN-DOC 28316

    TESSARO, ANA P.G. ; ARAUJO, LEANDRO G. de ; TSUTSUMIUCHI, VICTOR K. ; OLIVEIRA JUNIOR, JULIO de ; VICENTE, ROBERTO . An algorithmic software model for the characterization of radioactive waste. Journal of Radioanalytical and Nuclear Chemistry, v. 330, n. 1, p. 279–292, 2021. DOI: 10.1007/s10967-021-07934-2

    Abstract: 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.

    Palavras-Chave: algorithms; nuclear data collections; radioactive waste management; site characterization

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  • IPEN-DOC 28879

    ARAUJO, LEANDRO G. de ; VIEIRA, LUDMILA C. ; CANEVESI, RAFAEL L.S.; SILVA, EDSON A. da; WATANABE, TAMIRES ; FERREIRA, RAFAEL V. de P.; MARUMO, JULIO T. . Biosorption of uranium from aqueous solutions by Azolla sp. and Limnobium laevigatum. Environmental Science and Pollution Research, v. 29, n. 30, p. 45221-45229, 2022. DOI: 10.1007/s11356-022-19128-8

    Abstract: The main goal of this study was to assess alternatives to the current challenges on environmental quality and circular economy. The former is here addressed by the treatment of radioactively contaminated solutions, and the latter by using abundant and low-cost biomass. In this paper, we examine the biosorption of hexavalent uranium (U(VI)) in a batch system using the macrophytes Limnobium laevigatum and Azolla sp. by three operational parameters: biomass dose, metal ion concentration, and contact time. Simulated solutions were firstly addressed with two biomasses, followed by studies with real liquid organic radioactive waste (LORW) with Azolla sp. The batch experiments were carried out by mixing 0.20 g biomass in 10 mL of the prepared solution or LORW. The total contact time employed for the determination of the equilibrium times was 240 min, and the initial U(VI) concentration was 0.63 mmol L−1. The equilibrium times were 15 min for L. laevigatum and 30 min for Azolla sp. respectively. A wide range of initial U(VI) concentrations (0.25–36 mmol L−1) was then used to assess the adsorption capacity of each macrophyte. Isotherm models validated the adsorption performance of the biosorption process. Azolla sp. presented a much higher U(VI) uptake (0.474 mmol g−1) compared to L. laevigatum (0.026 mmol g−1). When in contact with LORW, Azolla sp. removed much less uranium, indicating an adsorption capacity of 0.010 mmol g−1. In conclusion, both biomasses, especially Azolla sp., can be used in the treatment of uranium-contaminated solutions.

    Palavras-Chave: sorption; uranium; aquatic organisms; radioactive waste management

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  • IPEN-DOC 27907

    MACHADO, G.G.; KRUPSKAYA, V.V.; ZAKUSIN, S.V.; HARADA, J.; VICENTE, R. ; SOUZA, R.P.; ARAUJO, L.G. ; MONTALVAN, E.T.; ESPINOSA, D.C.R.; KAHN, H.; GUILHEN, S.N. . Brazilian clays for environmental solutions applied to radioactive waste management. Brazilian Journal of Radiation Sciences, v. 9, n. 1A, p. 1-14, 2021. DOI: 10.15392/bjrs.v9i1A.1539

    Abstract: Clayey materials have been adopted in most nuclear waste producing countries as a key constituent in engineered barrier systems 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 barrier under the conditions associated to a Low and Intermediate Level Waste Repository; being the former a matter of national strategic interest. Samples coming from the Brazilian states of Paraná, Bahia, Paraíba, and Maranhão were treated and analyzed by means of X-Ray diffraction as main technique. Other techniques such as FTIR, LALLS, XRF, and SEM-EDS, were performed in order to establish the 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, aiming to provide information for 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. The composition is especially expressed in terms of smectite contents, favoring montmorillonite rich materials containing majorly Na+ as compensating cation in interlayer position. All tested samples can be considered as suitable candidates to be used in the design of final destination storage for nuclear waste. Thus, efficiency on 133Cs adsorption trials also indicate that these materials could have potential uses as sorptive matrices (Sorbents) for water treatment of radionuclide polluted waters such as TENORM waste waters. However, these trends are yet to be contrasted against hydraulic conductivity measurements and swelling pressure in order to have a more comprehensive perspective of this clayey prospects as barrier enhanced layer; aligned to the multilayer barrier system approach for nuclear waste management.

    Palavras-Chave: radioactive waste storage; fourier transformation; infrared spectra; cesium 133; clays

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  • IPEN-DOC 27759

    OLIVO-ARIAS, L.P.; ARAUJO, L.G. de ; ROJAS-TRIGOS, J.B.. Computational fluid dynamic simulation of a gas-solid fluidized bed system: a dense phase analysis. Latin-American Journal of Physics Education, v. 13, n. 4, p. 4308-1 - 4308-9, 2019.

    Abstract: 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.

    Palavras-Chave: fluid mechanics; computers; fluidized bed reactors; reactors; two-phase flow; hydrodynamic model; solids; volume measurement; computer calculations; computerized simulation

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  • IPEN-DOC 28679

    LINHARES, VANESSA do N. ; ARAUJO, LEANDRO G. de ; VICENTE, ROBERTO ; MARUMO, JULIO T. . Enhanced removal of radium from radioactive oil sludge using microwave irradiation and non-ionic surfactant. Journal of Petroleum Science and Engineering, v. 211, p. 1-10, 2022. DOI: 10.1016/j.petrol.2022.110168

    Abstract: Surfactant-based technologies have been studied for the treatment of radioactive waste containing isotopes of radium. Nevertheless, the use of combined processes to remove radium from radioactive oil sludge is scarce in the literature. The objective of this work was to investigate the potential of a non-ionic surfactant to remove radium from raw oil sludge (ROS) and pre-treated, microwave-irradiated oil sludge (POS). Characterization of ROS and POS was made using the following methods: Thermal Gravimetric Analysis, X-ray diffraction, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy, and gamma spectrometry. The effects of surfactant concentration (0.5–7.5%), temperature (25-60 °C), and contact time (30 and 60 min) were investigated. For ROS, little or no influence on the decontamination process was found for variations in the selected process parameters. For POS, the lowest surfactant concentration (2.5%) was the most efficient, removing about 94% of 226Ra and 228Ra. Neither contact time nor temperature affected removal. For ROS, removal percentages were 50–60% for 226Ra and 35–45% for 228Ra. The results indicated that the surfactant acted more efficiently in the decontamination of POS.

    Palavras-Chave: oils; sludges; radioactive wastes; surfactants; radioisotopes; microwave radiation

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  • IPEN-DOC 28406

    PRADO, E.S.P. ; MIRANDA, F.S.; ARAUJO, L.G. ; PETRACONI, G.; BALDAN, M.R.; ESSIPTCHOUK, A.; POTIENS JUNIOR, A.J. . Experimental study on treatment of simulated radioactive waste by thermal plasma: temporal evaluation of stable Co and Cs. Annals of Nuclear Energy, v. 160, p. 1-6, 2021. DOI: 10.1016/j.anucene.2021.108433

    Abstract: 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.

    Palavras-Chave: radioactive wastes; plasma; waste processing; thermochemical processes

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  • IPEN-DOC 26878

    TESSARO, ANA P.G. ; ARAUJO, LEANDRO G. de ; VICENTE, ROBERTO . Inventorying the radionuclides in spent cartridge filters from the primary circuit of a nuclear research reactor by the dose-to-activity method. Radiation Physics and Chemistry, v. 171, p. 1-6, 2020. DOI: 10.1016/j.radphyschem.2020.108710

    Abstract: 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.

    Palavras-Chave: radioactive waste management; calculation methods; radioisotopes; gamma spectrometers; filters; iear-1 reactor; inventories; solid wastes; dose rates

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  • IPEN-DOC 29681

    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.. Physicochemical modifications and decolorization of textile wastewater by ozonation: performance evaluation of a batch system. Ozone: Science and Engineering, v. 45, n. 3, p. 276-290, 2023. DOI: 10.1080/01919512.2022.2088470

    Abstract: 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.

    Palavras-Chave: textile industry; waste water; ozonization; dyes; removal

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  • IPEN-DOC 27144

    ARAUJO, LEANDRO G. de ; PRADO, EDUARDO S.P. ; MIRANDA, FELIPE de S.; VICENTE, ROBERTO ; SILVA SOBRINHO, ARGEMIRO S. da; PETRACONI FILHO, GILBERTO; MARUMO, JULIO T. . Physicochemical modifications of radioactive oil sludge by ozone treatment. Journal of Environmental Chemical Engineering, v. 8, n. 5, p. 1-8, 2020. DOI: 10.1016/j.jece.2020.104128

    Abstract: An experimental study on the degradation of organic compounds from radioactive oil sludge by the ozonation process is presented. The effects of different concentrations of ozone in the oil sludge degradation over time were investigated. The experiments were performed in a 0.125 L glass reactor with magnetic stirring and a diffuser plate at the bottom to feed the ozone. The ozone concentration varied from 13 to 53 mg L−1 and the total interaction time was 1 h. To investigate the physicochemical properties of the oil sludge (solid and liquid components) prior to and after the treatment, multiple analytical characterization methods were used: Thermal Gravimetric Analysis, X-ray diffraction, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy, Fourier Transform Infrared spectroscopy, Spectrophotometer, and Residual Gas Analyzer. The most perceptive change is in the color of the liquid medium turned from dark brown to light yellow, especially under ozone concentrations higher than 33 mg L−1. Absorbance values decreased about 3.5 times after 30 min of treatment with [O3] =53 mg L−1. FTIR spectroscopy showed that the bands associated with the CH3 and CeH in CH2 disappeared during treatment. On the other hand, a greater presence of C]C aromatics was observed. By residual gas analysis, various organic and inorganic gases were identified during the treatment, such as CH4, H2, CO2, and H2S. Finally, the ozonation of the oil sludge proved to be effective, due to its high reaction capacity.

    Palavras-Chave: ozone; therapy; ozonization; radioactivity; sludges; oxidation; naturally occurring radioactive materials; fourier transformation; thermal gravimetric analysis

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  • IPEN-DOC 27884

    TESSARO, A.P.G. ; VICENTE, R. ; MARUMO, J.T. ; TEIXEIRA, A.C.S.C.; ARAUJO, L.G. . Preliminary studies on electron beam irradiation as a treatment method of radioactive oil sludge. Brazilian Journal of Radiation Sciences, v. 9, n. 1A, p. 1-16, 2021. DOI: 10.15392/bjrs.v9i1A.1416

    Abstract: 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. Characterization methods were employed to identify the chemical elements present in the waste. Radiometric analysis was performed to identify radionuclides and measure dose rates. Preliminary immobilization of the untreated waste with cement indicated resistance values very close to the minimum established in national regulation. To treat the waste, an electron beam accelerator, model Dynamitron II, with variable current up to 25 mA was employed and the irradiation doses ranged from 20 to 200 kGy. Solutions were prepared with an initial H2O2 concentration of 1.34 mol·L-1. The effects on the removal of total organic carbon are discussed.

    Palavras-Chave: dose rates; electron beams; irradiation; oils; radiation dose ranges; radioactive waste processing; radioactive wastes; radioisotopes; radiometric analysis; sludges

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  • IPEN-DOC 29635

    TESSARO, ANA P.G. ; ARAUJO, LEANDRO G. de ; SILVA, THALITA T. ; COELHO, EDNEI; CORREA, BENEDITO; ROLINDO, NATALIE C. ; VICENTE, ROBERTO . Prospects for fungal bioremediation of unburied waste packages from the Goiânia radiological accident. Environmental Science and Pollution Research, v. 30, n. 14, p. 41045-41059, 2023. DOI: 10.1007/s11356-023-25247-7

    Abstract: Goiânia, the Goiás State capital, starred in 1987, where one of the largest radiological accidents in the world happened. A teletherapy machine was subtracted from a derelict radiotherapy clinic and disassembled by scavengers who distributed fragments of the 50 TBq 137CsCl source among relatives and acquaintances, enchanted by the blue shine of the substance. During the 15 days before the accident was acknowledged, contaminated recycling materials were delivered to recycling factories in four cities in the state of São Paulo, Brazil, in the form of recycling paper bales. The contaminated bales were spotted, collected, and stored in fifty 1.6 m3 steel boxes at the interim storage facility of the Nuclear and Energy Research Institute (IPEN). In 2017, a check of the content was performed in a few boxes and the presence of high moisture content was observed even though the bales were dry when conditioned and the packages were kept sealed since then. The main objective of this work was to report the fungi found in the radioactive waste after they evolved for 30 years in isolation inside the waste boxes and their role in the decay of the waste. Examination of the microbiome showed the presence of nematodes and fungal communities. The fungi species isolated were Aspergillus quadricinctus, Fusarium oxysporum, Lecanicillium coprophilumi, Scedosporium boydii, Scytalidium lignicola, Xenoacremonium recifei, and Pleurostoma richardsiae. These microorganisms showed a significant capacity to digest cellulose in our trials, which could be one of the ways they survive in such a harsh environment, reducing the volume of radioactive paper waste. These metabolic abilities give us a future perspective of using these fungi in biotechnology to remediate radioactively contaminated materials, particularly cellulose-based waste.

    Palavras-Chave: radiation accidents; cesium 137; waste management; fungi; radioactive wastes; brazil

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  • IPEN-DOC 27429

    GERALDO, BIANCA ; ARAUJO, LEANDRO G. de ; VICENTE, ROBERTO ; TADDEI, MARIA H.T.; CHEBERLE, SANDRA M.; MARUMO, JULIO T. . Radioanalytical methods for sequential analysis of actinide isotopes in activated carbon filter‑bed waste. Journal of Radioanalytical and Nuclear Chemistry, v. 326, p. 1559-1568, 2020. DOI: 10.1007/s10967-020-07435-8

    Abstract: In this work, we compare methods for the sequential determination of U and the transuranium elements Np, Pu, Am, and Cm. The chemical yield, the time spent in the analysis, the amount of secondary waste, and the costs of each method are the aspects of interest. Two methods were compared: extraction chromatography (EC) and ion exchange plus extraction chromatography (IE + EC). The chemical yields of (EC) and (IE + EC) were similar for all radionuclides. The (EC) method is the more effective with respect to time of analysis, the amount of secondary waste and costs.

    Palavras-Chave: radioisotopes; radiochemistry; cost benefit analysis; ion exchange; radiopharmaceuticals; tracer techniques

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  • IPEN-DOC 26681

    GERALDO, BIANCA ; ARAUJO, LEANDRO G. de ; TADDEI, MARIA H.T.; FERREIRA, MARCELO T.; MADUAR, MARCELO F. ; VICENTE, ROBERTO ; MARUMO, JULIO T. . Radiochemical characterization of spent filter cartridges from the primary circuit of a research reactor. Journal of Radioanalytical and Nuclear Chemistry, v. 322, n. 3, p. 1941-1951, 2019. DOI: 10.1007/s10967-019-06864-4

    Abstract: 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.

    Palavras-Chave: alpha decay radioisotopes; beta decay radioisotopes; filters; gamma decay; pool type reactors; radioactive waste management; radioactive wastes; radioactivity; radiochemical analysis; research reactors

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  • IPEN-DOC 28854

    GUILHEN, SABINE N. ; WATANABE, TAMIRES ; SILVA, THALITA T. ; ROVANI, SUZIMARA; MARUMO, JULIO T. ; TENORIO, JORGE A.S.; MASEK, ONDREJ; ARAUJO, LEANDRO G. de . Role of point of zero charge in the adsorption of cationic textile dye on standard biochars from aqueous solutions: selection criteria and performance assessment. Recent Progress in Materials, v. 4, n. 2, p. 1-20, 2022. DOI: 10.21926/rpm.2202010

    Abstract: The point of zero charge (PZC) is an inherent electrokinetic property of biochars (BC). It influences the adsorption process under certain pH conditions. Herein, we report the method of determination of the PZC values of ten standard BCs. We used the salt addition method to select the BCs with suitable properties for methylene blue (MB) removal from aqueous solutions. The standard BCs were obtained by pyrolyzing five different biomasses at two distinct temperatures (550°C and 700°C). The BCs derived from rice husk (pHPZC at 7.22 and 7.64 for RH550 and RH700, respectively) and softwood pellets (pHPZC at 6.57 and 6.78 for SWP500 and SWP700, respectively) were selected for their compatibility with cationic dyes such as MB. Results from adsorption experiments indicated the potential use of the RH biochar as an adsorbent for the removal of MB from aqueous solutions. The removal efficiencies were 68.83% and 71.97% for RH550 and RH700, respectively. Considerably low values were obtained for SWP550 and SWP700 (21.61% and 22.84%, respectively). Equilibrium was achieved at 2 h for RH550 and 1 h for RH700, and the adsorption kinetics for the RH BCs could be described by a pseudo-second order equation. The results revealed that even when produced under comparable conditions, BCs obtained from different feedstocks exhibited different cationic dye removing abilities. BCs optimized for the removal of cationic or anionic dyes can be easily engineered by appropriately matching the feedstock with the processing conditions.

    Palavras-Chave: point charge; adsorption; biomass; chars; methylene blue; salts; dyes

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  • IPEN-DOC 27764

    OLIVO-ARIAS, L.P.; ARAUJO, L.G. . Structural analysis of polydimethylsiloxane samples. Latin-American Journal of Physics Education, v. 14, n. 3, p. 3309-1 - 3309-11, 2020.

    Abstract: This work presents a structural analysis of polydimethylsiloxane (PDMS) samples through the study of the mechanical properties of a soft material. For this, the dimensions of the crosslinking samples were modified taking a cure ratio as a reference, to determine the stress-strain, applying the Prony model which the Ansys-Mechanical platform offers. Experimental data was collected from the literature and a force test was performed on three different cylindrical samples (10:1 ratio) of PDMS with a curing agent. Consistent results of the modulus of elasticity as a function of time were obtained. Finally, using the Neo Hookean model, with consideration of hyperelastic material, and employing longer relaxation times, the results showed interesting findings in the parameters of total and directional deformation and other viscoelastic properties for this type of material.

    Palavras-Chave: polymers; mechanical properties; fluids; hydrodynamics; computer calculations; viscosity; elasticity

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  • IPEN-DOC 27250

    MEDEIROS, VINICIUS L.; ARAUJO, LEANDRO G. de ; RATERO, DAVI R.; PAULA, ALEX S.; MOLINA, EDUARDO F.; JAEGER, CHRISTIAN; MARUMO, JULIO T. ; NERY, JOSE G.. Synthesis and physicochemical characterization of a novel adsorbent based on yttrium silicate: a potential material for removal of lead and cadmium from aqueous media. Journal of Environmental Chemical Engineering, v. 8, n. 4, p. 1-10, 2020. DOI: 10.1016/j.jece.2020.103922

    Abstract: A new metallosilicate based on yttrium was synthesized and characterized by XRD, FT-IR, 29Si MAS-NMR, and 89Y MAS-NMR. The mixed framework of the material was confirmed by the detection of distinct chemical shift groups using 29Si MAS-NMR (at -82 to -87 ppm, -91 to -94 ppm, -96 to -102 ppm, and -105 to -108 ppm), as well as four distinct chemical shifts in the 89Y MAS-NMR spectrum (at -89, -142, -160, and -220 ppm). Adsorption and kinetic analyses indicated the potential of the new material for the removal of lead and cadmium from aqueous media. The adsorption results for lead indicated that dynamic equilibrium was reached after five hours, with total lead removal of around 94 %, while for cadmium it was reached in the first hour, with total cadmium removal of around 74 %. The adsorptions of lead and cadmium were modeled using pseudo-first order (PFO) and pseudo-second order (PSO) kinetic models. Although both models provided high R2 values (0.9903 and 0.9980, respectively), the PSO model presented a much lower χ2 red value (4.41×10−4), compared to the PFO model (2.12×10−3), which indicated that the rate-limiting step was probably due to the chemisorption of lead from the solution onto the yttrium-based metallosilicate.

    Palavras-Chave: adsorbents; yttrium silicates; chemisorption; adsorption; aqueous solutions; lead; cadmium; silicon 29; yttrium 89; nuclear magnetic resonance

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  • IPEN-DOC 28419

    OLIVO-ARIAS, L.P.; ARAUJO, L.G. . The influence of the initial gas distribution on the dynamics of a three-phase fluidized bed reactor: non-ideal gas condition. Latin-American Journal of Physics Education, v. 15, n. 1, p. 1312-1 - 1312-6, 2021.

    Abstract: The hydrodynamic evolution of a three-dimensional (3D) liquid-gas-solid fluidized bed reactor was studied using computational fluid dynamics (CFD) simulations, and the results were compared with previous experimental data. The gas-solid and liquid-solid interactions were calculated using the Euler-Euler model, incorporating the kinetic theory for the solid phase. The momentum exchange coefficients for the fluid-solid interactions were calculated using the Gidaspow drag model, and the fluid-fluid interactions by using the Schiller-Naumann model. The predicted gas volume fraction agreed to the Kumar model and showed better performance with the use of higher-order discretization. Furthermore, the Peng Robinson thermodynamic correlation was used to determine the properties of the materials under high severity conditions. The results showed a consistent distribution of the phases, it was quite uniform and there was a reasonable expansion of the bed when gas injection was established as an initial condition.

    Palavras-Chave: computer calculations; dynamics; hydrodynamics; fluidized beds

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  • IPEN-DOC 27180

    FERREIRA, RAFAEL V. de P.; ARAUJO, LEANDRO G. de ; CANEVESI, RAFAEL L.S.; SILVA, EDSON A. da; FERREIRA, EDUARDO G.A. ; PALMIERI, MAURICIO C.; MARUMO, JULIO T. . The use of rice and coffee husks for biosorption of U (total), 241Am, and 137Cs in radioactive liquid organic waste. Environmental Science and Pollution Research, v. 27, n. 29, SI, p. 36651-36663, 2020. DOI: 10.1007/s11356-020-09727-8

    Abstract: Rice and coffee husks (raw and chemically activated) are examined as potential biosorption materials regarding their capacity to remove U (total), 241Am, and 137Cs. The physical parameters evaluated were the morphological characteristics of the biomass, real and apparent density, and surface area. Contact times for the batch experiments were 0.5, 1, 2, and 4 h, and the concentrations tested ranged between 10% of the total concentration and the radioactive waste itself without any dilution. The results were evaluated by experimental sorption capacity, ternary isotherm, and kinetics models. The kinetics results showed that equilibrium was reached after 2 h for all biomass. Raw coffee husk showed the best adsorption results in terms of maximum capacity (qmax) for all three radionuclides, which were 1.96, 39.4 × 10−6, and 46.6 × 10−9 mg g−1 for U, Am, and Cs, respectively. The biosorption process for the raw and activated rice husks was best represented by the Langmuir ternary isotherm model with two sites. For the coffee husk, in the raw and activated states, the biosorption process was best described by the modified Jain and Snoeyink ternary model. These results suggest that biosorption with these biomaterials can be applied in the treatment of liquid organic radioactive waste containing mainly uranium and americium.

    Palavras-Chave: bioadsorbents; biomass; fourier transformation; infrared radiation; rice; liquid wastes; organic compounds; uranium; americium; cesium; coffee beans; gamma spectroscopy

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  • IPEN-DOC 27397

    PRADO, EDUARDO S.P.; MIRANDA, FELIPE S.; ARAUJO, LEANDRO G. de ; PETRACONI, GILBERTO; BALDAN, MAURICIO R.. Thermal plasma technology for radioactive waste treatment: a review. Journal of Radioanalytical and Nuclear Chemistry, v. 325, n. 2, p. 331-342, 2020. DOI: 10.1007/s10967-020-07269-4

    Abstract: In this paper, a review of radioactive wastes treatment using thermal plasma technology is presented as a treatment method for radioactive waste management.Virtually all waste streams can be treated by the thermal plasma technologies, resulting in a conditioned product, free from organics and liquids, definitely meeting the acceptance criteria for safe storage and disposal. The application of the thermal plasma system in the nuclear area is still one of the current research topics due to the theoretical and practical complexity of the treatment. This paper discusses the performance of the thermal plasma systems, addressing the advantages and limitations of the method.

    Palavras-Chave: plasma technology; radioactive waste management; radioactive waste processing; management; processing

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