LEANDRO GOULART DE ARAUJO

LEANDRO GOULART DE ARAUJO

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Uranium biosorption by hydroxyapatite and bone meal
2022 - WATANABE, TAMIRES; GUILHEN, SABINE N.; MARUMO, JULIO T.; SOUZA, RODRIGO P. de; ARAUJO, LEANDRO G. de
Biosorption has been examined for the treatment of aqueous solutions containing uranium, a radiotoxic pollutant. Nevertheless, the evaluation of the role of process variables by experimental design on the use of hydroxyapatite and bone meal as biosorbents for uranium has not yet been previously addressed. In this study, the effects of adsorbent dosage (M), initial uranium concentrations ([U]0), and solution pH were investigated, using a two-level factorial design and response surface analysis. The experiments were performed in batch, with [U]0 of 100 and 500 mg L−1, pH 3 and 5, and adsorbent/uranium solution ratios of 5 and 15 g L−1. Contact time was fixed at 24 h. Removal rates were higher than 88%, with a maximum of 99% in optimized conditions. [U]0 and M were found to be the most influential variables in U removal in terms of adsorption capacity (q). The experiments revealed that bone meal holds higher adsorption capacity (49.87 mg g−1) and achieved the highest uranium removal (~ 100%) when compared to hydroxyapatite (q = 49.20 mg g−1, removal = 98.5%). The highest value of q for both biomaterials was obtained for [U]0 = 500 mg L−1, pH 3, and M = 5 g L−1. Concerning the removal percentage, bone meal achieved the best performance for [U]0 = 500 mg L−1, pH 3, and M = 15 g L−1. Further experiments were made with real radioactive waste, resulting in a high uranium adsorption capacity for both materials, with 22.11 mg g−1 for hydroxyapatite and 22.08 mg g−1 for bone meal, achieving uranium removal efficiencies higher than 99%.
Enhanced removal of radium from radioactive oil sludge using microwave irradiation and non-ionic surfactant
2022 - LINHARES, VANESSA do N.; ARAUJO, LEANDRO G. de; VICENTE, ROBERTO; MARUMO, JULIO T.
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.
Biossorção de urânio por meio de hidroxiapatita e farinha de osso
2021 - WATANABE, TAMIRES; MARUMO, JULIO T.; ARAUJO, LEANDRO G. de
Preliminary studies on electron beam irradiation as a treatment method of radioactive oil sludge
2021 - TESSARO, A.P.G.; VICENTE, R.; MARUMO, J.T.; TEIXEIRA, A.C.S.C.; ARAUJO, L.G.
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.
Radioanalytical methods for sequential analysis of actinide isotopes in activated carbon filter‑bed waste
2020 - GERALDO, BIANCA; ARAUJO, LEANDRO G. de; VICENTE, ROBERTO; TADDEI, MARIA H.T.; CHEBERLE, SANDRA M.; MARUMO, JULIO T.
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.
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.
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.
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.