MAURICIO TIOKAZU OSHIRO

MAURICIO TIOKAZU OSHIRO

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Adsorption isotherms for the removal of Am-241 in radioactive liquid wastes using magnetite nanoparticles
2017 - OSHIRO, MAURICIO T.; SAKATA, SOLANGE K.; POTIENS JUNIOR, ADEMAR J.
Americium-241 (Am-241) is a radionuclide with half-life of 432 years, emitting alpha particles and low gamma energy and it is also considered radiotoxic. Am-241 is produced, in a low level, from nuclear fuel and laboratory wastes. Magnetite nanoparticles (Fe3O4) are iron oxides that possess highly magnetic properties, and its application for removal of water contaminants refers due to its high surface area which allows the adsorption capability and the facility to be prepared and removed from the aqueous medium. In This study, magnetite was synthesized by coprecipitation method largely described. Batch experiments were accomplished at room temperature, at pH 6 and the contacts varying from 2.5, 5, 10, 20, 30, 40, 50, 60 minutes and at 30 minutes for the isotherms experiments. The solid containing magnetite and Am-241 were removed with a magnet and the solution analyzed in a gamma-ray spectrometer (Canberra Model GX2518) which could be quantified. Results show that magnetite possess a capability of removal up to 80% of Am-241 at room temperature, indicating that magnetite nanoparticles are a good sorbent for the removal of radionuclides. Langmuir and Freundlich Isotherms models were investigated and the parameters obtained. Langmuir’s isotherm showed constants of KL (75.7575 L/mg), Q (0.1617 mg/g) and R2 (0.9892) and Freundlich’s isotherm exhibited values of KF (2.6416 [(mg/g).(L/mg)1/n]), 1/n (0.7853 mg/g) and R2 (0.8395), which indicates that the Am- 241 removal from magnetite fits more suitable the Langmuir isotherm model. The thermodynamics parameters, such as the enthalpy and entropy of adsorption, the activation energy, as well as, the kinetics studies are under development.
Studies of equilibrium and kinetics of adsorption of cesium ions by graphene oxide
2017 - OLIVEIRA, FERNANDO M.; BUENO, VANESSA N.; OSHIRO, MAURICIO T.; POTIENS JUNIOR, ADEMAR J.; HIROMOTO, GORO; RODRIGUES, DEBORA F.; SAKATA, SOLANGE K.
Cesium is one of the fission products of major radiological concern, it is often found in nuclear radioactive waste generated at nuclear power plants. Graphene Oxide (GO) has attracted great attention due to its functionalized surface, which includes hydroxyl, epoxy, carbonyl and carboxyl groups, with great capacity of complexation with metal ions and can be used as adsorbent to remove cations from aqueous solutions. In this work, a treatment of radioactive waste containing 137Cs was studied. For the batch experiments of Cs+ removal, 133Cs concentrations remained after the adsorption were determined by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and the results obtained were analyzed according to the Langmuir and Freundlich isotherms models. The kinetics of adsorption and Gibbs free energy were also determined. The Langmuir model was the best fit and defined a favorable adsorption. The cesium adsorption process is the pseudo-second model and the Gibbs free energy calculation indicated that the adsorption process is spontaneous.
Determinação da melhor técnica para digestão de resina proveniente de para-raios contaminados por am-241
2013 - OSHIRO, MAURICIO T.; POTIENS JUNIOR, ADEMAR J.
Determinação da melhor técnica para digestão de resina proveniente de para-raios contaminados por Am-241
2013 - OSHIRO, MAURICIO T.; BUENO, VANESSA N.; SAKATA, SOLANGE K.; POTIENS JUNIOR, ADEMAR J.
Estudo da remoção de césio em soluções aquosas por óxido de grafeno
2013 - BUENO, VANESSA N.; RODRIGUES, DEBORA F.; VITTA, PATRICIA B. DI; OSHIRO, MAURICIO T.; VICENTE, ROBERTO; HIROMOTO, GORO; POTIENS JUNIOR, ADEMAR J.; SAKATA, SOLANGE K.