CARLOS ALBERTO DA SILVA QUEIROZ
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Resumo IPEN-doc 31008 Lanthanum2024 - QUEIROZ, CARLOS A. da S.The following studies are presented: Preparation of lanthanum oxide for use as spec pure standard and synthesis and characterization of lanthanum peroxide. Using the fraction precipitation and cationic ion exchange techniques, with EDTA as eluent, it was possible to obtain pure lanthanum oxide ≥ 99.9%, whose Impurities were in the same level as in the imported standard. The yield for the combined techniques was reasonable high (≥ 80%). The raw material in the form of mixed rare earth carbonate (La2O3 45%) comes from by commercial rare earth concentrate. Emphasis was given to the analytical control to assure the purity of La2O2≥99.9% by spectrophotometry and mass spectrometry. A study was made for the optimization of dissolution lanthanum carbonate, from the lanthanum spec pure standard obtained here, as function of the concentration of ammonium carbonate and ammonium carbonate\ammonium hydroxide searching the maximum solubilization of the lanthanum carbonate. The lanthanum peroxide was prepared by the addition of hydrogen peroxide to the complexed soluble lanthanum carbonate. These studies included also the determination of active oxygen, the total lanthanum oxide by gravimetry and complexometry and the C, H, O contents by microanalysis. The peroxide was also investigated by infrared spectroscopy and thermal analysis. The analytical data collected allowed to conclude that the stoichiometric formula for the peroxide is La2O2(CO3)2 1.25H2O.Resumo IPEN-doc 30154 Preparation of lanthanum acetate from a mixed rare earths concentrate2023 - QUEIROZ, CARLOS A. da S.A simple and economical chemical process to obtaining lanthanum acetate of high purity was studied. The raw material in the form of mixed rare earths carbonate 24% La2O3 comes from commercial Brazilian monazite. It is used the technique of strong cationic exchange resin, proper to water treatment to the lanthanum''s fractionation and it is achieved a purity of 99.9% La2O3 and yield greater than or equal 90%, with the elution of rare earths by EDTA solution at pH 4.0. The complex of EDTA-La is transformed in La2O3 , subsequently the lanthanum oxide is dissolved in acetic acid to obtain the cerium acetate. The solid salt then is characterized via chemical analysis, thermal analysis, X ray diffraction, infrared spectroscopy and mass spectrometry to certify the lanthanum acetate purity. The analytical data collected allowed to conclude that the stechiometric formula for the compound is La (CH3COO)3.1.5 H2O.Artigo IPEN-doc 27845 Production of high purity samarium acetate for use in nuclear area2021 - QUEIROZ, CARLOS A. da S.; PEDREIRA FILHO, WALTER dos R.Samarium is currently used in many applications, such as catalysts, lasers and metal alloys. Samarium is also employed to absorb neutrons in nuclear reactors. In medicine, samarium is used in the form of radioactive 153Sm to produce radiopharmaceuticals. A simple process for the preparation of pure samarium acetate was studied. The raw material, which was used in the form of rare earth carbonates was produced industrially from the chemical treatment of Brazilian monazite. Ion exchange chromatography was performed using a strong cationic resin to fractionate rare earth elements (REE). Under these conditions, 99.9% pure Sm2O3 and yield greater than or equal 60% was eluted by ammonium salt of ethylenediaminetetraacetic acid (EDTA) solution in con-trolled pH. The EDTA-samarium complex was transformed into samarium oxide, which was subsequently dis-solved in acetic acid to obtain the samarium acetate. Molecular absorption spectrophotometry was used to moni-tor the samarium and sector field inductively coupled plasma mass spectrometry was used to certify the purity of the samarium acetate. The solid salt was characterized by chemical analysis, thermal analysis, infrared spectros-copy and X ray diffraction. The analytical data collected allowed to conclude that stoichiometric formula for the samarium acetate obtained is Sm(CH3COO)3.4.H2O.