CARLOS ALBERTO DA SILVA QUEIROZ
10 resultados
Resultados de Busca
Agora exibindo 1 - 10 de 10
Artigo IPEN-doc 14211 Quantification of trace amounts of rare earth elements in high purity gadolinium oxide by sector field inductively coupled plasma mass spectrometry (ICP-MS)2004 - PEDREIRA, W.R.; QUEIROZ, C.A. da S.; ABRAO, A.; PIMENTEL, M.M.Artigo IPEN-doc 11702 Trace amounts of rare earth elements in high purity samarium oxide by sector field inductively coupled plasma mass spectrometry after separation by HPLC2006 - PEDREIRA, W.R.; QUEIROZ, C.A.; ABRAO, ALCIDIO; ROCHA, SORAYA M.; VASCONCELLOS, MARI E. de; BOAVENTURA, G.R.; PIMENTEL, M.M.Artigo IPEN-doc 08265 Determination of trace amounts of rare earth elements in highly pure praseodymium oxide by double focusing inductively coupled plasma mass spectrometry and high-performance liquid chromatography2001 - PEDREIRA FILHO, W.R.; SARKIS, J.E.S.; RODRIGUES, C.; TOMIYOSHI, I.A.; QUEIROZ, C.A.S.; ABRAO, A.Artigo IPEN-doc 08604 Determination of trace amounts of rare earth elements in high pure lanthanum oxide by sector field inductively coupled plasma mass spectrometry (HR ICP-MS) and high-performance liquid chromatography (HPLC) techniques2002 - PEDREIRA FILHO, W.R.; SARKIS, J.E.S.; RODRIGUES, C.; TOMIYOSHI, I.A.; QUEIROZ, C.A.S.; ABRAO, A.Artigo IPEN-doc 08606 Thermoanalytical characterization of neodymium peroxicarbonate2002 - QUEIROZ, C.A.S.; MATOS, J.R.; VASCONCELLOS, M.E.; ABRAO, A.Artigo IPEN-doc 08626 Synthesis and characterization of lanthanum acetate for application as a catalyst2002 - ROCHA, S.M.R.; QUEIROZ, C.A.S.; ABRAO, A.Artigo IPEN-doc 10222 Sequential separation of the yttrium-heavy rare earths by fractional2004 - VASCONCELLOS, M.E.; QUEIROZ, C.A.S.; ABRAO, A.Artigo IPEN-doc 10226 Synthesis and thermoanalytical characterization of samarium peroxocarbonate2004 - QUEIROZ, C.A.S.; VASCONCELLOS, M.E.; ROCHA, S.M.R.; SENEDA, J.A.; PEDREIRA, W.R.; MATOS, J.R.; ABRAO, A.Artigo IPEN-doc 11701 Enrichment of yttrium from rare earth concentrate by ammonium carbonate leaching and peroxide precipitation2006 - VASCONCELLOS, MARI E. de; ROCHA, SORAYA M.R. da; PEDREIRA FILHO, WALTER dos R.; QUEIROZ, CARLOS A. da S.; ABRAO, ALCIDIOThe rare earth elements (REE) solubility with ammonium carbonate vary progressively from element to element, the heavy rare earth elements (HRE) being more soluble than the light rare earth elements (LRE). Their solubility is function of the carbonate concentration and the kind of carbonate as sodium, potassium and ammonium. In this work, it is explored this ability of the carbonate for the dissolution of the REE and an easy separation of yttrium was achieved using the precipitation of the peroxide from complex yttrium carbonate. For this work is used a REE concentrate containing (%) Y2O3 2.4, Dy2O3 0.6, Gd2O3 2.7, CeO2 2.5, Nd2O3 33.2, La2O3 40.3, Sm2O3 4.1 and Pr6O11 7.5. The mentioned concentrate was produced industrially from the chemical treatment of monazite sand by NUCLEMON in Sao Paulo. The yttrium concentrate was ˜ treated with 200 g L−1 ammonium carbonate during 10 and 30 min at room temperature. The experiments indicated that a single leaching operation was sufficient to get a rich yttrium solution with about 60.3% Y2O3. In a second step, this yttrium solution was treated with an excess of hydrogen peroxide (130 volumes), cerium, praseodymium and neodymium peroxides being completely precipitated and separated from yttrium. Yttrium was recovered from the carbonate solution as the oxalate and finally as oxide. The final product is an 81% Y2O3. This separation envisages an industrial application. The work discussed the solubility of the REE using ammonium carbonate and the subsequent precipitation of the correspondent peroxides.Artigo IPEN-doc 12977 Solubility behavior of rare earths with ammonium carbonate and ammonium carbonate plus ammonium hydroxide: precipitation of their peroxicarbonates2008 - VASCONCELLOS, MARI E. de; ROCHA, S.M.R.; PEDREIRA, W.R.; QUEIROZ, CARLOS A. da S.; ABRAO, ALCIDIOThe purpose of this work is to report the significant behavior of the rare earths when treated with ammonium carbonate and with a binary mixture of ammonium carbonate plus ammonium hydroxide. The carbonates of some rare earths are completely soluble in ammonium carbonate or in ammonium carbonate plus ammonium hydroxide, while others are only partially soluble and finally some are completely insoluble. Addition of hydrogen peroxide to the soluble complexed rare earth carbonates results in the precipitation of a series of a new compounds described as rare earth peroxicarbonates. The rare earths have some different precipitation behavior in the carbonate–peroxide system. Some are completely and immediately precipitated, others are completely precipitated after an aging period, and finally other are not precipitated at all. These different behaviors open a new possibility for the separation chemistry of the rare earths. Sm, Gd, Dy, Y, Yb and Tm are fast and completely soluble in ammonium carbonate. Ho, Eu and Tb are completely soluble in ammonium carbonate but slowly dissolved. La, Ce, Pr and Nd are only partially soluble in ammonium carbonate. While Ce, Pr, Nd, Sm, Eu and Dy are completely and easily soluble in the ammonium carbonate plus ammonium hydroxide mixture, La is only partially soluble and Tb is completely insoluble in the same mixture. Concerning the peroxicarbonates, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy and Ho are quantitatively precipitated. The precipitation of the Er peroxicarbonate is quantitative, but after an aging period of 24 h. Y is not precipitated at all. The process is very easy, simple and economically attractive. Although proved in bench scale, its scale-up is easily feasible.