ANTONIO ALVES DE FREITAS
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Artigo IPEN-doc 10778 Estudo do tratamento de um residuo de torio e terras raras por cromatografia de extracao2005 - ZINI, J.; ABRAO, A.; CARVALHO, F.M.S.; FREITAS, A.A.; SCAPIN, M.A.Artigo IPEN-doc 08841 Transformacao via peroxido de um hidroxido bruto de torio em nitrato para camisas de lampiao2002 - FREITAS, A.A.; CARVALHO, F.M.S.; FERREIRA, J.C.; ABRAO, A.Artigo IPEN-doc 13274 Recuperacao de chumbo-208 radiogenico de residuo contendo torio e terras raras2008 - FERREIRA, J.C.; FREITAS, A.A. de; SENEDA, J.A.; CARVALHO, F.M.S. de; ABRAO, A.Artigo IPEN-doc 08294 Preparation of highly pure thorium nitrate via thorium sulfate and thorium peroxide2000 - ABRAO, A.; FREITAS, A.A.; CARVALHO, F.M.S.A simple alternative and selective method has been proposed for the preparation of thorium nitrate using as raw material a hydrated crystalline technical grade thorium sulfate. This salt was produced industrially [1] from the alkaline chemical processing of monazite sand in S. Paulo. From a crude thorium hydroxide as the raw material containing uranium and rare earth elements was prepared a technical grade thorium sulfate [Th(SO ) .9H O]. A typical analysis of this salt had shown the following composition: ThO 47–53%, R O (rare 42 2 2 23 earth oxides) 0.5–0.9%, and UO 0.01% and minor amounts of iron, titanium, phosphorus, and silicon oxides. The thorium sulfate is 3 dissolved into water and the thorium peroxide is precipitated from acidic medium by addition of hydrogen peroxide. The thorium peroxide is filtered, washed and finally dissolved with nitric acid. Samples of the thorium peroxide were dried and fired to ThO and aliquot of the 2 thorium nitrate solution was evaporated to dryness and calcined to obtain the ThO . Both ThO have high purity (.99.5%). The content 2 2 of total rare earth elements is very low (0.23% as oxide). Uranium was not detected. The great majority of the RE is precipitated and recovered from the filtrate by oxalic acid.Artigo IPEN-doc 07195 Historico e perspectivas da producao e purificacao de compostos de torio no IPEN2000 - LAINETTI, P.E.O.; ABRAO, A.; FREITAS, A.A.; CARVALHO, F.M.S.; BERGAMASCHI, V.S.; CUNHA, E.F.; AYOUB, J.M.S.; MINDRISZ, A.C.Artigo IPEN-doc 14819 Natural gamma emitters after a selective chemical separation of a TENORM residue: preliminary results2007 - FREITAS, ANTONIO A. de; SANTOS, ADIR J.G. dos; PECEQUILO, BRIGITTE R.S.; ABRAO, ALCIDIOArtigo IPEN-doc 08264 Preparation of highly pure thorium nitrate via thorium sulfate and thorium peroxide2001 - ABRAO, A.; FREITAS, A.A.; CARVALHO, F.M.S.A simple alternative and selective method has been proposed for the preparation of thorium nitrate using as raw material a hydrated crystalline technical grade thorium sulfate. This salt was produced industrially [1] from the alkaline chemical processing of monazite sand in S. Paulo. From a crude thorium hydroxide as the raw material containing uranium and rare earth elements was prepared a technical grade thorium sulfate [Th(SO4)2.9H2O]. A typical analysis of this salt had shown the following composition: ThO2 47-53%, R2O3 (rare earth oxides) 0.5-0.9%, and UO3 0.01% and minor amounts of iron, titanium, phosphorus, and silicon oxides. The thorium sulfate is dissolved into water and the thorium peroxide is precipitated from acidic medium by addition of hydrogen peroxide. The thorium peroxide is filtered, washed and finally dissolved with nitric acid. Samples of the thorium peroxide were dried and fired to ThO2 and aliquot of the thorium nitrate solution was evaporated to dryness and calcined to obtain the ThO2. Both ThO2 have high purity (>99.5%). The content of total rare earth elements is very low (0.23% as oxide). Uranium was not detected. The great majority of the RE is precipitated and recovered from the filtrate by oxalic acid.Artigo IPEN-doc 09434 Transformação via peróxido de um hidróxido bruto de tório em nitrato para camisas de lampião2002 - FREITAS, A.A.; CARVALHO, F.M.S.; FERREIRA, J.C.; ABRAO, A.Apresenta-se neste trabalho um processo alternativo para a recuperação e purificação de tório partindo-se de um hidróxido bruto como precursor, cuja composição média é 60,1% em óxido de tório (ThO2), 18,6% em óxidos de terra raras (TR2O3) e impurezas comuns como silício, ferro, titânio, chumbo, sódio e outros. Este material foi produzido industrialmente da monazita processada no Brasil e estocado há alguns anos. Este hidróxido de tório bruto é tratado com ácido nítrico a quente e, depois da digestão e adição de floculante, é filtrado para a separação da fração insolúvel. Usando-se esta solução de nitrato de tório, precipitou-se o peróxido após o ajuste do pH e a adição controlada de peróxido de hidrogênio. O peróxido de tório assim obtido foi dissolvido com ácido nítrico e o nitrato de tório resultante tem qualidade para ser usado na fabricação de camisas para lampião a gás. Os elementos das terras raras são recuperados totalmente no filtrado do peróxido de tório.