PRECIPITAÇÃO DO SULFATO DUPLO DE TERRAS RARAS E SÓDIO A PARTIR DE UM LICOR SULFÚRICO DE TERRAS RARAS CONTENDO IMPUREZAS
PRECIPITATION OF RARE EARTH-SODIUM DOUBLE SULFATE FROM A RARE EARTH SULFURIC LIQUOR CONTANING IMPURITIES
Ruberlan Gomes da Silva, Carlos Antonio de Morais, Leandro Viana Teixeira, Éder Domingos de Oliveira
Resumo
O licor sulfúrico de terras raras usado nesse estudo continha 4,54 g.L -1 de óxidos de terras raras (OTR), baixa acidez (<1,0 g H 2 SO 4 .L -1 ) e apresentava em sua composição as impurezas Ca 2+ , Mg 2+ , Mn 2+ , Fe 3+ , Al 3+ , Th 4+ , UO 22+ e PO 43-. Parte desse licor foi purificado com calcário até pH=3,5 e depois com cal hidratada até pH=5,0, sendo obtido um licor de terras raras purificado isento das impurezas Fe 3+ , Th 4+ e PO 43- e com menores concentrações de Al 3+ , UO 22+ e SO 42- . Os ensaios de precipitação das terras raras com sulfato de sódio (Na 2 SO 4 ) mostraram que a qualidade química do sulfato duplo de terras raras e sódio (NaETR(SO 4 ) 2 .xH 2 O) obtido com o licor purificado apresentou teor de OTR de 38%, enquanto que o teor de OTR no sulfato duplo obtido com licor não purificado foi de apenas 31%. A principal impureza foi o cálcio (~3%). A eficiência de precipitação das terras raras foi de 80% e o consumo de Na 2 SO 4 foi de 1,3 toneladas para cada tonelada de OTR contido no licor alimentado. As precipitações foram realizadas a 70°C. A precipitação foi seletiva para as terras raras dos grupos específicos, tendo precipitado 82% do La, Ce, Nd e Pr, 53% do Sm, Eu e Gd e apenas 16% do Tb, Dy, Ho, Er, Tm, Yb, Lu, Y e Sc. Baseado nos resultados foi proposto uma rota de processo onde 80% das terras raras seriam precipitadas na forma de NaETR(SO 4 ) 2 .xH 2 O e os 20% restantes como óxidos (>97% de OTR) ou carbonatos (>68% de OTR) mistos de terras raras.
Palavras-chave
Abstract
The non purified rare earth sulfate liquor used in these study contained 4.54 g.L -1 of rare earth oxides (REO), low acidity (<1.0 g H 2 SO 4 .L -1 ) and presented in its composition the following impurities Ca 2+ , Mg 2+ , Mn 2+ , Fe 3+ , Al 3+ , Th 4+ , UO 22+ e PO 43-. Part of this liquor was purified with limestone until pH=3.5 and after with lime until pH=5.0, and it was obtained a purified rare earth sulfate liquor free of Fe 3+ , Th 4+ and PO 4-3 and with a low concentration of Al 3+ , UO 22+ and SO 42- . The rare earth precipitation experiments using sodium sulphate (Na 2 SO 4 ) indicated that the best chemical quality was obtained in rare earth-sodium double sulfates (NaETR(SO 4 ) 2 .xH 2 O) produced from the purified liquor, presenting a REO content of 38% w/w, while the rare earth-sodium double sulfates from the non purified liquor contained a REO content of only 31% w/w. The main impurity was calcium (~3% w/w Ca). The REO recovery was 80% and the consumption of Na 2 SO 4 was 1.3 ton per ton of REO in the feed liquor. The rare earth precipitation was carried out at 70°C. There was selective precipitation in specific groups of rare earth, being precipitated 82% of La, Ce, Nd and Pr, 53% of Sm, Eu and Gd and only 16% of Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and Sc. Based on this results, it was proposed a process route where 80% of REO would be precipitated as NaREE(SO 4 ) 2 .xH 2 O and the 20% remaining as rare earth oxides (>97% of REO) or as rare earth carbonates (>68% of REO).
Keywords
References
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