Modelagem da extração por solventes de urânio em meio sulfúrico com Alamine ®336 na ausência e na presença de íons cloreto

Abstract

In the solvent extraction (SX) plant of uranium, in Caetité/ Bahia, the continuous increase on the level of chlorides in the recirculation streams has promoted a significant decrease on the SX plant efficiency. Alvarenga (2010) has studied the increase of chloride ions level in the recirculated streams and concluded that it affects the efficience of uranium extraction by Alamine®336. The present work is complementary to the experimental one, thus focusing on the modelling of the thermodimanic equilibrium of the uranium SX by Alamine®336 from sulphate media at the absence and at the presence of chloride ions. The concentrations of the aqueous species were calculated using the Specific Ion Interaction Theory (SIT). Data was modelled by fitting test models using calculation tools from Excel®, Statistica® and AQ Solutions® softwares. The following uranium species considered in the aqueous phase: UO2 2+, UO2SO4, UO2(SO4)2 2-, UO2(SO4)3 4-, UO2Cl +and UO2Cl2. The analysis of the aqueous phase indicated that the concentration of species UO2 2+, UO2Cl + and UO2Cl2 are not significant for the studied operating conditions . According to data fitting attemps, it has been verified that the species which is extracted by the Alamine®336 is UO2(SO4)2 2-, whilst the species UO2(SO4)3 4-and UO2SO4 are converted to UO2(SO4)2 2-during extraction. Despite progress obtained in the modelling of the solvent extraction equilibria of uranium with Alamine®336, the interaction between the ions chlorides with the extractant was still not conclusive.