Computer simulation of flow-sheets for the solvent extraction of uranium: a new route to delay the effect of chemical degradation of the organic phase during uranium recovery from acidic sulfate media

BACKGROUND: The extractants used in solvent extraction processes undergo degradation under thermal, chemical and radiolytical stresses. In the case of uranium plants, tri-n-octylamine, used as an extractant, slowly degrades into di-n-octylamine. Such degradation causes a gradual depletion of the uranium extraction isotherms and as a result, of the efficiency of uranium recovery from feed solutions. The present work highlights a new route to delay this depletion of the extraction efficiency, merely by optimizing the flow-sheets involved in the process. Five flow-sheets have been compared for uranium recovery from acidic sulfate media by a solution of 0.146 mol L⁻¹ tri-n-octylamine in kerosene modified with 5% w/w 1-tridecanol and stripping with a 199 g L⁻¹ Na₂CO₃ solution. These five flow-sheets include the classical counter-current flow-sheet with four mixers-settlers in extraction and three mixers-settlers in stripping and four unusual combined solvent extraction flow-sheets with two independent extraction stripping loops and with one or two feed inlets.RESULTS: Computer simulation supplied evidence of the strong influence of the studied flow-sheets on the sturdiness of the process. More precisely, the unusual combined solvent extraction flow-sheets appeared to be significantly more efficient than the classical counter-current one and it is shown that an advantage of this can be to delay the negative impact of gradual degradation of tri-n-octylamine on uranium recovery efficiency from acidic sulfate media.CONCLUSION: The replacement of classical counter-current flow-sheets with a unique extraction-stripping loop in unusual combined flow-sheets with two or more independent extraction-stripping loops and with one or more feed inlets is a fruitful approach to delay the periodic addition of fresh tri-n-octylamine necessary for counter-balancing the progressive degradation of the extraction solvent and, as a result, to delay the gradual depletion of the efficiency of uranium recovery. Copyright