Uranium is recovered from leach liquors as anionic complex, the two most frequently encountered being the sulfate (from acid leach liquors) and the carbonate (from alkaline leach liquors) complexes :
Specially conceived strong base anion exchangers are used to fix these anionic complexes in presence of high concentrations of other anions such as sulfates, carbonates or ferric sultates. Both fixed bed or continuous systems are used for both loading and elution steps. The resin characteristics for the various systems may vary, for example in particle size, depending on the specific operating conditions employed. The operating capacity depends on the feed solution composition.
Elution of the uranium from the resin is practiced today using three main systems :
- acidified nitrate solutions
- chloride solutions
- sulfuric acid
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In the case of carbonate leaching, only NH4NO3 or NaCl can be used as eluants. Acid elution can not be used because the acid will react with the carbonates to form CO2. The quantity of eluant in a fixed system is of the order of 5 BV for nitrate or 10 BV for sulfuric acid or 15 BV for NaCl solutions. With continuous elution systems this quantity of eluants can be reduced.
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