Application of extraction chromatography to the separation of thorium and uranium dissolved in a solution of high salt concentration

Extraction chromatography with commercially available UTEVA resin (for uranium and tetravalent actinide) was applied for the separation of Th and U from control solutions prepared from a multi-element control solution and from sample solutions of solidified simulated waste. Thorium and U in control solutions with 1–5 mol/dm3 HNO3 were extracted with UTEVA resin and recovered with a solution containing 0.1 mol/dm3 HNO3 and 0.05 mol/dm3 oxalic acid to be separated from the other metallic elements. Extraction behavior of U in the sample solutions was similar to that in the control solutions, but extraction of Th was dependent on the concentration of HNO3. Thorium was extracted from 5 mol/dm3 HNO3 sample solutions but not from 1 mol/dm3 HNO3 sample solutions. We conjecture that thorium fluoride formation interferes with extraction of Th. Addition of Al(NO3)3 and Fe(NO3)3, which have higher stability constant with fluoride ion than Th, does improve extractability of Th from 1 mol/dm3 HNO3 sample solution.