Sodium hydroxide-sodium sulphate stripping of uranium from amine extracts



Batch shake-out tests on two tertiary amines and one secondary amine to determine the effects of sodium sulphate concentration and pH on the distribution of uranium between 0.1N amine in kerosene and aqueous sodium sulphate solution showed that transfer of uranium from the solvent to the aqueous phase was favored by increasing pH values up to 5.5 and by increasing the aqueous sodium sulphate concentration up to 20% w/v Na2SO4.

Continuous counter-current stripping of tri-isooctylamine (TIOA) extracts with 20% w/v Na2SO4 was also carried out in a three-stage mixer-settler arrangement in which the pH was controlled by the addition of 10% NaOH to the three stages. Further addition of caustic to the separated aqueous strip solution to raise the pH to 7.0–7.2 yielded a high grade uranium precipitate (88% U3O8). The continuous testing confirmed the results of the shake-out tests and showed that the procedure gave results comparing favorably with other stripping methods accompanied by a lower overall reagent cost.