| 摘要 |
<p>Extn. of uranium (VI) from impure phosphoric acid comprises: (a) a first cycle to extract impure acid with an organic phase contg. a dialkylphosphoric acid and trialkylphosphine oxide in inert dilute diluent followed by phase sepn.; treating U-charged organic phase with an aq. soln. of phosphoric acid contg. Fe (II) ions; to extract the uranium (IV) into aq. phase, followed by phase sepn. of the phases; (c) recycling of exhausted organic phase to extract the impure acid and (d) in a second cycle oxidn. of aq. phase; (e) extn. of this oxidised aq. phase with a second extn. medium contg. inert diluent, a dialkylphosphoric acid and opt. synergistic extn. agent, chosen from trialkylphosphine oxides, dibutyl-butyl- phosphonate and trialkylphosphates, followed by phase sepn. to give aq. phase exhausted of uranium and U-charged organic phase, (f) washing the organic phase with water, recovery of the uranium and recycling of organic extractive phase. An improvement is that prior to the washing of the second uranium contg. extractive phase with water in (f), it is treated with aq. sulphuric acid soln, which is free of iron; this solution is obtd. by diluting iron-free concd. sulphuric acid with the aq. soln. obtd. from the water washing-stage (f) to give a 25-60%, pref. about 45% sulphuric acid soln.. After treatment with the sulphuric acid solution uranium is recovered with a Fe/U wt. ratio of less than 0.5%, pref. less than 0.2%.</p> |
