A s imp1e and efficient procedure has been developed to quantitatively recover Pu from oxalate supernatant using a mixture of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and TBP in dodecane. Pu(IV) in the range of 6.9 to 34.6 mg/1 was quantitatively extracted into 0.2M CMPO + 1.2 M TBP in dodecane from an aqueous solution containing 3.0 M HNO3 and 0.1 M H2C2O4. At such low concentrations of Pu, the distribution ratio (D) did not change but the increase in oxalic acid concentration drastically reduced these values. The variation in HNO3 concentration at a fixed concentration of 0.2 M CMPO + 1.2 N TBP has shown a dramatic increase in the D values, being 0.3 at 1.0 M and >104 at 7.5 M. The extraction was almost quantitative even at the aqueous to organic ratio of 10:1. Plutonium could be quantitatively recovered by (i) stripping with 0.5 M acetic acid and (ii) coprecipitating it directly from the organic phase with 0.3 M oxalic acid + 0.3 M calcium nitrate + sodium nitrite. ∼92% of the Pu was found in the precipitate and ” ∼7% in the supernatant. Using this procedure, Pu in a concentrated form ( ∼50 times), could be recovered from the oxalate supernatant solutions without recourse to the destruction of oxalate Ion. The slope of 2 from the plot of log D ve log [NO3 −] and log [CMPO] respectively suggest the species in the organic phase to be PuC2O4(NO3)2. 2CMPO. The absorption spectral study of Pu(IV) confirmed the above observations.
J. N. Mathur, Murali, M. S., Rizvi, G. H., Iyer, R. H., Michael, K. M., Kapoor, S. C., Dhumwad, R. K., Badheka, L. P., and Banerji, A., “Separation and recovery of plutonium from oxalate supernatant using CMPO”, Solvent Extraction and Ion Exchange, vol. 12, pp. 745–763, 1994.