NUMERICAL MODELING FOR COEXTRACTION OF TC(VII) WITH U(VI) BY N-OCTYL(PHENYL)-N, N-DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE FROM NITRIC-ACIDSOLUTION

The coextraction model of Tc(VII) and U(VI) from nitric acid solution was developed on a tributyl phosphate (TBP)/n-dodecane system involvin g tyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO). Tec hnetium was considered to be extracted by the formation of Tc-CMPO and U-Tc-CMPO complexes in the presence of uranium. The distribution coef ficient of technetium in the presence of uranium was defined by taking these complexes into account, and expressed as a function of nitric a cid concentration, free CMPO concentration, and distribution coefficie nt of uranium. The equation of the distribution coefficient derived wa s applied to the previous data obtained in the mixed system of CMPO-TB P-dodecane at the low nitric acid concentration. It was found that the distribution behavior of technetium in the presence of uranium could be successfully simulated by the present coextraction model.