Extraction of uranium (VI) using N-Alkylcaprolactams from sulfuric acid media

N-alkylcaprolactams as a kind of neutral extractant for actinides were synthesized and used for the solvent extraction of U(VI) from acid media The extraction equilibria showed that U(VI) can be extracted more effectively from sulfuric acid solutions than from nitric acid or hydrochloric acid. The extractabilities of three N-alkylcaprolactams (B) with different alkyl groups were compared to each other and the extracted species from sulfuric acid media was found to be UO2SO4B2. These alkylcaprolactams also extract sulfuric acid into the organic phase in the absence of U(VI), the slope analysis indicating that only one H2SO4 molecule is coordinated to each extractant. The back extraction of U(VI) from the loaded solvent could be easily accomplished by use of dilute NaOH or Na2CO3 as the stripping solution. Furthermore, a study of the extraction kinetics of U(VI) has been carried out in a stirred cell with a plane interface. The rates of the extraction and back extraction for the present system were determined; it was found that the rate controlling reaction is very likely to take place in the interfacial region. (authors)