Extraction of uranium(VI) from nitric acid solution using pyrrolidone derivatives

The extraction behavior of uranyl species from HNO3 aqueous solutions using CH2Cl2 containing pyrrolidone derivatives as extractants has been studied to find an alternative to tributyl phosphate as an extractant. In this study, we used N-cyclohexyl-2-pyrrolidone (NCP), N-octyl-2-pyrrolidone (NOP), and N-dodecyl-2-pyrrolidone (NDP) as the extractants. As a result, it was found that NCP, NOP, and NDP (abbreviated as NRP) extract U(VI) as UO2(NO3)2(NRP)2, that a part of NCP in CH2Cl2 phase is moved to the aqueous phase, and that the extractability (corresponding distribution ratio) of U(VI) increases with increasing [HNO3]int from 7% (0.08) ([HNO3]int=0.1M, [NRP]int=1.0M) to more than 90% (11) ([HNO3]int=3.0M, [NRP]int=1.0M). From these results, it is expected that NOP and NDP extract U(VI) effectively from HNO3 solution of more than 3M and that the extracted U(VI) species are stripped by using HNO3 aqueous solution of low concentration. (author)