Extraction of platinum group metals from a nitric acid aqueous solution using thiodiglycolamide type extractants with ionic liquids

Osugi, Haruka; Kim, S.-Y.*; Okamura, Hiroyuki   

To extract the platinum group metals, Ru(III), Rh(III) and Pd(II) from the high-level radioactive liquid waste (HLLW), a thiodiglycolamide(TDGA)type extractant, CFBn-TDGA, was synthesized. The extraction properties of platinum group metals from an aqueous nitric acid solution were evaluated using ionic liquids containing the extractant. CFBn-TDGA could extract almost all Pd(II) using [Bmim][NTf] (1-butyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide) and [Bmim][NfO] (1-butyl-3-methylimidazolium nonafluorobutanesulfonate) as ionic liquids. In addition, the extractability of Ru(III) and Rh(III), which are difficult to extract from an aqueous nitric acid solution, increased by using an ionic liquid, [Bmim][NfO], as the solvent. Furthermore, because the extractability of Ru(III) and Rh(III) was improved under the condition at 50C, it also has an advantage in the extraction of platinum group metals from HLLW containing heat-generating nuclides. These results indicate that Ru(III), Rh(III) and Pd(II) contained in HLLW can be collectively extracted by using the TDGA type extractant in combination with [Bmim][NfO].