Extraction and separation of thorium(IV) and uranium(VI) with 4-oxaheptanediamide into ionic liquid system from aqueous solution

Thorium is much more abundant than uranium in nature and has become one of the important potential energy sources in the future. It is because that a thorium-232(232Th) nucleus has the ability to produce a uranium-233(233U) nucleus by absorbing a neutron. The aim of this paper is to investigate the extraction and separation of thorium ions and uranyl ions from aqueous solution with N,N’-dimethyl-N,N’-dioctyl-4-oxaheptanediamide (DMDOHA) into ionic liquids of 1-methyl-3-butylimid-azolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]). The results show that the extractant DMDOHA has a good affinity toward thorium ions than uranyl ions in the present system, the maximum value of separation factor SFTh(IV)/U(VI) is 21.9 at pH 2.24. The extraction process of thorium ions and uranyl ions was confirmed to proceed by cation-exchange extraction mechanism. The DMDOHA extractant formed a major 3:1 complex with thorium ion and a major 2:1 complex with uranyl ion based on the relationship between log[DMDOHA] with logD.