Selective electrochemical capture and release of uranyl from aqueous alkali, lanthanide, and actinide mixtures using redox-switchable carboranes.

We report the selective electrochemical biphasic capture of the uranyl cation (UO 2 2+ ) from mixed-metal alkali (Cs + ), lanthanide (Nd 3+ , Sm 3+ ), and actinide (Th 4+ , UO 2 2+ ) aqueous solutions to an organic, 1,2-dichloroethane (DCE), phase using the ortho -substituted nido -carborane anion, [1,2-(Ph 2 PO) 2 -1,2-C 2 B 10 H 10 ] 2- ( PO Cb 2- ). The reduced PO Cb 2- is generated by electrochemical reduction of the closo -carborane, PO Cb, prior to mixing with the aqueous mixed-metal solution. Subsequent UO 2 2+ release from the captured product, [UO 2 ( PO Cb) 2 ] 2- , was performed by galvanostatic bulk electrolysis of the DCE phase and back-extraction of UO 2 2+ to a fresh aqueous phase. The selective capture and release of UO 2 2+ was confirmed by combined ICP-OES and NMR spectral analyses of the aqueous and organic phases, respectively, against the newly synthesized nido -carborane complexes, [[CoCp* 2 ][Cs( PO Cb)]] 2 , [CoCp* 2 ] 3 [Nd( PO Cb) 3 ], [CoCp* 2 ] 3 [Sm( PO Cb) 3 ], and [CoCp* 2 ] 2 [Th( PO Cb) 3 ].