Selective Separation of Americium from Lanthanides using Molecular Recognition Technology

The problem to be addressed is the need for an efficient, simplified, and economic green chemistry process to separate and concentrate americium (Am) from lanthanide (Ln) fission products. Achievement of Phase I objectives using a metal-selective Molecular Recognition Technology (MRT) process would answer this need on a laboratory scale and lead through process scale-up to an industrial operation in Phase II and beyond that would be a significant step toward fully closing the nuclear fuel cycle, a result of great value to the Department of Energy (DOE). Waste mass and volume reduction by radionuclide concentration in the MRT process would reduce space required for permanent storage and enable environmental and legislative requirements to be met. High neutron cross sections of Ln(III) mandate their separation from Am(III) and curium(III) (Cm separation will not be studied in Phase I). Phase I objectives are prepare a novel ligand equipped with a tether that is similar to one without a tether prepared at Oak Ridge National Laboratory (ORNL) and shown by ORNL workers to have high selectivity for Am(III) over Ln(III) in solutions with nitric acid (HNO3) concentrations up to 3 M, attach the novel ligand to a silica gel solid support by the tether to form a new supported product for use in the MRT process, and test this supported product for its size selectivity among Ln(III) and Am(III) in 1-5 M HNO3 resulting in determination of separation factors (SF) for Am(III) over Ln(III). Experiments involving Am(III) will be performed at ORNL because of the nuclear capabilities located there. MRT processes are simple in design, are safe and reliable in operation, use no organic solvents or highly corrosive chemicals, generate minimal secondary waste, and occupy small floor space. Marked simplification of the separation process and greatly reduced capital and operating expenses result. Phase I success will lead in Phase II and beyond to scale-up of the MRT process enabling commercial separation of Am(III) and Cm(III) from Ln(III) followed by concentration and recovery of these radionuclides for subsequent storage and disposal. Applications and public benefits resulting from a successful Phase II effort would include a simplified and reliable green chemistry MRT process for effective separation, concentration, storage, and disposal of radiotoxic metals; greater ability to meet public and governmental requirements for disposal of primary radiotoxic waste; improvement of public perceptions of dangers of nuclear waste disposal by demonstrating minimal secondary waste generation; decreased need for extensive and expensive waste clean-up operations that attract negative public attention through demonstrated separation of target metals at mg L-1 and lower concentrations; and support of the purposes of non-proliferation. A major benefit to DOE is the opening of a door to a sustainable, simplified nuclear fuel cycle of the future. Benefits to local economies include jobs related to production of SuperLig® products and to building the immense infrastructure involved in nuclear facilities required for processing used nuclear fuel.