For improved stewardship of legacy defense waste and treatment of spent nuclear fuel, it is necessary to develop advanced separation systems for actinides and lanthanide-fission products. Current separations of actinides and lanthanides for the nuclear fuel cycle typically utilize liquid-liquid extraction systems, which generate large volumes of hazardous organic waste. To minimize waste production, we are focused on solid-liquid extraction systems. The solid phase extractant (SPE) consists of a mesoporous (2-50 nm pore diameter) silica support that is organically modified by covalently bonding ligands to the surface. The two materials I have focused on are 1) carbamoyl-acetamide (CA) and 2) diglycolamide (DGA) modified mesoporous silica. Characterization of these materials at various stages during synthesis will be presented. Additionally, as a major concern with SPEs for actinide separations is stability in acidic media, results from acid degradation studies will be discussed. The interactions of a number of trivalent species with the CA and DGA materials were studied using batch sorption techniques as well as a variety of spectroscopic methods. While the CA material was found to be an ineffective sorbent for trivalent lanthanides, it did complex lighter trivalent metals such as Al(III) and Sc(III). The DGA material, however, efficiently bound both trivalent lanthanides and actinides from acidic media. Additionally, Am(III) and Eu(III) behaved slightly differently on the DGA material, which is promising for development of a separation system. Results from these studies and others probing the fundamental interactions of these metals with the organically modified mesoporous silica materials will be presented.
