Actinide and Lanthanide Interactions with Aluminum (Hydr)oxide Minerals: Equilibrium and Kinetics Analysis of Sorption and Desorption Processes

Nuclear energy does not generate greenhouse gas emissions during power production, but the high-level nuclear waste generated in the commercial nuclear fuel cycle remains a barrier to increased nuclear power use in the United States. This waste will eventually be disposed of in deep geologic repositories, yet the development of a nuclear repository is hindered by knowledge gaps related to how radionuclides behave and migrate in the environment.To fill these knowledge gaps, the work presented in this dissertation focuses on understanding how actinides and lanthanides interact with different aluminum (hydr)oxide minerals and how the different surface acidities of these minerals effect macroscopic sorption trends. Europium and neptunium interactions to gibbsite, bayerite, corundum, and γ-alumina were investigated through a series of batch sorption experiments at varying mineral and metal ion concentration, pH, and time. Minerals were characterized to monitor for phase transformations and aqueous metal ion concentrations were measured using inductively-coupled plasma mass spectrometry. Kinetics analyses and equilibrium descriptions of the sorption and desorption processes of these systems are discussed in detail. Preliminary data focusing on the surface-mediated reduction of plutonium in the presence of bayerite and gibbsite are also presented.