Journal
JOURNAL OF HAZARDOUS MATERIALS
Volume 398, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.jhazmat.2020.122853
Keywords
Nuclear waste; Radiolysis; Sum frequency generation; Gibbsite; Boehmite
Categories
Funding
- IDREAM (Interfacial Dynamics in Radioactive Environments and Materials), an Energy Frontier Research Center - U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES)
- Nuclear Process Initiative Laboratory Directed Research and Development at Pacific Northwest National Laboratory
- U.S. Department of Energy's Office of Biological and Environmental Research
- U.S. DOE [DE-AC05-76RLO 1830]
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Understanding mechanistic pathways to radiolytic hydrogen generation by metal oxyhydroxide nanomaterials is challenging because of the difficulties of distinguishing key locations of OH bond scission, from structural interiors to hydroxylated surfaces to physi-sorbed water molecules. Here we exploited the interface-selectivity of vibrational sum frequency generation (VSFG) to isolate surface versus bulk hydroxyl groups for gibbsite and boehmite nanoplatelets before and after Co-60 irradiation at dose levels of approximately 7.0 and 29.6 Mrad. While high-resolution microscopy revealed no effect on particle bulk and surface structures, VSFG results clearly indicated up to 83% and 94% radiation-induced surface OH bond scission for gibbsite and boehmite, respectively, a substantially higher proportion than observed for interior OH groups by IR and Raman spectroscopy. Electron paramagnetic spectroscopy revealed that the major radiolysis products bound in the mineral structures are trapped electrons, O-center dot, O-2(-center dot) and possibly F-centers in gibbsite, and H-center dot, O-center dot and O-3(-center dot) in boehmite, which persist on the time frame of several months. The entrapped radiolysis products appear to be highly stable, enduring re-hydration of particle surfaces, and likely reflect a permanent adjustment in the thermodynamic stabilities of these nanomaterials.
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