This
study evaluated zeolite-based sorbents for iodine gas [I2(g)] capture. Based on the framework structures and porosities,
five zeolites, including two faujasite (FAU), one ZSM-5 (MFI), one
mesoMFI, one ZSM-22 (TON), as well as two mesoporous materials, were
evaluated for I2(g) capture at room temperature and 150
°C in an iodine-saturated environment. From these preliminary
studies, the three best-performing zeolites were ion-exchanged with
Ag+ and evaluated for I2(g) capture under similar
conditions. Energy-dispersive X-ray spectroscopy data suggest that
Ag-FAU frameworks were the materials with the highest capacity for
I2(g) in this study, showing ∼3× higher adsorption
compared to Ag-mordenite (Ag-MOR) at room temperature, but X-ray diffraction
measurements show that the faujasite structure collapsed during the
adsorption studies because of dealumination. The Ag-MFI zeolites are
decent sorbents in real-life applications, showing both good sorption
capacities and higher stability. In-depth analyses and characterizations,
including synchrotron X-ray absorption spectroscopy, revealed the
influence of structural and chemical properties of zeolites on the
performance for iodine adsorption from the gas phase.
Non-ideal thermodynamics of solid solutions can greatly impact materials degradation behavior. We have investigated an actinide silicate solid solution system (USiO4–ThSiO4), demonstrating that thermodynamic non-ideality follows a distinctive, atomic-scale disordering process, which is usually considered as a random distribution. Neutron total scattering implemented by pair distribution function analysis confirmed a random distribution model for U and Th in first three coordination shells; however, a machine-learning algorithm suggested heterogeneous U and Th clusters at nanoscale (~2 nm). The local disorder and nanosized heterogeneous is an example of the non-ideality of mixing that has an electronic origin. Partial covalency from the U/Th 5f–O 2p hybridization promotes electron transfer during mixing and leads to local polyhedral distortions. The electronic origin accounts for the strong non-ideality in thermodynamic parameters that extends the stability field of the actinide silicates in nature and under typical nuclear waste repository conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.