AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Experimental Studies of the Dynamics of Organic Iodide Species Adsorbed on the Surfaces of Environmentally-relevant Particles
ALLA ZELENYUK, Robert VanGundy, Katarzyna Grubel, Thomas Autrey, Youngsoon Shin, Pacific Northwest National Laboratory
Abstract Number: 906 Working Group: Instrumentation and Methods
Abstract Nuclear accidents, like Fukushima, can result in a release of harmful radioactive materials, including semi-volatile organic iodides, into the environment. These species are often adsorbed to different surfaces, such as dust or soot particles, or onto sorbents, designed for their efficient capture. A large number of previous studies have been focused on the efficiency and stability of sorbents to trap different iodide species; however, little is known about the chemical and physical transformations of these species with time and due to exposure to real-world conditions, e.g. relative humidity, light, and oxidants.
We will present the results of a recent study, in which we utilize our approaches for real-time separation and multidimensional characterization of individual particles to quantify the rates of transformation of organic iodide species, adsorbed on to the surfaces of graphitic and activated carbon particles and mesoporous silica.
Segregated particles with well-defined properties (mass, size, shape, morphology, porosity, and composition) were introduced into the adsorption/reaction chamber, where they were exposed to semi-volatile iodide-species, e.g. butyl-iodide (BuI). Single particle mass spectrometer, miniSPLAT, was used to quantify adsorption kinetics of iodide species by measuring, in real-time, changes in particle properties (i.e. composition, mass, and density). In addition, these particles were exposed to water vapor, ozone, OH, and UV light, providing information on the chemical transformation of the adsorbed iodide species.
To compare the evolution of chemisorbed and physisorbed organic iodide species, carbon and silica particles were impregnated with DABCO (1,4-diazabicyclo[2.2.2]octane). The data for BuI physisorbed on bare carbon particles, indicate identical temporal evolution of the iodinium and the butyl fragment ions as a function of the exposure time. In contrast, adsorption of BuI on DABCO-impregnated carbon particles exhibit fast physisorption of BuI and the formation of non-volatile mono-substituted DABCO at a slower rate.
Furthermore, to determine binding energies particles with adsorbed iodide species were introduced into temperature-controlled flow tube reactor, which is used to conduct single-particle desorption studies. These measurements were complemented by the traditional batch measurements utilizing temperature programmed desorption mass spectroscopy.