Three kinds of mordenite were examined for the adsorptive separation and removal of trace amounts of 14CO2 and moist NO(x) contained in the off-gases of reprocessing plants for spent nuclear fuels. It was found that protonation of mordenite eliminated any possible removal of CO2 by specific adsorption but induced the dissociative adsorption of NO2 with the formation of nitric acid-like adsorbed species and NO oxidation. FT-IR spectroscopic results confirmed that the Bronsted acid sites existing on H-type mordenites exhibit no interaction with CO2 molecules but can catalyze the dissociative adsorption of NO2. Such properties, together with the lower adsorption temperature and the thermal stability of the adsorbent, suggest a promising process involving H-type mordenites whereby NO(x) can be selectively captured and returned to the dissolving solution while trace amounts of 14CO2-containing carbon oxides pass through the system allowing their subsequent complete removal by entrapment in a solid matrix.
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