The separate removal of trace ¹⁴CO₂ and moist NO(x) from off-gases by adsorption on H-type mordenite

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.