Studies of Radio-Labelled Free Radicals Derived from a VOC (Volatile Organic Compound), Benzaldehyde, Adsorbed in Cation-Exchanged Zeolite X

Abstract

Radio-labelled free radicals were formed by the addition of muonium-a radioactive hydrogen atom with a positive muon as its nucleus-to benzaldehyde, as adsorbed in cation-exchanged zeolite X. PhCHOMu• radicals were the major species formed and the activation parameters associated with their reorientational motion were measured using longitudinal-field muon spin relaxation (LF-MuSRx). Two distinct adsorbed fractions were detected in each of the samples containing Li+, Na+, K+, Ca2+, Sr2+ and Ba2+ cations, believed to be from (1) an effectively bulk benzaldehyde component with an almost common activation energy for molecular reorientation of ca 3kJ/mol, and (2) benzaldehyde adsorbed inside the zeolite supercages. MgX showed only the supercage fraction clearly.