Experimental study on the release of Cl2 from NaCl upon OH radical uptake

Abstract

An experimental study using a bead-filled flow tube system coupled to a high-pressure chemical ionization mass spectrometer was performed to characterize the products and kinetic mechanism of the release of chlorine containing species by the heterogeneous reaction of OH radicals on a NaCl surface. Although only species corresponding to HCl were observed, the kinetic model and an experiment with O3 verified that Cl2, the sole product of the heterogeneous reaction, was converted to HCl in the presence of H. The yield of Cl2 per OH was determined to be 0.020±0.002 and 0.022±0.002 at 0 and 6% of relative humidity (RH), respectively. The XPS study indicated that the chlorine deficit caused by OH uptake was enhanced under wet conditions. An enhancement in Cl2 production was observed under wet conditions, which was consistent with the measured chlorine deficit in NaCl. Two reaction mechanisms were proposed to describe the heterogeneous uptake of OH by NaCl.