Kinetics of Nitric Acid Uptake by Salt

Abstract

The kinetics of the uptake of HN03 on a series of salt powders (NaC1, NaBr, KC1, and KBr) has been studied in a Teflon-coated, low-pressure flow reactor. HC1 and HBr are found to be the sole products of the reactions, and, within experimental uncertainty, all the HN03 taken up by the salt is converted to HCl or HBr. Values for the uptake coefficients are derived from two experimental procedures: (1) Steady-state uptake of constant HN03 flows and (2) real-time monitoring of pulsed quantities of HN03. The two procedures yield values in good agreement, and it has been determined that all the salts studied, including the nonreactive NaN03, are characterized by the same value of the uptake coefficient: y = (2.8 f 0.3) x A discussion is given for the non-negligible affinity of HN03 for the Teflon-coated walls and how this effect is taken into account in our experiments. We develop a model of the uptake kinetics, based on our experimental results, that reproduces the observations over a broad range of experimental conditions. In addition, the uptake of HCl (Y = 3 x on NaCl powder is determined in ancillary experiments. The results may hold implications for the understanding of chloride displacement in marine aerosols. and H20 ( y < 2 x