Physico-chemical study of a corona discharge in gas mixtures containing humid air, carbon dioxide and nitrogen oxides

摘要

Gas mixtures containing humid air, various proportions of CO2 and traces of NO2 are submitted to a short gap point-to-plane DC corona discharge in a reactor at atmospheric pressure. These mixtures can be considered as the basic component of most industrial effluents. Coming after an electrical study previously published, this work is centered on the physico-chemical effects of the discharge. Concentric circular alterations appearing on a copper cathode have been analyzed by XPS, showing an oxidation and acidification spread over a great part of the surface by the electric wind. The NO2 removal and corresponding by-products have been studied by UV absorption spectroscopy on gas samples after treatment, in the 200 - 400 nm wavelength range where NO2 abatement and O-3 concentrations can be evaluated. Being partly produced in liquid phase, HNO3 which is responsible of the acidification of cathode surface, can be studied only qualitatively. A few chemical mechanisms are propounded for both bulk and surface actions of the discharge.