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 O3 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.