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

¹ Laboratoire d'Électronique des Gaz et des Plasmas, Université de Pau et des Pays de l'Adour, BP 1155, 64013 Pau Cedex, France
² Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, Université de Pau et des Pays de l'Adour, BP 1155, 64013 Pau Cedex, France

Corresponding author: jean-francis.loiseau@univ-pau.fr

Received: 9 December 2003
Revised: 2 July 2004
Accepted: 4 August 2004
Published online: 21 December 2004

Abstract

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.