Control effects of pε and pH on the generation and stability of chlorine dioxide

Article type: Research Article

Authors: Pei, Yuan-sheng | Wu, Xiao-qiang | Luan, Zhao-kun | Wang, Tong

Affiliations: Research Center for Eco-Environmental Sciences, the Chinese Academy of Sciences, Beijing 100085, China

Abstract: A new method, without assistance of activity ratio diagram, was applied to construct the pε-pH diagrams for chlorine system. The optimal pH range for generation of ClO_{2} by contacting Cl_{2} (g) directly with ClO_{2}^{−} solution is within pH 1.35–1.94, particularly within pH 1.35–4.00 only if minimizing the formation of Cl_{2}. It is unachievable to synthesize pure ClO_{2} from the reaction of Cl_{2} and ClO_{2}^{−}. Conversely, ClO_{2} may be present a variation of stability in different waters owing to the changed pε and pH. ClO_{2} could be relatively stable if not disproportionate into ClO_{3}^{−}, coexisting with ClO_{2}^{−} (pε 17.63 and pH>9.68), Cl_{2} (pH≤0.92) or Cl^{−} (pH 0.92–9.68). When chlorine system has already reached the ultimate equilibria, ClO_{2} is a stable species in strongly acid media. As the acidity decreases, ClO_{2} disproportionates into ClO_{3}^{−} and Cl_{2}. Aqueous ClO_{2} is unstable within the normal pH range. This work initially, theoretically elucidates the generation and stability of ClO_{2} by way of the pε-pH diagrams.

Keywords: chlorine dioxide, generation, stability, pε-pH diagram

Journal: Journal of Environmental Sciences, vol. 15, no. 5, pp. 680-684, 2003