Kinetics and mechanism of the reduction of sodium chlorite by sodium hydrogen ascorbate in aqueous solution at near neutral pH

Abstract

The reduction of chlorite ion by the hydrogen ascorbate ion in a neutral solution safely produces chlorine dioxide. The decrease in absorbance at 268 nm with the presence of dimethyl sulfoxide (DMSO) allows measurement of the ascorbate disappearance in the reaction with excess chlorite. The measured rate constant at 25 ± 0.02°C, 3.67 × 10-4 M DMSO, ionic strength 0.51 M (NaClO4), and in the presence of 3.32 × 10 -9 M ethylenediaminetetraacetic acid is 13.81 ± 1.30 M -1 s-1. Rate constant measurements over the range 15-35°C gave an Arrhenius activation energy of 75.51 ± 4.53 kJ mol-1. This result is the first reported determination of the kinetics of this reaction and is consistent with either electron- or oxygen-transfer mechanisms. Anomalously, reduction of chlorite results in its oxidation, because intermediate hypochlorite oxidizes chlorite. © 2014 Wiley Periodicals, Inc.