Oxidation of Formaldehyde by Chlorite in Basic and Slightly Acidic Media

Abstract

The reaction of chlorite and formaldehyde was studied in basic and slightly acidic media . Though the expected product was CO 2, the oxidation of HCHO, however, gave nearly quantitative formation of ClO 2, the oxidation product of ClO 2 - . In excess HCHO the stoichiometry of the reaction was deduced as 3ClO 2 - + HCHO + 2H + → HCOOH + 2ClO 2 (aq) + Cl - + 2H 2 O; but in high excess of ClO 2 - the stoichiometry was 6ClO 2 - + HCHO + 4H + → CO 2 (g) + 4ClO 2 (aq) + 3H 2 O + 2Cl - . The reaction is autocatalytic in HOCl. The first step of the reaction produces HOCl, which catalyzes the formation of ClO 2 and further oxidation of HCOOH to CO 2 . ClO 2 was found to be relatively unreactive toward HCHO and HCOOH, and hence it accumulated rapidly.