<b>Mechanism of Dye Decoloration Reaction Using Peroxidase in the Presence of Sodium Percarbonate Bleach Activator</b>

Abstract

The influence of a sodium percarbonate bleach activator in the peroxidase system was studied based on decoloration reaction kinetics of Orange II. When sodium nonanoyl oxybenzene sulphonate(NOBS) coexisted in the ricehull peroxidase(RPO) system, the decoloration rate of Orange II increased. In contrast, the addition of NOBS in the horseradish peroxidase(HRP) system did not increase the decoloration rate. The optimal coexistence conditions of NOBS in the RPO system were Tris/HCl buffer, pH 9.0, 6.7 × 10-4 M of NOBS, and 3.0 × 10-3 M of hydrogen peroxide. No positive effect of the DOBS coexistence in the RPO system was observed. The formed sodium p-phenolsulfonate in the RPO–NOBS coexistence system was further analyzed by HPLC. It is considered that an elimination group (sodium p-phenolsulfonate) formed by a bleach activator resolution reaction activated the RPO reaction and increased the decoloration rate of Orange II. The proposed decoloration mechanism of Orange II is as follows. NOBS disintegrates, and sodium p-phenolsulfonate and organic peroxy acid are formed. Sodium p-phenolsulfonate preferentially reacts with Compound I, forming a sodium p-phenolsulfonate radical. The sodium p-phenolsulfonate radical subsequently undergoes a radical reaction with Orange II. The formed organic peroxy acid causes the decomposition of Orange II radical.