Abstract
Study was made to clarify the decoloration mechanism of Orange II in the presence of horseradish peroxidase (HRP)-hydrogen peroxide (H2O2) in organic solvents/water systems. The decoloration rate constant of Orange II decreased in the presence of organic solvents. The highest decoloration rate constant was noted for the methanol/water system. The decoloration reaction of Orange II was found to proceed even at high concentrations of methanol, while this was not the case for alcohols solvents. Reaction of the HRP system was examined by following the changes in HRP oxidation states using the methanol, ethanol and 2-propanol/water systems. An intermediate - Compound III - was formed in the HRP oxidation cycle of ethanol/water and 2-propanol/water systems but did not in the methanol/water system. HRP oxidation states and reaction cycle are importantly involved in the decoloration mechanism of Orange II.
