We have investigated the initial rate of decoloration of some natural colorants by sodium percarbonate in solution and the influence of pH and temperature on the decoloration reaction. The natural colorants were flavonol, chrysin, carthamin, car minic acid, and shikonin. Orange II (CI acid orange 7), a typical synthetic azo dye, was used for comparison. The maximum rate constant was in the neighborhood of pH 11.5 for all cases, and increased in the following order flavonol < chrysin < car thamin < orange II < carminic acid < shikonin. The decoloration rate increased as the temperature rose. The apparent activation energy of the decoloration reaction seemed to decrease in the order above.
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