The use of ultrasound to enhance the decolorization of the C.I. Acid Orange 7 by zero-valent iron

The effect of pH, iron loading and initial dye concentration on the decolorization of C.I. Acid Orange 7 by zero-valent iron combined with ultrasound radiation was investigated. It was shown that the reduction of C.I. Acid Orange 7 was enhanced by ultrasound and the decolorization appeared to be a first order reaction. With the pH range of 3-7, iron loading range of 0.5-2.0 g L−1 and initial dye concentration of 50-250 mg L−1, the decolorization efficiency decreased with the increasing pH or initial dye concentration, but increased with the increase of iron loading. Accordingly, the first order rate constant k1 decreased by 0.026 min−1 when pH dropped by one unit. It increased linearly with the increasing iron loading, but decreased nonlinearly with the increase of the initial dye concentration.