Decolorization of azo dye Orange II by ferrate(VI)–hypochlorite liquid mixture, potassium ferrate(VI) and potassium permanganate

Abstract

Ferrate(VI)–hypochlorite liquid mixture was prepared using hypochlorite, an industrial by-product, via wet oxidation method. Its oxidizing ability was investigated by decolorizing azo dye Orange II in batch experiments, and compared with potassium ferrate(VI) and potassium permanganate. Effects of the oxidant concentration, dye concentration, initial pH of dye solutions and UV 254 nm irradiation were examined. The color removal by potassium permanganate, potassium ferrate(VI) and the ferrate(VI)–hypochlorite liquid mixture at 30 min reached 17.7%, 62.0% and 95.2%, respectively. The ferrate(VI)–hypochlorite liquid mixture maintained a high decolorization efficiency over a wide pH range from 3.0 to 11.0, indicating that the initial solution pH had little impact on its oxidizing power. However, the decolorization efficiency by potassium permanganate was proved to be highly pH dependent and the lowest efficiency was observed at neutral pH. UV 254 nm irradiation did not enhance the decolorization efficiencies significantly for both the ferrate(VI)–hypochlorite liquid mixture and potassium permanganate over a wide pH range.