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Pulsed high-voltage electrical discharge was used in treating azo dye (Acid Orange ii, AO7) wastewater.

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Pulsed high‐voltage discharge, one of the advanced oxidation processes, was used for the treatment of Sunset Yellow wastewater. The effects of discharge type, initial pH, conductivity, and bubbling gas type on the formation of H2O2 were investigated in the mechanism experiments using deionized water. The concentration of H2O2 formed in hybrid series discharge mode was higher than that formed in hybrid gas‐liquid discharge and liquid discharge modes. Moreover, a pH of 1 and low conductivity were beneficial to the formation of H2O2. Bubbling O2 could obviously enhance the generation of H2O2. Afterwards, the effects of discharge type, initial pH, and bubbling gas type on the formation of H2O2 were also studied in the degradation experiments of Sunset Yellow. The experiment results were consistent with the mechanism experiments. Fenton reaction happened by the introduction of Fe2+ into the discharge process, which obviously enhanced the degradation of Sunset Yellow. Besides, the effects of initial pH and Fe2+ concentration on the Sunset Yellow degradation followed the second‐order kinetics. Moreover, the degradation efficiency of Sunset Yellow with copper mesh as an electrode was much higher than that with the needle electrode. This article proposed a feasible approach to deal with Sunset Yellow wastewater.

BACKGROUND A new Fe/AC heterogeneous Fenton‐like catalyst was prepared using a dipping–sintering method. The prepared catalyst was characterized by X‐ray diffraction and scanning electron microscopy. The decolorization of Sunset Yellow was conducted in a self‐designed pulsed high‐voltage discharge system by the catalysis of the prepared heterogeneous catalyst. Effects of preparation conditions of catalyst (carrier material, sintering temperature and dipping time) and operating conditions (catalyst dosage, pH and treatment method) on decolorization efficiency were investigated. RESULTS Spherical activated carbon (AC) was selected as the carrier material and the optimal dipping time and sintering temperature were 8 h and 350 °C, respectively. The efficiency of decolorization of Sunset Yellow was above 90% after 30 min of a pulsed high‐voltage discharge process with 5 g heterogeneous catalyst and at pH 2.00. The utilization of copper mesh not only enhanced the decolorization of Sunset Yellow but also facilitated the reusability of the prepared heterogeneous catalyst. The efficiency of decolorization of Sunset Yellow with prepared Fe/AC heterogeneous Fenton‐like catalyst (5 g) was even a little higher than that with homogeneous catalyst (1.635 mmol L−1 Fe2+). The decolorization efficiency remained above 90% after ten recycles of the catalyst, indicating that the prepared heterogeneous catalyst has good stability and reusability. In addition, a possible catalytic mechanism for the decolorization reaction in a pulsed high‐voltage discharge system with prepared Fe/AC heterogeneous Fenton‐like catalyst was proposed by determination of H2O2 and ·OH concentrations in deionized water. CONCLUSIONS The prepared Fe/AC heterogeneous Fenton‐like catalyst efficiently degrades Sunset Yellow wastewater in a pulsed high‐voltage discharge system. © 2016 Society of Chemical Industry