Degradation of methyl orange by sodium persulfate activated with zero-valent zinc

Abstract Zn 0 -activated persulfate (PS) is a novel advanced oxidation technology for the degradation of organic pollutants in aqueous solution. The effects of the initial solution pH, the dosages of PS and Zn 0 , and the temperature were investigated through a series of batch experiments using methyl orange (MO), an azo dye, as a model organic pollutant. The results demonstrated that MO could be effectively degraded by Zn 0 -activated PS. The chemical oxygen demand and the total organic carbon decreased by approximately 85% and 58%, respectively, in the solution containing 98 mg/L MO at the initial pH 5 and 25 °C within 3 h. The optimum dosages of PS and Zn 0 were 71 mg/L and 1.3 g/L, respectively. The highest removal of MO was realized at an initial pH 5. Tertiary butyl alcohol, an OH-specific radical scavenger, and l -histidine, a universal radical scavenger, corroborated that both OH and SO 4 − contributed to MO degradation. Three stages were observed during the degradation of MO at 15 and 25 °C, a rapid removal of MO in the initial stage of the reaction, followed by a very slow one and then a relatively quick degradation process.