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

Abstract

Zn0-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 Zn0, 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 Zn0-activated PS. The chemical oxygen demand and the total organic carbon decreased by approximately 85% and 58%, respectively, in the solution containing 98mg/L MO at the initial pH 5 and 25°C within 3h. The optimum dosages of PS and Zn0 were 71mg/L and 1.3g/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 SO4− 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.