Oxidation Degradation of Rhodamine B in Aqueous byUV/S2O8 2−Treatment System

Abstract

The UV photolysis of persulfate (S2O8 2−) is a novel advanced oxidation technologies (AOTs), which leads to the formation of strong oxidizing radicals, sulfate radicals (SO4 •−). The effect of oxidantS2O8 2−concentration, initial dye concentration, initial pH of solution, and various inorganic anions (Cl−,H2PO4 −, andHCO3 −) were investigated using Rhodamine B (RhB), a kind of xanthene dye, as a model pollutant. With the increase of oxidantS2O8 2−, moreSO4 •−produced to attack RhB molecules and result in the increase of RhB degradation. While the improvement was not sustained above a critical value, beyond which degradation rate does not increase. Initial pH of solution had great effect on the RhB degradation rate duringUV/S2O8 2−system.SO4 •−is rather stable in acidic solutions, while increasing system pH results in the transformation ofSO4 •−to•OH. The effects of three inorganic anions (Cl−,H2PO4 −, andHCO3 −) all had some negative effect on the degradation of RhB. Based on the RhB solution changes of the UV-vis absorption intensity during theUV/S2O8 2−treatment, decolorization of RhB accompanied the destruction of aromatic ring structures of RhB molecules.