Study on the Photochemical Decolorization of Orange II by Natural Goethite

The decolorization of Orange II in goethite/UV system was investigated. It was discovered that the optimum condition is: pH=3, [α-FeOOH]=0.5 g/L, [Orange II]=10 mg/L. Furthermore, the absorption of Orange II on goethite, and the effect of pH values, goethite dosage and carboxylate on the decolorization were investigated. The decolorization efficiency was 90% after 6h irradiation when the concentration of pyruvic acid was 1.0mmol/L, α-FeOOH concentration was 0.3 g/L, and Orange II concentration was 10 mg/L at pH 3.0. Besides, total organic carbon (TOC) and chemical oxygen demand (COD) were determined, and a possible reaction mechanism was prompted as well.