Visible light-assisted heterogeneous Fenton with ZnFe 2 O 4 for the degradation of Orange II in water

In this study, a visible (Vis) light response photocatalyst was synthesized via a simple reduction–oxidation method. The structure, morphology and optical properties of the catalyst were well characterized. The absorption capability of ZnFe 2 O 4 in visible-light region was demonstrated by the high rate of Orange II decolorization under Vis/ZnFe 2 O 4 /H 2 O 2 process. Guided by studies to explore the effects of radical scavengers and to quantify the yield of hydroxyl radical ( OH) production, OH on the surface of the catalyst was found to be the dominating reactive species for the Orange II removal. Moreover, ZnFe 2 O 4 maintained high activity, crystallinity and extremely low iron and zinc leaching during repeated experiments. The intermediate products were identified by GC–MS and a possible pathway is accordingly proposed to elucidate the mechanism of Orange II degradation by OH. In addition, high extent of mineralization was obtained as the chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies were 86.6% and 60.4%, respectively, within 60 min reaction. The toxicity tests with activated sludge indicated that the toxicity of the solution increased during the first 30 min but then decreased significantly as the oxidation proceeded.