Visible light enhanced heterogeneous photo-degradation of Orange II by zinc ferrite (ZnFe2O4) catalyst with the assistance of persulfate

Visible (Vis) light (>= 420 nm) response ZnFe2O4 photocatalyst was successfully fabricated via a facile reduction-oxidation method and its catalytic activity was demonstrated by the pronounced Orange II decolorization under Vis/ZnFe2O4/PS (persulfate, S2O82-) process. The reaction kinetics, degradation mechanism, catalyst stability, and mineralization as well as the toxicity, were detailed investigated. On the basis of the effects of radical scavengers, the sulfate radical (SO4 center dot-) is regarded as the predominant reactive oxidants for the Orange II decolorization, while the hydroxyl radical ((OH)-O-center dot) is also involved. A possible pathway is proposed according to the intermediates determined by GC-MS. The ZnFe2O4 catalyst maintained high activity and stability with very low iron and zinc leaching during the repeated experiments. At initial pH 6.0, the total organic carbon (TOC) and chemical oxygen demand (COD) removal efficiencies at 300 min were 50.5% and 78.6%, respectively, using 0.5 g/L. ZnFe2O4 dosage, 1.0 g/L, persulfate, and a 150 W visible light lamp. Toxicity experiments with activated sludge implied that the toxicity of the treated solution increased at the first stage but then declined as the reaction proceeded. (C) 2016 Elsevier B.V. All rights reserved.