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

Abstract

Abstract Visible (Vis) light (⩾420 nm) response ZnFe 2 O 4 photocatalyst was successfully fabricated via a facile reduction-oxidation method and its catalytic activity was demonstrated by the pronounced Orange II decolorization under Vis/ZnFe 2 O 4 /PS (persulfate, S 2 O 8 2− ) 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 (SO 4 − ) is regarded as the predominant reactive oxidants for the Orange II decolorization, while the hydroxyl radical ( OH) is also involved. A possible pathway is proposed according to the intermediates determined by GC-MS. The ZnFe 2 O 4 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 ZnFe 2 O 4 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.