Activation of Periodate for Efficient Degradation of Organic Dyes with Manganese Oxide Supported on Activated Alumina Beads.

Manganese oxide loaded on activated alumina beads (MnOx/AABs) was prepared by one-pot hydrothermal method and applied to activate periodate (PI) towards the degradation of Rhodamine B (RhB) and other organic dyes. The catalyst was first characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and N2 sorption. Subsequently, the effects of catalyst dosage, oxidant dosage, initial pH as well as co-existing inorganic anion and humic acid on the performance of the MnOx/AABs/PI system were studied. Under optimum conditions (catalyst dosage = 15 beads, PI dosage = 0.2 g/L), the removal efficiency of 50 mg/L RhB reached 99.4%, with a total organic carbon removal efficiency of 51.0%. The removal efficiencies of several other organic dyes were in the range of 70%-95.1%. The leached amount of Mn was measured to be 0.027 mg/L. Mechanism studies revealed that 1O2, IO3⋅ and O2⋅− were identified to be responsible in this reaction system, and 1O2 played a decisive role. In addition, IO4− was converted to IO3− without other toxic products during the degradation process. Reusability test in both the batch and continuous modes showed that the catalyst could be efficiency regenerated by calcination. Combining the results of liquid chromatography-mass spectrometry (LC–MS) and density functional theory calculations, the possible degradation pathway of RhB was proposed. Finally, toxicity evaluation of the degradation products of RhB was performed by theoretical calculations as well as experimental tests with Vigna radiata. [ABSTRACT FROM AUTHOR]