Manganese oxide octahedral molecular sieve (OMS-2) as an effective catalyst for degradation of organic dyes in aqueous solutions in the presence of peroxymonosulfate

Abstract

Cryptomelane type manganese oxide OMS-2 was prepared and tested in heterogeneous activation of peroxymonosulfate (PMS) for Acid Orange 7 (AO7) degradation in aqueous solutions. X-ray diffraction, scanning electron microscopy, N2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron spin resonance spectroscopy (ESR) were used to characterize the properties of the material. The effect of several parameters on its catalytic activity was also investigated. It was found that the catalyst was very active for AO7 and other organic dyes degradation, and presented a long-term stability during multiple runs. Results from XPS and ESR suggested that the highly catalytic efficiency possible involved the activation of PMS to sulfate radicals meditated by the redox pair of Mn(IV)/Mn(III) in OMS-2. Based on intermediate detections, the degradation pathway of AO7 in the OMS-2/PMS system was proposed.