Manganese Oxide Octahedral Molecular Sieve(OMS-2) Degradate Organic Dyes In The Presence Of Peroxymonosulfate

Manganese oxide octahedral molecular sieve?OMS-2?has a mild surface acidity and good redox properties due to the existence of Mn²⁺,Mn³⁺ and Mn⁴⁺ in the lattice,which has become a new research hotspot for researchers.New advanced oxidation technology based on sulfate radicals is a green,economical,simple and widely used water treatment technology,but there are still some shortcomings such as high cost,low catalyst efficiency and easy loss of metal components.Therefore,it is important to explore OMS-2 as a new catalyst for the activation of persulfate degradation wastewater.In this paper,OMS-2 and magnetic Fe₃O₄@OMS-2 catalysts were prepared by heating reflux method and solvent-free method.X-ray diffraction,Fourier transform infrared spectroscopy,scanning electron microscopy,N2 adsorption/desorption isotherms,X Ray photoelectron spectroscopy?XPS?and electron paramagnetic resonance?ESR?were used to characterize the structure of the catalyst.The OMS-2/PMS,OMS-2/PMS/Vis and Fe₃O₄/OMS-2/PMS catalytic system were prepared to studied the treatment efficiency of acid orange7?AO7?,degradation of intermediates,kinetics,catalyst stability and reaction mechanism,respectively,by using persulfate?PMS?as oxidant under Visible light?Vis?.The main conclusions are as follows.?1?In the OMS-2/PMS catalytic system,OMS-2 and PMS are indispensable to the degradation of dye wastewater.The AO7 and other dyes can be completely removed within 15 min by this system.Increasing the dye concentration,the amount of catalyst and the concentration of PMS can promote the degradation of the dye,but the removal efficiency decreaseds with the increase of the pH value of the solution.OMS-2 still showedgood catalytic performance after five recycling.Free radical inhibitory experiments show that the sulfate radicals produced by the catalyst activated PMS are the main active species of the system.The XPS and ESR results indicate that the catalytic mechanism may involve the reduction of Mn???ions and the oxidation of Mn???ions.The degradation pathway of AO7 by OMS-2/PMS system was also proposed by the analysis of intermediates based on the electrospray ionization mass spectrometry technology.?2?Compared with OMS-2/PMS system,OMS-2/PMS/Vis system has higher degradation rate of AO7 and intermediates.It was indicated by ESR and XPS that the catalytic process of OMS-2/PMS/Vis system involves the redox of Mn???/Mn???and Mn???/Mn?II?;while,valence state conversion only between Mn???and Mn???was occurred in OMS-2/PMS system.?3?The core-shell magnetic nanocatalysts produced though loading OMS-2 on Fe₃O₄ by solvent-free method have a high surface area of 251m2/g and high paramagneticity.It exhibited high catalytic activity of activated PMS to degrade organic dyes.The retained activity was still about 85% after it had been used for more than 10 times.And it can be easily separated using external magnetic field.So,it is an efficient catalytic material with high stability and recovery rate.