Comparison Of Cerium,Iron,and Manganese Oxides Loaded Various ZSM-5 Zeolites In Catalytic Ozonation Of Nitrobenzene From Water:Efficiencies And Mechanisms

The efficiencies and mechanisms of the parent and the metal(Ce,Fe,or Mn)oxides loaded various ZSM-5 zeolites in catalytic ozonation processes(COPs)were comparatively investigated for the treatment of nitrobenzene from water.The total organic carbon(TOC)removals in COPs upon parent NaZSM-5(38),HZSM-5(38),and NaZSM-5(100)increased by 6.7%,and 19.8%,respectively,relative to single ozonation(39.2%)under multiple uses.The loading of Ce,Fe,or Mn oxides significantly promoted the catalytic activity of the three series of ZSM-5 zeolites.The Ce/NaZSM-5(38)showed the highest TOC removal(86.3%)among ZSM-5 zeolites.The three series of ZSM-5 zeolites exhibited differentiatedmechanisms for removing nitrobenzene from water.The TOC removals of nitrobenzene solution in COPs upon NaZSM-5(38)series of zeolites were mainly via ·OH mediated oxidation due to weak adsorption.HZSM-5(38)and NaZSM-5(100)series of zeolites have powerful adsorption to nitrobenzene.The adsorption and direct ozonation jointly contributed the TOC removal in their first use.The ·OH mediated oxidation gradually dominated the TOC removal as the adsorption tends to be saturated under multiple uses.The surface Si-O bonds and Si-OH-Al structures are active sites of ZSM-5 zeolites.The high surface dispersion of loaded metal oxides further enriches their active sites.This study illustrates a new potential application of ZSM-5 zeolites as catalysts in COPs for increased efficiency when treating refractory wastewaters.