Preparation And Characterization Of Mn_xZn_1-xFe₂O₄/?-MnO₂/?-Bi₂O₃ Composite Magnetic Catalyst

The global environmental problems are becoming increasingly significant with the acceleration of the industrialization process,especially the water environmental problems caused by organic wastewater are highly concerned.There are some problems in conventional organic wastewater treatment methods,such as long processing cycles and low removal rates.Catalytic wet peroxide oxidation?CWPO?and semiconductor photocatalytic technology have become the current research hotspot because they can overcome the shortcomings of conventional methods and accelerate the degradation of organic wastewater.Because of the abundant resources,good catalytic performance and environmental friendly,manganese dioxide?MnO₂?is considered to be an excellent heterogeneous catalyst.Bismuth oxide?Bi₂O₃?has become one of the hotspots of semiconductor photocatalyst for its simple preparation method,non-toxic and small bandwidth.However,MnO₂ and Bi₂O₃ are difficult to recover after the end of the reaction,which is easy to cause secondary pollution.In addition,the photocatalytic activity of Bi₂O₃ is low due to the rapid recombination of electron-hole pairs and poor response to light in the visible region.So,this paper attempted to prepare the composite magnetic catalyst Mn_xZn_1-xFe₂O₄/?-MnO₂ and Mn_xZn_1-xFe₂O₄/?-MnO₂/?-Bi₂O₃,not only can realize the recovery of catalyst,but also improve the catalytic activity of the catalyst.?-MnO₂/Mn_xZn_1-xFe₂O₄ was synthesized via chemical co-precipitation method.The effects of mass ratio,molar ratio and H₂O₂ dose on the catalytic activity were studied.The structure and performance of Mn_xZn_1-xFe₂O₄/?-MnO₂ were characterized by XRD,FTIR,SEM and SQUID.The catalytic activity of the composite was studied by using Rhodamine B?RhB?as a simulated pollutant,and its stability was also studied.The results show that the spherical ?-MnO₂ and magnetic substrates Mn_x Zn_1-x Fe₂O₄ are successfully combined together,and the composite magnetic catalyst has good catalytic and magnetic properties.When the mass ratio of Mn_xZn_1-xFe₂O₄ and ?-MnO₂ is 20:100,molar ratio of MnSO₄·H₂O and KMnO₄ is 1.1:1,the catalytic activity of Mn_xZn_1-xFe₂O₄/?-MnO₂ is the best.In the presence of 2m L of H₂O₂?30%?,the degradation ratio of Rh B at a concentration of 10mg/L?100m L?in 0.005 g composite magnetic catalyst?93.9%?is higher than that in pure ?-MnO₂?33.7%?within 1h.Under the magnetic field,the recovery ratio of the composite magnetic catalyst is 89%,and the degradation rate of Rh B is 76% after five cycles.Mn_xZn_1-x Fe₂O₄/?-MnO₂/?-Bi₂O₃ was synthesized via impregnation sintering method,and the effects of mass ratio,photocatalyst dosage and the initial concentration of RhB on the catalytic activity were studied.The structure and performance of Mn_xZn_1-xFe₂O₄/?-MnO₂/?-Bi₂O₃ were characterized by XRD,FTIR,SEM,EDS,SQUID and UV-vis DRS.The photocatalytic activity of the composite was studied by using RhB.The results show that spherical and flaky ?-Bi₂O₃,spherical ?-MnO₂ and massive Mn_xZn_1-x Fe₂O₄ are successfully combined together to Mn_xZn_1-xFe₂O₄/?-MnO₂/?-Bi₂O₃.The band gap of the composite?2.34eV?is lower than that of pure ?-Bi₂O₃?2.48eV?or Mn_xZn_1-xFe₂O₄/?-Bi₂O₃?2.43eV?,and it has good catalytic performance and magnetic properties.When the mass ratio of ?-MnO₂ and ?-Bi₂O₃ is 10:100,the degradation ratio of RhB in 0.1g composite magnetic photocatalyst?98.9%?is higher than that in ?-Bi₂O₃?48%?or Mn_xZn_1-xFe₂O₄/?-Bi₂O₃?65%?within 1.75 h.Under the magnetic field,the recovery ratio of the composite magnetic photocatalyst is 87%,and the degradation ratio of RhB is 95.7% after five cycles.