Study On The Degradation Performance Of MnO₂ And BiOBr Catalysts For Methylene Blue Dye

With the development of industry,the environmental problems caused by industrial organic wastewater are increasingly prominent.At present,there are mainly physical,chemical and biological methods for the removal of organic wastewater,and conventional treatment methods often have the disadvantages of low degradation efficiency or short service life,etc.However,semiconductor photocatalyst has become a research hotspot due to its advantages of green energy saving,wide degradation range and thorough degradation of pollutants at room temperature.MnO₂ is considered as an excellent photocatalyst because of its low price,diverse structure and unique catalytic performance.As a kind of nano-layered semiconductor,BiOBr has adjustable band gap width,and its photocatalytic performance has also been widely studied.However,nanocatalyst is difficult to recover in use,which is easy to cause secondary pollution.At the same time,BiOBr is difficult to be applied in practice due to its poor catalytic performance in visible light.Based on this,this paper uses diatomite as the carrier to load MnO₂ to solve the recycling problem of nanometer MnO₂.Meanwhile,studies were carried out on the composite of BiOBr with CeO₂ and graphene and MnO₂/Diatomite to improve its visible light degradation efficiency and catalytic performance.With the method of decomposition of potassium permanganate from hydrothermal synthesis of MnO₂?K-Birnessite type?,to study the different calcining temperature,calcining time and Ce⁴⁺ion doping effect the performance of the catalyst,using scanning electron microscopy?SEM?and X-ray diffraction?XRD?and catalytic degradation experiment,the morphology structure and catalytic degradation properties of the catalysts were characterized and the results show that degradation efficiency increased from 62%to 85%after 180 minutes of calcination at 300?;When Ce⁴⁺ion doping is carried out,MnO₂ structure changes from k-birnessite type to?-crystal type,which can improve its degradation efficiency.When Ce⁴⁺ion doping content reaches 0.04,the degradation efficiency reaches 99%.Diatomite was used to load MnO₂ to improve its recycling capacity,and the optimal mass ratio between diatomite and potassium permanganate was searched for synthetic samples.Moreover,the prepared diatomite loaded MnO₂ was recovered,the recovery rate was calculated,and the five photocatalytic degradation cycle performance of the samples was measured.The results showed that the optimal mass ratio of MnO₂ to diatomite was 1.6:1,the recovery efficiency was 86%,the degradation efficiency decreased from 91%to 84%after 5cycles,and the photocatalytic degradation cycle performance was stable.Finally,the effects of BiOBr with visible light catalysis and its combination with CeO₂ or graphene and MnO₂/diatomite on the photodegradation performance of methylene blue dye were studied.Taking Bi?NO₃?₃�5H₂O and KBr as raw materials,the particle morphology of hydrothermal synthesis of BiOBr in pure water was two-dimensional nano-sheet with a diameter of less than 10 microns.When dilute nitric acid was added into the solution,the particle morphology remained unchanged,but the crystallinity of BiOBr was improved,and the visible light degradation efficiency of methylene blue was 43%.When ethylene glycol is added to the solution,as the solution viscosity and boiling point increase,the particle morphology of BiOBr is agglomerated into regular spheres by finer two-dimensional nano-sheet,which can improve the adsorption effect of methylene blue dye.And the temperature of hydrothermal reaction also has a great influence on the photocatalytic performance,when temperature is 140?,visible light catalytic degradation rate was 64%.The composite of CeO₂/BiOBr can boost the response ability of visible light and make the visible light degradation efficiency of the catalyst reach 75%.The combination of graphene and BiOBr increased the visible light catalytic efficiency of the catalyst to 69%.The synthesis of CeO₂/BiOBr/MnO₂/diatomite improves the visible light catalytic efficiency of the catalyst.When the mass ratio of CeO₂/BiOBr to MnO₂/diatomite is 6:1,the visible light catalytic performance is improved to 80%.