Preparation Of Zirconium-supported Catalysts And Catalytic Ozonation Of Methyl Orange

Dyeing wastewater has complex composition,high chroma and poor biodegradability,and it accounts for a large proportion of industrial wastewater in China.From the state’s emphasis on environmental protection and the release of a series of documents,it can be seen the discharge of dyeing wastewater can not be ignored.Catalytic ozonation process is an important part of advanced oxidation technology in water treatment,in which catalyst plays an important role.Zirconia is a special transition-metal oxide that possesses bifunctional characteristics of weak and base properties.The p-type semiconductivity shows abundant oxygen vacancies on its surface.Meanwhile,the high ion-exchange capacity and redox activities make it possible to be used in many catalytic processes as the catalyst,the supporter,and the promoter.In addition,the superior chemical stability and mechanical strength are favorable for application in catalysis,such as Fischer-Tropsch synthesis,organic reforming,photocatalysis and other fields.In recent years,mesoporous zirconia has stimulated significant scientific interests due to their higher surface area,unique and outstanding electronic,mechanical,and chemical properties.Commercial ZrO₂was used as a support to prepare MnO_x/ZrO₂catalyst by the incipient wetness impregnation method,and methyl orange was used as the targeted contaminant for exploring the catalytic activity on ozonation of MnO_x/ZrO₂catalyst.In the experiment,the factors of calcination temperature and catalyst loading were studied to determine the optimal catalyst preparation condition.Also,the initial pH of methyl orange solution was investigated during the catalytic ozonation process.The result showed that MnO_x/ZrO₂which prepared under the conditions of 400℃calcination temperature and 15%loading,exhibited the highest catalytic activity,after 60 min reaction.The catalytic activity of MnO_x/ZrO₂ was higher with the decrease of the initial solution pH.After three cycles of the catalyst,it was found that the catalytic activity of the catalyst was decreased,which may be due to the small specific surface area of the commercial ZrO₂,the active component could be detached easily.In order to increase the stability of the catalyst and the number of cycles,zirconium oxychloride was used as the zirconium source and CTMAB was used as the surfactant.The ZrO₂with larger specific surface area was prepared by hydrothermal method,catalysts（Mn/ZrO₂,Co-Mn/ZrO₂,Ce-Mn/ZrO₂,Fe-Mn/ZrO₂etal）were prepared by the incipient wetness impregnation method.The ZrO₂-based catalysts were used to study the decolorization of methyl orange wastewater by catalytic ozonation.The effect of reaction conditions on the decolorization rate of methyl orange was discussed.The physical properties of the catalyst were investigated by SEM,TEM,BET,XRD and XPS analysis.The results showed that the Co-Mn/ZrO₂ catalyst with a specific surface area of 43 m²/g and active components of MnO₂and Co₃O₄rexhibited the best degradation effect on organic matter.At room temperature,the optimal conditions for the decolorization of methyl orange by Co-Mn/ZrO₂catalyst were methyl orange concentration 100 mg/L,solution pH 3 and catalyst dosage 0.6 g/L,and metal ion dissolution rate during catalytic reaction was low,the decolorization rate of methyl orange could still be maintained above 90%after four cycles.The research provides reliable theoretical support for dyeing wastewater treatment.