Preparation And Catalytic Ozonation Of Perovskite Modified SiC Ceramic Membranes

Catalytic ozonation technology is integrated with ceramic membrane filtration technology,which has shown excellent performance in the treatment of high concentration and refractory wastewater,intermediate water reuse and deep purification of drinking water,and has become a hot topic in the research field of membrane separation technology.In this work,high-efficient,environmentally friendly and durable nano-catalysts were prepared,such as La_0.9Ce_0.1Co O₃ perovskite-type,La_0.9Ce_0.1Co O₃@dicelite（DE）supported catalyst and La_0.9Ce_0.1Co O₃@CM catalytic function silicon carbide（Si C）ceramic membrane.The morphology,crystal structure,specific surface area,porosity and elemental valence of catalysts and catalytic membranes were characterized by scanning electron microscope（SEM）,transmission electron microscope（TEM）,X-ray diffraction（XRD）,specific surface area（BET）and X-ray photoelectron spectroscopy（XPS）.Three kinds of catalytic ozonation systems were constructed:heterogeneous catalytic ozonation(La_0.9Ce_0.1Co O₃/O₃),dynamic ceramic membrane catalytic ozonation(La_0.9Ce_0.1Co O₃@DE/CM/O₃)and catalytic ceramic membrane catalytic ozonation(La_0.9Ce_0.1Co O₃@CM/O₃).Adopting Nitrobenzene（NB）as the target pollutants,the catalytic performances of the catalytic system were evaluated by determining the degradation efficiency and TOC removal rate of NB aqueous solution.The influences of catalyst dosage,reaction temperature,initial solution concentration,initial solution p H and filtration liquid flow rate on the catalytic performances of the three catalytic systems were systematically discussed.The possible catalytic degradation mechanism was proposed by the capture agent experiment and electron paramagnetic resonance spectroscopy（EPR）.In addition,the La_0.9Ce_0.1Co O₃@CM/O₃ system was applied to degrade the aqueous solutions of two typical dyes（Methyl orange MO and Methylene blue MB）,and the feasibility of the catalytic system in printing and dyeing wastewater treatment was explored.Specific research contents are as follows:（1）A perovskite-type catalyst La_0.9Ce_0.1Co O₃ was successfully prepared by citrate assisted sol-gel method for the reaction system of heterogeneous catalytic ozonation.The catalyst showed the adhesion structure of particles and sheets,and the grain size was calculated as 12.45 nm by Scherrer’s formula.The optimized reaction conditions were systematically studied by single factor experiment as follows:the concentration of ozone dissolved in water was 8.4 mg/L,the amount of La_0.9Ce_0.1Co O₃ was 0.15 g/L,the initial NB concentration was 0.1 g/L,the initial solution p H was 7,and the reaction temperature was 25℃.After 30 min,NB degradation efficiency and TOC removal rate reached 100%and 92.5%,respectively,indicating that La_0.9Ce_0.1Co O₃ had high catalytic ozonation activity.·OH,O₂^·-and ¹O₂ were the main reactive oxygen species（ROS）in the system,and·OH played a dominant role in catalytic ozonation.La_0.9Ce_0.1Co O₃ showed excellent stability and reusability for NB degradation after 5 cycles.（2）La_0.9Ce_0.1Co O₃ was loaded on the surface of Diatomaceous earth by urea-assisted sol-gel method to prepare a supported catalyst La_0.9Ce_0.1Co O₃@DE.A dynamic layer catalytic system La_0.9Ce_0.1Co O₃@DE/CM/O₃ was innovatively designed by integrating the Si C ceramic membrane support made in the laboratory with La_0.9Ce_0.1Co O₃@DE as catalytic layer.NB was used as the target pollutant to evaluate the catalytic ozonation performance of the system.The detailed optimization conditions are as follows:the concentration of ozone dissolved in water is 8.4 mg/L,the amount of La_0.9Ce_0.1Co O₃@DE is 0.40 g/L,the initial NB concentration is 0.1 g/L,the initial solution p H is 7,the reaction temperature is 25℃,and the filtration flow rate is 200 m L/min.After 30 min,the TOC removal rate of NB for La_0.9Ce_0.1Co O₃@DE is 47.07%higher than that of unmodified DE,indicating that La_0.9Ce_0.1Co O₃@DE has an excellent catalytic activity of ozonation.The free radical trapping experiment and EPR test showed that·OH,O₂^·-and ¹O₂ ROS groups existed simultaneously,and·OH played a dominant role in catalytic ozonation.Catalyst La_0.9Ce_0.1Co O₃@DE showed excellent stability and reusability for NB mineralization after 5 cycles.（3）Using the urea assisted sol-gel method,La_0.9Ce_0.1Co O₃ was loaded on the surface and pores of Si C ceramic membranes to fabricate a catalytic ceramic membrane La_0.9Ce_0.1Co O₃@CM,endowing a catalytic ozonation performance of Si C ceramic membrane.A catalytic degradation system La_0.9Ce_0.1Co O₃@CM/O₃ with ceramic membrane filtration was designed for deep degradation of NB aqueous solution.The reaction conditions of the catalytic system were investigated:the concentration of ozone dissolved in water was 8.4 mg/L,the filling times of La_0.9Ce_0.1Co O₃@CM was 1,the catalyst filling amount was 0.041 g,the initial NB concentration was 0.1 g/L,the initial p H of the solution was 7,the reaction temperature was 25℃,and the liquid filtration flow rate is 200 m L/min.After 30 min,the TOC removal rate of NB catalyzed by La_0.9Ce_0.1Co O₃@CM is 30.1%higher than that of unmodified CM,which suggests that La_0.9Ce_0.1Co O₃@CM has a good catalytic activity of ozonation.Free radical trapping experiments and EPR tests showed that·OH,O₂^·-and ¹O₂ were the main ROS in the catalytic system.After 5 cycles,La_0.9Ce_0.1Co O₃@CM still showed outstanding stability and reusability for NB degradation.In addition,the La_0.9Ce_0.1Co O₃@CM/O₃ system was employed in the treatment of dye aqueous solutions（MO and MB）,the results showed the rapid decolorization and deep mineralization of dye westewater were obtained,which laid a foundation for the potential application of the system in the treatment of printing and dyeing wastewater.