Preparation, Control Of Metal Oxide Nanostructures And Tesearch On Catalytic Ozonation

Phenol compounds are crucial chemical raw materials and intermediates. The effluentwith phenol compounds not only threaten health of human, but also bring enormous harmto the environment. Therefore, the efficient treatment for phenol effluent has become theurgent problem to be solved. Catalytic ozonation process is one of the most prospectivewater treatment in environment field, it was applicable to degradation of organics with lowconcentration.Nano-metal oxides with simple preparation and low cost possess the unique nature ofnanomaterials, and perform excellent catalytic as catalysts in ozonation reaction , therefore,they have receive tremendous focus at home and abroad. However, for the same typecatalysts, it is found that the different preparation conditions lead to significant differencesin surface property and catalytic activity. Therefore, it is necessary to investigate thecontact among preparation, the control of surface and catalytic activity of the catalysts.In our study, catalytic ozonation processes were investigated in degradationsimulative phenol effluent as target organic with metal oxide nanomaterials as catalysts.The relationship among the preparation method, the surface property and catalytic activityof catalysts in ozonation reaction were deliberated through controlling the surfacecharacteristic of catalysts. Designing various experiments to study the interaction betweencatalysts and ozone, it was confirmed that the oxidation species except hydroxyl radicalsexsited in reaction system. It was probed that the distinct the mechanism with catalysts,and the transformation of reactants and intermediates in catalytic reaction.Firstly, a series of ZnO, CeO₂ and MnOx nanomaterials were synthetized with differentpreparation methods, such as precipitation method, hydrothermal reaction, and combustionsynthesis. The samples were characterized by TG, X-ray diffraction, transmission electronmicroscopy, the Brunauer-Emmett-Teller surface area, UV-vis and FT-IR. Then products ofeach system were investigated on degradation of phenol in ozonation process, followed byselecting samples with high catalytic activity. The influence of preparation condition onsurface characteristics and catalytic activity were predicated conbination with catalyticactivities.In the system of nano-ZnO, five products were prepared by controlling calcinationtemperature and feeding speeds. The influence of preparation conditions on surfaceproperty and catalytic activity was discussed for nano-ZnO. The best reaction condition forozonation process was determined in presence of the sample, which presented the bestcatalytic activity. The influence on decomposition of ozone, the effect of tert-butyl alcoholon catalytic ozonation of phenol, and the catalysis on degradation of nitrobenzene ofnano-ZnO were evaluated respectively. It was revealed that phenol was not oxidized byhydroxyl radicals in catalytic reaction process with nano-ZnO.In the system of CeO₂, six CeO₂ nanomaterials were prepared by controlling ceriumsource, hydrothermal temperature and time. The reason why the cerium source led to theremarkable difference of catalytic activity was the difference of precursors. Thehydrothermal temperature and time caused significant difference in catalytic property, theAbstract reason focused on that the higher temperature and longer time in high pressure reactionresulted in the lose of the active center. The profound reason was analytical byinvestigating the effect on decomposition of ozone with Ce-E and Ce-F. The possible siteof the active center of catalytic reaction was determined, and the catalytic ozonationreaction process with Ce-E was described finally. The transformation of phenol andintermediates was defined with high-pressure liquid chromatography analysis. It wasdirectly proved that Ce-E presented high catalytic activity by calculating rate constant ofreaction.In the system of MnOx, the influence on surface property and catalytic activity withdifferent preparation methods and surfactants was inspected. The sample which obtained inpreparation process without surfactants performed the best catalytic activity according toresults. The decomposition of ozone with samples were deliberated, it was concluded thatthe catalytic ozonation reaction with MnOx-SDS and MnOx-SDBS maybe attributed toozone oxidation directly. Though MnO_x-n and Mn2O3 promoted decomposition of ozone,catalytic activities of them performed significant difference. It was expounded that thereason that MnO_x-n and Mn2O3 performed different catalytic activities on ozonationdegradation of phenol, the catalytic ozonation reaction process with MnO_x-n, the possiblesite of the active center, and the transformation of phenol and intermediate products.