Reseacrch On New Silicon-resistant Catalyst For Catalytic Ozone Oxidation

The wastewater from coal chemical industry is highly concentrated in COD,toxic for human being,and difficult to biodegradation.If it is discharged directly into the environment without treatment or just simple treatment,it will seriously damage the water environment and threaten human health.In the process of wastewater treatment in chemical coal chemical industry,it was found that the catalysts are easy to be coated by silicate in the wastewater and then deactivated,which then restrict the application of catalytic ozone oxidation（CWOO）in wastewater treatment of the coal chemical industry.In order to solve the problem of the catalyst deactivation aroused by the phenomenon of silicon coating upon catalysts,a new type of silicon-resistant catalyst for CWOO was developed and used as CWOO catalyst to degrade the silicon-containing m-Cresol model wastewater.The main research contents and results of this thesis are as follows:First,a variety of commercial catalyst carriers were evaluated for their silicon adsorption performance,and it was found that the laboratory-made KD-6 microspheric carbon carrier and ZSM-5 molecular sieve carrier showed excellent capacity of resistance to silicon.Based on the above two carriers,a series of Fe-loaded microspheric carbon catalysts and molecular sieve catalysts were prepared.The capacity of resistance to silicon was further evaluated.Taking the KD-Fe-3 catalysts that possess the best capacity of resistance to silicon in the series microspheric carbon catalysts as the research object,its surface structure and properties were characterized by various methods.CWOO experiment was carried out with a mixture solution containing m-Cresol and silica was used as model substrate,and its reaction conditions were optimized by response surface method（RSM）.The optimal reaction conditions were as follow:the catalyst dosage 1.5 g/L,the reaction time 24.97 min,the initial ozone concentration 70 mg/L,initial aqueous pH 4.56,silicon concentration 86.81 mg/L,m-Cresol concentration 77.80 mg/L.Under these conditions,the CWOO reaction was carried out,m-Cresol conversion was 100%,TOC removal was about4 times that of the ozonation without catalyst.The catalyst was evaluated for continuous 240h CWOO reaction,and the catalyst can still maintain high catalytic activity and stability.Further research indicated that the catalytic mechanism of KD-Fe-3 catalyst is the radical-type mechanism（·OH,O₂·^-and ¹O₂）.With ZSM-5 molecular sieve as the carrier,a series of anti-silicon catalysts were prepared by the equal volume impregnation method.The effects of the types of active component,the type of precursor salt solution,the calcination temperature,and the loading of active component on the anti-silicon performance of the catalysts and on the degradation effect of silicon-containing m-Cresol wastewater by CWOO of the catalysts.The optimal preparation conditions:the active component is Fe,the precursor salt is Fe（NO₃）₃,the calcination temperature is 500℃,and the loading is3 wt%.At this time,the conversion of m-cresol is 100%,the TOC removal is 36.35%,and the anti-silicon effect is excellent.