MnO₂-RGO/Al₂O₃ Catalyst-micro Air Bubble System Catalytic Ozonation For Advanced Treatment Of Wastewater From Coal Chemical Industry

Coal chemical wastewater is a typical non-biodegradable wastewater.After biochemical treatment,the effluent still cannot meet relevant emission standards.Effluent color is high,and the content of residual refractory biodegradable organics?such as quinoline,etc.?is high,which depends on further processing in the following sections.In the waste water treatment process,the heterogeneous ozone catalytic oxidation technology has gradually attracted the attention of scholars due to the easy separation of catalyst and water,high removal efficiency,and no derivative pollution.The development of highly efficient,reusable,and highly engineered catalysts is a key part of the heterogeneous ozone catalytic oxidation technology.In this study,the-catalysts were prepared by hydrothermal synthesis,hydrothermal loading and ultrasonic loading.The quinoline was used as the removal target to study the effectiveness of the catalysts.The results showed that the catalysts prepared by hydrothermal synthesis had the highest efficiency and activity.The doping-MnO₂RGO/Al₂O₃ catalysts were prepared by doping method.By studying the degradation of TOC and quinoline,the optimized parameters of the catalysts were optimized: calcined at 450 °C for 4 h.The particle size is 4 mm,the mass fraction of MnO₂ is 9%,and the ratio of GM?mass ratio of RGO to MnO₂?is 10:1.The appearance of the catalyst was evaluated by XRD?X-Ray Diffraction?,FTIR?Fourier Infrared?,TEM?Transmission Electron Microscopy?,BET?Special Surface and Pore Structure Analyzer?,and XPS?Surface Element Analyzer?.Mechanism analysis,in which the peak position of the XRD image is compared with the standard card,shows that MnO₂ is the standard ?-MnO₂,MnO₂ in the TEM image is a rod-shaped structure with a diameter of about 50 nm,and it is supported on the reticulated,corrugated,wrinkled form of graphene.The two are dispersed on the Al₂O₃ support.The dispersion of MnO₂ supported on RGO is higher than that on Al₂O₃.The FTIR curve shows that the MnO₂ and GO are not simply contacted but have Mn-OC bonds.The process of hydrothermal synthesis is accompanied by The disappearance of oxygencontaining groups and the formation of new bonds Mn-O-C;BET results show that the catalyst has a large specific surface area,reaching 172 m2/ g,from the hysteresis loop and curve form that the catalyst exists mesoporous structure,pore size analysis to verify the main The results of the mesoporous structure and XPS elemental analysis show that the appropriate amount of GO increases the surface Mn content and improves the catalytic efficiency.The TG thermogravimetry analysis shows that the temperature is 450°C.The thermal weight loss of the prepared catalyst has been relatively stable,there is no further change in the catalyst components,and the catalyst used after re-drying is of stable quality,and the quality does not change significantly with increasing temperature.In terms of engineering parameters,the compressive strength of the catalyst reached 25.2 N.After repeated 10 cycles,the removal efficiency of quinoline remained above 91%.The catalyst damage analysis of each catalyst with different manganese content was performed after each experiment.It was found that there was no obvious relationship between the number of damaged catalysts and manganese content,and there was almost no mass loss of the catalyst under general water flow wear.This study examined the role of ·OH and ·O₂^-in the catalytic system of ozone oxidation.Experiments have shown that ·OH plays an important role in this system.The oxidation of ·O₂^-functions slightly but not ·OH,through the micro-bubbles The effect of the characterization and aeration forms on the quinoline removal rate illustrates that the microbubble system increases the removal rate of quinoline by approximately 20%.A continuous flow reaction system was established in the experiment to achieve continuous inflow and outflow of coal chemical wastewater.After 10 hours of operation,the COD removal rate was over 51%,the TOC removal rate reached 62%,and the UV254 degradation rate was close to 70%.It shows that the system has good resistance to external organic load.When discharged,the water quality meets the first-grade standard of Integrated Wastewater Discharge Standard.This system has the practical value of engineering application and has reference significance for ozone oxidation technology.