Research On The Catalytic Ozonation Treating Coal Gasification Wastewater And The Preparation Of Cow Dung Based Activated Carbon Supported Nano-Fe₃O₄

Coal gasification industry is the foundation and support of China's new coal chemical industry and plays an irreplaceable role in the field of clean and energy efficient utilization.However,conventional wastewater treatment technology cannot effectively treat a large amount of waste water generated in the process of coal gasification.And the effluent of secondary biochemical treatment process still contains a large number of toxic and refractory materials.Along with the more strict discharge standard,the problem of the treatment of such wastewater seriously restricts the rapid development of coal chemical industry.Ozone oxidation process has been widely concerned in the field of wastewater treatment because of its high efficiency,stability and no secondary pollution.In order to improve the mineralization ability of ozonation technology for organic pollutants in wastewater,catalytic ozonation technology has gradually become a research hotspot in this environmental field.For the sake of highly removal rate of pollutants in the catalytic ozonation system,on the one hand,catalysts with high catalytic activity,low cost and strong stability can be developed.On the other hand,microbubble ozone technology can be used to enhance ozonation.In this paper,cow dung based activated carbon?CDAC?was prepared by phosphoric acid activation method,and Nano-Fe₃O₄@CDAC catalyst was successfully prepared by coprecipitation method.The characterization of carrier and catalysts were analyzed.The result from XRD,SEM and BET show that cow dung carbon surface morphology changed from smooth into coarse porous,nano-sized Fe₃O₄,generated by the coprecipitation method,is uniform distributing in the surface and the gap of the CDAC.CDAC and Nano-Fe₃O₄@CDAC catalysts have high ratio surface area?were 55.08 m²/g and 20.56m²/g,respectively?.The heterogeneous catalytic micro-ozone oxidation system was built to treat biologically pretreated coal gasification wastewater.The optimal operating conditions of the single micro-ozone oxidation system were determined by examining the removal efficiency of COD and UV₂₅₄.And the effect of catalyst dosage on the COD removal of wastewater was also tested.The result showed that the microbubble ozone system and the catalytic microbubble ozone system had well degradation performance for the organic compounds in the wastewater?COD removal of wastewater were9.8%and 16.8%higher than that of ordinary ozone oxidation,respectively?.The practicability of Nano-Fe₃O₄@CDAC was investigated,and the COD removal efficiency of the catalyst was still above 70%after 5 consecutive catalytic experiments.The presence of hydroxyl radical·OH was directly detected by EPR detection,the generation of·OH in different reaction systems was compared,and the promotion effect of microbubble ozone and Nano-Fe₃O₄@CDAC on ozone treatment was verified.Through GC-MS analysis and three-dimensional fluorescence spectra,it was clear that the main refractory substances of the wastewater in this catalytic process were basically completely removed,and the biodegradability of the wastewater was significantly improved.