| The treatment of industrial wastewater has always been a focused environmental problem.At present,most treatments in China still adopt traditional facilities and technologies.But with the rapid development of industry,old technologies can no longer satisfy the high standard of water treatment.As an advanced oxidation technology,catalytic ozone oxidation would be widely used in the field of industrial wastewater treatment in the near future due to its good treatment effect,simple operation and no secondary pollution.In this article,Mn-Ce/Al2O3 and Mn-Co/Al2O3 catalysts were prepared and used to deal with four kinds of industrial wastewater through continuous reaction method to explore the catalytic activity of the alumina-based catalysts.The experimental results showed that with 50 mg·L-1ozone dosage,the COD for the food wastewater decreased from 103.8 mg·L-1 to 49.78 mg·L-1 and 107 mg·L-1 to 44.3 mg·L-1 after the treatments of Mn-Ce/Al2O3 and Mn-Co/Al2O3 catalysts,respectively.Accordingly,the value for the printing and dyeing wastewater reduced to 42.26 mg·L-1 and 43.7 mg·L-1,respectively.As for coal chemical and rubber leather wastewater,when the ozone dosage is 200 mg·L-1,the COD decreased from 117 mg·L-1 to 53 mg·L-1 and 49 mg·L-1 using Mn-Ce/Al2O3 catalyst,and 93.6 mg·L-1 to 72.2 mg·L-1 and 64.3 mg·L-1 using Mn-Co/Al2O3 catalyst,respectively.Therefore,the catalytic activity of Mn-Co/Al2O3 catalyst was superior to that of Mn-Ce/Al2O3 catalyst and both were ideal for food,printing and dyeing and coal chemical industry.But the catalytic effect for rubber leather wastewater was not satisfying.So a better catalyst need to be developed to improve the catalytic performance.The XRD spectra indicated that the metallic oxides existed in the catalysts in amorphous structure.From the XPS spectrograms,Mn existed in the form of Mn4+ and Ce existed in the form of Ce3+ and Ce4+ in the Mn-Ce/Al2O3 catalyst.While in the Mn-Co/Al2O3 catalyst,Mn existed in the form of Mn4+,and Co existed in the form of Co2+ and Co3+.Another kind of catalysts based on activated carbon,Mn-Co/AC,was prepared and used to decompose the methylene blue wastewater with static reaction operation method to further optimize the preparation conditions.The Mn-Co/AC catalyst was characterized and the catalytic activity was compared between it and the Mn-Co/Al2O3 catalyst.The results showed that the catalyst prepared by loading 2 wt%:2 wt%Mn-Co active component and calcining at 400? had the best catalytic performance.When adding 30 mg·L-1 ozone to methylene blue wastewater,the COD decreased from 105.88 mg·L-1 to 42.11 mg·L-1 and 103.21 mg·L-1 to 65.28 mg·L-1 using Mn-Co/AC and Mn-Co/Al2O3 catalysts,respectively.For simulated rubber wastewater,when the ozone dosage is 120 mg·L-1,the COD decreased from 98.45 mg·L-1 to 49.12 mg·L-1 and 98.45 mg·L-1 to 77.52 mg·L-1,respectively.The XRD spectra of the Mn-Co/AC catalyst showed that the metallic oxides existed in amorphous structure.And the XPS spectrograms indicated that Mn existed in the form of Mn2+ and Mn3+ and Co existed in the form of Co2+ and Co3+.The catalytic stability,wear resistance and metal dissolution of Mn-Co/AC catalysts were further investigated by continuous reaction operation.The mechanism of catalytic reaction was studied by adding tert-butyl alcohol,a hydroxyl radical inhibitor.The results showed that in the continuous 90-hour reaction operation,the COD of the wastewater was kept between 40 mg·L-1 and 50 mg·L-1 from the initial 100 mg·L-1 and the wear rate of the catalysts was only 8.7 wt%.Nearly no metallic oxides dissolution was observed,while some hydroxyl radical were generated.Hence,the methylene blue was decomposed by Ozone through direct oxidation and indirect oxidation during the catalytic reactions,further improving the catalytic performance. |
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