Study On The Preparation Of Heterogeneous Manganese-based Fenton Catalyst And Its Degradation Of Cyclin Wastewater

Nowadays,the extensive use of antibiotics worldwide poses an increasing threat to the aquatic environment,most antibiotics and their metabolites are persistent and stable refractory organic compounds.Conventional physical or biological treatment technology has been unable to effectively remove antibiotics,especially the removal effect of low-concentration antibiotics is not ideal.Advanced oxidation technologies（AOPs）have a powerful effect on the treatment of high organic content and non-biodegradable wastewater,thus becoming a highly potential process.Among many AOPs techniques,the Fenton reaction has been used for many years and has undergone a series of improvements.Currently,peroxymonosulfate（PMS）is used as a strong oxidant to degrade pollutants after activation using heterogeneous Fenton-like catalysts,which has attracted extensive attention due to its low cost,high efficiency,and mild conditions.Among many transition metal catalysts,Mn-based catalysts are particularly effective in activating PMS to degrade tetracycline.For example,due to the presence of a large amount of Mn（Ⅲ）and Mn（Ⅳ）in Mn O₂,when PMS is added to contact the active centers on its surface,each active center transfer electrons through the redox reaction between Mn（Ⅲ）and Mn（Ⅳ）.At the same time,PMS is activated by Mn O₂ to generate SO₄^·-to degrade tetracycline.In addition,common manganese ferrite Mn Fe₂O₄ contains abundant Mn（Ⅱ）and Mn（Ⅳ）,which can activate PMS to generate SO₄^·-.The synergistic effect between Mn and Fe will also greatly promote the decomposition of tetracycline.Therefore,this paper takes manganese-based catalysts as the research object and improves the performance of removing tetracycline from wastewater by constructing heterogeneous Fenton-like catalysts.The specific research contents are as follows:1.The MnCO₃ precursor with high crystallinity is synthesized by room temperature co-precipitation method,and it is calcined at high temperature in air atmosphere to obtain pure phaseε-Mn O₂.Theε-Mn O₂/PVDF polymer film was prepared by the immersion-precipitation phase inversion method.Whenε-Mn O₂/PVDF was used as the activator of PMS,it exhibited good catalytic degradation performance for 20 ppm tetracycline（TC）.And it can still maintain its original catalytic effect after 10 cycles of experiments.Morphology analysis results show thatε-Mn O₂ is relatively uniformly dispersed in PVDF,forming a dense surface layer.Due to the addition ofε-MnO₂ nanoparticles,large pores and pores are formed,which are beneficial to the adsorption and degradation of pollutant molecules.Besides,the influence of PMS concentration in the system,p H value and external factors such as anion species contained in the solution were further studied.2.Five ratios of MoS₂/MnFe₂O₄ magnetic particles were synthesized by in situ growth to activate PMS to degrade 20 ppm tetracycline（TC）.The results show that when the ratio of Mo S₂ to Mn Fe₂O₄ is 2:1,its catalytic performance is better than that of other ratios of the composites.At the same time,the strong magnetic properties of Mo S₂/Mn Fe₂O₄ make it easy to separate and recover from water for subsequently using.The degradation rate of tetracycline（TC）was still maintained at 80%after repeated four cycles.After a series of characterization analysis,the possible reaction mechanism of Mo S₂/Mn Fe₂O₄ activated PMS for TC degradation was discussed.3.In order to explore the reasons for the difference in the activity of manganese dioxide with different phase structures in the Fenton-like reaction,four complexes ofα-,β-,γ-,δ-Mn O₂ and Mn Fe₂O₄ were synthesized for degradation of 20 ppm TC.It is found thatβ-Mn O₂/Mn Fe₂O₄ has the best degradation effect on TC,and still has strong magnetic properties,which solves the problem that many catalysts are difficult to recycle.The extremely low leaching amount of Mn and Fe ions indicates that the catalyst is environmentally friendly and not easy to cause pollution.Finally,a series of characterization methods were used to clarify their structural differences and reaction mechanism.