Study On Fe-Mn/γ-Al₂O₃ Catalytic Ozone Oxidation Technology Of Landfill Leachate

Landfill leachate is one kind of highly polluted wastewater with high concentration.The treatment of landfill leachate remains a thorny problem due to its complex composition and high NH₄⁺-N concentration.Therefore,it is an urgent problem to find out an efficient method.As an advanced technology,heterogeneous catalytic ozone oxidation technology has been widely used in the treatment of refractory wastewater.Therefore,in this paper,a supported catalyst withγ-Al₂O₃ as the carrier and iron and manganese as the active components is prepared,and a catalytic ozone oxidation reactor is designed to treat the organic matter in the landfill leachate.The best process of catalyst preparation and the best operating parameters of the reactor are investigated.At the pretreatment stage,the best process of coagulation and air stripping are as following:the best process of coagulation is 16+16 g/L of PFS+Al₂（SO₄）₃,the coagulation is performed under the condition of p H=8（original p H）,and the COD removal rate can be 69%.;the best condition of air stripping is determined to be 25℃,4-6 hours of treatment at p H=11,and the NH₄⁺-N removal rate can be 70%.The pretreatment of landfill leachate can improve the efficiency of the catalytic oxidation treatment process.Taking COD removal rate as the evaluation index,this paper firstly investigates the best process Fe-Mn/γ-Al₂O₃ catalyst preparation.The research result shows thatγ-Al₂O₃ is immersed for 6 hours in the precursors of iron and manganese 1 mol/L each at a ratio of 1:1,then burning at 350°C for 3 hours.The characterization results of the catalyst show iron and manganese are evenly loaded on the surface of the carrier,the ratio of iron oxides is Fe₂O₃:Fe O=2.47:1,and the ratio of manganese oxides is Mn O₂:Mn₂O₃=2.22:1.Still adapting the COD removal rate as the evaluation index,further investigation focuses on the optimal operation conditions of the reactor.The results show that the optimal conditions are as follows:catalyst dosage 12.5 g/L,oxygen flow rate 0.8 L/min,initial p H=11,HRT=4 h,COD removal rate can reach 83.7%;furthermore,tandem operation can increase 30%utilization rate of ozone.Through the three-dimensional fluorescence spectroscopy and GC-MS analysis of the water quality,demonstrate the main ingredients of landfill leachate are refractory organics such as humic acid and fulvic acid.During the early stage of the catalytic oxidation,·OH mainly degrades refractory organics into small-molecule organics.In the later stage,the fluorescence intensity of the organic matter is greatly reduced,and the humus in the effluent is basically mineralized.